Comparison of star-formation rates for the deep field Extended Groth Strip and its Dusty Star Forming Galaxies population by Luisa Fernanda Cardona Torres Thesis submitted in partial fullfillment of the requirements for the degree of MASTER OF SCIENCE IN ASTROPHYSICS at the Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ September 2019 Tonantzintla, Puebla Advised by: PhD. Itziar Aretxaga Tenured Researcher - INAOE PhD. Alfredo Montana˜ Conacyt Fellow - INAOE c INAOE 2019

The author hereby grants to INAOE permission to reproduce and to distribute publicly paper and electronic copies of this thesis document in whole or in part

Abstract

This masters thesis presents the study of the star formation rates (SFR) of submil- limeter galaxies (SMGs) in the deep field Extended Groth Strip (EGS). We used the SFRs reported in the CANDELS and SCUBA-2 Cosmology Legacy Survey (SCLS2) catalogues, derived from UV/optical, NIR and submillimeter measurements. We per- formed the selection of the star-forming galaxies in EGS from the CANDELS cata- logue. With this sample we adjusted the star formation main sequence to the star- forming population of EGS for redshift bins (0.5 < z < 6). Our fit best agrees with the fit by Speagle, et al. (2014) and the high-mass end of the fit by Whitaker, et al. (2014). However, the exact location of the star formation main sequence is still uncertain. Then we compared the estimations of the SFRs from both catalogues for the population of SMGs with counterparts identified in the optical and near infrared bands. The total SFRUV+IR reported in the CANDELS catalogue is derived from measurements in the UV/optical bands and is corrected for dust extinction with ob- servations at 24 µm and the SFRIR is derived from the submillimeter observations of SCLS2 at 450 and 850 µm. When comparing both estimations we found that in most cases SFRUV+IR underestimates the total SFR of the SMGs. Nonetheless, 86% of the SMGs lie within the 3σ region of our star formation main sequence fit, where 4% of the sample can be classified as starbursts as they are located above the 3σ region of the fit. We performed follow-up spectroscopic observations of some SMGs at the GTC-MOS Osiris instrument. We were able to identify emission lines in the spectra and propose candidate spectroscopic redshift when possible. However, we were unable to measure the flux of emission lines that trace the star formation activity. Finally, we propose the future work to be developed in a doctorate program.

[i] ii Abstract

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ Resumen

Esta tesis de maestr´ıa presenta el estudio de las tasas de formaci´onestelar (SFR) de la poblaci´onde galaxias submilim´etricasen el campo profundo Extended Groth Strip. Se emplearon las SFR reportadas en los cat´alogosCANDELS y SCUBA-2 Cos- mology Legacy Survey (SCLS2), las cuales han sido estimadas a partir de medidas realizadas en el UV/´optico, cercano y mediano infrarojo y sub-milim´etrico.Se re- aliz´ola selecci´onde las galaxias con formaci´onestelar en el campo EGS del cat´alogo CANDELS, observadas en el UV/´optico.Con esta muestra se realiz´oel ajuste de la secuencia principal de formaci´onestelar a esta poblaci´onde EGS, para corrimientos al rojo entre 0.5 y 6. Nuestro ajuste concuerda mejor con el ajuste presentado por Speagle, et al. (2014) y con el ajuste a altas masas de Whitaker, et al. (2014). Sin embargo, la ubicaci´onexacta de la secuencia principal de formaci´onestelar a´unes incierta. Entonces comparamos las estimaciones de SFRs de ambos cat´alogospara la poblaci´onde galaxias submilim´etricascon contrapartes identificadas en las bandas

´opticasy del cercano infrarojo. La tasa de formaci´ontotal SFRUV+IR, reportada en el cat´alogoCANDELS, est´aderivada de mediciones en el UV/´opticoy corregida por la extinci´onde polvo con observaciones a 24 µm y la SFRIR proveniente de las observa- ciones submilim´etricasde SCLS2 a 450 y 850 µm. Al comparar las dos estimaciones encontramos que en la mayor´ıade los casos la SFRUV+IR subestima la SFR total de las galaxias submlim´etricas.A pesar de esto, 86% de las SMGs yacen dentro de la region de 3σ de nuestro ajuste de la secuencia principal de formaci´onestelar, donde 4% de la muestra de SMGs pueden ser clasificadas como galaxias starbursts ya que se encuentran ubicadas sobre la regi´onde 3σ del ajuste. Finalmente, realizamos un seguimiento espectrosc´opicode algunas SMGs con el GTC/MOS Osiris, en los cuales identificamos l´ıneasde emisi´on,proponiendo un corrimiento al rojo para los que fue

[iii] iv Resumen posible. Sin embargo, no logramos medir el flujo de l´ıneasde emisi´onque trazaran la actividad de formaci´onestelar. Finalmente, se plantea una propuesta de trabajo futuro a desarrollar en una etapa de doctorado.

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ Contents

Abstract i

Resumen iii

1 Introduction 1 1.1 Dusty Star Forming Galaxies ...... 2 1.2 K-correction ...... 3 1.3 Star Formation Rate ...... 5 1.3.1 Star-formation main sequence ...... 7 1.4 Main goals and key questions ...... 8

2 Extended Groth Strip Data 9 2.1 Data sources ...... 9 2.1.1 AEGIS ...... 9 2.1.2 CANDELS catalogue ...... 11 2.1.3 Optical spectra ...... 11 2.1.4 Submillimeter data ...... 12 2.2 Optical counterparts to submillimeter galaxies ...... 14 2.2.1 Derived properties of the SCLS2 galaxies ...... 17

3 Demographics of the EGS population 21 3.1 UVJ diagram ...... 23 3.2 Star Formation Main Sequence ...... 29 3.2.1 Location of Dusty Star-Forming Galaxies within the star for- mation main sequence ...... 33

[v] vi CONTENTS

4 GTC-MOS spectra 35 4.1 Phase II - planning ...... 35 4.2 Line identification and redshift report ...... 38 4.2.1 HST-galaxies ...... 39 4.2.2 Submillimeter galaxies ...... 46

5 Conclusions and future work 53

List of Figures 57

List of Tables 59

References 61

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ Chapter 1

Introduction

One of the most important goals of modern astrophysics is to understand the forma- tion and evolution of the universe and the structures it contains. In 1996 the tenta- tive detection of the Cosmic Infrared Background (CIB) by the Cosmic Background Explorer (COBE) was presented (Puget et al., 1996), which had been predicted be- forehand as the contribution of early galaxies (Partridge & Peebles, 1967). Later on, the confirmation of the CIB measurement was presented, whose integrated energy (in the 140 to 240 µm range) is 2.5 times the integrated optical/NIR light from the ∼ galaxies in the Hubble Deep Field (Hauser et al., 1998). This implies that there is a dust enshrouded population of galaxies at high redshift and that an important frac- tion of our understanding of the star formation history of the universe is obscured by dust (Dwek et al., 1998). Since then, the technological developments have permitted the growth of a new kind of astronomical observations at submillimeter wavelengths, where the dust enshrouded population of the universe and its contribution to the CIB has been under study (Smail et al., 1997; Hughes et al., 1998; Perera et al., 2008; Hatsukade et al., 2011; Scott et al., 2012; Geach et al., 2013; Zavala et al., 2017). For instance, Fujimoto et al. (2015) presented a statistical study of sources detected in the 1.2 mm band at the Atacama Large Millimeter Array/submillimeter (ALMA) +31 where the integrated flux of these sources accounted for 104−25% of the CIB found by COBE.

In this work we focus on the physical properties of star-forming galaxies that are dust enshrouded (DSFGs) within the deep field Extended Groth Strip (EGS).

[1] 2 1. Introduction

1.1 Dusty Star Forming Galaxies

Submillimeter galaxies (SMGs) are a high-z population of star-forming galaxies which contain large amounts of dust. This implies that a great extent of their UV radiation, emitted by young stars, is obscured by the dust and thermally re-emitted at longer 12 wavelengths in the Infrared (IR). They have large IR Luminosities (LIR = 10 L ), −1 which are related to high Star Formation Rates of the order SFR 300 3000M yr ≈ − (Smail et al., 1997; Hughes et al., 1998). The heated dust grains within the DSFGs emit radiation as a modified black body, and there is not a straight forward way to discern between the two main possible mechanisms that heat the dust: Active Galactic Nuclei (AGN) or young stars (Blain et al., 2002).

SMGs were discovered in the late 90’s thanks to the technological developments that allowed observations in the submillimiter range, specifically at 850 µm with the Submillimeter Common-Use Bolometer Array (SCUBA) at the 15 m James Clerk Maxwell Telescope (JCMT, i.e. Smail et al., 1997; Hughes et al., 1998; Barger et al., 1998). This marked the beginning of a new research area in astrophysics, which has been reviewed by Blain et al. (2002) and Casey et al. (2014). As a recently discovered population, there have been efforts to understand them in terms of local known ob- jects. For instance, low-z objects considered analogues to SMGs, similar in luminosity 12 (Lbol 10 L ), are the Ultra Luminous Infra-Red Galaxies (ULIRGs Blain et al., ∼ 2002), whose dust emission dominates the SED from 8 µm to 1 mm (and therefore

Lbol LIR). However, whether the SMGs are scaled up versions of ULIRGs at high ≈ redshift or not is still under debate (Casey et al., 2014).

A very important new generation survey in the study of DSFGs is the SCUBA- 2 Cosmology Legacy Survey (SCLS2, see section 2.1.4), which observed over 3000 submillimeter sources at 850 µm approaching the confusion limit (Geach et al., 2017) of the JCMT. The confusion limit happens when the noise is neither dominated by atmospheric noise nor by instrumentation noise, but instead by the blurring of faint sources caused by the resolution limitation of the telescope (Blain et al., 2002).

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 1.2 K-correction 3

There is a selection bias upon the wavelength at which DSFGs are detected in these surveys. For instance, Casey et al. (2013) report a higher peak z for the 850 µm detected galaxies than the 450 µm detected ones. Likewise, galaxies selected at shorter wavelengths (i.e. 450 µm) have higher dust temperatures, implying a warmer popula- tion (Casey et al., 2013). Zavala et al. (2014) further studied these selection effects and they showed that the variations upon the peak z for different observation wavelengths are consistent with a common parent distribution. In order to gain a more complete understanding of a population, it is common to associate sources detected at a certain wavelength with counterparts found at other wavelengths. Since single-dish submillimeter observations usually have poor resolution (θ 15 30arcsec), we resort to sources detected at higher positional certainties at ≈ − other wavelengths, like radio wavelenghts, given the known correlation between FIR and radio for starburst galaxies (Condon, 1992; Carilli & Yun, 2000), or mid-infrared 24 µm, where we look for the emission of dust at shorter wavelengths (Pope et al., 2006). This is, however, a very difficult endeavour for SMGs, where counterparts cannot be found for complete samples (Casey et al., 2013; Zavala et al., 2018).

1.2 K-correction

The distribution of the flux-density over wavelength (or frequency) emitted by an object is known as its Spectral Energy Distribution (SED). The shape of the SED depends upon the mechanisms of emission of the object. As it was mentioned in the previous section, the thermal emission of dust, which dominates the SED of DSFGs, is commonly modeled with a modified black body distribution. The flux-density at frequency ν is given by:

3 ν β 2hν 1 −( /ν ) Sν = [1 e 0 ] , (1.2.1) − c2 ehν/kT 1 − where ν0 is the frequency at which the emission becomes optically thick, β is the emissivity index, and T is the temperature of the emitting source, which in the case of DSFGs is considered to be the dust-temperature.

Determination of SFR of SMGs in the EGS 4 1. Introduction

Figure 1.1: (Left panel) Modified black body for a source with luminosity LIR = 12 1 10 L , dust-temperature Td = 42 K, emissivity index β = 1.8 and ν0 = c/100µm (Casey× et al., 2014). The SEDs are redshifted to lower ν as z increases. The vertical lines correspond to observed wavelengths: 2.1 mm (blue dash-dot line),1.1 mm (red line), 850 µm (green dashed line), 450 µm (cyan dotted line) and 70 µm (red dash- dot line). (Right panel) Flux density at the observed λ (following the same colors and symbols as in the left panel) for the same modified black body (LIR,β,ν0,Td). We can see that for λ = 70 µm there is a strong positive K-correction, while at larger λ (λ 450 µm) the effect is opposite (negative K-correction). ≥

As we observe sources with the same luminosity at higher redshifts, the SED shifts to higher wavelengths and the peak brightness decreases its intensity. It is necessary to apply the K-correction in order to estimate the emitted flux-density by the source. This effect is shown in Figure 1.1, with a modified black body SED redshifted to a set of values, and the resulting observed flux density as a function of redshift. In the left panel it can be appreciated how the peak of the SED approaches submillimeter observational wavelengths as the redshift of the source increases. In the right panel,

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 1.3 Star Formation Rate 5 which shows how the flux density of a galaxy with fixed L changes as a function of z, we can see that at λ 1 mm the flux density remains almost constant (or even ∼ increases) at z 1 10. This aids the observation of this type of galaxies up to high ≈ − redshifts at wavelengths higher than λ > 250 µm (Blain et al., 2002). The observed flux density can be estimated through the equation (Casey et al., 2014):

L (1 + z) S S = IR ν , (1.2.2) ν,obs 4πD2 R 1000µm L 8µm Sν(Td)dν where DL is the luminosity distance, Sν is the source emitted flux density at rest-frame R 1000µm frequency ν, LIR the galaxy infrared luminosity, z is the redshift, and 8µm Sν(Td)dν is the modified black body emission integrated over the 8 µm 1 mm wavelength range. − Given that in the case of DSFGs, detected at submillimeter wavelengths, the effect of the K-correction is applied to decrease the observed flux-density to estimate the rest-frame flux density, then it is known as negative K-correction.

1.3 Star Formation Rate

The Star Formation Rate (SFR) is a measurement of the rate at which stars are born in a galaxy, or a particular region within it, and how they transform gas into −1 stars. It is typically measured in units of solar masses per year (M yr ). There are several calibrated methods to estimate the SFR, according to tracers associated with young stellar populations at different wavelengths. Some of the most used methods presented in Kennicutt (1998) are the following:

SFR derived from the UV luminosity: •

−1 −28 −1 −1 SFRUV(M yr ) = 1.4 10 LUV(erg s Hz ) (1.3.1) ×

SFR derived from recombination lines like Hα: •

−1 −42 −1 SFRHα(M yr ) = 7.9 10 L(Hα)(erg s ) (1.3.2) ×

Determination of SFR of SMGs in the EGS 6 1. Introduction

SFR derived from forbidden lines like [OII]: •

−1 −41 −1 SFR[OII](M yr ) = 1.4 10 L[OII](erg s ) (1.3.3) ×

SFR derived from the IR luminosity: •

−1 −44 −1 SFRIR(M yr ) = 4.5 10 LIR(erg s ) (1.3.4) ×

These relations may vary according to the initial mass function (IMF) considered by the author. The most frequently used IMFs are those by Salpeter (1955), Kroupa (2001) and Chabrier (2003). Kennicutt (1998) used the Salpeter IMF for equations 1.3.1 - 1.3.4. If, instead of the Salpeter IMF, a Chabrier IMF (2003) is employed, then the SFRIR is lower by a 1.8 factor (Casey et al., 2014).

Figure 1.2: SED fitting of the observational flux-densities for an example galaxy (irac131161) at redshift z 1. The SCLS2 450 µm and 850 µm fluxes would lie in the rightmost region of the∼ SED, where there is an extrapolation in the fit. Image from Barro et al. (2011a).

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 1.3 Star Formation Rate 7

UV-based determinations are affected by dust extinction, which is often difficult to determine. The estimation of IR-based SFRs is also affected by different assumptions. For example, the SED templates used to fit the fluxes of high-z galaxies are adopted local low-z analogues (Barro et al., 2011a). There could also be some radiation con- tribution from obscured AGNs, which can heat the dust, but would not be related to the star-forming mechanisms (Casey et al., 2014). Furthermore, for the IR derived luminosity, few galaxies have deep data beyond 70 µm (e.g. from Spitzer/MIPS Barro et al., 2011a). This affects the calculations of SFR as there are not enough data points to correctly constrain the full IR-SED. Hence, the LIR and SFRIR determinations can be affected by the indetermination of the SED fit and the assumption of a single T throughout the galaxy. As it was mentioned previously, SMGs are bright in the sub- millimeter range and, therefore, in principle they can provide more data points to fit the SED and achieve more accurate IR-based luminosities and star-formation rates.

1.3.1 Star-formation main sequence

The star-formation main sequence is a correlation between the stellar mass (M?) and the star-formation rate (SFR) shown by the majority of star-forming galaxies. The concept was first introduced by Noeske et al. (2007) for optically selected galaxies that had SFRHα and later on expanded by Daddi et al. (2007) for 24 µm selected galaxies. There have been several works that fitted a star-formation main sequence: 64 of those fits were studied by Speagle et al. (2014) for a comprehensive relation that holds up to z = 6. Before the work by Speagle et al. (2014) there were no quantitative comparisons and, given that each work uses different calibrations and methods (e.g. IMFs, Stellar Population Synthesis models, extinction curves), they converted the necesary parameters and derived a time and stellar mass dependent equation. There are still contradictory results. For instance, Whitaker et al. (2014) studied the low-mass slope of the star-formation main sequence for the redshift range 0.5 < z < 2.5. They considered the deep photometry and grism spectra from CANDELS and 3D-HST and three methods for estimating the SFR: SFRUV+IR, β-dust corrected

UV SFR and Hα SFR. On the other hand Koprowski et al. (2016) present the main sequence for galaxies detected in the 850 µm SCLS2, in the high-mass end of the main sequence. Koprowski et al. (2016) discuss the various main sequence fits and

Determination of SFR of SMGs in the EGS 8 1. Introduction

how the FIR/sub-millimeter selected samples yield different relations to the optically

selected fits, where some find a decline in the slope for masses above logM?/M 10.5 ≈ (Whitaker et al., 2014), while others find no differences (Schreiber et al., 2015). They emphasize on the main sequence relation depending upon the sample selection, and the need of the SED fitting to encompass optical-IR data in order to estimate the SFR. Even though the star-formation main sequence is still a subject to debate it is used as a new definition of starburst galaxies. A starburst galaxy is now defined as those with elevated sSFR= SFR , when compared to the main sequence (e.g. Casey M? et al., 2014). In their 2014 review on DSFGs Casey et al. showed that it was still uncertain where the Dusty Star-Forming Galaxy population lies in relation to the main sequence, which depends upon the method and uncertainties related to the estimation of SFR and M?. Furthermore, it is unkown which would be the impact of mergers to the mass build-up of SMGs (Casey et al., 2014).

1.4 Main goals and key questions

The main goal of this thesis is to compare the SFR measurements derived from ob- servations at UV/optical and submillimeter bands. We will work with data from the CANDELS and SCLS2 catalogues for the Extended Groth Strip field. We aim to explore the demographic properties of the galaxies reported in the optical catalogue CANDELS selecting the star-forming and quiescent galaxies using a color-color dia- gram. Besides, we would like to examine how DSFGs with identified counterparts in the CANDELS and IRAC catalogues relate to the rest of the population in this field according to the derived SFR and stellar mass (M?). Throughout this work we adopted a flat ΛCDM cosmology with the following −1 −1 parameters: H0 = 67 km s Mpc , Ωm = 0.32.

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ Chapter 2 Extended Groth Strip Data

The Extended Groth Strip (EGS) field is a region between the constellations Ursae Major and Bootes, located at α = 14h19m00s and δ = +52o4800000 and it is 70 10 × square arcminutes in size. It was first observed by the Hubble Space Telescope (HST ) with the Wide Field Planetary Camera 2 (WFPC1) between March and April 1994 and named after the phycisist Edward Groth (Rhodes, 1999). He was associated with the HST and worked there as data and operations team leader, where he was P.I. for the Wide Field Camera (WFC) instrument. It is one of the most studied fields, along with: GOODS-N, GOODS-S, UDS and COSMOS (e.g. Koekemoer et al., 2011)

2.1 Data sources

The EGS field has had a large multi-wavelength coverage from several instruments and surveys. For instance, the 3D-HST, AEGIS, CANDELS and IRAC surveys include this deep field. Their data is available in the Rainbow Navigator, presented by Barro et al. (2011b) 1.

2.1.1 AEGIS

The All-wavelength Extended Groth Strip International Survey (AEGIS) is a multi- wavelength program whose goal is to understand how galaxies and large-scale struc- tures form and evolve from early times into the universe we see around us (Davis et al., 2007). The instruments involved in this survey range from those used at radio

1Rainbow Navigator (P´erez- Gonzalez and Barro): https://rainbowx.fis.ucm.es/Rainbow˙navigator˙public/

[9] 10 2. Extended Groth Strip Data

wavelengths (VLA at 6 and 20 cm) to X-Rays (Chandra/ Advanced CCD Imaging Spectrometer (ACIS) at 4 and 1 keV). It also covers the UV, NIR and IR spectral re- gions with the following telescopes: Galaxy Evolution Explorer (GALEX), HST in the V (F606W), I (F814W), J (F110W) and H (F160W) bands, Keck Telescope, Canada- France-Hawaii Legacy Survey, Palomar/ Wide-Field Infrared Camera, Spitzer/ In- frared Array Camera (IRAC) for the Mid-Infrared range (at 3.6, 4.5, 5.8 and 8 µm) and the Spitzer/ Multiband Imaging Photometer (MIPS) for the far-IR observations (at 24, 70 and 160 µm). The resulting data is presented as images, spectra and derived data products in their web page2. However, each instrument had a different coverage of the EGS field. Therefore, there are some areas where the surveys do not overlap, as can be seen in Figure 2.1.

Figure 2.1: AEGIS coverage map of the Extended Groth Strip. In both panels the background gray-scale image shows the HST /ACS mosaic composed image. (Left panel) CFH12K (pink), WIRC from Palomar (red), Keck spectroscopic observations with DEIMOS as part of the DEEP2 collaboration (black), CFHTLS MegaCam (blue). (Right panel) VLA at 20 cm(red), VLA at 6 cm(pink), Spitzer/IRAC (green), Chandra (blue), GALEX (black). In both panels the cyan region corresponds to the Mini Test Region and the yellow line marks 30 arcmin along the length of the field. Image taken from Davis et al. (2007).

2Official web-page of the AEGIS catalogue http://morta.ucolick.org/aegis/v

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 2.1 Data sources 11

2.1.2 CANDELS catalogue

The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) is an HST survey program that covered 800 arcmin2 over five deep fields (Koekemoer et al., 2011; Grogin et al., 2011). The program was designed to observe up to two depths: the CANDELS/Deep survey (limited at H=27.7 mag) and CANDELS/Wide survey (limited at H=27 mag). The WFC3 and ACS cameras on board the HST acquired deep images during 902 orbits between 2010 and 2013. The project was led by Sandra Faber (U. of California, Santa Cruz) and Henry Ferguson (Space Telescope Science Institute). The five deep fields observed within this project were:

CANDELS/Deep survey: CANDELS/Wide survey:

GOODS-N (Great Observatories UDS (Ultra Deep Survey) • • Origins Deep Survey - North) COSMOS (Cosmic Evolution Sur- • vey) GOODS-S (Great Observatories • Origins Deep Survey - South) EGS (Extended Groth Strip) • The CANDELS survey has an extensive database for these observed deep fields. Several sub teams within CANDELS estimated redshifts and other physical parame- ters through various methods, presented and evaluated by Mobasher et al. (2015) and Santini et al. (2015). There have also been demographic studies for the GOODS-S and the UDS fields by Fang et al. (2018). The CANDELS catalogue for the EGS field was presented by Stefanon et al. (2017).

2.1.3 Optical spectra

Within the work in this thesis we present new optical spectra obtained with the 10 m Gran Telescopio de Canarias (GTC) Multi-Object Spectrograph (MOS) for the obser- vation proposal GTC-AMEX19 (PI: Aretxaga). We observed, among other objects, 3 submilimeter galaxies selected from the SCLS2 sample, with optical counterparts presented by Zavala et al. (2017) (section 2.2). Additionally, we observed 4 galaxies selected from the 3D-HST catalogue. In chapter 4 we present the planning, reduction, extracted spectra and line identification of these observations.

Determination of SFR of SMGs in the EGS 12 2. Extended Groth Strip Data

2.1.4 Submillimeter data

2.1.4.1 SCUBA-2 Cosmology Legacy Survey

Our submillimeter sample of Dusty Star-Forming Galaxies (DSFGs) are selected from data acquired with the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) at the James Clerk Maxwell Telescope in 2014, as part of the SCUBA-2 Cosmology Legacy Survey (SCLS2 Geach et al., 2013, 2017). The catalogue presents observations at 450 µm and 850 µm, with depths of σ450 µm 1.9 mJy and σ850 µm 0.46 mJy ≈ ≈ (Zavala et al., 2017). The coverage of the map is 70 arcmin2 with angular FWHM ∼ of θ450 µm 7.5 arcsec and θ850 µm 14.5 arcsec. The sources for a robust sample ≈ ≈ were selected as the peak values from the S/N map, taking into account S/N> 3.5. Considering this threshold, the catalogue has 57 sources at 450 µm and 90 at 850 µm and it is displayed in Figure 2.2 over the corresponding S/N maps at each wavelength.

Figure 2.2: The SCLS2 450 µm (left panel) and 850 µm (right panel) S/N maps of the Extended Groth Strip with detected sources marked with white squares. Image taken from Zavala et al. (2017).

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 2.1 Data sources 13

2.1.4.2 AzTEC map

There is also an EGS 1.1 mm map acquired with the AzTEC instrument at the Large Millimeter Telescope Alfonso Serrano (LMT). It is centered at α = 214.9420396o, δ = 52.87861111o and has a 91.2 arcmin2 area. The data was acquired in May 2013 and observed over 11 hours, when the LMT was operating in its 32 m configura- tion (θ1.1mm 8.5 arcsec). Figure 2.3 shows the catalogue of SCLS2 sources over ∼ the AzTEC S/N map, where the brightest source at 850 µm (S/N=24.2) appears with S/N=6.6 at 1.1 mm. As it can be seen, the depth of the 1.1 mm map is low

(S1.1 mm 0.5 mJy). There will be a new instrument, named TOLTEC, to be in- ∼ stalled at the LMT in late 2019. It is designed to observe at 1.1, 1.4 and 2.0 mm in the 50 m configuration of the LMT. One of the main projects for this instrument is the observation of deep fields as part of its legacy programs, where the confusion limit for the 1.1 mm band will be reached (S1.1 mm 0.025 mJy). ∼

34 35 72 50 43 60 5479 27 80 68 43 4022 48 1446 1721 3470 64 36 13 93 7 2023 55 254 129 51 136 52 62 89 158 49 4226 21 81 74 2738 50 48 56 28 2631 67 44 57 53 82 63 57 23 30244 88 4469126 23 3010 159 32 4931 78 207 75 77 6518 2529 53 35 18 47 71 8533 36 37 4039 4116 421711 28 58 221 2459 47 54 2921 94 5273 1410 91 61 32 51 5616 194638 33 3911 83 37 53 92 45 58 90 66 45 55

-2.9 -2.2 -1.6 -0.88 -0.21 0.47 1.1 1.8 2.5 3.1 3.8 Figure 2.3: The 1.1 mm S/N map of the EGS field observed by AzTEC at the 32 m LMT. This region closely matches the SCLS2 coverage area described in 2.1.4. The 850 µm detected sources are marked in red and the 450 µm detected sources are marked in blue.

Determination of SFR of SMGs in the EGS 14 2. Extended Groth Strip Data

2.2 Optical counterparts to submillimeter galaxies

Once the SCLS2 sources were detected, they were associated with optical counter- parts using the panchromatic data available for this field (Zavala et al., 2018). The counterparts were found using: radio VLA at 20 cm, which traces recent star forma- tion via synchrotron emission (Carilli & Yun, 2000); observations at 24 µm, as they are sensitive to warm dust emission; and 8 µm data as a tracer of the older and mass- dominant stellar population. Counterparts were found within a search radius 2.5 times the positional uncertainty of each galaxy. They found 71 counterparts. Out of the 71 identified counterparts, 58 lie within the footprint of CANDELS. The remaining 13 galaxies that fall outside the HST /CANDELS coverage, were associated to sources from the IRAC catalogue presented by Barro et al. (2011b). In Table 2.1 we present the ID and coordinates for the optical counterparts. From now on, we will work with this sample of DSFGs with identified counterparts. They have reported Stellar-Mass and SFR values estimated by various teams in the CANDELS catalogue.

Table 2.1: Optical counterparts for the SCLS2 sources. The optical counterpart coor- dinates are those of CANDELS (Stefanon et al., 2017) or IRAC (Barro et al., 2011b) catalogues. Column 1: name in the SCLS2 catalogue at 850 µm. Column 2: identifi- cation in the SCLS2 catalogue at 450 µm. Column 3: identification in the CANDELS catalogue with HST observation. Column 4: identification in the IRAC catalogue. Column 5: right-ascension of the optical/IR counterparts. Column 6: Declination of the optical/IR counterparts.

ID850 µm ID450 µm IDHST IDIRAC RAopt DECopt 850.001 450.02 21335 - 214.910882 52.900925 850.002 450.03 16498 - 214.914447 52.875959 850.003 450.05 18656 - 214.916415 52.891337 850.004 450.25 17920 - 214.946689 52.910020 850.005 450.08 - 122794 214.978122 52.811542 850.006 450.13 13658 - 214.974134 52.905954 850.007 450.20 8156 - 214.962443 52.870324 850.008 450.15 8265 - 215.014456 52.901214 850.009 450.12 - 123412 214.843676 52.910939 Continued on next page

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 2.2 Optical counterparts to submillimeter galaxies 15

Table 2.1 – continued from previous page

ID850 µm ID450 µm IDHST IDIRAC RAopt DECopt 850.010 450.14 8340 - 214.919736 52.839658 850.011 450.39 4919 - 214.922389 52.821939 850.012 450.06 12475 - 214.946125 52.876173 850.014 450.46 - 121876 1 214.8562017 52.9287205 850.015 450.09 12874 - 214.938204 52.874313 850.016 450.56 - 120588 215.007724 52.827103 850.017 450.11 13776 - 214.898846 52.852513 850.018 450.84 4996 - 214.974861 52.860563 850.019 450.41 24050 - 214.970982 52.957352 850.020 450.23 7994 - 215.031040 52.916459 850.021 450.17 6891 - 215.054219 52.925918 850.022 450.01 9333 - 214.927684 52.847964 850.024 450.04 16318 - 214.923237 52.882156 850.025 450.29 23205 - 214.850601 52.866404 850.028 450.69 16544 - 214.876329 52.852377 850.029 450.21 21206 - 214.835440 52.843781 850.030 450.10 21235 - 214.877974 52.876880 850.032 450.63 5729 - 214.932895 52.832951 850.037 450.64 - 117087 215.050227 52.853897 850.038 450.27 27358 - 214.864723 52.899081 850.039 450.40 - 117578 215.038863 52.854429 850.041 450.16 1368 - 214.992838 52.850766 850.042 450.26 12502 - 214.979990 52.902444 850.043 450.73 23152 - 214.950132 52.938209 850.052 450.76 - 124474 1 214.827757 52.904873 850.059 450.24 18694 - 214.855508 52.848827 850.060 450.75 - 121668 214.84949 52.938104 850.065 450.18 21212 - 214.875544 52.866459 850.069 450.44 11896 - 214.954780 52.876572 Continued on next page

Determination of SFR of SMGs in the EGS 16 2. Extended Groth Strip Data

Table 2.1 – continued from previous page

ID850 µm ID450 µm IDHST IDIRAC RAopt DECopt 850.070 450.34 18143 - 214.968421 52.925046 850.073 450.52 5375 - 214.948005 52.840633 850.078 450.82 -- 215.0377 52.8708.. 850.079 450.54 12448 - 215.029611 52.936340 850.085 450.33 - 118504 1 215.015842 52.856805 850.092 450.60 8277 - 214.885212 52.815749 850.095 450.37 - 121835 1 214.996545 52.814086 850.097 450.71 14062 - 214.920611 52.865887 850.104 450.45 - 122942 214.986563 52.80205 850.044 - 2998 - 215.034896 52.891364 850.047 - 20341 - 214.859833 52.860656 850.048 - 2838 - 215.045433 52.894592 850.050 - 17067 - 214.996769 52.94075 850.051 - 10774 - 214.995061 52.906108 850.053 - 3345 - 214.993497 52.864329 850.054 - 15371 - 214.874737 52.843773 850.056 - 4619 - 215.027303 52.894668 850.057 - 7340 - 214.996947 52.889169 850.062 - 1507 - 215.061805 52.900938 850.067 - 28663 - 214.829331 52.893962 850.072 - 14167 - 215.015852 52.939408 850.075 - 26086 - 214.834060 52.870092 850.077 - - 117273 215.029710 52.867911 850.080 - 26097 - 214.923151 52.934686 850.081 - 14924 - 214.954660 52.899053 850.082 - - 115315 215.055684 52.881997 - 450.19 6840 - 214.916970 52.827376 - 450.28 15610 - 214.945929 52.894158 - 450.35 15566 - 214.902474 52.863695 Continued on next page

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 2.2 Optical counterparts to submillimeter galaxies 17

Table 2.1 – continued from previous page

ID850 µm ID450 µm IDHST IDIRAC RAopt DECopt - 450.36 9195 - 214.936159 52.855855 - 450.42 13677 - 214.905312 52.850914 - 450.43 11923 - 215.020341 52.929760 - 450.48 27020 - 214.908677 52.927897

2.2.1 Derived properties of the SCLS2 galaxies

Zavala et al. (2017) identified the sources in the SCLS2 catalogue, detecting them at first in the S/N map and then measuring the coordinates, flux density and noise. In order to measure these quantities, they fitted to each detected source the Point Spread Function (PSF), which was estimated in the reduction procedure. This measured flux density is called raw flux density, as it does not have any boosting correction. We measured the raw flux density at the reported coordinates for each wavelength map and compared it with the raw flux density reported by Zavala et al. (2017). In Figure 2.4, we present a comparison between both reported flux densities for the 450 µm map, where we can appreciate that there is good agreement between both measured flux densities. Therefore, we will adopt the derived physical parameters estimated by Zavala et al. (2017) for our sample from the SCLS2.

2.2.1.1 Deboosted flux

When sources are detected at a low S/N, there occurs contamination from the crowd- ing of sources fainter than the detection threshold, which increases (boosts) the mea- sured flux density of the detected sources (Coppin et al., 2006). Therefore, the raw flux densities have to be deboosted before estimating physical parameters. The deboosting factor is estimated through an statistical process using Monte Carlo simulations, as described by Zavala et al. (2017). Fainter sources are more boosted than brighter ones. Considering that we have compared the raw flux densities measured directly and that they comply with a 1:1 relation (Figure 2.4), we will adopt from now on the fDeboost from Zavala et al. (2017) and use these values to estimate the infrared luminosities and star formation rates.

Determination of SFR of SMGs in the EGS 18 2. Extended Groth Strip Data

Figure 2.4: Comparison between the SCLS2 450 µm raw flux densities and fRAW measured in this work (y-axis) and those reported by Zavala et al. (2017) at map (x-axis).

2.2.1.2 Infrared Luminosity

The IR luminosity (8 1000 µm) reported by Zavala et al. (2018) was estimated by − fitting a modified black body, fixed at the redshift provided by the optical catalogues.

The modified black body that was used had an emissivity index β = 1.6 and ν0 =

c/100 µm, from equation 1.2.1. Our LIR estimation uses the same modified black body

parameters (β, ν0), the redshift reported in the catalogues for the optical counterparts,

the deboosted flux and the dust temperature (Td) as in Zavala et al. (2017, 2018). We

must point out that in Zavala et al. (2018) they fitted both the LIR and Td. Instead, we are calculating the IR-luminosity from either the 450 µm or 850 µm, assuming that the

Td is correct. The resulting LIR comparison is presented in Figure 2.5, where we can appreciate that the LIR calculated from the 850 µm flux densities are systematically located above the 1:1 relation. As the f850 µm is placed further away from the modified black body peak emission the fit is less accurate, in this case overestimating the LIR. We could safely assume this is the reason for the overestimation, given that this effect is only appreciated in the estimated LIR from 850 µm flux densities and not at 450 µm.

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 2.2 Optical counterparts to submillimeter galaxies 19

Figure 2.5: Comparison of LIR calculated in this work and Zavala et al. (2018), using the 450 µm (upper panel) and 850 µm (lower panel) deboosted flux densities and LIR by Zavala et al. (2017). We considered a modified black body with β = 1.6 and ν0 = c/100 µm, z of the optical counterparts and Td fitted by Zavala et al. (2018).

Determination of SFR of SMGs in the EGS 20 2. Extended Groth Strip Data

2.2.1.3 Infrared star-formation rate for dusty star forming galaxies

Considering the LIR, Zavala et al. (2018) estimate the SFRIR with a Kennicutt (1998) 12 relation and Chabrier (2003) initial mass function (IMF), where LIR 10 L implies −1 ∼ a SFR 100M yr . Equation 1.3.4 considers a different IMF, so it must be scaled ∼ to account for this difference with a factor 1.8. Zavala et al. (2018) use the star- ∼ forming main sequence derived by Speagle et al. (2014), and our sample of DSFG population lies mostly within the 3σ of this main sequence fit (Figure 2.6).

Figure 2.6: Distribution of the DSFGs from the SCLS2 catalogue with optical coun- terparts in the sSFR-redshift relation by Zavala et al. (2018). The continuous black line and its 3σ uncertainty region (gray-scale) are the star forming main sequence derived by Speagle et al. (2014). The black dots are the galaxies detected at both 450 µm and 850 µm, the blue rectangles are those only detected at 450 µm and the red triangles are the galaxies detected only in the 850 µm data. Image taken from Zavala et al. (2018).

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ Chapter 3

Demographics of the EGS population

The EGS CANDELS catalogue includes physical properties calculated by various teams, as presented in Mobasher et al. (2015) and Santini et al. (2015), who com- pare the results from the teams. They concluded that the results are in overall good agreement, despite the different methods and assumptions (i.e. initial mass functions (IMFs), Stellar Population Synthesis templates, SED fitting code) that each team considered. We adopt from the CANDELS catalogue the Star Formation Rate (SFR) presented by Barro et al. (2011a), which is the total SFR SFRIR+UV, according to ∼ equation 3.0.1. In order to obtain the SFRIR+UV they estimated the IR luminosities

(LIR = L[8 1000 µm]) and luminosity at 2800 A.˚ The LIR was calculated by fitting − the MIPS 24 µm fluxes to SED templates, and L2800 was obtained from the best fit of optical SED templates (Barro et al., 2017, see Figure 1.2).

−10 SFRUV+IR = 1.09 10 (LIR + 3.3L2800) (3.0.1) ×

There have been galaxy demographic studies for the other CANDELS fields, like those in UDS and GOODS-S conducted by Fang et al. (2018). Following their proce- dure, we select a sample of galaxies from the EGS catalogue, considering the criteria below:

[21] 22 3. Demographics of the EGS population

1.- Observed magnitude at the HST F160W band H < 24.5, following the rec- ommendation by van der Wel et al. (2014). The galaxy sizes can be estimated accurately if this limit is considered when fitted in GALFIT.

2.- SExtractor parameter CLASS STAR< 0.9, in order to avoid contamination of the sample by stars.

3.- As suggested by Santini et al. (2015) we excluded the sources with photometric defects, like star spikes and hot pixels, which are tagged as PhotFlag=0.

4.- Stellar masses within the range 9.0 < log (M?/M ) < 11.0.

5.- Well-constrained GALFIT measurements, where we accepted the objects with quality flag value of 0.

The only criterium we will not comply with from Fang et al. (2018) is the redshift selection (z < 2.5), as we wish to explore the redshift evolution of the demographics up to higher redshifts. In Table 3.1 we present the number of galaxies remaining in our sample after the selection criteria have been applied, and the percentage they represent from the entire catalogue. For comparison, we show as well the Fang et al. (2018) sample in UDS, GOODS-S and for both fields combined. Another difference between our study and that of Fang et al. (2018) is the adopted SFR estimation. They did not use the SED fitting results by Santini et al. (2015), instead they used the rest-frame UV (NUV: λ 2800A)˚ luminosity corrected by dust (AV from the ≈ SED fits, where ANUV = 1.8AV ) following equation 3.0.2 for a Kroupa IMF (2001).

We will identify this SFR as SFRUV,corr. They justified this selection by comparing their estimates with the ones presented by other teams in Santini et al. (2015), and concluded they had good agreement.

−1 −10 SFRUV,corr[M yr ] = 2.59 10 LNUV,corr[L ] (3.0.2) ×

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 3.1 UVJ diagram 23

Table 3.1: Number of galaxies in each field using: F160W < 24.5 mag, PhotFlag=0, Class star< 0.9, 9.0 < logM?/M < 11.0. Both the number of galaxies and percent- ages relate to the whole catalogue for the GOODS-S and UDS fields (taken from Fang et al., 2018), and for the EGS field (this work). Column 1: the selection criteria. Column 2: number of galaxies for the GOODS-S field. Column 3: number of galaxies for the UDS field. Column 4: number of galaxies for the GOODS-S and UDS fields, combined. Column 5: number of galaxies for the EGS field.

Characteristic GOODS-S UDS Combined EGS Full catalogue 34930 35932 70862 41457 (100%) (100%) (100%) (100%) z spec 2658 (6.41%) Selection criteria 4683 5810 10493 7663 (13.4%) (16.2%) (14.2%) (18.5%) Star-forming galaxies 3581 4479 8060 7137 (10.3%) (12.5%) (11.4%) (17.22%) Quiescent galaxies 447 628 1075 526 (1.3%) (1.7%) (1.5%) (1.3%)

3.1 UVJ diagram

We used a color-color rest-frame diagram for our star-forming galaxies selection, with colors U-V and V-J, which differentiates between quiescent and star-forming galaxies, even those reddened by dust (Patel et al., 2012). From now on we will refer to this diagram as UVJ diagram, where star-forming galaxies are red in V-J and quiescent galaxies are blue (Williams et al., 2009). In Figure 3.1 and 3.2 we present the UVJ diagram for the selected sample of galaxies from the CANDELS/EGS catalogue. The color of the dots represents their specific star-formation rate (log sSFR, considering the total SFR estimated by Barro et al., 2011a). The optical counterparts identified by Zavala et al. (2018) in the CANDELS catalogue are marked as downwards red triangles. Dusty star-forming galaxies (DSFGs) with only IR counterparts in the IRAC catalogue are not included, as these do not have reported U, V and J magnitudes. The black dashed line is the selection criteria used to discern between quiescent and star-forming galaxies for up to z = 2, since this is the redshift limit in Williams et al. (2009).

Determination of SFR of SMGs in the EGS 24 3. Demographics of the EGS population

logM logM 0 0 logM 0 0 logM logM

0

0

0

0

00 0

0 0

0 0 0

00

U - V - U 0 0

00 0

0 0 00

0 0

0

0

00 0 0 0 0 0

- J

Figure 3.1: UVJ rest-frame color diagram for the EGS field selected galaxies at 0 < z < 2. The color values in this Figure are uncorrected for dust extinction. We present the properties of the galaxies in the EGS field in redshift slides of ∆z = 0.5 (rows) and in stellar mass slides of ∆log M?/M = 0.5 (columns). The color gradient for the points indicates the log(sSFR) value for each galaxy. The optical counterparts of the SCLS2 sources, identified by Zavala et al. (2018) in the CANDELS catalogue, are marked as downwards red triangles. The dashed black lines define the quiescent region according to Williams et al. (2009).

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 3.1 UVJ diagram 25

logM logM 0 0 logM 0 0 logM 0 logM

0 0

0

0

00 0

0 0

0 0 0

00

U - V - U 0 0

00 0

0 0 00

0 0

0

0

00 0 0 0 0 0

- J

Figure 3.2: UVJ rest-frame color diagram uncorrected for dust extinction for the selected galaxies in the EGS field that lie beyond z > 2. Same symbols as in Figure 3.1.

Determination of SFR of SMGs in the EGS 26 3. Demographics of the EGS population

The CANDELS catalogue presents estimated extinction values AV (Santini et al., 2015), therefore, we corrected for dust attenuation the colors presented in the UVJ diagram, considering a Calzetti et al. (2000) attenuation law with AU = 1.5AV and

AJ = 0.35AV . The effect of this correction can be seen in Figure 3.3 for 0.5 < z < 1.0 and 10 < log (M?/M ) < 10.5. The UVJ diagrams corrected for dust attenuation are presented in Figures 3.4 and 3.5. Those galaxies whose colors locate them in the upper left corner of the UVJ diagram are catalogued as quiescent galaxies and those outside the region limited by the dashed line are classified as star-forming galaxies (Figure 3.4). For galaxies at z > 2, we will consider them all to be star-forming. The selected number of quiescent and star-forming galaxies are reported in Table 3.1.

UVJ diagram - dust correction

0 0 0 0

U - V - U 0 0 00

0

0 0

00 00 00 0 0 0 00 0 0 0 - J

Figure 3.3: UVJ color diagrams for 0.5 < z < 1.0 and 10 < log(M?/M ) < 10.5 that shows the effect before (left) and after (right) applying a dust correction. The symbols are the same as in Figure 3.1.

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 3.1 UVJ diagram 27

logM logM 0 0 logM 0 0 logM 0 logM

0

0

0

0

00 0

0 00

0 0 0

00 U - V - U 0 0

00 0

0 0 00

0 0

0

0

00 0 0 0 0 0

- J

Figure 3.4: UVJ rest-frame color diagram corrected for dust attenuation for the CAN- DELS/EGS galaxies at 0 < z < 2. The symbols are the same as in Figure 3.1.

Determination of SFR of SMGs in the EGS 28 3. Demographics of the EGS population

logM logM 0 0 logM 0 0 logM logM

0 0

0

0

00

0

0 0

0

0 0 00

U - V - U 0 0

00 0

0

00 0

0 0

0

0

00

0 0 0 0 0

- J

Figure 3.5: UVJ rest-frame color diagram corrected for dust attenuation for galaxies at redshifts 2 < z < 4. The symbols are the same used in Figure 3.1.

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 3.2 Star Formation Main Sequence 29

3.2 Star Formation Main Sequence

⊙ ⊙⊙ ⊙⊙

- -

- ⊙⊙ ⊙⊙ ⊙⊙

- -

- ⊙⊙ ⊙⋆⊙ ⋆⊙

- -

- ⊙ ⊙ ⊙ ⊙ ⊙ ⊙ ⊙ ⊙ ⊙ ⊙ ⊙ ⊙

Figure 3.6: Star Formation Rate - Stellar Mass relation for the EGS field. The quies- cent and star-forming galaxies are represented as the yellow empty circles and black dots, respectively. The empty cyan circles represent the galaxies that do not com- ply with some of the selection criteria. The DSFGs with optical counterparts in the CANDELS catalogue are represented as downwards filled red triangles, where empty triangles are those which do not pass the selection criteria. Optical counterparts iden- tified in the IRAC catalogue are represented with an upwards purple triangle. The SFRIR estimated in section 2.2.1.3 from the SCLS2 data is identified with red (CAN- DELS optical counterparts) or purple (IRAC near-infrared counterparts) diamonds. The vertical black dashed line connects the SFRIR and SFRTotal from Barro et al. (2011a). Determination of SFR of SMGs in the EGS 30 3. Demographics of the EGS population

Once the quiescent and star forming galaxies were selected, we locate them in the SFR-stellar mass relation diagram (Figure 3.6). As it can be appreciated, most DSFGs have significantly higher SFRIR calculated from the submillimeter flux densities than from other methods. Furthermore, this difference is not a fixed factor.

−1 −1 SFR[M yr ] −1 log sSFR [yr ] = log = log SFR[M yr ] log M?[M ] (3.2.1) M?[M ] −

In order to explore the star formation main sequence, we transform the previous estimations to specific star formation rate following equation 3.2.1. We will hence use a variable which is normalized by galaxy mass. Then we proceeded with a 3 step iterative linear fit with clipping at σ = 1.5. Our final fits for the star formation main sequence at each redshift panel are presented as solid red lines in Figure 3.7 and the coefficients are presented in Table 3.2, according to equation 3.2.2. This procedure is the same presented by Fang et al. (2018) to ensure that the fit crosses the highest- density galaxy region in the diagram.

−1 log sSFR [yr ] = α log M? [M ] + β (3.2.2)

There is another approach to select star-forming galaxies, which is the direct selection upon the SFR vs M? diagram, as presented by Barro et al. (2017) and Liu et al. (2018). They fitted a star formation main sequence to their data and then selected the quiescent galaxies as those galaxies located below the ∆SFR = 0.7 dex and − ∆SFR = 1.2 dex from the main sequence, respectively. Within their work they − compare this selection with the UVJ diagram, determining that even though the two selection criteria are consistent, the UVJ diagram is more restrictive towards identifying the quiescent and transition populations (Barro et al., 2017). This justifies our selection of the UVJ diagram criteria. Furthermore, we aim to calculate the star formation main sequence for our sample from the already selected star-forming galaxies. Figure 3.7 also presents the 3σ deviation of the main sequence as a gray region, along with other fits in the literature: Fang et al. (2018, blue dash-dot line), which corresponds to the star formation main sequence of the UDS and GOODS-S fields

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 3.2 Star Formation Main Sequence 31 from CANDELS data; Speagle et al. (2014, purple dash-dot line), which presents a time and stellar mass dependent estimation for redshifts z < 6; Barro et al. (2017, cyan dash-dot line), who fitted the high-mass (log M?/M = 10.5) section of the star formation main sequence and used the GOODS-S field from CANDELS data; and Whitaker et al. (2014, green dash-dot line), who fitted a broken power law with a mass cut at log M?/M = 10.2 for the AEGIS, COSMOS, GOODS-N, GOODS-S, and the UKIDSS UDS fields, also using CANDELS data. All the coefficients from the various fits are presented in Table 3.2.

Table 3.2: Coefficients for the star formation main sequence fits by various authors, as expressed in the corresponding equations a,b,c,d. Column 1: redshift range for the fit, which corresponds to each panel in Figure 3.7. Column 2: parameters for our fit, considering equation 3.2.2. Column 3: fit coefficients presented by Fang et al. (2018). Column 4: coefficients for the fit by Barro et al. (2017). Column 5: time at mid-bin used in the Speagle et al. (2014) equation c. Column 6: coefficients for the broken power-law fit by Whitaker et al. (2014), where the fit is split for masses higher and lower than log (M?/M ) 10.2. ∼ z range Our fit Fanga Barrob Speaglec Whitakerd

α β a b µ log C t(z) µlow µhigh log C 0.2-0.5 -0.094 -8.91 -0.009 -9.296 z=0.35 0.5-1.0 -0.325 -6.474 -0.063 -8.987 0.19 1.21 z=0.75 0.94 0.14 1.11 1.0-1.5 -0.576 -3.792 -0.184 -8.860 0.53 1.44 z=1.25 0.99 0.51 1.31 1.5-2.0 0.716 -2.122 -0.255 -8.748 0.64 1.75 z=1.75 1.04 0.62 1.49 2.0-2.5 -0.835 -0.733 -0.311 -8.714 0.68 1.92 z=2.25 0.91 0.67 1.62 2.5-3.0 -0.615 -2.478 z=2.75 3.0-3.5 -0.733 -1.147 z=3.25 3.5-4.0 -0.906 0.918 z=3.75 z > 4.0 -0.596 -2.097 z=5.25

a.Fang et al. (2018) log sSFR = a(log M? 10) + b. h  −  i b.Barro et al. (2017) log SFR = µ log M? 10.5 + log C. M − c.Speagle et al. (2014) log SFR(M?, t) = (0.840.026 t)log M?(6.51 0.11 t). × − × M? corresponds to the stellar mass of each galaxy. h   i d.Whitaker et al. (2014) log SFR = µ log M? 10.2 + log C. M −

Determination of SFR of SMGs in the EGS 32 3. Demographics of the EGS population

Figure 3.7: Specific Star Formation Rate - Stellar Mass relation for the EGS field, with the CANDELS catalogue SFR estimated by Barro et al. (2011a). Solid red line: our fit with the 3σ uncertainty (gray shaded region) we estimated, considering σ2 = P(x µ)2/N 1. Blue dash-dot line: Fang et al. (2018) for the UDS and GOODS- S fields. Purple− dash-dot− line: Speagle et al. (2014) time and mass dependent relation. Cyan dash-dot line: Barro et al. (2017) for high-mass galaxies in GOODS-S field. Green dash-dot line: Whitaker et al. (2014) power law fit for the AEGIS, COSMOS, GOODS-N, GOODS-S, and the UKIDSS UDS fields. The red downwards triangles are the CANDELS optical counterparts of the SCLS2 galaxies and the upwards purple triangles are the IRAC identified counterparts (Zavala et al., 2017). The diamonds connected by dashed lines are the corresponding SFRIR estimated by Zavala et al. (2018) and presented in section 2.2.1.3.

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 3.2 Star Formation Main Sequence 33

From these results we can conclude that the star formation main sequence is still a subject open for discussion, where the results can vary depending upon the population, selection criteria and fitting technique. Our own fit best agrees with the slope fit by Speagle et al. (2014) at low redshifts (z < 1.5), and the high-mass slope of the fit by Whitaker et al. (2014) up to z 2.5. ≈

3.2.1 Location of Dusty Star-Forming Galaxies within the star formation main sequence

Dusty Star Forming Galaxies typically lie in the high-mass end of the star forma- tion main sequence. Within our sample, however, there are some low-mass galaxies log M?/M 9.06 at low redshift (z 0.5). Considering the UV based SFR corrected ∼ ≤ by dust in the CANDELS catalogue, the optical counterparts of the DSFGs lie within the 3σ range of our main sequence fit, except for three galaxies in the 2.5 < z < 3.0 redshift bin. When we consider the SFRIR calculated from submillimeter data 62 out of 68 galaxies are located within the 3σ region and 3 galaxies lie above the 3σ region. Therefore, 4% of our DSFGs sample can be classified as starburst galaxies. However, as it can be appreciated in Figure 3.8 most of the DSFGs lie above the star-formation main sequence even if they are located within the 3σ region of the fit.

Here we must emphasize that there is not yet a consensus of where the star formation main sequence exactly lies. For instance, Zavala et al. (2018) used the

Speagle et al. (2014) SFR-M? relation and found 82% of the same galaxies in the sample within 3σ of the main sequence (Figure 2.6). However, it seems to be a better approach to calculate the star formation main sequence from the same field as the studied DSFG population and with the same methods.

Determination of SFR of SMGs in the EGS 34 3. Demographics of the EGS population

Figure 3.8: Location of DSFGs to the star-formation main sequence for the same redshift bins as in Figure 3.7. The gaussian is centered on the star-formation main sequence with the corresponding σ of the fit. The blue, purple and pink regions correspond to the 1σ, 2σ and 3σ regions of the fit. The orange rectangles are the histogram of DSFGs. Most of the DSFGs lie in the upper section of the star-formation main sequence fit.

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ Chapter 4 GTC-MOS spectra

A proposal for Multi-Object Spectroscopy (MOS) with OSIRIS (Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy) was presented and accepted at the Gran Telescopio de Canarias (GTC). I participated in the plan- ning stage of the proposal GTC-AMEX19 (PI: Aretxaga), selected the target objects and designed the multi-object mask. Once the spectra were observed and delivered, we proceeded with the reduction of the data. We present the detected lines and the identification of the candidate rest-frame emission lines.

4.1 Phase II - planning

The field to observe in GTC-AMEX19 was centered at α = 214.8519671o and δ = +52.8857350o. We selected the Dusty Star-Forming Galaxies (DSFGs) which already had an identified optical counterpart to observe. Whenever there were two galaxies along the same spatial axis position, we chose the one that did not have a measured spectroscopic redshift. Once the DSFGs slits were located, the fiducial stars and sky slits were selected. Finally, suplementary slits were added, if possible, with 3D-HST galaxies within the observing field. In this thesis we present the results for 3 submillimeter galaxies, 7 fiducial stars, 4 sky slits and 4 3D-HST galaxies. These SCLS2 sources and 3D-HST galaxies are listed in Table 4.1. The corresponding slits for these objects are shown in Figure 4.1.

[35] 36 4. GTC-MOS spectra

Figure 4.1: HST F814W background image with the slits corresponding to GTC- AMEX19. The yellow and black boxes are the 850 µm and 450µm SCLS2 sources, respectively. The blue rectangle is the observed field in the GTC-AMEX19 proposal. The cyan rectangles are the observed slits.

The observations were performed with the R1000R grism of the OSIRIS Multi- Object Spectrograph, using a 2x2 binning. The observations were acquired in 5 batches, where each batch had 3 exposures of 1168 seconds each, which adds up to 5 hours. The observations were initially made on April 7 and 8 of 2019 on service ∼ mode. However, upon quality check we discovered one of the batches had to be repeated due to clouds. The new batch was observed on April 29. Three observation batches were obtained with a seeing of 0.9 arcsec and the other two with 0.8 arcsec.

We reduced the data in IRAF, with the packages: onedspec, gtcmos1 and inaoe, all developped by D. Mayya for OSIRIS reduction. We calibrated both for wave- length and flux, using calibration lamps (HgAr, Ne, Xe) and standard stars (HILT600, Ross640, Feige66), respectively. The final calibrated images were average combined with the gtcmos/omcombine task, and the 1D spectrum of each galaxy, with the sky already substracted, was extracted with the onedspec/apall task.

1gtcmos IRAF package cookbook: https://www.inaoep.mx/ ydm/gtcmos/gtcmos.html

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 4.1 Phase II - planning 37

Table 4.1: Galaxies selected for GTC-MOS optical spectral observations in proposal GTC-AMEX19. Column 1: slit number in the planning stage. Column 2: galaxy ID in the 850 µm SCLS2 catalogue. Column 3: galaxy ID in the 450 µm SCLS2 cata- logue. Column 4: galaxy ID in the HST /CANDELS (c), Spitzer/IRAC (d) or 3D-HST catalogues. Column 5: right ascension coordinate for optical counterparts. Column 6: declination coordinate for optical counterparts. Column 7: reported redshift for the optical counterpart. In parenthesis: method for the redshift reported, where 1 denotes optical photometry, and 2 denotes HST grism.

Slit ID850µm ID450µm ID α δ z (method) (deg.) (deg.) c +0.24 7 850.059 450.24 18694 214.85551 52.84883 2.75−0.21 (1) e +0.0041 19 39103 214.83087 52.89241 0.7281−0.0048 (2) e +0.0556 20a 34861 214.86507 52.89737 0.7126−0.0302 (2) c +0.09 20 850.038 450.27 27358 214.86472 52.89908 1.93−0.01 (2) e +0.1232 28 38223 214.88542 52.92622 0.6862−0.1112 (2) e +0.0019 30 40111 214.88124 52.93277 0.7577−0.0071 (2) 32 850.060 450.75 121668d 214.84949 52.93810 0.94 0.06 (1) ±

17 HST-38223.028 34 15 HST-40111.030 3 5 8 14 850.3820 11 850.597 HST-34861.0 850.1429 2 12 27 850.603233 21 24 1 13 31 16 19 22 HST-39103.0 4 6 26

10 18 23 25

9

-1.31e-19 4.46e-19 2.76e-18 1.20e-17 4.88e-17 1.94e-16 Figure 4.2: 2D spectra reduced with IRAF, calibrated in wavelength and flux. The sky has already been substracted to better observe features. The red labels correspond to the DSFGs from the SCLS2 catalogue and the cyan labels indicate galaxies from the 3D-HST catalogue.

Determination of SFR of SMGs in the EGS 38 4. GTC-MOS spectra

4.2 Line identification and redshift report

In order to identify the lines in our spectra we explored both the 2D and 1D spectra. In the following paragraphs we will present the identified lines and derived redshifts, when possible. We used template spectra of starbursts galaxies and quasars, like the composite spectrum presented is Figure 4.3 (Francis et al., 1991) and Figure 4.4 (Conti et al., 1996). The reported wavelengths for the lines correspond to the center value of a gaussian curve fitted to the line in the 1D spectrum.

Figure 4.3: Composite spectrum template for a QSO plotted as λF (λ) vs rest-frame λ, and the identified lines with their corresponding wavelength. Image taken from Francis et al. (1991)

Figure 4.4: Spectrum for the starburst galaxy NGC 1741B. Image taken from Conti et al. (1996)

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 4.2 Line identification and redshift report 39

4.2.1 HST-galaxies

+0.0041 HST 39103 has a reported HST grism redshift of z = 0.7281−0.0048 in the 3D-HST catalogue. There are three lines in our observed spectrum, located at 5074.57, 6461.84 and 7915.96 A.˚ We considered the following cases. If the observed 6461.84 A˚ line corresponds to [OII]λ3727, then the redshift would be z = 0.7338, but the other lines observed in the spectrum would be located at the rest-frame wavelength of 2926 A˚ and 4565.67 A,˚ which do not correspond to any known emission lines. If we identify the observed lines (at 5074.57, 6461.84 and 7915.96 A)˚ as Lyαλ1216, CIVλ1549 and the blend AlIII + CIII]λλ1892, 1909 (Figure 4.5), then we obtain a redshift of z = 3.1698, with which the SiIV+OIV]λ1400 line would lie (at 5837.7 A)˚ in a region contaminated by sky lines and, since SiIV + OIV]λ1400 is fainter than Lyα and CIV, we would not be able to detect it. The observer-frame width of the 7915.96 A˚ line is 13.78 A,˚ and the candidate blend of AlIII + CIII]λλ1892, 1909 is hence unresolved. The apparent angular size of the galaxy is 1.76 arcsec, which at the corresponding redshift would ∼ be an apparent radius of 6.8 kpc. We will need to check how many lines were ∼ detected in the 3D-HST grism to reconcile these solutions. +0.0556 HST 34861 has an HST grism redshift of z = 0.7126−0.0302, reported in the 3D- HST catalogue. We present the slit, spectra and lines in Figure 4.7. Two emission lines were identified in the extracted spectrum: 6382.85 A˚ and 8572.37 A.˚ These lines were identified as [OII]λ3727 and [OIII]λ5007 for a redshift of z = 0.712, respectively. The line Hβ4861 would lie on top of a sky lines region (at 8324 A)˚ in the observed spectrum. We also considered the following cases. If the line detected at 6382.85 A˚ were MgIIλ2798, then the redshift would be z = 1.2812 and the lines CIII]λ1909 and [OII]λ3727 would lie at 4354.8 A˚ and 8502 A,˚ respectively, but these lines were not detected at those positions, and the observed line 8572.37 A˚ would correspond to the rest frame wavelength 3757.8 A,˚ where the closest line is 30 A˚ away ([OII]λ3727). If the line detected at 6382.85 A˚ were Hδ4102, then the redshift would be z = 0.556 and the lines [OII]λ3727 and Hγ would lie at 5799 A˚ and 6753 A,˚ where no lines are detected, and the observed line at 8572.37 A,˚ would correspond to a rest-frame wavelength of 5508.9 A,˚ where there are no emission lines in the templates. If the line observed at 8572.37 A˚ corresponded to Hβ, then the lines Hγ4340 and [OIII]λλ4959, 5007 would lie at 7653.59 A,˚ 8745.19 A˚ and 8829.84 A˚ in the observed spectrum, but these lines

Determination of SFR of SMGs in the EGS 40 4. GTC-MOS spectra are not detected, and the other observed line at 6382.85 A˚ would correspond to a rest- frame wavelength of 3618.9 A,˚ where there is no emission line associated. Therefore, we estimate a z = 0.7123 for this source, in agreement with the 3D-HST reported redshift.

Figure 4.5: (Top) Observed slit on HST F814w band image. (Middle) Extracted 1D spectra of galaxy HST 39103 with the possible lines: Lyαλ1216, CIVλ1549 and the blend OIII] + CIIIλλ1892, 1909. (Bottom) 2D spectra for slit 19 with galaxy HST 39103.

19 39103.0

15.5377"

-0.017 -0.013 -0.0083 -0.0038 0.00064 0.0052 0.0096 0.014 0.019 0.023 0.028

-39193

Ly

5000 5500 6000 6500 7000 7500 8000 8500 9000 Wavelength

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 4.2 Line identification and redshift report 41

Figure 4.6: (Left) 2D spectral lines. (Right) 1D spectral lines. Identified lines at 5074.57 A(˚ Top), 6461.84 A(˚ Middle) and 7915.96 A(˚ Bottom).

Determination of SFR of SMGs in the EGS 42 4. GTC-MOS spectra

Figure 4.7: (Top) Observed slit on HST F814w band image with HST 34861. (Middle) Extracted 1D spectra of galaxy HST 34861 with the identified lines: [OII]λ3727 and [OIII]λ5007. (Bottom) 2D spectra for slit 20 with galaxy HST 34861.

HST-34861 20 K-38 27358

12.6952"

-0.017 -0.013 -0.0083 -0.0038 0.00064 0.0052 0.0096 0.014 0.019 0.023 0.028

5000 5500 6000 6500 7000 7500 8000 8500 9000 Wavelength

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 4.2 Line identification and redshift report 43

Figure 4.8: Identified lines for HST 34861 at (Top) 6382.85 A˚ and (Bottom) 8572.37A.˚ (Left) 2D spectral lines. (Right) 1D spectral lines.

+0.1232 HST 38223 has an HST grism redshift of z = 0.6862−0.1112. We identified one emission line at 6175.78 A,˚ shown in Figure 4.9. We considered this line to be [OII]λ3727 resulting in z = 0.7586. Therefore, we tried to find the rest-frame lines MgIIλ2798, Hδ4102, Hγ4340, Hβ4861, but the first line lies outside of the ob- servational wavelength range and the other three lines lie a region of the spectrum dominated by sky lines. If we considered the detected line to be MgIIλ2798, then the redshift would be z = 1.34, and the lines [OII] and CIII] would lie at 8730.12 A˚ (on sky lines region) and 4471.64 A˚ (outside of the observational wavelength range), respectively. If we considered the detected line to be Hδ, then the redshift would be z = 0.5978 and the lines [OII]λ3727, Hγ4340 and Hβ4861 would lie at 5955 A,˚ 6934.45 A˚ and 7766.9 A˚ in the observed spectrum, but these lines are not detected.

Determination of SFR of SMGs in the EGS 44 4. GTC-MOS spectra

Figure 4.9: (Top) Observed slit on HST F814w band image with HST 38223. (Middle) Extracted 1D spectra of galaxy HST 38223 with the identified line at 6175.78A.˚ Below, 2D spectra for slit 28 with galaxy HST 38223. (Bottom) Identified line [OII]λ3727 at 6175.78A˚ in the spectrum of HST 38223. (Left) 2D spectrum. (Right) 1D spectrum.

5000 5500 6000 6500 7000 7500 8000 8500 9000 Wavelength

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 4.2 Line identification and redshift report 45

Figure 4.10: (Top) Observed slit on HST F814w band image with HST 40111. (Mid- dle) Extracted 1D spectra of galaxy HST 40111 with the identified line at 6554.15A.˚ Below, 2D spectra for slit 30 with galaxy HST 40111. (Bottom) Identified line [OII]λ3727 at 6554.15A.˚

30 HST-40111

9.22589"

-0.017 -0.013 -0.0083 -0.0038 0.00064 0.0052 0.0096 0.014 0.019 0.023 0.028

-40111

5

5 55 5 5 5

Determination of SFR of SMGs in the EGS 46 4. GTC-MOS spectra

+0.0019 The 3D-HST galaxy HST 40111 has an HST grism redshift of 0.7577−0.0071. We were able to identify one line at 6554.15 A,˚ as can be seen in Figure 4.10. We identified this line as [OII]λ3727 and estimated a redshift of z = 0.7586. The other lines that could be detected are Hδ4102, Hγ4340 and Hβ4861 at 7213.7 A,˚ 7632.3 A˚ and 8548.5 A,˚ where there are sky lines regions.

4.2.2 Submillimeter galaxies

In the spectrum from the galaxy 850.59 two lines were found at 7086.48 A˚ and 7388.48 A.˚ The 1D and 2D spectra, slit and detected lines are shown in Figure 4.11. +0.24 The measured redshift through optical photometry is z = 2.75−0.21 in the CANDELS catalogue. For this galaxy we considered the possibility of the following lines. If the 7086.48 A˚ line corresponded to the [CIII]λ1909 line, then the redshift would be z = 2.7124, where the CIVλ1549, SiIV/OIV]λ1400 and MgIIλ2798 lines would lie at 5796 A,˚ 5197 A˚ and 10387 A˚ . However, the first line is not observed in the spectrum, and the second and last lines would fall outside of our observed wavelength range, and the observed line at 7388.48 A˚ would correspond to a rest-frame wavelength of 1990 A,˚ where there is no associated emission line. If the 7086.48 A˚ observed line were [CIV]λ1549, the redshift would be z = 3.5752 and the CIII]λ1909 line would lie on top of a sky lines region (at 8734A)˚ and the 7388.38A˚ line would correspond to a rest frame wavelength of 1615.23A˚ , where there is no emission line. On the other hand, if the observed 7388.48 A˚ line corresponds to CIII]λ1909, the redshift would be z = 2.8711, the CIVλ1549, SiIV/OIV]λ1400 and MgIIλ2798 lines would lie at 5996 A,˚ 5419 A˚ and 10831 A,˚ where the first line would be on top of a sky lines region, the second line is not observed in the spectrum and the last line falls outside of the observed wavelength window. For this association the 7086.48 A˚ observed line would correspond to a rest-frame wavelength of 1830 A,˚ where there is no associated emission line.

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 4.2 Line identification and redshift report 47

Figure 4.11: (Top right) Extracted 1D spectra of galaxy 850.59 with the identified lines at 7086.48A˚ and 7388.48A.˚ (Top left) Observed slit on HST F814w band image with 850.59. (Upper middle) Identified lines at 7086.48A˚ and 7388.48A,˚ 1D spectrum. (Bottom) 2D spectra for slit 7 with galaxy 850.59.

24

59 HST-18694

7

0.00282099 deg

-0.017 -0.013 -0.0083 -0.0038 0.00064 0.0052 0.0096 0.014 0.019 0.023 0.028

55

5

5 55 5 5 5

Determination of SFR of SMGs in the EGS 48 4. GTC-MOS spectra

Figure 4.12: (Top) Extracted 1D spectra of galaxy 850.38 with the identified line at 8182.53A.˚ (Upper middle) Observed slit 20 on HST F814w band image with 850.38. (Lower middle) Identified line MgII at 8182.53A(˚ Bottom) 2D spectra for slit 20 with galaxy 850.38.

38 27 S38 HST-27358 20

14.4688"

-0.017 -0.013 -0.0083 -0.0038 0.00064 0.0052 0.0096 0.014 0.019 0.023 0.028

5000 5500 6000 6500 7000 7500 8000 8500 9000 Wavelength

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 4.2 Line identification and redshift report 49

Figure 4.13: (Top left) Observed slit 32 on HST F814w band image with 850.60. (Top right) Extracted 1D spectra of galaxy 850.60 with the identified line at 8412 and 7372A˚ for Hγλ4340 and [OII]λ3727. (Middle) Identified lines in the 2D spectrum: 8412A(˚ Left) and 7372A(˚ Right). (Bottom) 2D spectra for slit 32 with galaxy 850.60.

60 irac121668

32

10.5199"

-0.017 -0.013 -0.0083 -0.0038 0.00064 0.0052 0.0096 0.014 0.019 0.023 0.028

5

5

5 55 5 5 5

Determination of SFR of SMGs in the EGS 50 4. GTC-MOS spectra

+0.09 The DSFG 850.38 has a reported HST grism redshift of z = 1.93−0.01 for the CANDELS optical counterpart. We were able to detect only one line in the extracted spectrum, at 8182.53 A.˚ We considered the following possibilities. If we identify this line as MgIIλ2798, the resdhift would be z = 1.924, where the lines CIII]λ1909 and [OII]λ3727 would correspond to an observed wavelength of 5582.68 A˚ and 10,899 A,˚ where the first line would lie on top of a sky line and the last line would fall outside our observational wavelength range, as well as the CIVλ1549 line (4529 A).˚ If the observed line is CIII]λ1909 then MgIIλ2798 would fall outside of our observational wavelength window, and CIVλ1549 is not observed in the spectrum at 6629.72A.˚ If we considered the observed line is [OII]λ3727, then the MgIIλ2798 and Hγ lines would lie at 6127.62Aand˚ 9504.6A,˚ where the first one is not observed in the spectrum and the last one falls outside of the observational wavelength range. Hence, we consider the rest-frame line MgIIλ2798 as the appropriate association for this line. The slit image, extracted spectrum, identified line and 2D spectrum are presented in Figure 4.12. The DSFG 850.60 has an optical photometric redshift of z = 0.94 0.06 in ± the CANDELS catalogue for its associated optical counterpart. We were unable to clearly identify lines in the 1D extracted spectrum. However, in the 2D spectra we were able to identify two lines at 7372 A˚ and 8412 A.˚ For these lines we considered the following lines: Hγλ4340 and [OII]λ3727. We now consider each line separately for its analysis. If the observed 7372 A˚ corresponds to [OII]λ3727, then the redshift would be z = 0.978 and the lines Hδ and Hγ would lie in sky lines regions at 8113.76 A˚ and 8584.5 A.˚ If this line were MgIIλ2798, then the redshift would be z = 1.63 and the lines [OII]λ3727 and CIIIλ1909 would lie outside the observational wavelength region (at 9802 A˚ and 5020 A).˚ If the observed line at 7372 A˚ were Hδ4102, then the redshift would be z = 0.7972 and the lines [OII]λ3727, Hγ4340, Hβ4861 would lie at 6698 A,˚ 7799.8 A˚ and 8736 A˚ in the observed spectrum. None of these lines are visible at these wavelengths, therefore, we assume the most likely rest-frame line associated to 7372 A˚ is [OII]λ3727. We considered the other observed line at 8412 A˚ corresponds to the line Hγ4340, for a z = 0.9382, and the lines Hδ4102 and Hβ4861 would lie at 7950.5 A˚ and 9421 A˚ on top of sky lines regions. If the observed line at 8412 A˚ were Hδ, then the redshift would be z = 1.0507, [OII]λ3727 and Hγ would lie at 7642.96 A˚ and 8900 A˚ in the observed spectrum (where they are not detected),

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 4.2 Line identification and redshift report 51 and the other observed line (7372 A)˚ would correspond to the rest-frame wavelength 3594.87 A,˚ where there is no associated emission line. If the observed line at 8412 A˚ were Hβ the redshift would be z = 0.73, the lines [OII]λ3727 Hδ4102, Hγ4340 and [OIII]λλ4959, 5007 would lie at 6449.5, 7098.5, 7510.37, 8581.5 and 8664.6 A,˚ where none of these lines are observed in the spectrum, and the other observed line (7372 A)˚ would correspond to a rest-frame wavelength of 4261.3 A,˚ where there is no associated emission line. Therefore, we conclude that these two observed lines (7372 and 8412 A)˚ are [OII]λ3727 and Hγ4340. The slit image, 1D extracted spectra and 2D spectra are presented in Figure 4.13. As can be seen, detecting lines in the optical spectra of dusty star forming galaxies is a difficult endeavour. We were unable to identify forbidden or recombination lines with good enough quality to measure fluxes in order to measure SFR properties. We could attempt stacking more observation hours, to try to obtain lines that could be detected even if they lie in a region contaminated by sky lines. However, we will continue to work with these spectra to attempt reducing the contamination by sky lines with other reduction techniques.

Determination of SFR of SMGs in the EGS 52 4. GTC-MOS spectra

Table 4.2: Compilation of the observed lines in the spectra and identified lines and parameters if it was possible. Column 1: slit of the observed source. Column 2: name of the observed source. Column 3: wavelength of the observed line. Column 4: associated rest-frame emission line. Column 5: estimated redshift considering the associated line. We highlight in bold the robust line associations and redshift estimations.

Slit Source Observed line Associated line Redshift A˚ 20 SCLS2 - 850.38 8182.53 MgIIλ2798 1.924 7 SCLS2 -850.59 7086.48 CIII]λ1909? 7388.48 CIII]λ1909? ? 7086.48 [CIV]λ1549? 32 SCLS2 - 850.60 7372 [OII]λ3727 0.9581 ∼ 8412 Hγ4340 20 3DHST - 34861 6482.85∼ [OII]λ3727 0.7123 8572.37 [OIII]λ5007 28 3DHST - 38223 6175.78 [OII]λ3727 0.7586 6175.78 MgIIλ2798 1.34 19 3DHST - 39103 5074.57 Lyαλ1216 6461.84 CIVλ1549 3.1699 7915.96 Al III+CIII]λλ1892, 1909 30 3DHST - 40111 6554.15 [OII]λ3727 0.7586

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ Chapter 5 Conclusions and future work

When COBE measured the Cosmic Infrared Background (CIB) it was discovered that about half of the Extragalactic Background Light was emitted in the IR. This implies that a great amount of the star-formation history is enshrouded by dust and needs to be studied at the appropriate wavelengths. Submillimeter Galaxies (SMGs) are a high-z population with high IR Luminosities and star-formation rates (SFR). They have high amounts of dust that absorbs the UV light emitted by young stars and re-emits it in the FIR-submillimeter bands. The shape of the emission is modeled with a modified black body at the temperature of the dust Td that is affected by the negative K-correction at wavelengths higher than λ 250 µm. Therefore, the SED ≥ is redshifted to the submillimiter range, where this population of galaxies was first discovered. The star-formation main sequence is the relation between the Star-Formation

Rate (SFR) or specific Star-Formation Rate (sSFR) and the stellar mass (M?). This relation, however, is still affected by the selection of galaxies, initial mass functions and stellar population models that are used to estimate the SFR and M?. Furthermore, there is still discussion upon whether there is a slope difference for high- and low- mass galaxies. The relation is known to evolve with redshift, as it was characterized by Speagle et al. (2014). Within this work we measured the fluxes of Dusty Star-Forming Galaxies (DSFG) from the SCUBA-2 Cosmology Legacy Survey (SCLS2) at 450 µm and 850 µm and compared them with those reported by Zavala et al. (2017). Upon finding a good agreement we proceeded to work with the SCLS2 sample galaxies that had a counter- part identified in the CANDELS or IRAC catalogues. We used the deboosted fluxes

[53] 54 5. Conclusions and future work by Zavala et al. (2017) to estimate IR luminosities with the negative K-correction for a modified black body at the redshift z and dust temperature Td reported for each galaxy. Finally, we calculated the SFRIR using a Kennicutt (1998) relation for a Chabrier (2003) IMF.

Then we selected the star-forming galaxies from the CANDELS catalogue that complied with the selection criteria used in Fang et al. (2018). We used the UVJ color diagram corrected by dust and the quiescent selection region defined by Williams et al. (2009). We represented within the UVJ diagram the optical counterparts for the DSFGs, finding that all but two lie in the star-forming region of the diagram. One of these two is low-redshift galaxy that does not comply with the selection criteria, because it does not have reliable photometric values. After the star-forming galaxies were selected we proceeded to fit the star-formation main sequence in a log sSFR vs log M? relation, separated by redshift bins of ∆z = 0.5. We compared our star- formation main sequence fit with other authors (i.e. Fang et al., 2018; Whitaker et al., 2014; Speagle et al., 2014; Barro et al., 2017), finding discrepancies between their fits according to sample selection, field, the selection of star-forming galaxies and fitted function. We represented the SFRIR derived from the submillimeter fluxes and compared them with the total SFRUV+IR by Barro et al. (2011a) presented in the CANDELS catalogue, finding large discrepancies. The estimated SFRIR are better constrained as they are based on the FIR and not on NIR or MIR-based extrapolation.

When we compared the SFR derived from submillimeter fluxes to the total SFR es- timated by adding the LIR, derived from the MIR (i.e. 24 µm), and the UV-luminosity uncorrected by dust, we found the first one was higher in most of the cases ( 79%). ∼ Therefore, we can conclude that the UV/optical based SFRs underestimate the total SFR produced by DSFGs and in some cases overestimates it.

We noticed that the selection of star-forming galaxies may affect the star-formation main sequence fit, as well as the stellar mass selection criteria and the function fitted to the data (i.e. linear, power law or broken power-law fit). We we considered the SFR derived from submillimeter fluxes for all the DSFGs. Most of the DSFGs are located above the star formation main sequence and inside the 3σ region of the fit. Only 4% of the DSFGs lie above the 3σ region of star formation main sequence, implying a classification as starburst galaxies.

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ 55

We observed three DSFGs with the GTC-MOS OSIRIS. We presented the redshift estimates for the identified candidate emission lines detected in our observed spectra. However, we were not able to determine a robust redshift for one of these galaxies, as we could detect few lines and some of them lie on top of sky lines. Therefore, the future work related to the spectra of the DSFGs is to integrate more observing hours and work with methods to identify lines within the sky lines. The TOLTEC large-format camera will arrive soon at the Large Millimeter Tele- scope Alfonso Serrano, to be used with the full 50-m diameter dish. It is designed to simultaneously observe at 1.1, 1.4 and 2.0 mm. Furthermore, one of its legacy projects is the Ultra Deep Survey which will cover 0.8 square degrees down to the confusion ∼ limit at 1.1 mm ( 0.025 mJy). This configuration will be the best for wide-scale, ∼ high-resolution (5 arcsec), continuum imaging in the millimeter wavelength range with single-dish telescopes. We will be able to detect the submillimeter and dusty star-forming galaxies within the deep fields GOODS-S, UDS and COSMOS to be observed in the Ultra-Deep Survey of Star-forming Galaxies, and better constrain the FIR-derived measurements of the SFR with ancilliary CANDELS data. As it has been previously demonstrated there are strong biases when selecting pop- ulations of galaxies detected at different wavelengths. Therefore, the simultaneously observed deep fields within the TOLTEC legacy project will provide a uniformly se- lected population of galaxies. These new observations will provide flux measurements that will better constrain the Rayleigh-Jeans portion of the SED, hence IR-luminosity and IR-based SFR, which will complement the view of the UV-derived star formation density with its complementary IR-derived star formation density. These observations, along with the multi-wavelength studies available for these deep fields will provide a wide range of data that will allow a more complete understanding of the physical properties of Dusty Star-Forming Galaxies. We will aim to reproduce the procedure presented in this thesis with the 3 deep TOLTEC fields in the Ultra-Deep Survey of Star-forming Galaxies and the corre- sponding CANDELS data for these fields. We will select the star-forming galaxies within the CANDELS catalogue and adjust the corresponding star-formation main sequence for those fields, following with the comparison of the SFR estimations from the millimeter-derived luminosities for those SMGs and DSFGs with identified optical and IR counterparts. Then we will perform the star-formation comparison by slicing

Determination of SFR of SMGs in the EGS 56 5. Conclusions and future work luminosities and redshift. This will provide, for the first time, an unbiased sample of DSFGs discerning between their orders of luminosity (Luminous Infrared Galaxies, Ultra Luminous Infrared Galaxies, Hyper Luminous Infrared Galaxies and SMGs), allowing the study of each population evolution across cosmic time. We will also perform stacking analysis of star-forming galaxies formally undetected by TOLTEC, hence constraining statistically their obscured star-formation properties. We will be able to ascertain at what cosmic epoch dust is most effective obscuring what type of star-forming galaxy. We will expand the results presented in this thesis for the EGS field to a greater sample of deep fields and a larger number of galaxies. This will provide a broader study of the properties of the DSFG population and their evolution discriminated by mass and luminosity. This will allow us to estimate the obscured star formation fraction at large redshifts. These results will lead us towards a more complete understanding of the star-formation history and evolution of the universe.

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ List of Figures

1.1 K-correction for a modified black body and submillimeter observation wavelengths ...... 4 1.2 IR-SED fitting for an irac galaxy ...... 6

2.1 AEGIS coverage map of the Extended Groth Strip ...... 10 2.2 SCLS-2 S/N maps at 450 µm and 850 µm ...... 12 2.3 The AzTEC 1.1 mm S/N map of the EGS field ...... 13 2.4 Comparison of measured flux densities at the SCLS2 450 µm map. . . 18

2.5 Comparison of estimated LIR from SCLS2 850 µm and 450 µm data. 19 2.6 Star-forming main sequence for DSFGs with optical counterparts . . . 20

3.1 UVJ rest-frame color diagram uncorrected for dust extinction for EGS field selected galaxies. (0 < z < 2)...... 24 3.2 UVJ rest-frame color diagram uncorrected for dust extinction for EGS field selected galaxies. (z > 2) ...... 25 3.3 Effect of dust correction in UVJ rest-frame color diagrams ...... 26 3.4 UVJ color diagram corrected for dust extinction. (0 < z < 2) . . . . . 27 3.5 UVJ color diagram corrected for dust extinction. (2 < z < 4) . . . . . 28

3.6 SFR M? relation for the EGS field ...... 29 − 3.7 Specific Star Formation Rate - Stellar Mass relation for the EGS field 32 3.8 Location of DSFGs to the star-formation main sequence ...... 34

4.1 GTC-AMEX19 proposed slits for GTC-MOS ...... 36 4.2 2D spectra reduced with substracted sky ...... 37 4.3 Composite spectrum template for QSOs ...... 38

[57] 58 LIST OF FIGURES

4.4 Spectrum for starburst galaxy ...... 38 4.5 HST 39103 - Field, 1D and 2D spectra ...... 40 4.6 HST 39103 - Detected lines ...... 41 4.7 HST 34861 - Spectra and detected lines ...... 42 4.8 HST 34861 - Detected lines ...... 43 4.9 HST 38223 - Spectra and detected lines ...... 44 4.10 HST 40111 - Spectra ...... 45 4.11 850.59 - Spectra and detected lines ...... 47 4.12 850.38 - Spectra and detected lines ...... 48 4.13 850.60 - Spectra and detected lines ...... 49

Astrophysics Department Instituto Nacional de Astrof´ısica, Optica´ y Electronica´ List of Tables

2.1 CANDELS and IRAC counterparts to SCLS2 sources ...... 14

3.1 Number of galaxies in the EGS, UDS and GOODS-S fields ...... 23 3.2 Coefficients for star formation main sequence fits ...... 31

4.1 Galaxies selected for GTC-MOS observations ...... 37 4.2 Compilation of the observed lines in the spectra and identified lines and parameters if it was possible. Column 1: slit of the observed source. Column 2: name of the observed source. Column 3: wavelength of the observed line. Column 4: associated rest-frame emission line. Column 5: estimated redshift considering the associated line. We highlight in bold the robust line associations and redshift estimations...... 52

[59] 60 LIST OF TABLES

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Determination of SFR of SMGs in the EGS