The XMM-Newton Ω\Omega Project

The abundance of high-redshift galaxy clusters depends sensitively on the matter density \OmM and, to a lesser extent, on the cosmological constant $\Lambda$. Measurements of this abundance therefore constrain these fundamental cosmological parameters, and in a manner independent and complementary to other methods, such as observations of the cosmic microwave background and distance measurements. Cluster abundance is best measured by the X-ray temperature function, as opposed to luminosity, because temperature and mass are tightly correlated, as demonstrated by numerical simulations. Taking advantage of the sensitivity of XMM-Newton, our Guaranteed Time program aims at measuring the temperature of the highest redshift (z>0.4) SHARC clusters, with the ultimate goal of constraining both \OmM and $\Lambda$.Comment: To appear in the Proceedings of the XXI Moriond Conference: Galaxy Clusters and the High Redshift Universe Observed in X-rays, edited by D. Neumann, F. Durret, & J. Tran Thanh Va

Sequential and Spontaneous Star Formation Around the Mid-Infrared Halo HII Region KR 140

We use 2MASS and MSX infrared observations, along with new molecular line (CO) observations, to examine the distribution of young stellar objects (YSOs) in the molecular cloud surrounding the halo HII region KR 140 in order to determine if the ongoing star-formation activity in this region is dominated by sequential star formation within the photodissociation region (PDR) surrounding the HII region. We find that KR 140 has an extensive population of YSOs that have spontaneously formed due to processes not related to the expansion of the HII region. Much of the YSO population in the molecular cloud is concentrated along a dense filamentary molecular structure, traced by C18O, that has not been erased by the formation of the exciting O star. Some of the previously observed submillimetre clumps surrounding the HII region are shown to be sites of recent intermediate and low-mass star formation while other massive starless clumps clearly associated with the PDR may be the next sites of sequential star formation.Comment: Accepted for publication in MNRAS, 8 pages, 10 figure

Submillimeter mapping and analysis of cold dust condensations in the Orion M42 star forming complex

We present here the continuum submillimeter maps of the molecular cloud around the M42 Nebula in the Orion region. These have been obtained in four wavelength bands (200, 260, 360 and 580 microns) with the ProNaOS two meter balloon-borne telescope. The area covered is 7 parsecs wide (50 arcmin at a distance of 470 pc) with a spatial resolution of about 0.4 parsec. Thanks to the high sensitivity to faint surface brightness gradients, we have found several cold condensations with temperatures ranging from 12 to 17 K, within 3 parsecs of the dense ridge. The statistical analysis of the temperature and spectral index spatial distribution shows an evidence of an inverse correlation between these two parameters. Being invisible in the IRAS 100 micron survey, some cold clouds are likely to be the seeds for future star formation activity going on in the complex. We estimate their masses and we show that two of them have masses higher than their Jeans masses, and may be gravitationally unstable.Comment: 4 figures, The Astrophysical Journal, Main Journal, in pres

Role of the (Mn)superoxide dismutase of Enterococcus faecalis in the in vitro interaction with microglia

Enterococcus faecalis is a significant human pathogen worldwide and is responsible for severenosocomial and community-acquired infections. Although enterococcal meningitis is rare,mortality is considerable, reaching 21 %. Nevertheless, the pathogenetic mechanisms of thisinfection remain poorly understood, even though the ability of E. faecalis to avoid or survivephagocytic attack in vivo may be very important during the infection process. We previouslyshowed that the manganese-cofactored superoxide dismutase (MnSOD) SodA of E. faecalis wasimplicated in oxidative stress responses and, interestingly, in the survival within mouse peritonealmacrophages using an in vivo\u2013in vitro infection model. In the present study, we investigated therole of MnSOD in the interaction of E. faecalis with microglia, the brain-resident macrophages. Byusing an in vitro infection model, murine microglial cells were challenged in parallel with the wildtypestrain JH2-2 and its isogenic sodA deletion mutant. While both strains were phagocytosedby microglia efficiently and to a similar extent, the DsodA mutant was found to be significantlymore susceptible to microglial killing than JH2-2, as assessed by the antimicrobial protectionassay. In addition, a significantly higher percentage of acidic DsodA-containing phagosomes wasfound and these also underwent enhanced maturation as determined by the expression ofendolysosomal markers. In conclusion, these results show that the MnSOD of E. faecaliscontributes to survival of the bacterium in microglial cells by influencing their antimicrobial activity,and this could even be important for intracellular killing in neutrophils and thus for E. faecalispathogenesis

A Sample of Intermediate-Mass Star-Forming Regions: Making Stars at Mass Column Densities <1 g/cm^2

In an effort to understand the factors that govern the transition from low- to high-mass star formation, we identify for the first time a sample of intermediate-mass star-forming regions (IM SFRs) where stars up to - but not exceeding - 8 solar masses are being produced. We use IRAS colors and Spitzer Space Telescope mid-IR images, in conjunction with millimeter continuum and CO maps, to compile a sample of 50 IM SFRs in the inner Galaxy. These are likely to be precursors to Herbig AeBe stars and their associated clusters of low-mass stars. IM SFRs constitute embedded clusters at an early evolutionary stage akin to compact HII regions, but they lack the massive ionizing central star(s). The photodissociation regions that demarcate IM SFRs have typical diameters of ~1 pc and luminosities of ~10^4 solar luminosities, making them an order of magnitude less luminous than (ultra)compact HII regions. IM SFRs coincide with molecular clumps of mass ~10^3 solar masses which, in turn, lie within larger molecular clouds spanning the lower end of the giant molecular cloud mass range, 10^4-10^5 solar masses. The IR luminosity and associated molecular mass of IM SFRs are correlated, consistent with the known luminosity-mass relationship of compact HII regions. Peak mass column densities within IM SFRs are ~0.1-0.5 g/cm^2, a factor of several lower than ultra-compact HII regions, supporting the proposition that there is a threshold for massive star formation at ~1 g/cm^2.Comment: 61 pages, 6 tables, 20 figures. Accepted for publication in the Astronomical Journa

Submillimeter dust emission of the M17 complex measured with PRONAOS

We map a 50' x 30' area in and around the M17 molecular complex with the French submillimeter balloon-borne telescope PRONAOS, in order to better understand the thermal emission of cosmic dust and the structure of the interstellar medium. The PRONAOS-SPM instrument has an angular resolution of about 3', corresponding to a size of 2 pc at the distance of this complex, and a high sensitivity up to 0.8 MJy/sr. The observations are made in four wide submillimeter bands corresponding to effective wavelengths of 200, 260, 360 and 580 um. Using an improved map-making method for PRONAOS data, we map the M17 complex and faint condensations near the dense warm core. We derive maps of both the dust temperature and the spectral index, which vary over a wide range, from about 10 K to 100 K for the temperature and from about 1 to 2.5 for the spectral index. We show that these parameters are anticorrelated, the cold areas (10-20 K) having a spectral index around 2, whereas the warm areas have a spectral index between 1 and 1.5. We discuss possible causes of this effect, and we propose an explanation involving intrinsic variations of the grain properties. Indeed, to match the observed spectra with two dust components having a spectral index equal to 2 leads to very large and unlikely amounts of cold dust. We also give estimates of the column densities and masses of the studied clumps. Three cold clumps (14-17 K) could be gravitationally unstable.Comment: 16 pages, 4 figures, accepted June 2002 in Astronomy & Astrophysic

TURBULENCE IN MOLECULAR CLOUDS

We generate random Gaussian turbulent velocity fields with a Kolmogorov spectrum and use these to obtain synthetic line-of-sight velocity profiles. The profiles are found to be similar to line profiles observed in molecular clouds. We suggest methods for analysing measured line profiles to test whether they might arise from Gaussian Kolmogorov turbulence.Comment: accepted in ApJ, compressed postscript, figures not included. Complete preprint available at http://ucowww.ucsc.edu/~dubinski/home.html or by request to [email protected]

A multiwavelength study of Galactic HII region Sh2-294

We present the observational results of Galactic HII region S294, using optical photometry, narrow-band imaging and radio continuum mapping at 1280 MHz, together with archival data from 2MASS, MSX and IRAS surveys. The stellar surface density profile indicates that the radius of the cluster associated with the S294 region is ~ 2.3 arcmin. We found an anomalous reddening law for the dust inside the cluster region and the ratio of total-to-selective extinction is found to be 3.8+-0.1. We estimate the minimum reddening E (B-V) = 1.35 mag and distance of 4.8+-0.2 kpc to the region from optical CC and CM diagrams. We identified the ionizing source of the HII region, and spectral type estimates are consistent with a star of spectral type ~ B0 V. The 2MASS JHKs images reveal a partially embedded cluster associated with the ionizing source along with a small cluster towards the eastern border of S294. The ionization front seen along the direction of small cluster in radio continuum and Halpha images, might be due to the interaction of ionizing sources with the nearby molecular cloud. We found an arc shaped diffuse molecular hydrogen emission at 2.12 micron and a half ring of MSX dust emission which surrounds the ionized gas in the direction of the ionization front. Self consistent radiative transfer model of mid- to far-infrared continuum emission detected near small cluster is in good agreement with the observed spectral energy distribution of a B1.5 ZAMS star. The morphological correlation between the ionised and molecular gas, along with probable time scale involved between the ionising star, evolution of HII region and small cluster, indicates that the star-formation activity observed at the border is probably triggered by the expansion of HII region.Comment: 50 pages, 21 figures: Accepted by The Astrophysical Journal; Also available at http://www.tifr.res.in/~ojha/S294.pd

The complete submillimetre spectrum of NGC 891

Submillimetre maps of NGC 891 have been obtained with the PRONAOS balloon-borne telescope and with the ISOPHOT instrument on board the ISO satellite. In this article, we also gather data from IRAS and SCUBA to present the complete submillimetre spectrum of this nearby edge-on spiral galaxy. We derive submillimetre emission profiles along the major axis. The modified blackbody fits, assuming a single dust component, lead to temperatures of 19-24 K toward the centre and 18-20 K toward the edges, with possible variations of the dust spectral index from 1.4 to 2. The two-component fits lead to a warm component temperature of 29 K all along the galaxy with a cold component at 16 K. The interstellar medium masses derived by these two methods are quite different: 4.6 x 10^9 Mo in the case of the one-component model and 12 x 10^9 Mo in the case of the two-component one. This two-component fit indicates that the cold dust to warm dust ratio is 20 to 40, the highest values being in the wings of this galaxy. Comparing to dust mass estimates, both estimations of the ISM mass are consistent with a gas to dust mass ratio of 240, which is close to the Milky Way value. Our results illustrate the importance of accurate submillimetre spectra to derive masses of the interstellar medium in galaxies.Comment: 5 pages, 2 figures, accepted May 2003 in the MNRA

Emission Features and Source Counts of Galaxies in Mid-Infrared

In this work we incorporate the newest ISO results on the mid-infrared spectral-energy-distributions (MIR SEDs) of galaxies into models for the number counts and redshift distributions of MIR surveys. A three-component model, with empirically determined MIR SED templates of (1) a cirrus/PDR component (2) a starburst component and (3) an AGN component, is developed for infrared (3--120\micron) SEDs of galaxies. The model includes a complete IRAS 25\micron selected sample of 1406 local galaxies ($z \leq 0.1$; Shupe et al. 1998a). Results based on these 1406 spectra show that the MIR emission features cause significant effects on the redshift dependence of the K-corrections for fluxes in the WIRE 25\micron band and ISOCAM 15\micron band. This in turn will affect deep counts and redshift distributions in these two bands, as shown by the predictions of two evolution models (a luminosity evolution model with $L\propto (1+z)^3$ and a density evolution model with $\rho\propto (1+z)^4$). The dips-and-bumps on curves of MIR number counts, caused by the emission features, should be useful indicators of evolution mode. The strong emission features at $\sim 6$--8\micron will help the detections of relatively high redshift ($z\sim 2$) galaxies in MIR surveys. On the other hand, determinations of the evolutionary rate based on the slope of source counts, and studies on the large scale structures using the redshift distribution of MIR sources, will have to treat the effects of the MIR emission features carefully. We have also estimated a 15\micron local luminosity function from the predicted 15\micron fluxes of the 1406 galaxies using the bivariate (15\micron vs. 25\micron luminosities) method. This luminosity function will improve our understanding of the ISOCAM 15\micron surveys.Comment: 24 pages, 14 EPS figures. Accepted by Ap