87 research outputs found
The Spatial Extent of (U)LIRGs in the Mid-Infrared. II. Feature Emission
We present results from the second part of our analysis of the extended
mid-infrared (MIR) emission of the Great Observatories All-Sky LIRG Survey
(GOALS) sample based on 5-14 micron low-resolution spectra obtained with the
IRS on Spitzer. We calculate the fraction of extended emission as a function of
wavelength for all galaxies in the sample, FEE_lambda, and spatially separate
the MIR spectrum of galaxies into their nuclear and extended components.
We find that the [NeII] emission line is as compact as the hot dust MIR
continuum, while the polycyclic aromatic hydrocarbon (PAH) emission is more
extended. The 6.2 and 7.7 micron PAH emission is more compact than that of the
11.3 micron PAH, which is consistent with the formers being enhanced in a more
ionized medium. The presence of an AGN or a powerful nuclear starburst
increases the compactness of the hot dust MIR continuum, but has a negligible
effect on the spatial extent of the PAH emission on kpc-scales. Globally, the
spectra of the extended emission component are homogeneous for all galaxies in
GOALS. This suggests that the physical properties of star formation taking
place at distances farther than 1.5 kpc from the nuclei of (U)LIRGs are very
similar, resembling local star-forming galaxies with L_IR < 10^11 Lsun, as well
as star formation-dominated ULIRGs at z~2. In contrast, the MIR spectra of the
nuclear component of local (U)LIRGs are very diverse. This implies that the
observed variety of their integrated MIR properties arise, on average, only
from the processes that are taking place in their cores.Comment: 16 pages, 7 figures, accepted for publication in Ap
A High Spatial Resolution Mid-Infrared Spectroscopic Study of the Nuclei and Star-Forming Regions in Luminous Infrared Galaxies
We present a high spatial (diffraction-limited) resolution (~0.3")
mid-infrared (MIR) spectroscopic study of the nuclei and star-forming regions
of 4 local luminous infrared galaxies (LIRGs) using T-ReCS on the Gemini South
telescope. We investigate the spatial variations of the features seen in the
N-band spectra of LIRGs on scales of ~100 pc, which allow us to separate the
AGN emission from that of the star formation (SF). We compare our Gemini T-ReCS
nuclear and integrated spectra of LIRGs with those obtained with Spitzer IRS.
The 9.7um silicate absorption feature is weaker in the nuclei of the LIRGs than
in the surrounding regions. This is probably due to the either clumpy or
compact environment of the central AGN or young, nuclear starburst. We find
that the [NeII] luminosity surface density is tightly and directly correlated
with that of Pa-alpha for the LIRG star-forming regions (slope of 1.00+-0.02).
Although the 11.3um PAH feature shows also a trend with Pa-alpha, this is not
common for all the regions. We also find that the [NeII]\Pa-alpha ratio does
not depend on the Pa-alpha equivalent width (EW), i.e., on the age of the
ionizing stellar populations, suggesting that, on the scales probed here, the
[NeII] emission line is a good tracer of the SF activity in LIRGs. On the other
hand, the 11.3um PAH\Pa-alpha ratio increases for smaller values of the
Pa-alpha EW (increasing ages), indicating that the 11.3um PAH feature can also
be excited by older stars than those responsible for the Pa-alpha emission.
Additional high spatial resolution observations are essential to investigate,
in a statistical way, the star formation in local LIRGs at the smallest scales
and to probe ultimately whether they share the same physical properties as
high-z LIRGs, ULIRGs and submillimiter galaxies.Comment: 23 pages (apjstyle), 19 figures, accepted for publicacion in Ap
SOFIA/FORCAST resolves 30–40 μm extended dust emission in nearby active galactic nuclei
We present arcsecond-scale observations of the active galactic nuclei (AGNs)
of seven nearby Seyfert galaxies observed from the Stratospheric Observatory
For Infrared Astronomy (SOFIA) using the 31.5 and 37.1 um filters of the Faint
Object infraRed CAmera for the SOFIA Telescope (FORCAST). We isolate unresolved
emission from the torus and find extended diffuse emission in six 37.1 um
residual images in our sample. Using Spitzer/IRS spectra, we determine the
dominant mid-infrared (MIR) extended emission source and attribute it to dust
in the narrow line region (NLR) or star formation. We compare the optical NLR
and radio jet axes to the extended 37.1 um emission and find coincident axes
for three sources. For those AGNs with extended emission coincident with the
optical axis, we find that spatial scales of the residual images are consistent
with 0.1 - 1 kpc scale distances to which dust can be heated by the AGN. Using
previously published subarcsecond 1 - 20 um imaging and spectroscopic data
along with our new observations, we construct broadband spectral energy
distributions (SEDs) of the AGNs at wavelengths 1 - 40 um. We find that three
AGNs in our sample tentatively show a turnover in the SED between 30 - 40 um.
Using results from Clumpy torus models and the Bayesian inference tool
BayesClumpy, we find that the posterior outputs for AGNs with MIR turnover
revealed by SOFIA/FORCAST have smaller uncertainties than AGNs that do not show
a turnover.Comment: 16 pages, 9 figure
Characterizing the Cool KOIs III. KOI-961: A Small Star with Large Proper Motion and Three Small Planets
We present the characterization of the star KOI 961, an M dwarf with transit
signals indicative of three short-period exoplanets, originally discovered by
the Kepler Mission. We proceed by comparing KOI 961 to Barnard's Star, a
nearby, well-characterized mid-M dwarf. By comparing colors, optical and
near-infrared spectra, we find remarkable agreement between the two, implying
similar effective temperatures and metallicities. Both are metal-poor compared
to the Solar neighborhood, have low projected rotational velocity, high
absolute radial velocity, large proper motion and no quiescent H-alpha
emission--all of which is consistent with being old M dwarfs. We combine
empirical measurements of Barnard's Star and expectations from evolutionary
isochrones to estimate KOI 961's mass (0.13 +/- 0.05 Msun), radius (0.17 +/-
0.04 Rsun) and luminosity (2.40 x 10^(-3.0 +/- 0.3) Lsun). We calculate KOI
961's distance (38.7 +/- 6.3 pc) and space motions, which, like Barnard's Star,
are consistent with a high scale-height population in the Milky Way. We perform
an independent multi-transit fit to the public Kepler light curve and
significantly revise the transit parameters for the three planets. We calculate
the false-positive probability for each planet-candidate, and find a less than
1% chance that any one of the transiting signals is due to a background or
hierarchical eclipsing binary, validating the planetary nature of the transits.
The best-fitting radii for all three planets are less than 1 Rearth, with KOI
961.03 being Mars-sized (Rp = 0.57 +/- 0.18 Rearth), and they represent some of
the smallest exoplanets detected to date.Comment: Accepted to Ap
Local Luminous Infrared Galaxies: Spatially resolved mid-infrared observations with Spitzer/IRS
Luminous Infrared (IR) Galaxies (LIRGs) are an important cosmological class
of galaxies as they are the main contributors to the co-moving star formation
rate density of the universe at z=1. In this paper we present a GTO Spitzer IRS
program aimed to obtain spectral mapping of a sample of 14 local (d<76Mpc)
LIRGs. The data cubes map, at least, the central 20arcsec x 20arcsec to
30arcsec x 30arcsec regions of the galaxies, and use all four IRS modules
covering the full 5-38micron spectral range. The final goal of this project is
to characterize fully the mid-IR properties of local LIRGs as a first step to
understanding their more distant counterparts. In this paper we present the
first results of this GTO program. The IRS spectral mapping data allow us to
build spectral maps of the bright mid-IR emission lines (e.g., [NeII], [NeIII],
[SIII], H_2), continuum, the 6.2 and 11.3micron PAH features, and the 9.7micron
silicate feature, as well as to extract 1D spectra for regions of interest in
each galaxy. The IRS data are used to obtain spatially resolved measurements of
the extinction using the 9.7micron silicate feature, and to trace star forming
regions using the neon lines and the PAH features. We also investigate a number
of AGN indicators, including the presence of high excitation emission lines and
a strong dust continuum emission at around 6micron. We finally use the
integrated Spitzer/IRS spectra as templates of local LIRGs. We discuss several
possible uses for these templates, including the calibration of the star
formation rate of IR-bright galaxies at high redshift. We also predict the
intensities of the brightest mid-IR emission lines for LIRGs as a function of
redshift, and compare them with the expected sensitivities of future space IR
missions.Comment: Accepted for publication in Advances in Space Researc
A mobile ELF4 delivers circadian temperature information from shoots to roots
Extended Data and Source Data can be found at https://doi.org/10.1038/s41477-020-0634-2Ajuts: the Mas laboratory is funded by the FEDER/Spanish Ministry of Economy and Competitiveness, the Ramon Areces Foundation and the Generalitat de Catalunya (AGAUR). The P.M. laboratory also acknowledges financial support from the CERCA Program, Generalitat de Catalunya and by the Spanish Ministry of Economy and Competitiveness through the Severo Ochoa Program for Centers of Excellence in R&D 2016-2019 (SEV-2015-0533).The circadian clock is synchronized by environmental cues, mostly by light and temperature. Explaining how the plant circadian clock responds to temperature oscillations is crucial to understanding plant responsiveness to the environment. Here, we found a prevalent temperature-dependent function of the Arabidopsis clock component EARLY FLOWERING 4 (ELF4) in the root clock. Although the clocks in roots are able to run in the absence of shoots, micrografting assays and mathematical analyses show that ELF4 moves from shoots to regulate rhythms in roots. ELF4 movement does not convey photoperiodic information, but trafficking is essential for controlling the period of the root clock in a temperature-dependent manner. Low temperatures favour ELF4 mobility, resulting in a slow-paced root clock, whereas high temperatures decrease movement, leading to a faster clock. Hence, the mobile ELF4 delivers temperature information and establishes a shoot-to-root dialogue that sets the pace of the clock in root
Warm H₂ 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 H₂ 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. H₂ lines provide direct quantitative measurements of kinetic energy dissipation in molecular gas in galaxies throughout the Universe. Based on the detection of very powerful H₂ lines from z = 2 galaxies and proto-clusters at the detection limits of Spitzer, we are confident that future far-IR and UV H₂ 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 H₂ 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
Warm H_2 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_2 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_2 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_2 lines from z = 2 galaxies and proto-clusters at the detection limits of Spitzer, we are confident that future far-IR and UV H_2 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_2 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
Integrated systems for biopolymers and bioenergy production from organic waste and by-products: a review of microbial processes
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