A Massive Protostar Embedded in the Scuba Core JCMT 18354-0649S

We report the discovery of an extremely red object embedded in the massive SCUBA core JCMT 18354-0649S. This object is not associated with any known radio or far-IR source, though it appears in Spitzer IRAC data obtained as part of the GLIMPSE survey. At shorter wavelengths, this embedded source exhibits an extreme color, K – L' = 6.7. At an assumed distance of 5.7 kpc, this source has a near-IR luminosity of ~1000 L_☉. Its spectral energy distribution (SED) rises sharply from 2.1 μm to 8 μm, similar to that of a Class 0 young stellar object. Theoretical modeling of the SED indicates that the central star has a mass of 6-12 M_☉, with an optical extinction of more than 30. As both inflow and outflow motions are present in JCMT 18354-0649S, we suggest that this deeply embedded source is (1) a massive protostar in the early stages of accretion, and (2) the driving source of a massive molecular outflow evident in HCN J = 3-2 profiles observed toward this region

A Water Maser and Ammonia Survey of GLIMPSE Extended Green Objects (EGOs)

We present the results of a Nobeyama 45-m water maser and ammonia survey of all 94 northern GLIMPSE Extended Green Objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5 micron emission. We observed the ammonia (1,1), (2,2), and (3,3) inversion lines, and detect emission towards 97%, 63%, and 46% of our sample, respectively (median rms ~50 mK). The water maser detection rate is 68% (median rms ~0.11 Jy). The derived water maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on MIR properties or maser associations. Water masers and warm dense gas, as indicated by emission in the higher-excitation ammonia transitions, are most frequently detected towards EGOs also associated with both Class I and II methanol masers. 95% (81%) of such EGOs are detected in water (ammonia(3,3)), compared to only 33% (7%) of EGOs without either methanol maser type. As populations, EGOs associated with Class I and/or II methanol masers have significantly higher ammonia linewidths, column densities, and kinetic temperatures than EGOs undetected in methanol maser surveys. However, we find no evidence for statistically significant differences in water maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1 mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic water maser luminosity and clump number density. Water maser luminosity is weakly correlated with clump (gas) temperature and clump mass.Comment: Astrophysical Journal, accepted. Emulateapj, 24 pages including 24 figures, plus 9 tables (including full content of online-only tables

Object-X: The Brightest Mid-IR Point Source in M33

We discuss the nature of the brightest mid-IR point source (which we dub Object X) in the nearby galaxy M33. Although multi-wavelength data on this object have existed in the literature for some time, it has not previously been recognized as the most luminous mid-IR object in M33 because it is entirely unremarkable in both optical and near-IR light. In the Local Group Galaxies Survey, Object X is a faint red source visible in VRI and H-alpha but not U or B. It was easily seen at JHK_s in the 2MASS survey. It is the brightest point source in all four Spitzer IRAC bands and is also visible in the MIPS 24-micron band. Its bolometric luminosity is 5x10^5 L_sun. The source is optically variable on short time scales (tens of days) and is also slightly variable in the mid-IR, indicating that it is a star. Archival photographic plates (from 1949 and 1991) show no optical source, so the star has been obscured for at least half a century. Its properties are similar to those of the Galactic OH/IR star IRC+10420 which has a complex dusty circumstellar structure resulting from episodic low velocity mass ejections. We propose that Object X is a M>30 M_sun evolved star obscured in its own dust ejected during episodic mass loss events over at least half a century. It may emerge from its current ultra-short evolutionary phase as a hotter post-RSG star analogous to M33 Var A. The existence and rarity of such objects can be an important probe of a very brief yet eventful stellar evolutionary phase.Comment: 20 pages, 10 figures. Accepted for publication by Ap

The Next Generation of the Montage Image Mosaic Toolkit

The scientific computing landscape has evolved dramatically in the past few years, with new schemes for organizing and storing data that reflect the growth in size and complexity of astronomical data sets. In response to this changing landscape, we are, over the next two years, deploying the next generation of the Montage toolkit ([ascl:1010.036]). The first release (October 2015) supports multi-dimensional data sets ("data cubes"), and insertion of XMP/AVM tags that allows images to "drop-in" to the WWT. The same release offers a beta-version of web-based interactive visualization of images; this includes wrappers for visualization in Python. Subsequent releases will support HEALPix (now standard in cosmic background experiments); incorporation of Montage into package managers (which enable automated management of software builds), and support for a library that will enable Montage to be called directly from Python. This next generation toolkit will inherit the architectural benefits of the current engine - component based tools, ANSI-C portability across Unix platforms and scalability for distributed processing. With the expanded functionality under development, Montage can be viewed not simply as a mosaic engine, but as a scalable, portable toolkit for managing, organizing and processing images

Triggered Star Formation and Dust around Mid-Infrared-Identified Bubbles

We use Two Micron All Sky Survey, GLIMPSE, and MIPSGAL survey data to analyze the young stellar object (YSO) and warm dust distribution around several mid-infrared-identified bubbles. We identify YSOs using J-band to 8 um photometry and correlate their distribution relative to the PDR (as traced by diffuse 8 um emission) which we assume to be associated with and surround a HII region. We find that only 20% of the sample HII regions appear to have a significant number of YSOs associated with their PDRs, implying that triggered star formation mechanisms acting on the boundary of the expanding HII region do not dominate in this sample. We also measure the temperature of dust inside 20 HII regions using 24 um and 70 um MIPSGAL images. In eight circularly symmetric sources we analyze the temperature distribution and find shallower temperature gradients than is predicted by an analytic model. Possible explanations of this shallow temperature gradient are a radially dependent grain-size distribution and/or non-equilibrium radiative processes.Comment: 35 pages, 17 figures, accepted for publication in Ap

Star Formation in the Milky Way. The Infrared View

I present a brief review of some of the most recent and active topics of star formation process in the Milky Way using mid and far infrared observations, and motivated by the research being carried out by our science group using data gathered by the Spitzer and Herschel space telescopes. These topics include bringing together the scaling relationships found in extragalactic systems with that of the local nearby molecular clouds, the synthetic modeling of the Milky Way and estimates of its star formation rate.Comment: 12 pages, 9 figures. To apper in "Cosmic-ray induced phenomenology in star-forming environments: Proceedings of the 2nd Session of the Sant Cugat Forum of Astrophysics" (April 16-19, 2012), Olaf Reimer and Diego F. Torres (eds.

Sky maps without anisotropies in the cosmic microwave background are a better fit to WMAP's uncalibrated time ordered data than the official sky maps

The purpose of this reanalysis of the WMAP uncalibrated time ordered data (TOD) was two fold. The first was to reassess the reliability of the detection of the anisotropies in the official WMAP sky maps of the cosmic microwave background (CMB). The second was to assess the performance of a proposed criterion in avoiding systematic error in detecting a signal of interest. The criterion was implemented by testing the null hypothesis that the uncalibrated TOD was consistent with no anisotropies when WMAP's hourly calibration parameters were allowed to vary. It was shown independently for all 20 WMAP channels that sky maps with no anisotropies were a better fit to the TOD than those from the official analysis. The recently launched Planck satellite should help sort out this perplexing result.Comment: 11 pages with 1 figure and 2 tables. Extensively rewritten to explain the research bette

Triggered star formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38

We have investigated the young stellar population in and around SFO 38, one of the massive globules located in the northern part of the Galactic HII region IC 1396, using the Spitzer IRAC and MIPS observations (3.6 to 24 micron) and followed up with ground based optical photometric and spectroscopic observations. Based on the IRAC and MIPS colors and H-alpha emission we identify ~45 Young Stellar Objects (Classes 0/I/II) and 13 probable Pre Main Sequence candidates. We derive the spectral types (mostly K- and M-type stars), effective temperatures and individual extinction of the relatively bright and optically visible Class II objects. Based on optical photometry and theoretical isochrones, we estimate the spread in stellar ages to be between 1--8 Myr with a median age of 3 Myr and a mass distribution of 0.3--2.2 Msun with a median value around 0.5 Msun. Using the width of the H-alpha emission line measured at 10% peak intensity, we derive the mass accretion rates of individual objects to be between 10^{-10} to 10^{-8} Msun/yr. From the continuum-subtracted H-alpha line image, we find that the H-alpha emission of the globule is not spatially symmetric with respect to the O type ionizing star HD 206267. We clearly detect an enhanced concentration of YSOs closer to the southern rim of SFO~38 and identify an evolutionary sequence of YSOs from the rim to the dense core of the cloud, with most of the Class II objects located at the bright rim. The YSOs appear to be aligned along two different directions towards the O6.5V type star HD 206267 and the B0V type star HD 206773. This is consistent with the Radiation Driven Implosion (RDI) model for triggered star formation. (Abridged)Comment: Accepted for publication in Ap

The RMS Survey: The Bolometric Fluxes and Luminosity Distributions of Young Massive Stars

Context: The Red MSX Source (RMS) survey is returning a large sample of massive young stellar objects (MYSOs) and ultra-compact (UC) \HII{} regions using follow-up observations of colour-selected candidates from the MSX point source catalogue. Aims: To obtain the bolometric fluxes and, using kinematic distance information, the luminosities for young RMS sources with far-infrared fluxes. Methods: We use a model spectral energy distribution (SED) fitter to obtain the bolometric flux for our sources, given flux data from our work and the literature. The inputs to the model fitter were optimised by a series of investigations designed to reveal the effect varying these inputs had on the resulting bolometric flux. Kinematic distances derived from molecular line observations were then used to calculate the luminosity of each source. Results: Bolometric fluxes are obtained for 1173 young RMS sources, of which 1069 have uniquely constrained kinematic distances and good SED fits. A comparison of the bolometric fluxes obtained using SED fitting with trapezium rule integration and two component greybody fits was also undertaken, and showed that both produce considerable scatter compared to the method used here. Conclusions: The bolometric flux results allowed us to obtain the luminosity distributions of YSOs and UC\HII{} regions in the RMS sample, which we find to be different. We also find that there are few MYSOs with L $\geq$ 10$^{5}$\lsol{}, despite finding many MYSOs with 10$^{4}$\lsol{} $\geq$ L $\geq$ 10$^{5}$\lsol{}.Comment: 12 pages, 12 figures, 3 tables, accepted to A&A. The full versions of tables 1 and 2 will be available via the CDS upon publicatio

Galaxy Formation with local photoionisation feedback I. Methods

We present a first study of the effect of local photoionising radiation on gas cooling in smoothed particle hydrodynamics simulations of galaxy formation. We explore the combined effect of ionising radiation from young and old stellar populations. The method computes the effect of multiple radiative sources using the same tree algorithm used for gravity, so it is computationally efficient and well resolved. The method foregoes calculating absorption and scattering in favour of a constant escape fraction for young stars to keep the calculation efficient enough to simulate the entire evolution of a galaxy in a cosmological context to the present day. This allows us to quantify the effect of the local photoionisation feedback through the whole history of a galaxy`s formation. The simulation of a Milky Way like galaxy using the local photoionisation model forms ~ 40 % less stars than a simulation that only includes a standard uniform background UV field. The local photoionisation model decreases star formation by increasing the cooling time of the gas in the halo and increasing the equilibrium temperature of dense gas in the disc. Coupling the local radiation field to gas cooling from the halo provides a preventive feedback mechanism which keeps the central disc light and produces slowly rising rotation curves without resorting to extreme feedback mechanisms. These preliminary results indicate that the effect of local photoionising sources is significant and should not be ignored in models of galaxy formation.Comment: Accepted for Publication in MNRAS, 13 pages, 13 figure