First galaxies: observations Lecture 3
Renske Smit Newton-Kavli fellow - University of Cambridge The spectral energy distribution
Adapted from Galliano et al. 2018 The spectral energy distribution
Adapted from Galliano et al. 2018 Overview
Lecture 1: Detection methods and the galaxy census Lecture 2: Dust and stellar mass Lecture 3: Optical and sub-mm spectroscopy
• Spectroscopic confirmations
• Lyman alpha and the IGM neutral hydrogen fraction
• [CII] emission: origin and detections
• Potential for kinematics
• High ionisation lines Spectroscopic confirmation of galaxies in the EoR The Astrophysical Journal, 819:129 (11pp), 2016 March 10 Oesch et al.
Table 3 Assumed LFs for z ∼ 10–11 Number Density Estimates
-5 Reference f * 10 M* α Nexp (Mpc−3)(mag)(<−22.1) Bouwens et al. (2015b) 1.65 −20.97 −2.38 0.06 Finkelstein et al. (2015) 0.96 −20.55 −2.90 0.002 Mashian et al. (2015) 0.25 −21.20 −2.20 0.03 Mason et al. (2015) 0.30 −21.05 −2.61 0.01 Trac et al. (2015) 5.00 −20.18 −2.22 0.002
Note. The parameters f*, M*, and α represent the three parameters of the Schechter UV LF taken from the different papers. when assuming a more realistic case where the emission line Oesch et al. 2016 flux is distributed over a combination of lines (e.g., Figure 7. Redshift and UV luminosities of known high-redshift galaxies from fi blank field surveys. Dark filled squares correspond to spectroscopically Hβ+[O III]), we can con dently invalidate such a solution. confirmed sources, while small gray dots are photometric redshifts (Bouwens The lower left panel in Figure 4 compares the measured grism et al. 2015b). GN-z11 clearly stands out as one of the most luminous currently spectrum with that expected for the best-fit lower redshift known galaxies at all redshifts z>6 and is by far the most distantmeasured solution we had previously identified (Oesch et al. 2014).A galaxy with spectroscopy (black squares; see Oesch et al. 2015b, for a full list of references). Wider area surveys with future near-infrared telescopes (such as strong line emitter SED is clearly inconsistent with the data. WFIRST) will be required to determine how common such luminous sources Apart from the emission lines, which we do not detect, this really are at z>10. model also predicts weak continuum flux across the whole wavelength range. At <1.47 μm, this is higher than the the observed spectrum has a break of 1->ffshort long 0.68 fl ( nn) observed mean, while at >1.47 μm the expected ux is too low at 2σ, thus indicating again that we can marginally rule out a compared to the observations. Overall the likelihood of a z∼2 4000 Å break based on the spectrum alone without even extreme emission line SED based on our grism data is less than including the photometric constraints. 10−6 and can be ruled out. Note that in very similar grism observations for a source triply imaged by a CLASH foreground cluster, emission line 4. DISCUSSION contamination could also be excluded (Pirzkal et al. 2015). We 4.1. Physical Properties of GN-z11 thus have no indication currently that any of the recent z∼9–11 galaxy candidates identified with HST is a lower Despite being the most distant known galaxy, GN-z11 is redshift strong emission line contaminant (but see, e.g., relatively bright and reliably detected in both IRAC 3.6 and Brammer et al. 2013, for a possible z∼12 candidate). 4.5 μm bands from the S-CANDELS survey (Ashby et al. 2015). This provides a sampling of its rest-frame UV SED and even partially covers the rest-frame optical wave- 3.3. Excluding a Lower-redshift Dusty or Quiescent Galaxy lengths in the IRAC 4.5 μm band (see Figure 6). The photometry of GN-z11 is consistent with a SED of Another potential source of contamination for very high logMM ~ 9 using standard templates (Bruzual & Char- redshift galaxy samples are dusty z∼2–3 sources with strong lot 2003, see appendix). The UV continuum is relatively blue 4000 Å or Balmer breaks (Hayes et al. 2012; Oesch et al. with a UV spectral slope β=−2.5±0.2 as derived from a 2012). However, the fact that the IRAC data for GN-z11 show powerlaw fit to the H160, K, and [3.6] fluxes only, indicating that it has a very blue continuum longward of 1.6 μm, together very little dust extinction (see also Wilkins et al. 2016). with the very red color in the WFC3/IR photometry, already Together with the absence of a strong Balmer break, this is rules out such a solution (see SED plot in Figure 4). consistent with a young stellar age of this galaxy. The best fit Nevertheless, we additionally explore what constraints the age is only 40 Myr (<110 Myr at 1σ). GN-z11 thus formed its grism spectrum alone can set on such a solution. stars relatively rapidly. The inferred star formation rate is 24 ± The expected flux for such a red galaxy increases gradually −1 10 Me yr . All the inferred physical parameters for GN-z11 across the wavelength range covered by the G141 grism, unlike are summarized in Table 2. Overall, our results show that what we observe in the data (lower right in Figure 4). galaxy build-up was well underway at 400 Myr after the fi ∼ Compared to our best- t solution (see next section) we measure Big Bang. a Δχ2=15 when comparing the data with the expected grism flux. Apart from the extremely large discrepancy with the IRAC photometry, we can thus exclude this solution at 98.9% 4.2. The Number Density of Very Bright z > 10 Galaxies confidence based on the spectrum alone. The spectrum of GN-z11 indicates that its continuum break Similar conclusions can be drawn from the break strength lieswithin the H160 filter (which covers ∼1.4–1.7 μm; see Figure 6). alone (see e.g., Spinrad et al. 1998). Assuming that the The rest-frame UV continuum flux of this galaxy is therefore observed break at 1.47 μm corresponds to 4000 Å at z 2.7, a = ∼0.4 mag brighter than inferred from the H160 magnitude. The galaxy with a maximally old SED (single burst at z=15) estimated absolute magnitude is M =−22.1±0.2, which is fl short long UV would show a ux ratio of (1- 7 Spectroscopic confirmation of galaxies in the EoR The Astrophysical Journal, 819:129 (11pp), 2016 March 10 Oesch et al. Table 3 Assumed LFs for z ∼ 10–11 Number Density Estimates -5 Reference f * 10 M* α Nexp (Mpc−3)(mag)(<−22.1) Bouwens et al. (2015b) 1.65 −20.97 −2.38 0.06 Finkelstein et al. (2015) 0.96 −20.55 −2.90 0.002 Mashian et al. (2015) 0.25 −21.20 −2.20 0.03 Mason et al. (2015) 0.30 −21.05 −2.61 0.01 Trac et al. (2015) 5.00 −20.18 −2.22 0.002 Note. The parameters f*, M*, and α represent the three parameters of the Schechter UV LF taken from the different papers. when assuming a more realistic case where the emission line Oesch et al. 2016 flux is distributed over a combination of lines (e.g., Figure 7. Redshift and UV luminosities of known high-redshift galaxies from fi blank field surveys. Dark filled squares correspond to spectroscopically Hβ+[O III]), we can con dently invalidate such a solution. confirmed sources, while small gray dots are photometric redshifts (Bouwens The lower left panel in Figure 4 compares the measured grism et al. 2015b). GN-z11 clearly stands out as one of the most luminous currently spectrum with that expected for the best-fit lower redshift known galaxies at all redshifts z>6 and is by far the most distantmeasured solution we had previously identified (Oesch et al. 2014).A galaxy with spectroscopy (black squares; see Oesch et al. 2015b, for a full list of references). Wider area surveys with future near-infrared telescopes (such as strong line emitter SED is clearly inconsistent with the data. WFIRST) will be required to determine how common such luminous sources Apart from the emission lines, which we do not detect, this really are at z>10. model also predicts weak continuum flux across the whole wavelength range. At <1.47 μm, this is higher than the the observed spectrum has a break of 1->ffshort long 0.68 fl ( nn) observed mean, while at >1.47 μm the expected ux is too low at 2σ, thus indicating again that we can marginally rule out a compared to the observations. Overall the likelihood of a z∼2 4000 Å break based on the spectrum alone without even extreme emission line SED based on our grism data is less than including the photometric constraints. 10−6 and can be ruled out. Note that in very similar grism observations for a source triply imaged by a CLASH foreground cluster, emission line 4. DISCUSSION contamination could also be excluded (Pirzkal et al. 2015). We 4.1. Physical Properties of GN-z11 thus have no indication currently that any of the recent z∼9–11 galaxy candidates identified with HST is a lower Despite being the most distant known galaxy, GN-z11 is redshift strong emission line contaminant (but see, e.g., relatively bright and reliably detected in both IRAC 3.6 and Brammer et al. 2013, for a possible z∼12 candidate). 4.5 μm bands from the S-CANDELS survey (Ashby et al. 2015). This provides a sampling of its rest-frame UV SED and even partially covers the rest-frame optical wave- 3.3. Excluding a Lower-redshift Dusty or Quiescent Galaxy lengths in the IRAC 4.5 μm band (see Figure 6). The photometry of GN-z11 is consistent with a SED of Another potential source of contamination for very high logMM ~ 9 using standard templates (Bruzual & Char- redshift galaxy samples are dusty z∼2–3 sources with strong lot 2003, see appendix). The UV continuum is relatively blue 4000 Å or Balmer breaks (Hayes et al. 2012; Oesch et al. with a UV spectral slope β=−2.5±0.2 as derived from a 2012). However, the fact that the IRAC data for GN-z11 show powerlaw fit to the H160, K, and [3.6] fluxes only, indicating that it has a very blue continuum longward of 1.6 μm, together very little dust extinction (see also Wilkins et al. 2016). with the very red color in the WFC3/IR photometry, already Together with the absence of a strong Balmer break, this is rules out such a solution (see SED plot in Figure 4). consistent with a young stellar age of this galaxy. The best fit Nevertheless, we additionally explore what constraints the age is only 40 Myr (<110 Myr at 1σ). GN-z11 thus formed its grism spectrum alone can set on such a solution. stars relatively rapidly. The inferred star formation rate is 24 ± The expected flux for such a red galaxy increases gradually −1 10 Me yr . All the inferred physical parameters for GN-z11 across the wavelength range covered by the G141 grism, unlike are summarized in Table 2. Overall, our results show that what we observe in the data (lower right in Figure 4). galaxy build-up was well underway at 400 Myr after the fi ∼ Compared to our best- t solution (see next section) we measure Big Bang. a Δχ2=15 when comparing the data with the expected grism flux. Apart from the extremely large discrepancy with the IRAC photometry, we can thus exclude this solution at 98.9% 4.2. The Number Density of Very Bright z > 10 Galaxies confidence based on the spectrum alone. The spectrum of GN-z11 indicates that its continuum break Similar conclusions can be drawn from the break strength lieswithin the H160 filter (which covers ∼1.4–1.7 μm; see Figure 6). alone (see e.g., Spinrad et al. 1998). Assuming that the The rest-frame UV continuum flux of this galaxy is therefore observed break at 1.47 μm corresponds to 4000 Å at z 2.7, a = ∼0.4 mag brighter than inferred from the H160 magnitude. The galaxy with a maximally old SED (single burst at z=15) estimated absolute magnitude is M =−22.1±0.2, which is fl short long UV would show a ux ratio of (1- 7 Lyman-⍺ z=3-6 The Astrophysical Journal Letters,728:L2(5pp),2011February10 Stark, Ellis, & Ouchi • Lyα at 1216Å is the intrinsically the brightest emission line in the spectrum of SF galaxies • Due to resonant scattering the Lyα fraction goes down. Lyα is mainly observed in low-mass, low metallicity systems Stark et al. 2011 Figure 2. Left: the differential rest-frame Lyα EW distribution, p(WLyα)(computedinbinsspanning∆WLyα,0 30 Å) for star-forming galaxies at z 6intwo = ≃ luminosity ranges ( 21.75 5. THE EXPECTED VISIBILITY OF Lyα EMISSION IN z 7LBGs ≃ Our new results, taken together with those in Paper I, now suggest that 54% of moderately faint ( 20.25 Table 3 Lyα Luminosity Function a 2 obs obs tot z φ∗ LLy∗ α αχr n ρLyα ρLyα 4 3 42 1 4 3 39 1 3 39 1 3 (10− Mpc− )(10erg s− )(10− Mpc− )(10erg s− Mpc− )(10erg s− Mpc− ) (1) (2) (3) (4) (5) (6) (7) (8) +3.0 +0.6 +0.9 +0.5 +1.0 6.6 8.5 2.2 4.4 0.6 1.5(fix) 1.60 4.1 0.8 1.9 0.4 6.6 0.8 − − − − − − Notes. (1) Redshift; (2)–(4) best-fit Schechter parameters for φ and L ,respectively,α is fixed to 1.5; (5) reduced χ 2 of the fitting; (6)–(7) ∗ Ly∗ α − number densities and Lyα luminosity densities calculated with the best-fit Schechter parameters down to the observed limit of Lyα luminosity, i.e., 1 log LLyα 42.4ergs− ; (8) inferred total Lyα luminosity densities integrated down to LLyα 0withthebest-fitSchechterparameters. a = Lyman-⍺ z=3-6 = LLy∗ α is the apparent value, i.e., observed Lyα luminosity with no correction for IGM absorption. recently reported for z 2–6 LAEs (Cassata et al. 2010;see also Rauch et al. 2008)aswellas= z 7dropouts(e.g.,Ouchi et al. 2009b;Oeschetal.2010;McLureetal.∼ LAE2010 luminosity). The best-fit +2.6 4 3 parameters for α 1.7areφ∗ 6.9 1.9 10− Mpc− and +0.9 = −42 1 = − function:× no LLy∗ α 4.9 0.7 10 erg s− .Notethatourdatapointatthe = − × 1 bright end (log L(Lyα) 43.5ergs− )appearstoexceedtheevolution from best-fit Schechter function= in Figure 6,althoughthedatapoint is consistent with the best-fit Schechter functionz=3.1 within to z=5.7 the error bar that extends down to 0. This excess data- unlike point is solelystrong made by one exceptional LAE that is an extended giant LAE, Himiko, reported in Ouchi et al. (2009a). evolution of 3.4. Evolution of Lyα Luminosity FunctionLBGs Figure 7 compares our Lyα LF of LAEs at z 6.6withthose at z 3.1and5.7. Note that these low-z LFs are= derived from large= LAE samples of wide-field SXDS (Ouchi et al. 2008) with the same procedures (including cosmic variance errors) and similar data sets taken with the same instrument. In this sense, there are little systematics among different redshift results Ouchi et al. 2008; 2010 caused by the sample selection and measurement technique. Figure 7. Evolution of Lyα LFs up to z 6.6. Red filled circles are the best While the LFs do not change within error bars from z 3.1 estimates of z 6.6LAEsfromtheentireSXDSsampleandredsolidlineisthe= to 5.7(Ouchietal.2008), the LF decreases from z = 5.7 best-fit Schechter= function of z 6.6LAEs.Bluefilledcirclesandthesolidline = are data points and the best-fit Schechter= function, respectively, of z 5.7LAEs to 6.6beyondsizesoferrors,i.e.,uncertaintiesofstatistics = and cosmic variance. To quantify this decrease, we present given by Ouchi et al. (2008). Note that the error bars of z 6.6and5.7data points (red and blue filled circles) represent uncertainties= from statistics and in Figure 8 error ellipses of Schechter parameters of LFs at cosmic variance. The cyan solid line is the best-fit Schechter function of z z 6.6, together with those at z 5.7fromOuchietal. 3.1LAEs(Ouchietal.2008). The LF decreases from z 5.7to6.6significantly,= (2008= ). Figure 8 shows that error contours= of z 6.6and5.7 while no significant evolution can be found between=z 3.1and5.7. For = 2 differ at the >90% significance level. Even if we= consider the comparison, we plot LF estimates from each of the five 0.2deg subfields with the same open symbols as found in Figure 6.Theseopensymbolsillustrate∼ maximum effect of contamination (Section 3.1), there exists a that with the data of a single 0.2deg2 field alone (e.g., open circles down to ∼ significant evolution of the Lyα LF. Because a contamination log LLyα 42.6), which is a typical survey size of previous studies, it is difficult correction pushes down our z 6.6LAELFtowardlownumber to distinguish≃ whether or not z 6.6LFsshowevolution(decrease)withrespect = to z 5.7. Dashed and dotted= lines represent the best-fit Schechter functions density in Figure 7,aninclusionofcontaminationcorrection = to our z 6.6LFwithaφ∗ and L∗ fixed to that of z 5.7, respectively. even strengthens the evolutionary tendency. The EW0 limit of = = our z 6.6 LAE sample is 14 Å, which is different from and = ! smaller than that of the z 5.7 LAE sample (EW0 27 Å; constrained EW0 values of our LAEs (see Section 6.1.1 for = ! Ouchi et al. 2008)by∆EW0 10 Å. Ouchi et al. (2008) more details), it is very likely that the bias introduced by the ≃ have investigated a possible false evolution given by a choice different EW0 limits (∆EW0 10 Å) is smaller than that found ≃ of EW0 limit for LAE samples at different redshifts. They in Ouchi et al. (2008), " 10% corresponding to "0.04 dex use LAE samples at z 3–6 whose EW0 limits differ by in φ .Thissmallbiasof 0.04 dex does not affect to the = ∗ " 30 Å (EW0 ! 30–60 Å), and fit a number–EW0 distribution conclusion of LF decrease in Figure 8. Moreover, the conclusion of the samples with a Gaussian function to obtain inferred of LF decrease is probably, again, even strengthened, because Schechter parameters for all z 3–6 LAE samples with the corrections for the incompleteness of the EW0 limits raise φ of = ∗ same EW0 limit of EW0 0. Ouchi et al. (2008)findthatthe the z 5.7sample(EW0 27 Å) more than that of our z 6.6 = = ! = inferred φ∗ is different from the original φ∗ by only " 10%, sample (EW0 ! 14 Å) in the case of the same number–EW0 and claim that the choice of EW0 limits provides negligible distribution at z 5.7and6.6. We plot error contours obtained impact on the results of Lyα LF evolution. This is true if the by Kashikawa et= al. (2006)inFigure8 for comparison. Because difference of the EW0 limit is much smaller than the best-fit the measurements of Kashikawa et al. (2006)donotinclude Gaussian sigma of the number–EW0 distribution (!130 Å for cosmic variance errors, their contours are relatively small. z 3–6; Ouchi et al. 2008). Although we cannot carry out Although the errors of our measurements are not small, the= similar investigation for our z 6.6sampleduetopoorly Figure 8 implies that a decrease in L would be the = ∗ Lyman-⍺ z>6 The Astrophysical Journal,744:179(7pp),2012January10 Schenker et al. amorecomprehensivetreatmentofLyα radiative transfer through outflows, result in an increased value for XH i in both The Astrophysical Journal,744:179(7pp),2012January10 cases. Schenker et al. 55 Å < EW < 85 Å. This slope is equal to dp(EW)/dEW 4. DISCUSSION = 0.0030 for the lower luminosity sample ( 20.25 Consistent results from LBG follow-up and LAE narrowband sources Konno et al. 2014 Figure 9. Evolution of Lyα LF at z 5.7–7.3. The red filled circles are the best = estimates of our z 7.3Lyα LF from the data of entire fields. The red open Figure 10. Error contours of Schechter parameters, LLy∗ α and φ∗.Thered circles and squares= denote our z 7.3Lyα LFs derived with the data of two contours represent our Lyα LF at z 7.3, while the blue contours denote the independent fields of SXDS and= COSMOS, respectively. The red curve is the one at z 6.6 obtained by Ouchi et= al. (2010). The inner and outer contours best-fit Schechter function for the best estimate of our z 7.3Lyα LF. The cyan indicate the= 68% and 90% confidence levels, respectively. The red and blue and blue curves are the best-fit Schechter functions of= the Lyα LFs at z 5.7 crosses show the best-fit Schechter parameters for the Lyα LFs at z 7.3and and 6.6 obtained by Ouchi et al. (2008) and Ouchi et al. (2010), respectively.= 6.6, respectively. = (A color version of this figure is available in the online journal.) (A color version of this figure is available in the online journal.) LF is consistent with those from the Subaru and VLT studies contours of the Schechter parameters of our z 7.3Lyα LF, whose results are supported by spectroscopic observations (Iye together with those of z 6.6LF(Ouchietal.= 2010). Our et al. 2006;Otaetal.2008, 2010;Shibuyaetal.2012;Clement´ measurements indicate that= the Schechter parameters of z 7.3 et al. 2012), and that our Lyα LF agrees with the results of the LF are different from those of z 6.6Lyα LF, and that= the recent deep spectroscopic follow-up observations for the LAE Lyα LF decreases from z 6.6to7=.3atthe>90% confidence candidates from the 4 m telescope data (Clement´ et al. 2012; level. Because our z 7=.3Lyα LF is derived with the same Faisst et al. 2014;Jiangetal.2013). procedures as the z = 6.6Lyα LF (Ouchi et al. 2010), one expects no systematic= errors raised by the analysis technique 4.2. Decrease in Lyα LF from z 6.6to7.3 for the comparison of the z 6.6and7.3 results. From this = aspect, it is reliable that the Ly=α LF declines from z 6.6to In this section, we examine whether the Lyα LF evolves from 7.3significantly.Here,wealsodiscussthepossibilitiesofthe= z 6.6to7.3. As described in Section 2.3,wereachanLyα LF decrease mimicked by our sample biases. In Section 3.1, = 42 1 limiting luminosity of 2.4 10 erg s− which is comparable we assume that there is no contamination in our z 7.3LAE to those of previous Subaru× z 3.1–6.6studies(Shimasaku = = sample. If some contamination sources exist, the z 7.3Lyα et al. 2006;Kashikawaetal.2006, 2011;Ouchietal.2008, LF corrected for contamination should fall below the= present 2010;Huetal.2010). Moreover, the size of the survey area, estimate of the z 7.3Lyα LF. In this case, our conclusion 0.5deg2,iscomparabletothoseintheseSubarustudies.Our = ≃ regarding the significant LF decrease is further strengthened. ultra-deep observations in the large areas allow us to perform In Section 2.3,wedefinetheselectioncriterionoftherest- afaircomparisonoftheLyα LFs at different redshifts. We frame Lyα EW of EW0 ! 0Å forour z 7.3LAEs.This compare our Lyα LF at z 7.3withthoseatz 5.7and6.6 = criterion of the EW0 limit is slightly different from that of the in Figure 9,andsummarizethebest-fitSchechterparametersat= = LAEs for the z 6.6Lyα LF estimates. However, the EW0 z 5.7, 6.6, and 7.3inTable4.Forthez 5.7and6.6data, = limit for the z 6.6LAEsisEW0 ! 14 Å (Ouchi et al. 2010) we= use the Lyα LF measurements of Ouchi et= al. (2010)derived = which is larger than our EW0 limit of z 7.3LAEs.Because from the largest LAE samples, to date, at these redshifts, and the = our EW0 limit gives more z 7.3LAEstooursamplethanthat Lyα LF measurements include all of the major Subaru survey of z 6.6LAEs,theconclusionoftheLy= α LF decrease from data (Shimasaku et al. 2006;Kashikawaetal.2006, 2011)and = z 6.6to7.3isunchangedbytheEW0 limit. the cosmic variance uncertainties in their errors. Nevertheless, = the difference in the best-estimate Lyα LFs is negligibly small 4.3. Accelerated Evolution of Lyα LF at z 7 between these studies. In Figure 9,wefindasignificantdecrease ! of the Lyα LFs from z 6.6to7.3largelybeyondtheerror Figure 9 implies that the decrease in the Lyα LF from z 6.6 bars. In our survey, we expect= to find 65 z 7.3LAEsinthe to 7.3islargerthanthatfromz 5.7to6.6, i.e., there= is case of no Lyα LF evolution from z 6.6to7= .3, but identify an accelerated evolution of the Ly=α LF at z 6.6–7.3. To only 7 z 7.3LAEsfromourobservationsthatareaboutan= evaluate this evolution quantitatively, we calculate= the Lyα order of magnitude= smaller than the expected LAEs. luminosity densities, ρLyα,downtothecommonluminosity 1 Toquantifythisevolution,weevaluatetheerrordistributionof limit of log LLyα 42.4ergs− reached by the observations for Schechter parameters. Because we fix the Schechter parameter LAEs at z 5.7,= 6.6, and 7.3. Similarly, we estimate the total = Lyα,tot of α to 1.5, we examine the error distribution of L∗ and Lyα luminosity densities, ρ ,whichareintegrateddown − Lyα φ with the fixed value of α 1.5. Figure 10 shows error to LLyα 0withthebest-fitSchechterfunctions.Figure11 ∗ = − = 9 Neutral Hydrogen fraction of the IGM The Astrophysical Journal Letters, 802:L19 (5pp), 2015 April 1 Robertson et al. provides a good description of their connection (dashed line). For reference, the likelihood samples shown in Figure 4 indicate the corresponding redshift of instantaneous reioniza- tion zreion via color coding. Given that the SFR density is supplied by galaxies that are Rapid change of luminous in their rest-frame UV, we can also connect the observed τ to the abundance of star-forming galaxies at z 10. the IGM neutral This quantity holds great interest for future studies with JWST, Hydrogen as the potential discovery and verification of distant galaxies beyond z > 10 has provided a prime motivation for the fraction between observatory. The 5σ sensitivity of JWST at 2 μm in a t = 104 s 7 exposure is mAB » 29.5. At z ~ 10, this sensitivity corre- z=6 and z=7-8 sponds to a UV absolute magnitude of MUV »-18. Extra- polating the SFR density to z > 10 and using the shape of the -2 LF at z ⩾ 9, we estimate that N ~ 0.5 arcmin galaxies at z > 10 will be present at apparent magnitudes of mAB < 29.5 at λ = 2 μm. Deep observations with JWST over ~10 arcmin2 may therefore find 5 candidates at z > 10 (see also Behroozi & Silk 2015). Returning to Figure 1, we can see the impact of the reduced value of τ by comparing the Planck and WMAP curves beyond z 10. Robertston et al. 2015 Figure 3. Measures of the neutrality 1 - QHII of the intergalactic medium as a function of redshift. Shown are the observational constraints compiled by Robertson et al. (2013), updated to include recent IGM neutrality estimates 4. DISCUSSION from the observed fraction of Lyα emitting galaxies (Pentericci et al. 2014; Schenker et al. 2014), constraints from the Lyα of GRB host galaxies The lower value of the optical depth τ of Thomson scattering (Chornock et al. 2013), and inferences from dark pixels in Lyα forest reported by the Planck Collaboration et al. (2015) strengthens measurements (McGreer et al. 2015). The evolving IGM neutral fraction the likelihood that early star-forming galaxies dominated the computed by the model is also shown (red region is the 68% credibility reionization process, as our model can simultaneously match interval; white line is the ML model). While these data are not used to constrain the observed SFR history Figure 1 over 6< 4 The Astrophysical Journal, 823:143 (17pp), 2016 June 1 Roberts-Borsani et al. Is this the case for all z>7 LBGs? Detection of new, extreme Spitzer [OIII] line emitters at z>7 The Astrophysical Journal, 823:143 (17pp), 2016 June 1 Roberts-Borsani et al. profiles of the foreground sources are assumed to match that seen in the high-spatial resolution HST images after PSF- matching to the ground-based observations. The total flux in each source is then varied to obtain a good match to the light in the ground-based images. Light from the foreground sources is subsequently subtracted from the images before doing photo- metry on the sources of interest. Flux measurements for individual sources are then performed in 1 2-diameter circular apertures due to the objects being inherently unresolved in the ground-based observations. These flux measurements are then corrected to total, based on the model flux profiles computed for individual sources based on the observed PSFs. The procedure we employ here to derive fluxes is very similar to that employed in Skelton et al. (2014). (See also Galametz et al. 2013 and Guo et al. 2013, who have adopted a similar procedure for their ground-based photometry.) 2.2. Spitzer/IRAC Data Set and Photometry The detailed information we have on z ∼ 6 to 9 galaxy Figure 1. Spitzer/IRAC [3.6]−[4.5] color vs. photometric redshiftRoberts-Borsani plot for et al. 2016 fi candidates over the CANDELS fields from HST is nicely young (∼5 Myr) stellar populations with very strong nebular emission lines Figure 4. Left: best- t SED models (blue line) to the observed HST + Spitzer/IRAC + ground-based photometry (red points and error bars) for the four especially fi (EW = 1500 Å) and a flat continuum. Also assumed are fixed flux ratios bright (H160,AB < 25.5) z 7 galaxies selected using our IRAC red selection criteria ([3.6]−[4.5] > 0.5). Also included in the gure is the redshift estimate for the complemented in the mid-IR by the Spitzer Extended Deep Hα fi between emission lines from Table 1 of Anders & Fritze-v. Alvensleben (2003) best- t model SED provided by EAZY. Right: redshift likelihood distributions P(z) for the same 4 candidate z 7 galaxies, as derived by EAZY. The impact of the Survey (SEDS, PI: Fazio) program (Ashby et al. 2013), which Spitzer/IRAC photometry on the redshift likelihood distributions should be close. for 0.2 Ze metallicity, while assuming case B recombination for the Hα/Hβ ranges in depth from 12 hr to >100 hr per pointing, though flux ratio. The [3.6]–[4.5] color of galaxies is expected to become quite red at 12 hr is the typical exposure time. The SEDS program provides z 7 due to the impact of the [O III] line on the 4.5 μm band and no 7 us with flux information at 3.6 and 4.5 μm, which can be useful comparably bright nebular line in the 3.6 μm. for probing z ∼ 6 to 9 galaxies in the rest-frame optical, fl quantifying the ux in various nebular emission lines, and The significant change in the [3.6]−[4.5] color of galaxies estimating the redshift. from z ∼ 6–7 to z 7 suggests that this might be a promising Over the GN and GS fields, we make use of Spitzer/IRAC way of segregating sources by redshift and in particular to reductions, which include essentially all the Spitzer/IRAC identify galaxies at z 7. Such information would be observations obtained to the present (Labbé et al. 2015; but see fi also Ashby et al. 2015), with 50–200 hr of observations per especially useful for search elds like CANDELS-EGS, which pixel in both bands (and typically ∼100 hr). lack deep observations in Y-band at ∼1.1 μm to estimate the Our procedure for performing photometry on the IRAC data redshifts directly from the position of the Lyman break. Smit is essentially identical to that used on the ground-based et al. (2015) showed that selecting sources with blue [3.6] observations, except that we utilize 2″-diameter circular −[4.5] colors can effectively single-out sources at z ∼ 6.6–6.9 apertures for measuring fluxes. These fluxes are then corrected over all CANDELS fields, even in the absence of Y-band to total based on the model profile of the individual sources + coverage. the PSF. Depending on the size of the source, these corrections Here we attempt to exploit this strong dependence of the range from ∼2.2× to 2.4×. [3.6]−[4.5] color on redshift to identify some of the brightest The median 5σ depths of these Spitzer/IRAC observations z 7 galaxies over the CANDELS fields. In performing this for a ∼26 mag source is 25.5 mag in the 3.6 μm band and 25.3 selection, we start with the source catalogs derived by Bouwens mag in the 4.5 μm band. et al. (2015) and Skelton et al. (2014) over a ∼900 arcmin2 region from the five CANDELS fields. In general, we rely on 3. SAMPLE SELECTION the source catalogs from Bouwens et al. (2015) where they exist (covering a 750 arcmin2 area or 83% of CANDELS).9 3.1. [3.6]–[4.5] IRAC Color versus Redshift ∼ and HST Detections Otherwise we rely on the Skelton et al. (2014) catalogs and photometry. Many recent studies (e.g., Schaerer & de Barros 2009; Shim We then apply color criterion to identify a base sample of et al. 2011; Labbé et al. 2013; Stark et al. 2013; de Barros Lyman-break galaxies at z ∼ 6.3–9.0. In particular, over the et al. 2014; Smit et al. 2014) have presented convincing CANDELS-UDS, COSMOS, and EGS fields, we use a evidence to support the presence of strong nebular line fi contamination in photometric lters, particularly for the IJ->2.2 JH - < 0.5 Spitzer/IRAC [3.6] and [4.5] bands. The observed [3.6] ()()814 125 125 160 -> - + −[4.5] IRAC color of galaxy candidates appears to be strongly (())()IJ814 12522.21 JH 125 160 impacted by the presence of these lines at different redshifts, in fi particular those of Hα and [O III]. Figure 1 provides an criterion. Over the CANDELS-GN and GS elds, we require illustration of the expected dependence of the Spitzer/IRAC that sources satisfy one of the two color criteria defined by [3.6]–[ 4.5] color as a function of redshift, assuming an [O III] +Hβ EW (rest-frame) of 2250 Å, which is at the high end of 9 ∼ Bouwens et al. (2015) only considered those regions in CANDELS where what has been estimated for galaxies at z ∼ 7 (Labbé et al. deep optical and near-IR observations are available from the CANDELS 2013; Smit et al. 2014, 2015). observations. 3 472 D. P. Stark et al. seen in the most extreme C III]-emitting galaxies at lower redshift lines in reionization-era galaxies, there are currently only a hand- (e.g. Erb et al. 2010;Christensenetal.2012; Stark et al. 2014). ful of $vLyα measurements at z>6 (Stark et al. 2015a; Willott Since the continuum is undetected in the spectrum, we calculate the et al. 2015). The wavelength centroids of the [C III], C III]doublet rest-frame equivalent widths using continuum flux derived from the in EGS-zs8-1 reveal a systemic redshift of 7.723. The peak of the broad-band SED. The measurements indicate a total [C III], C III] emergent Lyα emission line occurs at 10616 Å, implying a velocity 15 1 rest-frame equivalent width of 22 2Å(12 2Åfor[CIII] λ1907 offset of $vLyα 340+30 km s− . The full width at half-maximum ± ± = − 1 and 10 1ÅforCIII] λ1909), similar to the value recently derived of the Lyα line (360 km s− ;Oeschetal.2015) thus indicates that in a gravitationally± lensed galaxy at z 6.024 (Stark et al. 2015a). a substantial fraction of the Lyα flux leaves the galaxy between = 1 The flux ratio of the [C III],C III]doubletprovidesameasure- 340 and 520 km s− . We note that if we were to adopt the trun- ment of the electron density of the ionized gas. The ratio of [C III] cated Gaussian redshift for Lyα, the inferred velocity offset would 4 3 1 λ1907/C III] λ1909 varies from 0.8 for ne 3 10 cm− to be somewhat smaller (260 km s− ), but more importantly, the line 2 3 ≃ = × 1.5 for n 10 cm− . The measured [C III] λ1907/C III]1909 flux profile still would imply a significant amount of flux emerging at Downloaded from https://academic.oup.com/mnras/article-abstract/464/1/469/2236059 by FMRP user on 30 July 2019 e = ratio of EGS-zs8-1 (1.25 0.22) suggests that C III] traces rea- yet larger velocities. The mean velocity offset of EGS-zs8-1 is com- sonably high-density gas.± The electron density of the system is parable to the two measurements presented in Willott et al. (2015) determined by using IRAF’s NEBULAR package (Shaw & Du- but is considerably larger than that inferred in a robustly detected four 1995). Assuming an electron temperature of 15 000 K, con- C III]emitteratz 6.024 (Stark et al. 2015a) and well in excess = sistent with metal-poor C III]-emitting galaxies at lower redshifts of the $vLyα parametrization adopted in the reionization models (e.g. Erb et al. 2010; Christensen et al. 2012;Mainalietal.,in of Choudhury et al. (2015). We discuss the implications of these 12200 3 preparation), we infer an electron density of 9100+7800 cm− for findings for reionization in Section 5.2. EGS-zs8-1. The error bars on the measurement are− calculated by including 1σ error in the flux ratio as well as varying the electron 3.2 EGS-zs8-2 temperature between 12 600 and 20 000 K. While uncertainties are clearly still significant, the C III]densityisnoticeablylargerthan EGS-zs8-2 is another bright (H160 25.1) galaxy identified in 3 = the average density (250 cm− ) traced by [O II]or[SII]atz 2.3 CANDELS imaging by RB16. The IRAC colour of EGS-zs8-2 ≃ (Sanders et al. 2016). The tendency for C III] to imply larger den- ([3.6]Ð[4.5] 0.96 0.17) is redder than EGS-zs8-1, likely re- = ± sities than [O II]and[SII] is well known (e.g. James et al. 2014; flecting yet more extreme optical line emission. We estimate a rest- Mainali et al., in preparation) and may indicate that the higher ion- frame [O III] Hβ equivalent width of 1610 302 Å is required to ization line tends to be produced in denser regions within the galaxy. reproduce the+ flux excess in the [4.5] filter.± A 4.7σ emission fea- Larger samples with multiple density diagnostics are required at ture was identified by RB16 at a wavelength of 1.031 µm. RB16 lower redshift to assess whether the C III] density offset is actually tentatively interpret this feature as Lyα. physical. We obtained a Y-band spectrum of EGS-zs8-2 with the goal of The detection of C III] also constrains the systemic redshift (e.g. verifying the putative Lyα detection. The spectrum we obtained Erb et al. 2010;Starketal.2014), providing a valuable measure shows a 7.4σ emission line at 1.0305 µm (Fig. 2a), confirming that of the velocity offset of Lyα, $vLyα.TheLyα velocity offset is EGS-zs8-2 is indeed a Lyα emitter at zLyα 7.477. The measured 18 2 =1 a key input parameter for models which seek to map the evolv- line flux (7.4 1.0 10− erg cm− s− ) is less than half that ing number counts of Lyα emitters to IGM ionization state (e.g. of EGS-zs8-1.± We calculate× the Lyα equivalent width using the Lyman α and C III]emissioninz 7–9 Galaxies 473 Choudhury et al. 2015). Yet owing to the lack of strong nebular broad-band SED to estimate the underlying continuum flux. The = resulting value (WLyα 9.3 1.4 Å) is the smallest of the RB16 galaxies. = ± The MOSFIRE H-band spectrum covers 14 587 to 17 914 Å, corresponding to rest-frame wavelengths between 1720 and 2113 Å for EGS-zs8-2. In Fig. 2(b), we show the spectral window centred on the [C III], C III] doublet. No emission lines are visible. There are two weak sky lines in the wavelength range over which the doublet is situated. However, the separation of the individual components of the doublet is such that at least one of the two lines must be located in a clean region of the spectrum. We estimate 3σ upper 18 2 1 limits of 2.3 10− erg cm− s− for individual components. The × Downloaded from https://academic.oup.com/mnras/article-abstract/464/1/469/2236059 by FMRP user on 30 July 2019 non-detection suggests that the total flux in the C III]doubletmust be less than 62 per cent of the observed Lyα flux, fully consistent with the ratio observed in EGS-zs8-1 and in extreme C III] emitters at lower redshift. We place a 3σ upper limit on the doublet rest- frame equivalent width of < 14 Å. Deeper data may yet detect C III] in EGS-zs8-2. 3.3 COS-zs7-1 z=7.15 z=7.48 StarkFigure et al. 3. Keck/MOSFIRE2017 Y-band spectrum of COS-zs7-1, a bright Prior to this paper, COS-zs7-1 was the only source from RB16 Figure 2. Keck/MOSFIRE spectra of EGS-zs8-2, a z 7.477 galaxy presented in RB16. (Left:) two-dimensional and one-dimensional Y-band spectra centred (H 25.1) dropout presented in RB16. We identify an emission feature = lacking a near-IR spectrum. Similar to the other galaxies from RB16, 1.05= 1.055 1.06 1.065 1.07 1.075 on the Lyα emission line, confirming the tentative redshift identification presented in RB16. (Right:) H-band observations showing non-detection of the at the spatial position of the dropout at 9913 Å which is likely to be Lyα [C III], C III] λλ1907, 1909 doublet. The top panels show the two-dimensional SNR maps (black is positive), and the bottom panel shows the flux-calibrated COS-zs7-1 is bright in the near-IR (H 25.1) and has IRAC 50 160 = at z 7.154. The top panel shows the two-dimensional SNR map (black one-dimensional extractions. colour ([3.6]–[4.5] 1.03 0.15) that indicates intense optical = 40 = ± is positive), clearly showing the characteristic negative–positive–negative line emission. In addition to RB16, the galaxy has been reported signature expected from the subtraction of dithered data. The bottom panel Pixel 30 elsewhere (e.g. Tilvi et al. 2013;Bowleretal.2014). We estimate an shows0.2 the flux-calibrated one-dimensional extraction. 20MNRAS 464, 469Ð479 (2017) [O III] Hβ rest-frame equivalent width of 1854 325 Å based on EGS-zs8-1 + ± 10 the [4.5] flux excess, making COS-zs7-1 the most extreme optical ] 1 0 1 18 Å Signal x 10 /Å] / which we have obtained new spectral constraints (COS-zs7-1, EGS- 2 line emitter in the RB16 sample. RB16 derive a reasonably well- 2 0.1 Flux 0.12 zs8-1, EGS-zs8-2). We fit the available emission line and broad- constrained photometric redshift (zphot 7.14+ ) that places Lyα A)] 2 Smooth 0.12 band fluxes using the Bayesian spectral interpretation tool BEA- 2 in a narrow 290 Å window between 9750= and− 10 041 Å. Gauss GLE (Chevallard & Charlot 2016), which incorporates in a flexible erg/s/cm 1 The Keck/MOSFIRE Y-band spectrum spans between 9750 and erg/s/cm 0 1 17 and consistent way the production of radiation in galaxies and its 11 238 Å, covering the full range over which Lyα is predicted to lie. − transfer through the interstellar and intergalactic media. The version We identify a 6.25σ emission line at 9913 Å that is coincident with 0 −of0.1 BEAGLE used here relies on the models of Gutkin, Charlot & the expected spatial position of COS-zs7-1 (Fig. 3). The emission z=7.7302±0.0006 Flux [10 Bruzual (2016), who follow the prescription−17 of Charlot2 & Longhetti 1 line is seen to have the standard negative–positive–negative pattern, f(Ly ) = 1.7±0.3 10 erg/s/cm (2001) to describe the emission from stars and the interstellar gas, indicating that it is present in both dither positions. If the feature is Flux density [erg / (s cm −based0.2 on a combination of the latest version of the Bruzual & 2 Lyα, it would correspond to z α 7.154, in excellent agreement 1.05 1.055 1.06 1.065 1.07 1.075 Ly = Charlot (2003)stellarpopulationsynthesismodelwiththestan- 11700 11750 11800 11850 11900 with the photometric redshift derived by RB16. No other emission Observed Wavelength [µm] [Ang] dard photoionization code CLOUDY (Ferland et al. 2013). The main lines are visible at the spatial position of COS-zs7-1 in the Y-band adjustable parameters of the photoionized gas are the interstellar spectrum. We conclude that Lyα is the most likely interpretation ofOesch et al. 2015 z=7.73 Zitrin et al. 2015 z=8.68 metallicity, Z , the typical ionization parameter of newly ionized the line given the pronounced dropout in the z band and the evidence ISM H II regions, US (which characterizes the ratio of ionizing photon to for strong [O III] Hβ emission in the [4.5] filter. The emission line gas densities at the edge of the Stroemgren sphere), and the dust- is clearly distinct+ from sky lines with emission spanning 9905– to-metal mass ratio, ξ (which characterizes the depletion of metals 9915 Å; however, the red side of the line coincides with positive d on to dust grains). We consider here models with hydrogen density residuals from a weak OH line at 9917 Å, complicating the line flux n 100 cm 3, and two values of C/O abundance ratios, equal to measurement. Integrating the emission line blueward of the OH H − 1.0= and 0.5 the standard value in nearby galaxies [(C/O) 0.44. line, we find a total flux of 2.5 0.4 10 17 erg cm 2 s 1 and a − − − Attenuation× by dust is described using the 2-component⊙ model≈ of rest-frame Lyα equivalent width± of 28× 4Å. Charlot & Fall (2000), combined with the Chevallard et al. (2013) Table 2 summarizes the various emission± line measures and the ‘quasi-universal’ prescription to account for the effects linked to related physical properties for all three sources in the context of dust/star geometry [including interstellar medium (ISM) clumpi- earlier work. ness] and galaxy inclination. Finally, we adopt the prescription of Inoue et al. (2014) to include absorption by the IGM. We parametrize the star formation histories of model 4PHOTOIONIZATIONMODELLING galaxies in BEAGLE as exponentially delayed functions The broad-band SEDs of the RB16 galaxies suggest the presence ψ(t) t exp ( t/τ ), for star formation time-scale in the range ∝ − SFR of extremely large equivalent width [O III] Hβ emission. Here we 7 log (τ /yr) 10.5 and formation redshift in the range z + ≤ SFR ≤ obs investigate whether the available data require an intense radiation zform 50 (where zobs is the observed galaxy redshift). We field that may favour the escape of Lyα. In the case of EGS-zs8-1 adopt≤ a standard≤ Chabrier (2003) initial mass function and assume and EGS-zs8-2, we fold in the new constraints on [C III], C III] emis- that all stars in a given galaxy have the same metallicity, in the sion. We focus our analysis on the three galaxies from RB16 for range 2.2 log(Z/Z ) 0.25. We superpose on this smooth − ≤ ⊙ ≤ MNRAS 464, 469–479 (2017) Ionised ‘bubbles’ Dijkstra et al. 2014 Robertson et al. 2010 What makes these sources special? 476 D. P. Stark et al. Two possibilities: 5.1 Impact of local radiation field on Lyα equivalent widths The IRAC 4.5 µm flux excesses of the RB16 sample are suggestive • These sources are of extreme optical line emission. Photoionization models indicate selected on [OIII] - the that the data require very large sSFRs, moderately low metallicity, and large ξion∗ (Table 3), suggesting efficient LyC production rates. source of ionising The distribution of neutral hydrogen in the circum-galactic medium could be very different in such young, rapidly growing systems. photons can potentially Conceivably, both the intense radiation field and enhanced stellar create an ionised bubble feedback of the RB16 galaxies could disrupt the surrounding dis- tribution of gas, reducing the covering fraction of neutral hydrogen and boosting the transmission of Lyα. If the escape fraction of Lyα Downloaded from https://academic.oup.com/mnras/article-abstract/464/1/469/2236059 by FMRP user on 30 July 2019 • These sources are bright through the galaxy is indeed related to the sSFR and ξion∗ ,weshould detect evidence of a larger Lyα emitter fraction in extreme optical (>L*) and therefore likely line emitters located just after reionization (4 FigureStark 6. Theet al. fraction 2017 of Lyα emitters with WLyα > 25 Å among UV aVLT/FORSsurveydescribedinbyVanzellaetal.(2009). Our luminous (MUV < 20.25) galaxies at z>4. The Lyα fraction in the RB16 goal is to determine whether Lyα equivalent widths tend to be − sample is larger than found in previous studies of z>7 galaxies. The open enhanced in the subset of 4 MNRAS 464, 469Ð479 (2017) Spectroscopic confirmation of galaxies in the EoR The Astrophysical Journal, 819:129 (11pp), 2016 March 10 Oesch et al. Table 3 Assumed LFs for z ∼ 10–11 Number Density Estimates -5 Reference f * 10 M* α Nexp (Mpc−3)(mag)(<−22.1) Bouwens et al. (2015b) 1.65 −20.97 −2.38 0.06 Finkelstein et al. (2015) 0.96 −20.55 −2.90 0.002 Mashian et al. (2015) 0.25 −21.20Zitrin −et2.20 al. 2015 0.03 Mason et al. (2015) 0.30 −21.05 −2.61 0.01 Trac et al. (2015) 5.00 50 −20.18 −2.22 0.002 40 Pixel 30 Note. The parameters f*, M*, and α 20represent the three parameters of the 10 1 0 1 18 x 10 Schechter UV LF taken from the different papers.Signal Flux A)] 2 Smooth 2 Gauss 1 1 when assuming a more realistic case where0 the emission line Oesch et al. 2016 Figure 7. Redshift and UV luminosities of known high-redshift galaxies from flux is distributed over a combination 1 of lines (e.g., blank field surveys. Dark filled squares correspond to spectroscopically fi Flux density [erg / (s cm Hβ+[O III]), we can con dently invalidate 2 such a solution. confirmed sources, while small gray dots are photometric redshifts (Bouwens 11700 11750 11800 11850 11900 The lower left panel in Figure 4 compares the measured grism [Ang] et al. 2015b). GN-z11 clearly stands out as one of the most luminous currently spectrum with that expected for the best-fit lower redshift known galaxies at all redshifts z>6 and is by far the most distantmeasured solution we had previously identified (Oesch et al. 2014).A galaxy with spectroscopy (black squares; see Oesch et al. 2015b, for a full list of references). Wider area surveys with future near-infrared telescopes (such as strong line emitter SED is clearly inconsistent with the data. WFIRST) will be required to determine how common such luminous sources Apart from the emission lines, which we do not detect, this really are at z>10. model also predicts weak continuum flux across the whole wavelength range. At <1.47 μm, this is higher than the the observed spectrum has a break of 1->ffshort long 0.68 fl ( nn) observed mean, while at >1.47 μm the expected ux is too low at 2σ, thus indicating again that we can marginally rule out a compared to the observations. Overall the likelihood of a z∼2 4000 Å break based on the spectrum alone without even extreme emission line SED based on our grism data is less than including the photometric constraints. 10−6 and can be ruled out. Note that in very similar grism observations for a source triply imaged by a CLASH foreground cluster, emission line 4. DISCUSSION contamination could also be excluded (Pirzkal et al. 2015). We 4.1. Physical Properties of GN-z11 thus have no indication currently that any of the recent z∼9–11 galaxy candidates identified with HST is a lower Despite being the most distant known galaxy, GN-z11 is redshift strong emission line contaminant (but see, e.g., relatively bright and reliably detected in both IRAC 3.6 and Brammer et al. 2013, for a possible z∼12 candidate). 4.5 μm bands from the S-CANDELS survey (Ashby et al. 2015). This provides a sampling of its rest-frame UV SED and even partially covers the rest-frame optical wave- 3.3. Excluding a Lower-redshift Dusty or Quiescent Galaxy lengths in the IRAC 4.5 μm band (see Figure 6). The photometry of GN-z11 is consistent with a SED of Another potential source of contamination for very high logMM ~ 9 using standard templates (Bruzual & Char- redshift galaxy samples are dusty z∼2–3 sources with strong lot 2003, see appendix). The UV continuum is relatively blue 4000 Å or Balmer breaks (Hayes et al. 2012; Oesch et al. with a UV spectral slope β=−2.5±0.2 as derived from a 2012). However, the fact that the IRAC data for GN-z11 show powerlaw fit to the H160, K, and [3.6] fluxes only, indicating that it has a very blue continuum longward of 1.6 μm, together very little dust extinction (see also Wilkins et al. 2016). with the very red color in the WFC3/IR photometry, already Together with the absence of a strong Balmer break, this is rules out such a solution (see SED plot in Figure 4). consistent with a young stellar age of this galaxy. The best fit Nevertheless, we additionally explore what constraints the age is only 40 Myr (<110 Myr at 1σ). GN-z11 thus formed its grism spectrum alone can set on such a solution. stars relatively rapidly. The inferred star formation rate is 24 ± The expected flux for such a red galaxy increases gradually −1 10 Me yr . All the inferred physical parameters for GN-z11 across the wavelength range covered by the G141 grism, unlike are summarized in Table 2. Overall, our results show that what we observe in the data (lower right in Figure 4). galaxy build-up was well underway at 400 Myr after the fi ∼ Compared to our best- t solution (see next section) we measure Big Bang. a Δχ2=15 when comparing the data with the expected grism flux. Apart from the extremely large discrepancy with the IRAC photometry, we can thus exclude this solution at 98.9% 4.2. The Number Density of Very Bright z > 10 Galaxies confidence based on the spectrum alone. The spectrum of GN-z11 indicates that its continuum break Similar conclusions can be drawn from the break strength lieswithin the H160 filter (which covers ∼1.4–1.7 μm; see Figure 6). alone (see e.g., Spinrad et al. 1998). Assuming that the The rest-frame UV continuum flux of this galaxy is therefore observed break at 1.47 μm corresponds to 4000 Å at z 2.7, a = ∼0.4 mag brighter than inferred from the H160 magnitude. The galaxy with a maximally old SED (single burst at z=15) estimated absolute magnitude is M =−22.1±0.2, which is fl short long UV would show a ux ratio of (1- 7 12 Lyman Break spectroscopy Watson et al. 2015 Figure 2 | Spectrum of A1689-zD1. The 1D (lower) and 2D (upper) SED (blue line) are shown. The Lyα break is close to the spectrograph’s binned spectra are shown, with the 68% confidence uncertainty on the NIR/VIS arm split, however, the break is clearly detected in the NIR arm 1D spectrum in the bottom panel. The redshift z = 7.5 is determined from alone. A nearby galaxy (z ~ 2) visible in the bottom part of the 2D spec- the Lyα break at 1035 nm. Sky absorption (grey bands) and the best-fit trum is detected in both the VIS and NIR arms. absence of sky emission lines, making this by far the deepest intrin- 0.61 ± 0.12 mJy in the combined image and at 2.4–3.1σ significance sic spectrum published of a reionization era object, highlighting the in each of the three individual observations (Fig. 3). A1689-zD1 is difficulty of obtaining UV redshifts for objects at this epoch that are located within the primary beam FWHM of one pointing and the not strongly dominated by emission lines. The restframe equivalent sensitivity (RMS) around its position is 0.12 mJy/beam, 42% of the width limits are < 4 Å for both Lyα and CIII] 1909Å. Our search sensitivity of the deepest part of the mosaic. The source is the space for Lyα is largely free of sky emission lines; they cover 16% brightest in the mosaic area of 5 square arcminutes. It coincides with of the range. the UV position of A1689-zD1 and is 1.5˝ away from the next near- Fits to the galaxy’s spectral energy distribution (SED) yield a est object in the Hubble image, which is not detected in the ALMA 9 map. No line emission is convincingly detected in the ALMA spec- lensing-corrected stellar mass of 1.7×10 M (i.e. +0.15 tral data, for which we cover about half of the X-shooter–allowed log(M⋆/M ) = 9.23–0.16, with a best-fitting stellar age of 80 Myr (i.e. II +0.26 redshift space for the [C ] 158µm line (see Methods). The derived a light-weighted age, t, of log(t/yr) = 7.91–0.24. The lensing-corrected total infrared (TIR) luminosity corrected for lensing and for CMB UV luminosity is ~1.8×1010 L , resulting in a star-formation rate 12 10 –1 effects is 6.2×10 L , corresponding to a SFR of about 9 M yr , estimate of 2.7±0.3 M yr–1 based on the UV emission and uncor- 7 with a dust mass in the galaxy of 4×10 M , assuming a dust tem- rected for dust extinction, for a Chabrier initial mass function11. perature of 35 K. The dust mass we determine is conservative and is A1689-zD1 is thus a sub-L* galaxy, meaning that it is among the unlikely to be lower than about 2×107 M . It could in principle be 9 faint galaxies that dominate star-formation at this epoch . larger by an order of magnitude, due to temperature and geometry Mosaic observations of the lensing cluster were obtained with the effects (see Methods). Table 1 presents a comparison of the proper- Atacama Large Millimetre Array (ALMA) in Cycles 0 and 1 with ties of A1689-zD1 with other z > 6.5 galaxies with deep mm obser- the receivers tuned to four 3.8 GHz frequency bands between 211 vations. Most of the sources observed so far are more UV-luminous and 241 GHz. A1689-zD1 is located towards the northern edge of than A1689-zD1 and have upper limits somewhat above the dust the mosaic and is detected at 5.0σ with an observed flux of mass found here. Figure 3 | ALMA signal-to-noise ratio (SNR) maps of A1689-zD1. of observation 2011.0.00319.S and observation 2012.1.00261.S. A1689- Contours are SNR = 5, 4, 3, 2 (black, solid), –3, –2 (white, dashed). zD1 is detected, left to right, at 5.0σ, 2.4σ, 3.1σ, and 3.0σ. Natural Images and noise maps were primary-beam corrected before making weighting was used and the visibilities were tapered with a 1˝ circular SNR maps. Beam sizes are shown, bottom left in each panel. Panels are Gaussian kernel, resulting in beams of 1.36˝×1.15˝, 1.19˝×1.09˝, 8˝×8˝. The panels show, left to right, the combined data, the two tunings 1.43˝×1.12˝, 1.43˝×1.17˝ left to right. Grism spectroscopy NEW CONTAM! Lyα Redshift 9 10 11 12 1.0 0.5 0.0 Trace −0.5 scale [arcsec] −1.0 6001.1 1.2 1.3 1.4 1.5 1.6 GN-z11 HST WFC3/IR G141 Grism Spectrum 400 200 Low-resolution 0 spectroscopy good for Flux Density [nJy] Flux Density [nJy] −200 Model at detecting Lyman break +0.08 zgrism=11.09−0.12 contamination −400 1.1 1.2 1.3 1.4 1.5 1.6 Wavelength [µm] Oesch et al. 2016 Grism spectroscopy The Astrophysical Journal Letters,765:L2(6pp),2013March1 Brammer et al. For single band 1” 1” detections low redshift 15 15 2 line emitters are a new 2 10 10 erg/s/cm erg/s/cm class of interloper 18 18 − 5 − 5 0 0 [OIII] at z=2 line flux / 10 line flux / 10 10 10 F160W kernel Contam. Uniform kernel (R=0.30”) 8 UDFj-39546284 8 UDF-40106456 6 Ly , z = 12.12? 6 (H )+[OIII]+H , z = 1.303 S/N 4 [OIII] 5007, z = 2.19? S/N 4 2 2 0 0 1.1 1.2 1.3 1.4 1.5 1.6 1.1 1.2 1.3 1.4 1.5 1.6 Bouwens et al. 2011; Ellis et al. 2013 λ/µm λ/µm Figure 3. Optimal extraction of the UDFj-39546284Brammer spectrum (left) et and al. that 2013 of a comparison object, UDF-40106456 (right). The top panels show the stacked 2D spectra and the spectra cross-correlated with the H160 image kernel, which is indicated at left. The upper spectra show the 2D cross-correlation extracted along the trace and scaled by the G141 sensitivity curve and ∆λ of the spectrum, which, for a uniform kernel, would give an integrated line flux with the units as labeled. The same cross-correlation is applied to the 2D pixel variance array, yielding the uncertainties shaded in gray. The bottom panels show the signal-to-noise spectrum. While there are additional apparently significant features at λ < 1.5 µm, these are likely due to contamination rather than coming from UDFj-39546284 (Section 3.3). The gray curves in the bottom panels show the S/NinR 0′′. 3 apertures along the trace. The red curves indicate the potential contamination from nearby sources. The filled orange regions are model emission-line spectra,= whose shapes match those of the observed lines. (A color version of this figure is available in the online journal.) cross-correlation technique enhances the detection significance population of extreme [O iii]emission-linegalaxiesatz 1.7 by a factor of two compared to simple photometry along the was recently identified by van der Wel et al. (2011)∼ from trace within an equivalent 0′′.30 aperture. This example demon- their significant line contribution to the J125 photometry in strates that the cross-correlation technique works and is able to the CANDELS survey. Additional galaxies with [O iii]rest- recover extremely faint emission lines. frame equivalent widths reaching 2000 Å have been identified in WFC3 grism spectroscopy by Atek et al. (2011)andBrammer 4. LINE IDENTIFICATION et al. (2012b). The strongest emitters in van der Wel et al. (2011) have J125 H160 1, with [O iii]intheJ125 band. While such 4.1. Is UDFj-39546284 at z 12? − ∼− = colors can mimic those of high-redshift dropout galaxies (Atek If the galaxy is at z 12, as is suggested based on its strong et al. 2011), even more extreme equivalent widths at !3000 Å ∼ (rest frame) are required to reach J125/140 H160 > 1.4observed photometric break between the JH140 and H160 filters (Ellis et al. − 2013;Bouwensetal.2013), the line—if real—can be identified for UDFj-39546284. as Lyα redshifted to z 12.12. The rest-frame equivalent width of Lyα would not be unreasonably= high at >170 Å (accounting 4.3. Discovery of a Possible Analog: An iii z for the z 12 Lyman break in H160); such values can be reached Extreme [O ] Emitter at 1.605 = = in young, low-metallicity starbursts at high redshift (Schaerer We have discovered a very bright example of such an 2003). However, such strong Lyα emission might be unexpected extreme emission-line galaxy in G141 grism observations of the early in the reionization epoch when the neutral fraction is high Extended Groth Strip (EGS) field (GO-12547, PI: Cooper). This (Santos 2004; but see also Dijkstra et al. 2011). More to the remarkable object, EGS-XEW-1, located at α 14:17:58.2, point, if the line is real it can account for most or all of the H160 δ +52:31:35 and shown in Figure 4,isan“[O= iii]blob”at flux, meaning that the photometric break does not necessarily = z 1.605 with JH140 21.5 and a complex morphology reflect a strong continuum break and the photometric redshift is comprised= of diffuse (A) and= compact (B) components separated unreliable. Therefore, the line could also be a longer-wavelength by 1′′.Theexposuretimesandditheredpixelsamplingfor feature at much lower redshift, a possibility discussed by Ellis the Cooper et al. grism program are nearly identical to those et al. (2013). of 3D-HST, and the spectra were processed with the 3D-HST interlacing software as described above. The diffuse component, 4.2. Low-redshift Solutions—[O iii]atz 2.2 = which is extended over more than 1′′ (8.5 kpc), has a combined Although we cannot exclude other low-redshift identifications observed-frame equivalent width of nearly 9000 Å for the such as [O ii]atz 3.28 or Hα at z 1.44, a likely possibility blended Hβ and [O iii]λ4959,5007 emission lines. The more is that the line is= [O iii]λ4959,5007= at z 2.19 0.01. A compact component has EW 3000 160 Å. = ± = ± 4 Spectroscopic confirmation of galaxies in the EoR The Astrophysical Journal, 819:129 (11pp), 2016 March 10 Oesch et al. Table 3 Assumed LFs for z ∼ 10–11 Number DensityNEW Estimates CONTAM! -5 Reference f * 10 M* α Nexp Lyα Redshift (Mpc−3)(mag)(9<−22.1) 10 11 12 1.0 Bouwens et al. (2015b) 1.65 −20.97 0.5−2.38 0.06 Finkelstein et al. (2015) 0.96 −20.55 0.0−2.90Trace 0.002 −0.5 Mashian et al. (2015) 0.25 −21.20 scale [arcsec] −1.0−2.20 0.03 Mason et al. (2015) 0.30 −21.05 −2.61 0.01 6001.1 1.2 1.3 1.4 1.5 1.6 Trac et al. (2015) 5.00 −20.18 −2.22GN-z11 HST WFC3/IR 0.002 G141 Grism Spectrum 400 Note. The parameters f*, M*, and α represent the three parameters of the Schechter UV LF taken from the different papers. 200 0 Flux Density [nJy] Flux Density [nJy] when assuming a more realistic case where−200 the emission line Model at +0.08 Oesch et al. 2016 Figure 7.zgrismRedshift=11.09−0.12 and UV luminosities of known high-redshift galaxies from flux is distributed over a combination of lines (e.g., contamination blank field surveys. Dark filled squares correspond to spectroscopically fi −400 Hβ+[O III]), we can con dently invalidate1.1 such a1.2 solution.1.3 1.4confirmed1.5 sources,1.6 while small gray dots are photometric redshifts (Bouwens Wavelength [µm] The lower left panel in Figure 4 compares the measured grism et al. 2015b). GN-z11 clearly stands out as one of the most luminous currently spectrum with that expected for the best-fit lower redshift known galaxies at all redshifts z>6 and is by far the most distantmeasured solution we had previously identified (Oesch et al. 2014).A galaxy with spectroscopy (black squares; see Oesch et al. 2015b, for a full list of references). Wider area surveys with future near-infrared telescopes (such as strong line emitter SED is clearly inconsistent with the data. WFIRST) will be required to determine how common such luminous sources Apart from the emission lines, which we do not detect, this really are at z>10. model also predicts weak continuum flux across the whole wavelength range. At <1.47 μm, this is higher than the the observed spectrum has a break of 1->ffshort long 0.68 fl ( nn) observed mean, while at >1.47 μm the expected ux is too low at 2σ, thus indicating again that we can marginally rule out a compared to the observations. Overall the likelihood of a z∼2 4000 Å break based on the spectrum alone without even extreme emission line SED based on our grism data is less than including the photometric constraints. 10−6 and can be ruled out. Note that in very similar grism observations for a source triply imaged by a CLASH foreground cluster, emission line 4. DISCUSSION contamination could also be excluded (Pirzkal et al. 2015). We 4.1. Physical Properties of GN-z11 thus have no indication currently that any of the recent z∼9–11 galaxy candidates identified with HST is a lower Despite being the most distant known galaxy, GN-z11 is redshift strong emission line contaminant (but see, e.g., relatively bright and reliably detected in both IRAC 3.6 and Brammer et al. 2013, for a possible z∼12 candidate). 4.5 μm bands from the S-CANDELS survey (Ashby et al. 2015). This provides a sampling of its rest-frame UV SED and even partially covers the rest-frame optical wave- 3.3. Excluding a Lower-redshift Dusty or Quiescent Galaxy lengths in the IRAC 4.5 μm band (see Figure 6). The photometry of GN-z11 is consistent with a SED of Another potential source of contamination for very high logMM ~ 9 using standard templates (Bruzual & Char- redshift galaxy samples are dusty z∼2–3 sources with strong lot 2003, see appendix). The UV continuum is relatively blue 4000 Å or Balmer breaks (Hayes et al. 2012; Oesch et al. with a UV spectral slope β=−2.5±0.2 as derived from a 2012). However, the fact that the IRAC data for GN-z11 show powerlaw fit to the H160, K, and [3.6] fluxes only, indicating that it has a very blue continuum longward of 1.6 μm, together very little dust extinction (see also Wilkins et al. 2016). with the very red color in the WFC3/IR photometry, already Together with the absence of a strong Balmer break, this is rules out such a solution (see SED plot in Figure 4). consistent with a young stellar age of this galaxy. The best fit Nevertheless, we additionally explore what constraints the age is only 40 Myr (<110 Myr at 1σ). GN-z11 thus formed its grism spectrum alone can set on such a solution. stars relatively rapidly. The inferred star formation rate is 24 ± The expected flux for such a red galaxy increases gradually −1 10 Me yr . All the inferred physical parameters for GN-z11 across the wavelength range covered by the G141 grism, unlike are summarized in Table 2. Overall, our results show that what we observe in the data (lower right in Figure 4). galaxy build-up was well underway at 400 Myr after the fi ∼ Compared to our best- t solution (see next section) we measure Big Bang. a Δχ2=15 when comparing the data with the expected grism flux. Apart from the extremely large discrepancy with the IRAC photometry, we can thus exclude this solution at 98.9% 4.2. The Number Density of Very Bright z > 10 Galaxies confidence based on the spectrum alone. The spectrum of GN-z11 indicates that its continuum break Similar conclusions can be drawn from the break strength lieswithin the H160 filter (which covers ∼1.4–1.7 μm; see Figure 6). alone (see e.g., Spinrad et al. 1998). Assuming that the The rest-frame UV continuum flux of this galaxy is therefore observed break at 1.47 μm corresponds to 4000 Å at z 2.7, a = ∼0.4 mag brighter than inferred from the H160 magnitude. The galaxy with a maximally old SED (single burst at z=15) estimated absolute magnitude is M =−22.1±0.2, which is fl short long UV would show a ux ratio of (1- 7 Low- and high-redshift spectroscopic tracers log Luminosity z~0 Wavelength (μm) Low- and high-redshift spectroscopic tracers log Luminosity z~4 Wavelength (μm) Low- and high-redshift spectroscopic tracers [CII] log Luminosity z~7 Wavelength (μm) ALMA as a redshift machine? z=6.6 ALMA cycle 0 Ouchi et al., 2013 see also Ota et al. 2014, Maiolino et al. 2015 Himiko revisited: faint but detectable [CII] Low surface-brightness Lyα [CII] at the origin of SFR-L[CII] scatter? 4 Carniani et al. The other component, B[CII], peaks at 175 30 km/s and is narrower ( FWHM = 70 20 km/s)− ± than the former component. The knot of± the [CII] emission is co-aligned with the UV position of clump-B,[CII] indicating that [CII] and UV emission arise from the same region. Since components B[CII] and A[CII] overlap in velocity, the flux map B[CII] shows also a tail emission extending to the west that is assocaited with the A[CII] component. The core of the B[CII] emission is not spatially resolved indicating the the [Cii] line is powered by a compact source with physical size < 2 kpc. For this component 8 we infer a [Cii] luminosity L[CII]=(0.50 0.13) 10 L . Since around the Lyα redshift we do± not detect× any⊙ emission close to the UV clumps A and C, we search for line emission in the ALMA cube between -1000 km/s and 1000 km/s relative to the redshift of Lyα and with level of significanceCarniani,> 3Maiolino,σ. Only Smit a putative & Amorin, detection 2017 is found Fig. 2.— L[CII] versus SFR diagram. The green line shows the at 500 km/s and located at the UV position of the relations for local star-forming galaxies by De Looze et al. (2014), clump∼− C. Because of the low significance (S/N=3.2), the while the dotted grey line is the best-fit relation for Z = 0.15Z emission can be spurious due to noise fluctuation, hence galaxies simulated by Vallini et al. (2015). The location of Himiko’s⊙ total emission is shown with the large red circle. The location of we consider it as a non detection. For the two UV clumps Himiko’s subclumps is shown with red squares. We also report the A and C, we therefore infer an upper limit on the [Cii] location of CR7 and its subclumps. The dotted circle shows the 8 luminosity L[CII]< 0.2 10 L where we assume a line previous upper limit on the [Cii]emissionforHimikoobtainedby × ⊙ Ouchi et al. (2013). width of 100 km/s. We note that while the [Cii] emission in clump B(= B ) is fully consistent with the local L –SFR rela- et al. 2015). [CII] [CII] tion, clumps A, C and A[CII] are scattered outside the lo- 3.3. Multi-component system cal relation (Figure 2), as observed in other high-z galax- ies (e.g. Maiolino et al. 2015). Given the multi-clump shape of Himiko in the rest- As discussed in Carniani et al. (2017), positional offsets frame UV images and the extended [Cii] emission de- between UV and [Cii] emission may be ascribed to spa- tected in the smoothed ALMA observations, in this sec- tially distinct regions of the galaxy, and of their circum- tion we investigate the morphology of [Cii] emission and galactic environment, characterised by different physical its connection with the UV and Lyα counterparts. properties. For instance, the low [Cii] luminosity at the A channel map analysis performed on the non- location of the UV regions can be interpreted as a con- smoothed combined cube, which has an angular reso- sequence of a local low metal enrichment level in these lution of 0.39′′ 0.31′′, reveals that the extended [Cii] star-forming regions, but also in terms of strong feed- × emission discussed in the previous Section is the result back ionizing or expelling gas (Vallini et al. 2015; Katz of two distinct components, which will be referred to as et al. 2016; Olsen et al. 2017). Spatially-offset [Cii]emis- A[CII] and B[CII]. The flux maps and spectra of these two sion may also be explained in terms of dust obscura- components are shown in Figure 3. tion and/or outflowing/inflowing gas. In the former sce- We identify the component A[CII] with a S/N=5 in nario [Cii] is excited in-situ by star-formation whose UV the channel map from -100 km/s to -365 km/s. The emission is heavily dust-obscured. In this context we centroid of the emission is spatially offset by 0.2′′ to- note that Ouchi et al. (2013) infer a dust attenuation ward the West relative to the UV position of the∼ (bright- for Himiko of E(B-V)=0.15, which can hide a significant est) clump-A, but it is fully consistent with the peak fraction of star forming regions traced by the UV emis- of the extended Lyα nebula observed by Ouchi et al. sion. On the other hand, the spatially-offset [Cii] can (2013) (yellow diamond in Fig.3). We exclude that be associated to a satellite clumps in the process of ac- this [Cii] component is directly associated with the UV creting, or clumps expelled by galactic outflows; in these clump A since the [Cii] emission level at the location cases the [Cii] emission is excited by the UV radiation of the UV emission is lower than 2σ. As we will dis- of the closest star-formation region (e.g. clump A). This cuss later, positional offsets between UV and FIR line last scenario is also supported by the fact that Himiko emission are not so rare in primeval galaxies (Maiolino reveals a triple major merger event whose extended Lyα et al. 2015; Willott et al. 2015; Carniani et al. 2017). nebula emission may be powered by both star formation By fitting a 2D elliptical Gaussian profile to the chan- and galactic winds (Ouchi et al. 2013; Zabl et al. 2015). nel map, we find that the [Cii] emission of component In summary UV and [Cii] emission can trace dif- A[CII] is spatially resolved with a beam-deconvolved size ferent regions that should be treated as different sub- of (0.68 0.10)′′ (0.41 0.10)′′, which corresponds to components of the same system. A detailed discussion of a physical± size of× 3.7 kpc.± The [Cii] profile peaks at multiple sub-components observed in z>5 star-forming 175 30 km/s and∼ has a line width of 240 80 km/s. galaxies, as well as their offset relative to the star form- − ± 8 ± We measure L[CII]=(0.85 0.13) 10 L that corre- ing regions traced by the UV emission, is presented in a sponds to the 70% of the± total [Cii×] luminosity⊙ inferred companion paper (Carniani et al. in prep.). for Himiko. ∼ ALMA [CII] (non)detections RESEARCH LETTER HZ1 HZ2 HZ3 HZ4 HZ5 HZ6 HZ7 HZ8 HZ5a HZ8W HZ9 HZ10 Capak et al. 2015 z=5.5 [CII] dust N 1ʺ E Figure 1 | Optical, [C II] and continuum maps of the sources HZ1–HZ10. Fig. 3. The background images are from HST-ACS in the F814W17 band where The [C II] line detections (red contours) and weak ,158 mm FIR continuum the morphologies will be affected by Lya, except for HZ10, which is Subaru z9 detections (blue contours) are shown with the rest-frame ultraviolet images as band. All objects are detected in [C II], showing that a large amount of gas is the background. The images are 50 3 50 (scale bar at bottom left) and the present in these systems, but only four are detected in continuum. contours are 2, 6 and 10 s with [C II] line profiles for each source shown in 3 star-formation history is much smaller, ,40%, because the majority of Ref. 29 (Calzetti like dust) star-formation is in low luminosity (,L*) galaxies that were already Ref. 20 (SMC like dust) assumed to have little or no dust extinction (see Methods section This work, detections ‘Effects of evolving dust on the global star-formation history’, 2 This work, upper limits This work, mean of undetected Extended Data Fig. 4). A1689-zD1 In contrast to the dust emission, we find .3s detections of the [C II] line in all nine normal galaxies (Fig. 3). The line emission is spectrally 21 resolved in all cases, with [C II] velocity dispersions of 63–163 km s , ) 1 and marginally resolved at our spatial resolution of ,0.5–0.9 arcsec, 1600 9 11 L / indicating galaxies with dynamic masses (Mdyn) of ,10 –10 solar IR L ( masses (M[; see Methods sections ‘Reduction of ALMA data’ and 10 ‘Derivation of physical parameters’). We also detect two optically faint log 0 [C II] emitters at redshifts consistent with the targeted objects. HZ5a is detected near HZ5 at a redshift consistent with the in-falling gas seen in the optical spectra of HZ524. HZ8W corresponds to an optically faint companion to HZ8 and has a similar redshift. Taken together, the –1 direct and serendipitous detections suggest ubiquitous and enhanced [C II] emission in early galaxies similar to that seen in local low-metal- licity systems12 (Fig. 4). The [C II] enhancement in local systems is caused by a lower dust-to- –2 –2 –1 0 1 gas ratio which allows the ultraviolet radiation field to penetrate a Ultraviolet slope, β larger volume of molecular cloud12. Our significantly lower IRX Figure 2 | IRX–b measurements of z . 5 objects. The deficit of infrared values and enhanced [C II]/FIR ratios would suggest a similar effect emission in our sample is evident in the presented infrared excess is happening in high redshift galaxies. But other possible causes of versus ultraviolet slope (IRX–b) relation when compared with models. the transition in obscuration properties with redshift have been Detections are indicated in red, upper limits in orange, the mean IRX suggested25: evolution in metal abundances that changes the ratio (obtained by combining undetected sources) in blue, and intrinsic ultraviolet slope; changes in the dust properties; and dif- 11 A1689-zD1 in maroon. Error bars are 1s, and include standard ferences in the dust geometry. The systems in this study were measurement error and systematic uncertainty added in quadrature. selected to have broad ultraviolet absorption features in their spec- The Meurer29 relation, which assumes Calzetti-like dust and is consistent with typical galaxies at z , 3, is shown as a black solid line, tra that indicate a relatively homogeneous metal abundance of while a model for lower-metallicity SMC-like dust model20 is shown as a ,0.25 times the solar value. At this metallicity, the ultraviolet spec- dashed line. tral slopes are expected to be similar to those of solar metallicity 456 | NATURE | VOL 522 | 25 JUNE 2015 G2015 Macmillan Publishers Limited. All rights reserved ALMA [CII] (non)detections A potential difference between Ly⍺ emitters and 1 dex non-Ly⍺ emitters? scatter! Knudsen et al. 2016 ALMA as a ‘redshift machine’ Uncertainty in photometric redshift requires a (long) scan of the frequency range Weiß et al. 2013 High-EW [OIII] emitters • Colour offers only occur in certain redshift bands - extra constraints on the redshift probability distribution! Smit et al., 2014; 2015, Roberts-Borsani et al. 2016 Emission line signatures of Hα, [OIII] z~6.5 z~6.8 z~7.1 Smit et al. 2015 Smit et al. 2015 Smit et al. 2015 z=6.854 >8 sigma - 24 min on source! Smit et al. 2018 z=6.808 Smit et al. 2018 ALMA spectroscopic confirmations • Not selected on Ly⍺: implications for stellar population or gas column density? • Modestly red UV- continuum slopes and bright Luv: more evolved/ dustier galaxies? Smit et al., 2018 What produces bright [CII] emission? Compilation z 6 7 ⇡ Bright [CII] VR7 z = 6.534 (This paper) = can appear in 109 MASOSA z 6.543 (This paper) sources with EW = 25 50 A˚ 0,Lya ] red and blue EW = 50 120 A˚ 0,Lya [L UV slopes, ] EW > 120 A˚ 108 0,Lya CII and even in [ L high-EW Ly⍺ emitters! 107 Local compilation 0.2 Z 0.1 Z 0.05 Z Vallini+2015 1 3 10 30 100 300 1 SFRUV [M yr ] Matthee et al. 2019 What produces bright [CII] emission? Compilation z 6 7 ⇡ VR7 z = 6.534 (This paper) = 109 MASOSA z 6.543 (This paper) EW = 25 50 A˚ 0,Lya ] EW = 50 120 A˚ 0,Lya [L ] EW > 120 A˚ 108 0,Lya CII [ L Bright [CII] emitters almost always 107 Local compilation 0.2 Z 0.1 Z 0.05 Z Vallini+2015 show bright UV 1 3 10 30 100 300 1 luminosity: SFRUV [M yr ] SFRUV > 20 M⦿/yr Matthee et al. 2019 Origin of [CII] in the interstellar medium Credit: Jorge Pineda Origin of [CII] in the interstellar medium Photoelectric effect is perhaps the most efficient mechanism of [CII] excitation → need dust Credit: Jorge Pineda Photo-electric effect [CII] more easily excited in some sources? -1 One possible -1.5 explanation is a higher gas-to-dust ratio: UV -2 light penetrates further IR / L -2.5 into the photo- [CII] L dissociation region -3 surrounding SF Literature -3.5 This work, continuum detections This work, continuum limits This work, mean of undetected -4 9.5 10 10.5 11 11.5 12 12.5 13 LIR (Lsun) Capak et al. 2015 ! Figure 4 | Our sample has a clear excess of [CII] emission relative to FIR emission when compared with normal lower-redshift systems (z=0-3)6,11,14,29. Detections are indicated in red, upper limits in orange, and the mean of undetected sources is shown in blue. The high [CII]/FIR ratio we measure indicates a lower dust-to-gas ratio, more diffuse clouds, and a more diffuse UV radiation field than seen in normal z~0 galaxies11,12,14. Error bars are 1σ including standard measurement error and systematics added in quadrature. [CII] ‘halos’? [CII] Halo at z ∼ 6 9 !"##$%%&'(%)* Stacking of z=5-7 !"#$%&'( sources: [CII] !"#$%)* contribution from diffuse gas in the circumgalactic medium (CGM)? Evidence for outflows? Fujimoto et al. 2019 Figure 6. Radial surface brightness profiles for the ALMA-HST (circles) and ALMA-ALL (squares) samples. The radial values are estimated by the median of each annulus. The red, green, and blue symbols denote the [C ii]line,rest-frameFIR,andrest-frameUV continuum emission. The rest-frame UV continuum profile is directly derived from the mock HST/H-band image whose resolution is matched to that of the ALMA image. The black dashed and solid curves denote the ALMA synthesized beams in the stacked imagesof the ALMA-HST and ALMA-ALL samples, respectively. All radialprofilesarenormalizedtothepeakvalueofthe[Cii] line. The green and red symbols are slightly shifted along the x-axis for clarity. the S´ersic+exponential profiles for the [Cii] line emis- surface brightness profiles by fitting the two-component sion. We obtain the best-fit scale-length values of rn = S´ersic+exponential profile. We select the best-fit results 3.3 ± 0.1 kpc. This corresponds to the best-fit effective of 6 LAEs at z>5 with MUV ! −21 mag and EWLyα radius of re =5.6 ± 0.1 kpc, showing that the [C ii] halo < 100 A˚ that are consistent with the parameter space is extended ∼5 times more than the stellar continuum in of our sample (Table 1). We find that the radial surface the central galactic component. Note that the visibility- brightness profile of the [Cii] line emission is comparable based profile fitting with uvmultifit (Mart´ı-Vidal et al. to that of the Lyα line emission. The median rn value for 2014) also provides us with the best-fit value of re =5.1± the 6 LAEs is estimated to be 3.8±1.7 kpc that is consis- 1.7 kpc for the halo component, which is consistent with tent with our best estimate of 3.3±0.1 kpc. These results the galfit result within the error. may imply that the physical origin of the extended [Cii] In Figure 9, we compare the radial surface brightness line emission is related to the Lyα halo. profiles of the [Cii] with the Lyα halos universally identi- Note that we confirm that it is hard to reproduce the fied in the normal star-forming galaxies at z ∼ 3–6 (e.g., extended morphology of the [C ii] line emission with the Momose et al. 2016; Leclercq et al. 2017). For the [Cii] central component alone. In the bottom panel of Figure line emission, we adopt the result from the ALMA-ALL 9, we present the residuals of the [C ii] line emission ob- sample due to the high significance detection. For the tained from the best-fit results of the one- (central) and Lyα line emission, we use the recent results with the two- (central+halo) component fittings with uvmulti- deep MUSE data for the high-z LAEs of Leclercq et al. fit. We find that the residuals in the one-component (2017), where the authors estimate the best-fit radial The potential for kinematics from ALMA IFU spectroscopy The promise of ALMA for kinematics using [CII] KMOS-3D: Hα @ z~2 Wisnioski+2017 [OIII] λ 5007Å [OII] λ 3727Å out of K-band out of K-band z=1 z=2 z=3 z=5 z=7 lookback time 6 Gyr 3 Gyr 2 Gyr 1.2 Gyr 800 Myr 2 2 -1 Harrison+2017 2 -1 100 80 C-HiZ_z1_195 Hα intensity vel. (km s ) (km s ) Turner+2017 RT+ O σ ) obs ) -1 1 -1 1 1 1 50 60 0 0 0 0 40 0 (km s arcsec -1 -1 -1 obs vel. (km s -1 Q1 σ 20 -95 0 95 0 40 81 -50 ID:13 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 KROSS: H α @ z~1-1 2 KDS: [OIII]-1 @ z~3.5 U-zvipe_z1_1071 Hα intensity vel. (km s ) σ (km s ) 120 DN O ) obs ) -1 1 1 1 1 -1 50 100 80 0 0 0 0 0 (km s 60 arcsec -1 -1 -1 -1 obs 40 vel. (km s Q2 σ -77 0 77 0 76 152 -50 20 -2 ID:669 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 C-zcos_z1_652 Hα intensity vel. (km s ) (km s ) 40 DN M σ ) obs ) 50 -1 1 1 1 1 -1 30 40 20 30 0 0 0 0 10 (km s arcsec 0 20 -1 -1 -1 -1 obs vel. (km s Q1 σ -40 0 40 0 31 62 -10 10 -2 ID:146 -2 -2 -2 -20 0 -1 0 1 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 -1 2 -1 E-zmus_z1_119 Hα intensity vel. (km s ) (km s ) 200 RT+ M σ ) obs ) 150 -1 1 1 1 1 -1 100 100 0 0 0 0 0 (km s arcsec -1 -1 -1 obs 50 vel. (km s -1 Q1 σ -200 0 200 0 78 156 -100 ID:183 -2 -2 -2 0 -1 0 1 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 200 E-zmus_z1_12 Hα intensity vel. (km s ) σ (km s ) 150 RT+ M ) obs ) -1 1 1 1 1 -1 100 100 0 0 0 0 0 (km s arcsec -100 -1 -1 -1 -1 obs 50 vel. (km s Q1 -202 0 202 0 68 135 σ -200 -2 ID:184 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 E-zmvvd_z1_67 Hα intensity vel. (km s ) (km s ) 100 RT+ M σ ) obs ) 100 -1 1 1 1 1 -1 50 80 0 60 0 0 0 0 -50 (km s arcsec 40 -1 -1 -1 -1 obs vel. (km s Q1 -100 σ -141 0 141 0 50 100 20 -2 ID:316 -2 -2 -2 -150 0 -1 0 1 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 0 10 -10 0 10 2 2 2 -1 2 -1 80 S-CFHIZELS- Hα intensity vel. (km s ) (km s ) RT M σ ) SM14-164290 obs ) -1 1 1 1 1 -1 50 60 0 0 0 0 0 40 (km s arcsec -1 -1 -1 obs 20 -1 vel. (km s Q3 -63 0 63 0 43 85 -50 σ -2 ID:337 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 S-CFHIZELS- Hα intensity vel. (km s ) (km s ) 100 100 RT+ M σ ) SM14-85797 obs ) -1 1 1 1 1 -1 50 80 0 0 0 0 0 60 (km s arcsec 40 -1 -1 -1 -50 obs -1 vel. (km s Q1 -151 0 151 0 50 100 σ 20 -100 -2 ID:359 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 0 10 -10 0 10 arcsec arcsec arcsec arcsec r (kpc) r (kpc) The promise of ALMA for kinematics using [CII] KMOS-3D: Hα @ z~2 Wisnioski+2017 [OIII] λ 5007Å [OII] λ 3727Å out of K-band out of K-band z=1 z=2 z=3 z=5 z=7 lookback time 6 Gyr 3 Gyr 2 Gyr 1.2 Gyr 800 Myr 2 2 -1 Harrison+2017 2 -1 100 80 C-HiZ_z1_195 Hα intensity vel. (km s ) (km s ) Turner+2017 RT+ O σ ) obs ) -1 1 -1 1 1 1 50 60 0 0 0 0 40 0 (km s arcsec -1 -1 -1 obs vel. (km s -1 Q1 -95 0 95 0 40 81 -50 σ 20 ID:13 ALMA band 6 -2 -2 -2 [CII] λ 158 μ m into 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 KROSS: H α @ z~1-1 2 KDS: [OIII]-1 @ z~3.5 U-zvipe_z1_1071 Hα intensity vel. (km s ) σ (km s ) 120 DN O ) obs ) -1 1 1 1 1 -1 50 100 80 0 0 0 0 0 (km s 60 arcsec -1 -1 -1 -1 obs 40 vel. (km s Q2 σ -77 0 77 0 76 152 -50 20 -2 ID:669 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 C-zcos_z1_652 Hα intensity vel. (km s ) (km s ) 40 DN M σ ) obs ) 50 -1 1 1 1 1 -1 30 40 20 30 0 0 0 0 10 (km s arcsec 0 20 -1 -1 -1 -1 obs vel. (km s Q1 σ -40 0 40 0 31 62 -10 10 -2 ID:146 -2 -2 -2 -20 0 -1 0 1 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 -1 2 -1 E-zmus_z1_119 Hα intensity vel. (km s ) (km s ) 200 RT+ M σ ) obs ) 150 -1 1 1 1 1 -1 100 100 0 0 0 0 0 (km s arcsec -1 -1 -1 obs 50 vel. (km s -1 Q1 σ -200 0 200 0 78 156 -100 ID:183 -2 -2 -2 0 -1 0 1 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 200 E-zmus_z1_12 Hα intensity vel. (km s ) σ (km s ) 150 RT+ M ) obs ) -1 1 1 1 1 -1 100 100 0 0 0 0 0 (km s arcsec -100 -1 -1 -1 -1 obs 50 vel. (km s Q1 -202 0 202 0 68 135 σ -200 -2 ID:184 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 E-zmvvd_z1_67 Hα intensity vel. (km s ) (km s ) 100 RT+ M σ ) obs ) 100 -1 1 1 1 1 -1 50 80 0 60 0 0 0 0 -50 (km s arcsec 40 -1 -1 -1 -1 obs vel. (km s Q1 -100 σ -141 0 141 0 50 100 20 -2 ID:316 -2 -2 -2 -150 0 -1 0 1 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 0 10 -10 0 10 2 2 2 -1 2 -1 80 S-CFHIZELS- Hα intensity vel. (km s ) (km s ) RT M σ ) SM14-164290 obs ) -1 1 1 1 1 -1 50 60 0 0 0 0 0 40 (km s arcsec -1 -1 -1 obs 20 -1 vel. (km s Q3 -63 0 63 0 43 85 -50 σ -2 ID:337 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 S-CFHIZELS- Hα intensity vel. (km s ) (km s ) 100 100 RT+ M σ ) SM14-85797 obs ) -1 1 1 1 1 -1 50 80 0 0 0 0 0 60 (km s arcsec 40 -1 -1 -1 -50 obs -1 vel. (km s Q1 -151 0 151 0 50 100 σ 20 -100 -2 ID:359 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 0 10 -10 0 10 arcsec arcsec arcsec arcsec r (kpc) r (kpc) First low-resolution kinematic measurements Smooth accretion from the cosmic web as an important mechanism for galaxy growth at z~7? Smit et al. 2018 First low-resolution kinematic measurements Bowler et al. 2017 Smit et al. 2018 First low-resolution kinematic measurements Observational classification indicates likely ‘rotation-dominated’ systems First low-resolution kinematic measurements Disk model works well, however mergers or gas outflows are still possible Dynamical masses from [CII] 15-50% stellar mass fraction suggest gas rich systems - similar to z~2-3 star- forming disks Smit et al. 2018 Rotation vs. chaotic motion [Cii] in CR7 9 320 320 320 400 2 +80 1.5 240 1.5 Reference frame clump A 240 1.5 240 350 +40 [km/s] Residual Velocity 1.0 160 1.0 160 1.0 160 300 1 eoiy[km/s] Velocity [km/s] 0 Velocity ] ] 0.5 0.5 1 0.5 80 ” 80 80 250 -40 0.0 0 0.0 0 0 0.0 0 Dec. [ -80 200 v[kms HZ10 -0.5 80 -0.5 80 -0.5 80 150 − − -120 − -1 -1.0 160 -1.0 160-160 -1.0 160 100 Relative Declination [”] − Relative Declination [”] − Relative Declination [”] − Rotational Velocity [km/s] z=5.6 -1.5 240 -1.5 z=6.6 240-200 -1.5 240 − − − 50 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 1.5-2 1.0 0.5 0.0 -0.5 -1.0 -1.5 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 320 -2 -1 0 1 2320 320 0 Relative Right Ascension [”] − Relative Right AscensionR.A. [”] [”] − Relative Right Ascension [”] − 01234 Radial Distance [kpc] Jones et al., 2017 Matthee et al., 2017 Figure 7. [Cii]velocitymap(ata22 22 kpc scale) in Figure 8. IR continuum map at 230-250 GHz centered on ⇥ the rest-frame of clump A, based on the first moment map the position of CR7. The black contours show the 2, 3 What fraction of the 1 1 collapsed for frequencies with 614 to +96 km s with re- level, where 1 =7µJy beam .WealsoshowHST rest- spect to the Ly↵ redshift (see Fig. 1 for the corresponding frame UV (F814W+F110W+F160W) contours at the 2, 3, galaxy population[Cii] flux map). is Contours show the 3, 4 and 5 threshold 4 levels to highlight the positions of known (foreground) and velocity maps are shown for > 3 detections. The map sources. Sources are annotated with their photometric red- chaotic vs. settled?is driven by the the strongly blue-shifted component C-2. shifts estimated by Laigle et al. (2016). No dust continuum is detected at CR7, although a 2 signal is detected around ⇡ potential clump D. Dust continuum is also clearly detected than the beam, meaning that these clumps are unre- in a foreground source at z =0.84. solved and hence have a size r1/2,[CII] < 2.2 kpc. We +0.6 measure an observed size of r1/2,[CII],obs =3.7 0.6 kpc for clump A (4 % of the measurements result in an un- similar SFRs as CR7 (e.g. Pentericci et al. 2016; Smit resolved size, meaning that clump A is resolved at 2 et al. 2017). +0.9 ⇡ significance) and r1/2,[CII],obs =4.4 0.6 kpc for clump C-2 (resolved at 3.5 significance). We deconvolve 5. IR CONTINUUM ⇡ the sizes of A and C-2 to obtain the intrinsic size with 5.1. Blind detections r = r2 2.22. Resulting sizes are listed in Ta- ,[CII] obs We combine the flux in all four spectral windows from ble 1. Dynamical masses are computed following Wang p our ALMA coverage to search for dust continuum emis- et al. (2013): sion. In the entire image, we find two detections with S/N > 3, but they are not associated with CR7. One detection is 3.500 north-east of CR7 (associated with ID 2 5 2 Mdyn/M (sin i) =1.94 10 vFWHM,[CII] r1/2,[CII], number 339509 in the catalog from Laigle et al. 2016, ⇥ ⇥ ⇥ (2) photo z =0.84 and visible in Fig. 8), while the other where Mdyn is the dynamical mass in M , i is the in- is 18.500 to the south-west (ID number 335753 in Laigle 1 clination angle, v the line-width in km s et al. 2016, photo z =3.10, not visible in the image). FWHM,[CII] and r1/2,[CII] the size in kpc (half-light radius). This re- The positions of these foreground galaxies confirm the sults in dynamical masses (uncorrected for inclination) astrometric correction described in 3.2. We note that § ranging from (3.9 1.7) 1010 M for component A, we detect a tentative (3 ) line at 250.484 GHz at the ± ⇥ (2.4 1.9) 1010 M for clump C-2 and < 0.7 1010 position of ID 339509 that is identified as CO(4-3) with ± ⇥ 10 ⇥ M for < 0.4 10 M for clumps B and B-2, respec- ⌫0 = 461.041 GHz at z =0.841, perfectly consistent ⇥ tively. These dynamical mass estimates are lower than with its photometric redshift. typical quasar host galaxies at z 6(Wang et al. 2013), As visible in Fig. 8,thereisa 2.7 continuum ⇡ ⇡ and comparable to star-forming galaxies at z 7 with detection 200 to the south-east of CR7, nearby a faint ⇡ ⇡ Contribution of mergers vs smooth accretion At z>6 mergers and smooth accretion might contribute equally to stellar mass growth Duncan, et al., 2019 Simulation predictions for [CII] Simulations predict highly time variable morphologies, but ordered rotation is common [CII] 157.6µm [OIII] 88.33µm [OIII] 51.80µm L = 108.14L L = 106.45L L = 106.48L Pallottini, et al., 2017;2019 1kpc Katz, et al., 2019 see also Pawlik et al. 2011, Romano-Diaz et al. 2011, Feng et al. 2015 [OIV] 25.88µm [OI] 63.17µm [OI] 145.5µm L = 104.83L L = 108.83L L = 108.03L [NIII] 57.21µm [NII] 121.7µm [NII] 205.4µm L = 105.80L L = 104.80L L = 104.23L 2 log10 ⌃IR/erg/s/cm ⇣ ⌘ 7.5 6.0 4.5 3.0 1.5 The promise of ALMA for kinematics using [CII] 320 320 320 400 1.5 240 1.5 240 1.5 240 KMOS-3D:350 Hα @ z~2 eoiyRsda [km/s] Residual Velocity Wisnioski+2017 1.0 160 1.0 160 1.0 160 300 eoiy[km/s] Velocity [km/s] Velocity 0.5 80 0.5 80 0.5 80 250 0.0 0 0.0 0 0.0 0 200 HZ10 -0.5 80 -0.5 80 -0.5 80 150 − − − -1.0 160 -1.0 160 -1.0 160 100 Relative Declination [”] − Relative Declination [”] − Relative Declination [”] − Rotational Velocity [km/s] -1.5 240 -1.5 240 -1.5 240 − − − 50 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 320 320 320 0 Relative Right Ascension [”] − Relative Right Ascension [”] − Relative Right Ascension [”] − z=1 z=201234z=3 z=5 z=7 Radial Distance [kpc] lookback time 6 Gyr 3 Gyr 2 Gyr 1.2 Gyr 800 Myr 2 2 -1 Harrison+2017 2 -1 100 80 C-HiZ_z1_195 Hα intensity vel. (km s ) (km s ) Turner+2017 RT+ O σ ) obs ) -1 1 -1 1 1 1 50 60 0 0 0 0 40 0 (km s arcsec -1 -1 -1 obs vel. (km s -1 Q1 σ 20 -95 0 95 0 40 81 -50 ID:13 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 KROSS: H α @ z~1-1 2 KDS: [OIII]-1 @ z~3.5 U-zvipe_z1_1071 Hα intensity vel. (km s ) σ (km s ) 120 DN O ) obs ) -1 1 1 1 1 -1 50 100 80 0 0 0 0 0 (km s 60 arcsec -1 -1 -1 -1 obs 40 vel. (km s Q2 σ -77 0 77 0 76 152 -50 20 -2 ID:669 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 C-zcos_z1_652 Hα intensity vel. (km s ) (km s ) 40 DN M σ ) obs ) 50 -1 1 1 1 1 -1 30 40 20 30 0 0 0 0 10 (km s arcsec 0 20 -1 -1 -1 -1 obs vel. (km s Q1 σ -40 0 40 0 31 62 -10 10 -2 ID:146 -2 -2 -2 -20 0 -1 0 1 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 -1 2 -1 E-zmus_z1_119 Hα intensity vel. (km s ) (km s ) 200 RT+ M σ ) obs ) 150 -1 1 1 1 1 -1 100 100 0 0 0 0 0 (km s arcsec -1 -1 -1 obs 50 vel. (km s -1 Q1 σ -200 0 200 0 78 156 -100 ID:183 -2 -2 -2 0 -1 0 1 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 200 E-zmus_z1_12 Hα intensity vel. (km s ) σ (km s ) 150 RT+ M ) obs ) -1 1 1 1 1 -1 100 100 0 0 0 0 0 (km s arcsec -100 -1 -1 -1 -1 obs 50 vel. (km s Q1 -202 0 202 0 68 135 σ -200 -2 ID:184 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 E-zmvvd_z1_67 Hα intensity vel. (km s ) (km s ) 100 RT+ M σ ) obs ) 100 -1 1 1 1 1 -1 50 80 0 60 0 0 0 0 -50 (km s arcsec 40 -1 -1 -1 -1 obs vel. (km s Q1 -100 σ -141 0 141 0 50 100 20 -2 ID:316 -2 -2 -2 -150 0 -1 0 1 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 0 10 -10 0 10 2 2 2 -1 2 -1 80 S-CFHIZELS- Hα intensity vel. (km s ) (km s ) RT M σ ) SM14-164290 obs ) -1 1 1 1 1 -1 50 60 0 0 0 0 0 40 (km s arcsec -1 -1 -1 obs 20 -1 vel. (km s Q3 -63 0 63 0 43 85 -50 σ -2 ID:337 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 -5 0 5 10 -10 -5 0 5 10 2 2 2 -1 2 -1 S-CFHIZELS- Hα intensity vel. (km s ) (km s ) 100 100 RT+ M σ ) SM14-85797 obs ) -1 1 1 1 1 -1 50 80 0 0 0 0 0 60 (km s arcsec 40 -1 -1 -1 -50 obs -1 vel. (km s Q1 -151 0 151 0 50 100 σ 20 -100 -2 ID:359 -2 -2 -2 0 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -2 -1 0 1 2 -10 0 10 -10 0 10 arcsec arcsec arcsec arcsec r (kpc) r (kpc) Highly ionised gas from spectroscopy High-EW [OIII] emitters • Given the measurements of high-EW ionisation lines from Spitzer we might also expect fainter lines in the rest-frame UV Smit et al., 2014; 2015, Roberts-Borsani et al. 2016 The origin of ionising photons AGN Feltre et al., 2016 metal-rich stars metal-poor stars The origin of ionising photons AGN Feltre et al., 2016 Expect CIII] 1907,1909Å The origin of ionising photons AGN Feltre et al., 2016 Expect [OIII] 1661,1666,5007Å and 88μm The origin of ionising photons AGN Feltre et al., 2016 Expect CIV 1548,1550Å The origin of ionising photons AGN Feltre et al., 2016 Expect HeII 1640Å The origin of ionising photons AGN Feltre et al., 2016 Expect NV 1238,1243Å High ionisation lines found at z~6-8 CIII] @ z=7.73 CIV @ z=7.05 2.0 EGS−zs8−1 0.8 ) Lyα [CIII] CIII] ) 1 1 − zLyα=7.733 − Å Å 0.6 1 1.5 1 1.0 − 1.5 − ) ) 1 s 1 s − 2 − CIV 1548 0.8 OIII] 1660? 2 − 0.4 Å − Å 1.0 1 1 − − 1.0 0.6 s s 2 2 − 0.2 − 0.5 0.4 erg cm erg cm 18 0.5 0.2 − 18 0.0 − erg cm 0.0 erg cm 18 18 − 0.0 − (10 λ (10 −0.2 λ F 0.0 (10 −0.5 (10 −0.2 F F −0.4 F −0.4 −1.0 −0.5 1.055 1.060 1.065 1.070 1.650 1.655 1.660 1.665 1.670 1.675 1540 1545 1550 1555 1655 1660 1665 1670 Observed Wavelength (µm) Observed Wavelength (µm) Rest Wavelength (Å) Rest Wavelength (Å) Stark et al. 2015; 2017 see also Shibuya et al., 2017; Zabl et al., 2015 1184 R. Mainali et al. Downloaded from https://academic.oup.com/mnras/article-abstract/479/1/1180/5042954 by Fac.Saude Publica-USP user on 30 July 2019 High ionisation lines found at z~6-8 NV @ z=8.68 Figure 1. Keck/MOSFIREMainali et al. 2D 2018 and 1D J-band spectrum of EGSY8p7 similar to that originally published in Zitrin et al. (2015). Top: the 2D S/N map (smoothed and unsmoothed) showing the N Vλ1243 detection where positive fluxes are denoted by black. The red circle shows positive peak of the detection at the same spatial position as expected from Lyα emission, while yellow circles denote negative peaks as expected per the dither sequence. The red dotted circle denote the tentative positive flux from the N Vλ1238 component, while yellow dotted circles denote the location of negative peaks as per dither sequence. Middle: similar figure as the top panel showing the 2D spectrum. Bottom: 1D spectrum showing the Lyα line along with the N Vλ1243 and tentative N Vλ1238 emission features. The black curve denotes the extracted 1D flux whereas the grey region indicates 1σ noise level. The smoothed (2-pixel) flux is shown in blue curve. Figure 2. MOSFIRE 2D spectrum (top) and 1D spectrum (bottom) of EGSY8p7 showing the spectral region around expected location of C IV (left), He II (middle), and O III] (right). The black curve denotes the extracted 1D flux, whereas the grey region indicates 1σ noise level. The dotted black lines represent the spectral window where we expect the relevant lines to fall. See Section 3.1 for details. The odds of finding a 4.6σ feature at the spatial position of 16 pixel box surrounding the putative N Vλ1243 detection. We find 1 6 Lyα and within the narrow 500 km s− (16 pixel) spectral window features with S/N in excess of 4.6 in only 32 of the 10 realizations, defined above are exceedingly low. We can test this by generating implying a very low probability (0.003 per cent) that the line is not a large number (106) of realizations of the error spectrum in the real (Fig. 3). We further investigate the likelihood of the detection MNRAS 479, 1180–1193 (2018) Classic BPT Rest-frame optical lines have well-studied line ratios to discriminate between AGN and star formation Baldwin, Phillips & Terlevich 6 PhotoionisationMainali modelling et al. • New development of line ratio diagnostics in the rest-frame UV can (b) replace the BPT diagnostics to differentiate between AGN & star-formation • Most z>6 galaxies with deep rest-frame UV (a) spectroscopy indicate (b) likely SF origin of photons Figure 4. (Left:) Comparison of UV line ratios associated with metal poor CIV emitters narrow line AGN at z 2-4. The filled red circle shows the line ratios of RXC J2248-ID3 if we adopt the empirically-motivated line ratio (CIV 1548/CIV 1550=1);⇠ the open red circle corresponds to an upper bound on the total CIV 1548,1550 flux adopted using the WFC3/IR grism measurement. The metal poor star forming systems are mostly separated from the AGN samples, suggesting they are subjectFeltre toet al. a softer2016; radiationMainali et al. field. 2017 (Right:) Comparison to photoionization models of Feltre et al. (2016). Grey(green) points correspond to flux ratios predicted from the AGN(stellar) photoionization models in Feltre et al. (2016). 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P. 2013, ApJ, 777, 67 REFERENCES The spatial distribution of CIV lines with lensing z=5 ~2 kpc MUSE SINFONI Smit et al., 2017 The origin of ionising photons • BPASS models including binary rotation needed for high CIV EW • Young ages and low metallicity stellar population (<5% solar) ALMA observations of highly ionised lines [OIII]/[CII] traces the volume filling factor of (highly) ionised gas Figure 3: Comparisons of SXDF-NB1006-2 and other galaxies detected inthe[OIII] line. The horizontal axis represents the oxygen abundance relative to the Sun on a logarithmic scale: [O/H] = log10(nO/nH) − log10(nO/nH)⊙,wherenO and nH are the number density of oxygen and hydrogen atoms, respectively, and the solar abundance is assumed to be 12 + log10(nO/nH)⊙ =8.69 (30). Circles with error bars represent data of nearby dwarf galaxies (9–11); inverted triangles with error bars are averages of nearby spiral galaxies (13). The arrows at the right-side axis show luminosity ratios of dusty galax ies at z ∼ 3 to 4 whose oxygen abundances have not yet been measured (10, 14, 15Inoue). Data et al., from 2016 SXDF-NB1006-2 are shown Figure 1: [O III]88µmandLyα emissionas five-pointed images and spectra stars of with SXDF-NB1006-2. error bars.(A ()A)The[OIII]/far ultraviolet (FUV) luminosity ratio. The ALMA [O III]88µmimage(contours)overlaidontheSubarunarrow-bandLyThe FUV luminosity is νLν at aboutα image 1500 Ainthesourcerest-frame.(˚ B)The[OIII]/total (offsets from the position listed in Tableinfrared 1). Contours (IR) are luminosity drawn at (−2, 2, ratio. 3, 4, 5) The×σ,where IR wavelength range is 8 to 1000 µminthesourcerest- σ =0.0636 Jy beam−1 km s−1.Negativecontoursareshownbythedottedline.Theellipse at lower left represents the synthesizedframe. beam size Because of ALMA. the (B)TheALMA[O IR continuumIII]88 ofµ SXDF-NB1006-2m is not detected, we show a 3σ lower spectrum with resolution of 20 km s−1 atlimit the intensity with a peak dust position temperature shown against of the 40 relative K and an emissivity index of1.5.(C)The[OIII]/[C II] velocity with respect to the redshift z =7.2120 (blue dashed line). The best-fit Gaussian profile luminosity ratio. Because the [C II]158µmlineofSXDF-NB1006-2isnotdetected,weshow for the [O III]lineisoverlaid.TheRMSnoiselevelisshownbythedottedline. (C)The Lyα spectrum (17)shownasafunctionoftherelativevelocitycomparedtothea 3σ lower limit. [O III]88µm line. The flux density is normalized by a unit of 10−18 erg s−1 cm−2 A˚ −1.Theskylevelonan arbitrary scale is shown by the dotted line. The velocity intervals where Earth’s atmospheric lines severely contaminate the spectrum are flagged (hatchedboxes).TheLyα line shows a 15 velocity shift ∆v ≈ +110 km s−1 relative to the [O III]line(reddashedline). 13 OIII emission linked to UV bright star-formation? OIII CII z=7 Spectroscopic line record with ALMA ALMA showing it’s real potential: [OIII] at z=9.11!! Hashimoto et al., 2018 Summary • Ly⍺ is now found deep in the Epoch of Reionisation - potentially emerging from ionised bubbles • ALMA is starting to take over as the main way of obtaining spectroscopic confirmations • Bright and extended [CII] emitters are now found in the Epoch of Reionisation - kinematics of these galaxies could suggest turbulent rotating systems 800 million years after the Big Bang • Detection of high-ionisation lines indicate a hard radiation field in the highest redshift galaxies - star-formation is a likely origin, but some evidence for AGN too!