56 research outputs found
Turbulence in the Tail of a Jellyfish Galaxy
When galaxies move through the intracluster medium (ICM) inside galaxy
clusters, the ram pressure of the ICM can strip the gas from galaxies. The
stripped gas forms tails on the trailing side. These galaxies are hence dubbed
``jellyfish galaxies''. ESO 137-001 is a quintessential jellyfish galaxy
located in the nearest rich cluster, the Norma cluster. Its spectacular
multiphase tail has complex morphology and kinematics both from the imprinted
galaxy's interstellar medium (ISM) and as a result of the interactions between
the stripped gas and the surrounding hot plasma, mediated by radiative cooling
and magnetic fields. We study the kinematics of the multiphase tail using
high-resolution observations of the ionized and the molecular gas in the entire
structure. We calculate the velocity structure functions (VSFs) in moving
frames along the tail and find that turbulence driven by Kelvin-Helmholtz (KH)
instability quickly overwhelms the original ISM turbulence and saturates at
kpc. There is also a hint that the far end of the tail has possibly
started to inherit pre-existing large-scale ICM turbulence likely caused by
structure formation. Turbulence measured by the molecular gas is generally
consistent with that measured by the ionized gas in the tail but has a slightly
lower amplitude. Most of the measured turbulence is below the mean free path of
the hot ICM ( kpc). Using warm/cool gas as a tracer of the hot ICM, we
find that the isotropic viscosity of the hot plasma must be suppressed below
0.01 percent Spitzer level.Comment: 7 pages, 6 figures, accepted for publication in MNRA
The VIRUS-P Exploration of Nearby Galaxies (VENGA): Survey Design, Data Processing, and Spectral Analysis Methods
We present the survey design, data reduction, and spectral fitting pipeline
for the VIRUS-P Exploration of Nearby Galaxies (VENGA). VENGA is an integral
field spectroscopic survey, which maps the disks of 30 nearby spiral galaxies.
Targets span a wide range in Hubble type, star formation activity, morphology,
and inclination. The VENGA data-cubes have 5.6'' FWHM spatial resolution, ~5A
FWHM spectral resolution, sample the 3600A-6800A range, and cover large areas
typically sampling galaxies out to ~0.7 R_25. These data-cubes can be used to
produce 2D maps of the star formation rate, dust extinction, electron density,
stellar population parameters, the kinematics and chemical abundances of both
stars and ionized gas, and other physical quantities derived from the fitting
of the stellar spectrum and the measurement of nebular emission lines. To
exemplify our methods and the quality of the data, we present the VENGA
data-cube on the face-on Sc galaxy NGC 628 (a.k.a. M 74). The VENGA
observations of NGC 628 are described, as well as the construction of the
data-cube, our spectral fitting method, and the fitting of the stellar and
ionized gas velocity fields. We also propose a new method to measure the
inclination of nearly face-on systems based on the matching of the stellar and
gas rotation curves using asymmetric drift corrections. VENGA will measure
relevant physical parameters across different environments within these
galaxies, allowing a series of studies on star formation, structure assembly,
stellar populations, chemical evolution, galactic feedback, nuclear activity,
and the properties of the interstellar medium in massive disk galaxies.Comment: Accepted for publication in AJ, 25 pages, 18 figures, 6 table
The VIRUS-P Exploration of Nearby Galaxies (VENGA): Spatially resolved gas-phase metallicity distributions in barred and unbarred spirals
We present a study of the excitation conditions and metallicity of ionized gas (Zgas) in eight nearby barred and unbarred spiral galaxies from the VIRUS-P Exploration of Nearby Galaxies (VENGA) survey, which provides high spatial sampling and resolution (median ∼387 pc), large coverage from the bulge to outer disc, broad wavelength range (3600–6800 Å), and medium spectral resolution (∼120 km s−1 at 5000 Å). Our results are: (1) We present high resolution gas excitation maps to differentiate between regions with excitation typical of Seyfert, LINER, or recent star formation. We find LINER-type excitation at large distances (3–10 kpc) from the centre, and associate this excitation with diffuse ionized gas (DIG). (2) After excluding spaxels dominated by Seyfert, LINER, or DIG, we produce maps with the best spatial resolution and sampling to date of the ionization parameter q, star formation rate, and Zgas using common strong line diagnostics. We find that isolated barred and unbarred spirals exhibit similarly shallow Zgas profiles from the inner kpc out to large radii (7–10 kpc or 0.5–1.0 R25). This implies that if profiles had steeper gradients at earlier epochs, then the present-day bar is not the primary driver flattening gradients over time. This result contradicts earlier claims, but agrees with recent IFU studies. (3) The Zgas gradients in our z ∼ 0 massive spirals are markedly shallower, by ∼0.2 dex kpc−1, than published gradients for lensed lower mass galaxies at z ∼ 1.5–2.0. Cosmologically motivated hydrodynamical simulations best match this inferred evolution, but the match is sensitive to adopted stellar feedback prescriptions
Tracing the kinematics of the whole ram pressure stripped tails in ESO 137-001
Ram pressure stripping (RPS) is an important process to affect the evolution
of cluster galaxies and their surrounding environment. We present a large MUSE
mosaic for ESO 137-001 and its stripped tails, and study the detailed
distributions and kinematics of the ionized gas and stars. The warm, ionized
gas is detected to at least 87 kpc from the galaxy and splits into three tails.
There is a clear velocity gradient roughly perpendicular to the stripping
direction, which decreases along the tails and disappears beyond kpc
downstream. The velocity dispersion of the ionized gas increases to km
s at kpc downstream and stays flat beyond. The stars in the
galaxy disc present a regular rotation motion, while the ionized gas is already
disturbed by the ram pressure. Based on the observed velocity gradient, we
construct the velocity model for the residual galactic rotation in the tails
and discuss the origin and implication of its fading with distance. By
comparing with theoretical studies, we interpreted the increased velocity
dispersion as the result of the oscillations induced by the gas flows in the
galaxy wake, which may imply an enhanced degree of turbulence there. We also
compare the kinematic properties of the ionized gas and molecular gas from
ALMA, which shows they are co-moving and kinematically mixed through the tails.
Our study demonstrates the great potential of spatially resolved spectroscopy
in probing the detailed kinematic properties of the stripped gas, which can
provide important information for future simulations of RPS.Comment: 18 pages, 20 figures, 2 tables, accepted for publication in MNRA
HST viewing of spectacular star-forming trails behind ESO 137-001
We present the results from the HST WFC3 and ACS data on an archetypal galaxy
undergoing ram pressure stripping (RPS), ESO 137-001, in the nearby cluster
Abell 3627. ESO 137-001 is known to host a prominent stripped tail detected in
many bands from X-rays, Halpha to CO. The HST data reveal significant features
indicative of RPS such as asymmetric dust distribution and surface brightness
as well as many blue young star complexes in the tail. We study the correlation
between the blue young star complexes from HST, HII regions from Halpha (MUSE)
and dense molecular clouds from CO (ALMA). The correlation between the HST blue
star clusters and the HII regions is very good, while their correlation with
the dense CO clumps are typically not good, presumably due in part to
evolutionary effects. In comparison to the Starburst99+Cloudy model, many blue
regions are found to be young (< 10 Myr) and the total star formation (SF) rate
in the tail is 0.3 - 0.6 M_Sun/yr for sources measured with ages less than 100
Myr, about 40% of the SF rate in the galaxy. We trace SF over at least 100 Myr
and give a full picture of the recent SF history in the tail. We also
demonstrate the importance of including nebular emissions and a nebular to
stellar extinction correction factor when comparing the model to the broadband
data. Our work on ESO 137-001 demonstrates the importance of HST data for
constraining the SF history in stripped tails.Comment: 21 pages, 19 figures, 4 tables, re-submitted to MNRAS (initial
submission on Aug. 4, 2022
Joint profiling of DNA methylation and chromatin architecture in single cells.
We report a molecular assay, Methyl-HiC, that can simultaneously capture the chromosome conformation and DNA methylome in a cell. Methyl-HiC reveals coordinated DNA methylation status between distal genomic segments that are in spatial proximity in the nucleus, and delineates heterogeneity of both the chromatin architecture and DNA methylome in a mixed population. It enables simultaneous characterization of cell-type-specific chromatin organization and epigenome in complex tissues
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