Day 103

Tuesday.  Lots of things to work on; still no apartment.


1110.1629
Concerning the classical cepheid VIc Wesenheit functions' strong metallicity dependence
Majaess, Turner, Gieren


* Classical Cepheids/Pop I Cepheids/Delta Cephei/Type I Cepheids: young, x4-20 M_sun stars, supergiants; day-month variability.
* Type II Cepheids/Pop II Cepheids: metal-poor, old, low-mass (0.5 M_sun) stars, 1-50 day variability, less bright (by 1.5 mag)
* RR Lyrae: mechanism the same, but a different type of variable (short periods); old, low-mass, metal-poor Pop II stars, has shed mass already.
* Dynamics of the pulsation: Eddington valve, or kappa-mechanism (kappa = gas opacity).  Doubly-ionized helium is more opaque ethan singly ionized helium.  Opacity determines how much radiation is trapped; temperature determines opacity.


Evidence for Cepheid VIc period-Wesenheit function if insensitive to metallicity.  There was a problem with applied correction to distances established for the Magellanic Clouds via a Galactic VIc Wesenheit calibration.  Applying a null correction consolidates the estimates.  Results imply that variations in chemical composition among Cepheids are comparatively negligible source of uncertainty for W(VIc)-based extragalactic distances and determinations of H_0.


1110.1630
CARMA survey toward IR-bright nearby galaxies (STING) II: Molecular gas star formation law and depletion time across the blue sequence
Rahman, Bolatto, Xue, Wong, Leroy, Walter, Bigiel, Rosolowsky, Fisher, Vogel, Blitz, West, Ott


Relationship between molecular gas and current sSFR at sub-kpc and kpc scales in 14 nearby SF galaxies.  Approximately linear relation between molecular gas and SFR surface density, with molecular gas depletion time ~2.3\pm1.3 Gyr.  


1110.1631
Radio bursts from superconducting strings
Cai, Sabancilar, Vachaspati


Radio bursts from cusps on superconducting strings are linearly polarized.


1110.1632
Multi-epoch nearby cluster survey: type Ia SN rate measurement in z~0.1 clusters and the late-time delay time distribution
Sand, Graham, Bildfell, Zaritzky, Pritchet, Hoekstra, Just, Herbert-Fort, Sivanandam, Foley, Mahdavi


Multi-Epoch Nearby Cluster Survey (MENeaCS): desitned to measure the cluster SN Ia rate in a sample of 57 X-ray selected galaxy clusters, with redshifts of 0.05<z<0.15.   23 cluster SNIa found, 4 were intracluster events.  Cluster SNIa rate, and red-sequence SNIa rate measured.  Red-sequence is consistent with 'field' elliptical rates.  Derive delay time distribution, result consistent with predictions for the double detonation explosion mechanism [?].  Single degenerate scenario delay time distribution predicts an order of magnitude drop off in SNIa rate ~6-7 Gyr after stellar formation, and the observed cluster rates cannot rule this out.


1110.1633
The SF history of the MW's nuclear star cluster
Pfuhl, Fritz, Zilka, Maness, Eisenhouer, Genzel, Gillessen, Ott, Dodds-Eden, Sternberg


450 cool giant stars spectroscopy data within 1pc from Sgr A*.  Use CO bands to derive temperatures of the giants.  Deepest spectro observation of galactic center.  Construct HR diagram of the red gian population; fit observation with model populations to derive SF history of the nuclear cluster.  Find (1) average nuclear SFR dropped from an initial maximum ~10Gyrs ago to a minimum 1-2Gyrs ago, and increased again during the last few hundred Myrs, (2) roughly 80% of the stellar mass formed more than 5 Gyrs ago; (3) mass estimates within R~1pc from Sgr A* favor a dominant star formation mode with 'normal' Chabrier/Kroupa IMF for the majority of the past star formation in the Galactic Center.  The bulk stellar mass seems to have formed under conditions significantly different from the young stellar disks, perhaps because at the time of the formation of the nuclear cluster the massive black hole and its sphere of influence was much smaller than today [?].


1110.1635
Missing BH unveil the SNe explosion mechanism
Belczynski, Wiktorowicz, Fryeer, Holz, Kalogera


Masses of compact remnants (WD, NS, BH) should be smoothly distributed, just like the smooth stellar mass distribution (0.1-100 Msun); but is not borne out by observed data.  A striking mass gap emerges at the boundary between neutron stars and BHs.  Heaviest NS reach a maximum of 2 M_sun, while the lightest BH are at least 5 M_sun.  With masses from 20 BH's, gap has remained intact and become a challenge to understanding of compact object formation.  Offer first guesses into the physical processes that bifurcate the formation of remnants into lower mass NS and heavier BHs.  Combining the results of full stellar modeling with multidimensional hydrodynamic simulations of SNe explosions, we explain the existence of the gap, and also put stringent constraints on the inner workings of the SN explosion mechanism: core-collapse SNe are launched within 100-200ms of the initial stellar collapse [?], implying the explosions are driven by Rayleigh-Taylor instabilities rather than the delayed standing accretion shock instabilities, resolving a major debate in the SNe community.


* Cool.


1110.1637
Can minor merging account for the size growth of quiescent galaxies?  New results from the CANDELS survey
Newman, Ellis, Bundy, Treu


Extremely compact galaxies at z~2 and their subsequent growth in physical size: revisit using WFC3/IR data or 935 galaxies with 0.4<z<2.5 and stellar masses M*>1e10.7 M_sun.  At each redshift, the most compact sources are those with little or no star formation; find that the mean size of these systems grows by a factor of 3.5 over this redshift interval.  New data enable us to identify companions to these hosts whose stellar masses are ten times smaller, but with good-enough photoz to define association.  Estimate minor merger rate over 0.4<z<2, in 404 quiescent hosts.  Find that 13-18% of quiescent hosts have likely physical companions with stellar mass ratios of 0.1 or greater.  Mergers of these companions will typically increase the host mass by 6% per merger timescale.  Estimate minimum growth rate necessary to explain the declining abundance of compact galaxies; assess mergers of the faint companions with their hosts are sufficient to explain this minimal rate.  Find mergers with mass ratios > 0.1 may explain most of the size evolution observed at z>~1 if a relatively short merger timescale is assumed, but rapid growth seen at higher redshift likely requires additional physical processes.


1110.1644
Super-eccentric migrating Jupiters
Socrates, Katz, Dong, Tremaine


A class of Formation theories of hot Jupiters: excitation of extreme orbital eccentricity followed by tidal dissipation at periastron passage that eventually circularizes the planetary orbit to a period of < 10 days.  Requires a high population of e>0.9 Jupiters, which Kepler might be able to detect.


1110.1694
Shrinking the Quadratic estimator
Anderes, Paul


Study regression characterization for the quadratic estimator of WL, developed by Hu and Okamoto (2001, 2002) for CMB.  Technique requires use to propose a fiducial model for the spectral density of the unknown lensing potential, but the resulting estimator is developed to be robust to misspecification of this model [???].  


* I'm confused.


1110.1718
Full-sky lensing reconstruction of gradient and curl modes from CMB maps
Namikawa, Yamauchi, Taruya


Present method of lensing reconstruction on the full sky:extend the optimal quadratic estimator of Okamoto & Hu (2003) to the case including the curl mode of deflection angle.  Compare with flat-sky estimator proposed by Cooray+ (2005).  Prospects for future observations discussed.


1110.1722
A remarkably high fraction of strong Ly-alpha emitters amongst luminous redshift 6.0<z<6.5 Lyman break galaxies in the UKIDSS ultra-deep survey
Curtis-Lake... etal


Ly_alpha escape fraction of ~25%.  L>=2L* galaxies at 6.0<z<6.5 display strong Ly_alpha emission, a fraction which is x2 higher than previously reported for L<=L* galaxies at z~6.  Results suggest: as the epoch of reionization is approached, plausible that the Ly_alpha emitter fraction amongst luminous (L>=2L*) LBGs shows a similarly sharp increase to that observed in their lower-luminosity (L<=L*) counterparts.


1110.1765
Accurate galacitc 21-cm H I measurements with the NRAO Green Bank telescope
Boothroyd et al


All-sky model made for the response of GBT at 21 cm is ued to correct for "stray" 21-cm radiation reaching the receiver through the sidelobes rather than the main beam; reduces systematic errors in 21-cm measurements by order of magnitude; allow accurate 21-cm H I measurements at 9' angular resolution.


1110.1877
Correlations between nebular emission and the continuum spectral shape in SDSS galaxies
Gyory, Szalay, Budavari, Csabai, Charlot


Statistical study of correlations and dimensionality of emission lines carried out on a sample of over 40k SDSS galaxies.  Using PCA, find equivalent widths of 11 strongest lines can be well represented using three parameters.  Correlation of emission pattern with eigenspace representation of continuum spectrum.  Prove empirical prescription for expectation values and variances of emission-line strengths as a function of spectral shape.  This estimation of emission lines has a sufficient accuracy to make it suitable for photometric applications; already proved useful in SDSS photometric redshift estimation.


* new spectro-z/photoz trick/method.  correlating emission lines with continuum can be useful for low S/N spectro measurements, I think.


1110.1924
Importance of the initial conditions for star formation -- II. fragmentation induced starvation and accretion shielding
Girichidis, Federrath, Banerjee, Klessen


Impact of different initial conditions for the initial density profile and the initial turbulence on the formation processes of protostellar clusters.  Study dense molecular cloud core collapse with 3d AMR simulations.  Focus on distribution of the gas among protostellar objects in the turbulent dynamical cores.  Find all stellar clusters follow a very similar gas accretion behaviour, despite large variations in initial configurations and the resulting gas/cluster morphology.  Once secondary protostars begin to form, the central region of a cluster is efficiently shielded from further accretion; hence objects located close to the center are starved of material.  Fragmentation induced starvation occurs not only in rotationally supported discs and filaments, but also in more spherically symmetric clusters with complex chaotic motions.  


* any observational evidence, of low mass stars in the center, etc?


1110.1925
Rotation curves of luminous spiral galaxies
Yegorova, Babic, Salucci, Spekkens, Pizzella


Stellar light distribution and rotation curves of high-luminosity spiral galaxies in the local universe.  30 Halpha and H I rotation curves.  Stellar disk scale-length of these objects was measured to taken from literature.  Find: in the outermost parts of the stellar disks of these massive objects, the rotation curves agree with the universal rotation curve; however a few rotation curves of the sample show a divergence [duh].


1110.1933
Dependence of barred galaxy fraction on galaxy properties and environment
Lee, Park, Lee, Choi


33k galaxies from SDSS DR7:  strong bars are dominantly hosted by intermediate-mass systems; weak bars prefer bluer galaxies with lower mass and lower concentration.  Strong bars are likely to be destroyed during strong tidal interactions, and that the mechanism for this phenomenon is gravitational and not hydrodynamical.  Fraction of weak bars has no correlation with environmental parameters.  Do not find any direct evidence for environmental stimulation of bar formation [how do they define environmental stimulation anyway?].


1110.1936
X-ray diagnostics of giant molecular clouds in the galactic center region and post activity of Sgr A*
Okada, Aharonian, Watanabe, Tanaka, Khangulyan, Takahashi


First calculations of morphologies and spectra of the reflected X-ray emission for several realistic models of Sgr B2, the most massive molecular cloud in MW.  


1110.1951
A garnd design for galaxy clusters: connections and predictions
Cavaliere, Lapi, Fusco-Femiano


X-ray observations of Intra cluster plasma (ICP) of 12 galaxy clusters, and analyze with entropy-based "Supermodel", described by few parameters: central level and outer slope of entropy profile.  Uniformly derive not only robust snapshots of the ICP thermal state, but also the concentration parameter marking the age of the host DM halo.  Test these profiles for consistence with numerical simulations and observations.  FInd central and outer entropy to correlate: cluster split into two main classes defined on the basis of low or high entropy conditions prevailing throughout the ICP.  Find inverse correlations between the central/outer entropy and halo concentration.  Interpret these in terms of mapping the ICP progress on timescales around 5 Gyr toward higher concentrations, under the drive of DM halo development.  Progress proceeds from HE to LE, twoard states of deeper entropy erosion by radiative cooling in the inner regions and of decreasing outer entropy production as the accretion peters out.  Propose radial and time features to constitute a cluster Grand Design, and make predictions.  For HE clusters: sustained outer temperature profiles.  For LEs: outer entropy ramp to bend over; temperature decline to steepen at low z.  Goes together with increasing turbulent support, as probed by SZ.


1110.1985
Investigating clustering dark energy with 3d weak cosmic shear
Ayaita, Schaefer, Weber


Present adequate numerical methods facilitating 3d weak cosmic shear calculations.  Possible constraints heavily depend on the DE equation of state w.  


1110.1987
Cross identification between X-ray and optical clusters of galaxies in the SDSS DR7 field
Wang, Yang, Luo, Lau, Wang, Mo, van den Bosch, Wang


201 X-ray clusters over SDSS DR7 area.  Following optical properties correlated with the X-ray luminosity: Central galaxy luminosity, central galaxy mass, group couminosity, group stellar mass.  Findamental plane relation between x-ray luminosity, central galaxy stellar mass and characteristic satellite stellar mass, unbias, obtained.  Find halo masses estimated using the velocity dispersion of satellite galaxies are not very reliable, while estimation using ranking of characteristic group stellar mass or X-ray luminosity scaling relation are more reliable (0.2-0.25 dex scatter).  Compare properties of groups of similar mass and z that are underluminous, find that X-ray luminous groups have more faint satellite galaxies and the red fraction in their satellite galaxies enhanced.  


AIfA Lens Seminar (today 2pm)
Cosmic evolution of dark and luminous mass in early-type galaxies
Andrea Ruff


Joint gravitational lensing and stellar-dynamical analysis of 11 early-type galaxies: redshifts, stellar velocity dispersions, lens models from Paper I.    Measure total mass density slope inside the Einstein radius for each of the 11 lenses (gamma'=2.16 average, with intrinsic scatter of 0.25).  Determine DM fraction for each lens within half the effective radius, find the average projected DM mass fraction to be 0.42 with scatter of 0.20 for a Salpeter IMF.  Investigate cosmic evolution of gamma' and find a mild trend d(gamma')/d(zd) = -0.25.  Suggests that the total density profile of massive galaxies has become slightly steeper over cosmic time.  If confirmed by larger samples, indicates dissipative processes played some role in the growth of massive galaxies since z~1.


* interesting.  evidence for baryonic contraction?  any DM fraction evolution?


** the actual talk: for those whose source z was not determined (which was all but 5 out of 20), prior estimates were used, and a corresponding error bar (which is x2-3 worse than when the z_src is known) was applied.


AIfA Lens Seminar (tomorrow 11am)
Weighing the Giants: unbiased weak lensing masses for X-ray luminous galaxy clusters
Douglas Applegate


Galaxy cluster cosmology: WL calibration of mass-observable relations is essential for the most efficient use of these survey data, but only if lensing masses are unbiased to better than 5% accuracy.  Traditional lensing techniques are not yet at this level; demonstrate how shear tomography with photometric redshifts may be used to meet this exacting standard.  Present lensing follow up of 50 X-ray luminous galaxy clusters at 0.2<z<0.7, which holds potential for diverse science results and can serve as a pathfinder for future follow-up efforts.


* Gotta pay attention to this talk.