Day 118

Thursday.  Gave the talk today, I think I now have a grasp on how to give talks.  


MPIfR/AIfA Promotionskolloquium
The dusty, molecular envelopes of Red Supergiant stars: VY Canis Majoris as the Archetypal Example
Lies Verheyen


Maser emission of dusty envelopes surrounding red giant stars studied in 88 red supergiants associated with Galactic open clusters.  Detect SiO maser emission at 86 GHz towards 13 sources with the IRAM 30m telescope.  The maser observations allow us to determine the stellar line-of-sight velocity with high accuracy [how?  just like regular spectroscopy with emission lines?].  A comparison of the maser peak flux with previous detections at 43 GHz show that the 86 GHz maser is stronger in 10 out of the 12 red supergiants detected in both transitions.  [What's the relationship between the 43 and 86, aside that one is twice the other's frequency?]  Analysis of the colors indicates detections occur in the reddest sources, supporting a radiative pumping mechanism for the SiO maser.  Model VY CMa asymmetric nebula with 2d radiative transfer code to model the dust continuum spectrum and optical and near-IR images.  Find: VY CMa is surrounded by a dusty disk with surface density proportional to r^-1 which is observed under inclination angle of 55 degrees.  Dust has 1e-3 M_sun mass, and consists of a mixture of (metallic) Fe, Al2O3 (alumina), (Mg,Fe)2SiO4 (olivine, peridot, pretty!) and (Ca,Na)2(Al,Mg,Fe^2+)[(Al,Si)SiO7] (melilite, a solid solution).  The central star is best represented by a black body of 2800K.  The mass of VY CMa is 15 solar masses.  With an interferometer, observe selection of molecular transition in VY CMa's nebula: HCN(1-0), HCO+(1-0), SiS(5-4), NaCl(7-6), NaCl(8-7), SO2(3{1,3}-2{0,2}), SO2(16{2,14}-15{3,13}) and SO2(10{1,9}-10{0,10}).  The interferometric images show that different molecules trace different parts of the envelope.  NaCl is present exclusively in the spherical outflow, while SO2 is found in the bipolar outflow.  Reproduce observed emission by constructing a model of the envelope plus outflow.  The bipolar outflow has an opening angle of 120 degrees, a constant H2 density and the expansion velocity increases linearly from 15 km/s to 45 km/s.


Astronomisches Kolloquium (Oct. 28, 11:00)
The multiphase extraplanar medium in spiral galaxies
George Heald


Evolution of galaxy connected to environment.  Extraplanar region in spiral galaxies is the interface between the star-forming disk and the environment.  The structure and kinematics of the baryonic material in this interface region are vital clues to the relative importance of various processes, such as cold gas accretion and galactic fountains, in determining the history of galaxies.  The strength and morphology of the magnetic fields in these regions may also be crucial to understanding the connection to the intergalactic medium.  Hydrogen acccretion in local galaxies (HALOGAS) survey: deep edge-on spiral gas accretion WSRT observations; reveals the presence of kinematically lagging extraplanar gas, and counterparts to the MW's high velocity clouds. WSRT-SINGS survey: high-quality polarimaetric data for a partially overlapping galaxy sample: leads to a common model of the magnetic field morphology in spiral galaxies.  


1110.5635
Moving mesh cosmology: properties of gas disks
Torrey, Vogelsberger, Sijacki, Springel, Hernquist


Compare structural properties of galaxies formed in SPH GADGET vs. the moving-mesh code AREPO.  Both use identical gravity solvers and same sub-resolution physics, but use very different methods to track the hydrodynamic evolution of gas.  Permits: isolation of effects of hydro solver on formation and evolution of galactic disks.  Fit simulated gas disks with exponential profiles.  Find: cold gas disks formed using AREPO have systematically larger disk scale lengths and higher specific angular momenta than their GADGET counterparts.  Reason for difference: rooted in the inaccuracies of the SPH solver, and calls for a reassessment of commonly adopted feedback prescriptions in cosmological simulations.


* would the feedback prescriptions by Hopkins, Quataert, and Murray help?


1110.5636
Continuum removal in Halpha extragalactic measurements
Spector, Finkelman, Brosch


Point out important source of error in measurements of extragalactic H alpha emission, and suggest ways to reduce it.  Common procedure: take narrow-band and wide-band flux; subtract continuum from the narrowband.  Errors introduced by color effects: can lead to underestimates as large as 40% and overestimates as large as 10%, depending on the underlying galaxy's stellar population and the continuum-subtraction procedure used.  Errors may lead to biases in results of surveys, and to the underestimation of the cosmic star formation rate at low redshifts (the low z points in the Madau plot).  Use single colour measurement to significantly reduce these errors.


* interesting if it affects the Madau plot.


1110.5638
From star-forming spirals to passive spheroids integral field spectroscopy of E+A galaxies
Swinbank, Balogh, Bower, Zabludoff, Lucey, McGee, Miller, Nichol


* E+A galaxy: strong Balmer line absorption and weak OII emission.  "E" == spectra showing characteristics of stellar populations from elliptical galaxies; "A" == Balmer lines typical of spectra associated with "A" type stars.  A.k.a. "K+A" galaxies.


3d spectroscopy of 11 E+A galaxies, which suggests a recent burst of star-formation being triggered, but was subsequently abruptly ended.  Probe spatial and spectral properties of both the young (~1Gyr) and old (few Gyr) stellar populations.  Use H-delta equivalent widths to estimate burst masses be >10% by mass, also consistent with the SFH inferred from the broad-band SEDs.  On average the A-stars cover ~33% of the galaxy image, extending over 2-15 kpc^2, indicating that the characteristic E+A signature is a property of the galaxy as a whole and not due to a heterogeneous mixture of populations.  In ~50% of sample, A-stars, nebular emission, and continuum emission are not co-located, suggesting that the newest stars are forming in a different place than those that formed ~1Gyr ago, and that recent star-formation has occurred in regions distinct from the oldest stellar populations.  10/11 galaxies have dynamics that class them as "fast rotators" with magnitudes and dynamics comparable to local ellipticals and SO's.  Also find correlation between the spatial extent of the A-stars and dynamics: fastest rotators tend to have the most compact A-star populations, providing new constraints on models that aim to explain the transformation of later type galaxies into early types.  Show that there are no obvious differences between the line extents and kinematics of E+A galaxies detected in the radio (AGN) compared to non-radio sources, suggesting that AGN feedback does not play a dramatic role in defining their properties, or that its effects are short.


* A-stars lasts for... how many years?  


1110.5645
Far-infrared properties of Lyman break galaxies from cosmological simulations
Cen


* Lyman break galaxies: typically at z=3~4, uses Lyman break at 912A moving into UV/optical, and using UV/blue drop-outs to efficiently identify high-z objects.


AMR hydro simulations with ultra-high resolution (114h-1pc[?]) and large sample size (>3300 galaxies of stellar mass > 1e9 Msun), show how the stellar light of Lyman break galaxies at z=2 is distributed between optical/UV/FIR bands.  With a single scalar parameter for dust obscuration: can simultaneously reproduce the observed UV luminosity function for the entire range (3-100 Msun/yr) and extant FIR luminosity function at the bright end (>20Msun/yr).  Quantify that galaxies more massive or having higher SFR tend to have larger amounts of dust obscuration mostly due to a trend in column density and in a minor part due to a mass (or SFR)-metallicity relation.  Predict FIR luminosity function in the range SFR=1-100Msun/yr is a power law with a slope about -1.7.  Further predict that there is a "galaxy desert" at SFR (FIR) < 0.02 [...?] in the SFR(UV)-SFR(FIR) plane.  Detailed deistributions of SFR(FIR) at fixed SFR(UV) are presented.  Upcoming observations by ALMA should test this model.  If confirmed, it validates the predictions of the standard CDM model and has important [?] implications on the intrinsic SFR function of galaxies at high redshift.


* Is this discussion limited to the luminosity function of Lyman break galaxies only?  Is it talking about evolution into the z~2 range?


1110.5648
The spatial clustering of ROSAT all-sky survey AGNs III. Expanded sample and comparison with Optical AGNs
Krumpe, Miyaji, Coil, Aceves


Compare RASS vs SDSS AGN clustering; 0.07<z<0.50 range.  Meaaasure clustering amplitude through cross-correlation functions with SDSS galaxies, and derive the bias by applying a HOD model directly to the CCFs.  Find no difference in clustering of X-ray and optically-selected broad-line AGNs, as well as for samples with radio-detected AGNs are excluded.  This contrasts low z optically-selected narrow-line AGNs, where radio-loud AGNs are found in more massive halos than optical AGNs without a radio-detection.  [What does this imply?] The typical dark matter halo masses of our broad-line AGNs are 12.4-13.4, consistent with the halo mass range of typical non-AGN galaxies at low redshifts.  Find no significant difference between clustering if X-ray selected narrow-line AGNs and broad-line AGNs.  Confirm weak dependence of the clustering strength on AGN X-ray luminosity at a ~2 sigma level.  Finally, summarize the current picture of AGN clustering to z~1.5 based on three dimensional clustering measurements.


* states the facts on correlation, but doesn't state the implications or significance of these results.