429 research outputs found
Torque-Limited Growth of Massive Black Holes in Galaxies Across Cosmic Time
We combine cosmological hydrodynamic simulations with analytic models to
evaluate the role of galaxy-scale gravitational torques on the evolution of
massive black holes at the centers of star-forming galaxies. We confirm and
extend our earlier results to show that torque-limited growth yields black
holes and host galaxies evolving on average along the Mbh-Mbulge relation from
early times down to z = 0 and that convergence onto the scaling relation occurs
independent of the initial conditions and with no need for mass averaging
through mergers or additional self-regulation processes. Smooth accretion
dominates the long-term evolution, with black hole mergers with mass ratios
>1:5 representing typically a small fraction of the total growth. Winds from
the accretion disk are required to eject significant mass to suppress black
hole growth, but there is no need for coupling this wind to galactic-scale gas
to regulate black holes in a non-linear feedback loop. Torque-limited growth
yields a close-to-linear relation for the star formation rate and the black
hole accretion rate averaged over galaxy evolution time scales. However, the
SFR-AGN connection has significant scatter owing to strong variability of black
hole accretion at all resolved time scales. Eddington ratios can be described
by a broad lognormal distribution with median value evolving roughly as (1 +
z)^1.9, suggesting a main sequence for black hole growth similar to the cosmic
evolution of specific SFRs. Our results offer an attractive scenario consistent
with available observations in which cosmological gas infall and transport of
angular momentum in the galaxy by gravitational instabilities regulate the
long-term co-evolution of black holes and star-forming galaxies.Comment: 26 pages, 15 figures, replaced by published versio
Optimizing Private Land Conservation and Public Land Use Planning/Regulation
Report of the 2010 Berkley Workshop
Held at the Pocantico Conference Center of the Rockefeller Brothers Fund - July 201
An Observationally Driven Multifield Approach for Probing the Circum-Galactic Medium with Convolutional Neural Networks
The circum-galactic medium (CGM) can feasibly be mapped by multiwavelength
surveys covering broad swaths of the sky. With multiple large datasets becoming
available in the near future, we develop a likelihood-free Deep Learning
technique using convolutional neural networks (CNNs) to infer broad-scale
physical properties of a galaxy's CGM and its halo mass for the first time.
Using CAMELS (Cosmology and Astrophysics with MachinE Learning Simulations)
data, including IllustrisTNG, SIMBA, and Astrid models, we train CNNs on Soft
X-ray and 21-cm (HI) radio 2D maps to trace hot and cool gas, respectively,
around galaxies, groups, and clusters. Our CNNs offer the unique ability to
train and test on ''multifield'' datasets comprised of both HI and X-ray maps,
providing complementary information about physical CGM properties and improved
inferences. Applying eRASS:4 survey limits shows that X-ray is not powerful
enough to infer individual halos with masses . The multifield improves the inference for all halo masses. Generally,
the CNN trained and tested on Astrid (SIMBA) can most (least) accurately infer
CGM properties. Cross-simulation analysis -- training on one galaxy formation
model and testing on another -- highlights the challenges of developing CNNs
trained on a single model to marginalize over astrophysical uncertainties and
perform robust inferences on real data. The next crucial step in improving the
resulting inferences on physical CGM properties hinges on our ability to
interpret these deep-learning models
A Scramjet Engine Model Including Effects of Precombustion Shocks and Dissociation
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76382/1/AIAA-2008-4619-101.pd
Warming Climate Changes Vermont Disease
Introduction: •The average annual temperature in Vermont has gradual increased roughly 1° Centigrade with an increase of 1.16 inches of annual precipitation over the past 112 years. •According to expert analysis, humans are responsible for 60% of the warming overthe past 140 years. •Projected greater than 1° Centigrade increase in global temperature by 2100 and a correlated rise in precipitation. •Climate changes result in the introduction and reproduction of non-endemic flora and fauna. •Vector-borne diseases accompany warming trends and can become endemic and cause new illnesses in areas which were previously uninhabitable.https://scholarworks.uvm.edu/comphp_gallery/1006/thumbnail.jp
Large scale outflows from z ~ 0.7 starburst galaxies identified via ultra-strong MgII quasar absorption lines
(Abridged) Star formation-driven outflows are a critical phenomenon in
theoretical treatments of galaxy evolution, despite the limited ability of
observations to trace them across cosmological timescales. If the strongest
MgII absorption-line systems detected in the spectra of background quasars
arise in such outflows, "ultra-strong" MgII (USMgII) absorbers would identify
significant numbers of galactic winds over a huge baseline in cosmic time, in a
manner independent of the luminous properties of the galaxy. To this end, we
present the first detailed imaging and spectroscopic study of the fields of two
USMgII absorber systems culled from a statistical absorber catalog, with the
goal of understanding the physical processes leading to the large velocity
spreads that define such systems. Each field contains two bright emission-line
galaxies at similar redshift (dv < 300 km/s) to that of the absorption.
Lower-limits on their instantaneous star formation rates (SFR) from the
observed OII and Hb line fluxes, and stellar masses from spectral template
fitting indicate specific SFRs among the highest for their masses at z~0.7.
Additionally, their 4000A break and Balmer absorption strengths imply they have
undergone recent (~0.01 - 1 Gyr) starbursts. The concomitant presence of two
rare phenomena - starbursts and USMgII absorbers - strongly implies a causal
connection. We consider these data and USMgII absorbers in general in the
context of various popular models, and conclude that galactic outflows are
generally necessary to account for the velocity extent of the absorption. We
favour starburst driven outflows over tidally-stripped gas from a major
interaction which triggered the starburst as the energy source for the majority
of systems. Finally, we discuss the implications of these results and speculate
on the overall contribution of such systems to the global SFR density at z~0.7.Comment: 15 pages, 6 figure, accepted for publication by MNRA
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