Sunday.
1401.7666
Near-infrared log-slit spectra of Seyfert galaxies: gas excitation across the central kilparsec
van der Laan, Schinnerer, Boeker, Armus
The excitation of the gas phase of the ISM can be driven by various mechanisms. In galaxies with an AGN (e.g., Seyferts), both radiative and mechanical energy from the central BH, or the stars in the disk surrounding it may play a role. Investigate the relative importance and range of influence of the AGN for the excitation of ionized and molecular gas in the central kilo parsec of its host galaxy. Present H- and K-band long-slit spectra for a sample of 21 nearby (D<70 Mpc) Seyfert galaxies obtained with the NIRSPEC instrument on the Keck telescope. For each galaxy, fit the nebular line emission, stellar continua, and warm molecular gas as a function of distance from the nucleus. Analysis does not reveal a clear difference between the nucleus proper and off-nuclear environment in terms of excitation mechanisms, suggesting that they influence of an AGN reaches far into the disk of the host galaxy. The radial variations in emission line ratios indicate that, while local mechanisms do affect the gas excitation, they are often averaged out when measuring over extended regions. The fully calibrated log-slit spectra, as well as the fitting results are available on-line.
1401.7676
Evolution in the escape fraction of ionizing photons and the decline in strong Lya emission from z>6 galaxies
Dijkstra, Wyithe, Haiman, Mesinger, Pentericci
The rapid decline in the number of strong Lya emitting galaxies at z>6 provides evidence for neutral hydrogen in the IGM, but is difficult to explain with plausible models for reionization. Demonstrate that the observed reduction in Lya flux from galaxies at z>6 can be explained by evolution in the escape fraction of ionizing photons, f_esc. Find: median observed drop in the fraction of galaxies showing strong Lya emission, as well as the observed evolution of the Lya LF both follow from a small increase in f_esc of Delta f_esc~0.1 from f_esc~0.6 at z~6. This high escape fraction may be at odds with current constraints n the ionizing photon escape fraction, which favor smaller values of f_esc<20%. However, models that invoke a redshift evolution of f_esc that is consistent with these constraints can suppress the z~7 Lya flux to the observed level, if they also include a small evolution in global neutral fraction of Delta x_HI~0.2. Thus an evolving escape fraction of ionizing photons can be a plausible part of the explanation for evolution in the Lya emission of high z galaxies. More generally, analysis also shows that the drop in the Lya fraction is quantitatively consistent with the observed evolution in the Lya LF of Lya emitters.
1401.7695
Modeling AGN feedback in cool-core clusters: the balance between heating and cooling
Li, Bryan
3d high-res (60pc) AMR sims of idealized cool-core cluster. AGN feedback, jet power calculated based on accretion rate of cold gas near the SMBH. ICM first cools into clumps along the propagation direction of the AGN jets. As the jet power increases, gas condensation occurs isotropically, forming spatially extended (up to a few tens kpc) structures that resemble the observed Ha filaments in Perseus and many other cool-core cluster. Jet heating elevates the gas entropy and cooling time, halting clump formation. The cold gas that is not accreted onto the SMBH settles into a rotating disk of ~1e11 Msun. The hot gas cools directly onto the cold disk while the SMBH accretes from the innermost region of the disk, powering the AGN that maintains a thermally balanced steady state for a few Gyr. The mass cooling rate averaged over 7Gyr is ~30 Msun/yr, an order of magnitude lower than the classic cooling flow value (obtained in runs w/o the AGN). Medium res sims produce similar results, but when the resolution is lower than 0.5 kpc, the cluster experiences cycles of gas condensation and AGN outbursts. Owing to its self-regulating mechanism, AGN feedback can successfully balance cooling with a wide range of model parameters. Besides suppressing cooling, model produces cold structures in early stages (up to ~2 Gyr) that are in good agreement with the observations. However, the log-lived massive cold disk is unrealistic, suggesting that additional physical processes are still needed.
1401.7711
GERLUMPH data release 1: high-resolution cosmological microlensing magnification maps and eResearch tools
Vernardos, Fluke, Bate, Croton
A new lensing map software, with 12342 high-res cosmo microlensing magnification maps [from sims?] and provides the first uniform coverage of the convergence, shear and smooth matter fraction parameter space. Use these maps to perform a comprehensive numerical investigation of the mass-sheet degeneracy, finding excellent agreement with predictions. Study the effect of smooth matter on microlensing induced magnification fluctuations. In particular, in the minima and saddle-point regions, fluctuations are enhanced only along the critical line, while in the maxima region they are always enhanced for high smooth matter fractions (~0.9). Describe approach to data management, including the use of an SWL database with web interface for data access and online analysis, obviating the need for individuals to download large volumes of data. In combination with existing observational databases and online applications, the GERLUMPH archive represents a fundamental component of a new microlensing eResearch cloud. Maps and tools are publicly available.
1401.7716
redMaPPer III: a detalied comparison of the Planck 2013 and SDSS DR8 RedMaPPer cluster catalogs
Rozo, Rykoff, Bartlett, Melin
Results highlight the power of multi-wavelength observations to identify and characterize systematic errors in galaxy cluster data sets, and clearly establish photometric data both as a robust cluster finding method, and as an important part of defining clean galaxy cluster samples. Intrinsic scatter of richness-SZ mass is 21%. 245 clusters in common; identify 3 failures in redMaPPer and 36 failures in the PSZ1; at least 12 are due to clusters whose optical counter part was correctly identified in the PSZ1, but where the quoted redshift for the optical counterpart in the external data base used in the PSZ1 was incorrect. Further identify 5 PSZ1 sources that suffer from projection effects (multiple rich systems along the LoS of the SZ detection) and 17 new high-z (z>0.6) cluster candidates of varying degrees of confidence. Should all of the high-z cluster candidates identified here be confirmed, will have tripled the number of high-z Planck clusters in the SDSS region.
1401.7813
Compact quiescent galaxies at intermediate redshifts
Hsu, Stockton, Shih
22 galaxies of 0.4<z<0.9; explore size, morphology, and stellar populations. Find most of the galaxies actually formed most of their stars at z<2, where the density of universe was lower than at high z. These young galaxies are less compact than those found at z>2 in the literature. Several of these young objects appear to be disk-like or possibly prolate (consistent with previous studies). If these galaxies were found to be confirmed to be disks, their formation would be more likely caused by gas accretion than by major mergers. On the other hand, if these galaxies were to be confirmed to be prolate, the fact that prolate galaxies do not exist in the local universe would indicate that galaxy formation mechanisms have evolved over cosmic time. Also find 6 galaxies with spectra indicating formation of >75% of their masses at z>2. 5 of them appear to have been modified over cosmic time, in agreement with the inside-out buildup of massive galaxies recently proposed in the literature. The remaining galaxy has a truly old stellar population, a very small size, and a disk-like morphology. This object would be a good candidate for a newly unmodified compact quiescent galaxy from high- that would be worth future study.
1401.7866
Evolution of the cosmic web
Cautun, van de Weygaert, Jones, Frenk
Web represent the transition stage between linear and NL structures and contains easily accessible information about the early phases of structure formation processes. Investigate the characteristics and the time evolution of morphological components since. Quantify cosmic web components in terms of their mass and volume content, their density distribution and halo populations. Employ new analysis techniques to determine the spatial extent of filaments and sheets, like their total length and local width. This analysis identifies cluster and filaments as the most prominent components of the web. In contrast, while voids and sheets take most of the volume, they correspond to under dense environments and are devoid of group-sized and more massive haloes. At early times the cosmos is denominated by tenuous filaments and sheets, which, later merge together, such that the present day web is dominated by fewer but much more massive structures. The analysis of the mass transport between environments clearly show how matter flows from voids into walls, and then via filaments into cluster regions, which form the nodes of the cosmic web. Also study the properties of individual filamentary branches, to find long, almost straight, filaments extending to distances larger than 100 Mpc/h. These constitute the bridges between massive clusters, which seem to form along approximately straight lines.
1401.7935
Detecting the first stars and black holes with 21-cm cosmology
Barkana
The significant relative velocity between the baryons and DM at early times suppress SF; the spatial variation of this suppression enhances large-scale clustering [why?] and produces a prominent cosmic web on 100 comoving Mpc scales in the 21-cm intensity distribution. This structure makes it much more feasible for radio astronomers to detect these early stars, and should drive a new focus on the era t~200 Myr, which is rich with little-explored astrophysics.
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