542 research outputs found
Spatially resolved kinematics of the central regions of M83: hidden mass signatures and the role of supernovae
The barred grand-design spiral M83 (NGC 5236) is one of the most studied
galaxies given its proximity, orientation, and particular complexity.
Nonetheless, many aspects of the central regions remain controversial conveying
our limited understanding of the inner gas and stellar kinematics, and
ultimately of the nucleus evolution.
In this work, we present AO VLT-SINFONI data of its central ~235x140 pc with
an unprecedented spatial resolution of ~0.2 arcsec, corresponding to ~4 pc. We
have focused our study on the distribution and kinematics of the stars and the
ionised and molecular gas by studying in detail the Pa_alpha and Br_gamma
emission, the H_2 1-0S(1) line at 2.122 micron and the [FeII] line at 1.644
micron, together with the CO absorption bands at 2.293 micron and 2.323 micron.
Our results reveal a complex situation where the gas and stellar kinematics are
totally unrelated. Supernova explosions play an important role in shaping the
gas kinematics, dominated by shocks and inflows at scales of tens of parsecs
that make them unsuitable to derive general dynamical properties.
We propose that the location of the nucleus of M83 is unlikely to be related
to the off-centre 'optical nucleus'. The study of the stellar kinematics
reveals that the optical nucleus is a gravitationally bound massive star
cluster with M_dyn = (1.1 \pm 0.4)x10^7 M_sun, formed by a past starburst. The
kinematic and photometric analysis of the cluster yield that the stellar
content of the cluster is well described by an intermediate age population of
log T(yr) = 8.0\pm0.4, with a mass of M \simeq (7.8\pm2.4)x10^6 M_sun.Comment: 14 pages, 10 figures, accepted for publication in Ap
Spatially resolved kinematics, galactic wind, and quenching of star formation in the luminous infrared galaxy IRAS F11506-3851
We present a multi-wavelength integral field spectroscopic study of the low-z
LIRG IRAS F11506-3851, on the basis of VIMOS and SINFONI (ESO-VLT)
observations. The morphology and the 2D kinematics of the gaseous (neutral and
ionized) and stellar components have been mapped using the NaD doublet, the
H line, and the near-IR CO(2-0) and CO(3-1) bands. The kinematics of
the ionized gas and the stars are dominated by rotation, with large observed
velocity amplitudes and centrally peaked velocity dispersion maps. The stars
lag behind the warm gas and represent a dynamically hotter system, as indicated
by the observed dynamical ratios. Thanks to these IFS data we have disentangled
the contribution of the stars and the ISM to the NaD feature, finding that it
is dominated by the absorption of neutral gas clouds in the ISM. The neutral
gas 2D kinematics shows a complex structure dominated by two components. On the
one hand, the thick slowly rotating disk lags significantly compared to the
ionized gas and the stars, with an irregular and off-center velocity dispersion
map. On the other hand, a kpc-scale neutral gas outflow is observed along the
semi-minor axis of the galaxy, as revealed by large blueshifted velocities
(30-154 km/s). We derive an outflowing mass rate in neutral gas of about 48
/yr. Although this implies a global mass loading factor of
1.4, the 2D distribution of the ongoing SF suggests a much larger value of mass
loading factor associated with the inner regions (R200 pc), where the
current SF represents only 3 percent of the total. All together these results
strongly suggest that we are witnessing (nuclear) quenching due to SF feedback
in IRAS F11506-3851. However, the relatively large mass of molecular gas
detected in the nuclear region via the H2 1-0 S(1) line suggests that further
episodes of SF may take place again
Detection of an ionized gas outflow in the extreme UV-luminous star-forming galaxy BOSS-EUVLG1 at z=2.47
BOSS-EUVLG1 is the most ultraviolet (UV) and Ly luminous galaxy
detected so far in the Universe, going through a very active starburst phase,
and forming stars at a rate (SFR) of 955 118 M yr. We
report the detection of a broad H component carrying 25% of the total
H flux. The broad H line traces a fast and massive ionized gas
outflow characterized by a total mass, of 7.94
0.15, an outflowing velocity (V) of 573 151 km s,
and an outflowing mass rate () of 44 20 M
yr. The presence of the outflow in BOSS-EUVLG1 is also supported by the
identification of blueshifted UV absorption lines in low and high ionization
states. The energy involved in the H outflow can be explained by the
ongoing star formation without the need for an Active Galactic Nucleus. The
derived low mass loading factor (= 0.05 0.03) indicates that
although massive, this phase of the outflow can not be relevant for the
quenching of the star formation. In addition, only a small fraction (
15%) of the ionized outflowing material with velocities above 372 km s
could escape the gravitational potential, and enrich the surrounding
circum-galactic medium at distances above tens of kpc. The ionized phase of the
outflow does not carry the mass and energy to play a relevant role neither in
the evolution of the host galaxy nor in the enrichment of the intergalactic
medium. Other phases of the outflow could be carrying most of the outflow
energy and mass in the form of hot X-ray emitting gas as predicted by some
recent simulations. The expected emission of the extended X-ray emitting halo
associated with the outflow in BOSS-EUVLG1 and similar galaxies could be
detected with the future X-ray observatory, {\it ATHENA} but could not be
resolved spatially.Comment: 8 pages, 3 figures, accepted in A&
Note: "Lock-in accelerometry" to follow sink dynamics in shaken granular matter
Understanding the penetration dynamics of intruders in granular beds is
relevant not only for fundamental Physics, but also for geophysical processes
and construction on sediments or granular soils in areas potentially affected
by earthquakes. While the penetration of intruders in two dimensional (2D)
laboratory granular beds can be followed using video recording, it is useless
in three dimensional (3D) beds of non-transparent materials such as common
sand. Here we propose a method to quantify the sink dynamics of an intruder
into laterally shaken granular beds based on the temporal correlations between
the signals from a reference accelerometer fixed to the shaken granular bed,
and a probe accelerometer deployed inside the intruder. Due to its analogy with
the working principle of a lock in amplifier, we call this technique Lock in
accelerometry (LIA). During Earthquakes, some soils can lose their ability to
sustain shear and deform, causing subsidence and sometimes substantial building
damage due to deformation or tumblin
Chandra Observations of Extended X-ray Emission in Arp 220
We resolve the extended X-ray emission from the prototypical ultraluminous
infrared galaxy Arp 220. Extended, faint edge-brightened, soft X-ray lobes
outside the optical galaxy are observed to a distance of 10 to 15 kpc on each
side of the nuclear region. Bright plumes inside the optical isophotes coincide
with the optical line emission and extend 11 kpc from end to end across the
nucleus. The data for the plumes cannot be fit by a single temperature plasma,
and display a range of temperatures from 0.2 to 1 keV. The plumes emerge from
bright, diffuse circumnuclear emission in the inner 3 kpc centered on the
Halpha peak, which is displaced from the radio nuclei. There is a close
morphological correspondence between the Halpha and soft X-ray emission on all
spatial scales. We interpret the plumes as a starburst-driven superwind, and
discuss two interpretations of the emission from the lobes in the context of
simulations of the merger dynamics of Arp 220.Comment: Accepted for publication in ApJ; see also astro-ph/0208477 (Paper 1
Near-Infrared and Star-forming properties of Local Luminous Infrared Galaxies
We use HST NICMOS continuum and Pa-alpha observations to study the
near-infrared and star-formation properties of a representative sample of 30
local (d ~ 35-75Mpc) luminous infrared galaxies (LIRGs, infrared 8-1000um
luminosities of L_IR=11-11.9[Lsun]). The data provide spatial resolutions of
25-50pc and cover the central ~3.3-7.1kpc regions of these galaxies. About half
of the LIRGs show compact (~1-2kpc) Pa-alpha emission with a high surface
brightness in the form of nuclear emission, rings, and mini-spirals. The rest
of the sample show Pa-alpha emission along the disk and the spiral arms
extending over scales of 3-7kpc and larger. About half of the sample contains
HII regions with H-alpha luminosities significantly higher than those observed
in normal galaxies. There is a linear empirical relationship between the mid-IR
24um and hydrogen recombination (extinction-corrected Pa-alpha) luminosity for
these LIRGs, and the HII regions in the central part of M51. This relation
holds over more than four decades in luminosity suggesting that the mid-IR
emission is a good tracer of the star formation rate (SFR). Analogous to the
widely used relation between the SFR and total IR luminosity of Kennicutt
(1998), we derive an empirical calibration of the SFR in terms of the
monochromatic 24um luminosity that can be used for luminous, dusty galaxies.Comment: Accepted for publication in ApJ. Contact first author for high
qualitity version of figure
High-resolution imaging of the molecular outflows in two mergers: IRAS17208-0014 and NGC1614
Galaxy evolution scenarios predict that the feedback of star formation and
nuclear activity (AGN) can drive the transformation of gas-rich spiral mergers
into ULIRGs, and, eventually, lead to the build-up of QSO/elliptical hosts. We
study the role that star formation and AGN feedback have in launching and
maintaining the molecular outflows in two starburst-dominated advanced mergers,
NGC1614 and IRAS17208-0014, by analyzing the distribution and kinematics of
their molecular gas reservoirs. We have used the PdBI array to image with high
spatial resolution (0.5"-1.2") the CO(1-0) and CO(2-1) line emissions in
NGC1614 and IRAS17208-0014, respectively. The velocity fields of the gas are
analyzed and modeled to find the evidence of molecular outflows in these
sources and characterize the mass, momentum and energy of these components.
While most (>95%) of the CO emission stems from spatially-resolved
(~2-3kpc-diameter) rotating disks, we also detect in both mergers the emission
from high-velocity line wings that extend up to +-500-700km/s, well beyond the
estimated virial range associated with rotation and turbulence. The kinematic
major axis of the line wing emission is tilted by ~90deg in NGC1614 and by
~180deg in IRAS17208-0014 relative to their respective rotating disk major
axes. These results can be explained by the existence of non-coplanar molecular
outflows in both systems. In stark contrast with NGC1614, where star formation
alone can drive its molecular outflow, the mass, energy and momentum budget
requirements of the molecular outflow in IRAS17208-0014 can be best accounted
for by the existence of a so far undetected (hidden) AGN of L_AGN~7x10^11
L_sun. The geometry of the molecular outflow in IRAS17208-0014 suggests that
the outflow is launched by a non-coplanar disk that may be associated with a
buried AGN in the western nucleus.Comment: Final version in press, accepted by A&A. Reference list updated.
Minor typos correcte
Size and Structure of the Narrow-Line Region of Quasars
We have observed the narrow-line regions (NLRs) of the seven brightest
radio-quiet PG (or BQS) quasars (z < 0.5) with the Wide Field and Planetary
Camera 2 on board the Hubble Space Telescope (HST). Linear-ramp filters were
used to image the [OIII] lambda 5007 line emission with 0.0455-0.1 arcsec pixel
resolution. We find that the NLRs are very compact with typical extents of 2-4
arcsec. Two quasars show compact filamentary structures similar to Seyfert
NLRs. They may be related to radio outflows. Most interestingly, when including
a sample of Seyfert galaxies observed with HST, we tentatively find that the
size of the NLR is proportional to the square root of the [OIII] luminosity.
This is comparable to the scaling found for the size of the broad-line region
with continuum luminosity, which has been interpreted in terms of a constant
photoionization parameter. The relation determined here connects the NLR of
radio-quiet quasars and Seyferts over three orders of magnitude in [OIII]
luminosity.Comment: 6 pages, 4 figures, accepted for publication in ApJ Letter
Spatially Resolved Near-Infrared Spectroscopy of Seyfert 2 Galaxies Mk 1066, NGC 2110, NGC 4388, and Mk 3
We present near-infrared spectra with resolutions of lambda/dlambda~1200 in
the emission lines of Pa-beta, [FeII] (1.2567um), Br-gamma, and H2 v=1-0S(1) of
the nuclei and circumnuclear regions of the four Seyfert 2 galaxies Mk 1066,
NGC 2110, NGC 4388, and Mk 3. All of these galaxies show strong near-infrared
line emission that is detected at radii several times the spatial resolution,
corresponding to projected physical scales of 0.07 to 0.7 kpc. Velocity
gradients are detected in these nuclei, as are spatial variations in line
profiles and flux ratios. We compare the spatial and velocity distribution of
the line emission to previously observed optical line and radio emission. The
evidence indicates that the [FeII] emission is associated with the Seyfert
activity in the galaxies. Our data are consistent with X-ray heating being
responsible for most of the [FeII] emission, although differences in [FeII] and
Pa-beta line profiles associated with radio emission suggests that the [FeII]
emission is enhanced by fast shocks associated with radio outflows. The H2
emission is not as strongly associated with outflows or ionization cones as is
the emission in other lines, but rather appears to be primarily associated with
the disk of the galaxy.Comment: 35 pages, 24 figure
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