Date: Wednesday 28-Jan-2015
Speaker: Dr. Basmah Riaz (Univ. Hertfordshire/UMD/MPE)
Title: "Class I outflow sources in a ~3Myr old cluster: Clues to alternative formation mechanisms for very low-mass stars"
Abstract:
The origins of very low-mass stars (VLMs; ~0.3-0.08 Msun) have been subject to much debate, in order to understand if their formation and evolutionary stages are similar to those observed in solar-type pre-main sequence stars. We are conducting a multi-wavelength study to characterize Class I VLMs in nearby y oung star-forming regions. Our first results on Class I VLMs in the ?? Orionis region indicate prominent accretion and outflow activity, with the activity rates within the range observed for Class I protostars, and comparatively higher than Class II VLMs at similar ages. Radiative transfer modeling of the observed spectral energy distributions for these Class I VLM systems indicates the overall physical structure to be a scaled-down version of a typical low-mass protostellar system. Given the membership of these objects in a relatively evolved cluster of ~3 Myr of age, we consider an alternate formation mechanism in the context of the `hybrid' model of disk fragmentation, followed by ejection of a gaseous VLM clump.
Date: Thursday 5-Mar-2015
Speaker: Dr. Gerrit Verschuur (Physics Department, Univ. of Memphis)
Title: The Strange Case of HVC MI
Abstract:
Since 1973 an HI feature known as high-velocity cloud HVC MI has been mapped with resolutions of 36, 10 and 1 arcmin. I will show that MI is part of a very extended, twisted HI filament. Depending on the viewing angle, this filament reveals a helical twist in certain segments and then becomes HVC MI where the underlying filament twists into the line-of-sight. Available data will be used to show that this model best accounts for the presence of HVC MI, which is not a ‘cloud’ but a manifestation of a geometric phenomenon. This leads to a startling discovery. In previously published work, I claimed that MI was associated with an enhancement in the cosmic microwave background as observed by WMAP but offset from the continuum peak by 0.°7. However, when using PLANCK and HI aperture synthesis data the association is seen to be perfect with no angular offset. Using a typical relationship between background electron density and HI density, the continuum emission observed by PLANCK can be accounted for by electron brehmstrahlung. This study highlights a sad state of affairs as regards our knowledge of interstellar HI and its relationship to high-frequency continuum radiation observed by PLANCK and WMAP; this is the only direction for which all the relevant data are available. This points to the need for more aperture synthesis studies of interstellar HI features.
Date: Monday 30-Mar-2015
Speaker: Dr. Gerrit Verschuur (Physics Department, Univ. of Memphis)
Title: The Strange Case of HVC MI
Abstract:
Since 1973 an HI feature known as high-velocity cloud HVC MI has been mapped with resolutions of 36, 10 and 1 arcmin. I will show that MI is part of a very extended, twisted HI filament. Depending on the viewing angle, this filament reveals a helical twist in certain segments and then becomes HVC MI where the underlying filament twists into the line-of-sight. Available data will be used to show that this model best accounts for the presence of HVC MI, which is not a ‘cloud’ but a manifestation of a geometric phenomenon. This leads to a startling discovery. In previously published work, I claimed that MI was associated with an enhancement in the cosmic microwave background as observed by WMAP but offset from the continuum peak by 0.°7. However, when using PLANCK and HI aperture synthesis data the association is seen to be perfect with no angular offset. Using a typical relationship between background electron density and HI density, the continuum emission observed by PLANCK can be accounted for by electron brehmstrahlung. This study highlights a sad state of affairs as regards our knowledge of interstellar HI and its relationship to high-frequency continuum radiation observed by PLANCK and WMAP; this is the only direction for which all the relevant data are available. This points to the need for more aperture synthesis studies of interstellar HI features.
Date: Thursday 9-Apr-2015
Speaker: Dr. Helmut Dannerbauer
Title: Witnessing the Formation of Massive, Distant Galaxies in the (Sub)Millimeter Regime
Abstract:
In order to understand galaxy formation it is crucial to obtain sensitive observations of the emission of dust and molecular gas both of which constrain the on-going star formation or AGN activity and the future potential of the galaxy to grow. Constraining the growth of ensemble of galaxies in the distant universe and not simply the most active ones, is one of the primary goals of current and planned (sub)mm facilities. I will discuss two major questions in galaxy formation and assembly: 1) are dusty galaxies vigorously forming stars embedded within large scale structures at z>1.5; and 2) do dusty starbursts exist at the highest redshift. To shed light on these obscure topics, I will present our on-going observations of dust and molecular gas with a number of different (sub)mm facilities such as Herschel, APEX, IRAM or ALMA of one important star forming galaxy population in the distant universe: submillimeter selected galaxies (SMGs).
Date: Monday 18-May-2015
Speaker: Dr. Shih-Ping Lai
Title: In Quest of the Youngest Protostars and Protoplanetary Disks
