Globular cluster stars evolving off the main sequence are known to lose mass, and it is expected that some of the lost material should remain within the cluster as an intracluster medium (ICM). Most attempts to detect such an ICM have been unsuccessful. The Multiband Imaging Photometer for Spitzer on the Spitzer Space Telescope was used to observe eight Galactic globular clusters in an attempt to detect the thermal emission from ICM dust. Most clusters do not have significant detections at 70 microns; one cluster, NGC 6341, has tentative evidence for the presence of dust, but 90 micron observations do not confirm the detection. Individual 70 micron point sources which appear in several of the cluster images are likely to be background galaxies. The inferred dust mass and upper limits are < 4e-4 solar masses, well below expectations for cluster dust production from mass loss in red and asymptotic giant branch stars. This implies that either globular cluster dust production is less efficient, or that ICM removal or dust destruction is more efficient, than previously believed. We explore several possibilities for ICM removal and conclude that present data do not yet permit us to distinguish between them.
Spitzer IRAC mid-infrared photometry is presented for the globular cluster (GC) systems of the NGC 5128 ("Centaurus A") and NGC 4594 ("Sombrero") galaxies. Existing optical photometric and spectroscopic are combined with this new data in a comprehensive optical to mid-IR colour catalogue of 260 GCs. Empirical colour-metallicity relationships are derived for all optical to mid-IR colour combinations. These colours prove to be very effective quantities to test the photometric predictions of simple stellar population (SSP) models. In general, four SSP models show larger discrepancies between each…
We are examining mass loss from globular clusters giant stars, focussing on metallicity dependance. We present three sets of observations: TIMMI-2 mid-IR spectra of 47 Tuc, UVES high-resolution optical spectra of several clusters, and an infrared atlas of omega Cen using the Spitzer Space Telescope.
We have identified four circumstellar disks with a deficit of dust emission from their inner 15-50 AU. All four stars have F-G spectral type, and were uncovered as part of the Spitzer Space Telescope ``Cores to Disks'' Legacy Program Infrared Spectrograph (IRS) first look survey of ~100 pre-main sequence stars. Modeling of the spectral energy distributions indicates a reduction in dust density by factors of 100-1000 from disk radii between ~0.4 and 15-50 AU, but with massive gas-rich disks at larger radii. This large contrast between the inner and outer disk has led us to use the term `cold di…
We present observations at 3.6, 4.5, 5.8, 8, 24, 70 & 160um of NGC 205, the dwarf elliptical companion of M31, obtained with the Spitzer Space Telescope. The point sources subtracted images at 8 and 24um display a complex and fragmented infrared emission coming from both very small dust particles and larger grains. The extended dust emission is spatially concentrated in three main emission regions, seen at all wavelengths from 8 to 160um. These regions lie approximately along NGC 205's semi-major axis and range from ~100 to 300 pc in size. Based on our mid-to-far infrared flux density measurem…
We analyze the metallicity distributions of globular clusters belonging to 28 early-type galaxies in the survey of Kundu & Whitmore (2001). A Monte Carlo algorithm which simulates the chemical evolution of galaxies that grow hierarchically via dissipationless mergers is used to determine the most probable protogalactic mass function for each galaxy. Contrary to the claims of Kundu & Whitmore, we find that the observed metallicity distributions are in close agreement with the predictions of such hierarchical formation models. The mass spectrum of protogalactic fragments for the galaxies in our …
Observations at 70 microns with the Spitzer Space Telescope have detected several stellar systems within 65 pc of the Sun. Of 18 presumably young systems detected in this study, as many as 15 have 70-micron emission in excess of that expected from their stellar photospheres. Five of the systems with excesses are members of the Tucanae Association. The 70-micron excesses range from a factor of ~2 to nearly 30 times the expected photospheric emission from these stars. In contrast to the 70-micron properties of these systems, there is evidence for an emission excess at 24 microns for only HD 3003…
Spitzer IRAC and MIPS images of the Trifid Nebula (M20) reveal its spectacular appearance in infrared light, highlighting the nebula's special evolutionary stage. The images feature recently-formed massive protostars and numerous young stellar objects, and a single O star that illuminates the surrounding molecular cloud from which it formed, and unveil large-scale, filamentary dark clouds. The hot dust grains show contrasting infrared colors in shells, arcs, bow-shocks and dark cores. Multiple protostars are detected in the infrared, within the cold dust cores of TC3 and TC4, which were previo…
We observed 36 evolved stars in the Small Magellanic Cloud (SMC) using the low-resolution mode of the Infrared Spectrograph (IRS) on the Spitzer Space Telescope. Two of these stars, MSX SMC 014 and 155, have nearly featureless spectral energy distributions over the IRS wavelength range (5.2-35 um) and F_nu peaking at ~8-9 um. The data can be fit by sets of amorphous carbon shells or by single 600-700 K blackbodies. The most similar spectra found in extant spectral databases are of R CrB, although the spectral structure seen in R CrB and similar stars is much weaker or absent in the SMC sources…
We investigate what may be the origin of the presently observed spatial distribution of the mass of the Galactic Old Halo globular cluster system. We propose its radial mass density profile to be a relic of the distribution of the cold baryonic material in the protoGalaxy. Assuming that this one arises from the profile of the whole protoGalaxy minus the contribution of the dark matter (and a small contribution of the hot gas by which the protoglobular clouds were bound), we show that the mass distributions around the Galactic centre of this cold gas and of the Old Halo agree satisfactorily. In…
We present Spitzer Space Telescope IRAC and MIPS observations of the galactic globular cluster M15 (NGC 7078), one of the most metal-poor clusters with a [Fe/H] = -2.4. Our Spitzer images reveal a population of dusty red giants near the cluster center, a previously detected planetary nebula (PN) designated K648, and a possible detection of the intra-cluster medium (ICM) arising from mass loss episodes from the evolved stellar population. Our analysis suggests 9 (+/-2) x 10^-4 solar masses of dust is present in the core of M15, and this material has accumulated over a period of approximately 10…
I review the literature's census of the cold gas in clusters of galaxies. Cold gas here is defined as the gas that is cooler than X-ray emitting temperatures (~10^7 K) and is not in stars. I present new Spitzer IRAC and MIPS observations of Abell 2597 (PI: Sparks) that reveal significant amounts of warm dust and star formation at the level of 5 solar masses per year. This rate is inconsistent with the mass cooling rate of 20 +/- 5 solar masses per year inferred from a FUSE [OVI] detection.
This paper presents a sensitive and comprehensive IRAC 3-8 $μ$m photometric survey of white dwarfs for companions in the planetary mass regime with temperatures cooler than the known T dwarfs. The search focuses on descendents of intermediate mass stars with $M\ga3$ $M_{\odot}$ whose inner, few hundred AU regions cannot be probed effectively for massive planets and brown dwarfs by any alternative existing method. Furthermore, examination for mid-infrared excess explores an extensive range of orbital semimajor axes, including the intermediate 5-50 AU range poorly covered and incompletely access…
Using the Spitzer IRAC camera we have obtained mid-IR photometry of the red giant branch stars in the Galactic globular cluster 47 Tuc. About 100 stars show an excess of mid-infrared light above that expected from their photospheric emission. This is plausibly due to dust formation in mass flowing from these stars. This mass loss extends down to the level of the horizontal branch and increases with luminosity. The mass loss is episodic, occurring in only a fraction of stars at a given luminosity. Using a simple model and our observations we derive mass loss rates for these stars. Finally, we o…
We present results of fully self-consistent N-body simulations of the motion of four globular clusters moving in the inner region of their parent galaxy. With regard to previous simplified simulations, we confirm merging and formation of an almost steady nuclear cluster, in a slightly shorter time. The projected surface density profile shows strong similarity to that of resolved galactic nuclei. This similarity reflects also in the velocity dispersion profile which exhibits a central colder component as observed in many nucleated galaxies.
We summarize the progress to date of our Legacy Science Program entitled "The Formation and Evolution of Planetary Systems" (FEPS) based on observations obtained with the Spitzer Space Telescope during its first year of operation. In addition to results obtained from our ground-based preparatory program and our early validation program, we describe new results from a survey for near-infrared excess emission from the youngest stars in our sample as well as a search for cold debris disks around sun-like stars. We discuss the implications of our findings with respect to current understanding of t…
Recent Spitzer observations of the globular cluster M15 detected dust associated with its intracluster medium. Surprisingly, these observations imply that the dust must be very short-lived compared to the time since the last Galactic plane crossing of the cluster.Here we propose a simple mechanism to explain this short lifetime. We argue that the kinetic energy of the material ejected during a stellar collision may be sufficient to remove the gas and dust entirely from a cluster, or to remove the gas as a wind, in addition to partially destroying the dust. By calculating the rate of stellar co…
We present new far infrared maps of the Small Magellanic Cloud (SMC) at 24, 70, and 160 microns obtained as part of the Spitzer Survey of the Small Magellanic Cloud (S3MC,Bolatto et al. 2006). These maps cover most of the active star formation in the SMC Bar and the more quiescent Wing. We combine our maps with literature data to derive the dust surface density across the SMC. We find a total dust mass of Mdust = 3 10^5 Msun, implying a dust-to-hydrogen ratio over the region studied of log D/H = -2.86, or 1-to-700, which includes H_2. Assuming the dust to trace the total gas column, we derive …
Recent discoveries from red optical proper motion and wide-field near-infrared surveys have uncovered a new population of ultracool subdwarfs, metal-poor stars and brown dwarfs extending into the late-type M, L and possibly T spectral classes. These objects are among the first low-mass stars and brown dwarfs formed in the Galaxy, and are valuable tracers of metallicity effects in low-temperature atmospheres. Like solar metallicity late-type dwarfs, ultracool subdwarfs emit the majority of their emergent flux at infrared wavelengths. Here I discuss how Spitzer observations will contribute to th…
Various galaxy properties are not continuous over a large range in mass, but rather reveal a remarkable transition or `bimodality' at a stellar mass of 3 x 10^{10} Mo. These properties include colors, stellar populations, Xray emission and mass-to-light ratios. This behavior has been interpreted as the transition from hot to cold flows by Dekel & Birnboim (2005). Here we explore whether globular cluster (GC) systems also reveal a bimodal nature with regard to this critical mass scale. Globular clusters probe star formation at early epochs in the Universe and survive subsequent galaxy mergers a…
Tidal disruption of dark matter halos around proto-globular clusters in a halo of a small galaxy is studied in the context of the hierarchical clustering scenario by using semi-cosmological N-body/SPH simulations assuming the standard cold dark matter model ($Ω_0 = 1$). Our analysis on formation and evolution of the galaxy and its substructures archives until $z = 2.0$. In such a high-redshift universe, the Einstein-de Sitter universe is still a good approximation for a recently favored $Λ$-dominated universe, and then our results does not depend on the choice of cosmology. In order to resolve…
We present results from Chandra X-ray and Spitzer mid-infrared observations of the interacting galaxy pair NGC6872/IC4970 in the Pavo galaxy group and show that the smaller companion galaxy IC4970 hosts a highly obscured active galactic nucleus (AGN). The 0.5-10 keV X-ray luminosity of the nucleus is variable, increasing by a factor 2.9 to 1.7 x 10^{42} erg/s (bright state) on ~100 ks timescales. The X-ray spectrum of the is heavily absorbed (N_H = 3 x 10^{23} cm^{-2}) for power law models with Gamma = 1.5-2.0 and shows a clear 6.4 keV Fe Kalpha line with equivalent width of 144-195 eV. Limits…
We present 3.6 - 160 micron infrared images of Kepler's supernova remnant (SN1604) obtained with the IRAC and MIPS instruments on the Spitzer Space Telescope. We also present MIPS SED low resolution spectra in the 55 - 95 micron region. The observed emission in the MIPS 24 micron band shows the entire shell. Emission in the MIPS 70 micron and IRAC 8 micron bands is seen only from the brightest regions of 24 micron emission, which also correspond to the regions seen in optical Halpha images. Shorter wavelength IRAC images are increasingly dominated by stars, although faint filaments are discern…
Cold dark matter hierarchical clustering (CDMHC) cosmology based on the Jeans 1902 criterion for gravitational instability gives predictions about the early universe contrary to fluid mechanics and observations. Jeans neglected viscosity, diffusivity, and turbulence: factors that determine gravitational structure formation and contradict small structures (CDM halos) forming from non-baryonic dark matter particle candidates. From hydro-gravitational-dynamics (HGD) cosmology, viscous-gravitational fragmentation produced supercluster (10^46 kg), cluster, and galaxy-mass (10^42 kg) clouds in the p…
We present a model of globular cluster self-enrichment. In the protogalaxy, cold and dense clouds embedded in the hot protogalactic medium are assumed to be the progenitors of galactic halo globular clusters. The massive stars of a first generation of metal-free stars, born in the central areas of the proto-globular cluster clouds, explode as Type II supernovae. The associated blast waves trigger the expansion of a supershell, sweeping all the material of the cloud, and the heavy elements released by these massive stars enrich the supershell. A second generation of stars is born in these compr…
We discuss infrared Spitzer observations of early type galaxies in the SAURON sample at 24, 60 and 170 microns. When compared with 2MASS Ks band luminosities, lenticular (S0) galaxies exhibit a much wider range of mid to far-infrared luminosities then elliptical (E) galaxies. Mid and far-infrared emission from E galaxies is a combination of circumstellar or interstellar emission from local mass-losing red giant stars, dust buoyantly transported from the galactic cores into distant hot interstellar gas and dust accreted from the environment. The source of mid and far-IR emission in S0 galaxies …
We present Spitzer IRAC (3.6, 4.5, 5.8, 8.0 um) and MIPS (24 um) observations of the SCUBA submillimeter sources and uJy VLA radio sources in a 5'x5' area in the Lockman Hole East region. Out of the ~40 SCUBA/VLA sources in the field, Spitzer counterparts were detected for nearly all except for the few low-weight SCUBA detections. We show that the majority (80-90%) of the detected sources are cold (i.e., starburst-like) infrared-luminous galaxies (L_{IR} > 10^{11} Lsun) at redshift 0.5<z<3.5, whose star-formation rate density (SFRD) is comparable to that of the optically-selected star-forming …
Many early-type galaxies are detected at 24 to 160 micron but the emission is usually dominated by an AGN or heating from the evolved stellar population. Here we present MIPS observations of a sample of elliptical and lenticular galaxies which are rich in cold molecular gas, and we investigate how much of the MIR to FIR emission could be due to star formation activity. The 24 micron images show a rich variety of structures, including nuclear point sources, rings, disks, and smooth extended emission, and comparisons to matched-resolution CO and radio continuum images suggest that the bulk of th…
We examine various physical processes associated with the formation of globular clusters by using the three-dimensional Smoothed Particle Hydrodynamics (SPH) code. Our code includes radiative cooling of gases, star formation, energy feedback from stars including stellar winds and supernovae, and chemical enrichment by stars. We assume that, in the collapsing galaxy, isothermal cold clouds form through thermal condensations and become proto-globular clouds. We calculate the size of proto-globular clouds by solving the linearized equations for perturbation. We compute the evolution of the inner …
We present a Spitzer Space Telescope imaging survey of the most massive Galactic globular cluster, omega Centauri, and investigate stellar mass loss at low metallicity and the intracluster medium (ICM). The survey covers approximately 3.2x the cluster half-mass radius at 3.6, 4.5, 5.8, 8, and 24 microns, resulting in a catalog of over 40,000 point-sources in the cluster. Approximately 140 cluster members ranging 1.5 dex in metallicity show a red excess at 24 microns, indicative of circumstellar dust. If all of the dusty sources are experiencing mass loss, the cumulative rate of loss is estimat…
We present a Spitzer based census of the IC 348 nebula and embedded star cluster. Our Spitzer census supplemented by ground based spectra has added 42 class II T-Tauri sources to the cluster membership and identified ~20 class 0/I protostars. The population of IC 348 likely exceeds 400 sources after accounting statistically for unidentified diskless members. Our Spitzer census of IC 348 reveals a population of protostars that is anti-correlated spatially with the T-Tauri members, which comprise the centrally condensed cluster around a B star. The protostars are instead found mostly at the clus…
High resolution spectra of 110 selected red giant stars in the globular cluster M15 (NGC 7078) were obtained with Hectochelle at the MMT telescope in 2005 May, 2006 May, and 2006 October. Echelle orders containing Halpha and Ca H & K are used to identify emission and line asymmetries characterizing motions in the extended atmospheres. Emission in Halpha is detected to a luminosity of log (L/L_sun)=2.36, in this very metal deficient cluster, comparable to other studies, suggesting that appearance of emission wings is independent of stellar metallicity. The faintest stars showing Halpha emission…
All galaxies are thought to reside within large halos of dark matter, whose properties can only be determined from indirect observations. The formation and assembly of galaxies is determined from the interplay between these dark matter halos and the baryonic matter they host. Although statistical relations can be used to approximate how massive a galaxy's halo is, very few individual galaxies have direct measurements of their halo masses. We present a method to directly estimate the total mass of a galaxy's dark halo using its system of globular clusters. The link between globular cluster syst…
We show that there is a subsystem of the M31 globular clusters with THIN DISK kinematics. These clusters span the entire metallicity range of the M31 globular cluster system, in contrast to the (thick) disk globulars in the Milky Way which are predominantly metal-rich. Disk globular clusters are found across the entire disk of M31 and form around 40% of the clusters projected on its disk. The existence of such a disk system suggests that there was a relatively large thin disk in place very early in M31's history. Accurate measures of the ages of these clusters will constrain the epoch of disk …
We argue that any violent galactic winds following early epoch of star bursts would significantly weaken the potentials of galaxies, and leave lasting signatures such as a lowered dark halo density and preferentially radial/escaping orbits for halo tracers such as globular clusters. A galaxy is disintegrated if more than half of its dynamical mass is blown off. The presence of dense halos in galaxies and the absence of intergalactic/escaping globulars should imply an upper limit on the amount of baryons lost in galactic winds around 4% of the total mass of the galaxy. This translates to limits…
The magnetic cataclysmic variable AE Aquarii hosts a rapidly rotating white dwarf which is thought to expel most of the material streaming onto it. Observations of AE Aqr have been obtained in the wavelength range of 5 - 70 microns with the IRS, IRAC, and MIPS instruments on board the Spitzer Space Telescope. The spectral energy distribution reveals a significant excess above the K4V spectrum of the donor star with the flux increasing with wavelength above 12.5 microns. Superposed on the energy distribution are several hydrogen emission lines, identified as Pf alpha and Hu alpha, beta, gamma. …
Many past attempts to kill MOND have only strengthened the theory. Better data on galaxy velocity curves clearly favor MOND (without fine-tuning) over cold dark matter. The usual critism on the incompleteness of classical MOND has spurred a Modified Relativity (MR) by Bekenstein. After outlining cosmology and lensing in MOND, we review MOND on small scales. We point out some potential problems of MOND in two-body relaxation and tidal truncation. We argue that the tidal field in any MOND-like gravity theory predicts that the Roche lobe sizes of a binary system are simply proportional to the bin…
We present photometric and spectroscopic data of the interacting starburst galaxy NGC 6052 obtained with the Spitzer Space Telescope. The mid-infrared (MIR) spectra of the three brightest spatially resolved regions in the galaxy are remarkably similar and are consistent with dust emission from young nearly coeval stellar populations. Analysis of the brightest infrared region of the system, which contributes ~18.5 % of the total 16\micron flux, indicates that unlike similar off-nuclear infrared-bright regions found in Arp 299 or NGC 4038/9, its MIR spectrum is inconsistent with an enshrouded ho…
We present MAMBO 1.2mm observations of 40 extragalactic sources from the Spitzer First Look Survey that are bright in the mid-infrared (S_24um>1mJy) but optically obscured (log_10 (nu F_nu (24um))/(nu F_nu (0.7um))>1). We use these observations to search for cold dust emission, probing the similarity of their spectral energy distributions to star forming infrared galaxies or obscured AGN. The sample as a whole is well detected at mean S_1.2mm=0.74+-0.09mJy and S_1.2mm/S_24um=0.15+-0.03. Seven (three) of the sources are individually detected at >3sigma (>5sigma) levels. Mean millimeter fluxes a…
Models for the formation and growth of structure in a cold dark matter dominated universe predict that galaxy halos should contain significant substructure. Studies of the Milky Way, however, have yet to identify the expected few hundred sub-halos with masses greater than about 10^6 Msun. Here we propose a test for the presence of sub-halos in the halos of galaxies. We show that the structure of the tidal tails of ancient globular clusters is very sensitive to heating by repeated close encounters with the massive dark sub-halos. We discuss the detection of such an effect in the context of the …
Far-infrared Spitzer observations of elliptical galaxies are inconsistent with simple steady state models of dust creation in red giant stars and destruction by grain sputtering in the hot interstellar gas at T ~ 10^7 K. The flux at 24 microns correlates with optical fluxes, suggesting that this relatively hot dust is largely circumstellar. But fluxes at 70 and 160 microns do not correlate with optical fluxes. Elliptical galaxies with similar L_B have luminosities at 70 and 160 microns (L_70 and L_160) that vary over a factor ~ 100, implying an additional source of dust unrelated to that produ…
In this letter we report on the discovery of a z=2.83 Lyman-alpha Blob (LAB) found in our wide field narrow-band survey within the Spitzer First Look Survey region. The blob is extended over at least 95kpc and has a total Lyman-alpha luminosity of 2.1 x 10^44 erg/s. It is only the sixth LAB known of this scale (> 50 kpc), and is associated with an embedded continuum source in g', R, i', K & 4.5 um bands. The LAB's optical spectrum shows clumpy structures and tantalising hints of a sharp red cut-off and shear within the Ly-alpha emission line. Studies of the LAB's surface brightness profile and…
We test the hypothesis that globular clusters form in supergiant molecular clouds within high-redshift galaxies. Numerical simulations demonstrate that such large, dense, and cold gas clouds assemble naturally in current hierarchical models of galaxy formation. These clouds are enriched with heavy elements from earlier stars and could produce star clusters in a similar way to nearby molecular clouds. The masses and sizes of the model clusters are in excellent agreement with the observations of young massive clusters. Do these model clusters evolve into globular clusters that we see in our and …
Spitzer observations of extended dust in two optically normal elliptical galaxies provide a new confirmation of buoyant feedback outflow in the hot gas atmospheres around these galaxies. AGN feedback energy is required to prevent wholesale cooling and star formation in these group-centered galaxies. In NGC 5044 we observe interstellar (presumably PAH) emission at 8 microns out to about 5 kpc. Both NGC 5044 and 4636 have extended 70 microns emission from cold dust exceeding that expected from stellar mass loss. The sputtering lifetime of this extended dust in the ~1keV interstellar gas, ~10^7 y…
(abbreviated) We report detection with the Spitzer Space Telescope of cool dust surrounding solar type stars. The observations were performed as part of the Legacy Science Program, ``Formation and Evolution of Planetary Systems'' (FEPS). From the overall FEPS sample (Meyer et al. 2006) of 328 stars having ages ~0.003-3 Gyr we have selected sources with 70 um flux densities indicating excess in their spectral energy distributions above expected photospheric emission........ .....The rising spectral energy distributions towards - and perhaps beyond - 70 um imply dust temperatures T_dust <45-85 K…
Spitzer Space Telescope imaging as part of the Galactic Legacy Mid-Plane Survey Extraordinaire (GLIMPSE) reveals a previously unidentified low-latitude rich star cluster near l=31.3 degrees, b=-0.1 degrees. Near-infrared JHK' photometry from the Wyoming Infrared Observatory indicates an extinction of A_V ~ 15+/-3 mag for cluster members. Analysis of 13CO features along the same sightline suggests a probable kinematic distance of 3.1 -- 5.2 kpc. The new cluster has an angular diameter of ~1-2 pc, a total magnitude m_{K_0}=2.1 corrected for extinction, and a luminosity of M_K ~ -10.3 at 3.1 kpc.…
A powerful way to observe directly the solid state inventory of dense molecular clouds is by infrared spectroscopy of background stars. We present Spitzer/IRS 5-20 micron spectra of ices toward stars behind the Serpens and Taurus molecular clouds, probing visual extinctions of 10-34 mag. These data provide the first complete inventory of solid-state material in dense clouds before star formation begins. The spectra show prominent 6.0 and 6.85 micron bands. In contrast to some young stellar objects (YSOs), most (~75%) of the 6.0 micron band is explained by the bending mode of pure water ice. In…
The Milky Way contains several distinct old stellar components that provide a fossil record of its formation. We can understand their spatial distribution and kinematics in a hierarchical formation scenario by associating the proto-galactic fragments envisaged by Searle and Zinn (1978) with the rare peaks able to cool gas in the cold dark matter density field collapsing at redshift z>10. We use hierarchical structure formation simulations to explore the kinematics and spatial distribution of these early star-forming structures in galaxy haloes today. Most of the proto-galaxies rapidly merge, t…
Fluxes and upper limits in the wavelength range from 3.6 to 70 microns from the Spitzer Space Telescope are provided for twenty solar-mass Pleiades members. One of these stars shows a probable mid-IR excess and two others have possible excesses, presumably due to circumstellar debris disks. For the star with the largest, most secure excess flux at MIPS wavelengths, HII1101, we derive Log(L[dust]/L[Sun]) ~ -3.8 and an estimated debris disk mass of 4.2 x 10^-5 M(Earth) for an assumed uniform dust grain size of 10 microns If the stars with detected excesses are interpreted as stars with relativel…
We present the first MIR spectrum of the z=2.2856 ultraluminous, infrared galaxy FSC 10214+4724, obtained with the Infrared Spectrograph onboard the Spitzer Space Telescope. The spectrum spans a rest wavelength range of 2.3-11.5 microns, covering a number of key diagnostic emission and absorption features. The most prominent feature in the IRS spectrum is the silicate emission at rest-frame 10 microns. We also detect an unresolved emission line at a rest wavelength of 7.65 microns which we identify with [NeVI], and a slightly resolved feature at 5.6 microns identified as a blend of [Mg VII] an…
We have conducted a survey of Ultra-luminous Infrared Galaxies (ULIRGs) with the Infrared Spectrograph on the Spitzer Space Telescope, obtaining spectra from 5.0-38.5um for 77 sources with 0.02<z <0.93. Observations of the pure rotational H2 lines S(3) 9.67um, S(2) 12.28um, and S(1) 17.04um are used to derive the temperature and mass of the warm molecular gas. We detect H2 in 77% of the sample, and all ULIRGs with F(60um)>2Jy. The average warm molecular gas mass is ~2x10^8solar-masses. High extinction, inferred from the 9.7um silicate absorption depth, is not observed along the line of site to…
Many models of globular cluster formation assume the presence of cold dense clouds in early universe. Here we re-examine the Fall & Rees (1985) model for formation of proto-globular cluster clouds (PGCCs) via thermal instabilities in a protogalactic halo. We first argue, based on the previous study by others, that under the protogalactic environments only nonlinear density inhomogeneities can condense into PGCCs. We then carry out numerical simulations of the collapse of overdense clouds in one-dimensional spherical geometry, including self-gravity and radiative cooling down to T=10^4 K. Since…
We present a 900 sec, wide-field U image of the inner region of the Andromeda galaxy obtained during the commissioning of the blue channel of the Large Binocular Camera mounted on the prime focus of the Large Binocular Telescope. Relative photometry and absolute astrometry of individual sources in the image was obtained along with morphological parameters aimed at discriminating between stars and extended sources, e.g. globular clusters. The image unveils the near-ultraviolet view of the inner ring of star formation recently discovered in the infrared by the Spitzer Space Telescope and shows i…
We test the hypothesis that metal-poor globular clusters form within disk galaxies at redshifts z>3. Numerical simulations demonstrate that giant gas clouds, which are cold and dense enough to produce massive star clusters, assemble naturally in hierarchical models of galaxy formation at high redshift. Do model clusters evolve into observed globular clusters or are they disrupted before present as a result of the dynamical evolution? To address this question, we calculate the orbits of model clusters in the time-variable gravitational potential of a Milky Way-sized galaxy, using the outputs of…
We report the observations of 12 globular clusters with the AKARI/FIS. Our goal is to search for emission from the cold dust within clusters. We detect diffuse emissions toward NGC 6402 and 2808, but the IRAS 100-micron maps show the presence of strong background radiation. They are likely emitted from the galactic cirrus, while we cannot rule out the possible association of a bump of emission with the cluster in the case of NGC 6402. We also detect 28 point-like sources mainly in the WIDE-S images (90 micron). At least several of them are not associated with the clusters but background galaxi…
