84 research outputs found
The SED of the nearby HI-massive LIRG HIZOA J0836-43: from the NIR to the radio domain
HIZOA J0836-43is one of the most HI-massive galaxies in the local (z<0.1)
Universe. Not only are such galaxies extremely rare, but this "coelacanth"
galaxy exhibits characteristics -- in particular its active, inside-out stellar
disk-building -- that appear more typical of past (z ~ 1) star formation, when
large gas fractions were more common. Unlike most local giant HI galaxies, it
is actively star forming. Moreover, the strong infrared emission is not induced
by a merger event or AGN, as is commonly found in other local LIRGs. The galaxy
is suggestive of a scaled-up version of local spiral galaxies; its extended
star formation activity likely being fueled by its large gas reservoir and, as
such, can aid our understanding of star formation in systems expected to
dominate at higher redshifts. The multi-wavelength imaging and spectroscopic
observations that have led to these deductions will be presented. These include
NIR (J H K) and MIR (Spitzer; 3-24micron) imaging and photometry, MIR
spectroscopy, ATCA HI-interferometry and Mopra CO line emission observations.
But no optical data, as the galaxy is heavily obscured due to its location in
Vela behind the Milky Way.Comment: 5 pages, 3 figures, to appear in the proceedings of IAU Symposium
284, "The Spectral Energy Distribution of Galaxies" (SED2011), 5-9 September
2011, Preston, UK, editors R.J. Tuffs & C.C.Popesc
The WISE Extended Source Catalog (WXSC). I. The 100 Largest Galaxies
We present mid-infrared photometry and measured global properties of the 100 largest galaxies in the sky, including the well-studied Magellanic Clouds, Local Group galaxies M31 and M33, the Fornax and Virgo galaxy cluster giants, and many of the most spectacular Messier objects (e.g., M51 and M83). This is the first release of a larger catalog of extended sources as imaged in the mid-infrared, called the Wide-field Infrared Survey Explorer (WISE) Extended Source Catalog (WXSC). In this study, we measure their global attributes, including integrated flux, surface brightness, and radial distribution. The largest of the large are the LMC, SMC, and Andromeda galaxy, which are also the brightest mid-infrared galaxies in the sky. We interrogate the large galaxies using WISE colors, which serve as proxies for four general types of galaxies: bulge-dominated spheroidals, intermediate semi-quiescent disks, star-forming (SF) spirals, and AGN-dominated. The colors reveal a tight "sequence" that spans 5 mag in W2–W3 color, ranging from early to late types and low to high SF activity; we fit the functional form given by . Departures from this sequence may reveal nuclear, starburst, and merging events. Physical properties and luminosity attributes are computed, notably the diameter, aggregate stellar mass, and dust-obscured star formation activity
Probing distant clusters : a pre-SALT photometric study of intermediate redshift galaxy cluster
Includes bibliographical references (p. 273-279)
Kathryns Wheel: A spectacular galaxy collision discovered in the Galactic neighbourhood
We report the discovery of the closest collisional ring galaxy to the Milky
Way. Such rare systems occur due to "bulls-eye" encounters between two
reasonably matched galaxies. The recessional velocity of about 840 km/s is low
enough that it was detected in the AAO/UKST Survey for Galactic H
emission. The distance is only 10.0 Mpc and the main galaxy shows a full ring
of star forming knots, 6.1 kpc in diameter surrounding a quiescent disk. The
smaller assumed "bullet" galaxy also shows vigorous star formation. The
spectacular nature of the object had been overlooked because of its location in
the Galactic plane and proximity to a bright star and even though it is the
60 brightest galaxy in the HI Parkes All Sky Survey (HIPASS) HI
survey.
The overall system has a physical size of 15 kpc, a total mass of
M (stars + HI), a metallicity of
[O/H], and a star formation rate of 0.2-0.5 M\,yr,
making it a Magellanic-type system. Collisional ring galaxies therefore extend
to much lower galaxy masses than commonly assumed. We derive a space density
for such systems of , an order of magnitude
higher than previously estimated. This suggests Kathryn's Wheel is the nearest
such system. We present discovery images, CTIO 4-m telescope narrow-band
follow-up images and spectroscopy for selected emission components. Given its
proximity and modest extinction along the line of sight, this spectacular
system provides an ideal target for future high spatial resolution studies of
such systems and for direct detection of its stellar populations.Comment: 18 pages, 12 figures, accepted for publication in MNRA
Galaxy and Mass Assembly (GAMA): Mid-infrared properties as tracers of galaxy environment
We investigate how different mid-infrared (mid-IR) properties of galaxies are correlated with the environment in which the
galaxies are located. For this purpose, we first study the dependence of galaxy clustering on the absolute magnitude at 3.4 µm and
redshift. Then, we look into the environmental dependence of mid-IR luminosities and the galaxy properties derived from these
luminosities. We also explore how various IR galaxy luminosity selections influence the galaxy clustering measurements. We used a set of W1 (3.4 µm) absolute magnitude (MW1) selected samples from the Galaxy and Mass Assembly (GAMA)
survey matched with mid-IR properties from the Wide-field Infrared Survey Explorer (WISE) in the redshift range 0.07 ≤ z < 0.43.
We computed the galaxy two-point correlation function (2pCF) and compared the clustering lengths between subsamples binned
in MW1 and in redshift. We also measured the marked correlation function (MCF), in which the galaxies are weighted by marks
when measuring clustering statistics, using the luminosities in the WISE W1 to W4 (3.4 to 22 µm) bands as marks. Additionally, we
compared the measurements of MCFs with different estimates of stellar mass and star formation rate (SFR) used as marks. Finally,
we checked how different selections applied to the sample affect the clustering measurements
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