1107.5587
The outer disks of dwarf irregular galaxies
Hunter, Elmegreen, Oh, Anderson, Nrdgren, Massey, Wilsey, Riabokin
* I didn't know dwarf irregulars had outer disks.
Obtain V and Galex UV images of 4 dIrr and 1 blue compact dwarf galaxies; additionally, B images of 3 of them (all ultra-deep, 29.5 mag/arcsec^-2 in V). Convert V and FUV and Ha into star formation rate profiles that are sensitive to the past 10 Myrs. Compare stellar distributions, surface brightness profiles, gas kinematics. Two general observations: (1) exponential disks in these irregulars are very regular (in spite of some lumpiness for young stars and HI distribuions, some kinematics of unordered motions, etc). (2) remarkable continuity of star formation throughout disks over time. 4/5 galaxies have SFR in the outer disk measured from the FUV tracks determined from the V band (?), requiring SF at a steady rate over the galaxy's lifetime. But, H I surface density profiles decline with radius more shallowly than stellar light; gas is marginally gravitationaly stable against collapse into clouds. Outer stellar disks challenges our consepts of SF and disk growth.
* I guess dIrrs are more disk-like than disks?
1107.6031
The galactic dust-to-metals ratio and metallicity using gamma-ray bursts
Watson
ISM of the Galaxy understanding requires knowledge of metallicity and dust-to-metal ratio, but there are uncertainties in these parameters. Determine dust-to-metal ratio of the Galaxy using absorption of X-ray afterglows of several 100 GRBs to determine metal column density in combination with Galactic dust maps to determine LOS dust extinction through the Galaxy in the direction of the GRB. GRB afterglows have large soft X-ray absoprtions--GRB upper bound define the Galactic dust-to-metal relation. Use 2-d two-sample KS test. Result consistent with previous study using bright X-ray sources in the Galaxy (N_H = 2.2pm0.3 e21 cm^-2 A_V assuming sloar metallicity). Use same technique, but use dust map instead of HI maps--this allows to place a limit on the metallicity in the Galaxy. Metallicity consistent with 1989 study that is often used with X-ray studies. Maybe the metallicity of typical ISM sightline through the Galaxy is ~0.25 dex higher than current best esimate of solar metallicity. Dust-to-gas ratio seems to be correlated with the total gas column density. Probably due to metallicity gradient observed toward the Galactic centre. The dust-to-gas ratio is non-constant. The dust column density at N_H=2.2e21 cm^-2 A_V (units?), represents a better proxy for the soft X-ray absorption column density than H I maps.
1107.5729
On identifying the progenitors of SNIa
Livio, Pringle
Two new means of identifying the main class of progenitors of SNIa: single or double degenerate: (i) if there is an viewing-angle dependence or dependence on non-spherically symmetric explosions, then the correlation between polarization and e.g., velocity gradient can be used to determine the geometry of the asymetry, and hence the nature of the progenitor, and (ii) in the double-degenerate case, the range in the observed properties is likely to increase with the amount of carbon seen in the ejecta.
* hmm, doesn't sound too convincing.
1107.5740
Merger induced scatter and bias in the cluster mass-SZ effect scaling relation
Krause, Pierpaoli, Dolag, Borgani
* I've read this before.
examine sources of scatter in the cluster mass-SZ observable relation using simulation\
s; more concentrated halos have stronger SZ signals at fixed mass, projection effects \
from correlated structures. Merging clusters cause asymmetric scatter such that the i\
nferred mass of merging systems is biased low. Mergers are the dominant source of bia\
s towards low inferred masses--over 50% of outliers on the low side of the scaling rel\
ation uderwent a major merger withing the last Gyr. More mergers at high z; so merger\
s cause a redshift-dependent bias in scaling relations. SZ morphology of massive clus\
ters are well corrleated with the clusters' dynamical state--morphology can be used to\
constrain merger fractions and identify merger-induced outliers of the scaling relati\
on.
1107.5721
Local group progenitors: Lyman alpha bright?
Dayal, Libeskind
A novel approach of identifying progenitors of MW and M31-type galaxies that are visib\
le as LAEs at z~6: CLUES (constrained local universe simulations) snapshot that repro\
duces the MW and M31 galaxies that are in the correct environment; couple that with a \
LAE model. Explore IGM ionization states from neutral to fully ionized; including (ex\
cluding) effects of clustered sources, the first local group progenitor appears as a L\
AE for a neutral hydrogen fraction of 0.4 (0.1). Number increases to 4 (6) of the MW\
(M31) progenitors being visible as LAEs for a completely ionized IGM; the contributio\
n from clustered sources is crucial in making the progenitors visible as LAEs, for all\
ionization states considered. Constrain on the physical properties of such progenito\
rs.
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