200 research outputs found
Gibson\u27s Passion: A Case Study in Media Manipulation?
The question I have posed for myself - Is this a case of media manipulation? - is complicated by the fact that we are dealing here with two huge institutional nexuses, Hollywood and the Roman Catholic Church, that both have a longstanding and, one might say, radical commitment to managing any and all news about themselves. This means that, in each case, it is far from easy to establish the truth of what they are up to in order to determine the extent of the possible manipulation. Or, more charitably, one might say that both institutional nexuses are dedicated to the proposition that the truths of art and the truths of faith, respectively, may not always be best served by disclosing the truths about the people and institutions responsible for serving them up
Galaxy Quenching from Cosmic Web Detachment
We propose the Cosmic Web Detachment (CWD) model, a framework to interpret
the star-formation history of galaxies in a cosmological context. The CWD model
unifies several starvation mechanisms known to disrupt or stop star formation
into one single physical framework. Galaxies begin accreting star-forming gas
at early times via a network of primordial filaments, simply related to the
pattern of density fluctuations in the initial conditions. But when
shell-crossing occurs on intergalactic scales, this pattern is disrupted, and
the galaxy detaches from its primordial filaments, ending the accretion of cold
gas. We argue that CWD encompasses known external processes halting star
formation, such as harassment, strangulation and starvation. On top of these
external processes, internal feedback processes such as AGN contribute to stop
in star formation as well.
By explicitly pointing out the non-linear nature of CWD events we introduce a
simple formalism to identify CWD events in N-body simulations. With it we
reproduce and explain, in the context of CWD, several observations including
downsizing, the cosmic star formation rate history, the galaxy mass-color
diagram and the dependence of the fraction of red galaxies with mass and local
density.Comment: 20 pages, accepted for publication in OJA. High-res version:
http://skysrv.pha.jhu.edu/~miguel/Papers/CWD/ms.pd
Religion in American Public Life (with transcript)
Sarah Gordon and Mark Silk look at how the U.S. has historically regulated religious institutions as well as accounted for an individualâs religious liberty
Religion in American Public Life (with transcript)
Sarah Gordon and Mark Silk look at how the U.S. has historically regulated religious institutions as well as accounted for an individualâs religious liberty
Red Galaxy Growth and the Halo Occupation Distribution
We have traced the past 7 Gyr of red galaxy stellar mass growth within dark
matter halos. We have determined the halo occupation distribution, which
describes how galaxies reside within dark matter halos, using the observed
luminosity function and clustering of 40,696 0.2<z<1.0 red galaxies in Bootes.
Half of 10^{11.9} Msun/h halos host a red central galaxy, and this fraction
increases with increasing halo mass. We do not observe any evolution of the
relationship between red galaxy stellar mass and host halo mass, although we
expect both galaxy stellar masses and halo masses to evolve over cosmic time.
We find that the stellar mass contained within the red population has doubled
since z=1, with the stellar mass within red satellite galaxies tripling over
this redshift range. In cluster mass halos most of the stellar mass resides
within satellite galaxies and the intra-cluster light, with a minority of the
stellar mass residing within central galaxies. The stellar masses of the most
luminous red central galaxies are proportional to halo mass to the power of a
third. We thus conclude that halo mergers do not always lead to rapid growth of
central galaxies. While very massive halos often double in mass over the past 7
Gyr, the stellar masses of their central galaxies typically grow by only 30%.Comment: Accepted for publication in the ApJ. 34 pages, 22 Figures, 5 Table
Correlations Between Central Massive Objects And Their Host Galaxies: From Bulgeless Spirals to Ellipticals
Recent observations by Ferrarese et al. (2006) and Wehner et al. (2006)
reveal that a majority of galaxies contain a central massive object (CMO),
either a supermassive black hole (SMBH) or a compact stellar nucleus,
regardless of the galaxy mass or morphological type, and that there is a tight
relation between the masses of CMOs and those of the host galaxies. Several
recent studies show that feedback from black holes can successfully explain the
\msigma correlation in massive elliptical galaxies that contain SMBHs.
However, puzzles remain in spirals or dwarf spheroids that do not appear to
have black holes but instead harbor a compact central stellar cluster. Here we
use three-dimensional, smoothed particle hydrodynamics simulations of isolated
galaxies to study the formation and evolution of CMOs in bulgeless disk
galaxies, and simulations of merging galaxies to study the transition of the
CMO--host mass relation from late-type bulgeless spirals to early-type
ellipticals. Our results suggest that the observed correlations may be
established primarily by the depletion of gas in the central region by
accretion and star-formation, and may hold for all galaxy types. A systematic
search for CMOs in the nuclei of bulgeless disk galaxies would offer a test of
this conclusion. (Abridged)Comment: 11 pages, 8 figures, accepted to Ap
Corrections to Bino Annihilation I: Sfermion Mixing
We consider corrections to bino annihilation due to sfermion mixing.Comment: 11 pages in LaTex plus 4 postscript figures (included),
CfPA--93--th--21, UMN--TH--1205/9
Giant Lya nebulae associated with high redshift radio galaxies
We report deep Keck narrow-band Lya images of the luminous z > 3 radio
galaxies 4C 41.17, 4C 60.07, and B2 0902+34. The images show giant, 100-200 kpc
scale emission line nebulae, centered on these galaxies, which exhibit a wealth
of morphological structure, including extended low surface brightness emission
in the outer regions, radially directed filaments, cone-shaped structures and
(indirect) evidence for extended Lya absorption. We discuss these features
within a general scenario where the nebular gas cools gravitationally in large
Cold Dark Matter (CDM) halos, forming stars and multiple stellar systems.
Merging of these ``building'' blocks triggers large scale starbursts, forming
the stellar bulges of massive radio galaxy hosts, and feeds super-massive black
holes which produce the powerful radio jets and lobes. The radio sources,
starburst superwinds and AGN radiation then disrupt the accretion process
limiting galaxy and black hole growth, and imprint the observed filamentary and
cone-shaped structures of the Lya nebulae.Comment: 36 Pages, including 8 Postscript figures. Accepted for publication in
the Astrophysical Journa
Galaxy Zoo: dust lane early-type galaxies are tracers of recent, gas-rich minor mergers
We present the second of two papers concerning the origin and evolution of
local early-type galaxies exhibiting dust features. We use optical and radio
data to examine the nature of active galactic nucleus (AGN) activity in these
objects, and compare these with a carefully constructed control sample. We find
that dust lane early-type galaxies are much more likely to host emission-line
AGN than the control sample galaxies. Moreover, there is a strong correlation
between radio and emission-line AGN activity in dust lane early-types, but not
the control sample. Dust lane early-type galaxies show the same distribution of
AGN properties in rich and poor environments, suggesting a similar triggering
mechanism. By contrast, this is not the case for early-types with no dust
features. These findings strongly suggest that dust lane early-type galaxies
are starburst systems formed in gas-rich mergers. Further evidence in support
of this scenario is provided by enhanced star formation and black hole
accretion rates in these objects. Dust lane early-types therefore represent an
evolutionary stage between starbursting and quiescent galaxies. In these
objects, the AGN has already been triggered but has not as yet completely
destroyed the gas reservoir required for star formation.Comment: 11 pages, 18 figures, 4 tables, MNRAS (Accepted for publication- 2012
January 19
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