Day 827

Wednesday.

15002.00003
A direct onstraint on the gas content of a massive, passively evolving elliptical galaxy at z=1.43
Sargent et al

In comparison to gas and dust in SF galaxies at the peak epoch of galaxy assembly, little is known about the ISM of distant, passively evolving galaxies.  Report on a deep 3mm band search with IRAM/PdBI for molecular gas in a massive (M*~6e11 Msun) elliptical galaxy at z=1.4277, the first observation of this kind ever attempted.  Place a 3 sigma upper limit of 0.30Jy km/s on the flux of the CO(J=2-1) line of L'_CO<8.3e9 K km/s pc^2, assuming a line width in accordance with the stellar velocity dispersion of sigma*~330 km/s.  This translates to a molecular gas mass of <3.6e10 (alpha_CO/4.4)M_sun or a gas fraction of <5% assuming a Saltpeter IMF and an ISM dominated by molecular gas, as observed in local ETGs.  This low gas fraction approaches that of local ETGs, suggesting that the low SF activity in massive, high-z passive galaxies reflects a true dearth of gas and a secondary role for inhibitive mechanisms like morphological quenching.

1502.00008
Gravitational lens modelling in a citizen science context
Küng, Saha, et al

Develop a method to enable collaborative modeling of gravitational lenses and lens candidates, that could be used by non-professional lens enthusiasts.  Uses and existing free-form modeling program (glass), but enables the input to this code to be provided in a novel way, via a user-generated diagram that is essentially a sketch of an arrival-time surface.  Report on an implementation of this method, SpaghettiLens, which has been tested in a modeling challenge using 29 simulated lenses drawn from a larger set created for the Space Warps citizen science SL search.  Find that volunteers from this online community asserted the image parities and time ordering consistently in some lenses, but made errors in other lenses depending on the image morphology.  While errors in image parity and time ordering lead to large errors in the mass distribution, the enclosed mass was found to be more robust: the model-derived Einstein radii found by the volunteers were consistent with those produced by one of the professional team, suggesting that given the appropriate tools, gravitational lens modeling is a data analysis activity that can be crowd-sourced to good effect.  Ideas for improvement are discussed, these include (a) overcoming the tendency of the models to be shallower than the correct answer in test cases, leading to systematic overestimation of the Einstein radius by 10% at present, and (b) detailed modeling of arcs.

1502.00292
Giant disk galaxies : where environment trumps mass in galaxy evolution
Courtois, Zaritsky, Sorce, Pomarede

Identify some of the most HI massive and fastest rotating disk galaxies in the local universe with the aim of probing the processes that drive the formation of these extreme disk galaxies.  By combining data from the Cosmic Flows project, which has consistently reanalyzed archival galaxy HI profiles, and 3.6 um photometry obtained with the Spitzer Space Telescope, with which stellar mass can be measured, use the baryonic Tully-Fisher (BTF) relationship to explore whether these massive galaxies are distinct.  Discuss several results, but the most striking is the systematic offset of the HI-massive sample above the BTF.  These galaxies have both more gas and more stars in their disks than the typical disk galaxy of similar rotational velocity.  The "condensed" baryon fraction, f_C, the fraction of the baryons in a DM halo that settle either as cold gas or stars into the disk, is twice as high in the HI-massive sample than typical, and almost reaches the universal baryon fraction in some cases, suggesting that the most extreme of these galaxies have little in the way of a hot baryonic component or cold baryons distributed well outside the disk.  In contrast, the SFE, measured as the ratio lf the mass in stars to that in both stars and gas, shows no difference between the HI-massive sample and the typical disk galaxies.  Conclude that the SFE is driven by an internal, self-regulating process, while f_C is affected by external factors.  Also found that the most massive HI detected galaxies are located preferentially in filaments.  Present the first evidence of an environmental effect on galaxy evolution using a dynamical definition of a filament.

1502.00313
The mass-concenration relation and the stellar-to-halo mass ratio in the CFHT Stripe 82 survey
Shan, Kneib, Li, Comparat, Erben, ... Van Waerbeke, et al

A new measurement of M-c relation and the stellar-to-halo mass ratio over 5e12 to 2e14 Msun range galaxy clusters.  Used stacked lensing signals from CS82, combined with clusters from SDSS DR10.  Measure for 0.2<z<0.4 and 0.4<z<0.6.  Conclude that the amplitude A and slope B are both consistent with the simulation predictions by Klypin+2014 within errors.  Also measure the stellar-to-halo mass ratio and find it to be flatter than previous measurement for high stellar masses because of the complex structures and merger history in massive DM haloes.

1502.00394
Probing the DM radial profile in lens galaxies and the size of X-ray emitting region in quasars with mircolensing
Jiménez-Vicente, Mediavilla, Kochanik, Muñoz

Use X-ray and optical microlensing measurements of 47 image pairs in 18 lens systems to study the shape of the DM density profile in the lens galaxies and the size of the (soft) X-ray emission region.  Show that single epoch X-ray microlensing is sensitive to the source size.  These results, in good agreement with previous estimates, show that the X-ray size scales roughly linearly with the BH mass, with a HLR of R_1/2~(20pm12)r_g (r_g=GM_BH/c^2).  This corresponds to a size of ~1 light dat for a black hole mass of M_BH=1e9Msun.  Simultaneously estimate the fraction of the local surface mass density in stars, finding that the stellar mass fraction is alpha=0.20pm0.05 at an average radius of ~1.9 R_e, where R_e is the effective radius of the lens.  This stellar mass fraction is insensitive to the X-ray source size and in excellent agreement with earlier results based on optical data.  By combining the X-ray and optical microlensing data, divide this larger sample into two radial binds.  Find that the surface mass density in the form of stars is alpha=0.31pm0.15 and alpha=0.13pm0.05 at (1.3pm0.3) R_e and (2.3mp0.3) R_e, respectively, in good agreement with expectations and some previous results.

1502.00709
How to collect matches that will catch fire
Loeb

How can we select a cohort of promising astrophysicists before they have made their discoveries?  This is a fundamental challenge of academic planning.  Argue that science can only blossom if young researches are rewarded for acquired skills and growth rather than inherited academic ancestry.

1502.00806
Exoplanets: Gaia and the importance of ground based spectroscopy follow-up
Benamati et al

Thanks to Gaia, high-accuracy astrometric orbits of thousands of new low-mass celestial objects will be collected, such as extra-solar planets and brown dwarfs.  These measurements in combination with spectroscopy and with present day and future extrasolar planet search programs (HARPS, ESPRESSO) will have a crucial contribution to several aspects of planetary astrophysics (formation theories, dynamical evolution, etc).  Moreover, Gaia will have a strong contribution on the stellar chemical and kinematic characterization studies.  In this paper, preset a shirt overview of the importance of Gaia in the context of exoplanet research.  As preparatory work for Gaia, then present a study where derived stellar parameters for a sample of field giant stars are derived.  [???]