J/A+A/615/A96 VI photometry in 3 dwarf galaxies (Mueller+, 2018)
Distances from the tip of the red giant branch to the dwarf galaxies
dw1335-29 and dw1340-30 in the Centaurus group.
Mueller O., Rejkuba M., Jerjen H.
<Astron. Astrophys. 615, A96 (2018)>
=2018A&A...615A..96M 2018A&A...615A..96M (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Photometry, UBVRI
Keywords: galaxies: distances and redshifts - galaxies: dwarf -
galaxies: clusters: individual: Centaurus group - galaxies: photometry
Abstract:
The abundance and spatial distribution of dwarf galaxies are excellent
empirical benchmarks against which to test models of structure
formation on small scales. The nearby Centaurus group, with its two
subgroups centered on Cen A and M 83, stands out as an important
alternative to the Local Group for scrutinizing cosmological model
predictions in a group of galaxies context.
We have obtained deep optical images of three recently discovered M 83
satellite galaxy candidates with the FORS2 instrument mounted on the
Very Large Telescope. We aim to confirm their group membership and
study their stellar population.
Deep V I-band photometry was used to resolve the brightest stars in
our targets. Artificial star tests are performed to estimate the
completeness and uncertainties of the photometry. The color-magnitude
diagrams reveal the red giant branch (RGB) stars, allowing us to use
the Sobel edge detection method to measure the magnitude of the RGB
tip and thus derive distances and group membership for our targets.
The mean metallicity of the dwarf galaxies were further determined by
fitting BASTI model isochrones to the mean RGB locus.
Description:
Our targets were the three dwarf galaxy candidates dw1325-33,
dw1335-29, and dw1340-30, a subsample from the 16 candidates found by
our team in the M 83 subgroup (Mueller et al., 2015A&A...583A..79M 2015A&A...583A..79M).
In the left column of Fig. 1 we show the discovery images observed
with the wide-field Dark Energy Camera mounted at the prime focus of
the Blanco 4-m telescope at CTIO.
The presented tables in like .raw format are standard matched
photometry files produced by the standalone version of
DAOPHOT2/DAOMASTER (just take-off the # in the first lines).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 71 8 Observation summary for the three dwarf galaxy
candidates
1325-301.dat 79 1955 dw1325-30 VI chip 1 photometric catalog
1335-291.dat 79 2624 dw1335-29 VI chip 1 photometric catalog
1335-292.dat 79 1578 dw1335-29 VI chip 2 photometric catalog
1340-301.dat 79 2618 dw1340-30 VI chip 1 photometric catalog
1340-302.dat 79 2224 dw1340-30 VI chip 2 photometric catalog
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy name
11- 12 I2 h RAh Right ascension (J2000)
14- 15 I2 min RAm Right ascension (J2000)
17- 18 I2 s RAs Right ascension (J2000)
20 A1 --- DE- Declination sign (J2000)
21- 22 I2 deg DEd Declination (J2000)
24- 25 I2 arcmin DEm Declination (J2000)
27- 28 I2 arcsec DEs Declination (J2000)
30- 43 A14 --- Date Observing date
45- 49 A5 --- Inst Instrument
51- 56 A6 s TExp Exposure time
58 A1 --- Filter [VI] Filter used for the observation
60- 63 F4.2 --- Airmass Mean airmass during the observation
65- 71 A7 arcsec Qimg Average image quality measured on images
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Byte-by-byte Description of file (#): 1325-30?.dat 1335-29?.dat 1340-30?.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- ID Star identification number
9- 16 F8.3 pix Xpos X position on the cropped chip (1)
19- 25 F7.3 pix Ypos Y position on the cropped chip (1)
28- 34 F7.4 mag Vmag ?=99.9999 V band magnitude with zeropoint=25mag
38- 43 F6.4 mag e_Vmag ?=9.9999 V band magnitude error
46- 52 F7.4 mag Imag ?=99.9999 I band magnitude with zeropoint=25mag
56- 61 F6.4 mag e_Imag ?=9.9999 I band magnitude error
64- 70 F7.4 --- Chi ?=99.9999 CHI value
73- 79 F7.4 --- Sharp ?=9.9999 Sharpness value
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Note (1): The cropping was performed with IRAFs imcopy command with
X=200:1800, Y=10:960 on Chip 1 and X=200:1800, Y=320:1020 on Chip 2.
1 pix = 0.25".
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Acknowledgements:
Olivier Mueller, oliver89.mueller(at)unibas.ch
(End) Patricia Vannier [CDS] 27-Jul-2018