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Near-infrared (IR) imaging polarimetry in the J, H, and Ks bands has been carried out for the protostellar cluster region around NGC 2264 IRS 2 in the Monoceros OB1 molecular cloud. Various infrared reflection nebulae clusters (IRNCs) associated with NGC 2264 IRS 2 and IRAS 12 S1 core were detected as well as local infrared reflection nebulae (IRNe). The illuminating sources of the IRNe were identified with known or new near- and mid-IR sources. In addition, 314 point-like sources were detected in all three bands and their aperture polarimetry was studied. Using a color-color diagram, reddened field stars and diskless pre-main sequence stars were selected to trace the magnetic field (MF) structure of the molecular cloud. The mean polarization position angle of the point-like sources is 81 \pm 29 degree in the cluster core, and 58 \pm 24 degree in the perimeter of the cluster core, which is interpreted as the projected direction on the sky of the MF in the observed region of the cloud. The Chandrasekhar-Fermi method gives a rough estimate of the MF strength to be about 100 {\mu}G. A comparison with recent numerical simulations of the cluster formation implies that the cloud dynamics is controlled by the relatively strong MF. The local MF direction is well associated with that of CO outflow for IRAS 12 S1 and consistent with that inferred from submillimeter polarimetry. In contrast, the local MF direction runs roughly perpendicular to the Galactic MF direction., Comment: To appear in the Astrophysical Journal, 31 pages, 19 Postscript figures

The fullerene C$_{60}$ has four infrared-active vibrational transitions at 7.0, 8.5, 17.4 and 18.9 $\mu$m. We have previously observed emission features at 17.4 and 18.9 $\mu$m in the reflection nebula NGC 7023 and demonstrated spatial correlations suggestive of a common origin. We now confirm our earlier identification of these features with C$_{60}$ by detecting a third emission feature at 7.04 $\pm$ 0.05 $\mu$m in NGC 7023. We also report the detection of these three C$_{60}$ features in the reflection nebula NGC 2023. Our spectroscopic mapping of NGC 7023 shows that the 18.9 $\mu$m C$_{60}$ feature peaks on the central star and that the 16.4 $\mu$m emission feature due to polycyclic aromatic hydrocarbons peaks between the star and a nearby photodissociation front. The observed features in NGC 7023 are consistent with emission from UV-excited gas-phase C$_{60}$. We find that 0.1-0.6% of interstellar carbon is in C$_{60}$; this abundance is consistent with those from previous upper limits and possible fullerene detections in the interstellar medium. This is the first firm detection of neutral C$_{60}$ in the interstellar medium., Comment: ApJ Letters, in press

Explorers have made breakthroughs in many fields of astrophysics. The science from both these missions contributed to three Nobel Prizes - Giacconi (2002), Mather, and Smoot (2006). Explorers have: marked the definitive beginning of precision cosmology, discovered that short gamma-ray bursts are caused by compact star mergers and have measured metalicity to redshifts z>6. NASA Explorers do cutting-edge science that cannot be done by facility-class instruments. The Explorer program provides a rapid response to changing science and technology, to enable cutting-edge science at moderate cost. Explorers also enable innovation, and engage & train scientists, managers and engineers, adding human capital to NASA and the nation. The astrophysics Explorer launch rate now being achieved is 1 per 3 years, and budget projections are in the $150M/year range for the next five years. A newly Vigorous Explorer Program should be created to: 1. Reach the long-stated goal of annual astrophysics launches; 2. Find additional launch options for Explorers and actively encourage cost savings in launchers and spacecraft, such as new commercial vehicles and innovative partnerships. 3. Mitigate risk via stronger technical development and sub-orbital programs, and through longer, more thorough, Phase A programs, potentially reducing the need for a 30% contingency; 4. Strive to protect the funding for missions that have reached Phase B, to prevent significant launch slips and cancellations, with a goal of 4 to 5 years from Phase B to launch; 5. Review the project management procedures and requirements to seek cost reductions, including the risk management strategy and the review and reporting process; 6. Review and possibly modify the cost caps for all Explorer classes to optimize scientific returns per dollar. [ABRIDGED], Comment: 18 pages, no figures. An Activities/Program White Paper submitted to the Astro2010 NAS/NRC Decadal Review of Astronomy and Astrophysics

We present Spitzer observations of a sample of 12 starless cores selected to have prominent 24 micron shadows. The Spitzer images show 8 and 24 micron shadows and in some cases 70 micron shadows; these spatially resolved absorption features trace the densest regions of the cores. We have carried out a 12CO (2-1) and 13CO (2-1) mapping survey of these cores with the Heinrich Hertz Telescope (HHT). We use the shadow features to derive optical depth maps. We derive molecular masses for the cores and the surrounding environment; we find that the 24 micron shadow masses are always greater than or equal to the molecular masses derived in the same region, a discrepancy likely caused by CO freeze--out onto dust grains. We combine this sample with two additional cores that we studied previously to bring the total sample to 14 cores. Using a simple Jeans mass criterion we find that ~ 2/3 of the cores selected to have prominent 24 micron shadows are collapsing or near collapse, a result that is supported by millimeter line observations. Of this subset at least half have indications of 70 micron shadows. All cores observed to produce absorption features at 70 micron are close to collapse. We conclude that 24 micron shadows, and even more so the 70 micron ones, are useful markers of cloud cores that are approaching collapse., Comment: 41 pages, 28 figures, 5 tables; accepted by ApJ

The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a set of mission concepts for the next generation of UVOIR space observatory with a primary aperture diameter in the 8-m to 16-m range that will allow us to perform some of the most challenging observations to answer some of our most compelling questions, including "Is there life elsewhere in the Galaxy?" We have identified two different telescope architectures, but with similar optical designs, that span the range in viable technologies. The architectures are a telescope with a monolithic primary mirror and two variations of a telescope with a large segmented primary mirror. This approach provides us with several pathways to realizing the mission, which will be narrowed to one as our technology development progresses. The concepts invoke heritage from HST and JWST design, but also take significant departures from these designs to minimize complexity, mass, or both. Our report provides details on the mission concepts, shows the extraordinary scientific progress they would enable, and describes the most important technology development items. These are the mirrors, the detectors, and the high-contrast imaging technologies, whether internal to the observatory, or using an external occulter. Experience with JWST has shown that determined competitors, motivated by the development contracts and flight opportunities of the new observatory, are capable of achieving huge advances in technical and operational performance while keeping construction costs on the same scale as prior great observatories., Comment: 22 pages, RFI submitted to Astro2010 Decadal Committee

We present mid-infrared spectral maps of the NGC 1333 star forming region, obtained with the the Infrared Spectrometer on board the Spitzer Space Telescope. Eight pure H2 rotational lines, from S (0) to S (7), are detected and mapped. The H2 emission appears to be associated with the warm gas shocked by the multiple outflows present in the region. A comparison between the observed intensities and the predictions of detailed shock models indicates that the emission arises in both slow (12 - 24 km/s) and fast (36 - 53 km/s) C-type shocks with an initial ortho-to-para ratio of ~ 1. The present H2 ortho-to-para ratio exhibits a large degree of spatial variations. In the post-shocked gas, it is usually about 2, i.e. close to the equilibrium value (~ 3). However, around at least two outflows, we observe a region with a much lower (~ 0.5) ortho-to-para ratio. This region probably corresponds to gas which has been heated-up recently by the passage of a shock front, but whose ortho-to-para has not reached equilibrium yet. This, together with the low initial ortho-to-para ratio needed to reproduce the observed emission, provide strong evidence that H2 is mostly in para form in cold molecular clouds. The H2 lines are found to contribute to 25 - 50% of the total outflow luminosity, and thus can be used to ascertain the importance of star formation feedback on the natal cloud. From these lines, we determine the outflow mass loss rate and, indirectly, the stellar infall rate, the outflow momentum and the kinetic energy injected into the cloud over the embedded phase. The latter is found to exceed the binding energy of individual cores, suggesting that outflows could be the main mechanism for core disruption., Comment: Accepted for publication in the Astrophysical Journal

This white paper is submitted to the Astronomy and Astrophysics 2010 Decadal Survey (Astro2010)1 Committee on the State of the Profession to emphasize the potential of the Stratospheric Observatory for Infrared Astronomy (SOFIA) to contribute to the training of instrumentalists and observers, and to related technology developments. This potential goes beyond the primary mission of SOFIA, which is to carry out unique, high priority astronomical research. SOFIA is a Boeing 747SP aircraft with a 2.5 meter telescope. It will enable astronomical observations anywhere, any time, and at most wavelengths between 0.3 microns and 1.6 mm not accessible from ground-based observatories. These attributes, accruing from the mobility and flight altitude of SOFIA, guarantee a wealth of scientific return. Its instrument teams (nine in the first generation) and guest investigators will do suborbital astronomy in a shirt-sleeve environment. The project will invest $10M per year in science instrument development over a lifetime of 20 years. This, frequent flight opportunities, and operation that enables rapid changes of science instruments and hands-on in-flight access to the instruments, assure a unique and extensive potential - both for training young instrumentalists and for encouraging and deploying nascent technologies. Novel instruments covering optical, infrared, and submillimeter bands can be developed for and tested on SOFIA by their developers (including apprentices) for their own observations and for those of guest observers, to validate technologies and maximize observational effectiveness., Comment: 10 pages, no figures, White Paper for Astro 2010 Survey Committee on State of the Profession

(Brief Summary) What is the total radiative content of the Universe since the epoch of recombination? The extragalactic background light (EBL) spectrum captures the redshifted energy released from the first stellar objects, protogalaxies, and galaxies throughout cosmic history. Yet, we have not determined the brightness of the extragalactic sky from UV/optical to far-infrared wavelengths with sufficient accuracy to establish the radiative content of the Universe to better than an order of magnitude. Among many science topics, an accurate measurement of the EBL spectrum from optical to far-IR wavelengths, will address: What is the total energy released by stellar nucleosynthesis over cosmic history? Was significant energy released by non-stellar processes? Is there a diffuse component to the EBL anywhere from optical to sub-millimeter? When did first stars appear and how luminous was the reionization epoch? Absolute optical to mid-IR EBL spectrum to an astrophysically interesting accuracy can be established by wide field imagingat a distance of 5 AU or above the ecliptic plane where the zodiacal foreground is reduced by more than two orders of magnitude., Comment: 7 pages; Science White Paper for the US Astro 2010-2020 Decadal Survey. If interested in further community-wide efforts on this topic please contact the first author

We present infrared and millimeter observations of Barnard 335, the prototypical isolated Bok globule with an embedded protostar. Using Spitzer data we measure the source luminosity accurately; we also constrain the density profile of the innermost globule material near the protostar using the observation of an 8.0 um shadow. HHT observations of 12CO 2 --> 1 confirm the detection of a flattened molecular core with diameter ~10000 AU and the same orientation as the circumstellar disk (~100 to 200 AU in diameter). This structure is probably the same as that generating the 8.0 um shadow and is expected from theoretical simulations of collapsing embedded protostars. We estimate the mass of the protostar to be only ~5% of the mass of the parent globule., Comment: 15 pages, 17 figures, emulateapj format, accepted for publication in ApJ

We report the mid- and far-infrared properties of nearby M dwarfs. Spitzer/MIPS measurements were obtained for a sample of 62 stars at 24 um, with subsamples of 41 and 20 stars observed at 70 um and 160 um respectively. We compare the results with current models of M star photospheres and look for indications of circumstellar dust in the form of significant deviations of K-[24 um] colors and 70 um / 24 um flux ratios from the average M star values. At 24 um, all 62 of the targets were detected; 70 um detections were achieved for 20 targets in the subsample observed; and no detections were seen in the 160 um subsample. No clear far-infrared excesses were detected in our sample. The average far infrared excess relative to the photospheric emission of the M stars is at least four times smaller than the similar average for a sample of solar-type stars. However, this limit allows the average fractional infrared luminosity in the M-star sample to be similar to that for more massive stars. We have also set low limits for the maximum mass of dust possible around our stars., Comment: 28 pages, 4 figures, to be published in The Astrophysical Journal

We present Spitzer observations of the dark globule CB190 (L771). We observe a roughly circular 24 micron shadow with a 70 arcsec radius. The extinction profile of this shadow matches the profile derived from 2MASS photometry at the outer edges of the globule and reaches a maximum of ~32 visual magnitudes at the center. The corresponding mass of CB190 is ~10 Msun. Our 12CO and 13CO J = 2-1 data over a 10 arcmin X 10 arcmin region centered on the shadow show a temperature ~10 K. The thermal continuum indicates a similar temperature for the dust. The molecular data also show evidence of freezeout onto dust grains. We estimate a distance to CB190 of 400 pc using the spectroscopic parallax of a star associated with the globule. Bonnor-Ebert fits to the density profile, in conjunction with this distance, yield xi_max = 7.2, indicating that CB190 may be unstable. The high temperature (56 K) of the best fit Bonnor-Ebert model is in contradiction with the CO and thermal continuum data, leading to the conclusion that the thermal pressure is not enough to prevent free-fall collapse. We also find that the turbulence in the cloud is inadequate to support it. However, the cloud may be supported by the magnetic field, if this field is at the average level for dark globules. Since the magnetic field will eventually leak out through ambipolar diffusion, it is likely that CB190 is collapsing or in a late pre-collapse stage., Comment: 16 pages, 13 figures, accepted for publication in ApJ

We report on the identification of the lens responsible for microlensing event MACHO-LMC-20. As part of a \textit{Spitzer}/IRAC program conducting mid-infrared follow-up of the MACHO Large Magellanic Cloud microlensing fields, we discovered a significant flux excess at the position of the source star for this event. These data, in combination with high resolution near-infrared \textit{Magellan}/PANIC data has allowed us to classify the lens as an early M dwarf in the thick disk of the Milky Way, at a distance of $\sim 2$ kpc. This is only the second microlens to have been identified, the first also being a M dwarf star in the disk. Together, these two events are still consistent with the expected frequency of nearby stars in the Milky Way thin and thick disks acting as lenses., Comment: 6 pages, 4 figures, submitted to ApJ Letters

We are performing a uniform and unbiased, ~7x7 degrees imaging survey of the Large Magellanic Cloud (LMC), using the IRAC and MIPS instruments on board the Spitzer Space Telescope in order to survey the agents of a galaxy's evolution (SAGE), the interstellar medium (ISM) and stars in the LMC. The detection of diffuse ISM with column densities >1.2x10^21 H cm^-2 permits detailed studies of dust processes in the ISM. SAGE's point source sensitivity enables a complete census of newly formed stars with masses >3 solar masses that will determine the current star formation rate in the LMC. SAGE's detection of evolved stars with mass loss rates >1x10^-8 solar masses per year will quantify the rate at which evolved stars inject mass into the ISM of the LMC. The observing strategy includes two epochs in 2005, separated by three months, that both mitigate instrumental artifacts and constrain source variability. The SAGE data are non-proprietary. The data processing includes IRAC and MIPS pipelines and a database for mining the point source catalogs, which will be released to the community in support of Spitzer proposal cycles 4 and 5. We present initial results on the epoch 1 data with a special focus on the N79 and N83 region. The SAGE epoch 1 point source catalog has ~4 million sources. The point source counts are highest for the IRAC 3.6 microns band and decrease dramatically towards longer wavelengths consistent with the fact that stars dominate the point source catalogs and that the dusty objects, e.g. young stellar objects and dusty evolved stars that detected at the longer wavelengths, are rare in comparison. We outline a strategy for identifying foreground MW stars, that may comprise as much as 18% of the source list, and background galaxies, that may comprise ~12% of the source list., Comment: Accepted by the Astronomical Journal

Spitzer mid-infrared images of the dusty warped disk in the galaxy Centaurus A show a parallelogram-shaped structure. We successfully model the observed mid-infrared morphology by integrating the light from an emitting, thin, and warped disk, similar to that inferred from previous kinematic studies. The models with the best match to the morphology lack dust emission within the inner 0.1 to 0.8 kpc, suggesting that energetic processes near the nucleus have disturbed the inner molecular disk, creating a gap in the molecular gas distribution., Comment: submitted to ApJ

Spitzer Space Telescope mid-infrared images of the radio galaxy Centaurus A reveal a shell-like, bipolar, structure 500 pc to the north and south of the nucleus. This shell is seen in 5.8, 8.0 and 24 micron broad-band images. Such a remarkable shell has not been previously detected in a radio galaxy and is the first extragalactic nuclear shell detected at mid-infrared wavelengths. We estimate that the shell is a few million years old and has a mass of order million solar masses. A conservative estimate for the mechanical energy in the wind driven bubble is 10^53 erg. The shell could have created by a small few thousand solar mass nuclear burst of star formation. Alternatively, the bolometric luminosity of the active nucleus is sufficiently large that it could power the shell. Constraints on the shell's velocity are lacking. However, if the shell is moving at 1000 km/s then the required mechanical energy would be 100 times larger., Comment: submitted to ApJ Letters

The Spitzer Space Telescope, born as the Shuttle Infrared Telescope Facility (SIRTF) and later the Space Infrared Telescope Facility (still SIRTF), was under discussion and development within NASA and the scientific community for more than 30 years prior to its launch in 2003. This brief history chronicles a few of the highlights and the lowlights of those 30 years from the authors personal perspective. A much more comprehensive history of SIRTF/Spitzer has been written by George Rieke (2006)., Comment: 12 pages, 3 figures; to appear in proceedings of "The Spitzer Space Telescope: New Views of the Cosmos"

We have carried out photometry of the microlensing event MACHO-LMC-5 with Spitzer's IRAC ten years after the magnification of the LMC source star was recorded. This event is unique in the annals of gravitational microlensing: the lensing star itself has been observed using HST (once with WFPC2 and twice with ACS/HRC). Since the separation between the source and lens at the epoch of the Spitzer observations was $\sim0.24''$, the two stars cannot be resolved in the Spitzer images. However, the IRAC photometry clearly establishes that the lens is a M5 dwarf star from its infrared excess, which in turn yields a mass of $\sim0.2 M_{\odot}$. This demonstrates the potential of Spitzer to detect the lenses in other gravitational microlensing events., Comment: Accepted for publication, ApJS Spitzer Special Issue

We present results of a Chandra observation of a field in NGC 2264. The observations were taken with the ACIS-I camera with an exposure time of 48.1 ks. We present a catalog of 263 sources, which includes X-ray luminosity, optical and infrared photometry and X-ray variability information. We found 41 variable sources, 14 of which have a flare-like light curve, and 2 of which have a pattern of a steady increase or decrease over a 10 hour period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being pre-main sequence stars with ages younger than 3 Myr., Comment: 36 pages, 13 figures, AJ in press (May 2004)

We present ISO-PHOT spectra of the regions 2.5-4.9um and 5.8-11.6um for a sample of 45 disk galaxies from the U.S. ISO Key Project on Normal Galaxies. The spectra can be decomposed into three spectral components: (1) continuum emission from stellar photospheres, which dominates the near-infrared (2.5- 4.9um; NIR) spectral region; (2) a weak NIR excess continuum, which has a color temperature of ~ 1000K, carries a luminosity of a few percent of the total far-infrared luminosity L(FIR), and most likely arises from the ISM; and (3) the well-known broad emission features at 6.2, 7.7, 8.6 and 11.3 um, which are generally attributed to aromatic carbon particles. These aromatic features in emission (AFEs) dominate the mid-infrared (5.8-11.6 um; MIR) part of the spectrum, and resemble the so-called Type-A spectra observed in many non-stellar sources and the diffuse ISM in our own Galaxy. The relative strengths of the AFEs vary by 15-25% among the galaxies. However, little correlation is seen between these variations and either IRAS 60um-to-100um flux density ratio R(60/100) or the FIR-to-blue luminosity ratio L(FIR)/L(B), suggesting that the observed variations are not a direct consequence of the radiation field differences among the galaxies. We demonstrate that the NIR excess continuum and AFE emission are correlated, suggesting that they are produced by similar mechanisms and similar (or the same) material. On the other hand, as the current star-formation activity increases, the overall strengths of the AFEs and the NIR excess continuum drop significantly with respect to that of the far-infrared emission from large dust grains. This is likely a consequence of the preferential destruction in intense radiation fields of the small carriers responsible for the NIR/AFE emission., Comment: With 8 tables and 12 figures; to appear in the Astrophysical Journal

We have obtained CO(1-0) observations for a sample of 37 interacting galaxy systems, chosen from a parent sample of optically-selected interacting galaxies. The sample observed here spans a large range of interaction strengths and star formation rates (SFR). Using the standard CO-to-H2 conversion factor we find that the interacting galaxies are, on average, marginally more rich in molecular gas than a comparison sample of isolated spiral galaxies, having mean H2/LB and H2/HI ratios 20-40% higher than isolated spirals. The interacting galaxies also have a mean LIR/MH2 ratio that is a factor of ~1.3 higher than the isolated galaxies. There is a strong correlation between relative H2 content and SFRs, indicating that the level of interaction-induced star formation activity is very dependent upon the the available gas supply. Some galaxies, however, have moderate amounts of H2 but much lower than normal SFRs. Therefore molecular gas is a necessary, but not sufficient, prerequisite for star formation. There is also a strong correlation between interaction strength and both SFR and relative H2 content. If the increase in H2 content is real, there must be a substantial conversion of HI to H2 gas taking place in the strongest interacting systems. At least some portion of this apparent increase, however, could be due to non-standard CO-to-H2 conversion factors. A reduction in the conversion factor by amounts consistent with that applicable to ultraluminous infrared galaxies would completely account for the systematic increase in derived H2 content as a function of interaction strength. Such a change could not, however, account for the total range of relative H2 content as a function of SFR. Therefore the correlation between molecular gas content and star formation rate must be real., Comment: 36 pages, 13 figures, 2 landscape tables, uses emulateapj style, submitted to ApJ

We present imaging polarimetry of the extremely luminous, redshift 2.3 IRAS source FSC10214+4724. The observations were obtained with HST's Faint Object Camera in the F437M filter, which is free of strong emission lines. The 0.7 arcsec long arc is unresolved to 0.04 arcsec FWHM in the transverse direction, and has an integrated polarization of 28 +/- 3 percent, in good agreement with ground-based observations. The polarization position angle varies along the arc by up to 35 deg. The overall position angle is 62 +/- 3 deg east of north. No counterimage is detected to B = 27.5 mag ($3\sigma$), giving an observed arc to counterimage flux ratio greater than 250, considerably greater than the flux ratio of 100 measured previously in the I-band. This implies that the configuration of the object in the source plane at the B-band is different from that at I-band, and/or that the lensing galaxy is dusty., Comment: 17 pages, 3 figures. Accepted for publication in Astronomical Journal, February 1999