J/A+A/629/A18 Deep VI photometry of 15 dwarf galaxy candidates (Mueller+, 2019)
The dwarf galaxy satellite system of Centaurus A.
Mueller O., Rejkuba M., Pawlowski M.S., Ibata R., Lelli F., Hilker M.,
Jerjen H.
<Astron. Astrophys. 629, A18 (2019)>
=2019A&A...629A..18M 2019A&A...629A..18M (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Galaxies, photometry
Keywords: galaxies: dwarf - galaxies: luminosity function, mass function -
galaxies: distances and redshifts -
galaxies: groups: individual: NGC 5128
Abstract:
Dwarf galaxy satellite systems are essential probes to test models of
structure formation, making it necessary to establish a census of
dwarf galaxies outside of our own Local Group. We present deep FORS2
VI band images from the ESO Very Large Telescope (VLT) for 15 dwarf
galaxy candidates in the Centaurus group of galaxies. We confirm nine
dwarfs to be members of Cen A by measuring their distances using a
Bayesian approach to determine the tip of the red giant branch
luminosity. We have also fit theoretical isochrones to measure their
mean metallicities. The properties of the new dwarfs are similar to
those in the Local Group in terms of their sizes, luminosities, and
mean metallicities. Within our photometric precision, there is no
evidence of a metallicity spread, but we do observe possible extended
star formation in several galaxies, as evidenced by a population of
asymptotic giant branch stars brighter than the red giant branch tip.
The new dwarfs do not show any signs of tidal disruption. Together
with the recently reported dwarf galaxies by the complementary PISCeS
survey, we study the luminosity function and 3D structure of the
group. By comparing the observed luminosity function to the
high-resolution cosmological simulation IllustrisTNG, we find
agreement within a 90% confidence interval.However, Cen A seems to be
missing its brightest satellites and has an overabundance of the
faintest dwarfs in comparison to its simulated analogs. In terms of
the overall 3D distribution of the observed satellites, we find that
the whole structure is flattened along the line-of-sight, with a
root-mean-square (rms) height of 130kpc and an rms semi-major axis
length of 330kpc. Future distance measurements of the remaining dwarf
galaxy candidates are needed to complete the census of dwarf galaxies
in the Centaurus group.
Description:
The instrument was FORS2 mounted at the Very Large Telescope, using V
and I band filters. The table columns are given for each dwarf
candidate as: RA (deg), Dec (deg), V (mag), V_error (mag), I (mag),
I_error (mag), CHI, sharp
Where no meaningful photometry could be measured, a high value
(99.9999) is given. Note that the .fits files commited to the CDS are
stacked I band images and are only for the purpose of illustration. We
have measured the photometry on the individual images, which are
available through the ESO archive. The magnitudes are given in Vega.
For the candidates which were not resolved, we only provide the
photometry on chip 1. The photometry on chip 2 was mainly used to get
additional data for the background contamination estimation and was
therefore not needed for these false detections.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 80 34 Observation summary for 15 dwarf galaxy
candidates
catalog.dat 89 65174 Photometric catalog
list.dat 112 24 List of fits images
fits/* . 24 Individual fits images
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Dwarf galaxy candidate name
12- 13 I2 h RAh Right ascension (J2000)
15- 16 I2 min RAm Right ascension (J2000)
18- 19 I2 s RAs Right ascension (J2000)
21 A1 --- DE- declination sign (J2000)
22- 23 I2 deg DEd declination (J2000)
25- 26 I2 arcmin DEm declination (J2000)
28- 29 I2 arcsec DEs declination (J2000)
31- 44 A14 --- Obs.date Observation date (DD/DD MMM YYYY)
46- 50 A5 --- Inst Instrument
52- 57 A6 s ExpTime Exposure time
59 A1 --- Filt [VI] Filter used for the observation
61- 64 F4.2 --- Airmass ?=- Mean airmass during the observation
66 A1 --- l_ImgQual Limit flag on ImgQual
67- 79 A13 arcsec ImgQual ?=- Average image quality
80 A1 --- Note [*] *: KK198 V-band exposure on 19 and 20 Apr
was aborted - here we report it for
completeness, but the data was not used
--------------------------------------------------------------------------------
Byte-by-byte Description of file: catalog.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Dwarf galaxy candidate name
12- 16 A5 --- Chip Chip number (chipN)
18- 29 F12.8 deg RAdeg Right ascension (J2000)
31- 42 F12.8 deg DEdeg Declination (J2000)
44- 50 F7.4 mag Vmag ?=99.9999 V magnitude (Vega)
52- 57 F6.4 mag e_Vmag ?=9.9999 rms uncertainty on V magnitude
59- 65 F7.4 mag Imag ?=99.9999 I magnitude (Vega)
67- 72 F6.4 mag e_Imag ?=9.9999 rms uncertainty on I magnitude
74- 80 F7.4 --- chi CHI estimation from DAOPHOT
82- 89 F8.4 --- Sharp Sharp estimation from DAOPHOT
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 24 F5.3 arcsec/pix scale Scale of the image
26- 29 I4 --- Nx Number of pixels along X-axis
31- 33 I3 --- Ny Number of pixels along Y-axis
35- 57 A23 "datime" Obs.date Observation date
59- 62 I4 Kibyte size Size of FITS file
64- 88 A25 --- FileName Name of FITS file, in subdirectory fits
90-112 A23 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Oliver Mueller, oliver.muller(at)astro.unistra.fr
(End) Patricia Vannier [CDS] 12-Aug-2019