J/MNRAS/475/4148 UKIDSS UDS field spectroscopic redshifts (Galametz+, 2018)
Growing up in a megalopolis: environmental effects on galaxy evolution in a
supercluster at z ∼ 0.65 in UKIDSS UDS.
Galametz A., Pentericci L., Castellano M., Mendel T., Hartley W.G.,
Fossati M., Finoguenov A., Almaini O., Beifiori A., Fontana A., Grazian A.,
Scodeggio M., Kocevski D.D.
<Mon. Not. R. Astron. Soc., 475, 4148-4169 (2018)>
=2018MNRAS.475.4148G 2018MNRAS.475.4148G (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxy catalogs ; Redshifts
Keywords: galaxies: clusters: individual: ClG J021734-0513 -
large-scale structure of Universe
Abstract:
We present a large-scale galaxy structure Cl J021734-0513 at z∼0.65
discovered in the UKIDSS UDS field, made of ∼20 galaxy groups and
clusters, spreading over 10Mpc. We report on a VLT/VIMOS
spectroscopic follow-up program that, combined with past spectroscopy,
allowed us to confirm four galaxy clusters (M200∼1014M☉) and
a dozen associated groups and star-forming galaxy overdensities. Two
additional filamentary structures at z∼0.62 and 0.69 and foreground
and background clusters at 0.6<z<0.7 were also confirmed along the
line of sight. The structure subcomponents are at different formation
stages. The clusters have a core dominated by passive galaxies and an
established red sequence. The remaining structures are a mix of
star-forming galaxy overdensities and forming groups. The presence of
quiescent galaxies in the core of the latter shows that
'pre-processing' has already happened before the groups fall into
their more massive neighbours. Our spectroscopy allows us to derive
spectral index measurements e.g. emission/absorption line equivalent
widths, strength of the 4000Å break, valuable to investigate the
star formation history of structure members. Based on these line
measurements, we select a population of 'post-starburst' galaxies.
These galaxies are preferentially found within the virial radius of
clusters, supporting a scenario in which their recent quenching could
be prompted by gas stripping by the dense intracluster medium. We
derive stellar age estimates using Markov Chain Monte Carlo-based
spectral fitting for quiescent galaxies and find a correlation between
ages and colours/stellar masses which favours a top-down formation
scenario of the red sequence. A catalogue of ∼650 redshifts in UDS is
released alongside the paper (via MNRAS online data).
Description:
We restrict the present study to the area covered by both
near-infrared WFCAM UKIDSS UDS data and optical Suprime-Cam data, a
field we will simply refer to as 'UDS' in the rest of the text. We
do not discard the possibility that the large-scale structure studied
in this work may extend beyond the field of study.
We make use of the photometric measurements and photometric redshifts
(zphot) from the CANDELS UDS catalogue (Galametz et al., 2013, Cat.
J/ApJS/206/10; Santini et al., 2015, Cat. J/ApJ/801/97) for sources
within the CANDELS field of view and from the UKIDSS UDS catalogues
for the rest of the field (Almaini et al. in preparation).
The catalogue lists spectroscopic redshifts in the UKIDSS UDS field
obtained with VIMOS during VLT Program ID. 092.A-0833.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 34 35 Clusters/groups candidates at 0.6≤z≤0.7 in
UKIDSS UDS
table2.dat 54 654 VIMOS spectroscopic redshifts in the
UKIDSS UDS field
table3.dat 38 22 Redshift of groups and clusters in UDS
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See also:
J/ApJS/206/10 : CANDELS multiwavelength catalog (Galametz+, 2013)
J/ApJ/801/97 : GOODS-S+UDS stellar mass catalogs from CANDELS (Santini+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- ID Name, UNN or CNN (1)
4 A1 --- n_ID [b] Note (2)
6- 7 I2 h RAh Right ascension (J2000)
9- 10 I2 min RAm Right ascension (J2000)
12- 16 F5.2 s RAs Right ascension (J2000)
18 A1 --- DE- Declination sign (J2000)
19- 20 I2 deg DEd Declination (J2000)
22- 23 I2 arcmin DEm Declination (J2000)
25- 28 F4.1 arcsec DEs Declination (J2000)
30- 34 F5.3 --- zph Photometric redshift
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Note (1): The first ID letter (C or U) indicates if the cluster candidate was
identified within (CANDELS) or out (UKIDSS) of the CANDELS HST field of view.
Note (2): b: U1N indicates the northern extension of the cluster U1 that
corresponds to Finoguenov et al. (2010, Cat. J/MNRAS/403/2063) X-ray-detected
cluster SXDF04XGG (see Section 4). We report here the coordinates of the
X-ray detection and photometric redshift estimate from Finoguenov et al.
(2010, Cat. J/MNRAS/403/2063).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Galaxy name
17- 18 I2 h RAh Right ascension (J2000)
20- 21 I2 min RAm Right ascension (J2000)
23- 27 F5.2 s RAs Right ascension (J2000)
29 A1 --- DE- Declination sign (J2000)
30- 31 I2 deg DEd Declination (J2000)
33- 34 I2 arcmin DEm Declination (J2000)
36- 39 F4.1 arcsec DEs Declination (J2000)
41- 46 F6.4 --- zsp Spectroscopic redshift
48 A1 --- q_zsp Redshift quality flag
50- 54 A5 --- SpType Spectral type flag (1)
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Note (1): Spectral type flag as follows:
E = passive
SF = star-forming
E/SF = passive with little star formation
ST = star
Highz = z > 2 source
AGN = AGN
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 3 A3 --- ID Name, UNN or CNN
4 A1 --- n_ID [cd] Note on ID (1)
9- 10 I2 --- N Number of sources used for first cluster
z calculation
11 A1 --- --- [/]
12 I1 --- N2 ? Number of sources used for second cluster
z calculation
17- 22 F6.4 --- zcl First cluster redshift estimation
24- 29 F6.4 --- e_zcl ? rms uncertainty on zcl
30 A1 --- --- [/]
31- 35 F5.3 --- zcl2 ? Second cluster redshift estimation
38 I1 --- Case [1/4] Method used to derive cluster redshift
estimates (2)
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Note (1): Note as follows:
c = Double-peaked redshift distribution. Source number and redshift are
provided for both peaks.
d = A background galaxy group at z=0.707±0.010 (eight sources) was also
confirmed along the line of sight of U5 (see Fig. 9, red symbols and
secondary peak in the U5 panel of Fig. 11).
Note (2): Methods as follows:
1 = A first estimate of zcluster is obtained from the mean redshift of sources
at 0.6<z<0.7 within 1Mpc of the cluster centre. The sample is then
cleaned from outliers by only considering galaxies with
|Δv|<2000km/s from the first mean redshift estimate; we indeed
expect these galaxy systems to have dispersions below 1000km/s.
A new mean redshift is then rederived (case 1).
zcluster 'case 1' and 'case 2' are adopted for clusters with less than 10
confirmed members. Uncertainties on the redshift estimates are obtained
from the standard deviation of the redshift distribution.
2 = For clusters whose outskirts are contaminated along the line of sight by
fore/background structures (e.g. cluster C7 contaminated by C1), we
restrict the redshift determination to sources within 0.5Mpc of the
centre (case 2).
zcluster 'case 1' and 'case 2' are adopted for clusters with less than 10
confirmed members. Uncertainties on the redshift estimates are obtained
from the standard deviation of the redshift distribution.
3 = In case of alignments of structures along the line of sight, mainly
double-peaked distributions at the cluster position (e.g. clumps C4, C8
etc.), a redshift is estimated for both peaks (case 3).
4 = We perform an iterative estimation of redshift and projected velocity
dispersion for clusters with more than 10 confirmed members (C1, C2, U2,
U9, C3, and U1N). A new zcluster and projected velocity dispersion
σ are obtained from sources within |Δv|<2000km/s of the first
zcluster estimate using, respectively, the biweight location estimator
and the biweight estimate of scale introduced by Beers, Flynn & Gebhardt
(1990AJ....100...32B 1990AJ....100...32B). Uncertainties on zcluster and σ are
estimated using a jackknife estimate following Beers et al.
(1990AJ....100...32B 1990AJ....100...32B)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 08-Apr-2021