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Line-of-sight effects in strong gravitational lensing by Pierre Fleury et al. on Wednesday 30 November
While most strong-gravitational-lensing systems may be roughly modelled by a
single massive object between the source and the observer, in the details all
the structures near the light path contribute to the observed images. These
additional contributions, known as line-of-sight effects, are non-negligible in
practice. This article proposes a new theoretical framework to model the
line-of-sight effects, together with very promising applications at the
interface of weak and strong lensing. Our approach relies on the dominant-lens
approximation, where one deflector is treated as the main lens while the others
are treated as perturbations. The resulting framework is technically simpler to
handle than the multi-plane lensing formalism, while allowing one to
consistently model any sub-critical perturbation. In particular, it is not
limited to the usual external-convergence and external-shear parameterisation.
As a first application, we identify a specific notion of line-of-sight shear
that is not degenerate with the ellipticity of the main lens, and which could
thus be extracted from strong-lensing images. This result supports and improves
the recent proposal that Einstein rings might be powerful probes of cosmic
shear. As a second application, we investigate the distortions of
strong-lensing critical curves under line-of-sight effects, and more
particularly their correlations across the sky. We find that such correlations
may be used to probe, not only the large-scale structure of the Universe, but
also the dark-matter halo profiles of strong lenses. This last possibility
would be a key asset to improve the accuracy of the measurement of the
Hubble-Lema\^itre constant via time-delay cosmography.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2104.08883v5
The diversity of rotation curves of simulated galaxies with cusps and cores by Finn A. Roper et al. on Wednesday 30 November
We use $\Lambda$CDM cosmological hydrodynamical simulations to explore the
kinematics of gaseous discs in late-type dwarf galaxies. We create
high-resolution 21-cm 'observations' of simulated dwarfs produced in two
variations of the EAGLE galaxy formation model: one where supernova-driven gas
flows redistribute dark matter and form constant-density central 'cores', and
another where the central 'cusps' survive intact. We 'observe' each galaxy
along multiple sight lines and derive a rotation curve for each observation
using a conventional tilted-ring approach to model the gas kinematics. We find
that the modelling process introduces systematic discrepancies between the
recovered rotation curve and the actual circular velocity curve driven
primarily by (i) non-circular gas orbits within the discs; (ii) the finite
thickness of gaseous discs, which leads to overlap of different radii in
projection; and (iii) departures from dynamical equilibrium. Dwarfs with dark
matter cusps often appear to have a core, whilst the inverse error is less
common. These effects naturally reproduce an observed trend which other models
struggle to explain: late-type dwarfs with more steeply-rising rotation curves
appear to be dark matter-dominated in the inner regions, whereas the opposite
seems to hold in galaxies with core-like rotation curves. We conclude that if
similar effects affect the rotation curves of observed dwarfs, a late-type
dwarf population in which all galaxies have sizeable dark matter cores is most
likely incompatible with current measurements.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2203.16652v3
Accurate modelling of extragalactic microlensing by compact objects by Víctor Boscá et al. on Wednesday 30 November
Microlensing of extragalactic sources, in particular the probability of
significant amplifications, is a potentially powerful probe of the abundance of
compact objects outside the halo of the Milky Way. Accurate experimental
constraints require an equally accurate theoretical model for the amplification
statistics produced by such a population. In this article, we argue that the
simplest (strongest-lens) model does not meet this demanding requirement. We
thus propose an elaborate practical modelling scheme for extragalactic
microlensing. We derive from first principles an expression for the
amplification probability that consistently allows for: (i) the coupling
between microlenses; (ii) realistic perturbations from the cosmic large-scale
structure; (iii) extended-source corrections. An important conclusion is that
the external shear applied on the dominant microlens, both by the other lenses
and by the large-scale structure, is practically negligible. Yet, the
predictions of our approach can still differ by a factor of a few with respect
to existing models of the literature. Updated constraints on the abundance of
compact objects accounting for such discrepancies may be required.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2205.00991v2
Constraints on dark matter annihilation and decay from the large-scale structure of the nearby universe by Deaglan J. Bartlett et al. on Wednesday 30 November
Decaying or annihilating dark matter particles could be detected through
gamma-ray emission from the species they decay or annihilate into. This is
usually done by modelling the flux from specific dark matter-rich objects such
as the Milky Way halo, Local Group dwarfs, and nearby groups. However, these
objects are expected to have significant emission from baryonic processes as
well, and the analyses discard gamma-ray data over most of the sky. Here we
construct full-sky templates for gamma-ray flux from the large-scale structure
within $\sim$200 Mpc by means of a suite of constrained $N$-body simulations
(CSiBORG) produced using the Bayesian Origin Reconstruction from Galaxies
algorithm. Marginalising over uncertainties in this reconstruction, small-scale
structure, and parameters describing astrophysical contributions to the
observed gamma-ray sky, we compare to observations from the Fermi Large Area
Telescope to constrain dark matter annihilation cross sections and decay rates
through a Markov Chain Monte Carlo analysis. We rule out the thermal relic
cross section for $s$-wave annihilation for all $m_\chi \lesssim 7 {\rm \,
GeV}/c^2$ at 95\% confidence if the annihilation produces gluons or quarks less
massive than the bottom quark. We infer a contribution to the gamma-ray sky
with the same spatial distribution as dark matter decay at $3.3\sigma$.
Although this could be due to dark matter decay via these channels with a decay
rate $\Gamma \approx 6 \times 10^{-28} {\rm \, s^{-1}}$, we find that a
power-law spectrum of index $p=-2.75^{+0.71}_{-0.46}$, likely of baryonic
origin, is preferred by the data.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2205.12916v2
On the ages of bright galaxies sim 500 Myr after the Big Bang: insights into star formation activity at z gtrsim 15 with JWST by Lily Whitler et al. on Wednesday 30 November
With JWST, new opportunities to study the evolution of galaxies in the early
Universe are emerging. Spitzer constraints on rest-optical properties of
$z\gtrsim7$ galaxies demonstrated the power of using galaxy stellar masses and
star formation histories (SFHs) to indirectly infer the cosmic star formation
history. However, only the brightest individual $z\gtrsim8$ objects could be
detected with Spitzer, making it difficult to robustly constrain activity at
$z\gtrsim10$. Here, we leverage the greatly improved rest-optical sensitivity
of JWST at $z\gtrsim8$ to constrain the ages of seven UV-bright
($M_{UV}\lesssim-19.5$) galaxies selected to lie at $z\sim8.5-11$, then
investigate implications for $z\gtrsim15$ star formation. We infer the
properties of individual objects with two spectral energy distribution
modelling codes, then infer a distribution of ages for bright $z\sim8.5-11$
galaxies. We find a median age of $\sim20$ Myr, younger than that inferred at
$z\sim7$ with a similar analysis, consistent with an evolution towards larger
specific star formation rates at early times. The age distribution suggests
that only $\sim3$ percent of bright $z\sim8.5-11$ galaxies would be similarly
luminous at $z\gtrsim15$, implying that the number density of bright galaxies
declines by at least an order of magnitude between $z\sim8.5-11$ and $z\sim15$.
This evolution is challenging to reconcile with some early JWST results
suggesting the abundance of bright galaxies does not significantly decrease
towards very early times, but we suggest this tension may be eased if young
stellar populations form on top of older stellar components, or if bright
$z\sim15$ galaxies are observed during a burst of star formation.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2208.01599v2
Shock-induced stripping of satellite ISM CGM in IllustrisTNG clusters at z sim0 by Hao Li et al. on Wednesday 30 November
Using the IllustrisTNG simulation, we study the interaction of large-scale
shocks with the circumgalactic medium (CGM) and interstellar medium (ISM) of
star-forming (SF) satellite galaxies in galaxy clusters. These shocks are
usually produced by mergers and massive accretion. Our visual inspection shows
that approximately half of SF satellites have encountered shocks in their host
clusters at $z\leq0.11$. After a satellite crosses a shock front and enters the
postshock region, the ram pressure on it is boosted significantly. Both the CGM
and ISM can be severely impacted, either by striping or compression. The
stripping of the ISM is particularly important for low-mass galaxies with $\log
(M_{*}/M_{\odot})<10$ and can occur even in the outskirts of galaxy clusters.
In comparison, satellites that do not interact with shocks lose their ISM only
in the inner regions of clusters. About half of the ISM is stripped within
about 0.6 Gyr after it crosses the shock front. Our results show that
shock-induced stripping plays an important role in quenching satellite galaxies
in clusters.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.07711v2
ALMACAL IX: multi-band ALMA survey for dusty star-forming galaxies and the resolved fractions of the cosmic infrared background by Jianhang Chen et al. on Wednesday 30 November
Wide, deep, blind continuum surveys at submillimetre/millimetre (submm/mm)
wavelengths are required to provide a full inventory of the dusty, distant
Universe. However, conducting such surveys to the necessary depth, with
sub-arcsec angular resolution, is prohibitively time-consuming, even for the
most advanced submm/mm telescopes. Here, we report the most recent results from
the ALMACAL project, which exploits the 'free' calibration data from the
Atacama Large Millimetre/submillimetre Array (ALMA) to map the lines of sight
towards and beyond the ALMA calibrators. ALMACAL has now covered 1,001
calibrators, with a total sky coverage around 0.3 deg2, distributed across the
sky accessible from the Atacama desert, and has accumulated more than 1,000h of
integration. The depth reached by combining multiple visits to each field makes
ALMACAL capable of searching for faint, dusty, star-forming galaxies (DSFGs),
with detections at multiple frequencies to constrain the emission mechanism.
Based on the most up-to-date ALMACAL database, we report the detection of 186
DSFGs with flux densities down to S870um ~ 0.2mJy, comparable with existing
ALMA large surveys but less susceptible to cosmic variance. We report the
number counts at five wavelengths between 870um and 3mm, in ALMA bands 3, 4, 5,
6 and 7, providing a benchmark for models of galaxy formation and evolution. By
integrating the observed number counts and the best-fitting functions, we also
present the resolved fraction of the cosmic infrared background (CIB) and the
CIB spectral shape. Combining existing surveys, ALMA has currently resolved
about half of the CIB in the submm/mm regime.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.09329v2
Panchromatic HST WFC3 Imaging Studies of Young, Rapidly Evolving Planetary Nebulae II NGC 7027 by Paula Moraga Baez et al. on Wednesday 30 November
The iconic planetary nebula (PN) NGC 7027 is bright, nearby (D ~ 1 kpc),
highly ionized, intricately structured, and well observed. This nebula is hence
an ideal case study for understanding PN shaping and evolution processes.
Accordingly, we have conducted a comprehensive imaging survey of NGC 7027
comprised of twelve HST Wide Field Camera 3 images in narrow-band and continuum
filters spanning the wavelength range 0.243--1.67 microns. The resulting
panchromatic image suite reveals the spatial distributions of emission lines
covering low-ionization species such as singly ionized Fe, N, and Si, through H
recombination lines, to more highly ionized O and Ne. These images, combined
with available X-ray and radio data, provide the most extensive view of the
structure of NGC 7027 obtained to date. Among other findings, we have traced
the ionization structure and dust extinction within the nebula in sub-arcsecond
detail; uncovered multipolar structures actively driven by collimated winds
that protrude through and beyond the PN's bright inner core; compared the
ionization patterns in the WFC3 images to X-ray and radio images of its
interior hot gas and to its molecular outflows; pinpointed the loci of thin,
shocked interfaces deep inside the nebula; and more precisely characterized the
central star. We use these results to describe the recent history of this young
and rapidly evolving PN in terms of a series of shaping events. This
evolutionary sequence involves both thermal and ram pressures, and is far more
complex than predicted by extant models of UV photoionization or winds from a
single central progenitor star, thereby highlighting the likely influence of an
unseen binary companion.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.01859v2
The Circumgalactic Medium of Milky Way-like Galaxies in the TNG50 Simulation -- I: Halo Gas Properties and the Role of SMBH Feedback by Rahul Ramesh et al. on Wednesday 30 November
We analyze the physical properties of gas in the circumgalactic medium (CGM)
of 132 Milky Way (MW)-like galaxies at $z=0$ from the cosmological
magneto-hydrodynamical simulation TNG50, part of the IllustrisTNG project. The
properties and abundance of CGM gas across the sample are diverse, and the
fractional budgets of different phases (cold, warm, and hot), as well as
neutral HI mass and metal mass, vary considerably. Over our stellar mass range
of $10^{10.5} < M_\star / \rm{M}_\odot < 10^{10.9}$, radial profiles of gas
physical properties from $0.15 < R\rm{ / R_{\rm 200c}} < 1.0$ reveal great CGM
structural complexity, with significant variations both at fixed distance
around individual galaxies, and across different galaxies. CGM gas is
multi-phase: the distributions of density, temperature and entropy are all
multimodal, while metallicity and thermal pressure distributions are unimodal;
all are broad. We present predictions for magnetic fields in MW-like halos: a
median field strength of $|B|\sim\,1\mu$G in the inner halo decreases rapidly
at larger distance, while magnetic pressure dominates over thermal pressure
only within $\sim0.2 \times \rm{R_{200c}}$. Virial temperature gas at $\sim
10^6\,$K coexists with a sub-dominant cool, $< 10^5\,$K component in
approximate pressure equilibrium. Finally, the physical properties of the CGM
are tightly connected to the galactic star formation rate, in turn dependent on
feedback from supermassive black holes (SMBHs). In TNG50, we find that energy
from SMBH-driven kinetic winds generates high-velocity outflows ($\gtrsim
500-2000$ km/s), heats gas to super-virial temperatures ($> 10^{6.5-7}$ K), and
regulates the net balance of inflows versus outflows in otherwise quasi-static
gaseous halos.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.00020v2
Growth of A Massive Black Hole Via Tidal Disruption Accretion by Seungjae Lee et al. on Wednesday 30 November
Stars that are tidally disrupted by the massive black hole (MBH) may
contribute significantly to the growth of the MBH, especially in dense nuclear
star clusters (NSCs). Yet, this tidal disruption accretion (TDA) of stars onto
the MBH has largely been overlooked compared to the gas accretion (GA) channel
in most numerical experiments until now. In this work, we implement a black
hole growth channel via TDA in the high-resolution adaptive mesh refinement
code Enzo to investigate its influence on a MBH seed's early evolution. We find
that a MBH seed grows rapidly from $10^3\,\mathrm{M}_\odot$ to $\gtrsim
10^6\,\mathrm{M}_\odot$ in 200\,Myrs in some of the tested simulations.
Compared to a MBH seed that grows only via GA, TDA can enhance the MBH's growth
rate by up to more than an order of magnitude. However, as predicted, TDA
mainly helps the early growth of the MBH (from $10^{3-4}\,\mathrm{M}_\odot$ to
$\lesssim10^{5}\,\mathrm{M}_\odot$) while the later evolution is generally
dominated by GA. We also observe that the star formation near the MBH is
suppressed when TDA is most active, sometimes with a visible cavity in gas (of
size $\sim$ a few pc) created in the vicinity of the MBH. It is because the MBH
may grow expeditiously with both GA and TDA, and the massive MBH could consume
its neighboring gas faster than being replenished by gas inflows. Our study
demonstrates the need to consider different channels of black hole accretion
that may provide clues for the existence of supermassive black holes at high
redshifts.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.02376v2
Mirror Dark Sector Solution of the Hubble Tension with Time-varying Fine-structure Constant by John Zhang et al. on Wednesday 30 November
We explore a model introduced by Cyr-Racine, Ge, and Knox
(arXiv:2107.13000(2)) that resolves the Hubble tension by invoking a ``mirror
world" dark sector with energy density a fixed fraction of the ``ordinary"
sector of Lambda-CDM. Although it reconciles cosmic microwave background and
large-scale structure observations with local measurements of the Hubble
constant, the model requires a value of the primordial Helium mass fraction
that is discrepant with observations and with the predictions of Big Bang
Nucleosynthesis (BBN). We consider a variant of the model with standard Helium
mass fraction but with the value of the electromagnetic fine-structure constant
slightly different during photon decoupling from its present value. If $\alpha$
at that epoch is lower than its current value by $\Delta \alpha \simeq -2\times
10^{-5}$, then we can achieve the same Hubble tension resolution as in
Cyr-Racine, et al. but with consistent Helium abundance. As an example of such
time-evolution, we consider a toy model of an ultra-light scalar field, with
mass $m <4\times 10^{-29}$ eV, coupled to electromagnetism, which evolves after
photon decoupling and that appears to be consistent with late-time constraints
on $\alpha$ variation.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.03236v2
Microlensing of gravitational waves by dark matter structures by Malcolm Fairbairn et al. on Wednesday 30 November
Gravitational lensing of gravitational waves provides a potential new probe
of dark matter structures. In this work, we consider the microlensing effect on
gravitational wave signals from black hole binaries induced by low-mass dark
matter halos that do not retain enough baryonic matter to hold stars. We
clarify systematically when this microlensing effect is relevant and study in
detail its detectability by future gravitational wave observatories. We
consider lensing by cold dark matter halos and by solitonic cores that reside
in fuzzy dark matter halos. Our results show that although the effect can be
detectable at relatively large impact parameters, the probability of detecting
such lensed events is low. In particular, we find that the expected number of
events lensed by cold dark matter halos is $\mathcal{O}(0.01)$ per year for BBO
and the expected number of events lensed by solitonic cores inside fuzzy dark
matter halos is $\mathcal{O}(0.01)$ per year for ET. In the case that a
significant fraction of dark matter consists of $\mathcal{O}(100 M_\odot)$
objects that are relatively compact, $R < \mathcal{O}(0.1\,{\rm pc})$, we show
that the expected number of lensed events per year ET can be very large,
$\mathcal{O}(1000)$.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.13436v2
A bias-free cosmological analysis with quasars alleviating H 0 tension by Aleksander Łukasz Lenart et al. on Wednesday 30 November
Cosmological models and their parameters are widely debated because of
theoretical and observational mismatches of the standard cosmological model,
especially the current discrepancy between the value of the Hubble constant,
$H_{0}$, obtained by Type Ia supernovae (SNe Ia), and the Cosmic Microwave
Background Radiation (CMB). Thus, considering high-redshift probes like quasars
(QSOs), having intermediate redshifts between SNe Ia and CMB, is a necessary
step. In this work, we use SNe Ia and the most updated QSO sample, reaching
redshifts up to $z\sim7.5$, applying the Risaliti-Lusso QSO relation based on a
non-linear relation between ultraviolet and X-ray luminosities. We consider
this relation both in its original form and corrected for selection biases and
evolution in redshift through a reliable statistical method also accounting for
the circularity problem. We also explore two approaches: with and without
calibration on SNe Ia. We then investigate flat and non-flat standard
cosmological models and a flat $w$CDM model, with a constant dark energy
equation of state parameter $w$. Remarkably, when correcting for the evolution
as a function of cosmology, we obtain closed constraints on $\Omega_M$ using
only non-calibrated QSOs. We find that considering non-calibrated QSOs combined
with SNe Ia and accounting for the same correction, our results are compatible
with a flat $\Lambda$CDM model with $\Omega_M = 0.3$ and $H_0 = 70 \,
\mathrm{km\,s^{-1}\,Mpc^{-1}}$. Intriguingly, the $H_0$ values obtained place
halfway between the one from SNe Ia and CMB, paving the way for new insights
into the $H_0$ tension.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.10785v2
iMaNGA: mock MaNGA galaxies based on IllustrisTNG and MaStar SSPs II the catalogue by Lorenza Nanni et al. on Wednesday 30 November
To test the current theory on galaxy formation and evolution, it is essential
to strengthening the synergy between simulations and observations. For this
reason, in our previous paper of this series, we presented a method to mock
SDSS-IV/MaNGA integral-field spectroscopic galaxy observations from
cosmological simulations of galaxy formation. Here we present the resulting
mock galaxy catalogue. This catalogue consists of 1,000 unique galaxies in
TNG50 falling into the SDSS-IV/MaNGA-Primary target footprint, defined in the
redshift and i-band absolute magnitude space, i.e. the iMaNGA sample. In this
paper, we describe the general characteristics of the catalogue, in terms of
morphology, kinematics, and stellar population properties. We also investigate
our ability to recover the galaxy characteristics, as given by the simulations,
analysing the synthetic spectra. We demonstrate that the `intrinsic' and
recovered stellar kinematics, and stellar age and metallicity are consistent
with zero within the 1$-{\sigma}$ level, for all the $\sim 8$ million tassels
in the iMaNGA sample presented in this paper. We also compare `intrinsic' and
recovered star formation histories, noting a strong resemblance. Therefore, our
mocking and spectral fitting processes do not distort `intrinsic' galaxy
properties, hence we can use these results for scientific analysis. In the
future papers of this series, we will present a comprehensive comparison and
scientific analysis of TNG50 simulations with MaNGA observational results.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.13146v2
Two lensed star candidates at z simeq4 8 behind the galaxy cluster MACS J0647 7+7015 by Ashish Kumar Meena et al. on Wednesday 30 November
We report the discovery of two extremely magnified lensed star candidates
behind the galaxy cluster MACS J0647.7+7015, in recent multi-band James Webb
Space Telescope (JWST) NIRCam observations. The candidates are seen in a
previously known, $z_{phot}\simeq4.8$ dropout giant arc that straddles the
critical curve. The candidates lie near the expected critical curve position
but lack clear counter images on the other side of it, suggesting these are
possibly stars undergoing caustic crossings. We present revised lensing models
for the cluster, including multiply imaged galaxies newly identified in the
JWST data, and use them to estimate a background macro-magnification of at
least $\gtrsim90$ and $\gtrsim50$ at the positions of the two candidates,
respectively. With these values, we expect effective, caustic-crossing
magnifications of $10^4-10^5$ for the two star candidates. The Spectral Energy
Distributions (SEDs) of the two candidates match well spectra of B-type stars
with best-fit surface temperatures of $\sim10,000$ K, and $\sim12,000$ K,
respectively, and we show that such stars with masses $\gtrsim20$ M$_{\odot}$
and $\gtrsim50$ M$_{\odot}$, respectively, can become sufficiently magnified to
be observed. We briefly discuss other alternative explanations and conclude
these are likely lensed stars, but also acknowledge that the less magnified
candidate may instead be or reside in a star cluster. These star candidates
constitute the second highest-redshift examples to date after Earendel at
$z_{phot}\simeq6.2$, establishing further the potential of studying extremely
magnified stars to high redshifts with the JWST. Planned visits including
NIRSpec observations will enable a more detailed view of the candidates already
in the near future.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.13334v2
Shattering and growth of cold clouds in galaxy clusters: the role of radiative cooling, magnetic fields and thermal conduction by Fred Jennings et al. on Wednesday 30 November
In galaxy clusters, the hot intracluster medium (ICM) can develop a striking
multi-phase structure around the brightest cluster galaxy. Much work has been
done on understanding the origin of this central nebula, but less work has
studied its eventual fate after the originally filamentary structure is broken
into individual cold clumps. In this paper we perform a suite of 30
(magneto-)hydrodynamical simulations of kpc-scale cold clouds with typical
parameters as found by galaxy cluster simulations, to understand whether clouds
are mixed back into the hot ICM or can persist. We investigate the effects of
radiative cooling, small-scale heating, magnetic fields, and (anisotropic)
thermal conduction on the long-term evolution of clouds. We find that filament
fragments cool on timescales shorter than the crushing timescale, fall out of
pressure equilibrium with the hot medium, and shatter, forming smaller
clumplets. These act as nucleation sites for further condensation, and mixing
via Kelvin-Helmholtz instability, causing cold gas mass to double within 75
Myr. Cloud growth depends on density, as well as on local heating processes,
which determine whether clouds undergo ablation- or shattering-driven
evolution. Magnetic fields slow down but don't prevent cloud growth, with the
evolution of both cold and warm phase sensitive to the field topology.
Counter-intuitively, anisotropic thermal conduction increases the cold gas
growth rate compared to non-conductive clouds, leading to larger amounts of
warm phase as well. We conclude that dense clumps on scales of $500$ pc or more
cannot be ignored when studying the long-term cooling flow evolution of galaxy
clusters.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.09183v2
Peering into the Milky Way by FAST: I Exquisite HI structures in the inner Galactic disk from the piggyback line observations of the FAST GPPS survey by Tao Hong et al. on Wednesday 30 November
Neutral hydrogen (HI) is the fundamental component of the interstellar
medium. The Galactic Plane Pulsar Snapshot (GPPS) survey is designed for
hunting pulsars by using the Five-hundred-meter Aperture Spherical radio
Telescope (FAST) from the visible Galactic plane within $|b| \leq 10^{\circ}$.
The survey observations are conducted with the L-band 19-beam receiver in the
frequency range of 1.0 $-$ 1.5 GHz, and each pointing has an integration time
of 5 minutes. The piggyback spectral data simultaneously recorded during the
FAST GPPS survey are great resources for studies on the Galactic HI
distribution and ionized gas. We process the piggyback HI data of the FAST GPPS
survey in the region of $33^{\circ} \leq l \leq 55^{\circ}$ and $|b| \leq
2^{\circ}$. The rms of the data cube is found to be approximately 40 mK at a
velocity resolution of $0.1$ km s$^{-1}$, placing it the most sensitive
observations of the Galactic HI by far. The high velocity resolution and high
sensitivity of the FAST GPPS HI data enable us to detect weak exquisite HI
structures in the interstellar medium. HI absorption line with great details
can be obtained against bright continuum sources. The FAST GPPS survey
piggyback HI data cube will be released and updated on the web:
http://zmtt.bao.ac.cn/MilkyWayFAST/.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.11299v2
PHANGS-JWST First Results: Dust embedded star clusters in NGC 7496 selected via 3 3 μ m PAH emission by Jimena Rodriguez et al. on Wednesday 30 November
The earliest stages of star formation occur enshrouded in dust and are not
observable in the optical. Here we leverage the extraordinary new
high-resolution infrared imaging from JWST to begin the study of dust-embedded
star clusters in nearby galaxies throughout the local volume. We present a
technique for identifying dust-embedded clusters in NGC 7496 (18.7 Mpc), the
first galaxy to be observed by the PHANGS-JWST Cycle 1 Treasury Survey. We
select sources that have strong 3.3$\mu$m PAH emission based on a $\rm
F300M-F335M$ color excess, and identify 67 candidate embedded clusters. Only
eight of these are found in the PHANGS-HST optically-selected cluster catalog
and all are young (six have SED-fit ages of $\sim1$ Myr). We find that this
sample of embedded cluster candidates may significantly increase the census of
young clusters in NGC 7496 from the PHANGS-HST catalog -- the number of
clusters younger than $\sim$2 Myr could be increased by a factor of two.
Candidates are preferentially located in dust lanes, and are coincident with
peaks in PHANGS-ALMA CO (2-1) maps. We take a first look at concentration
indices, luminosity functions, SEDs spanning from 2700A to 21$\mu$m, and
stellar masses (estimated to be between $\sim10^4-10^5 M_{\odot}$). The methods
tested here provide a basis for future work to derive accurate constraints on
the physical properties of embedded clusters, characterize the completeness of
cluster samples, and expand analysis to all 19 galaxies in the PHANGS-JWST
sample, which will enable basic unsolved problems in star formation and cluster
evolution to be addressed.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.13426v2
Peering into the Milky Way by FAST: II Ionized gas in the inner Galactic disk revealed by the piggyback line observations of the FAST GPPS survey by L. G. Hou et al. on Wednesday 30 November
As one of the major components of the interstellar medium, the ionized gas in
our Milky Way, especially the low-density diffuse component, has not been
extensively observed in the radio band. The Galactic Plane Pulsar Snapshot
(GPPS) survey covers the sky area within the Galactic latitude of $\pm10^\circ$
around the Galactic plane visible by the Five-hundred-meter Aperture Spherical
radio Telescope (FAST), and the spectral line data are simultaneously recorded
during the pulsar survey observations. With an integration time of 5 minutes
for each beam, the GPPS survey project provides the most sensitive piggyback
spectra for tens of radio recombination lines (RRLs) in the band of 1000$-$1500
MHz for H$n\alpha$, He$n\alpha$, C$n\alpha$, as well as H$n\beta$ and
H$n\gamma$. We processed the spectral data of RRLs, and obtained a sensitive
averaged H$n\alpha$ RRL map of a sky area of 88 square degrees in the inner
Galaxy of 33$^\circ$ $\leqslant l \leqslant$ 55$^\circ$ and $|b| \leqslant$
2.0$^\circ$. The final spectral data of the H$n\alpha$ RRLs have a spatial
resolution of $\sim$3$^\prime$, a spectral resolution of 2.2 km s$^{-1}$, and a
typical spectral rms noise of 0.25 mJy beam$^{-1}$ or 6.3 mK in main-beam
brightness temperature. The new H$n\alpha$ RRL map shows complex structural
features dominated by a number of HII regions and large extended diffuse
ionized gas regions. We detect about 94% of the known HII regions and confirm
43 WISE HII regions in the observed sky area. Several large HII regions or
star-forming complexes in the distant outer Galaxy are resolved in the map of
H$n\alpha$ RRLs. Extended RRL features of the diffuse ionized gas are detected.
The RRL data products of the GPPS survey will be published and updated at
http://zmtt.bao.ac.cn/MilkyWayFAST/
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.11301v2
Peering into the Milky Way by FAST: III Magnetic fields in the Galactic halo and farther spiral arms revealed by the Faraday effect of faint pulsars by Jun Xu et al. on Wednesday 30 November
The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the most
sensitive radio telescope for pulsar observations. We make polarimetric
measurements of a large number of faint and distant pulsars using the FAST. We
present the new measurements of Faraday rotation for 134 faint pulsars in the
Galactic halo. Significant improvements are also made for some basic pulsar
parameters for 15 of them. We analyse the newly determined rotation measures
(RMs) for the Galactic magnetic fields by using these 134 halo pulsars,
together with previously available RMs for pulsars and extragalactic radio
sources and also the newly determined RMs for another 311 faint pulsars which
are either newly discovered in the project of the Galactic Plane Pulsar
Snapshot (GPPS) survey or previously known pulsars without RMs. The RM
tomographic analysis in the first Galactic quadrant gives roughly the same
field strength of around 2~$\mu$G for the large-scale toroidal halo magnetic
fields. The scale height of the halo magnetic fields is found to be at least
2.7$\pm$0.3~kpc. The RM differentiation of a large number of pulsars in the
Galactic disk in the Galactic longitude range of $26^{\circ}<90^{\circ}$
gives evidence for the clockwise magnetic fields (viewed from the north
Galactic pole) in two interarm regions inside the Scutum arm and between the
Scutum and Sagittarius arm, and the clockwise fields in the Local-Perseus
interarm region and field reversals in the Perseus arm and beyond.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.11302v2