J/ApJ/883/157ivo://CDS.VizieR/J/ApJ/883/157doi:10.26093/cds/vizier.18830157CDSJoshi B.A.Cohen S.Windhorst R.A.Jansen R.Pirzkal N.Hathi N.P.2022-08-09T13:53:19Z2021-04-12T09:09:30ZCDS support team

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

cds-question@unistra.frgalaxiesspectroscopyhst-photometryredshiftedsurveysvisible-astronomyWe investigate the accuracy of 4000{AA}/Balmer-break based redshifts by combining Hubble Space Telescope (HST) grism data with photometry. The grism spectra are from the Probing Evolution And Reionization Spectroscopically survey with HST using the G800L grism on the Advanced Camera for Surveys. The photometric data come from a compilation by the 3D-HST collaboration of imaging from multiple surveys (notably, the Cosmic Assembly Near-infrared Deep Extragalactic Survey (CANDELS) and 3D-HST). We show evidence that spectrophotometric redshifts (SPZs) typically improve the accuracy of photometric redshifts by ~17%-60%. Our SPZ method is a template-fitting-based routine that accounts for correlated data between neighboring points within grism spectra via the covariance matrix formalism and also accounts for galaxy morphology along the dispersion direction. We show that the robustness of the SPZ is directly related to the fidelity of the D4000 measurement. We also estimate the accuracy of continuum-based redshifts, i.e., for galaxies that do not contain strong emission lines, based on the grism data alone ({sigma}_{Delta}z/(1+z)_^NMAD^<~0.06). Given that future space-based observatories like Wide Field InfraRed Survey Telescope and Euclid will spend a significant fraction of time on slitless spectroscopic observations, we estimate number densities for objects with |{Delta}z/(1+z_s_)|<=0.02. We predict ~700-4400 galaxies degree^-2^ for galaxies with D4000>1.1 and |{Delta}z/(1+z_s_)|<=0.02 to a limiting depth of i_AB_=24mag. This is especially important in the absence of an accompanying rich photometric data set like the existing one for the CANDELS fields, where redshift accuracy from future surveys will rely only on the presence of a feature like the 4000{AA}/Balmer breaks or the presence of emission lines within the grism spectra.2019ApJ...883..157Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/883/157CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/261 : GOODS initial results (Giavalisco+, 2004)II/318 : GOODS Source Catalogs release r2.0z (Giavalisco+ 2008)J/A+A/454/423 : GOODS-South Field VLT/FORS2 redshifts. II. (Vanzella+, 2006)J/AJ/132/1729 : HUDF BVI-dropout sources (Beckwith+, 2006)J/ApJ/668/839 : Spectrophotometric redshifts for HUDF galaxies (Ryan+, 2007)J/ApJ/706/158 : Early-type galaxies in PEARS (Ferreras+, 2009)J/AJ/138/1022 : Emission-line gal. from HST PEARS survey (Straughn+, 2009)J/ApJ/742/3 : Photometric catalogs for ECDF-S and CDF-N (Rafferty+, 2011)J/MNRAS/413/971 : Galaxy And Mass Assembly (GAMA) DR1 (Driver+, 2011)J/AJ/141/64 : PEARS emission-line galaxies spectroscopy (Xia+, 2011)J/ApJS/207/24 : GOODS-S CANDELS multiwavelength catalog (Guo+, 2013)J/ApJ/772/48 : Emission-line galaxies from PEARS. II. (Pirzkal+, 2013)J/ApJ/796/60 : ECDFS galaxies phot. redshifts & counterparts (Hsu+, 2014)J/ApJS/214/24 : 3D-HST+CANDELS catalog (Skelton+, 2014)J/ApJ/810/71 : UV mag of cand. galaxies at 3~<z~<8.5 (Finkelstein+, 2015)J/ApJ/801/97 : GOODS-S & UDS stellar masses from CANDELS (Santini+, 2015)J/ApJ/830/51 : FourStar gal. evolution survey (ZFOURGE) (Straatman+, 2016)J/ApJS/225/27 : 3D-HST Survey: grism spectra (Momcheva+, 2016)J/ApJ/835/153 : Galaxy env. in the 3D-HST fields (z=0.5-3) (Fossati+, 2017)J/MNRAS/472/4878 : Number counts predictions for surveys (Valentino+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/883/157https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/883/157http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/883/157https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/883/157https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/883/157http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/883/157GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/883/157/table3 (Redshift and D4000 catalog for our sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/883/157/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/883/157/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/883/157/table3?GETtext/xml+votable180.050000true53.1845635-27.836041110.0055555555555555566/11252 35935https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/883/157?format=asciiOpticaldefaultJ/ApJ/883/157/table3Redshift and D4000 catalog for our sampleSimbadNameSimbad column added by the CDSmeta.idcharnullableN[36.9/1689.6] Net Spectral Significancestat.fit.goodnessfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPEARS[12378/135087] PEARS identifiermeta.id;meta.mainintFieldField identifier ("GOODS-N" or "GOODS-S")meta.id;obs.fieldcharRAJ2000[53/189.5] Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[-28/62.4] Declination (J2000)degpos.eq.dec;meta.mainzspec[0.6/1.3] Redshift from spectroscopysrc.redshiftfloatzphot[0.36/1.5] Redshift from photometrysrc.redshiftfloate_zphot[0/0.4] Lower uncertainty in zphotstat.errorfloatE_zphot[0/0.2] Upper uncertainty in zphotstat.error;stat.maxfloatzgrism[0.3/1.5] Redshift from HST ACS/WFC G800L grism datasrc.redshift;pos.heliocentricfloate_zgrism[0/1.18] Lower uncertainty in zgrismstat.errorfloatE_zgrism[0/1.14] Upper uncertainty in zgrismstat.error;stat.maxfloatzSPZ[0.3/1.5] Redshift from this spectrophotometric techniquesrc.redshift;pos.heliocentricfloate_zSPZ[0/0.4] Lower uncertainty in zSPZstat.errorfloatE_zSPZ[0/0.21] Upper uncertainty in zSPZstat.error;stat.maxfloatD4000[1.1/2] D4000 value (1)spect.indexfloate_D4000[0.03/0.41] Uncertainty in D4000stat.errorfloatimag[19.88/25.13] Apparent i band AB magnitudemagphot.mag;em.opt.IfloatPCatDisplay PEARS data from Ferreras+, 2009, J/ApJ/706/158 and Pirzkal+, 2013, J/ApJ/772/48meta.ref.urlintnullableS14Display the 3D-HST+CANDELS data from Skelton+, 2014, J/ApJS/214/24 within 0.3"meta.ref.urlcharGOODSDisplay the GOODS data release 2 (II/318) within 0.3"meta.ref.urlchar