J/MNRAS/490/135 Galaxy clusters and groups at z∼1 (Lee+, 2019)
More connected, more active: galaxy clusters and groups at z∼1 and the
connection between their quiescent galaxy fractions and large-scale
environments.
Lee S.-K., Im M., Hyun M., Park B., Kim J.-W., Kim D., Kim Y.
<Mon. Not. R. Astron. Soc., 490, 135-155 (2019)>
=2019MNRAS.490..135L 2019MNRAS.490..135L (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, spectra ; Redshifts ; Optical
Keywords: galaxies: clusters: general - galaxies: evolution -
galaxies: high redshift - galaxies: star formation
Abstract:
High-redshift galaxy clusters, unlike local counterparts, show diverse
star formation activities. However, it is still unclear what keeps
some of the high-redshift clusters active in star formation. To
address this issue, we performed a multiobject spectroscopic
observation of 226 high-redshift (0.8<z<1.3) galaxies in galaxy
cluster candidates and the areas surrounding them. Our spectroscopic
observation reveals six to eight clusters/groups at z∼0.9 and z∼1.3.
The redshift measurements demonstrate the reliability of our
photometric redshift measurements, which in turn gives credibility for
using photometric redshift members for the analysis of large-scale
structures (LSSs). Our investigation of the large-scale environment
(∼10Mpc) surrounding each galaxy cluster reveals LSSs - structures up
to ∼10Mpc scale - around many of, but not all, the confirmed
overdensities and the cluster candidates. We investigate the
correlation between quiescent galaxy fraction of galaxy overdensities
and their surrounding LSSs, with a larger sample of ∼20 overdensities
including photometrically selected overdensities at 0.6<z<0.9.
Interestingly, galaxy overdensities embedded within these extended
LSSs show a lower fraction of quiescent galaxies (∼20 per cent) than
isolated ones at similar redshifts (with a quiescent galaxy fraction
of ∼50 per cent). Furthermore, we find a possible indication that
clusters/groups with a high quiescent galaxy fraction are more
centrally concentrated. Based on these results, we suggest that LSSs
are the main reservoirs of gas and star-forming galaxies to keep
galaxy clusters fresh and extended in size at z∼1.
Description:
Our sample is drawn from high-redshift (0.5<z<2.0) cluster candidates
that are selected from a 0.77deg2 area of the entire UDS field. Our
cluster-finding algorithm is described in Lee et al.
(2015ApJ...810...90L 2015ApJ...810...90L). Briefly, galaxy cluster candidates are selected
as overdense regions, where the galaxy surface number density is
higher than the field value by more than 4σ at each redshift
bin.
We obtain 46 cluster candidates, with halo masses of
log(M200/M☉) in the range of [13.4,14.2]. Among the 46 cluster
candidates, we selected targets for the multiobject spectroscopy using
the Magellan Baade 6.5m Telescope at Las Campanas Observatory, Chile,
based on (1) the SF property - covering a wide range in quiescent
galaxy fraction, (2) redshift - residing at similar redshifts at z∼1,
and (3) their vicinity with each other - to be within the field of
view (FoV) of the Inamori Magellan Areal Camera and Spectrograph
(IMACS; Dressler et al. 2011PASP..123..288D 2011PASP..123..288D) instrument.
Based on these criteria, we select six cluster candidates that show
different quiescent galaxy fractions while residing at similar
redshifts, z∼0.9 and 1.2 as our main targets.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 58 227 Target UDS galaxies for our magellan
spectroscopic observation
table3.dat 89 13 Properties of galaxy clusters/groups
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Galaxy name (UDS-NNNNNN) (1)
12- 19 F8.5 deg RAdeg Right ascension (J2000)
21- 28 F8.5 deg DEdeg Declination (J2000)
30- 35 F6.4 --- zspec ? Spectroscopic redshift
37- 40 A4 --- q_zspec Quality flag on zspec (2)
42- 46 F5.3 --- zphot ? Photometric redshift
48- 52 F5.2 mag Rmag Subaru R-band magnitude
54 A1 --- f_Rmag [a] Flag on Rmag (3)
56- 58 A3 --- Group Cluster/group membership (4)
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Note (1): There are 2 stars included at the end of the table with no name
Note (2): Quality flag as follows:
a = Multiple features
b = Single feature
star = Star (zpec=0.0000)
Note (3): Flag as follows:
a = SDSS r-band magnitude
Note (4): Group as follows:
1-a = UDSOD1-a overdensity at z∼0.875 in UDSOOD1 cluster (7 galaxies)
1-b = UDSOD1-b overdensity at z∼0.920 in UDSOOD1 cluster (8 galaxies)
1-c = UDSOD1-c overdensity at z∼0.963 in UDSOOD1 cluster (5 galaxies)
2-a = UDSOD2-a overdensity at z∼0.840 in UDSOOD2 cluster (5 galaxies)
2-b = UDSOD2-b overdensity at z∼0.865 in UDSOOD2 cluster (6 galaxies)
3 = UDSOD3 overdensity at z∼0.87 (11 galaxies)
4 = UDSOD4 overdensity at z∼1.294 (9 galaxies)
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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- 9 A9 --- Name Cluster/Group Name (UDSODN-a)
11 A1 --- f_Name [b] Flag on Name (1)
13- 20 F8.5 deg RAdeg Right ascension (J2000)
22- 29 F8.5 deg DEdeg Declination (J2000)
31- 36 F6.4 --- zcl Cluster redshift
38- 43 F6.4 --- e_zcl Error on zcl
45- 47 F3.1 Mpc Rproj Projected radius
49- 50 I2 --- Nsp Number of galaxies with spectroscopic
redshift within the projected radius Rproj
52- 53 I2 --- Nsplit ? Total number of galaxies with zspec within
the projected radius Rproj including the
spectroscopic redshifts from literature
55- 58 F4.2 --- wi ? Weight computed as the number of
spectroscopically confirmed members divided
by the sum of the numbers of spectroscopic
members and outliers
60- 63 F4.1 [Msun] logM* ? Logarithm of total stellar mass
65- 68 F4.1 [Msun] logM200 ? Logarithm of halo mass calibrated from the
correlation between total stellar mass and
halo mass of model clusters (see Appendix B)
70- 72 F3.1 [Msun] e_logM200 ? Error on logM200
74- 75 I2 --- Ng ? Number of member galaxies corrected by
applying weights for photo-z selected
members
77- 80 F4.2 --- Fquies ? Quiescent galaxy fraction within R200
82- 84 I3 kpc R200 ? Halo radius calculated from M200
86- 89 F4.2 --- Conc ? Halo concentration
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Note (1): Flag as follows:
b = Properties when two outliers in UDSOD4 are treated as non-members
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 23-Jan-2023