Day 600

Saturday.  Sunday.  Monday.  Tuesday.

1402.0592
The Earth as an extrasolar transiting planet - II: HARPS and UVES detection of water vapor and biogenic species O$_2$ and O$_3$
Arnold et al

The atmospheric composition of transiting exoplanets can be characterized during transit by spectroscopy.  For an Earth twin, models predict that O2 and O3 biogenic gases should be detectable, as well as water vapor.  The aim is to measure the Earth radius versus wavelength at the highest spectral resolution available to fully characterize the signature of the Earth seen as a transiting exoplanet.  Present observations of Dec. 21, 2010 Moon eclipse.  The Earth observed from the Moon during a lunar eclipse transits in from of the Sun and opens access to the Earth atmosphere transmission spectrum [so how are we obtaining Earth spectra from the Moon?---reflection from the moon surface, apparently].  Use 2 different ESO spectrographs to take penumbra and umbra high-resolution spectra from 3100 to 10400AA.  A change in moisture above the telescope compromised the UVES data; this effect is corrected.  3 different methods used for analysis.  All clearly show the spectral signatures of the Rayleigh scattering in the Earth atmosphere and the bands of H2O, O2 and O3.  Sodium is detected.  Show that the E-ELT will be able to detect the O2 A-band, and O3 and water vapor to a lesser sextant, for an Earth twin at 10 pc.

1402.7073
Cold dark matter haloes in the Planck era: evolution of structural parameters for Einasto and NFW profiles
Dutton, Macció

Present the evolution of the structure of relaxed CDM haloes in Planck cosmology.  Simulations cover 5 decades in halo mass (dwarf galaxies to galaxy clusters).  Due to the increased matter density and PS normalization the concentration mass relation in the Planck cosmology has a 20 % higher normalization at z=0 compared to WMAP cosmology.  Confirm that CDM haloes are better described by the Einasto profile; CDM haloes at galaxy half-light radius have significantly steeper density profiles than implied by NFW fits.  There is a scatter of 0.2 dex in the Einasto shape parameter at fixed halo mass, adding further to the diversity of CDM halo profiles.  The evolution of the concentration mass relation in the simulations is not reproduced by any of the analytic models in the literature.  Provide a simple fitting formula that accurately describes the evolution between redshifts z=5 to 0 for both NFW and Einasto fits.  The observed concentrations and halo masses at low redshifts of spiral galaxies, groups and clusters of galaxies are in good agreement with simulations, suggesting only mild halo response on these scales.


1402.7076
The mass-independence of specific star formation rates in galactic disks
Abramson et al

The slope of the SFR-M* relation (the SFR "Main Sequence) is not quite unity; sSFR (==SFR/M*) are weakly-but-significantly anti-correlated with M*.  Demonstrate that this trend may simply reflect the well-known increase in bulge mass-fractions -- portions of a galaxy not forming stars -- with M*.  Using a large set of bulge/disk decompositions and SFR estimates derived from the SDSS, show that re-normalizing SFR by disk stellar mass (sSFRd = SFR/Mdisk) reduces the M* dependence of SF efficiency by ~0.2.5 dex per dex, erasing it entirely in some subsamples.  Quantitatively, find log(sSFRd)-log(M*) to have a slope -0.20<beta_disk<0.00pm0.02 (depending on SFR estimator and MS definition) for SF galaxies with M*>1e10 Msun and bulge mass fractions B/T<0.7, generally consistent with a pure-disk control sample (beta_contral=-0.05pm0.04).  That <SFR/Mdisk> is (largely) independent of host mass for SF disks bears strongly on scenarios of galaxy evolution derived from any SFR-M* relation, including: the principal manifestation of "mass quenching" (bulge growth); the constancy of the shape of the star-forming stellar mass function (uniform dlog(M*)/dt, as assuming disk-driven growth); and the degree to which dispersion in SFR(M*,t) encodes diversity in SFHs.  Results emphasize the need to treat galaxies as composite systems -- not integrated masses -- in observational and theoretical work.

1403.0002
Lyman edges in supermassive black hole binaries
Generozov, Haiman

Propose a new spectral signature for SMBH binaries with circumbinary gas disks: a start drop in flux blueward of the Lyman limit.  A prominent edge is produced if the gas dominating the emission in the Lyman continuum region of the spectrum is sufficiently cold (T<20,000K) to contain signifiant neutral hydrogen.  Circumbinary disks may be in this regime if the binary torques open a central cavity in the disk and clear most of the hot gas from the inner region, and if any residual UV emission from the individual BHs is either dim or intermittent.  Model the vertical structure and spectra of circumbinary disks using the radiative transfer code TLUSTY, and identify the range of BH masses and binary separations producing a Lyman edge.  Find that compact SM binaries with orbital periods of ~0.1-10 yr, whose GWs are expected to be detectable by pulsar timing arrays, could have prominent Lyman edges.  Such strong spectral edge features are not typically present in AGN spectra and could serve as corroborating evidence for the presence of a SMBH binary.

1403.0003
Satellites of radio AGN in SDSS: insights into AGN triggering and feedback
Pace, Salim

Effects of radio jets on galaxies in their vicinity (satellites) and the role of satellite in triggering radio-loud AGNs.  Compare the aggregate properties of satellites of a sample of 7,220 radio AGNs at z<0.3 to the satellites of a control sample of radio-quiet galaxies, which are matched in redshift, color, luminosity, and axis ratio, as well as by environment type: field galaxies, cluster members and brightest cluster galaxies (BCGs).  Remarkably, find that radio AGNs exhibit on average a 50% excess (17 sigma) in the number of satellites within 100 kpc even though the cluster membership was controlled for (e.g., radial BCGs have more satellites than radio-quiet BCGs, etc.).  Satellite excess is not confirmed for high-excitation sources, which are only 2% of radial AGN.  Extra satellites may be responsible for raising the probability for hot gas AGN accretion via tidal effects or may otherwise enhance they intensity or duration of the radio-emitting phase.  Furthermore, find that the incidence of radio AGNs among potential hosts (massive ellipticals) is similar for field galaxies and for non-BCG cluster members, suggesting that AGN fueling depends primarily on conditions in the host halo rather than the parent, cluster halo.  Regarding feedback, find that radio AGNs, either high or low excitation, have no detectable effect on star formation in their satellites, as neither induced SF nor SF benching is present in more than ~1% of radio AGN.

1403.0007
Cosmic star formation history
Madau, Dickinson

[review article]  Review the range of complementary techniques and theoretical tools that are allowing astronomers to map the cosmic history of SF, heavy element production, and reionization of the universe from the cosmic "dark ages" to the present epoch.  A consistent picture is emerging from modes galaxy surreys, whereby the SFR density peaked about 3.5 Gyr after the Big Bang, at redshift 1.9, and declined exponentially at later times, with an e-folding type scale of 3.9 Gyr.  Half of the stellar mass observed today was formed before redshift 1.3.  Less than 1% of today's stars formed during the epoch of reionization, at redshift greater than 6.  Under the simple assumption of a universal IMF, the global stellar mass density inferred at any epoch matches reasonably well the time integral of all the preceding SF activity, although a mild disagreement may still point to unresolved issues with the measurements, or to deviations in the stellar IMF from conventional assumptions.  The assembly histories of the stellar component of galaxies and their central BHs were quite similar, offering evidence for the co-evolution of BHs and their host galaxies.  The rise of the mean metallicity of the universe to about 0.001 solar by redshift 6, one Gyr after the BB, appears to have been accompanied by the production of fewer than 10 H Ly-continuum photons per baryon, a rather tight budget for cosmological deionization.

1403.0044
Exhausting the information: novel bayesian combination of photometric redshift PDFs
Kind, Brunner

The estimation and utilization of photo-z PDFs has become increasingly important, primarily because of the prominent role photo-z PDFs play in enabling photometric survey data to be used to make cosmological constraints, especially when compared to single estimates.  Currently there exist a wide variety of algorithms to compute photo-z's, each with their own strengths and weaknesses.  In this paper, present a novel and efficient Bayesian framework that combines the results from different photo-z techniques into a more powerful and robust PDF estimate by maximizing they information from the photometric data.  To demonstrate this, use a supervised machine learning technique based on prediction trees and a random forest, an unsupervised method based on self organizing maps and a random atlas, and a standard template fitting method (easily extend to other existing techniques).  Use data from the DEEP2 survey and more than 1e6 galaxies from the SDSS to explore different methods for combining the photo-z predictions from these techniques.  Demonstrate that they can improve the accuracy of the final photo-z estimate over the best input technique, that the fraction of outliers is reduced, and that the identification of outliers is significantly improved when a Naive Bayes Classifer to this combined information is applied.  Furthermore, introduce a new approach to explore how different techniques perform across the different areas within the information space supported by the photometric data.  More robust and accurate photo-z PDFs will allow even more precise cosmological constraints to be made by using photometric surveys.  These improvements as we approach the limit of available training data (e.g., LSST).

1403.0055
A physical model for the evolving UV luminosity function of high redshift galaxies and their contribution to the cosmic reionization
Cai et al

Present a physical model for the evolution of UV LF of high-z galaxies, taking into account in a self-consistent way their chemical evolution and the associated evolution of dust extinction. The model yields good fits of the UV and Lya LFs at z>~2.  The weak evolution of both LFs between z=2 and 6 is explained as the combined effect of the negative evolution of the halo MF, of the increase with redshift of the SF efficiency, and of dust extinction.  The slope of the faint end of the UV LF is found to steepen with increasing redshift, implying that low luminosity galaxies increasingly dominate the contribution to the UV BG at higher and higher redshifts.  The observed range of UV lumionsities at high-z implies a minimum halo mass capable of hosting active SF [is] M_crit <~ 1e9.8 M_sun, consistent with the constraints from hydrodynamical simulations.  From fits of Lya LFs plus data on the luminosity dependence of extinction and from the measured ratios of non-ionizing UV to Lyman-continuum flux density for samples of z=~3 Ly break galaxies and Lya emitter, derive a simple relationship between the escape fraction of ionizing photons and the sSFR, implying larger escape fraction for less massive galaxies.  Galaxies already represented in the UV LF (M_UV<~-18) can keep the universe fully ionized up to z=~6, consistent with (uncertain) data pointing to a rapid drop of the ionization degree above z~6.  On the other side, the electron scattering optical depth, tau_es, inferred from CMB experiments favor an ionization degree close to unity up to z=~9-10.  Consistency with CMB data can be achieved if M_crit =~ 1e8.5 Msun, implying that the UV LFs extend to M_UV=~-13, although the corresponding tau_es is still on the low side of CMB-based estimates.

1403.0293
First measurement of $\sigma_8$ using supernova data only
Catsro, Quartin

Conversion of WL effects in the SN Hubble diagram from noise into signal; such signal is sensitive to the grout of structure in the universe.   … Sigma_8=0.84+0.28-0.65.  Results consistent with mock simulations, and with independent measurements.

1403.0357
Generation of an optimal target list for the Expolpanet Characterisation Observatory (EChO)
Varley et al

An ESA space mission concept.  Through direct measurement of the atmospheric chemical composition of hundreds of exoplanets, EChO would address fundamental questions such as: what are exoplanets made of ?  How do planets for hand evolve?  What is the origin of exoplanet diversity?  A dedicated survey mission for transit and eclipse spectroscopy capable of observing a large, diverse and ill-defined planetary sample within its 4 to 6 year mission lifetime.  Simulations show EChO would be capable of observing a large and diverse sample of planets even if it were launched today, and the wealth of optical targets for EChO expected to be discovered in the next 5 years by space and ground-based facilities is simply overwhelming.  Build on previous molecular detectability studies to show what molecules and abundances will be detectable by EChO for a selection of real targets with various molecular compositions and abundances. EChO's unique contribution to exoplanetary science will be in identifying the main constituents of hundreds of exoplanets in various mass/temperature regimes.  Full results at: www.ucl.ac.uk/exoplanets/echotargetlist.

1403.0502
On the (in)variance of the dust-to-metals ratio in galaxies
Mattsson et al

Recent works demonstrate a surprisingly small variation of the dust-to-metals ratio in different environments and a correlation between dust extinction and the density of stars.  This may appear as a strong evidence of cosmic dust being produced mainly by stars.  But evidence for significant variation of the dust-to-metals ratio with metallicity.  Demonstrate here that a simple star-dust scenario is problematic also in the sense that is requires that destruction of dust in the interstellar medium (e.g., due to passage of SN shocks) must be highly inefficient.  Suggest a model where stellar dust production is indeed efficient, but where interstellar dust growth is equally important and acts as a replenishment mechanism which can counteract the effects of dust destruction.  This model appears to resolve the seemingly contradictive observations, given that the ratio of the effective (stellar) dust and metal yields is not universal and this may change from one environment to another, depending on metallicity.