7 research outputs found
The Launching of Cold Clouds by Galaxy Outflows III: The Influence of Magnetic Fields
Motivated by observations of outflowing galaxies, we investigate the combined
impact of magnetic fields and radiative cooling on the evolution of cold clouds
embedded in a hot wind. We perform a collection of three-dimensional adaptive
mesh refinement, magnetohydrodynamical simulations that span two resolutions,
and include fields that are aligned and transverse to the oncoming,
super-Alfv\'enic material. Aligned fields have little impact on the overall
lifetime of the clouds over the non-magnetized case, although they do increase
the mixing between the wind and cloud material by a factor of
Transverse fields lead to magnetic draping, which isolates the clouds, but they
also squeeze material in the direction perpendicular to the field lines, which
leads to rapid mass loss. A resolution study suggests that the magnetized
simulations have somewhat better convergence properties than non-magnetized
simulations, and that a resolution of 64 zones per cloud radius is sufficient
to accurately describe these interactions. We conclude that the combined
effects of radiative cooling and magnetic fields are dependent on field
orientation, but are unlikely to enhance cloud lifetimes beyond the effect of
radiative cooling alone.Comment: 15 pages, 14 figures, accepted to Ap
A New Model For Including Galactic Winds in Simulations of Galaxy Formation II: Implementation of PhEW in Cosmological Simulations
Although galactic winds play a critical role in regulating galaxy formation,
hydrodynamic cosmological simulations do not resolve the scales that govern the
interaction between winds and the ambient circumgalactic medium (CGM). We
implement the Physically Evolved Wind (PhEW) model of Huang et al. (2020) in
the GIZMO hydrodynamics code and perform test cosmological simulations with
different choices of model parameters and numerical resolution. PhEW adopts an
explicit subgrid model that treats each wind particle as a collection of clouds
that exchange mass, metals, and momentum with their surroundings and evaporate
by conduction and hydrodynamic instabilities as calibrated on much higher
resolution cloud scale simulations. In contrast to a conventional wind
algorithm, we find that PhEW results are robust to numerical resolution and
implementation details because the small scale interactions are defined by the
model itself. Compared to conventional wind simulations with the same
resolution, our PhEW simulations produce similar galaxy stellar mass functions
at but are in better agreement with low-redshift observations at because PhEW particles shed mass to the CGM before escaping
low mass halos. PhEW radically alters the CGM metal distribution because PhEW
particles disperse metals to the ambient medium as their clouds dissipate,
producing a CGM metallicity distribution that is skewed but unimodal and is
similar between cold and hot gas. While the temperature distributions and
radial profiles of gaseous halos are similar in simulations with PhEW and
conventional winds, these changes in metal distribution will affect their
predicted UV/X-ray properties in absorption and emission.Comment: 23 pages, 17 figures, MNRAS accepte
The Thermal Sunyaev-Zel'dovich Effect from Massive, Quiescent 0.5 z 1.5 Galaxies
We use combined South Pole Telescope (SPT)+Planck temperature maps to analyze
the circumgalactic medium (CGM) encompassing 138,235 massive, quiescent 0.5
z 1.5 galaxies selected from data from the Dark Energy Survey
(DES) and Wide-Field Infrared Survey Explorer (WISE). Images centered on these
galaxies were cut from the 1.85 arcmin resolution maps with frequency bands at
95, 150, and 220 GHz. The images were stacked, filtered, and fit with a
gray-body dust model to isolate the thermal Sunyaev-Zel'dovich (tSZ) signal,
which is proportional to the total energy contained in the CGM of the galaxies.
We separate these - galaxies
into 0.1 dex stellar mass bins, detecting tSZ per bin up to and a
total signal-to-noise ratio of . We also detect dust with an
overall signal-to-noise ratio of , which overwhelms the tSZ at
150GHz more than in other lower-redshift studies. We correct for the dex
uncertainty in the stellar mass measurements by parameter fitting for an
unconvolved power-law energy-mass relation, , with the peak stellar mass
distribution of our selected galaxies defined as . This yields an erg and .
These are consistent with observations and within the limits of
moderate models of active galactic nuclei (AGN) feedback. We also compute the
radial profile of our full sample, which is similar to that recently measured
at lower-redshift by Schaan et al. (2021).Comment: 23 pages, 9 figures, Accepted for publication in ApJ. Updated to
reflect minor change
The APOGEE-2 Survey of the Orion Star Forming Complex: I. Target Selection and Validation with early observations
The Orion Star Forming Complex (OSFC) is a central target for the APOGEE-2
Young Cluster Survey. Existing membership catalogs span limited portions of the
OSFC, reflecting the difficulty of selecting targets homogeneously across this
extended, highly structured region. We have used data from wide field
photometric surveys to produce a less biased parent sample of young stellar
objects (YSOs) with infrared (IR) excesses indicative of warm circumstellar
material or photometric variability at optical wavelengths across the full 420
square degrees extent of the OSFC. When restricted to YSO candidates with H <
12.4, to ensure S/N ~100 for a six visit source, this uniformly selected sample
includes 1307 IR excess sources selected using criteria vetted by Koenig &
Liesawitz and 990 optical variables identified in the Pan-STARRS1 3
survey: 319 sources exhibit both optical variability and evidence of
circumstellar disks through IR excess. Objects from this uniformly selected
sample received the highest priority for targeting, but required fewer than
half of the fibers on each APOGEE-2 plate. We fill the remaining fibers with
previously confirmed and new color-magnitude selected candidate OSFC members.
Radial velocity measurements from APOGEE-1 and new APOGEE-2 observations taken
in the survey's first year indicate that ~90% of the uniformly selected targets
have radial velocities consistent with Orion membership.The APOGEE-2 Orion
survey will include >1100 bona fide YSOs whose uniform selection function will
provide a robust sample for comparative analyses of the stellar populations and
properties across all sub-regions of Orion.Comment: Accepted for publication in ApJ