J/A+A/618/A85 Spectroscopy of 3<z<4 quiescent galaxies (Schreiber+ 2018)
Near infrared spectroscopy and star-formation histories of 3≤z≤4 quiescent
galaxies.
Schreiber C., Glazebrook K., Nanayakkara T., Kacprzak G.G., Labbe I.,
Oesch P., Yuan T., Tran K.-V., Papovich C., Spitler L., Straatman C.
<Astron. Astrophys. 618, A85 (2018)>
=2018A&A...618A..85S 2018A&A...618A..85S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxy catalogs ; Redshifts
Keywords: techniques: spectroscopic - galaxies: evolution -
galaxies: high-redshift - galaxies: statistics
Abstract:
We present Keck-MOSFIRE H and K spectra for a sample of 24 candidate
quiescent galaxies at 3<z<4, identified from their rest-frame UVJ
colors and photometric redshifts in the ZFOURGE and 3DHST surveys.
With median integration times of one hour in H and five in K, we
obtain spectroscopic redshifts for half of the sample, using either
Balmer absorption lines or nebular emission lines. We confirm the high
accuracy of the photometric redshifts for this
spectroscopically-confirmed sample, with a median
|Zphot-Zspec|/(1+Zspec) of 1.2%. Two galaxies turn out to be dusty
Hα emitters at lower redshifts (z<2.5), and these are the only
two detected in the sub-mm with ALMA. High equivalent-width [OIII]
emission is observed in two galaxies, contributing up to 30% of the
K-band flux and mimicking the UVJ colors of an old stellar population.
This implies a failure rate of only 20% for the UVJ selection at these
redshifts. Lastly, Balmer absorption features are identified in four
galaxies, among the brightest of the sample, confirming the absence of
OB stars. We then modeled the spectra and photometry of all quiescent
galaxies with a wide range of star-formation histories. We find
specific star-formation rates (sSFR) lower than 0.15Gyr-1 (a factor
of ten below the main sequence) for all but one galaxy, and lower than
0.01Gyr-1 for half of the sample. These values are consistent with
the observed Hβ and [OII] luminosities, and the ALMA
non-detections. The implied formation histories reveal that these
galaxies have quenched on average 300Myr prior to being observed,
between z=3.5 and 5, and that half of their stars were formed by z∼5.5
with a mean SFR∼300M☉/yr. We finally compared the UVJ selection
to a selection based instead on the sSFR, as measured from the
photometry. We find that galaxies a factor of ten below the main
sequence are 40% more numerous than UVJ-selected quiescent galaxies,
implying that the UVJ selection is pure but incomplete. Current models
fail at reproducing our observations, and underestimate either the
number density of quiescent galaxies by more than an order of
magnitude, or the duration of their quiescence by a factor two.
Overall, these results confirm the existence of an unexpected
population of quiescent galaxies at z>3, and offer the first insights
on their formation histories.
Description:
We have obtained near-infrared spectra of candidate 3<z<4 quiescent
galaxies with Keck-MOSFIRE, to observe rest-frame optical features
such as nebular emission lines and Balmer absorption lines. Here we
provide the outcome of our observations, listing the derived
spectroscopic redshifts and the other physical properties of the
galaxies derived from the spectral modeling. The modeling assumed a
Calzetti et al. (2000ApJ...533..682C 2000ApJ...533..682C ) attenuation curve, solar
metallicity, Chabrier (2003PASP..115..763C 2003PASP..115..763C) stellar initial mass
function, and the Bruzual & Charlot (2003MNRAS.344.1000B 2003MNRAS.344.1000B) stellar
population models. The star-formation histories were drawn from a wide
grid of models, as described in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 192 24 Physical properties of the galaxies
tablea4.dat 74 24 Spectroscopic redshifts
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- ID Composite ID of the galaxy, with format
"CATALOG-FIELD-ID" (G1)
14- 23 F10.6 deg RAdeg Right ascension (J2000)
25- 35 F11.7 deg DEdeg Declination (J2000)
37 A1 --- f_z [0/2] Redshift flag (2)
39- 43 F5.3 --- z Redshift
45- 50 F6.4 --- e_z Upper uncertainty on redshift
52- 57 F6.4 --- E_z Lower uncertainty on redshift
59- 62 F4.2 mag U-V U-V color (AB)
64- 67 F4.2 mag e_U-V Upper uncertainty on U-V color
69- 72 F4.2 mag E_U-V Lower uncertainty on U-V color
74- 77 F4.2 mag V-J V-J color (AB)
79- 82 F4.2 mag e_V-J Upper uncertainty on V-J color
84- 87 F4.2 mag E_V-J Lower uncertainty on V-J color
89- 92 F4.2 10+10Msun Mass Stellar mass in solar units
94- 97 F4.2 10+10Msun e_Mass Upper uncertainty on stellar mass
99-102 F4.2 10+10Msun E_Mass Lower uncertainty on stellar mass
104-106 F3.1 mag Av Attenuation in the V band
108-110 F3.1 mag e_Av Upper uncertainty on attenuation
112-114 F3.1 mag E_Av Lower uncertainty on attenuation
116-120 F5.1 Msun/yr SFR Past star-formation rate averaged over 10Myr
122-126 F5.1 Msun/yr e_SFR Upper uncertainty on SFR
128-132 F5.1 Msun/yr E_SFR Lower uncertainty on SFR
134-137 F4.2 Gyr tq Duration of quiescence
139-142 F4.2 Gyr e_tq Upper uncertainty on quiescence
144-147 F4.2 Gyr E_tq Lower uncertainty on quiescence
149-152 F4.1 --- zf Formation redshift
154-157 F4.1 --- e_zf Upper uncertainty on formation redshift
159-162 F4.1 --- E_zf Lower uncertainty on formation redshift
164-167 F4.2 Gyr tsf Duration of star-forming phase
169-172 F4.2 Gyr e_tsf Upper uncertainty on SF duration
174-177 F4.2 Gyr E_tsf Lower uncertainty on SF duration
179-182 F4.2 [Msun/yr] logSFRp Past average star-formation rate during
SF phase (log)
184-187 F4.2 [Msun/yr] e_logSFRp Upper uncertainty on past average SFR (log)
189-192 F4.2 [Msun/yr] E_logSFRp Lower uncertainty on past average SFR (log)
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Note (2): Redshift flag as follows:
2 = robust spectroscopic redshift
1 = uncertain spectroscopic redshift
0 = photometric redshift
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Byte-by-byte Description of file: tablea4.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- ID Composite ID of the galaxy, with format
"CATALOG-FIELD-ID" (G1)
14 A1 --- f_zs Spectroscopic redshift flag (2)
16- 19 F4.2 --- zp Photometric redshift
21- 24 F4.2 --- e_zp Upper uncertainty on photometric redshift
26- 29 F4.2 --- E_zp Lower uncertainty on photometric redshift
31- 36 F6.4 --- zs Spectroscopic redshift
38- 43 F6.4 --- e_zs Upper uncertainty on spectroscopic redshift
45- 50 F6.4 --- E_zs Lower uncertainty on spectroscopic redshift
52- 56 F5.1 --- deltaz Significance of "zp-zs"
58- 60 I3 % pz Probability that true redshift is
within ±0.01 of zs
62- 64 F3.1 --- chi2 Reduced chi squared of the fit
66 A1 --- Balmer Balmer absorption flag (3)
68- 70 I3 km/s sigma ? Velocity dispersion
72- 74 I3 km/s e_sigma ? Uncertainty on velocity dispersion
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Note (2): Spectroscopic redshift flag as follows:
2 = robust redshift
1 = uncertain redshift
0 = rejected redshift (do not use)
Note (3): Balmer absorption flag as follows:
1 = absorption lines detected
0 = absorption lines not detected
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Global notes:
Note (G1): Composite ID of the galaxy, with format "CATALOG-FIELD-ID".
CATALOG: ZF (ZFOURGE), or 3D (3DHST)
FIELD: COS (COSMOS), EGS, or UDS ID:
numeric ID from the catalog.
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Acknowledgements:
Corentin Schreiber, corentin.schreiber(at)physics.ox.ac.uk
(End) Corentin Schreiber [Univ. Oxford], Patricia Vannier [CDS] 10-Jul-2018