Day 377

Wednesday.

1302.6240
On the robustness of z=0-1 galaxy size measurements through model and non-parametric fits
Mosleh, Williams, Franx

Present size-stellar mass relations of nearby z=0.01-0.02 SDSS galaxies for samples selected by color, morphology, Sersic index n, and specific SFR.  Use: single Sersic fits, two-component Sersic models, and non-parametric method for size measurements.  Simulations show non-parametric and two-component Sersic methods provide the most robust effective radius measurements, while those based on single Sersic profiles are often overestimates, especially for red/early-type galaxies.  With robust sizes, show that for all subsamples, the mass-size relations are shallow at low stellar masses, and steepen above 3-4e10 Msun.  The mass-size relations for galaxies classified as late-type, low-n and SF are consistent with each other (and somewhat steeper at high mass than previous results), while blue galaxies follow a somewhat steeper relation.  Test potential systematics at high z; artificially redshift sample to z=1 and re-fit the galaxies using single Sersic profiles.  Sizes of galaxies before and after redshifting are consistent (negligible systematics).  Since the poorer physical resolution at high z washes out bright galaxy substructures, single-Sersic fitting appears to provide more reliable and unbiased effective radius measurements at high-z than for nearby, well-resolved galaxies.

1302.6253
The cluster and field galaxy AGN fraction at z=1 to 1.5: evidence for a reversal of the local anticorrelation between environment and AGN fraction
Martini, ... Jannuzi, Dey, ... et al

Fraction of cluster [why cluster?] galaxies that host AGN is an important probe of AGN fueling processes, the cold ISM at the centers of galaxies, and how tightly BHs and galaxies co-evolve.  Present a new measurement of the AGN fraction in a sample of 13 clusters of galaxies (M>1e14Msun) at 1<z<1.5 selected from Spitzer/IRAC shallow cluster survey, as well as the field fraction in the immediate vicinity of these clusters, and combine data with measurements from the literature to quantify the relative evolution of cluster and field AGN from the present to z~3.  Estimate that the cluster AGN fraction at 1<z<1.5 is f_A=3.0pm2.0% for AGN with a rest-frame above L_X>1e44 erg/s threshold.  This fraction is measured relative to all cluster galaxies more luminous than +1 relative to the absolute magnitude of the break in the galaxy luminosity function at the cluster z in IRAC 3.6um.  The cluster AGN fraction is 30x greater than the 3 sigma upper limit on the value for AGN of similar luminosity at z~0.25, as well as more than an order of magnitude greater than the AGN fraction at z~0.75.  AGN with >1e43 erg/s exhibit similarly pronounced evolution with redshift.  In contrast with the local universe, where the luminous AGN fraction is higher than in clusters, the X-ray and MIR-selected AGN fractions in the field and clusters are consistent at 1<z<1.5.  This is evidence that the cluster AGN population has evolved more rapidly than the field population from z~1.5 to the present.  This environment-dependent AGN evolution mimics the more rapid evolution of SF galaxies in clusters relative to the field.

1302.6362
Clustering of galaxies around GRB sight-lines
Sudilovsky et al

GRB afterglow seem to have strong intervening MgII absorption line systems relative to quasar LoS.  If this excess is real, one should also expect an overdensity of field galaxies around GRB sight-lines, but this is not found.

1302.5167
Determining accurate measurements of the growth rate from the galaxy correlation function in simulations
Contreras, Blake, Poole, Marin

Measure growth rate from z-space distortion in 2-pt galaxy correlation function, using high-res N-body sims, with new, flexible, empirical approach.  Quantify systematic error in measuring the growth rate in a 1 (Gpc/h)^3 volume over a range of z, from the DM particle distribution and a range of halo-mass catalogues with a number density comparable to the latest large-volume galaxy surveys (WiggleZ and BOSS).  Halo biases from unity to more massive haloes hosting LRGs probed.  The measured growth rate is sensitive to the model adopted for the small-scale real-space correlation function, and in particular that the "standard" assumption of a power-law correlation function can result in a significant systematic error in the growth rate determination.  Introduce new, empirical fitting function that produces results with a lower (5-10%) amplitude of systematic error.  Also introduce a new technique which permits the galaxy pairwise velocity distribution, the quantity which drives the non-linear growth of structure, to be measured as a non-parametric stepwise function.  

1302.5178
The WiggleZ dark energy survey: measuring the cosmic growth rate with the two-point galaxy correlation function
Contreras, Blake, ... et al

Study the grwoth rate of cosmic structure to redshift z=0.9 using more than 162k galaxy specz from WIggleZ.  Divide data into 4 z slices with effective redshifts 0.2, 0.4, 0.6, 0.76 and in each of the samples measure and model the 2-pt galaxy correlation function in parallel and transverse directions to the line-of-sight.  After simultaneously fitting for the galaxy bias factor, recover values for the cosmic growth rate which are consistent with the assumed LCDM input cosmo model, with an accuracy of around 20% in each z slice.   Investigate the sensitivity of results to the details of the assumed model and the range of physical scales fitted, making close comparison with a set of N-body simulations for calibration.  Measurements are consistent with an independent PS analysis of a similar data set, demonstrating that the results are not driven by systematic errors.  Determine the pairwise velocity dispersion of the sample in a non-parametric matter, showing that it systematically increases with decreasing redshift, and investigate the Alcock-Paczynski effects of changing the assumed fiducial model on the results.  Techniques should prove useful for current and future galaxy surveys mapping the growth rate of structure using the 2-dimensional correlation function.

1302.5377
A preliminary reconstruction of the orbit of the Chelyabinsk meteoroid
Zuluaga, Ferrin

Feb 15, 2013 meteoroid impact in Chelyabinsk.  Results of a preliminary reconstruction of the orbit of the Chelyabinsk meteoroid.  Calculate trajectory in the atmosphere from video recordings, use it to reconstruct the orbit in space of the meteoroid previous to the violent encounter with Earth.  Use MC methods to account for uncertainties implicit in the determination of the trajectory of the body in the atmosphere.  Use this result to classify the meteoroid among the near Earth astroid families finding that the parent body belonged to the Apollo asteroids.  Most orbital elements (except semimajor axis and inclination) are well constrained.

1302.4741
The host galaxies of long-duration gamma-ray bursts
Levesque

LGRBs are signatures of extraordinarily high-energy events occuring in our universe: core-collapse deaths of rare young massive stars.  Host galaxies of LGRBs are an excellent means of probing the environments and populations that produce their unusual progenitors.  In addition, these same young stellar progenitors makes LGRBs and their host galaxies valuable potentially powerful tracers of SF and metallicity at high redshifts.  However, properly unitizing LGRBs as probes of the early universe requires a thorough understanding of their formation and the host environments that they sample.  This review looks back at some of the recent work on LGRB host galaxies, with cosmo applications, and considers many new questions.