76 research outputs found
Spitzer/IRS Mapping of Local Luminous Infrared Galaxies
We present results of our program Spitzer/IRS Mapping of local Luminous
Infrared Galaxies (LIRGs). The maps cover the central 20"x20" or 30"x 30"
regions of the galaxies, and use all four IRS modules to cover the full 5-38
microns spectral range. We have built spectral maps of the main mid-IR emission
lines, continuum and PAH features, and extracted 1D spectra for regions of
interest in each galaxy. The final goal is to fully characterize the mid-IR
properties of local LIRGs as a first step to understanding their more distant
counterparts.Comment: 4 pages, 5 figures. To appear in "Highlights of Spanish Astrophysics
V", Proceedings of the VIII Scientific Meeting of the Spanish Astronomical
Society (SEA) held in Santander, 7-11 July, 200
Star formation and nuclear activity of local luminous infrared galaxies
Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de FÃsica Teórica. Fecha de lectura: 03-02-201
Warm molecular gas temperature distribution in six local infrared bright Seyfert galaxies
We simultaneously analyze the spectral line energy distributions (SLEDs) of
CO and H2 of six local luminous infrared (IR) Seyfert galaxies. For the CO
SLEDs, we used new Herschel/SPIRE FTS data (from J=4-3 to J=13-12) and
ground-based observations for the lower-J CO transitions. The H2 SLEDs were
constructed using archival mid-IR Spitzer/IRS and near-IR VLT/SINFONI data for
the rotational and ro-vibrational H2 transitions, respectively. In total, the
SLEDs contain 26 transitions with upper level energies between 5 and 15000 K. A
single, constant density, model (n ~ 10 cm) with a
broken power-law temperature distribution reproduces well both the CO and H2
SLEDs. The power-law indices are ~ 1-3 for warm molecular gas (20 K <
T 100 K). We show that
the steeper temperature distribution (higher ) for hot molecular gas can
be explained by shocks and photodissociation region (PDR) models, however, the
exact values are not reproduced by PDR or shock models alone and a
combination of both is needed. We find that the three major mergers among our
targets have shallower temperature distributions for warm molecular gas than
the other three spiral galaxies. This can be explained by a higher relative
contribution of shock excitation, with respect to PDR excitation, for the warm
molecular gas in these mergers. For only one of the mergers, IRASF 05189-2524,
the shallower H2 temperature distribution differs from that of the spiral
galaxies. The presence of a bright active galactic nucleus in this source might
explain the warmer molecular gas observed.Comment: A&A in press; 15 pages, 7 figures. Fixed several typo
An X-ray Study of Local Infrared Bright Galaxies
We are carrying out detailed study of the X-ray and infrared (IR) properties
of a sample of local (d < 70 Mpc) luminous infrared galaxies (LIRGs) using
XMM-Newton and Spitzer (imaging and spectroscopy). The main goal is to study
the extreme processes of star formation and/or active galactic nuclei (AGN)
taking place in this cosmologically important class of galaxies. In this
proceedings we present the preliminary results obtained from the analysis of
the XMM-Newton X-ray images and the X-ray spectral modeling.Comment: 5 pages, to appear in Highlights of Spanish Astrophysics VI,
Proceedings of the IX Scientific Meeting of the Spanish Astronomical Society
held on September 13-17, 2010, in Madrid, Spai
Local Luminous Infrared Galaxies. III. Co-evolution of Black Hole Growth and Star Formation Activity?
Local luminous infrared (IR) galaxies (LIRGs) have both high star formation
rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence.
Therefore, they are ideal candidates to explore the co-evolution of black hole
(BH) growth and star formation (SF) activity, not necessarily associated with
major mergers. Here, we use Spitzer/IRS spectroscopy of a complete
volume-limited sample of local LIRGs (distances of <78Mpc). We estimate typical
BH masses of 3x10^7 M_sun using [NeIII]15.56micron and optical [OIII]5007A gas
velocity dispersions and literature stellar velocity dispersions. We find that
in a large fraction of local LIRGs the current SFR is taking place not only in
the inner nuclear ~1.5kpc region, as estimated from the nuclear 11.3micron PAH
luminosities, but also in the host galaxy. We next use the ratios between the
SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH
growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to
BHAR ratios higher than those of optically selected Seyferts of similar AGN
luminosities. However, the majority of the IR-bright galaxies in the RSA
Seyfert sample behave like local LIRGs. Moreover, the AGN incidence tends to be
higher in local LIRGs with the lowest SFRs. All this suggests that in local
LIRGs there is a distinct IR-bright star forming phase taking place prior to
the bulk of the current BH growth (i.e., AGN phase). The latter is reflected
first as a composite and then as a Seyfert, and later as a non-LIRG optically
identified Seyfert nucleus with moderate SF in its host galaxy.Comment: Accepted for publication in Ap
VLT-SINFONI sub-kpc study of the star formation in local LIRGs and ULIRGs: Analysis of the global structure and characterisation of individual star-forming clumps
We present a 2D study of star formation at kpc and sub-kpc scales of a sample
of local (z<0.1) U/LIRGs, based on near-IR VLT-SINFONI observations. We
obtained integrated measurements of the star formation rate (SFR) and star
formation rate surface density, together with their 2D distributions, based on
Br_gamma and Pa_alpha emission. We observe a tight linear correlation between
the SFR derived from our extinction-corrected measurements and that derived
from 24 micron data, and a reasonable agreement with SFR derived from total IR
luminosity. Our near-IR measurements are on average a factor 3 larger than
optical SFR, even when extinction corrections are applied. We found that LIRGs
have a median-observed star formation rate surface density of 1.72
Msun/yr/kpc^2 for the extinction-corrected distribution, whilst ULIRGs have
0.23 Msun/yr/kpc^2, respectively. These median values for ULIRGs increase up to
2.90 Msun/yr/kpc^2, when only their inner regions, covering the same size as
the average FoV of LIRGs, are considered. We identified a total of 95
individual SF clumps in our sample, with sizes within 60-1500pc, and
extinction-corrected Pa_alpha luminosities of 10^5-10^8 Lsun. Star-forming
clumps in LIRGs are about ten times larger and thousands of times more luminous
than typical clumps in spiral galaxies. Clumps in ULIRGs have sizes similar
(x0.5-1) to those of high-z clumps, having Pa_alpha luminosities similar to
some high-z clumps, and about 10 times less luminous than the most luminous
high-z clumps identified so far. We also observed a change in the slope of the
L-r relation. A likely explanation is that most luminous galaxies are
interacting and merging, and therefore their size represents a combination of
the distribution of the star-forming clumps within each galaxy in the system
plus the effect of the projected distance.Comment: 27 pages, 27 figures, accepted for publication in A&A. Abstract
abridged due to arXiv requirement
Outflow of hot and cold molecular gas from the obscured secondary nucleus of NGC3256: closing in on feedback physics
The nuclei of merging galaxies are often deeply buried in dense layers of gas
and dust. In these regions, gas outflows driven by starburst and AGN activity
are believed to play a crucial role in the evolution of these galaxies.
However, to fully understand this process it is essential to resolve the
morphology and kinematics of such outflows. Using near-IR integral-field
spectroscopy obtained with VLT/SINFONI, we detect a kpc-scale structure of
high-velocity molecular hydrogen (H2) gas associated with the deeply buried
secondary nucleus of the IR-luminous merger NGC3256. We show that this
structure is likely the hot component of a molecular outflow, which is detected
also in the cold molecular gas by Sakamoto et al. This outflow, with a
molecular gas mass of M(H2)~2x10^7 Msun, is among the first to be spatially
resolved in both the hot H2 gas with VLT/SINFONI and the cold CO-emitting gas
with ALMA. The hot and cold components share a similar morphology and
kinematics, with a hot-to-cold molecular gas mass ratio of ~6x10^-5. The high
(~100 pc) resolution at which we map the geometry and velocity structure of the
hot outflow reveals a biconical morphology with opening angle ~40 deg and gas
spread across a FWZI~1200 km/s. Because this collimated outflow is oriented
close to the plane of the sky, the molecular gas may reach maximum intrinsic
outflow velocities of ~1800 km/s, with an average mass outflow rate of at least
~20 Msun/yr. By modeling the line-ratios of various near-IR H2 transitions, we
show that the H2 gas in the outflow is heated through shocks or X-rays to a
temperature of ~1900K. The energy needed to drive the outflow is likely
provided by a hidden Compton-thick AGN or by the nuclear starburst. We show
that the global kinematics of the molecular outflow in NGC3256 mimic those of
CO-outflows that have been observed at low spatial resolution in starburst- and
active galaxies.Comment: Accepted in Astronomy and Astrophysics (accepted 29 Aug 2014 v.3,
initial submission v.1 14 March 2014), 13 pages, 8 figure
Star-formation histories of local luminous infrared galaxies
We present the analysis of the integrated spectral energy distribution (SED)
from the ultraviolet (UV) to the far-infrared and H of a sample of 29
local systems and individual galaxies with infrared (IR) luminosities between
10^11 Lsun and 10^11.8 Lsun. We have combined new narrow-band H+[NII]
and broad-band g, r optical imaging taken with the Nordic Optical Telescope
(NOT), with archival GALEX, 2MASS, Spitzer, and Herschel data. The SEDs
(photometry and integrated H flux) have been fitted with a modified
version of the MAGPHYS code using stellar population synthesis models for the
UV-near-IR range and thermal emission models for the IR emission taking into
account the energy balance between the absorbed and re-emitted radiation. From
the SED fits we derive the star-formation histories (SFH) of these galaxies.
For nearly half of them the star-formation rate appears to be approximately
constant during the last few Gyrs. In the other half, the current
star-formation rate seems to be enhanced by a factor of 3-20 with respect to
that occured ~1 Gyr ago. Objects with constant SFH tend to be more massive than
starbursts and they are compatible with the expected properties of a
main-sequence (M-S) galaxy. Likewise, the derived SFHs show that all our
objects were M-S galaxies ~1 Gyr ago with stellar masses between 10^10.1 and
10^11.5 Msun. We also derived from our fits the average extinction (A_v=0.6-3
mag) and the polycyclic aromatic hydrocarbons (PAH) luminosity to L(IR) ratio
(0.03-0.16). We combined the A_v with the total IR and H luminosities
into a diagram which can be used to identify objects with rapidly changing
(increasing or decreasing) SFR during the last 100 Myr.Comment: 16 pages + online material, accepted for publication in A&
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