J/ApJ/843/41ivo://CDS.VizieR/J/ApJ/843/41doi:10.26093/cds/vizier.18430041CDSBouwens R.J.Illingworth G.D.Oesch P.A.Atek H.Lam D.Stefanon M.2019-08-22T08:53:47Z2018-03-21T08:27:17ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgalaxy-clustershst-photometrygalaxiesinfrared-sourcesredshiftedWe provide the first observational constraints on the sizes of the faintest galaxies lensed by the Hubble Frontier Fields (HFF) clusters. Ionizing radiation from faint galaxies likely drives cosmic reionization, and the HFF initiative provides a key opportunity to find such galaxies. However, we cannot assess their ionizing emissivity without a robust measurement of their sizes, since this is key to quantifying both their prevalence and the faint- end slope to the UV luminosity function. Here we provide the first size constraints with two new techniques. The first utilizes the fact that the detectability of highly magnified galaxies as a function of shear is very dependent on a galaxy's size. Only the most compact galaxies remain detectable in high-shear regions (versus a larger detectable size range for low shear), a phenomenon we quantify using simulations. Remarkably, however, no correlation is found between the surface density of faint galaxies and the predicted shear, using 87 high-magnification ({mu}=10-100) z~2-8 galaxies seen behind the first four HFF clusters. This can only be the case if faint (~-15mag) galaxies have significantly smaller sizes than more luminous galaxies, i.e., <~30mas or 160-240pc. As a second size probe, we rotate and stack 26 faint high-magnification sources along the major shear axis. Less elongation is found even for objects with an intrinsic half-light radius of 10mas. Together, these results indicate that extremely faint z~2-8 galaxies have near point-source profiles (half-light radii <30mas and perhaps 5-10mas). These results suggest smaller completeness corrections and hence shallower faint-end slopes for the z~2-8 LFs than derived in some recent studies (by {Delta}{alpha}>~0.1-0.3).2017ApJ...843...41Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/843/41CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/hst : HST Archived Exposures Catalog (STScI, 2007)J/ApJ/612/L93 : Candidates of z~5.5-7 galaxies in the HST-UDF (Yan+, 2004)J/AJ/132/1729 : HUDF BVI-dropout sources (Beckwith+, 2006)J/ApJ/754/83 : UV continuum for z~4-7 star-forming gal. (Bouwens+, 2012)J/ApJ/756/164 : UV galaxies in CANDELS from z=8 to z=4 (Finkelstein+, 2012)J/MNRAS/432/2696 : Galaxy luminosity function at z = 7-9 (McLure+, 2013)J/ApJ/762/L30 : MCS J0416.1-2403 strong lensing analysis (Zitrin+, 2013)J/ApJ/793/115 : UV-continuum slopes beta for z~4-8 galaxies (Bouwens+, 2014)J/MNRAS/444/268 : HST Frontier Fields clusters (Richard+, 2014)J/ApJ/800/18 : HST/WFC3 obs. of z~7-8 galaxies in A2744 (Atek+, 2015)J/ApJ/803/34 : z~4-10 galaxies from HST legacy fields (Bouwens+, 2015)J/ApJ/810/71 : UV mag of cand. galaxies at 3~<z~<8.5 (Finkelstein+, 2015)J/MNRAS/452/1437 : Abell 2744 strong-lensing analysis (Jauzac+, 2015)J/ApJS/219/15 : Morphologies of z=0-10 galaxies with HST (Shibuya+, 2015)J/ApJ/801/44 : HST lensing analysis of the CLASH sample (Zitrin+, 2015)J/A+A/590/A31 : ASTRODEEP Frontier Fields Catalogues (Merlin+, 2016)J/ApJ/835/113 : Gal. >~6 from the Hubble Frontier Fields (Livermore+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/843/41https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/843/41http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/843/41https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/843/41https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/843/41http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/843/41GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/843/41/table1 (Samples of high-magnification {mu}=10-100 z=2-8 galaxies found over the first four HFF clusters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/843/41/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/843/41/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/843/41/table1?GETtext/xml+votable180.050000true3.583458-30.3882780.005555555555555556Cone search capability for table J/ApJ/843/41/table2 (Coordinates and other measured properties of z~2-8 sources)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/843/41/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/843/41/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/843/41/table2?GETtext/xml+votable180.050000true3.60107083-30.412252780.0055555555555555566/6383 16486 28448 34793https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/843/41?format=asciiInfrareddefaultJ/ApJ/843/41/table1Samples of high-magnification {mu}=10-100 z=2-8 galaxies found over the first four HFF clustersSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintClusterCluster identificationmeta.id;meta.maincharz2[2/15]? Number of galaxies with z~2meta.numberintnullablez3[2/10]? Number of galaxies with z~3meta.numberintnullablez5[2/10] Number of galaxies with z~5meta.numberintz6[1/7] Number of galaxies with z~6meta.numberintz7[0/3] Number of galaxies with z~7meta.numberintz8[0/2] Number of galaxies with z~8meta.numberintNgNumber of galaxies for this cluster (table 2)meta.numberintnullable_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainJ/ApJ/843/41/table2Coordinates and other measured properties of z~2-8 sourcesIDSource IDmeta.id;meta.maincharprimaryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintClusterCluster identification as in table 1; column added by CDSmeta.id.parentcharHMagSMember of high magnification sample (1)meta.codecharRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainF160mag[24.6/30.2] Measured HST WFC3 F160W AB magnitudemagphot.mag;em.IR.HfloatF160Mag[-21.5/-12.2] Absolute F160W-band AB magnitudemagphys.magAbs;em.UV.100-200nmfloatzphot[1.5/7.7] Photometric redshift estimatesrc.redshiftfloatmagf[1/145] Magnification factor (median of the four parametric models)stat.paramfloatshff[1/47] Shear factor (median of the available models)arith.factorfloatrhl[0.0/2.7]? Circularized half-light radius estimate after correction for lensingkpcphys.size.radiusfloatnullablee_rhl[0.0/4.3]? Uncertainty in rhlkpcstat.errorfloatnullableM16Display data from the ASTRODEEP Frontier Fields Catalogues (Merlin+, 2016, J/A+A/590/A31) within 0.4"meta.ref.urlintnullableSimbadSimbad column added by the CDSmeta.ref.urlchar