Near-Infrared, Adaptive Optics Observations of the T Tauri Multiple-Star System

With high-angular-resolution, near-infrared observations of the young stellar object T Tauri at the end of 2002, we show that, contrary to previous reports, none of the three infrared components of T Tau coincide with the compact radio source that has apparently been ejected recently from the system (Loinard, Rodriguez, and Rodriguez 2003). The compact radio source and one of the three infrared objects, T Tau Sb, have distinct paths that depart from orbital or uniform motion between 1997 and 2000, perhaps indicating that their interaction led to the ejection of the radio source. The path that T Tau Sb took between 1997 and 2003 may indicate that this star is still bound to the presumably more massive southern component, T Tau Sa. The radio source is absent from our near-infrared images and must therefore be fainter than K = 10.2 (if located within 100 mas of T Tau Sb, as the radio data would imply), still consistent with an identity as a low-mass star or substellar object.Comment: 11 pages, 3 figures, submitted to ApJ

The plasma virome in longitudinal samples from pregnant patients

INTRODUCTION: Nucleic acid from viruses is common in peripheral blood, even in asymptomatic individuals. How physiologic changes of pregnancy impact host-virus dynamics for acute, chronic, and latent viral infections is not well described. Previously we found higher viral diversity in the vagina during pregnancy associated with preterm birth (PTB) and Black race. We hypothesized that higher diversity and viral copy numbers in the plasma would show similar trends. METHODS: To test this hypothesis, we evaluated longitudinally collected plasma samples from 23 pregnant patients (11 term and 12 preterm) using metagenomic sequencing with ViroCap enrichment to enhance virus detection. Sequence data were analyzed with the ViroMatch pipeline. RESULTS: We detected nucleic acid from at least 1 virus in at least 1 sample from 87% (20/23) of the maternal subjects. The viruses represented 5 families: DISCUSSION: These results emphasize the importance of longitudinal sampling and diverse cohorts in studies of virome dynamics during pregnancy

Moderate Resolution Spectroscopy For The Space Infrared Telescope Facility (SIRTF)

A conceptual design for an infrared spectrometer capable of both low resolution (λ/Δ-λ = 50; 2.5-200 microns) and moderate resolution (1000; 4-200 microns) and moderate resolution (1000; 4-200 microns) has been developed. This facility instrument will permit the spectroscopic study in the infrared of objects ranging from within the solar system to distant galaxies. The spectroscopic capability provided by this instrument for SIRTF will give astronomers orders of magnitude greater sensitivity for the study of faint objects than had been previously available. The low resolution mode will enable detailed studies of the continuum radiation. The moderate resolution mode of the instrument will permit studies of a wide range of problems, from the infrared spectral signatures of small outer solar system bodies such as Pluto and the satellites of the giant planets, to investigations of more luminous active galaxies and QS0s at substantially greater distances. A simple design concept has been developed for the spectrometer which supports the science investigation with practical cryogenic engineering. Operational flexibility is preserved with a minimum number of mechanisms. The five modules share a common aperture, and all gratings share a single scan mechanism. High reliability is achieved through use of flight-proven hardware concepts and redundancy. The design controls the heat load into the SIRTF cryogen, with all heat sources other than the detectors operating at 7K and isolated from the 4K cold station. Two-dimensional area detector arrays are used in the 2.5-120μm bands to simultaneously monitor adjacent regions in extended objects and to measure the background near point sources

The Extraordinary Mid-infrared Spectrum of the Blue Compact Dwarf Galaxy SBS0335-052

SBS0335-052 is a blue compact dwarf galaxy (BCD) with one of the lowest known metallicities, Z$\sim$Z_{\sun}/41, making it a local example of how primordial starburst galaxies and their precursors might appear. A spectrum obtained with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope clearly shows silicate absorption features, emission lines of [SIV] and [NeIII], and puts strong upper limits on the PAH emission features. The observed low resolution spectrum (R~90) extends from 5.3 to 35microns and peaks at ~28microns. The spectrum is compared to IRS observations of the prototypical starburst nucleus NGC7714. SBS0335-052 is quite unlike normal starburst galaxies, which show strong PAH bands, low ionization emission lines, and a continuum peak near 80microns. The continuum difference for $\lambda >30 \mu$m implies a substantial reduction in the mass of cold dust. If the spectrum of this very low metallicity galaxy is representative of star forming galaxies at higher redshifts, it may be difficult to distinguish them from AGNs which also show relatively featureless flat spectra in the mid-IR.Comment: Accepted in ApJ Sup. Spitzer Special Issue, 4 pages, 2 figure

M/L, H-alpha Rotation Curves, and HI Measurements for 329 Nearby Cluster and Field Spirals: II. Evidence for Galaxy Infall

We have conducted a study of optical and HI properties of spiral galaxies (size, luminosity, H-alpha flux distribution, circular velocity, HI gas mass) to explore the role of gas stripping as a driver of morphological evolution in clusters. We find a strong correlation between the spiral and S0 fractions within clusters, and the spiral fraction scales tightly with cluster X-ray gas luminosity. We explore young star formation and identify spirals that are (1) asymmetric, with truncated H-alpha emission and HI gas reservoirs on the leading edge of the disk, on a first pass through the dense intracluster medium in the cores of rich clusters; (2) strongly HI deficient and stripped, with star formation confined to the inner 5 kpc/h and 3 disk scale lengths; (3) reddened, extremely HI deficient and quenched, where star formation has been halted across the entire disk. We propose that these spirals are in successive stages of morphological transformation, between infalling field spirals and cluster S0s, and that the process which acts to remove the HI gas reservoir suppresses new star formation on a similarly fast timescale. These data suggest that gas stripping plays a significant role in morphological transformation and rapid truncation of star formation across the disk.Comment: 24 pages, 12 figures; accepted for publication in AJ; higher-resolution figures available at http://astronomy.nmsu.edu/nicol

Mid-infrared spectra of PAH emission in Herbig AeBe stars

We present spectra of four Herbig AeBe stars obtained with the Infrared Spectrograph (IRS). on the Spitzer Space Telescope. All four of the sources show strong emission from polycyclic aromatic hydrocarbons (PAHs), with the 6.2 um emission feature shifted to 6.3 um and the strongest C-C skeletal-mode feature occuring at 7.9 um instead of at 7.7 um as is often seen. Remarkably, none of the four stars have silicate emission. The strength of the 7.9 um feature varies with respect to the 11.3 um feature among the sources, indicating that we have observed PAHs with a range of ionization fractions. The ionization fraction is higher for systems with hotter and brighter central stars. Two sources, HD 34282 and HD 169142, show emission features from aliphatic hydrocarbons at 6.85 and 7.25 um. The spectrum of HD 141569 shows a previously undetected emission feature at 12.4 um which may be related to the 12.7 um PAH feature. The spectrum of HD 135344, the coolest star in our sample, shows an unusual profile in the 7-9 um region, with the peak emission to the red of 8.0 um and no 8.6 um PAH feature.Comment: Accepted by ApJ 23 June, 2005, 8 pages (emulateapj), 5 figures (3 in color

The Infrared Spectrograph on the Spitzer Space Telescope

The Infrared Spectrograph (IRS) is one of three science instruments on the Spitzer Space Telescope. The IRS comprises four separate spectrograph modules covering the wavelength range from 5.3 to 38micron with spectral resolutions, R \~90 and 600, and it was optimized to take full advantage of the very low background in the space environment. The IRS is performing at or better than the pre-launch predictions. An autonomous target acquisition capability enables the IRS to locate the mid-infrared centroid of a source, providing the information so that the spacecraft can accurately offset that centroid to a selected slit. This feature is particularly useful when taking spectra of sources with poorly known coordinates. An automated data reduction pipeline has been developed at the Spitzer Science Center.Comment: Accepted in ApJ Sup. Spitzer Special Issue, 6 pages, 4 figure

Dust Processing and Grain Growth in Protoplanetary Disks in the Taurus-Auriga Star-Forming Region

Mid-infrared spectra of 65 T Tauri stars (TTS) taken with the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope are modeled using dust at two temperatures to probe the radial variation in dust composition in the uppermost layers of protoplanetary disks. Most spectra indicating crystalline silicates require Mg-rich minerals and silica, but a few suggest otherwise. Spectra indicating abundant enstatite at higher temperatures also require crystalline silicates at temperatures lower than those required for spectra showing high abundance of other crystalline silicates. A few spectra show 10 micron complexes of very small equivalent width. They are fit well using abundant crystalline silicates but very few large grains, inconsistent with the expectation that low peak-to-continuum ratio of the 10 micron complex always indicates grain growth. Most spectra in our sample are fit well without using the opacities of large crystalline silicate grains. If large grains grow by agglomeration of submicron grains of all dust types, the amorphous silicate components of these aggregates must typically be more abundant than the crystalline silicate components. Crystalline silicate abundances correlate positively with other such abundances, suggesting that crystalline silicates are processed directly from amorphous silicates and that neither forsterite, enstatite, nor silica are intermediate steps when producing either of the other two. Disks with more dust settling typically have greater crystalline abundances. Large-grain abundance is somewhat correlated with greater settling of disks. The lack of strong correlation is interpreted to mean that settling of large grains is sensitive to individual disk properties. Lower-mass stars have higher abundances of large grains in their inner regions.Comment: 84 pages, 27 figures, submitted to the Astrophysical Journal on 7 November, 200