Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.atnf.csiro.au/people/bkoribal/publications/S217_warren.ps Äàòà èçìåíåíèÿ: Fri Oct 17 06:02:19 2003 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 17:26:26 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: m 43

Recycling intergalactic and interstellar matter
IAU Symposium Series, Vol. 217, 2004
Pierre­Alain Duc, Jonathan Braine and Elias Brinks, eds.
The Nature of High H i Mass­to­Light Ratio Galaxies
Bradley E. Warren & Helmut Jerjen
Research School of Astronomy and Astrophysics, Australian National
University, Mount Stromlo Observatory, Cotter Road, Weston ACT
2611, Australia
B¨arbel S. Koribalski
Australia Telescope National Facility, CSIRO, PO Box 76, Epping NSW
1710, Australia
Abstract. We present here the preliminary results of a multi­wavelength
investigation into high H i mass­to­light ratio dwarf galaxies identified in
the HIPASS Bright Galaxy Catalog.
One way to investigate aspects of star formation and galaxy evolution is to
study galaxies which appear to have done little of either, those with excessive
quantities of neutral hydrogen compared to their stellar content. How could such
galaxies, generally low luminosity dwarf galaxies, maintain such a high relative
proportion of gas, where as others have processed most of their gas into stars?
Could the star formation have been impaired or halted in some way? Have they
lacked internal or external stimulation or only recently begun star formation?
The H i Parkes All­Sky Survey (HIPASS) has provided the largest blind
survey of extragalactic neutral hydrogen over the southern sky to date. One
of its first products is the HIPASS Bright Galaxy Catalog (BGC, Koribalski
et al. 2003, AJ submitted) listing the 1000 apparently strongest extragalac­
tic H i sources in the southern hemisphere. A comparison of the BGC H i
data with preliminary optical properties (from LEDA, the Lyon­Meudon Extra­
galactic Database, Paturel et al. 1997, A&AS, 124, 109, http://cismbdm.univ­
lyon1.fr/¸leda/) of the BGC galaxies (Jerjen et al. 2003 in preparation) re­
vealed numerous sources, mostly intrinsically faint dwarf galaxies, with high
H i mass­to­light ratios; three with M HI =LB ? 20 M fi =L fi (ESO505­G007,
ESO215­G?009 and IC4212).
Figure 1(a) shows a plot of M HI =LB for 789 BGC galaxies as a function of
their absolute photographic B magnitude. The plot shows that there is a much
larger spread in M HI =LB for low luminosity (dwarf) galaxies, with some dwarf
galaxies (in the top right corner) having unusually high ratios. We have under­
taken extensive multi­wavelength observations (optical, near­infrared, radio) of
a sample of 20 high and 20 low M HI =LB dwarf galaxies on this plot (filled cir­
cles) using the ANU 2.3m telescope and the Australia Telescope Compact Array
(ATCA). We present here preliminary results from this investigation, some of
the optical (B band photometry) and radio (H i flux and rotation) properties
from three of the objects classified as high M HI =LB galaxies in our initial sam­
1

2 Warren, Jerjen and Koribalski
ple. Optical V RI and infrared JHK bands have also been taken, along with
optical spectra for some galaxies.
Figure 1. (a) The log(M HI =LB ) of 789 BGC galaxies as a function
of absolute B magnitude. Our sample (filled circles) is drawn from all
galaxies with MB;0 ? ­16.5 (mostly dwarf galaxies). The high M HI =LB
sample was drawn from galaxies with M HI =LB ? 3 M fi =L fi (top
right). A control sample has been drawn from galaxies with M HI =LB
! 3 M fi =L fi (bottom right). (b) H i line intensity contour map for
ESO215--G?009 overlaid on a DSS2 red image. Contours levels are at
0.08, 0.16, 0.32, 0.56, 0.88, 1.20 and 1.60 Jy beam \Gamma1 km s \Gamma1 .
Our measured apparent B magnitudes from CCD imaging for all three
galaxies, ESO215--G?009 (16.13 \Sigma 0.07 mag), ESO348--G009 (14.82 \Sigma 0.07 mag)
and MCG--04--02--003 (15.27 \Sigma 0.07 mag), were brighter than those stated in
LEDA (16.43, 16.71, 15.84 mag respectively) based on photographic plates.
The integrated H i flux densities of the three example galaxies are F HI = 104 \Sigma
12, 13.4 \Sigma 2.2, and 16.0 \Sigma 2.5 Jy km s \Gamma1 (BGC). With the ATCA we obtain F HI
= 121.6 \Sigma 0.3, 11.3 \Sigma 0.5, and 16.1 \Sigma 1.8 Jy km s \Gamma1 . Using the ATCA H i flux
and correcting the B magnitudes for galactic extinction (Schlegel et. al. 1998,
ApJ, 500, 525) we obtain H i mass­to­light ratios of 21.3 \Sigma 1.4, 1.36 \Sigma 0.15 and
2.9 \Sigma 0.5 M fi =L fi respectively, compared to the previous photographic plate
estimates of 24.4, 9.2 and 4.8 M fi =L fi .
A study of H i envelopes around low luminosity galaxies on Arecibo by van
Zee, Haynes, & Giovanelli (1995, AJ, 109, 990) claimed to have found numer­
ous high M HI =LB galaxies, including the galaxy H i 0542+05 (the Orion dwarf
galaxy) at 84.1 M fi =L fi . However, Karachentsev & Musella (1996, A&A, 315,
348) using CCD photometry and a better estimate of the high galactic extinc­
tion for this galaxy produced a M HI =LB of just 2.6 M fi =L fi . Similarly two of
our sample galaxies have dropped into the low M HI =LB regime, but ESO215--
G?009 is confirmed as a very high M HI =LB galaxy. A detailed discussion of this
galaxy will appear in an upcoming paper (Warren, Jerjen and Koribalski 2003 in
preparation). Figure 1(b) shows the H i intensity map for ESO215--G?009, the
H i cloud extending to several times the radius of the faint stellar component.