List of Past LMA/CARMA Seminars : 01-Jan-2005 to 01-Jun-2005

Date:   Monday 24-Jan-2005
Speaker:   Dr. Min S. Yun, University of Massachusetts
Title:   "Cosmic Evolution of Dusty Starbursts"

Date:   Monday 07-Feb-2005
Speaker:   Dr. Karen O'Neil, National Radio Astronomy Observatory
Title:   "Massive Low Surface Brightness Galaxies: Recent Results and Discoveries"

Date:   Thursday 17-Feb-2005 *** Note special date ***
Speaker:   Dr. Andreas Eckart, University of Cologne
Title:  Variable Emission From SgrA*

I report on recent simultaneous near-IR/X-ray observations of the SgrA* counterpart associated with the massive 3 to 4 million solar mass black hole at the center of the Milky Way. Special emphasis is put on a flare that was detected in the X-ray with an excess 2-8 keV luminosity of about 6x10^33 erg/s. A fading flare of SgrA* with >2 times the interim-quiescent flux was also detected at the beginning of the NIR observations, which overlapped with the fading part of the X-ray flare. Compared to 8-9 hours before the near-IR/X-ray flare, a marginally significant increase in the millimeter flux density (measured with BIMA) of SgrA* was detected during measurements about 7-9 hours afterwards. It is found that the flaring state can be conveniently explained with a synchrotron self-Compton model involving up-scattered submillimeter photons from a compact source component, possibly with modest bulk relativistic motion.

Date:   Monday 21-Feb-2005
Speaker:   Dr. Paul Vanden Bout, National Radio Astronomy Observatory
Title:   "Early Universe Molecular Emission Line Galaxies"

Date:   Monday 07-Mar-2005
Speaker:   Dr. Nicole Homeier, Johns Hopkins University
Title:  Massive Stars in the W49A Giant Radio HII Region

W49A is our Galaxy's brightest radio HII region, and is embedded in the 10^6 solar mass W49 giant molecular cloud. I will present near-infrared imaging of the W49A region and K-band spectroscopy for a handful of the brightest stars. We detect photospheric features for three luminous stars; all three stars have Br gamma absorption, NIII emission, and HeII absorption. Only the hottest main sequence stars have HeII absorption; these are O3-4V stars. One of the stars is ionizing the 'CC' radio source (designation from DePree et al. 1997) with a radius of only 0.2pc. This is the best known case of an isolated massive star transitioning from the ultracompact HII region phase. I will present these findings and also discuss kinematic information derived from nebular emission lines, as well as implications for the accretion and coalesence models of massive star formation.

Date:   Monday 14-Mar-2005
Speaker:   Dr. Ed Sutton, University of Illinois
Title:   Bayesian Analysis in Radio Astronomy

Date:   Monday 04-Apr-2005
Speaker:   Dr. David Wilner, Harvard-Smithsonian Center for Astrophysics
Title:  Debris Disks around Nearby Stars

A significant fraction of nearby stars are known to be surrounded by disks of dust particles thought to be replenished by collisions of larger bodies analogous to the Kuiper Belt Objects of our Solar System. Much of our knowledge of these "debris disks" comes from imaging and photometry at far-infrared and submillimeter wavelengths, which are well matched to the spectrum of cold dust. The few systems that are spatially resolved show features that suggest dynamical sculpting by planets. I will discuss the resolved imaging of several nearby systems (Vega, epsilon Eridani, ...), the interpretation, and issues with current models. I will also discuss prospects in this area for new facilities, in particular the SMA on Mauna Kea, CARMA, and ALMA.

Date:   Monday 18-Apr-2005
Speaker:   Dr. Tommy Wiklind, Space Telescope Science Institute
Title:  Finding Distant Galaxies in the Infrared

High redshift galaxies are usually identified using various drop-out methods, where the redshift is determined by the location of the Lyman break. This technique has provided large samples of galaxies at redshifts up to z~4, recently extended to higher redshifts. Moving to even larger distances the Lyman break shifts into the near-infrared bands, where high quality photometric data are hard to find. In this talk I will present on-going work using an alternative method, the Balmer break technique, for selecting high redshift galaxies. We have used this technique to find a number of z~7 galaxies which appear to be relatively dust-free and surprisingly massive post-starburst galaxies. The Balmer break method also allows selection of dusty starburst systems at redshifts z>2. A large number of this type of objects have been found, and their relation to submillimeter detected galaxies will be discussed.

Date:   Monday 02-May-2005
Speaker:   Dr. Remy Indebetouw, University of Virginia
Title:   Massive Star Formation Across the Galaxy With Spitzer

Date:   Monday 23-May-2005
Speaker:   Dr. Catherine Buchanan, Rochester Institute of Technology
Title:  Radio-Excess IRAS Galaxies: Towards an understanding of radio emission in active galaxies

In recent years, our understanding of active galaxies has developed into an increasingly clear picture. However, the initiation of radio emission in active galaxies and the radio-loud/radio-quiet dichotomy remain relatively poorly understood. Radio-excess galaxies, that lie between the traditional classes of radio-loud and radio-quiet active galaxies, are useful objects to give insight into the radio-loud/radio-quiet dichotomy. In the context of quasar-starburst evolutionary scenarios, FIR-luminous radio-excess galaxies are also good candidates to study the initiation of radio activity in AGN. In this talk I will present the findings from our multi-wavelength study of a sample of radio-excess IRAS galaxies, and describe the implications of our results for the understanding of radio emission from active galaxies.

Date:   Monday 27-Jun-2005
Speaker:   Dr. Tony Wong, Australia Telescope National Facility
Title:  Radio continuum, CO, and infrared emission from nearby star-forming galaxies

The tight correlation between far-infrared and radio emission in galaxies requires a coupling between thermal and non-thermal emission processes that remains poorly undertood. To improve our understanding of this correlation as a function of size scale, we have been comparing radio with mid-infrared (MIR) and far-infrared (FIR) images of nearby galaxies using a wavelet cross-correlation method. Following up our earlier finding of a strong correlation between CO and radio continuum emission in a sample of nearby spiral galaxies, down to a scale of ~100 pc (Murgia et al. 2005), we also consider the relationship of both radio and infrared emission to CO. In the LMC the radio and FIR images are much better correlated with each other than with gas tracers such as CO or HI. On the other hand, in nearby spirals the radio and MIR are not as well correlated, and a somewhat better correlation is found between MIR and CO emission. A number of systematic effects contribute to these results and deserve further scrutiny; however, our results thus far do not appear to require a close relationship between radio emission and molecular clouds. If cosmic ray heating of molecular clouds is more important than generally believed, an enhancement of CI over CO in regions exposed to strong cosmic ray fluxes might be expected.

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