| Virgo, A Laboratory to Study Galaxy Evolution |
| As a dynamically young cluster, Virgo contains numerous candidates going through various environmental effects (e.g. gas stripping or evaporation and interactions with other galaxies or the cluster itself). In order to study details of each mechanism at work, we selected more than 40 spiral galaxies in Virgo to map in the HI, which is often the best tracer for the kinematics. The sample galaxies are spread throughout the cluster and span a wide range in star formation properties, indicating that the sample galaxies are experiencing different effects. My thesis eventually will combine the HI data with deep optical, H-alpha and UV data to investigate how the cluster environment affects galaxies in their morphological type and star formation history. (download Conference proceeding or Poster for workshop "Extra-Planar Gas (2004)" / Poster for "Advanced Lectures on: A Pan-Chromatic View of Clusters of Galaxies and the LSS (2005)"). |
| The stellar Kinematics of Edge-On Spirals with a Boxy/Peanut-Shaped Bulge |
| The stellar kinematics of 30 edge-on spiral galaxies (24 with Boxy or Peanut-shaped bulges, 6 with spheroidal bulges) were obtained from the long-slit spectroscopy data. Profiles of the mean stellar velocity, the velocity dispersion, asymmetric (h3) and symmetric (h4) deviations from a pure Gaussian were derived. The result was compared with the stellar bar diagnostics which were developed by simulations. Here we argue that a majority of B/PS bulges is an edge-on view of a thickened bar (from spheroidal to boxy to peanut shaped depending the viewing angle, from along the line-of-sight to with an intermediate angle to perpendicular to the line-of-sight). We also report the signature of a fast rotating inner stellar disk found in some of the sample (download Paper or Poster). |
| The Origin of Star-Gas Counter-Rotating Disks |
| Gas, rotating opposite to the stars? What causes this and what is the frequency like? In the aforementioned study of edge-on spirals, three galaxies revealed a signature of counter-rotation between the ionized gas ([OIII]) and the stars: two (NGC 1596 and NGC 3203) were newely found and one (NGC 128) was re-confirmed from the previous discovery. Based on the most widely believed explanation (gas accretion or merging of flyby's), we did HI follow-up observations of these galaxies. All of these have nearby galaxies on the sky in similar redshift ranges (except NGC 3203 whose companions do not have known redshifts), which is already suggestive of interation with companions. And guess what we have found...! (in preparation) |
| CO Mapping of Spirals in the Ursa Major Cluster |
| A sample of 22 galaxies in the Ursa Major Cluster has been mapped with NRAO 12-meter (now a.k.a. ARO 12-meter) in the On-The-Fly mapping mode. Our work in complementary of previous extragalactic CO studies since 1) the sample is homogeneous and 2) the galaxies were fully mapped without missing any flux. In this work, we provide not only the global molecular gas properties but also the radial surface density distributions (in preparation; download Posters [IAU197] or [KSSS/KAS]). |
| Low Surface Brightness Galaxies and the Tully-Fisher Relation |
| Is it a fine tuning (in such a way that higher Mass-to-Light potentials produce the correct amount of light for a given rotational velocity) that makes low surface brightness galaxies follow the same Tully-Fisher relation as their high surface brightness counterpart? Or is the fine tuning simply a physical paradox which predicts the existence of strong deviators? This work is based on my first year project at Columbia and there is a nice behind story which is appropriate for "the beer conversation" (download Paper). As a lover of LSBs since then, I want to be a faint-object-hunter and pursue to study their physics. |