79 research outputs found
A Near-Infrared Study of the Stellar Cluster: [DBS2003] 45
We present a multi-wavelength photometric and spectroscopic study of a newly
discovered candidate cluster [DBS2003] 45. Our H, Ks photometry confirms that
[DBS2003] 45 is a cluster. An average visual extinction Av 7.1+/-0.5 is needed
to fit the cluster sequence with a model isochrone. Low resolution spectroscopy
indicates that half a dozen early B and at least one late O type giant stars
are present in the cluster. We estimate the age of the cluster to be between 5
and 8 Myr based on spectroscopic analysis. Assuming an age of 6 Myr, we fit the
observed mass function with a power law, N(M) M^(-Gamma), and find an index
Gamma 1.27+/-0.15, which is consistent with the Salpeter value. We estimate the
total cluster mass is around 1000 solar masses by integrating the derived mass
function between 0.5 and 45 solar masses. Both mid-infrared and radio
wavelength observations show that a bubble filled with ionized gas is
associated with the cluster. The total ionizing photon flux estimated from
radio continuum measurements is consistent with the number of hot stars we
detected. Infrared bright point sources along the rim of the bubble suggest
that there is triggered star formation at the periphery of the HII region.Comment: 12 pages, 10 figures, 2 tables. Accepted by ApJ, a typo in the
Abstract correcte
Detailed analysis of paternal knockout <i>Grb10 </i>mice suggests effects on stability of social behavior, rather than social dominance
Imprinted genes are highly expressed in monoaminergic regions of the midbrain and their functions in this area are thought to have an impact on mammalian social behaviors. One such imprinted gene is Grb10, of which the paternal allele is generally recognized as mediating social dominance behavior. However, there has been no detailed study of social dominance in Grb10 +/p mice. Moreover, the original study examined tubeâtest behavior in isolated mice 10 months of age. Isolation testing favors more territorial and aggressive behaviors, and does not address social dominance strategies employed in group housing contexts. Furthermore, isolation stress impacts midbrain function and dominance related behavior, often through alterations in monoaminergic signaling. Thus, we undertook a systematic study of Grb10 +/p social rank and dominance behavior within the cage group, using a number of convergent behavioral tests. We examined both male and female mice to account for sex differences and tested cohorts aged 2, 6 and 10 months to examine any developments related to age. We found groupâhoused Grb10 +/p mice do not show evidence of enhanced social dominance, but cages containing Grb10 +/p and wildâtype mice lacked the normal correlation between three different measures of social rank. Moreover, a separate study indicated isolation stress induced inconsistent changes in tube test behavior. Taken together, these data suggest future research on Grb10 +/p mice should focus on the stability of social behaviors, rather than dominance per se
On the central ionizing star of G23.96+0.15 and near-IR spectral classification of O stars
Aims: A near-infrared study of the main ionizing star of the ultracompact HII
region G23.96+0.15 (IRAS 18317-0757) is presented, along with a re-evaluation
of the distance to this source, and a re-assessment of H- and K-band
classification diagnostics for O dwarfs; Methods: We have obtained near-IR
VLT/ISAAC imaging and spectroscopy of G23.96+0.15, plus archival imaging from
UKIRT/UFTI. A spectroscopic analysis was carried out using a non-LTE model
atmosphere code; Results: A quantitative H- and K-band classification scheme
for O dwarfs is provided, from which we establish an O7.5V spectral subtype for
the central star of G23.96+0.15. We estimate an effective temperature of Teff ~
38 kK from a spectral analysis; Conclusions: A spectroscopic distance of 2.5
kpc is obtained for G23.96+0.15, substantially lower than the kinematic
distance of 4.7 kpc, in common with recent studies of other Milky way HII
regions. Such discrepancies would be alleviated if sources are unresolved
binaries or clusters.Comment: 5 pages, 3 figures, accepted for Astronomy & Astrophysic
Subaru and Gemini High Spatial Resolution Infrared 18 Micron Imaging Observations of Nearby Luminous Infrared Galaxies
We present the results of a ground-based, high spatial resolution infrared 18
micron imaging study of nearby luminous infrared galaxies (LIRGs), using the
Subaru 8.2-m and Gemini South 8.1-m telescopes. The diffraction-limited images
routinely achieved with these telescopes in the Q-band (17-23 micron) allow us
to investigate the detailed spatial distribution of infrared emission in these
LIRGs. We then investigate whether the emission surface brightnesses are
modest, as observed in starbursts, or are so high that luminous active galactic
nuclei (AGNs; high emission surface brightness energy sources) are indicated.
The sample consists of 18 luminous buried AGN candidates and
starburst-classified LIRGs identified in earlier infrared spectroscopy. We find
that the infrared 18 micron emission from the buried AGN candidates is
generally compact, and the estimated emission surface brightnesses are high,
sometimes exceeding the maximum value observed in and theoretically predicted
for a starburst phenomenon. The starburst-classified LIRGs usually display
spatially extended 18 micron emission and the estimated emission surface
brightnesses are modest, within the range sustained by a starburst phenomenon.
The general agreement between infrared spectroscopic and imaging energy
diagnostic methods suggests that both are useful tools for understanding the
hidden energy sources of the dusty LIRG population.Comment: 17 pages, 3 figures, accepted for publication in AJ (No. 141, 2011
May issue). Higher resolution version is available at
http://optik2.mtk.nao.ac.jp/~imanishi/Paper/20um/20um.pd
Follow-Up Near-infrared Spectroscopy of Ultraluminous Infrared Galaxies observed by ISO
We present low resolution near-infrared spectroscopy of an unbiased sample of
24 ultraluminous infrared galaxies (ULIRGs), selected from samples previously
observed spectroscopically in the mid-infrared with the Infrared Space
Observatory (ISO). Qualitatively, the near-infrared spectra resemble those of
starbursts. Only in one ULIRG, IRAS 04114-5117E, do we find spectroscopic
evidence for AGN activity. The spectroscopic classification in the
near-infrared is in very good agreement with the mid-infrared one. For a subset
of our sample for which extinction corrections can be derived from Pa-alpha and
Br-gamma, we find rather high Pa-alpha luminosities, in accordance with the
powering source of these galaxies being star formation.[Fe] emission is strong
in ULIRGs and may be linked to starburst and superwind activity. Additionally,
our sample includes two unusual objects. The first, IRAS F00183-7111, exhibits
extreme [Fe] emission and the second, IRAS F23578-5307, is according to our
knowledge one of the most luminous infrared galaxies in H2 rotation-vibration
emission.Comment: Accepted for publication in A&A (12 pages, 4 figures). See
http://www.mpia-hd.mpg.de/homes/dannerb/ for a version with higher quality
figure
Results from a Near Infrared Search for Emission-line Stars in the Inner Galaxy: Spectra of New Wolf-Rayet Stars
We present follow-up spectroscopy of emission line candidates detected on
near-infrared narrow band images in the inner Galaxy (Homeier et al. 2003). The
filters are optimized for the detection of Wolf-Rayet stars and other objects
which exhibit emission--lines in the 2 m region. Approximately three
square degrees along the Galactic plane have been analyzed in seven
narrow--filters (four emission--lines and three continuum). We have discovered
4 new Wolf-Rayet stars and present coordinates, finding charts, and K-band
spectra.Comment: To appear in Astronomy & Astrophysic
The properties of quasar hosts at the peak of the quasar activity
We present near-infrared imaging obtained with ESO VLT/ISAAC of a sample of
16 low luminosity radio-quiet quasars at the epoch around the peak of the
quasar activity (2 < z < 3), aimed at investigating their host galaxies. For 11
quasars, we are able to detect the host galaxies and derive their properties,
while for the other five quasars, upper limits to the host luminosity are
estimated. The luminosities of the host galaxies of radio-quiet quasars at high
redshift are in the range of those of massive inactive elliptical galaxies.
This work complements our previous systematic study of quasar hosts aimed to
trace the cosmological luminosity evolution of the host galaxies up to z ~2 and
extends our pilot study of a few luminous quasars at z > 2. The luminosity
trend with cosmic epoch resembles that observed for massive inactive galaxies,
suggesting a similar star formation history. In particular, both quasar host
galaxies and massive inactive galaxies appear mostly assembled already at the
peak age of the quasar activity. This result is of key importance for testing
the models of joint formation and evolution of galaxies and their active
nuclei.Comment: 27 pages, 8 figures, 2 tables. Accepted for publication in Ap
GLIMPSE-CO1: the most massive intermediate-age stellar cluster in the Galaxy
The stellar cluster GLIMPSE-C01 is a dense stellar system located in the
Galactic Plane. Though often referred to in the literature as an old globular
cluster traversing the Galactic disk, previous observations do not rule out
that it is an intermediate age (less than a few Gyr) disk-borne cluster. Here,
we present high-resolution near-infrared spectroscopy of over 50 stars in the
cluster. We find an average radial velocity is consistent with being part of
the disk, and determine the cluster's dynamical mass to be (8 \pm 3)x10^4 Msun.
Analysis of the cluster's M/L ratio, the location of the Red Clump, and an
extremely high stellar density, all suggest an age of 400-800Myr for
GLIMPSE-C01, much lower than for a typical globular cluster. This evidence
therefore leads us to conclude that GLIMPSE-C01 is part of the disk population,
and is the most massive Galactic intermediate-age cluster discovered to date.Comment: 10 pages, 9 figures, accepted for publication in MNRA
AKARI Near-Infrared Spectroscopy of Luminous Infrared Galaxies
We present the AKARI near-infrared (NIR; 2.5-5 micron) spectroscopic study of
36 (ultra)luminous infrared galaxies [(U)LIRGs] at z=0.01-0.4. We measure the
NIR spectral features including the strengths of 3.3 micron polycyclic aromatic
hydrocarbon (PAH) emission and hydrogen recombination lines (Br\alpha. and
Br\beta), optical depths at 3.1 and 3.4 micron, and NIR continuum slope. These
spectral features are used to identify optically elusive, buried AGN. We find
that half of the (U)LIRGs optically classified as non-Seyferts show AGN
signatures in their NIR spectra. Using a combined sample of (U)LIRGs with NIR
spectra in the literature, we measure the contribution of buried AGN to the
infrared luminosity from the SED-fitting to the IRAS photometry. The
contribution of these buried AGN to the infrared luminosity is 5-10%, smaller
than the typical AGN contribution of (U)LIRGs including Seyfert galaxies
(10-40%). We show that NIR continuum slopes correlate well with WISE
[3.4]-[4.6] colors, which would be useful for identifying a large number of
buried AGN using the WISE data.Comment: ApJ, accepted. 37 pages, 11 figure
A near-IR study of the host galaxies of 2Jy radio sources at 0.03 < z < 0.5: I - the data
We present the results of a program of K- and Ks-band imaging of a sample of
2Jy radio galaxies with redshifts 0.03 < z < 0.5, for which the host galaxy
morphologies and structural parameters (effective radius, Sersic index and
unresolved nuclear point source contribution) have been determined using
GALFIT. Two-thirds of our sample are best modelled as being hosted by massive
elliptical galaxies with Sersic indices of n=4-6, with the remainder being
better suited either by a mixture of morphological components (usually a bulge
plus a small, less luminous, disk component) or by more disky galaxy models
with n=1-2. Our measured galaxy sizes are generally in very good agreement with
other imaging programs, both space- and ground-based. We also determine a
slightly higher average nuclear point source contribution than similar
HST-based programs. This is due to our inability to separate the AGN emission
from compact circum-nuclear stellar emission, but does not bias our modelling
of the remainder of the host galaxies and our results remain robust. We also
observe that roughly half of the objects in our sample are either undergoing
major or minor merger activity or are clearly morphologically disturbed.Comment: Accepted for publication in MNRAS. 31 pages, 9 figures, 6 tables.
Landscape table 4 added as extra included figur
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