J/ApJ/883/157 Spectrophotometric redshifts of GOODS galaxies (Joshi+, 2019)
Spectrophotometric redshifts for z∼1 galaxies and predictions for number
densities with WFIRST and Euclid.
Joshi B.A., Cohen S., Windhorst R.A., Jansen R., Pirzkal N., Hathi N.P.
<Astrophys. J., 883, 157 (2019)>
=2019ApJ...883..157J 2019ApJ...883..157J
ADC_Keywords: Galaxies, spectra; Photometry, HST; Redshifts; Surveys; Optical
Keywords: galaxies: distances and redshifts ; galaxies: evolution ;
galaxies: high-redshift
Abstract:
We investigate the accuracy of 4000Å/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
(σΔz/(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
|Δz/(1+zs)|≤0.02. We predict ∼700-4400 galaxies degree-2
for galaxies with D4000>1.1 and |Δz/(1+zs)|≤0.02 to a
limiting depth of iAB=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
4000Å/Balmer breaks or the presence of emission lines within the
grism spectra.
Description:
We use slitless spectroscopy obtained with the HST as part of the
Probing Evolution And Reionization Spectroscopically (PEARS;
Ferreras+ 2009, J/ApJ/706/158) survey (GO 10530; PI--S. Malhotra). The
PEARS survey was awarded 200 orbits in Cycle 14 to cover eight fields
in the Great Observatories Origins Deep Survey (GOODS) north (GOODS-N)
and south (GOODS-S) regions to a depth of z'AB≤27mag with the
ACS/WFC G800L grism. A ninth ultra-deep field to z'AB≲28mag
overlaps the Hubble Ultra Deep Field (HUDF). The total area covered is
∼119arcmin2. The ACS G800L grism nominally covers 0.55-1.05um for a
resolution of R∼100 at best.
We matched the PEARS master catalogs (using a matching radius of 0.3")
with photometry catalogs from the 3D-HST survey
(see Skelton+ 2014, J/ApJS/214/24) and our catalog of ground-based
spectroscopic redshifts in the GOODS regions.
This gives us all galaxies that have measured photometry, grism
spectra, and ground-based spectroscopic redshifts. See Section 3.2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 114 497 Redshift and D4000 catalog for our sample
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See also:
II/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)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- PEARS [12378/135087] PEARS identifier
8- 14 A7 --- Field Field identifier ("GOODS-N" or "GOODS-S")
16- 26 F11.7 deg RAdeg [53/189.5] Right Ascension (J2000)
28- 37 F10.6 deg DEdeg [-28/62.4] Declination (J2000)
39- 43 F5.3 --- zspec [0.6/1.3] Redshift from spectroscopy
45- 48 F4.2 --- zphot [0.36/1.5] Redshift from photometry
50- 53 F4.2 --- e_zphot [0/0.4] Lower uncertainty in zphot
55- 58 F4.2 --- E_zphot [0/0.2] Upper uncertainty in zphot
60- 63 F4.2 --- zgrism [0.3/1.5] Redshift from HST ACS/WFC G800L grism
data
65- 68 F4.2 --- e_zgrism [0/1.18] Lower uncertainty in zgrism
70- 73 F4.2 --- E_zgrism [0/1.14] Upper uncertainty in zgrism
75- 78 F4.2 --- zSPZ [0.3/1.5] Redshift from
this spectrophotometric technique
80- 83 F4.2 --- e_zSPZ [0/0.4] Lower uncertainty in zSPZ
85- 88 F4.2 --- E_zSPZ [0/0.21] Upper uncertainty in zSPZ
90- 96 F7.2 --- N [36.9/1689.6] Net Spectral Significance
98-103 F6.4 --- D4000 [1.1/2] D4000 value (1)
105-108 F4.2 --- e_D4000 [0.03/0.41] Uncertainty in D4000
110-114 F5.2 mag imag [19.88/25.13] Apparent i band AB magnitude
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Note (1): In this work, the 4000Å break is measured by the D4000
(Bruzual 1983ApJ...273..105B 1983ApJ...273..105B ; Hamilton 1985ApJ...297..371H 1985ApJ...297..371H), as
opposed to the Dn4000 index. See Section 3.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 09-Mar-2021