Abstract
We describe a
Herschel Space Observatory
194–671
μ
m spectroscopic survey of a sample of 121 local luminous infrared galaxies and report the fluxes of the CO
J
to
J
–1 rotational transitions ...for
, the N
ii
205
μ
m line, the C
i
lines at 609 and 370
μ
m, as well as additional and usually fainter lines. The CO spectral line energy distributions (SLEDs) presented here are consistent with our earlier work, which was based on a smaller sample, that calls for two distinct molecular gas components in general: (i) a cold component, which emits CO lines primarily at
J
≲ 4 and likely represents the same gas phase traced by CO (1−0), and (ii) a warm component, which dominates over the mid-
J
regime (4 <
J
≲ 10) and is intimately related to current star formation. We present evidence that the CO line emission associated with an active galactic nucleus is significant only at
J
> 10. The flux ratios of the two C
i
lines imply modest excitation temperatures of 15–30 K; the C
i
370
μ
m line scales more linearly in flux with CO (4−3) than with CO (7−6). These findings suggest that the C
i
emission is predominantly associated with the gas component defined in (i) above. Our analysis of the stacked spectra in different far-infrared (FIR) color bins reveals an evolution of the SLED of the rotational transitions of
vapor as a function of the FIR color in a direction consistent with infrared photon pumping.
The Great Observatories All-sky LIRG Survey (GOALS) consists of a complete sample of 202 luminous infrared galaxies (LIRGs) selected from the IRAS Revised Bright Galaxy Sample (RBGS). The galaxies ...span the full range of interaction stages, from isolated galaxies to interacting pairs to late stage mergers. We present a comparison of the UV and infrared properties of 135 galaxies in GOALS observed by GALEX and Spitzer. For interacting galaxies with separations greater than the resolution of GALEX and Spitzer (~2''-6''), we assess the UV and IR properties of each galaxy individually. The contribution of the FUV to the measured star formation rate (SFR) ranges from 0.2% to 17.9%, with a median of 2.8% and a mean of 4.0% ± 0.4%. The specific star formation rate (SSFR) of the GOALS sample is extremely high, with a median value (3.9 × 10-10 yr-1) that is comparable to the highest SSFRs seen in the Spitzer Infrared Nearby Galaxies Survey sample. We examine the position of each galaxy on the IR excess-UV slope (IRX-beta) diagram as a function of galaxy properties, including IR luminosity and interaction stage. The LIRGs on average have greater IR excesses than would be expected based on their UV colors if they obeyed the same relations as starbursts with L IR < 1011 L sun or normal late-type galaxies. The ratio of L IR to the value one would estimate from the IRX-beta relation published for lower luminosity starburst galaxies ranges from 0.2 to 68, with a median value of 2.7. A minimum of 19% of the total IR luminosity in the RBGS is produced in LIRGs and ultraluminous infrared galaxies with red UV colors (beta>0). Among resolved interacting systems, 32% contain one galaxy which dominates the IR emission while the companion dominates the UV emission. Only 21% of the resolved systems contain a single galaxy which dominates both wavelengths.
The Spitzer Survey of Stellar Structure in Galaxies (inline image) is an Exploration Science Legacy Program approved for the Spitzer post-cryogenic mission. It is a volume-, magnitude-, and ...size-limited (d < 40 Mpc,
Almost every known low-luminosity Milky Way dwarf spheroidal (dSph) satellite galaxy contains at least one RR Lyrae star. Assuming that a fraction of distant (60 < d sub(helio) < 100 kpc) Galactic ...halo RR Lyrae stars are members of yet to be discovered low-luminosity dSph galaxies, we perform a guided search for these low-luminosity dSph galaxies. In order to detect the presence of dSph galaxies, we combine stars selected from more than 123 sightlines centered on RR Lyrae stars identified by the Palomar Transient Factory. We find that this method is sensitive enough to detect the presence of Segue 1-like galaxies (MV = (ProQuest: Formulae and/or non-USASCII text omitted), rh = 30 pc) even if only ~20 sightlines were occupied by such dSph galaxies. Yet, when our method is applied to the Sloan Digital Sky Survey Data Release 10 imaging catalog, no signal is detected. An application of our method to sightlines occupied by pairs of close (<200 pc) horizontal branch stars, also did not yield a detection. Thus, we place upper limits on the number of low-luminosity dSph galaxies with half-light radii from 30 pc to 120 pc, and in the probed volume of the halo. Stronger constraints on the luminosity function may be obtained by applying our method to sightlines centered on RR Lyrae stars selected from the Pan-STARRS1 survey, and eventually, from the Large Synoptic Survey Telescope. In Appendix A, we present spectroscopic observations of an RRab star in the Bootes 3 dSph and a light curve of an RRab star near the Bootes 2 dSph.
We report positions, velocities, and metallicities of 50 ab-type RR Lyrae (RRab) stars observed in the vicinity of the Orphan stellar stream. Using about 30 RRab stars classified as being likely ...members of the Orphan stream, we study the metallicity and the spatial extent of the stream. We find that RRab stars in the Orphan stream have a wide range of metallicities, from -1.5 dex to -2.7 dex. The average metallicity of the stream is -2.1 dex, identical to the value obtained by Newberg et al. using blue horizontal branch stars. We find that the most distant parts of the stream (40-50 kpc from the Sun) are about 0.3 dex more metal-poor than the closer parts (within ~30 kpc), suggesting a possible metallicity gradient along the stream's length. We have extended the previous studies and have mapped the stream up to 55 kpc from the Sun. Even after a careful search, we did not identify any more distant RRab stars that could plausibly be members of the Orphan stream. If confirmed with other tracers, this result would indicate a detection of the end of the leading arm of the stream. We have compared the distances of Orphan stream RRab stars with the best-fit orbits obtained by Newberg et al. We find that model 6 of Newberg et al. cannot explain the distances of the most remote Orphan stream RRab stars, and conclude that the best fit to distances of Orphan stream RRab stars and to the local circular velocity is provided by potentials where the total mass of the Galaxy within 60 kpc is M sub(60) ~ 2.7 x 10 super(11) M sub(middot in circle), or about 60% of the mass found by previous studies. More extensive modeling that would consider non-spherical potentials and the possibility of misalignment between the stream and the orbit is highly encouraged.
We report observations of a possible young transiting planet orbiting a previously known weak-lined T-Tauri star in the 7-10 Myr old Orion-OB1a/25-Ori region. The candidate was found as part of the ...Palomar Transient Factory (PTF) Orion project. It has a photometric transit period of 0.448413 + or - 0.000040 days, and appears in both 2009 and 2010 PTF data. Follow-up low-precision radial velocity (RV) observations and adaptive optics imaging suggest that the star is not an eclipsing binary, and that it is unlikely that a background source is blended with the target and mimicking the observed transit. RV observations with the Hobby-Eberly and Keck telescopes yield an RV that has the same period as the photometric event, but is offset in phase from the transit center by approx = - 0.22 periods. The amplitude (half range) of the RV variations is 2.4 km s super(-1) and is comparable with the expected RV amplitude that stellar spots could induce. The RV curve is likely dominated by stellar spot modulation and provides an upper limit to the projected companion mass of M sub(p) sin i sub(orb) <, ~4.8 + or - 1.2 M sub(Jup); when combined with the orbital inclination, i sub(orb), of the candidate planet from modeling of the transit light curve, we find an upper limit on the mass of the planetary candidate of M sub(p) <, ~5.5 + or - 1.4 M sub(Jup). This limit implies that the planet is orbiting close to, if not inside, its Roche limiting orbital radius, so that it may be undergoing active mass loss and evaporation.
Using the large multiwavelength data set in the Chandra/SWIRE Survey (0.6 deg super(2) in the Lockman Hole), we show evidence for the existence of highly obscured (Compton-thick) AGNs, estimate a ...lower limit to their surface density, and characterize their multiwavelength properties. Two independent selection methods based on the X-ray and infrared spectral properties are presented. The two selected samples contain (1) five X-ray sources with hard X-ray spectra and column densities 10 super(24) cm super(-2) and (2) 120 infrared sources with red and AGN-dominated infrared SEDs. We estimate a surface density of at least 25 Compton-thick AGNs deg super(-2) detected in the infrared in the Chandra/SWIRE field, of which 640% show distinct AGN signatures in their optical/near-infrared SEDs, the remaining being dominated by the host galaxy emission. Only 633% of all Compton-thick AGNs are detected in the X-rays at our depth F(0.3-8 keV) > 10 super(-15) ergs cm super(-2) s super(-1). We report the discovery of two sources in our sample of Compton-thick AGNs, SWIRE J104409.95+585224.8 (z = 2.54) and SWIRE J104406.30+583954.1 (z = 2.43), which are the most luminous Compton-thick AGNs at high z currently known. The properties of these two sources are discussed in detail with an analysis of their spectra, SEDs, luminosities, and black hole masses.
The Near-Earth Object Surveyor Mission Mainzer, A. K.; Masiero, J. R.; Abell, Paul A. ...
The planetary science journal,
12/2023, Volume:
4, Issue:
12
Journal Article
Peer reviewed
Open access
Abstract
The Near-Earth Object (NEO) Surveyor mission is a NASA Observatory designed to discover and characterize asteroids and comets. The mission’s primary objective is to find the majority of ...objects large enough to cause severe regional impact damage (>140 m in effective spherical diameter) within its 5 yr baseline survey. Operating at the Sun–Earth L1 Lagrange point, the mission will survey to within 45° of the Sun in an effort to find objects in the most Earth-like orbits. The survey cadence is optimized to provide observational arcs long enough to distinguish near-Earth objects from more distant small bodies that cannot pose an impact hazard reliably. Over the course of its survey, NEO Surveyor will discover ∼200,000–300,000 new NEOs down to sizes as small as ∼10 m and thousands of comets, significantly improving our understanding of the probability of an Earth impact over the next century.
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