Richard C. Puetter

Infrared spectra of protostars - Composition of the dust shells

Nearly complete 2 to 13 ..mu..m spectra are presented for 13 compact infrared sources associated with molecular clouds, as well as partial spectra of six additional objects. The spectra resemble blackbodies with superposed absorption features from 2.8 to 3.5 ..mu..m, at 6.0 and 6.8 ..mu..m, and in the silicate band centered near 9.7 ..mu..m. Correlations among the features are studied in an attempt to confirm possible identifications. A good correlation between the deepest part of the absorption at 3.1 ..mu..m, its long wavelength wing, and the 6.0 ..mu..m features suggests that all may be due to large amorphous water ice particles. The relatively poor correlation between the 3.4 and 6.8 ..mu..m optical depths adds no evidence to support the suggestion that these bands may be due to CH bonds.

The 4-8 micron spectrum of the infrared source W33 A

The spectrum of the highly obscured infrared source W33 A from 4.5 to 8 microns is measured in order to investigate the intervening cold, dense interstellar material. Spectrophotometry at a relative spectral resolution of about 0.015 by an airborne filter-wheel infrared spectrometer reveals strong absorption features at 4.61, 5.99 and 6.78 microns. The absorption at 4.61 microns is attributed primarily to the fundamental vibration-rotation band of CO at a column density (at least 10 to the 19th/sq cm) which is 10% of the carbon inferred from silicate abundances. The strengths and line widths of the absorption agt 5.99 and 6.78 microns are interpreted as evidence of absorption in the resonance bands of carbonyl, carbon-carbon double, methyl and methylene bonds of hydrocarbons associated with interstellar dust.

Pixon‐based multiresolution image reconstruction and the quantification of picture information content

This article reviews pixon‐based image reconstruction, which in its current formulation uses a multiresolution language to quantify an images algorithmic information content (AIC) using Bayesian techniques. Each pixon (or its generalization, the information) represents a fundamental quanta of an images AIC, and an images pixon basis represents the minimum degrees of freedom necessary to describe the image within the accuracy of the noise. We demonstrate with a number of examples that pixon‐based image reconstruction yields results consistently superior to popular competing methods, including maximum likelihood and maximum entropy methods. Typical improvements include higher spatial resolution, greater sensitivity to faint sources, and immunity to the production of spurious sources and signal correlated residuals. Finally, we show how the pixon provides a generalization of the Akaike information criterion, and how it relates to concepts of “coarse graining” and the role of the Heisenberg uncertainly principle in statistical mechanics, provides a mechanism for optimal data compression, and represents a more optimal basis for image compression or reconstruction than wavelets.

Variability of Disk Emission in Pre-main-sequence and Related Stars. I. HD 31648 and HD 163296: Isolated Herbig Ae Stars Driving Herbig-Haro Flows

Infrared photometry and spectroscopy covering a time span of a quarter-century are presented for HD 31648 (MWC 480) and HD 163296 (MWC 275). Both are isolated Herbig Ae stars that exhibit signs of active accretion, including driving bipolar flows with embedded Herbig-Haro (HH) objects. HD 163296 was found to be relatively quiescent photometrically in its inner disk region, with the exception of a major increase in emitted flux in a broad wavelength region centered near 3 μm in 2002. In contrast, HD 31648 has exhibited sporadic changes in the entire 3-13 μm region throughout this span of time. In both stars, the changes in the 1-5 μm flux indicate structural changes in the region of the disk near the dust sublimation zone, possibly causing its distance from the star to vary with time. Repeated thermal cycling through this region will result in the preferential survival of large grains, and an increase in the degree of crystallinity. The variability observed in these objects has important consequences for the interpretation of other types of observations. For example, source variability will compromise models based on interferometry measurements unless the interferometry observations are accompanied by nearly simultaneous photometric data.

Photometry and Photometric Redshifts of Faint Galaxies in the Hubble Deep Field South NICMOS Field

We present a catalog of photometry and photometric redshifts of 335 faint objects in the Hubble Deep Field South near-infrared camera and multiobject spectrograph (NICMOS) —eld. The analysis is based on (1) infrared images obtained with the Hubble Space Telescope (HST ) using the NICMOS with the F110W, F160W, and F222M —lters; (2) an optical image obtained with HST using the Space Telescope Imaging Spectrograph with no —lter; and (3) optical images obtained with the European Southern Observatory Very Large Telescope with U, B, V , R, and I —lters. The primary utility of the catalog of photometric redshifts is as a survey of faint galaxies detected in the NICMOS F160W and F222M images. The sensitivity of the survey varies signi—cantly with position, reaching a limiting depth of AB(16000) B 28.7 and covering 1.01 arcmin2 to AB(16000) \ 27 and 1.05 arcmin2 to AB(16000) \ 26.5. The catalog of photometric redshifts identi—es 21 galaxies (or 6% of the total) of redshift z ( 5, eight galaxies (or 2% of the total) of redshift z ( 10, and 11 galaxies (or 3% of the total) of best-—t spectral type E/S0, of which —ve galaxies (or 1% of the total) are of redshift z ( 1. Subject headings: cosmology: observationsgalaxies: distances and redshifts ¨ galaxies: photometrygalaxies: statistics

High-Resolution Infrared Imaging and Spectroscopy of the Pistol Nebula: Evidence for Ejection

We present new infrared images, obtained with the Hubble Space Telescope (HST) Near-Infrared Camera and Multiobject Spectrometer (NICMOS), and Brα (4.05 μm) spectroscopy, obtained using CGS4 on UKIRT, of the Pistol Star and its associated nebula. We find strong evidence to support the hypothesis that the Pistol Nebula was ejected from the Pistol Star. The Paα (1.87 μm) NICMOS image shows that the nebula completely surrounds the Pistol Star, although the line intensity is much stronger on its northern and western edges. The Brα CGS4 spectra show the classical ringlike signature of quasi-spherical expansion. The blueshifted emission (Vmax ≈ -60 km s-1) is much weaker than the redshifted emission (Vmax ≈ +10 km s-1), where the velocities are with respect to the velocity of the Pistol Star; further, the redshifted emission spans a very narrow range of velocities, i.e., it appears flattened in the position-velocity diagram. These data suggest that the nebula was ejected from the star several thousand years ago, with a velocity between the current terminal velocity of the stellar wind (95 km s-1) and the present expansion velocity of gas in the outer shell of the nebula (60 km s-1). The Paα image reveals several emission-line stars in the region, including two newly identified emission-line stars north of the Pistol Star, both of which are likely to be the hottest known stars in the Galactic center with spectral types earlier than WC8 and Teff > 50,000 K). The presence of these stars, the morphology of the Paα emission, and the velocity field in the gas suggest that the side of the nebula farthest from us is approaching, and being ionized by, the hot stars of the Quintuplet and that the highest velocity redshifted gas has been decelerated by winds from the Quintuplet stars. We also discuss the possibility that the nebular gas might be magnetically confined by the ambient magnetic field delineated by the nearby nonthermal filaments.

Evidence for methane escape and strong seasonal and dynamical perturbations of Neptune's atmospheric temperatures

Aims. We studied the distribution of mid-infrared thermal emission from Neptune to determine the spatial variability of temperatures and the distribution of trace constituents, allowing us to determine the relative strengths of radiation and dynamics in its atmosphere. Methods. Mid-infrared images of the planet were taken at the Very Large Telescope on 1–2 September 2006. Results. These images reveal strong inhomogeneities in thermal emission. 17.6 and 18.7-µm images exhibit strong seasonally elevated south polar temperatures near Neptune’s tropopause. These high temperatures allow tropospheric methane, elsewhere cold-trapped at depth, to escape into the stratosphere. Poleward of 70 ◦ S, 8.6- and 12.3-µm emission from stratospheric methane and ethane is enhanced, and a distinct, warm stratospheric feature near 65–70 ◦ S latitude is rotating with the neutral atmosphere. This feature may

Keck long-wavelength spectrometer

UCSDs IR astronomy group is building an imaging mid-IR spectrometer for the Keck Telescope. This instrument, the Long-Wavelength Spectrometer (LWS), is built around a 96 X 96 element, Si:As impurity band conduction array built by GenCorp Aerojet Electronics Systems Division. The LWS has low and moderate spectroscopy modes with nominal spectral resolutions of R (equals (lambda) /(Delta) (lambda) ) equals 100 and 1400 respectively, operating in the 10 micrometers (second order) and 20 micrometers (first order) ground- based atmospheric spectral windows. The LWS is also capable of direct imaging from 5 micrometers to 27 micrometers through a selection of 16 filters. For each of the spectroscopic modes and the direct imaging mode, the plate scale is 0.12 arcsec/pixel, which Nyquist samples the telescopes diffraction pattern at 10 micrometers . Because of the large light gathering power of the Keck Telescope and its small diffraction pattern, the LWS will have unparalleled point source sensitivity, making it the premiere instrument for extragalactic and general faint-source mid-IR spectroscopy.

0.8-2.5 Micron Spectroscopy of Nova Ophiuchi 1998*

We report 0.8-2.5 μm spectroscopy of the very fast Nova Ophiuchi 1998 from June 19 and 22 to October 2.15 1998 UT. On the first night the Paschen and Brackett emission lines dominated the spectrum, although He I 1.0830 μm was the strongest single line present and He II was very weak. There were also broad, symmetric emission wings underlying the H I and He I lines with FWHM of about 10,000 km s-1. Three nights later the rapid evolution of the nova to higher excitation conditions was evident from the much stronger He II lines which had increased by a factor of 4 relative to the hydrogen lines. The C III line at 0.9710 μm also appeared the second night, a line that we have heretofore seen only in Wolf-Rayet stars and which almost certainly indicates an overabundance of carbon. The broad emission wings were also present. About 110 days later on October 2.15 UT, the emission lines were very weak (5%-15% of the continuum) and only a few Paschen features and lines of He II were present. At no time during our observations was there any evidence of a long-wavelength upturn indicative of thermal emission from dust. The continuum magnitudes on the dates of observation at J (1.25 microns) were 9.4, 10.9 to 15.0, respectively. The optical decline of 0.37 mag day-1 makes this nova one of the fastest ever seen. Model fits of the broad lines profiles suggest that they originate in an optically thin, spherically expanding shell. The line ratios from the narrow components deviate significantly from case B values and seem to come from an optically thick (τ = 10-100 at line center in Paα), high-density (ne ~ 1011 cm-3) gas at around 10,000 K.

The 4 to 8 micron spectrum of the galactic center

Observations of the complex Sgr A W(N) with a 28-arcsec beam and 1.5% spectral resolution are reported. Neither unidentified absorption features at 6.0 and 6.8 microns nor emission features at 6.2 and 7.7 microns were detected. The absence of the absorption features demonstrates that they are not characteristic of general interstellar extinction. The absence of emission features suggests that there is considerable distance between the ionized gas and the molecular clouds. The absence of 6.2- and 7.7-micron emission features also suggests that a feature previously seen at 3.3-3.4 microns is an absorption at 3.4 microns, and this absorption is apparently characteristic of interstellar extinction. The strength of the forbidden Ar II emission indicates an overabundance of argon. CO absorption seen at 4.67 microns indicates that saturation effects are not large, and there is evidently a large velocity dispersion in the line of sight to the infrared sources.