156 research outputs found
Genetic and molecular genetic characterization of the Japanese early heading cultivar of wheat
Understanding the 8 micron vs. Pa-alpha relationship on sub-arcsecond scales in Luminous Infrared Galaxies
This work explores in detail the relation between the 8 micron and the
Pa-alpha emissions for 122 HII regions identified in a sample of 10 low-z LIRGs
with nearly constant metallicity (12 + log (O/H) ~ 8.8). We use Gemini/T-ReCS
high-spatial resolution (<~ 0.4" ~ 120 pc for the average distance of 60 Mpc of
our sample) mid-infrared imaging (at 8.7 micron or 10.3 micron) together with
HST/NICMOS continuum and Pa-alpha images. The LIRG HII regions extend the
L_8micron vs. L_Pa-alpha relation found for HII knots in the high-metallicity
SINGS galaxies by about two orders of magnitude to higher luminosities. Since
the metallicity of the LIRG sample is nearly constant, we can rule out this
effect as a cause for the scatter seen in the relationship. In turn, it is
attributed to two effects: age and PAH features. The L_8micron/L_Pa-alpha
ratio, which varies by a factor of ten for the LIRG HII regions, is reproduced
by a model with instantaneous star formation and ages ranging from ~ 4 to 7.5
Myr. The remaining dispersion around the model predictions for a given age is
probably due to differential contributions of the PAH features (the 8.6 micron,
in our case) to the 8 micron emission from galaxy to galaxy.Comment: 16 pages, 9 figures, accepted for publication in ApJ; paper with
full-resolution figures can be found at:
http://damir.iem.csic.es/extragalactic
The FUV to Near-IR Morphologies of Luminous Infrared Galaxies in the GOALS Sample
We compare the morphologies of a sample of 20 LIRGs from the Great
Observatories All-sky LIRG Survey (GOALS) in the FUV, B, I and H bands, using
the Gini (G) and M20 parameters to quantitatively estimate the distribution and
concentration of flux as a function of wavelength. HST images provide an
average spatial resolution of ~80 pc. While our LIRGs can be reliably
classified as mergers across the entire range of wavelengths studied here,
there is a clear shift toward more negative M20 (more bulge-dominated) and a
less significant decrease in G values at longer wavelengths. We find no
correlation between the derived FUV G-M20 parameters and the global measures of
the IR to FUV flux ratio, IRX. Given the fine resolution in our HST data, this
suggests either that the UV morphology and IRX are correlated on very small
scales, or that the regions emitting the bulk of the IR emission emit almost no
FUV light. We use our multi-wavelength data to simulate how merging LIRGs would
appear from z~0.5-3 in deep optical and near-infrared images such as the HUDF,
and use these simulations to measure the G-M20 at these redshifts. Our
simulations indicate a noticeable decrease in G, which flattens at z >= 2 by as
much as 40%, resulting in mis-classifying our LIRGs as disk-like, even in the
rest-frame FUV. The higher redshift values of M20 for the GOALS sources do not
appear to change more than about 10% from the values at z~0. The change in
G-M20 is caused by the surface brightness dimming of extended tidal features
and asymmetries, and also the decreased spatial resolution which reduced the
number of individual clumps identified. This effect, seen as early as z~0.5,
could easily lead to an underestimate of the number of merging galaxies at
high-redshift in the rest-frame FUV.Comment: Accepted for publication in the Astronomical Journal. The total page
count is 15 pages with 13 figures and 1 Tabl
Understanding the 8 micron vs. Pa-alpha relationship on sub-arcsecond scales in Luminous Infrared Galaxies
This work explores in detail the relation between the 8 micron and the
Pa-alpha emissions for 122 HII regions identified in a sample of 10 low-z LIRGs
with nearly constant metallicity (12 + log (O/H) ~ 8.8). We use Gemini/T-ReCS
high-spatial resolution (<~ 0.4" ~ 120 pc for the average distance of 60 Mpc of
our sample) mid-infrared imaging (at 8.7 micron or 10.3 micron) together with
HST/NICMOS continuum and Pa-alpha images. The LIRG HII regions extend the
L_8micron vs. L_Pa-alpha relation found for HII knots in the high-metallicity
SINGS galaxies by about two orders of magnitude to higher luminosities. Since
the metallicity of the LIRG sample is nearly constant, we can rule out this
effect as a cause for the scatter seen in the relationship. In turn, it is
attributed to two effects: age and PAH features. The L_8micron/L_Pa-alpha
ratio, which varies by a factor of ten for the LIRG HII regions, is reproduced
by a model with instantaneous star formation and ages ranging from ~ 4 to 7.5
Myr. The remaining dispersion around the model predictions for a given age is
probably due to differential contributions of the PAH features (the 8.6 micron,
in our case) to the 8 micron emission from galaxy to galaxy.Comment: 16 pages, 9 figures, accepted for publication in ApJ; paper with
full-resolution figures can be found at:
http://damir.iem.csic.es/extragalactic
On the Refractive Index of Ageing Dispersions of Laponite
Aqueous dispersion of Laponite at low ionic concentration is of interest
since it undergoes structural evolution with respect to time, which is usually
termed as ageing. In this work we study the refractive index behavior as a
function of ageing time, concentration and temperature. We observed that the
extended Lorenz-Lorentz equation fitted the refractive index dependence on
concentration and temperature very well. The refractive index did not show any
dependence on ageing time. However, the dependence of refractive index on
concentration showed a marked change as the system underwent transition from an
isotropic to a biphasic state. The slope of the refractive index-density data
is remarkably close to that of water at all Laponite concentrations. In the
context of transport phenomena, optical measurements such as interferometry can
exploit the water-like behavior of Laponite dispersions.Comment: 13 pages, 3 figures, to appear in Applied Clay Scienc
Eddington-Limited Accretion in z~2 WISE-selected Hot, Dust-Obscured Galaxies
Hot, Dust-Obscured Galaxies, or "Hot DOGs", are a rare, dusty, hyperluminous
galaxy population discovered by the WISE mission. Predominantly at redshifts
2-3, they include the most luminous known galaxies in the universe. Their high
luminosities likely come from accretion onto highly obscured super massive
black holes (SMBHs). We have conducted a pilot survey to measure the SMBH
masses of five z~2 Hot DOGs via broad H_alpha emission lines, using
Keck/MOSFIRE and Gemini/FLAMINGOS-2. We detect broad H_alpha emission in all
five Hot DOGs. We find substantial corresponding SMBH masses for these Hot DOGs
(~ 10^{9} M_sun), and their derived Eddington ratios are close to unity. These
z~2 Hot DOGs are the most luminous AGNs at given BH masses, suggesting they are
accreting at the maximum rates for their BHs. A similar property is found for
known z~6 quasars. Our results are consistent with scenarios in which Hot DOGs
represent a transitional, high-accretion phase between obscured and unobscured
quasars. Hot DOGs may mark a special evolutionary stage before the red quasar
and optical quasar phases, and they may be present at other cosmic epochs.Comment: 15 pages, 9 figures. Accepted by Ap
High spatial resolution T-ReCS mid-infrared imaging of Luminous Infrared Galaxies
We present diffraction-limited (FWHM ~ 0.3arcsec) Gemini/T-ReCS mid-infrared
(MIR: N-band or narrow-band at 8.7micron) imaging of four Luminous Infrared
Galaxies (LIRGs) drawn from a representative local sample. The MIR emission in
the central few kpc is strikingly similar to that traced by Pa-alpha, and
generally consists of bright nuclear emission and several compact circumnuclear
and/or extranuclear HII regions. The central MIR emission is dominated by these
powerful HII regions, consistent with the majority of AGN in this local sample
of LIRGs contributing a minor part of the MIR emission. The luminous
circumnuclear HII regions detected in LIRGs follow the extrapolation of the
8micron vs. Pa-alpha relation found for M51 HII knots. The integrated central
3-7kpc of galaxies, however, present elevated 8micron/Pa-alpha ratios with
respect to individual HII regions, similar to the integrated values for
star-forming galaxies. Our results show that the diffuse 8micron emission, not
directly related to the ionizing stellar population, can be as luminous as that
from the resolved HII regions. Therefore, calibrations of the star formation
rate for distant galaxies should be based on the integrated 8micron emission of
nearby galaxies, not that of the HII regions alone.Comment: Accepted for publication in Astrophysical Journal Letters. Paper with
high resolution Fig.1 can be found at
http://damir.iem.csic.es/extragalactic/publications/publications.htm
Warm H as a probe of massive accretion and feedback through shocks and turbulence across cosmic time
Galaxy formation depends on a complex interplay between gravitational
collapse, gas accretion, merging, and feedback processes. Yet, after many
decades of investigation, these concepts are poorly understood. This paper
presents the argument that warm H can be used as a tool to unlock some of
these mysteries. Turbulence, shocks and outflows, driven by star formation, AGN
activity or inflows, may prevent the rapid buildup of star formation in
galaxies. Central to our understanding of how gas is converted into stars is
the process by which gas can dissipate its mechanical energy through turbulence
and shocks in order to cool. H lines provide direct quantitative
measurements of kinetic energy dissipation in molecular gas in galaxies
throughout the Universe. Based on the detection of very powerful H lines
from z = 2 galaxies and proto-clusters at the detection limits of {\it
Spitzer}, we are confident that future far-IR and UV H observations will
provide a wealth of new information and insight into galaxy evolution to
high-z. Finally, at the very earliest epoch of star and galaxy formation, warm
H may also provide a unique glimpse of molecular gas collapse at 7 z
12 in massive dark matter (DM) halos on their way to forming the very first
galaxies. Such measurements are beyond the reach of existing and planned
observatories.Comment: Submitted as a science White Paper to the Astronomy and Astrophysics
Astro 2020 Decadal Survey call issued by the National Academies of Sciences,
Engineering and Medicine (March 11 2019
An Overdensity of Lyman Break Galaxies Around the Hot Dust-Obscured Galaxy WISE J224607.56052634.9
We report the identification of Lyman Break Galaxy (LBG) candidates around
the most luminous Hot Dust-Obscured Galaxy (Hot DOG) known, WISE
J224607.56052634.9 (W22460526) at , using deep \textit{r}-,
\textit{i}-, and \textit{z}-band imaging from the Gemini Multi-Object
Spectrograph South (GMOS-S). We use the surface density of LBGs to probe the
Mpc-scale environment of W22460526 to characterize its richness and
evolutionary state. We identify LBG candidates in the vicinity of W22460526
using the selection criteria developed by \cite{2004VOuchi} and
\cite{2006Yoshida} in the Subaru Deep Field and in the Subaru XMM-Newton Deep
Field, slightly modified to account for the difference between the filters
used, and we find 37 and 55 LBG candidates, respectively. Matching to the
-band depths of those studies, this corresponds to times the surface density of LBGs expected in the field.
Interestingly, the Hot DOG itself, as well as a confirmed neighbor, do not
satisfy either LBG selection criteria, suggesting we may be missing a large
number of companion galaxies. Our analysis shows that we are most likely only
finding those with higher-than-average IGM optical depth or moderately high
dust obscuration. The number density of LBG candidates is not concentrated
around W22460526, suggesting either an early evolutionary stage for the
proto-cluster or that the Hot DOG may not be the most massive galaxy, or that
the Hot DOG may be affecting the IGM transparency in its vicinity. The
overdensity around W22460526 is comparable to overdensities found around
other Hot DOGs and is somewhat higher than typically found for radio galaxies
and luminous quasars at a similar redshift.Comment: 20 pages, 15 figures. The main results are in Figures 9 and 12.
Accepted for publication in A&
Discovery of a Low-Redshift Hot Dust-Obscured Galaxy
We report the discovery of the hyperluminous, highly obscured AGN WISE
J190445.04+485308.9 (W1904+4853 hereafter, $L_{bol} = 1.1 \times 10^{13} \
L_{\odot}log \
(M_{BH}/M_{\odot}) = 8.4 \pm 0.31.4
\pm 0.2\sim 45 \ M_{\odot} \ yr^{-1}3 \times 10^{10} \ M_{\odot}$, the host galaxy
appears to be a starburst system with respect to the main sequence of the
star-forming galaxies at the same redshift. Although blueshifted and asymmetric
[O III] emission provides evidence of an outflow, we estimate it to be an order
of magnitude smaller than the star formation rate, indicating that the current
obscured AGN activity at the center has not yet produced significant feedback
on the host galaxy star formation activity. W1904+4853 supports the
interpretation that Hot DOGs are a rare transitional phase of AGN accretion in
galaxy evolution, a phase that can persist into the present-day Universe.Comment: 19 pages, 6 figures, submitted to Ap
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