1307.3244
Detection of the compressed primary stellar wind in eta Carinae
Teodoro et al
Series of 3 HST STIS spectroscopic mappings, spaced one year apart, reveal 3 partial arcs in [Fe II] and [Ni II] emissions moving outward from eta Carinae. Identify arcs with the shell-like structures, seen in 3d hydro-sims, formed by compression of the primary wind by the secondary wind during periastron passages. [what is orbiting what?]
1307.3247
Evidence for a correlation between the sizes of quiescent galaxies and local environment to z~2
Lani ... Grogin, Lai, et al
Strong relationship between galaxy size and environment for the quiescent population in 1<z<2. Environments: projected galaxy overdensities on scales of 400 kpc, determined from 96k K-band selected galaxies from UKIDSS UDS. Sizes determined from ground-based K-band imaging, calibrated using spaced-based CANDELS HST observations in the centre of the UDS field, with photometric redshifts and stellar masses derived from 11-band photometric fitting. From the resulting size-mass relation, confirm that quiescent galaxies at a given stellar mass were typically ~ 50% smaller at z~1.4 compared to the present day. At a given epoch, however, find that passive galaxies in denser environments are on average significantly larger at a given stellar mass. The most massive quiescent galaxies (M* > 2e11 Msun) at z>1are typically 50% larger in the highest density environments compared to those in the lowest density environments. Using MC simulations, reject the null hypothesis that the size-mass relation is independent of environment at >4.8 sigma for 1<z<2. In contrast, the evidence for a relationship between size and environment is much weaker for SF galaxies.
1307.3254
Time delay and accretion disk size measurements in the lensed quasar SBS 0909+532 from multiwavelength microlensing analysis
Hainline, ... Kochaneck, et al
2.5 seasons of SDSS r-band photometry of lens quasar from USNO, as well as 2 seasons each of g- and r-band monitoring from Liverpool Robotic Telescope. Using MC sims to simultaneously measure the system's time delay and model the r-band microlensing variability, confirm and significantly refine the precision of the system's time delay to Delta t_AB = 50+2-4 days, where the stated uncertainties represent the bounds of the formal 1 sigma CL. There may be a conflict between the time delay measurement and a lens consisting of a single galaxy. While models based on the HST astrometry and a relatively compact stellar distribution can reproduce the observed delay, the models have somewhat less DM than expected. Also carry out a joint analysis of the microlensing variability in the r- and g-bands to constrain the size of the quasar's continuum source at these wavelengths, obtaining log[(r_{s,r}/sm) (cos(i)/0.5)^1/2] = 15.3 pm 0.3 and [...r_{s,g}...] = 14.8 pm 0.9, respectively. Current results do not formally constrain the temperature profile of the accretion
disk, but a re consistent with the expectations of standard thin disk theory.
1307.3322
A scaling relation between merger rate of galaxies and their close pair count
Jiang, Jing, Han
When galaxy merger rate is measured from the observed close pair count, usually a single merger timescale is assumed. Current calibrations based on simulations have focused mostly on major mergers (stellar mass ratios from 1:1 to 1:4). Using a high-res N-body/SPH cosmo sim, find an accurate scaling relation between galaxy pair counts and merger rates down to a stellar mass ratio of about 1:30. The relation explicitly accounts for the dependence on redshift (or time), pair separation, and virial masses of the two galaxies in a pair. With this relation, the mean merger timescale for a close pair of galaxies can be obtained. The use of virial masses, instead of the stellar mass, is motivated by the fact that the dynamical friction time scale is mainly determined by the DM surrounding central and satellite galaxies. This fact can also minimize the error induced by uncertainties in modeling SF in the simulations. Since the virial mass can be read from the well-established relation between the virial masses and the stellar masses in observation, scaling relation ca be easily applied to observations to obtain the merger rate and merger time scale. For major merger pairs (1:1-1:4) of galaxies above 4e10 Msun/h at z=0.1, it takes about 0.31Gyr to merge for pairs within a projected distance of 20 kpc/h with stellar mass ratio of 1:1, while the time taken goes up to 1.6 Gyr for mergers with stellar mass ration of 1:4. Results indicate that a single timescale is not enough to describe mergers with the stellar mass ratio spanning even a narrow range from 1:1 to 1:4.
1307.3403
Detection of Ly$\beta$ auto-correlations and Ly$\alpha$-Ly$\beat$ cross-correlations in BOSS data release 9
Irsic, Slosar, Bailey, Eisenstein, ... McDonald, ... Rossi, Schneider, Sheldon, et al
Lya and Lyb cross spectra detected with high significance, with cross-correlation coefficient of ~1 at large scales. Lyb measurements contaminated by the associated OVI absorption, similar to Si contamination of the Lya forest. Lyb forest will allow extension of the usable path-length for the Lya measurements while allowing a better understanding of the physics of IGM and thus more robust cosmological constraints.
Detection of the compressed primary stellar wind in eta Carinae
Teodoro et al
Series of 3 HST STIS spectroscopic mappings, spaced one year apart, reveal 3 partial arcs in [Fe II] and [Ni II] emissions moving outward from eta Carinae. Identify arcs with the shell-like structures, seen in 3d hydro-sims, formed by compression of the primary wind by the secondary wind during periastron passages. [what is orbiting what?]
1307.3247
Evidence for a correlation between the sizes of quiescent galaxies and local environment to z~2
Lani ... Grogin, Lai, et al
Strong relationship between galaxy size and environment for the quiescent population in 1<z<2. Environments: projected galaxy overdensities on scales of 400 kpc, determined from 96k K-band selected galaxies from UKIDSS UDS. Sizes determined from ground-based K-band imaging, calibrated using spaced-based CANDELS HST observations in the centre of the UDS field, with photometric redshifts and stellar masses derived from 11-band photometric fitting. From the resulting size-mass relation, confirm that quiescent galaxies at a given stellar mass were typically ~ 50% smaller at z~1.4 compared to the present day. At a given epoch, however, find that passive galaxies in denser environments are on average significantly larger at a given stellar mass. The most massive quiescent galaxies (M* > 2e11 Msun) at z>1are typically 50% larger in the highest density environments compared to those in the lowest density environments. Using MC simulations, reject the null hypothesis that the size-mass relation is independent of environment at >4.8 sigma for 1<z<2. In contrast, the evidence for a relationship between size and environment is much weaker for SF galaxies.
1307.3254
Time delay and accretion disk size measurements in the lensed quasar SBS 0909+532 from multiwavelength microlensing analysis
Hainline, ... Kochaneck, et al
2.5 seasons of SDSS r-band photometry of lens quasar from USNO, as well as 2 seasons each of g- and r-band monitoring from Liverpool Robotic Telescope. Using MC sims to simultaneously measure the system's time delay and model the r-band microlensing variability, confirm and significantly refine the precision of the system's time delay to Delta t_AB = 50+2-4 days, where the stated uncertainties represent the bounds of the formal 1 sigma CL. There may be a conflict between the time delay measurement and a lens consisting of a single galaxy. While models based on the HST astrometry and a relatively compact stellar distribution can reproduce the observed delay, the models have somewhat less DM than expected. Also carry out a joint analysis of the microlensing variability in the r- and g-bands to constrain the size of the quasar's continuum source at these wavelengths, obtaining log[(r_{s,r}/sm) (cos(i)/0.5)^1/2] = 15.3 pm 0.3 and [...r_{s,g}...] = 14.8 pm 0.9, respectively. Current results do not formally constrain the temperature profile of the accretion
disk, but a re consistent with the expectations of standard thin disk theory.
1307.3322
A scaling relation between merger rate of galaxies and their close pair count
Jiang, Jing, Han
When galaxy merger rate is measured from the observed close pair count, usually a single merger timescale is assumed. Current calibrations based on simulations have focused mostly on major mergers (stellar mass ratios from 1:1 to 1:4). Using a high-res N-body/SPH cosmo sim, find an accurate scaling relation between galaxy pair counts and merger rates down to a stellar mass ratio of about 1:30. The relation explicitly accounts for the dependence on redshift (or time), pair separation, and virial masses of the two galaxies in a pair. With this relation, the mean merger timescale for a close pair of galaxies can be obtained. The use of virial masses, instead of the stellar mass, is motivated by the fact that the dynamical friction time scale is mainly determined by the DM surrounding central and satellite galaxies. This fact can also minimize the error induced by uncertainties in modeling SF in the simulations. Since the virial mass can be read from the well-established relation between the virial masses and the stellar masses in observation, scaling relation ca be easily applied to observations to obtain the merger rate and merger time scale. For major merger pairs (1:1-1:4) of galaxies above 4e10 Msun/h at z=0.1, it takes about 0.31Gyr to merge for pairs within a projected distance of 20 kpc/h with stellar mass ratio of 1:1, while the time taken goes up to 1.6 Gyr for mergers with stellar mass ration of 1:4. Results indicate that a single timescale is not enough to describe mergers with the stellar mass ratio spanning even a narrow range from 1:1 to 1:4.
1307.3403
Detection of Ly$\beta$ auto-correlations and Ly$\alpha$-Ly$\beat$ cross-correlations in BOSS data release 9
Irsic, Slosar, Bailey, Eisenstein, ... McDonald, ... Rossi, Schneider, Sheldon, et al
Lya and Lyb cross spectra detected with high significance, with cross-correlation coefficient of ~1 at large scales. Lyb measurements contaminated by the associated OVI absorption, similar to Si contamination of the Lya forest. Lyb forest will allow extension of the usable path-length for the Lya measurements while allowing a better understanding of the physics of IGM and thus more robust cosmological constraints.
No comments:
Post a Comment