J/MNRAS/464/183 Segregation effects in DEEP2 galaxy groups (Nascimento+, 2017)
Segregation effects in DEEP2 galaxy groups.
Nascimento R.S., Ribeiro A.L.B., Lopes P.A.A.
<Mon. Not. R. Astron. Soc., 464, 183-193 (2017)>
=2017MNRAS.464..183N 2017MNRAS.464..183N (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Velocity dispersion ; Redshifts
Keywords: Galaxy: evolution - galaxies: groups: general -
galaxies: high-redshift
Abstract:
We investigate segregation phenomena in galaxy groups in the range of
0.2<z<1. We study a sample of groups selected from the 4th Data
Release of the DEEP2 galaxy redshift survey. We used only groups with
at least eight members within a radius of 4 Mpc. Outliers were removed
with the shifting gapper technique and, then, the virial properties
were estimated for each group. The sample was divided into two stacked
systems: low(z≤0.6) and high (z>0.6) redshift groups.
Assuming that the colour index (U-B)0 can be used as a proxy for
the galaxy type, we found that the fraction of blue (star-forming)
objects is higher in the high-z sample, with blue objects being
dominant at MB>-19.5 for both samples, and red objects being
dominant at MB←19.5 only for the low-z sample. Also, the radial
variation of the red fraction indicates that there are more red
objects with R<R200 in the low-z sample than in the high-z sample.
Our analysis indicates statistical evidence of kinematic segregation,
at the 99 per cent c.l., for the low-z sample: redder and brighter
galaxies present lower velocity dispersions than bluer and fainter
ones. We also find a weaker evidence for spatial segregation between
red and blue objects, at the 70 per cent c.l. The analysis of the
high-z sample reveals a different result: red and blue galaxies have
velocity dispersion distributions not statistically distinct, although
redder objects are more concentrated than the bluer ones at the 95 per
cent c.l. From the comparison of blue/red and bright/faint fractions,
and considering the approximate lookback time-scale between the two
samples (∼3Gyr), our results are consistent with a scenario
where bright red galaxies had time to reach energy equipartition,
while faint blue/red galaxies in the outskirts infall to the inner
parts of the groups, thus reducing spatial segregation from z∼0.8 to
z∼0.4.
Description:
The DEEP2 Galaxy Redshift Survey (Newman et al., 2013ApJS..208....5N 2013ApJS..208....5N)
is considered the largest spectroscopic survey of homogeneously
selected galaxies at z∼1. The survey covers a total area of 2.8
deg2 distributed across four fields observed up to limiting magnitude
RAB=24.1.
We make a virial analysis of the DEEP2 group sample (Gerke et al.,
2012, Cat. J/ApJ/751/50)
The results of the virial analysis are listed in Table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 175 221 Velocity dispersion, characteristic radii and
masses of DEEP2 groups
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See also:
J/ApJ/751/50 : Galaxy groups catalog from DEEP2 Redshift Survey (Gerke+ 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID [1/2321] Sequential number
6- 15 F10.6 deg RAdeg Right ascension (J2000)
17- 25 F9.6 deg DEdeg Declination (J2000)
27- 34 F8.6 --- z Redshift
36- 42 F7.3 km/s sigma Velocity dispersion
45- 51 F7.3 km/s e_sigma Error on sigma (lower value)
53- 59 F7.3 km/s E_sigma Error on sigma (upper value)
61- 63 I3 --- o_sigma Number of galaxies used to compute the
velocity dispersion
65- 72 F8.6 Mpc R500 Radius within which the mean over-density of
the cluster is 500 times the critical density
at the cluster redshift
75- 82 F8.6 Mpc e_R500 Error on R500 (lower value)
84- 91 F8.6 Mpc E_R500 Error on R500 (upper value)
93-100 F8.6 10+14Msun M500 Mass for a radius of R500
103-110 F8.6 10+14Msun e_M500 Error on M500 (lower value)
112-119 F8.6 10+14Msun E_M500 Error on M500 (upper value)
121-128 F8.6 Mpc R200 Radius within which the mean over-density of
the cluster is 200 times the critical density
at the cluster redshift
131-138 F8.6 Mpc e_R200 Error on R200 (lower value)
140-147 F8.6 Mpc E_R200 Error on R200 (upper value)
149-156 F8.6 10+14Msun M200 Mass for a radius of R200
159-166 F8.6 10+14Msun e_M200 Error on M200 (lower value)
168-175 F8.6 10+14Msun E_M200 Error on M200 (upper value)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 15-May-2018