184 research outputs found
High-resolution UKIRT observations of circumnuclear star formation in M100
We present high-resolution, near-infrared imaging of the circumnuclear region
of the barred spiral galaxy M100 (=NGC 4321), accompanied by near-infrared
spectroscopy. We identify a total of 43 distinct regions in the K-band image,
and determine magnitudes and colours for 41 of them. By comparison with other
near-infrared maps we also derive colour excesses and K-band extinctions for
the knots. Combining the imaging and spectroscopic results, we conclude that
the knots are the result of bursts of star formation within the last 15-25 Myr.
We discuss the implications of these new results for our dynamical and
evolutionary understanding of this galaxy.Comment: 10 pages, 4 figures, uses mn-1.4.sty. Accepted for publication in
Monthly Notices of the Royal Astronomical Societ
A postmortem investigation of the Type IIb supernova 2001ig
We present images taken with the GMOS instrument on Gemini-South, in
excellent (<0.5 arcsec) seeing, of SN 2001ig in NGC 7424, ~1000 days after
explosion. A point source seen at the site of the SN is shown to have colours
inconsistent with being an H II region or a SN 1993J-like remnant, but can be
matched to a late-B through late-F supergiant with A_V<1. We believe this
object is the massive binary companion responsible for periodic modulation in
mass loss material around the Wolf-Rayet progenitor which gave rise to
significant structure in the SN radio light curve.Comment: 5 pages, 3 figures. Accepted for publication in MNRAS Letters. Fig. 1
resolution degraded to meet size limitations; full resolution version
available from http://www.aao.gov.au/local/www/sdr/pubs/sn2001ig_gmos.ps.g
Neutral Hydrogen in the Ringed Barred Galaxies NGC 1433 and NGC 6300
We have made observations of the \ion{H}{1} in the southern ringed barred
spiral galaxies NGC~1433 and NGC~6300 with the Australia Telescope Compact
Array (ATCA), the main goal being to test the resonance theory for the origin
of these rings. NGC~1433 is the prototypical ringed barred spiral, and displays
distinct \ion{H}{1}~counterparts to its nuclear ring, inner ring, outer
pseudoring, and plume-like features. The and regions at
corotation, as well as the bar itself, are relatively devoid of neutral atomic
hydrogen. By associating the inner ring of NGC~1433 with the inner second
harmonic resonance, and its outer pseudoring with the outer Lindblad resonance,
we are able to infer a bar pattern speed for NGC~1433 of
~km~s~kpc. By way of contrast, NGC~6300 possesses a much
more extended \ion{H}{1}~disk than NGC~1433. There is a gas ring underlying the
inner pseudoring, but it is both broader and slightly larger in diameter than
the optical feature. By again linking this inner ring feature to the inner
second harmonic resonance, we derive a bar pattern speed for NGC~6300 of
~km~s~kpc, but in this case, neither the outer pseudoring
nor the nuclear ring predicted by the resonance-ring theory can be identified
in NGC~6300. Although it may be the case that the ring in NGC~6300 is not
related to a resonance with the bar at all, we postulate instead that NGC~6300
is merely a less well-developed example of a resonance-ring galaxy than is
NGC~1433.Comment: 21 pages, aas2pp4 LaTeX, no figures included. Accepted for April 1
1996 ApJ. Full paper (with figures) available from
http://www.phys.unsw.edu.au/~sdr/prep.htm
UNSWIRF: A Tunable Imaging Spectrometer for the Near-Infrared
We describe the specifications, characteristics, calibration, and analysis of
data from the University of New South Wales Infrared Fabry-Perot (UNSWIRF)
etalon. UNSWIRF is a near-infrared tunable imaging spectrometer, used primarily
in conjunction with IRIS on the AAT, but suitable for use as a visitor
instrument at other telescopes. The etalon delivers a resolving power in excess
of 4000 (corresponding to a velocity resolution ~75 km/s), and allows imaging
of fields up to 100" in diameter on the AAT at any wavelength between 1.5 and
2.4 microns for which suitable blocking filters are available.Comment: 16 pages, 10 figures, uses psfig.sty and html.sty (included). To
appear in Publications of the Astronomical Society of Australi
Ultraviolet Detection of the Binary Companion to the Type IIb SN 2001ig
We present HST/WFC3 ultraviolet imaging in the F275W and F336W bands of the
Type IIb SN 2001ig at an age of more than 14 years. A clear point source is
detected at the site of the explosion having and
mag. Despite weak constraints on both the
distance to the host galaxy NGC 7424 and the line-of-sight reddening to the
supernova, this source matches the characteristics of an early B-type main
sequence star having K and . A BPASS v2.1 binary evolution model, with
primary and secondary masses of 13 M and 9 M respectively,
is found to resemble simultaneously in the Hertzsprung-Russell diagram both the
observed location of this surviving companion, and the primary star
evolutionary endpoints for other Type IIb supernovae. This same model exhibits
highly variable late-stage mass loss, as expected from the behavior of the
radio light curves. A Gemini/GMOS optical spectrum at an age of 6 years reveals
a narrow He II emission line, indicative of continuing interaction with a dense
circumstellar medium at large radii from the progenitor. We review our findings
on SN 2001ig in the context of binary evolution channels for stripped-envelope
supernovae. Owing to the uncrowded nature of its environment in the
ultraviolet, this study of SN 2001ig represents one of the cleanest detections
to date of a surviving binary companion to a Type IIb supernova.Comment: 8 pages, 3 figures. Resubmitted to ApJ after minor changes requested
by refere
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