280 research outputs found
New distances of unresolved dwarf elliptical galaxies in the vicinity of the Local Group
We present Surface Brightness Fluctuation distances of nine early-type dwarf
galaxies and the S0 galaxy NGC 4150 in the Local Volume based on deep B- and
R-band CCD images obtained with the 2.56 metre Nordic Optical Telescope.
Typically, six stellar fields at various galactocentric distances have been
chosen for each galaxy as appropriately free of foreground stars and other
contaminants, and Fourier analysed to determine the distances, which are found
to lie in the range of 3 to 16 Mpc. The SBF method is thus demonstrated to
efficiently measure distances from the ground with mid-aperture telescopes for
galaxies for which only the tip of the red giant branch method in combination
with the Hubble Space Telescope has been available until now. We obtained the
following distance moduli: 28.11 +/- 0.15 mag (or 4.2 +/- 0.3 Mpc) for UGC
1703, 27.61 +/- 0.17 mag (or 3.3 +/- 0.3 Mpc) for KDG 61, 29.00 +/- 0.27 mag
(or 6.3 +/- 0.8 Mpc) for UGCA 200, 27.74 +/- 0.18 mag (or 3.5 +/- 0.3 Mpc) for
UGC 5442, 30.22 +/- 0.17 mag (or 11.1 +/- 0.9 Mpc) for UGC 5944, 30.79 +/- 0.11
mag (or 14.4 +/- 0.7 Mpc) for NGC 4150, 31.02 +/- 0.25 mag (or 16.0 +/- 1.9
Mpc) for BTS 128, 29.27 +/- 0.16 mag (or 7.1 +/- 0.6 Mpc) for UGC 7639, 30.19
+/- 0.23 mag (or 10.9 +/- 1.2 Mpc) for UGC 8799 with an alternative distance of
30.61 +/- 0.26 mag (or 13.2 +/- 1.7 Mpc), and 29.60 +/- 0.20 mag (or 8.3 +/-
0.8 Mpc) for UGC 8882.Comment: 14 pages, 13 figures (figures 1, 2 and 10 are of reduced quality),
accepted for publication in A&
Deep Near-Infrared Surface Photometry and Properties of Local Volume Dwarf Irregular Galaxies
We present deep H-band surface photometry and analysis of 40 Local Volume
galaxies, a sample primarily composed of dwarf irregulars in the Cen A group,
obtained using the IRIS2 detector at the 3.9m Anglo-Australian Telescope. We
probe to a surface brightness of ~25 mag arcsec, reaching a 40 times
lower stellar density than the Two Micron All Sky Survey (2MASS). Employing
extremely careful and rigorous cleaning techniques to remove contaminating
sources, we perform surface photometry on 33 detected galaxies deriving the
observed total magnitude, effective surface brightness and best fitting
S\'ersic parameters. We make image quality and surface photometry comparisons
to 2MASS and VISTA Hemispheric Survey (VHS) demonstrating that deep targeted
surveys are still the most reliable means of obtaining accurate surface
photometry. We investigate the B-H colours with respect to mass for Local
Volume galaxies, finding that the colours of dwarf irregulars are significantly
varied, eliminating the possibility of using optical-NIR colour transformations
to facilitate comparison to the more widely available optical data sets. The
structure-luminosity relationships are investigated for our `clean' sample of
dwarf irregulars. We demonstrate that a significant fraction of the Local
Volume dwarf irregular population have underlying structural properties similar
to both Local Volume and Virgo Cluster dwarf ellipticals. Linear regressions to
structure-luminosity relationships for the Local Volume galaxies and Virgo
Cluster dwarf ellipticals show significant differences in both slope and
scatter around the established trend lines, suggesting that environment might
regulate the structural scaling relationships of dwarf galaxies in comparison
to their more isolated counterparts.Comment: 27 pages, 14 figures, 5 table
Photometric Properties of Six Local Volume Dwarf Galaxies from Deep Near-Infrared Observations
We have obtained deep near-infrared - (1.25 m), - (1.65m)
and -band (2.15 m) imaging for a sample of six dwarf galaxies
(M_B\ga-17 mag) in the Local Volume (LV, D\la10 Mpc). The sample consists
mainly of early-type dwarf galaxies found in various environments in the LV.
Two galaxies (LEDA 166099 and UGCA 200) in the sample are detected in the
near-infrared for the first time. The deep near-infrared images allow for a
detailed study of the photometric and structural properties of each galaxy. The
surface brightness profiles of the galaxies are detected down to the ~ isophote in the - and -bands, and in
the -band. The total magnitudes of the galaxies are derived in the three
wavelength bands. For the brightest galaxies (M_B\la-15.5 mag) in the sample,
we find that the Two Micron All Sky Survey (2MASS) underestimates the total
magnitudes of these systems by up to \la0.5 mag. The radial surface
brightness profiles of the galaxies are fitted with an exponential (for those
galaxies having a stellar disk) or S\'ersic law to derive the structure of the
underlying stellar component. In particular, the effective surface brightness
() and effective radius () are determined from the analytic fits to
the surface brightness profile. The - colours for the galaxies have
been measured to explore the luminosity-metallicity relation for early-type
dwarfs. In addition, the - colours of the galaxies are used to assess
their evolutionary state relative to other galaxy morphologies. The total
stellar masses of the dwarf galaxies are derived from the -band photometric
measurements. These will later be compared to the dynamical mass estimates for
the galaxies to determine their dark matter content.Comment: 14 pages, 8 figures, submitted to MNRA
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