J/MNRAS/478/5336 z-low satellite galaxies in COSMOS survey (Xi+, 2018)
Quantifying the abundance of faint, low-redshift satellite galaxies in the
COSMOS survey.
Xi C., Taylor J.E., Massey R.J., Rhodes J., Koekemoer A., Salvato M.
<Mon. Not. R. Astron. Soc., 478, 5336-5355 (2018)>
=2018MNRAS.478.5336X 2018MNRAS.478.5336X (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Photometry ; Redshifts
Keywords: dark matter - galaxies: dwarf - galaxies: formation -
galaxies: groups: general - Local Group -
galaxies: luminosity function, mass function
Abstract:
Faint dwarf satellite galaxies are important as tracers of small-scale
structure, but remain poorly characterized outside the Local Group,
due to the difficulty of identifying them consistently at larger
distances. We review a recently proposed method for estimating the
average satellite population around a given sample of nearby bright
galaxies, using a combination of size and magnitude cuts (to select
low-redshift dwarf galaxies preferentially) and clustering
measurements (to estimate the fraction of true satellites in the cut
sample). We test this method using the high-precision photometric
redshift catalogue of the COSMOS survey, exploring the effect of
specific cuts on the clustering signal. The most effective of the
size-magnitude cuts considered recover the clustering signal around
low-redshift primaries (z<0.15) with about two-thirds of the signal
and 80 per cent of the signal-to-noise ratio obtainable using the full
COSMOS photometric redshifts. These cuts are also fairly efficient,
with more than one-third of the selected objects being clustered
satellites. We conclude that structural selection represents a useful
tool in characterizing dwarf populations to fainter magnitudes and/or
over larger areas than are feasible with spectroscopic surveys. In
reviewing the low-redshift content of the COSMOS field, we also note
the existence of several dozen objects that appear resolved or
partially resolved in the HST imaging, and are confirmed to be local
(at distances of ∼250Mpc or less) by their photometric or
spectroscopic redshifts. This underlines the potential for future
space-based surveys to reveal local populations of intrinsically faint
galaxies through imaging alone.
Description:
Table A1 lists the IDs, coordinates, redshifts, and magnitudes of the
serendipitous discoveries, sorted by class.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 82 74 Serendipitous catalogue of nearby objects
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See also:
J/ApJS/224/24 : The COSMOS2015 catalog (Laigle+, 2016)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1 I1 --- Class [1/7] Visual class (1)
3- 9 I7 --- COSMOS2015 ? ID from the COSMOS 2015 catalogue
(where available, Laigle et al.,
2016ApJS..224...24L 2016ApJS..224...24L, Cat. J/ApJS/224/24)
10 A1 --- n_COSMOS2015 [m] m for masked
12- 19 F8.4 deg RAdeg Right ascension (J2000)
21- 26 F6.4 deg DEdeg Declination (J2000)
28- 32 F5.3 --- z Redshift
34- 38 F5.3 --- e_z ? Redshift error (only for objects with
photometric redshifts)
40- 44 F5.2 mag i+mag Apparent i±band magnitude
45 A1 --- n_i+mag [+] + for SDSS i-band model magnitude
47- 51 F5.1 mag i+MAG Approximate absolute magnitude in i±band (2)
53- 82 A30 --- Com Comments
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Note (1): Visual classes as follows:
1 = Class 1 objects contain many clearly recognizable point sources,
which together account for a significant fraction of their light.
The implication is that they are close enough to be resolved into
regions dominated by individual bright stars in the COSMOS ACS images
(which have a resolution of approximately 0.095" in F814W -
cf. Koekemoer et al., 2007ApJS..172..196K 2007ApJS..172..196K).
2 = Class 2 may be resolved or partially resolved into point sources,
but are less distinct than Class 1.
3 = Class 3 objects appear to be high surface-brightness galaxies at
larger distances, but still close enough to have visible HII regions
and the like.
4 = Class 4 objects are large and extremely LSB, suggesting some or all may
be local LSB dwarfs.
5 = Class 5 objects appear to be distant galaxies whose light is
significantly contaminated by a single bright galactic star
superposed on the galaxy.
6 = Class 6 objects are LSB galaxies with a few superposed point sources
that may or may not be foreground galactic stars.
7 = Class 7 includes all other strange or unusual objects that look like
they might be nearby.
Repeated visual searches suggest classes 1 & 2 are reasonably complete,
while classes 3-7 contain only a few representative examples of the
many objects of this kind.
Note (2): assuming a distance D=cz/H0 with H0=0.678).
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 28-Oct-2021