Michael J. Wolff

GLIMPSE. I. An SIRTF Legacy Project to Map the Inner Galaxy

ABSTRACT The Galactic Legacy Infrared Mid‐Plane Survey Extraordinaire (GLIMPSE), a Space Infrared Telescope Facility (SIRTF) Legacy Science Program, will be a fully sampled, confusion‐limited infrared survey of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

A Quantitative Comparison of the Small Magellanic Cloud, Large Magellanic Cloud, and Milky Way Ultraviolet to Near-Infrared Extinction Curves*

\frac{2}{3}

TWO-DIMENSIONAL RADIATIVE TRANSFER IN PROTOSTELLAR ENVELOPES. I. EFFECTS OF GEOMETRY ON CLASS I SOURCES

\end{document} of the inner Galactic disk with a pixel resolution of ∼1 \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \u...

The Spectral Energy Distribution of HH 30 IRS: Constraining the Circumstellar Dust Size Distribution

We present an exhaustive, quantitative comparison of all of the known extinction curves in the Small and Large Magellanic Clouds (SMC and LMC) with our understanding of the general behavior of Milky Way extinction curves. The R_V dependent CCM relationship and the sample of extinction curves used to derive this relationship is used to describe the general behavior of Milky Way extinction curves. The ultraviolet portion of the SMC and LMC extinction curves are derived from archival IUE data, except for one new SMC extinction curve which was measured using HST/STIS observations. The optical extinction curves are derived from new (for the SMC) and literature UBVRI photometry (for the LMC). The near-infrared extinction curves are calculated mainly from 2MASS photometry supplemented with DENIS and new JHK photometry. For each extinction curve, we give R_V = A(V)/E(B-V) and N(HI) values which probe the same dust column as the extinction curve. We compare the properties of the SMC and LMC extinction curves with the CCM relationship three different ways: each curve by itself, the behavior of extinction at different wavelengths with R_V, and behavior of the extinction curve FM fit parameters with R_V. As has been found previously, we find that a small number of LMC extinction curves are consistent with the CCM relationship, but majority of the LMC and all of the SMC curves do not follow the CCM relationship. For the first time, we find that the CCM relationship seems to form a bound on the properties of all of the LMC and SMC extinction curves. This result strengthens the picture of dust extinction curves exhibit a continuum of properties between those found in the Milky Way and the SMC Bar. (abridged)We present an exhaustive quantitative comparison of all the known extinction curves in the Small and Large Magellanic Clouds (SMC and LMC) with our understanding of the general behavior of Milky Way extinction curves. The RV-dependent CCM relationship of Cardelli, Clayton, and Mathis and the sample of extinction curves used to derive this relationship are used to describe the general behavior of Milky Way extinction curves. The ultraviolet portion of the SMC and LMC extinction curves are derived from archival IUE data, except for one new SMC extinction curve, which was measured using Hubble Space Telescope Space Telescope Imaging Spectrograph observations. The optical extinction curves are derived from new (for the SMC) and literature UBVRI photometry (for the LMC). The near-infrared extinction curves are calculated mainly from 2MASS photometry supplemented with DENIS and new JHK photometry. For each extinction curve, we give RV = A(V)/E(B - V) and N(H I) values that probe the same dust column as the extinction curve. We compare the properties of the SMC and LMC extinction curves with the CCM relationship three different ways: each curve by itself, the behavior of extinction at different wavelengths with RV, and the behavior of the extinction curve Fitzpatrick and Massa fit parameters with RV. As has been found previously, we find that a small number of LMC extinction curves are consistent with the CCM relationship, but the majority of the LMC and all the SMC curves do not follow the CCM relationship. For the first time, we find that the CCM relationship seems to form a bound on the properties of all the LMC and SMC extinction curves. This result strengthens the picture dust extinction curves exhibit of a continuum of properties between those found in the Milky Way and the SMC bar. Tentative evidence based on the behavior of the extinction curves with dust-to-gas ratio suggests that the continuum of dust extinction curves is possibly caused by the environmental stresses of nearby star formation activity.

First Atmospheric Science Results from the Mars Exploration Rovers Mini-TES

We present two-dimensional radiation transfer models of class I protostars and show the effect of including more realistic geometries on the resulting spectral energy distributions and images. We begin with a rotationally flattened infalling envelope as our comparison model and add a flared disk and bipolar cavity. The disk affects the spectral energy distribution most strongly at edge-on inclinations, causing a broad dip at about 10 lm (independent of the silicate feature) due to high extinction and low scattering albedo in this wavelength region. The bipolar cavities allow more direct stellar+disk radiation to emerge into polar directions and more scattering radiation to emerge into all directions. The wavelength-integrated flux, often interpreted as luminosity, varies with viewing angle, with pole-on viewing angles seeing 2–4 times as much flux as edge-on, depending on geometry. Thus, observational estimates of luminosity should take into account the inclination of a source. The envelopes with cavities are significantly bluer in near-IR and mid-IR color-color plots than those without cavities. Using one-dimensional models to interpret Class I sources with bipolar cavities would lead to an underestimate of envelope mass and an overestimate of the implied evolutionary state. We compute images at near-, mid-, and far-IR wavelengths. We find that the mid-IR colors and images are sensitive to scattering albedo and that the flared disk shadows the midplane on large size scales at all wavelengths plotted. Finally, our models produce polarization spectra that can be used to diagnose dust properties, such as albedo variations due to grain growth. Our results of polarization across the 3.1 l mi ce feature agree well with observations for ice mantles covering 5% of the radius of the grains. Subject headings: circumstellar matter — dust, extinction — polarization — radiative transfer — stars: formation — stars: pre–main-sequence

Infrared Signatures of Protoplanetary Disk Evolution

We present spectral energy distribution (SED) models for the edge-on classical T Tauri star HH 30 IRS that indicate that dust grains have grown to larger than 50 μm within its circumstellar disk. The disk geometry and inclination are known from previous modeling of multiwavelength Hubble Space Telescope images, and we use the SED (0.5 μm ≤ λ ≤ 3 mm) to constrain the dust size distribution. Model spectra are shown for different circumstellar dust models: a standard interstellar medium (ISM) mixture and larger grain models. As compared to ISM grains, the larger dust grain models have a shallower wavelength-dependent opacity: smaller at short wavelengths and larger at long wavelengths. Models with the larger dust grains provide a good match to the observed SED of HH 30 IRS. Although the currently available SED is poorly sampled, we estimate L* ≈ 0.2 L☉, Mdisk ≈ 1.5 × 10-3 M☉, and a power law with exponential cutoff dust grain size distribution. This model provides a good fit to the currently available data, but mid- and far-IR observations are required to more tightly constrain the size distribution. The accretion luminosity in our models is Lacc 0.2L*, corresponding to an accretion rate 4 × 10-9 M☉ yr-1. Dust size distributions that are simple power-law extensions (i.e., no exponential cutoff) yield acceptable fits to the optical/near-IR but too much emission at millimeter wavelengths, and require larger disk masses up to Mdisk ~ 0.5 M☉. Such a simple size distribution would not be expected in an environment such as the disk of HH 30 IRS (i.e., where coagulation and accretion processes are occurring in addition to grain shattering), particularly over such a large range in grain sizes. Its ability to adequately characterize the grain populations, however, may be determined from more complete observational sampling of the SED in the mid- to far-IR.

High-resolution near-infrared images and models of the circumstellar disk in hh 30

Thermal infrared spectra of the martian atmosphere taken by the Miniature Thermal Emission Spectrometer (Mini-TES) were used to determine the atmospheric temperatures in the planetary boundary layer and the column-integrated optical depth of aerosols. Mini-TES observations show the diurnal variation of the martian boundary layer thermal structure, including a near-surface superadiabatic layer during the afternoon and an inversion layer at night. Upward-looking Mini-TES observations show warm and cool parcels of air moving through the Mini-TES field of view on a time scale of 30 seconds. The retrieved dust optical depth shows a downward trend at both sites.

Dust Grain-Size Distributions From MRN to MEM

We investigate the observational signatures of a straightforward evolutionary scenario for protoplanetary disks, in which the disk mass of small km) particles decreases homologously with time, but ([50 the disk structure and stellar parameters do not change. Our goal is to identify optimal infrared spectral indicators of the existence of disks, their structure, and mass evolution that may be tested with the upcoming SIRT F mission. We present simulated spectral energy distributions (SEDs) and colors over a wide range of masses, 10~8 Our Monte Carlo radiative equilibrium techniques M _ „ M disk „ 10~1 M _ . enable us to explore the wide range of optical depths of these disks and incorporate multiple, anisotropic dust scattering. The SED is most sensitive to disk mass in the far-IR and longer wavelengths, as is already known from millimeter and radio observations. As the disk mass decreases, the excess emission of the disk over the stellar photosphere diminishes more rapidly at the longest than at short wavelengths. At near-infrared wavelengths, the disk remains optically thick to stellar radiation over a wide range of disk masses, resulting in a slower decline in the SED in this spectral regime. Therefore, near-IR excesses (K[L ) provide a robust means of detecting disks in star clusters down to M disk D 10~7 M _ , while the far-IR excess probes the disk mass, the caveat being that large inner-disk holes can decrease the near-IR disk emission. Various other disk parameters (outer radius, —aring, and dust size distribution) alter the SED quantitatively, but do not change our general conclusions on the evolution of SEDs and colors with the mass of small particles in the disk. Reducing the disk mass results in a clear progression in color-color diagrams, with low-mass disks displaying the bluest colors. We interpret color-color diagrams for TaurusAuriga sources in the context of decreasing disk mass. DiUerent viewing angles yield degeneracies in the color-mass relationship, but highly inclined disks are very faint and red and are readily identi—ed in color-magnitude diagrams.

Seasonal melting and the formation of sedimentary rocks on Mars, with predictions for the Gale Crater mound

We present Hubble Space Telescope near-infrared camera and multiobject spectrometer observations of the reflection nebulosity associated with the T Tauri star HH 30. The images show the scattered-light pattern characteristic of a highly inclined, optically thick disk with a prominent dust lane whose width decreases with increasing wavelength. The reflected nebulosity exhibits a lateral asymmetry in the upper lobe on the opposite side to that reported in previously published Wide Field Planetary Camera 2 images. The radiation transfer model that most closely reproduces the data has a flared accretion disk with dust grains larger than standard interstellar medium grains by a factor of approximately 2.1. A single hot spot on the stellar surface provides the necessary asymmetry to fit the images and is consistent with previous modeling of the light curve and images. Photometric analysis results in an estimated extinction of AV 80; however, since the photometry measures only scattered light rather than direct stellar flux, this a lower limit. The radiative transfer models require an extinction of AV = 7900.

Hubble Space Telescope observations of the Martian aphelion cloud belt prior to the Pathfinder mission: Seasonal and interannual variations

Employing the maximum entropy method (MEM) algorithm, we fit interstellar extinction measurements that span the wavelength range 0.125-3 μm. We present a uniform set of MEM model fits, all using the same grain materials, optical constants, and abundance constraints. In addition, we are taking advantage of improved UV and IR data and better estimates of the gas-to-dust ratio. The model fits cover the entire range of extinction properties that have been seen in the Galaxy and the Magellanic Clouds. The grain models employed for this presentation are the simplistic homogeneous sphere models (i.e., those of Mathis, Rumpl, & Nordsieck in 1977) with two (graphite, silicate) or three (graphite, silicate, amorphous carbon) components. Although such usage is only a first step, the results do provide interesting insight into the use of grain size as a diagnostic of dust environment. We find that the SMC bar extinction curve cannot be fitted using carbon grains alone. This is a challenge to the recent observational result indicating little silicon depletion in the SMC.