Day 19

Friday.  Computer arrived yesterday afternoon.  Got to finish up the paper.


1106.2816
Sizing up Lyman-alpha and Lyman break galaxies
Malhotra, Rhoads, Finkelstein, Hathi, Nilsson, McLinden, Pirzkal


* what are the differences between these two anyways?
* Lyman-alpha galaxies:  guess: galaxies showing Lyman-alpha emission line.  actual: young galaxies in the early universe which typically has prominent emission of Lyman alpha photons.  Galaxies with vigorous ongoing star formation expected to show strong Ly-a emission lines.  Hot stars emit copious amounts of UV radiation, which ionizes the neutral hydrogen.  2/3 or the ionized H end up with emission of a Ly-a photon.  Guess correct.
* Lyman break galaxies:  guess: galaxies detected by the Lyman break; typically high z (z~2-3).  actual: selected by performing deep imaging in three broad band fiters (UGR).  Starforming galaxies at redshifts z>2.5 will be very faint or absent in the U filter.  Used to collect large number of z>2.5 galaxies.  Guess mostly correct.


Populations of high-z galaxies grow more luminous as they grow in linear size.  This is because the brightness per unit area has a distinct upper limit due to self-regulating nature of SF.  Or: observed increase in characteristic Ly-break galaxies (L*) with time can be explained by their increase in size (~1/H(z)).  In contrast, Lyman-alpha selected galaxies have a characteristic, constant, small size between redshift z2.25 and 6.5.  Coupled with surface brightness, this can explain their non-evolving UV continuum luminosity function.  LyAG compact physical size related to LyA emission/detection?  Measure 170 LyAG with HST over 2.25<z<6.  Combine with similar number of LyAG with half-light radii from the literature, and derive surface brightnesses for the entire combined sample.


* growth in size translates to evolving L* for LBG's.
* LyAG are compact, and compactness seems to be a requirement for LyA emission.




1106.2805
The Most metal-poor damped Ly-a systems: insights into chemical evolution in the very metal-poor regime
Cooke, Pettini, Steidel, Rudie, Nissen


* damped Ly-a (DLA) systems: regions of high-density neutral H, which absorbs Ly-a photos.


Probe nature and nucleosynthesis of the earliest generations of stars using high-resolution spectra of the most metal-poor DLA systems.  22 systems, iron abundance < 1/100 solar, first observations.  Investigate trend of C/O in the very metal-poor regime; compare O/Fe rations in the most metal-poor DLAs and halo stars.  Find near-solar values of C/O in DLAs at lowest metallicities; distribution [?] in agreement with that seen in Galactic halo stars.  O/Fe ratio in VMP (very metal poor) DLAs is essentially constant and show very little dispersion, in agreement with galactic halo stars (if oxygen measured in the OI 6300 line).  Good agreement--universal origin of these metals [but what else can it be other than stars?].  Compare with Pop II and III star nucleosynthesis models to determine the origin of the metals in VMP DLAs.  Shows enrichment by generation of metal-free stars, but cannot rule out Pop II contribution yet.


1106.2565
The Yellow supergiant progenitor of the SNe Type II 2011dh in M51
Maund et al.


* found a progenitor for a SNe.


From archival HST images, within 23mas.  Was a F8 supergiant star.  Single star at the end of core C-burning with mass of ...?  [What is M_ZAMS?]  Rejects progenitor source being a cluster: progenitor not spatially extended, absence of excess Ha emission, poor fit to synthetic cluster SEDs.  Binary companion may be contributing to SED, but not significantly.  Similar to SN 2008ax Type IIb; suggests large amount of progenitor's H envelope was removed before explosion.


* what's the significance of cluster/binary companion for this SNe?


1106.2546
Mass and environment as drivers of galaxy evolution II: the quenching of satellite galaxies as the origin of environmental effects
Peng, Lilly, Renzini, Carollo


* galaxy evolution, quenching of satellite galaxies.


Central/satellite dichotomy in SDSS groups; prev. work show satellite gals responsible for all the environmental effects; centrals redness does not depend on environment but only on stellar masses; for satellites, it depends on both.  Satellite-becoming gals turn red at a fraction independent of stellar mass, but depend on local overdensity (range 0.2 to 0.8).  Red fraction of satellites correlated better with local overdensity than the richness (DM halo mass) of the group.  Universality of the mass-quenching process (L* same for blue and red).  Post quenching merging modifies mass function of central galaxies, but only by 25%.


1106.2656
Star formation in a stellar mass selected sample of galaxies to z3 from the GOODS NICMOS survey
Bauer, Consclice, Perez-Gonzalez, Grutzbauch, Bluck, Buitrago, Mortlock


* star formation 


UV and IR-derived SFR from HST/ACS and Spitzer, investigate SF properties of a complete sample of ~1300 galaxies down to logM* ~ 9.5 at z~1.5.


1106.2815
Purely kinetic coupled gravity
Gubitosi, Linder


* Giulia!


Kinetic terms coupled to gravity can achieve cosmic acceleration.  Imposes shift symmetry on the scalar field.  Most general purely kinetic action term: reduces to a simply form involving a coupling of hte Einstein tensor with the kinetic term, and can be interpreted as adding a new term to Galileon gravity in curved spacetime.  Find quasistable loitering phase mimicking late time acceleration by a cosmological constant.


* what in the world do they mean by "naturalness"?  


1106.2966
MOND cosmology from holographic principle
Zhang, Li


* holographic principle: property of quantum gravity and string theories: description of a volume of space can be thought of as encoded on a boundary to the region (preferably a light-like boundary like a gravitational horizon).  


MOND and holographic approach of gravity, dark energy emergyes naturally.  No dark matter necessary.


1101.5401
Asymptotically safe cosmology
Hindmarsh, Litim, Rahmede


* renomalization?


Study quantum modifications to cosmology in a FRW universe with and without scalar fields.  Take the renormalization group running of gravitational and matter couplings into account.
Find two types of cosmological fixed points, where the renomalization group scale either freezes in, or continues to evolve with scale factor.  Classify cosmological fixed points with and without gravity displaying an asymptotically safe renomalization group fixed point.  


* I don't get this.