Col-Ossos: Z-Band Photometry Reveals Three Distinct Tno Surface Types Identifying Cold Classical Tno Surfaces

Home , 2006 Polonskaya, Michele Bannister, Minor Planet Center

COL-OSSOS: Z-BAND PHOTOMETRY REVEALS THREE DISTINCT TNO SURFACE TYPES IDENTIFYING COLD CLASSICAL TNO SURFACES

Rosemary E. Pike Wesley Fraser; Megan Schwamb; J.J. Kavelaars; Michael Marsset; Michele Bannister; Ruth Murray-Clay; Katheryn Volk; Matthew Lehner; Shiang-Yu Wang; Aurelie Guilbert; Nuno Peixinho; Mike Alexandersen; Ying-Tung Chen; Brett Gladman; Stephen Gwyn; Jean-Marc Petit

Published in AJ, Sept. 2017,154, 100 TNO SURFACES: WHAT & WHY THE KUIPER BELT Neptune • TNOs were distributed into the outer Solar System during giant planet migration • The orbital distribution of TNOs provides constraints on the dynamics of scattering • The surface properties of TNOs provide constraints on the surface properties of the initial proto-planetesimal disk • Surface properties result from composition and evolution Minor Planet Center: Outer Solar System TNO SURFACES: WHAT & WHY

44 The Solar System Beyond Neptune TNO DYNAMICAL CLASSIFICATIONS

large-e and/or large-i: hot classicals

low-e, low-i: Cold Classical TNOs

Dynamically excited: non-cold classical TNOsl includes Resonant, Detached, Hot Classical, Scattering, Centaurs

Fig. 1. Left: Flowchart for the outer solar system nomenclature. When orbital elements are involved they should be interpreted as the osculating barycentric elements. Right: A cartoon of the nomenclatureGladman scheme (not etto scale). al. 2008, The boundaries SSBN between the Cen- taurs, JFCs, scattered disk, and inner Oort cloud are based on current orbital elements; the boundaries are not perihelion distance curves. Resonance inhabitance and the “fuzzy” SDO boundary are determined by 10-m.y. numerical integrations. The classical belt/ detached TNO split is an arbitrary division.

sified the entire three-opposition (or longer) sample present in the IAU’s Minor Planet Center (MPC) as of May 2006. a a J 2 The tables provide our SSBN07 classification for this Solar TJ ≡ + 2 (1 – e ) cos i (1) System Beyond Neptune book. Transneptunian objects that a aJ are now numbered also have their original provisional des- ignation to aid their identification in previously published where a, e, and i are the orbital semimajor axis, eccentric- literature. ity, and inclination of a comet and aJ is the semimajor axis We have found that in order to make a sensible TNO dy- of Jupiter (about 5.2 AU). A circular orbit in the reference namical classification, we were forced to define what is not plane (approximately the ecliptic but more correctly a TNO; we thus begin with the regions that bound TNO Jupiter’s orbital plane) with a = aJ yields TJ = 3.0. Exterior semimajor axes (Centaurs and the Oort cloud) and eccen- coplanar orbits with q = aJ = a(1 – e) (i.e., perihelion at Jupi- tricities (the JFCs). ter) have TJ just below 3, and thus as long as i is small the condition TJ < 3 is nearly the same as having q interior to 2. CENTAURS AND COMETARY OBJECTS Jupiter. However, if the inclination in increased or q pushed considerably below Jupiter, TJ drops well below 3 and can Historically, periodic comets were classified according even become negative for retrograde orbits. to their orbital period P, with short-period comets having Because of this, Carusi et al. (1987) and Levison (1996) P < 200 yr and long-period comets with P > 200 yr. While suggested that TJ = 2.0 provided a convenient lower bound- there existed at one point a classification system that as- ary for a Jupiter-family comet (JFC). Comets with TJ < 2 signed the short-period comets to planetary “families” ac- include retrograde and other high-i, high-e comets, while cording to which of the giant planets was the closest to their high-e but low-i orbits can remain in the range TJ = 2–3. heliocentric distances at aphelion, it became evident that Carusi et al. (1987) considered a TJ = 1.5 lower boundary, there was little dynamical significance to such a classifi- which has the merit of including comets 96P and 8P as cation, except in the case of the Jupiter family, which (by JFCs; the most notable comet that might be on the “wrong” virtue of the typical orbital eccentricities involved) has side is then 27P/Crommelin (TJ = 1.48), although with P = tended to apply to comets having P < 20–30 years. This 27 yr this object could appropriately be relegated to the suggested it would be reasonable to cement this classifica- comet group variously categorized as of “Halley type” (HT) tion with the use of the Tisserand parameter with respect or of “intermediate period” (Comet 1P/Halley itself has TJ = to Jupiter (first attempted by Kresák, 1972), defined by the –0.61). Since it is not directly relevant to our Kuiper belt Tisserand parameter TJ with respect to Jupiter nomenclature, we drop the issue of the lower TJ boundary. Gemini Proposal Section 2 Page 5 a.TNO colour and the SURFACES: planetesimal disk WHAT & WHY Dalle Ore et al. Fraser & Brown The Col-OSSOS Project • Sample is from a r'-J r'-J characterized survey multiple ice lines along the disk; volatile loss in a • Follow-up photometry of a each line creates mixed disk produces a diferent surface three surfaces magnitude limited sub-sample g'-r' g'-r' of the Outer Solar System

~45 AU ~18 AU ~5 AU ~5 AU ~18 AU ~45 AU Origins Survey discoveries b. changing the planetary architecture abrupt Neptune migration smooth Neptune migration Colossos Science Goals • Determine the number of surface types • Determine the intrinsic population fraction of these surface types • Dependence between color and dynamics? • Dependence between color and size?

Figure 1: Demonstration of a how a combined colour-dynamical survey will inform us about the outer Solar System’s cosmogony. a: observed (g’-r’) vs. (r’-J) colours of dynamically excited TNOs (star symbols) with H>6 and neutral (black) and red (red) surfaces, and cold classical objects (blue circles). Coloured ellipses designate example compositional classes with ellipse colours matching formative regions in the protoplanetesimal disk diagrams below. Left: The model of Dalle Ore has at least 5 classes originating from a disk with strong compositional gradients and many ice lines. Right: The model of Fraser has 3 classes originating from a well mixed disk. b: Contrast of the dynamical instability (left) and smooth (right) models of Neptune migration and their consequences for the formation of the Kuiper Belt. Symbols and colours shown match those in diagram a. Left: objects are trapped during instability, captured top-down into the MMRs from dynamically excited populations, and therefore only have members from the neutral (black points) or red (red points) compositional classes. Right: some objects are swept during migration into MMRs from the cold classical region, and will posses objects with surfaces like the cold classical objects (blue points) at low inclinations, along with the neutral and red classes. Additionally, sweeping will deposit some low eccentricity neutral and red objects into the cold classical region. Compositional information will allow the two situations to be distinguished. Colors of the Outer Solar System Origins Survey (Col-OSSOS)

rgJgr observations & pilot z-band study discovery & u band pilot z-band study

Gemini Image Credit: Gemini Subaru CFHT 2.0 1.8 1.6 1.4

(r’-J) . 1 2 Blue Binary 1.0 Cold Classical 0.8 Excited 01.60 0.9 0.8 0.7 Col-OSSOS 0.6 0.5 (r’-z’) Photometry 0.4 0.3 0.2 0.1 2.2 2.0 1.8

(u’-g’) 1.6 1.4 1.2 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 Plot: W. Fraser (g’-r’) z-Band Sample Tegler & Romanishin 2003 Peixinho et al. 2003, 2012, 2015 Tegler et al. 2003, 2016 Barucci et al. 2005 Fraser & Brown 2012 Dalle Ore et al. 2013 Wong & Brown 2017 … z-Band Photometry

Pike et al. 2017, AJ Fraser & Brown 2012 z-Band Photometry

Pike et al. 2017, AJ CONCLUSION: COLD CLASSICALFraser SURFACES & Brown 2012 ARE DISTINCT IN g, r, z z-Band Photometry from Ofek 2012 Pike et al. 2017, AJ Col-OSSOS Expansion Constraining Neptune’s Migration: Surfaces of Resonant TNOs Rosemary Pike, Kat Volk, Ruth Murray-Clay, Wes Fraser, Michele Bannister, Michael Marsset, Meg Schwamb, Matt Lehner, Aurelie Gulibert

• Dynamical simulations of Neptune’s migration to predict the number of cold classicals in the 2:1

• Photometry of a complete sample of 2:1 TNOs from the OSSOS Ensemble characterized surveys in g, r, and z bands 0.6 OSSOS observed objects: cold-classical colors not cold-classical colors this proposal 0.5 other current 2:1 resonance initial 2:1 location if model: 0.4 Neptune migrated 4AU source population capture locations targets captured objects 0.3 0.2 eccentricity (e) 0.1 0.0 42 44 46 48 50 semi-major axis (AU) Plot: R. Murray-Clay K. Volk Col-OSSOS Expansion Program on LBT

• LBT in Mount Graham, AZ • 34 TNOs in the 2:1, mr≤24.5

• 34 TNOs in the 2:1, mr≤24.5 • April 2018: 2/3 nights lost to weather

• z band using LBC Red • 5 2:1s and 2 Cold classicals observed

• g and r using LBC Blue • 2018B: 3.5 nights awarded by NOAO CONCLUSIONS • Red Cold Classical TNO surfaces are distinct from dynamically excited TNO surfaces in the combination of g, r, and z-bands. • Separating TNOs based on a bimodal distribution is not sufﬁcient to correctly identify red and neutral TNO surfaces classes. • Simultaneous or near-simultaneous photometry is necessary to distinguish the red dynamically excited TNOs from the neutral dynamically excited TNOs. • Photometry in grz can be used to identify TNOs with cold classical surfaces outside the cold classical dynamical region, such as the 2:1 resonance. We target this resonance in our current LBT program. COL-OSSOS RESULTS

Additional papers by the Col-OSSOS Team The Astronomical Journal, 151:158 (7pp), 2016 June Fraser et al.

TRIPPy: TRAILED IMAGE PHOTOMETRY IN PYTHON

Wesley Fraser1, Mike Alexandersen2, Megan E. Schwamb2, Michaël Marsset3, Rosemary E. Pike4, J. J. Kavelaars5, Michele T. Bannister4, Susan Benecchi6, and Audrey Delsanti7 The Astronomical Journal, 151:158 (7pp), 2016 June 1 Fraser etThe al. Astronomical Journal, 151:158 (7pp), 2016 June Fraser et al. Queenʼs UniversityThe Belfast, Astronomical Astrophysics Journal, Research151:158 Center,(7pp), 2016 David June Bates Building, Belfast, BT7 1NN, UK; [email protected] Fraser et al. 2 Institute for Astronomy and Astrophysics, Academia Sinica; 11F AS/NTU, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei 10617, Taiwan 3 European Southern Observatory, Aix Marseille University, CNRS, LAM, France 4 Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 3P6, Canada 5 NRC Herzberg, National Research Council, Canada, 5071 W. Saanich Road, Victoria BC, Canada V9E 2E7 6 Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ, USA, 85719 7 Aix Marseille Université, CNRS, LAM (Laboratoire dʼAstrophysique de Marseille) UMR 7326, 13388 Marseille, France Received 2016 January 29; accepted 2016 March 24; published 2016 May 27

ABSTRACT Photometry of moving sources typically suffers from a reduced signal-to-noise ratio (S/N) or flux measurements biased to incorrect low values through the use of circular apertures. To address this issue, we present the software package, TRIPPy: TRailed Image Photometry in Python. TRIPPy introduces the pill aperture, which is the natural extension of the circular aperture appropriate for linearly trailed sources. The pill shape is a rectangle with two semicircular end-caps and is described by three parameters, the trail length and angle, and the radius. The TRIPPy software package also includes a new technique to generate accurate model point-spread functions (PSFs) and trailed PSFs (TSFs) from stationary background sources in sidereally tracked images. The TSF is merely the convolution of the model PSF, which consists of a moffat profile, and super-sampled lookup table. From the TSF, accurate pill aperture corrections can be estimated as a function of pill radius with an accuracy of 10 mmag for highly trailed sources. Analogous to the use of small circular apertures and associated aperture corrections, small radius pill apertures can be used to preserve S/Ns of low flux sources, with appropriate aperture correction applied to provide an accurate, unbiased flux measurement at all S/Ns. Key words: methods: data analysis – methods: numerical – techniques: photometric

Figure 1. Flux loss of a trailed source measured with circular apertures of radii ′ ′ 1 and 2 FWHM (solid thin and thick curves) vs. trailing length in units of the Figure 4. Example image cutouts of asteroid 105217 (left) and Polonskaya (480 s, r —middle, 240 s, g —right) in the top row, and the residual after removal of each 1. INTRODUCTIONimageʼs TSF in the bottom row. The asteroid is the bright targetlookup in the center table, of the photometry top three images. determined Images are sorted from left to right this in order point-spread of decreasing trail length. image FWHM. The dashed line (right ordinate) presents the S/N ratio between Figure 2. Example of a pill aperture. The full aperture, outlined in solid white, Star PSF Asteroid PSF is the combination of a rectangle ofTrail length lengthsl are, and 3 91 width(3.0 FWHM 2r,),2 with54 ( two2.3 FWHM),function and 1 27 (1.3(PSF FWHM) )fi. TSFtting subtractions method result can in residual be inaccurate. pixels of <10%, <8%, and <5% of the peak the trailed source, and a circular equivalent, both measured with circular The brightness of the solar systempixel valuesʼs of moving each asteroid bodiesʼs image. is All one residual of images contain subtle structure not represented in the stationary source PSF. fl semicircular end-caps of radius r, all rotated at angle α. For aperture Heresubtraction we present a new pill-shapedsubtraction aperture and software apertures large enough to encompass >99% of the source ux. The three the few directly measurable properties of those objects, and can photometry, the background is measured inside a user specified box, and package, TRailed Image Photometry in Python (TRIPPy), vertical lines represent the trailing of objects at 5, 16, and 40 au, observed at provide insight into a body s size, shape, and surface proper- opposition in 0 7 seeing with a 300 s exposure. The unevenness of the flux outside a pill aperture with larger rʼ(butcondition the same thatl). is The impossible image is to a 480 meet s underdesigned even the speci best ficallycorresponds for precision to a source photometry photon noise of uncertainty both moving of ∼1 mmag. fi exposureties. The of asteroid primary 2006, challenge Polonskaya, ofobserving accurate taken on circumstances. 2008photometry January of15 We moving 14:40:25 provide basic tests of this Clearly, even for highly elongated sources, accurate aperture loss curves are due to pixel noise of the arti cial images from which those −1 and stationary sources in sidereally tracked images. Through UTCtargets when the is asteroid a result had a of rate the of motion apparentscenario, of 19 by motion04 planting hr at of arti angle theficial 30 targets°.9. trailed The sources in our images corrections can be measured from the TSF alone. It should be curves were generated. the use of an elongated pill-shaped aperture (a rectangle with peakthemselves. pixels are nearly Typically, 9000 ADU sources brightercontaining are than observed the Polonskaya, background. with the and telescopethen subtracting a source withPublished the noted that with in a AJ pill radii 2016 of r < 2.5, for the extremely high same flux, but slightly adjusted FWHM. Thesetwo experiments semicircular end-caps described by three parameters, the tracked either sidereally or at the apparent motion of the target S/N images of Polonskaya, the aperture correction uncertainty revealed that ∼8% of peak residuals are foundtrail with length FWHM and angle,is the dominantand the source radius of), error, and anand estimate a pill aperture of the with larger r of interest. Either case results in the obfuscation of the target s variations as little as 5%. With thisʼ result inTSF mind, through residual convolutionshould be used. of For the images stationary with S/N < source200 (or PSF, still in the flux fractional flux excluded from circular apertures of 1 and 2 trailed point-spread function (hereafterstructures TSF in trailed), and imageconsequently, subtractions are an inevitable associated aperturelimited corrections regime), however, can be theaccurately uncertainty estimated is dominated by FWHM versus source trail length. In addition, we present the a reduction in the overall photometricconsequence of signal-to-noise the fact that point ratio sources do not preserve a ′ Figure 5.fromStars the used TSF, for largelyPSFsource generation photon mitigating noise, of the andther apertures issuesimage associatedof of smaller Polonskayar will with provide shown the in Figure 4 (top two rows), and their corresponding residuals after PSF removal (bottom effective background-limited decrease in photometric precision (S/N) compared to equivalentlyrecord bright of on-image stationary seeing sources. variations during an exposure. It lowest final uncertainty. The value of r that provides maximal should be noted, however, that trailedtwo subtraction rowscircular). residuals This is aperture will the same photometry. image as that The presented routines in the for top-right both TSF panel of Figure 4. For each star, pixel residuals in the core of each star are <1% the peak brightness of a trailed source compared to the stationary equivalent when Historically, photometry of faint trailed sources is doneof in that star. All images areS/ brightnessN depends on scaled the trail using length,z but-scale. we have found in practice be lower for less trailed sources; the 240generation, s exposures of as wellthat as for pill background and circular images aperture with trail photometry lengths <2 FWHM, an aperture large enough to include >99% of the source flux is the same way as for stationaryPolonskaya sources, have through a peak the residual use of that a is nearly half the 8% 8 are available as a python1.2 < r < package1.6 typically(Fraser provides2016 maximal). TRIPPy S/N. is a utilized. The curves in Figure 1 were measured from ideal small circular aperture, and associatedresidual of aperture the 480 s correction. exposures, and This the longer trailed image In Figure 6, we also present the results when a lookup table 105217 has higher peak residual still at 10%complete of peak pixel photometry package, which includes facilities for trailed sources of various lengths, generated from a moffat procedure suffers from two separate issues. The first issue is the is not used. This facilitates a comparison with the trail-fitting value. the KBO,generation allowing of the circular PSF and apertures TSF, and to bemechanisms used, facilitating for one-third the rate of motion of the asteroid in that image, were fi obvious—but usually neglected—loss of flux due to trailing in method of Vereš et al. (2012) which utilizes a Gaussian profile pro le with FWHM = 5.5 pixels. Despite the modest subtraction residuals,photometry accurate photo- using PSF and TSF source fitting. As well, TRIPPy sidereal images, which is not accounted for by the aperturecomparison of a widewithout range a lookup of photometry table, but otherwise, packages. uses essentially the same considered. The pill aperture photometry was corrected for the As can be seen, as long as the aperture radius is at least as metry for all trailed sources is still afforded byincludes the TSF. This facilities is for pill and circular aperture photometry, and correction measured from stationary sources. This results in an In a lowest rmstechnique sense, to one generate of TSFs the as we highest present here. performing Without the aperture correction measured on frame to provide comparison large as the trailing length in the image, the flux excluded by because accurate aperture corrections can be measuredbackground directly estimation through various techniques, including a under-reporting of the sourcefroms true the TSF.flux. We This demonstrate issue can this be with the extremely high lookup table, the error in the aperture correction estimate is a the use of a circular aperture is no more than ∼5%, a loss that ʼ techniquesnew modal is estimation the factorSExtractor technique of four worse.we MAG present Therefore,_ISOCOR here for for measuring thephotometry most accurate with MAG_ISOCOR, which includes their own corrections. All avoided with the use of an apertureS/N images large enough of Polonskaya to encompass and 105217. Specifically, we can be effectively ignored for low S/N ( 15) measurements. the background inphotometry, crowded thefields. use of We a lookup present table theis required. aperture For sourcesfl measurements at each flux level are normalized by the true flux,  the entire source image, but resultsmeasured in the the second aperture issue corrections with the astechnique. a function of r Thisin the technique attempts to provide full ux Higher precision photometry, however, is possible with standard way, using the TSF, and then directlyshape from the in image Section 2with, the S recipe/N 50, for the PSF lack and of a TSF lookup generation table will cause and a bias in use of circular apertures—a large penalty in S N as a resultFiguremeasurements of 5. Stars used of for a source PSFthe fl generationux by measurement tracing of the larger anr′ image thanisophotal the of amplitude Polonskaya curve of the around photon shown in Figureand4 (top are two presented rows), and their in corresponding Figure 7, residuals along after with PSF the removal mean(bottom knowledge of the TSF, and a reasonable choice in aperture of the asteroids themselves./ The differenceresultant is presented aperture in correction quality in Section 3, and finish inclusion of a larger background region. The scale of′ both noise uncertainty. measurement at each flux level. shape. Figure 6 for one of the 480 s, r imagestwothe of rows source Polonskayawith). This concluding and and is the for measuring same remarks image in photometry as Section that presented4. within in the that top-right aperture. panel of A Figure 4. For each star, pixel residuals in the core of each star are <1% the peak brightness effects is presented in Figure 1one. image of 105217. For completeness, we also include an Recently, Sonnett et al. (2013) presented a comparison of the To that end, we introduce the pill aperture. An example of of that star. All images are brightness scaled using z-scale.fl As can be seen, both produce similar S/Ns at all flux levels. Recently, Vereš et al. (2012estimate) presented of the aperturea technique correction for whentrailcorrection the lookup table is thenis not appliedrelative performances to account of various for the photometryux excludedtechniques in the by this aperture is presented in Figure 2. The pill can be described utilized. As can be seen, for nearly all r, the difference between scenario of moderate S/N observations (20), of a Kuiperfi fi Belt Similiarly, at high S/N levels, both techniques reproduce the fitting of moving sources. Aimed primarily at accuratethat aperture based on a two-dimensional−1 Gaussian pro le t to the aperture corrections measured from the TSF, and that 2. APERTUREObject, moving COMPARISON at 2 8 hr . At the expense of knowledge of as a rectangle with two semicircular end-caps, and is astrometry, their method achieved this by fitting an axisym- correct flux with no appreciable biases. At low S/N, however, characterized by three parameters, which are depicted in measured directly from the asteroidthetheʼs KBO,image source. is lessallowing In than thisthe circular way, PSF and source any apertures aperture elongation corrections, to be the can used, telescope be facilitating was at tracked least one-third the rate of motion of the asteroid in that image, were metric Gaussian profile convolved10 mmag. with In an ar line= 1.4 to FWHM the trailed pillroughly aperture, theTo accounted S/N understand= 889 for,at the a withnon-sidereal issues the associated rate rms to produce uncertainty with acircular(nearly) increasing apertureuntrailed image byof on average, MAG_ISOCOR produces a mean measurement that Figure 2. These parameters are the trail length or how far the source. The apparent rate and angle of motion of a source wascomparisonphotometry of a of wide trailed range sources, of inphotometry Figure 1, we packages. present the isconsidered. biased faintward The pillwhile aperture the pill photometry aperture produces was corrected an unbiased for the target has moved during an exposure, l, the “radius,” r, which solved for, thereby providing extremely accurate astrometry.modestIn a amounts lowest— rms4approximately sense, one 50% of in the the highest case discussed performing by aperture correction measured on frame to provide comparison 8 measurement. For example, the MAG_ISOCORR bias rapidly describes the half-width of the rectangle and the radius of each As we will discuss, however, without the use of an associatedSonnett ethttps: al.//github.com(2013)/.fraserw/TRIPPy fl techniques is the SExtractor MAG_ISOCOR photometry with MAG_ISOCOR, which includes their own corrections. All end-cap, and the angle of trailing on the image, α. Figure 3. Fractional ux error as a function of error in l and α. Curves are fi degrades to ∼3% at S/N∼50. The reason pill photometry shown for l values of 1, 2, 3, and 4 FWHM (solid, dashed, dotted, and dashed– One large dif culty arises in the use of MAG_ISOCOR whenfl measurements at each flux level are normalized by the true flux, Compared with the use of a large circular aperture, the pill fi technique.1 This technique attempts to provide full ux avoids this bias is simple; measurement of the PSF, and aperture avoids both the decrease in S N and flux under- dotted lines, respectively). Small errors in l result in signi cantly largertracing isophotal apertures around low S/N sources. While the / photometric errors compared to small errors in α. measurements of a source by tracing an isophotal curve around estimationand are of presented the TSF afforded in Figure by sidereally7, along tracked with images the mean estimation. For comparison with Figure 1, in the background- S/N of this technique is generally as good or better than other the source and measuring photometry within that aperture. A allowsmeasurement accurate aperture at each fl correctionsux level. to be calculated, at least to limited case, a pill aperture with r = 2.5 FWHM gathers ∼99% techniques, a bias toward measuring a flux lower than the true fl fl correction is then applied to account for the flux excluded by the precisionAs can be demonstrated seen, both produce in Figure similar6. S/Ns at all ux levels. of the source ux, and compared to a large circular aperture, Accurate photometry clearly depends on knowledge of thevalue exists. This is presented in Figure 7 where we compare results in 20% and 100% increases in S/N for trail lengths of trail length, l, and angle, r, in an image. The effects of usingthat aperture based on a two-dimensional Gaussian profile fit to Similiarly, at high S/N levels, both techniques reproduce the simulations of photometry reported by pill aperture photometry fl l = 1 FWHM and l = 4 FWHM, respectively. These S/N incorrect values are presented in Figure 3 where we plotthe source. In this way, source elongation can be at least correct ux with no appreciable biases. At low S/N, however, improvements jump to 100% and 320% for a small pill with fraction of flux contained within an aperture with an incorrectandl that from MAG_ISOCOR. This comparison was made by 3.2. Background Estimation roughly accounted for, with the rms uncertainty increasing by on average, MAG_ISOCOR produces a mean measurement that r = 1.5 FWHM. or α, compared to what it would be with the correct choice inplantingl 50 synthetically elongated Moffat profiles at various isIn biased addition faintward to the while pill aperture, the pill aperture we also produces introduce an a unbiased new modestfl amounts—approximately 50% in the case discussed by 2 ux levels in an image with a background of 1000 ADU, and techniquemeasurement. to estimate For example, the background the MAG_ISOCORR modal value in an bias image. rapidly Sonnettappropriate et al. Gaussian(2013). noise. The Moffat profile extracted from A common technique used to estimate the mode is to take three One large difficulty arises in the use of MAG_ISOCOR when degrades to ∼3% at S/N∼50. The reason pill photometry the first r′ image of asteroid Polonskaya was used. The rate, and timesavoids the medianthis bias value is simple; minus two measurement times the mean of the value PSF, of a and tracing isophotal apertures around low S/N sources. While the estimation of the TSF afforded by sidereally tracked images S/N of this technique is generally as good or better than other 5 allows accurate aperture corrections to be calculated, at least to techniques, a bias toward measuring a flux lower than the true the precision demonstrated in Figure 6. value exists. This is presented in Figure 7 where we compare simulations of photometry reported by pill aperture photometry and that from MAG_ISOCOR. This comparison was made by 3.2. Background Estimation planting 50 synthetically elongated Moffat profiles at various In addition to the pill aperture, we also introduce a new flux levels in an image with a background of 1000 ADU, and technique to estimate the background modal value in an image. appropriate Gaussian noise. The Moffat profile extracted from A common technique used to estimate the mode is to take three the first r′ image of asteroid Polonskaya was used. The rate, and times the median value minus two times the mean value of a

5 Published in Nature Astronomy, 2017 First arrival from afar: the interstellar planetesimal ʻOumuamua

Michele Bannister, M. E. Schwamb, W. C. Fraser, M. • Gemini DD Award Marsset, A. Fitzsimmons, S. Benecchi, P. Lacerda, • Calibrated images released to the R. E. Pike, JJ Kavelaars, A. B. Smith, S. O. Stewart, public within 5 weeks of observations S.-Y. Wang (王祥宇), M. J. Lehner http://doi.org/10.11570/17.0010 Published in ApJL 2017 Col-OSSOS: Color and Inclination are Correlated Throughout the Kuiper Belt Michael Marsset, Wesley C. Fraser, Rosemary E. Pike, Michele T. Bannister, Megan E. Schwamb, Kathryn Volk, J. J. Kavelaars, and OSSOS Core (In prep.)

“Blue” TNOs have larger orbital inclinations than “red” objects OSSOS Survey Simulator: (dynamically hot populations) Not an effect of discovery biases 50 6 35 Blue class Red class TNOs (this work) 30 Model 5 (CFEPS L7) 40 Model (K11) 25 ] 4 ]

30 20

3 Inclination [ 15

Inclination [ 20

2 10

5 10 0.0 0.5 1.0 1.5 1 Normalized Red-to-Blue Ratio

125 62 0 0 Implications: TNO surfaces are primordial and 20 0 20 40 60 Spt. slope [%/(103A)]˚ formed in a heterogeneous protoplanetary disk Col-OSSOS: The Colours of the Outer Solar System Origins Survey

M. Schwamb, M. Bannister, W. Fraser, M. Marsset, R. Pike, J.J. Kavelaars, S. Benecchi, M. Lehner, S.Y. Wang, A. Thirouin, A. Delsanti, N. Peixinho, M. Alexandersen, Y.T. Chen, B. Gladman, S. Gwyn, J.M. Petit, K. Volk

2013 UR15 2016 BP81

700 1000

600 800 Release of Photometry from: 500 400 600 - H block (17 objects)

Pixels Pixels 300 Pixels 400 - L block (18 objects) 200 200 100

0 0 0 100 200 300 400 500 600 700 0 200 400 600 800 1000 Pixels Pixels

g = g 0.139( 0.002) (g r) 0.10 G S ± ⇤ S

0.05

0.00 )

i 0.05 f (

5log 0.10 . 2 + i

g 0.15

0.20

0.25

0.30 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 (g r) S 2.0 1.8 1.6 1.4

(r’-J) . 1 2 Blue Binary 1.0 Cold Classical 0.8 Excited 01.60 0.9 0.8 0.7 Col-OSSOS 0.6 0.5 (r’-z’) Photometry 0.4 0.3 0.2 0.1 2.2 www.colossos.net 2.0 1.8

(u’-g’) 1.6 1.4 1.2 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 Plot: W. Fraser (g’-r’) ~THANK YOU~

Col-OSSOS: www.colossos.net

COL-OSSOS: Z-BAND PHOTOMETRY REVEALS THREE DISTINCT TNO SURFACE TYPES IDENTIFYING COLD CLASSICAL TNO SURFACES Rosemary E. Pike et al. AJ 2017