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Sample records for dust lane galaxy

  1. Boxy isophotes, discs and dust lanes in elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Lauer, T. R.

    1985-01-01

    CCD images of 42 elliptical and S0 galaxies are examined for low-contrast structures or subtle distortions of the isophotes from perfect ellipses. 75 percent of the galaxies have isophotes completely describable as concentric ellipses to within the photometry errors. 'Boxy' isophotes, stellar discs, and dust lanes are detected in the remaining 25 percent of the sample. The boxy elliptical galaxies appear dynamically indistinguishable from normal ellipticals and are therefore different from boxy bulges, which rotate rapidly. Most of the galaxies with faint discs, however, appear dynamically similar to S0 galaxies. Nearly edge-on dust lanes are found in four galaxies, which suggests that dust lanes may commonly occur in elliptical galaxies.

  2. Dust lanes in backlit galaxies: first results from the STARSMOG survey

    NASA Astrophysics Data System (ADS)

    Keel, William C.; Bradford, Sarah; Holwerda, Benne; Conselice, Christopher; Baldry, Ivan; Bland-Hawthorn, Jonathan; Driver, Simon P.; Dunne, Loretta; Liske, Jochen; Robotham, Aaron; Tuffs, Richard

    2017-01-01

    STARSMOG is an HST WFC3 snapshot survey of dust attenuation in overlapping backlit galaxies, planned to span the range of morphological type and luminosity of dust-rich galaxies. The target list came from the Galaxy Zoo and GAMA catalogs, imposing a minimum redshift difference to guarantee large line-of-sight separations, virtually eliminating scattering corrections and avoiding potentially distorted interacting systems. These include the first flocculent spirals studied with the occulting-galaxy approach. We present results from the geometrically most favorable subset of 9 pairs from the 54 observed STARSMOG systems. The data quality and intensity of background light let us map dust features with attenuations of only a few per cent in the red F606W band. Organized dust lanes show sharp outer boundaries in disks, and are absent in galaxies of late Hubble type. Many Sb-Sc disks show a dusty web of criss-crossing lanes, some nearly at right angles to the overall spiral pattern. Particularly favorable cases constraint the scale height of starlight in the foreground disks, through comparison of the light loss in regions with and without background light. The covering fraction of dust at various attenuation levels is consistent between barred and nonbarred spirals, although dust features may be more concentrated in azimuth when a bar is present (and concentrated in an annulus when a stellar resonance ring is seen). Together with our previous data on much more limited samples or at lower resolution,these results add to a picture where galaxies of similar morphology may have quite different attenuation patterns with radius for both arm and interarm dust.

  3. Ionized Gas in E/S0 Galaxies with Dust Lanes

    NASA Astrophysics Data System (ADS)

    Funes, Jose G.; J., S.; Finkelman, I.; Borsch, N.; Vaisanen, P.; Kniazev, A.

    2011-01-01

    We present results from an ongoing program to study the properties of dust and ionized gas in E/S0 galaxies with dust lanes. Our observational program comprises of H-alpha and broad-band images obtained with the SAAO 1.9m, the VATT 1.8m and the 1m telescope on WO. A detailed analysis of 30 galaxies shows the presence of a diffusely distributed ionized gas component in most objects. The extended gas morphology is typically smooth and closely follows the dust structure, with a clear correlation between the mass of both components. The dust content in each galaxy is estimated by measuring the extinction by the extragalactic dust in the dark lanes. The derived extinction law is used to correct the measured colors for intrinsic dust extinction and the data are fitted with a stellar population synthesis model. We find that the line-emission and colors of most objects are consistent with the presence of an “old” stellar population ( 10 Gyr) and a small fraction of a “young” population ( 10- 100 Myr). The younger stellar population may have formed at a later stage of the evolution of the galaxy through either a merger event or a secondary star-formation burst. Strong evidence for the external origin of the ISM is provided by the apparent inclination of the dust and ionized gas disks with respect to the galactic plane in a large fraction of our sample galaxies. Further spectroscopic observations will be obtained to study the gaseous disks dynamics and to characterize the underlying stellar populations for evidence of multiple phases of star formation and assembly history.

  4. POLYCYCLIC AROMATIC HYDROCARBON EMISSION FROM THE DUST LANE OF AN ELLIPTICAL GALAXY WITH THE SPITZER INFRARED SPECTROGRAPH

    SciTech Connect

    Kaneda, Hidehiro; Ishihara, Daisuke; Yamagishi, Mitsuyoshi; Onaka, Takashi; Sakon, Itsuki; Kitayama, Tetsu; Okada, Yoko; Suzuki, Toyoaki

    2010-06-20

    Spitzer and AKARI observations have found that polycyclic aromatic hydrocarbons (PAHs) are present in nearby elliptical galaxies, but their spatial distributions are still unknown. In order to investigate their distributions, we performed deep spectral mapping observations of the PAH-detected elliptical galaxy NGC 4589, a merger remnant with a minor-axis optical dust lane. As a result, we obtain clear evidence that the PAH 11.3 {mu}m emission comes predominantly from the dust lane of the galaxy. We also detect molecular hydrogen line emissions from the dust lane. The PAH 17 {mu}m emission is distributed differently from the PAH 11.3 {mu}m emission, and more similarly to the dust continuum emission. From their distinctive distributions, we suggest that the PAHs responsible for the 11.3 {mu}m feature are secondary products through the evolution of the interstellar medium brought in by the merger.

  5. An extremely low gas-to-dust ratio in the dust-lane lenticular galaxy NGC 5485

    NASA Astrophysics Data System (ADS)

    Baes, Maarten; Allaert, Flor; Sarzi, Marc; De Looze, Ilse; Fritz, Jacopo; Gentile, Gianfranco; Hughes, Thomas M.; Puerari, Ivânio; Smith, Matthew W. L.; Viaene, Sébastien

    2014-10-01

    Evidence is mounting that a significant fraction of the early-type galaxy population contains substantial reservoirs of cold interstellar gas and dust. We investigate the gas and dust in NGC 5485, an early-type galaxy with a prominent minor-axis dust lane. Using new Herschel PACS and SPIRE imaging data, we detect 3.8 × 106 M⊙ of cool interstellar dust in NGC 5485, which is in stark contrast with the non-detection of the galaxy in sensitive H I and CO observations from the ATLAS3D consortium. The resulting gas-to-dust ratio upper limit is Mgas/Md < 14.5, almost an order of magnitude lower than the canonical value for the Milky Way. We scrutinize the reliability of the dust, atomic gas and molecular gas mass estimates, but these do not show systematic uncertainties that can explain the extreme gas-to-dust ratio. Also a warm or hot ionized gas medium does not offer an explanation. A possible scenario could be that NGC 5485 merged with an SMC-type metal-poor galaxy with a substantial CO-dark molecular gas component and that the bulk of atomic gas was lost during the interaction, but it remains to be investigated whether such a scenario is possible.

  6. Embedded star formation in S{sup 4}G galaxy dust lanes

    SciTech Connect

    Elmegreen, Debra M.; Teich, Yaron; Popinchalk, Mark; Elmegreen, Bruce G.; Erroz-Ferrer, Santiago; Knapen, Johan H.; Comerón, Sébastien; Laine, Jarkko; Laurikainen, Eija; Gadotti, Dimitri A.; Kim, Taehyun; De Paz, Armando Gil; Hinz, Joannah L.; Ho, Luis C.; Holwerda, Benne; Menéndez-Delmestre, Karín; Mizusawa, Trisha [National Radio Astronomy Observatory and others

    2014-01-01

    Star-forming regions that are visible at 3.6 μm and Hα but not in the u, g, r, i, z bands of the Sloan Digital Sky Survey are measured in five nearby spiral galaxies to find extinctions averaging ∼3.8 mag and stellar masses averaging ∼5 × 10{sup 4} M {sub ☉}. These regions are apparently young star complexes embedded in dark filamentary shock fronts connected with spiral arms. The associated cloud masses are ∼10{sup 7} M {sub ☉}. The conditions required to make such complexes are explored, including gravitational instabilities in spiral-shocked gas and compression of incident clouds. We find that instabilities are too slow for a complete collapse of the observed spiral filaments, but they could lead to star formation in the denser parts. Compression of incident clouds can produce a faster collapse but has difficulty explaining the semi-regular spacing of some regions along the arms. If gravitational instabilities are involved, then the condensations have the local Jeans mass. Also in this case, the near-simultaneous appearance of equally spaced complexes suggests that the dust lanes, and perhaps the arms too, are relatively young.

  7. EVOLUTION IN THE DUST LANE FRACTION OF EDGE-ON L*{sub V} SPIRAL GALAXIES SINCE z = 0.8

    SciTech Connect

    Holwerda, B. W.; Boeker, T.; Dalcanton, J. J.; Radburn-Smith, D.; De Jong, R. S.; Guhathakurta, P.

    2012-07-01

    The presence of a well-defined and narrow dust lane in an edge-on spiral galaxy is the observational signature of a thin and dense molecular disk, in which gravitational collapse has overcome turbulence. Using a sample of galaxies out to z {approx} 1 extracted from the COSMOS survey, we identify the fraction of massive (L*{sub V}) disks that display a dust lane. Our goal is to explore the evolution in the stability of the molecular interstellar medium (ISM) disks in spiral galaxies over a cosmic timescale. We check the reliability of our morphological classifications against changes in rest-frame wavelength, resolution, and cosmic dimming with (artificially redshifted) images of local galaxies from the Sloan Digital Sky Survey. We find that the fraction of L*{sub V} disks with dust lanes in COSMOS is consistent with the local fraction ( Almost-Equal-To 80%) out to z {approx} 0.7. At z = 0.8, the dust lane fraction is only slightly lower. A somewhat lower dust lane fraction in starbursting galaxies tentatively supports the notion that a high specific star formation rate can efficiently destroy or inhibit a dense molecular disk. A small subsample of higher redshift COSMOS galaxies display low internal reddening (E[B - V]), as well as a low incidence of dust lanes. These may be disks in which the growth of the dusty ISM disk lags behind that of the stellar disk. We note that at z = 0.8, the most massive galaxies display a lower dust lane fraction than lower mass galaxies. A small contribution of recent mergers or starbursts to this most massive population may be responsible. The fact that the fraction of galaxies with dust lanes in COSMOS is consistent with little or no evolution implies that models to explain the spectral energy distribution or the host galaxy dust extinction of supernovae based on local galaxies are still applicable to higher redshift spirals. It also suggests that dust lanes are long-lived phenomena or can be reformed over very short timescales.

  8. On the morphology of dust lanes in galactic bars

    NASA Astrophysics Data System (ADS)

    Sánchez-Menguiano, L.; Pérez, I.; Zurita, A.; Martínez-Valpuesta, I.; Aguerri, J. A. L.; Sánchez, S. F.; Comerón, S.; Díaz-García, S.

    2015-07-01

    The aim of our study is to use dynamical simulations to explore the influence of two important dynamical bar parameters, bar strength and bar pattern speed on the shape of the bar dust lanes. To quantify the shape of the dust lanes we have developed a new systematic method to measure the dust lane curvature. Previous numerical simulations have compared the curvature of bar dust lanes with the bar strength, predicting a relation between both parameters which has been supported by observational studies but with a large spread. We take into account the bar pattern speed to explore, simultaneously, the effect of both parameters on the dust lane shape. To that end, we separate our galactic bars in fast bars (1 < {R} < 1.4 ) and slow bars ({R} > 1.4 ), obtaining, as previous simulations, an inverse relation between the dust lane curvature and the bar strength for fast bars. For the first time, we extend the study to slow bars, finding a constant curvature as a function of the bar strength. As a result, we conclude that weak bars with straight dust lanes are candidates for slow bars. Finally, we have analysed a pilot sample of 10 S4G galaxies, obtaining dust lane curvatures lying within the range covered by the simulations.

  9. The nuclear dust lane of Circinus: collimation without a torus

    NASA Astrophysics Data System (ADS)

    Mezcua, M.; Prieto, M. A.; Fernández-Ontiveros, J. A.; Tristram, K. R. W.

    2016-03-01

    In some AGN, nuclear dust lanes connected to kpc-scale dust structures provide all the extinction required to obscure the nucleus, challenging the role of the dusty torus proposed by the Unified Model. In this letter, we show the pc-scale dust and ionized gas maps of Circinus constructed using sub-arcsec-accuracy registration of infrared VLT AO images with optical Hubble Space Telescope images. We find that the collimation of the ionized gas does not require a torus but is caused by the distribution of dust lanes of the host galaxy on ˜10 pc scales. This finding questions the presumed torus morphology and its role at parsec scales, as one of its main attributes is to collimate the nuclear radiation, and is in line with interferometric observations which show that most of the pc-scale dust is in the polar direction. We estimate that the nuclear dust lane in Circinus provides 1/3 of the extinction required to obscure the nucleus. This constitutes a conservative lower limit to the obscuration at the central parsecs, where the dust filaments might get optically thicker if they are the channels that transport material from ˜100 pc scales to the centre.

  10. Dense gas in the dust lane of Centaurus A

    NASA Astrophysics Data System (ADS)

    Wild, W.; Eckart, A.

    2000-07-01

    The interstellar medium of Centaurus A (NGC 5128) has been studied extensively in recent years, using mostly molecular lines tracing low to medium density gas (500 to several 103 cm-3). The amount and distribution of the dense molecular gas was largely unknown. Here we present new millimeter data of the HCN(1-0), CS(2-1), and CS(3-2) rotational transitions towards the nearby radio galaxy Centaurus A observed with the SEST on La Silla, Chile. We obtained spectra of the HCN(1-0) emission which traces dense 104 cm-3 molecular gas at the center and along the prominent dust lane at offset positions +/-60'' and +/-100''. We also obtained a few spectra of CS(2-1) and (3-2) tracing densities of ~ 105 cm-3. The emission in these lines is weak and reaches a few mK at the available angular resolutions of 54'' - 36''. At the central position, the integrated intensity ratio I(HCN)/I(CO) peaks at 0.064, and decreases to ~ 0.02 to 0.04 in the dust lane. Using the new high density tracer data, we estimate the amount, distribution and physical conditions of the dense molecular gas in the dust lane of Centaurus A. We find that Cen A and the Milky Way are comparable in their HCN(1-0) line luminosity. However, towards the nucleus the fraction of dense molecular gas measured via the line luminosity ratio L(HCN)/L(CO) as well as the star formation efficiency L_FIR/L_CO is comparable to ultra-luminous infrared galaxies (ULIRGs). Within the off-nuclear dust lane and for Cen A as a whole these quantities are between those of ULIRGs and normal and infrared luminous galaxies. This suggests that most of the FIR luminosity of Centaurus A originates in regions of very dense molecular gas and high star formation efficiency. Based on observations collected at the European Southern Observatory, La Silla, Chile

  11. Dust in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Polikarpova, O. L.; Shchekinov, Yu. A.

    2017-02-01

    The conditions for the destruction of dust in hot gas in galaxy clusters are investigated. It is argued that extinction measurements can be subject to selection effects, hindering their use in obtaining trustworthy estimates of dust masses in clusters. It is shown, in particular, that the ratio of the dust mass to the extinction M d / S d increases as dust grains are disrupted, due to the rapid destruction of small grains. Over long times, this ratio can asymptotically reach values a factor of three higher than the mean value in the interstellar medium in the Galaxy. This lowers dust-mass estimates based on measurements of extinction in galaxy clusters. The characteristic lifetime of dust in hot cluster gas is determined by its possible thermal isolation by the denser medium of gas fragments within which the dust is ejected from galaxies, and can reach 100-300 million years, depending on the kinematics and morphology of the fragments. As a result, the mass fraction of dust in hot cluster gas can reach 1-3% of the Galactic value. Over its lifetime, dust can also be manifest through its far-infrared emission. The emission characteristics of the dust change as it is disrupted, and the ratio of the fluxes at 350 and 850 μm can increase appreciably. This can potentially serve as an indicator of the state of the dust and ambient gas.

  12. Galaxy formation by dust

    NASA Technical Reports Server (NTRS)

    Wang, Boqi; Field, Goerge B.

    1989-01-01

    It has been known since the early 1940's that radiation can cause an instability in the interstellar medium. Absorbing dust particles in an isotropic radiation field shadow each other by a solid angle which is inversely proportional to the square of the distance between the two particles, leading to an inverse-square attractive force - mock gravity. The effect is largest in an optically thin medium. Recently Hogan and White (HW, hereafter) proposed that if the pre-galactic universe contained suitable sources of radiation and dust, instability in the dust distribution caused by mock gravity may have led to the formation of galaxies and galaxy clusters. In their picture of a well-coupled dust-gas medium, HW show that mock gravity begins to dominate gravitational instability when the perturbation becomes optically thin, provided that the radiation field at the time is strong enough. The recent rocket observation of the microwave background at submillimeter wavelengths by Matsumoto et al. might be from pre-galactic stars, the consequence of the absorption of ultraviolet radiation by dust, and infrared reemission which is subsequently redshifted. HW's analysis omits radiative drag, incomplete collisional coupling of gas and dust, finite dust albedo, and finite matter pressure. These effects could be important. In a preliminary calculation including them, the authors have confirmed that mock gravitational instability is effective if there is a strong ultraviolet radiation at the time, but any galaxies that form would be substantially enriched in heavy elements because the contraction of the dust is more rapid than that of the gas. Moreover, since the dust moves with supersonic velocity through the gas soon after the perturbation becomes optically thin, the sputtering of dust particles by gas is significant, so the dust could disappear before the instability develops significantly. They conclude that the mock gravity by dust is not important in galaxy formations.

  13. Dust and Ionized Gas in Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Goudfrooij, Paul

    1995-05-01

    ellipticals. The detection rate of dust and ionized gas are found to be about 40% and 60%, respectively, which is significantly higher than that of previous imaging studies. The distributions of dust and ionized gas are consistent with being physically associated with each other. The wavelength dependence of the dust extinction in elliptical galaxies with large-scale dust lanes are presented and discussed in chapter 5. We find that the dust grains in dust-lane elliptical galaxies are smaller on average than the canonical grain size in our Galaxy. Comparing the typical lifetime of dust grains in different environments with formation timescales of lanes and/or rings in elliptical galaxies, we suggest that the observed characteristic dust grain size is determined by the time elapsed since the dust lane was accreted from outside. In Chapter 6 we combine the IRAS far-infrared observations, our optical survey data, and the available X-ray data of the galaxies in our sample. We find that dust masses as determined from the IRAS data are roughly an order of magnitude higher than those determined from optical extinction. To solve this dilemma we argue that the majority of the dust in elliptical galaxies exists as a diffusely distributed component. We show that the assumption of this newly postulated distribution of dust in terms of total masses and energetics of the dust is entirely consistent with heating by optical photons and hot electrons in the X-ray-emitting gas. The diffuse component of dust is found to have a non-negligible effect on the radial colour gradients in elliptical galaxies, and should thus be taken seriously in the interpretation of colour gradients. Several arguments in favour of an external origin of dust in elliptical galaxies are discussed. Last but not least, a strong anticorrelation between the masses of dust and hot gas in X-ray luminous elliptical galaxies is found and discussed. (SECTION: Dissertation Summaries)

  14. The neutral dust and gas in the radio galaxy 3C 305

    NASA Astrophysics Data System (ADS)

    Jackson, N.; Beswick, R.; Pedlar, A.; Cole, G.; Leahy, J. P.; Holloway, A. J.; Sparks, W. B.; Axon, D.

    3C305 is a nearby radio galaxy which shows strong warping of the stellar disk and a dust lane running almost parallel to the jet axis. We present and discuss HST and radio studies of the dust and gas which strongly constrain the geometry of this system, and explore the line ionization mechanism (photoionization/ jet-induced shocks) using emission line diagnostic ratios.

  15. Differential dust attenuation in CALIFA galaxies

    NASA Astrophysics Data System (ADS)

    Vale Asari, N.; Cid Fernandes, R.; Amorim, A. L.; Lacerda, E. A. D.; Schlickmann, M.; Wild, V.; Kennicutt, R. C.

    2016-06-01

    Dust attenuation has long been treated as a simple parameter in SED fitting. Real galaxies are, however, much more complicated: The measured dust attenuation is not a simple function of the dust optical depth, but depends strongly on galaxy inclination and the relative distribution of stars and dust. We study the nebular and stellar dust attenuation in CALIFA galaxies, and propose some empirical recipes to make the dust treatment more realistic in spectral synthesis codes. By adding optical recombination emission lines, we find better constraints for differential attenuation. Those recipes can be applied to unresolved galaxy spectra, and lead to better recovered star formation rates.

  16. Cold dust in elliptical galaxies.

    NASA Astrophysics Data System (ADS)

    Wiklind, T.; Henkel, C.

    1995-05-01

    We have observed the λ1250 µm flux in 8 elliptical galaxies using the MPIfR 7-channel bolometer system attachet to the IRAM 30-m telescope. Five of the galaxies are detected at more than 3σ, two are tentatively detected and for one we obtained an upper limit. For two of the detected galaxies, the CO(2-1) line makes a significant contribution to the measured λ1250 µm flux. A comparison of the λ1250 µm fluxes, corrected for the CO(2-1) line contribution, with IRAS 60 and 100µm data shows that there is a colt dust component (Td~<20K) in two of the ellipticals. The other galaxies have λ1250 µm fluxes consistent with a one-temperature component, with Td typically between 20-30K.

  17. A molecular gas ridge offset from the dust lane in a spiral arm of M83

    NASA Technical Reports Server (NTRS)

    Lord, Steven D.; Kenney, Jeffrey D. P.

    1991-01-01

    A high-resolution interferometric map of the CO emission on the eastern spiral arm of M83 is presented. The detected emission originates in about five unresolved components located parallel but about 300 pc downstream from the dust lane which lies along the inner edge of the spiral arm. All the CO components in the map but one are located within 130 pc of an H II region and may represent emission from locally heated gas. The lack of CO emission on the dust lane indicates that the dense molecular gas does not pile up here in M83. Remarkable differences between the molecular gas distributions in M83 and the spiral arms or M51, where CO emission peaks on the dust lane, is attributed to the difference in the strength of their density waves. The observations of M83 are consistent with the model of Elmegreen in which diffuse gas is compressed at the shock front, producing the dust lane at the inner edge of the spiral arm while dense giant molecular clouds pass through the front and form a broad distribution on the arm.

  18. Dust in Cluster Dwarf Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    De Looze, I.; Baes, M.; Fritz, J.; Verstappen, J.; Bendo, G. J.; Bianchi, S.; Bomans, D. J.; Boselli, A.; Clemens, M.; Corbelli, E.; Cortese, L.; Dariush, A.; Davies, J. I.; di Serego Alighieri, S.; Fadda, D.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Grossi, M.; Hughes, T. M.; Hunt, L. K.; Jones, A. P.; Madden, S.; Magrini, L.; Pierini, D.; Pohlen, M.; Sabatini, S.; Smith, M. W. L.; Vlahakis, C.; Xilouris, E. M.; Zibetti, S.

    Based on single cross-scan data of the Herschel Virgo Cluster Survey, we report the first detections of dust in cluster early-type dwarf galaxies: VCC 209, VCC 781 and VCC 951. All three galaxies have dust masses M d ≈ 105 - 106 M⊙ and average dust temperatures ≈ 16-20 K. Since these three early-type dwarfs reside in densely crowded regions close to the center of the Virgo cluster, and several H I-detected dwarfs in the outskirts of Virgo were not detected by Herschel(implying a dust content < 104 M⊙), this might imply that dust in dwarfs is more closely related to the molecular gas, which is more centrally peaked in a galaxy's potential well and therefore, not easily removed by any stripping mechanism. We conclude that the removal of interstellar dust from these early-type dwarfs appears to be less efficient than the removal of the H I gas.

  19. Galaxy simulation with dust formation and destruction

    NASA Astrophysics Data System (ADS)

    Aoyama, Shohei; Hou, Kuan-Chou; Shimizu, Ikkoh; Hirashita, Hiroyuki; Todoroki, Keita; Choi, Jun-Hwan; Nagamine, Kentaro

    2017-04-01

    We perform smoothed particle hydrodynamics (SPH) simulations of an isolated galaxy with a new treatment for dust formation and destruction. To this aim, we treat dust and metal production self-consistently with star formation and supernova (SN) feedback. For dust, we consider a simplified model of grain size distribution by representing the entire range of grain sizes with large and small grains. We include dust production in stellar ejecta, dust destruction by SN shocks, grain growth by accretion and coagulation and grain disruption by shattering. We find that the assumption of fixed dust-to-metal mass ratio becomes no longer valid when the galaxy is older than 0.2 Gyr, at which point the grain growth by accretion starts to contribute to the non-linear rise of dust-to-gas ratio. As expected in our previous one-zone model, shattering triggers grain growth by accretion since it increases the total surface area of grains. Coagulation becomes significant when the galaxy age is greater than ∼ 1 Gyr; at this epoch, the abundance of small grains becomes high enough to raise the coagulation rate of small grains. We further compare the radial profiles of dust-to-gas ratio (D) and dust-to-metal ratio (D/Z, i.e. depletion) at various ages with observational data. We find that our simulations broadly reproduce the radial gradients of dust-to-gas ratio and depletion. In the early epoch (≲ 0.3 Gyr), the radial gradient of D follows the metallicity gradient with D/Z determined by the dust condensation efficiency in stellar ejecta, while the D gradient is steeper than the Z gradient at the later epochs because of grain growth by accretion. The framework developed in this paper is applicable to any SPH-based galaxy evolution simulations including cosmological ones.

  20. Dust obscuration by an evolving galaxy population

    NASA Technical Reports Server (NTRS)

    Najita, Joan; Silk, Joseph; Wachter, Kenneth W.

    1990-01-01

    The effect of an evolving luminosity function (LF) on the ability of foreground galaxies to obscure background sources is discussed, using the Press-Schechter/CDM standard evolving LF model. Galaxies are modeled as simplified versions of local spirals and Poisson statistics are used to estimate the fraction of sky covered by intervening dusty galaxies and the mean optical depths due to these galaxies. The results are compared to those obtained in the case of nonevolving luminosity function in a low-density universe. It is found that evolution of the galaxy LF does not allow the quasar dust obscuration hypothesis to be sustained for dust disks with plausible sizes. Even in a low-density universe, where evolution at z = less than 10 is unimportant, large disk radii are needed to achieve the desired obscuring effect. The mean fraction of sky covered is presented as a function of the redshift z along with adequate diagram illustrations.

  1. New Fast Lane towards Discoveries of Clusters of Galaxies Inaugurated

    NASA Astrophysics Data System (ADS)

    2003-07-01

    Space and Ground-Based Telescopes Cooperate to Gain Deep Cosmological Insights Summary Using the ESA XMM-Newton satellite, a team of European and Chilean astronomers [2] has obtained the world's deepest "wide-field" X-ray image of the cosmos to date. This penetrating view, when complemented with observations by some of the largest and most efficient ground-based optical telescopes, including the ESO Very Large Telescope (VLT), has resulted in the discovery of several large clusters of galaxies. These early results from an ambitious research programme are extremely promising and pave the way for a very comprehensive and thorough census of clusters of galaxies at various epochs. Relying on the foremost astronomical technology and with an unequalled observational efficiency, this project is set to provide new insights into the structure and evolution of the distant Universe. PR Photo 19a/03: First image from the XMM-LSS survey. PR Photo 19b/03: Zoom-in on PR Photo 19b/03. PR Photo 19c/03: XMM-Newton contour map of the probable extent of a cluster of galaxies, superimposed upon a CHFT I-band image. PR Photo 19d/03: Velocity distribution in the cluster field shown in PR Photo 19c/03. The universal web Unlike grains of sand on a beach, matter is not uniformly spread throughout the Universe. Instead, it is concentrated into galaxies which themselves congregate into clusters (and even clusters of clusters). These clusters are "strung" throughout the Universe in a web-like structure, cf. ESO PR 11/01. Our Galaxy, the Milky Way, for example, belongs to the so-called Local Group which also comprises "Messier 31", the Andromeda Galaxy. The Local Group contains about 30 galaxies and measures a few million light-years across. Other clusters are much larger. The Coma cluster contains thousands of galaxies and measures more than 20 million light-years. Another well known example is the Virgo cluster, covering no less than 10 degrees on the sky ! Clusters of galaxies are the most

  2. Dust Production in Local Group Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Zijlstra, Albert; Sloan, Greg; Bernard-Salas, Jeronimo; Blommaert, Joris A. D. L.; Cioni, Maria-Rosa; Devost, Daniel; Feast, Michael W.; Groenewegen, Martin A. T.; Habing, Harm; Hony, Sacha; Lagadec, Eric; Loup, Cecile; Matsuura, Mikako; Menzies, John W.; Sloan, Greg C.; Waters, L. B. F. M.; Whitelock, Patricia A.; Wood, Peter R.; van Loon, Jacco Th.

    2006-05-01

    The superwind phase on the Asymptotic Giant Branch is a crucial ingredient of stellar and galactic evolution. The superwind ejecta are responsible for much of the interstellar hydrogen of evolved galaxies, and are a dominant contributor to the dust input into the ISM. The superwind determines the final mass of stellar remnants, and therefore affects, e.g., the type-I supernova rate. The characteristics of the superwind are still very poorly known, especially at non-solar metallicities. Spitzer has contributed a large and invaluable dataset on Magellanic Cloud stars, measuring dust, molecular bands and allowing accurate mass-loss measurements. We now propose to extend the (age, metallicity) parameter range by observing a number of other Milky Way satellites. The carbon stars in these galaxies trace an older population than the Magellanic Clouds, and extend to much lower metallicities. They are therefore crucial to allow us to extrapolate the Magellanic Cloud measurements to metal-poor environments. We propose to acquire low-resolution spectra of stars in the Sagittarius dwarf galaxy, Carina, Sculptor and Fornax. The selected stars range in metallicity from -0.55 to -2.0, and in age from 5-8 Gyr. Two low-metallicity planetary nebulae in these galaxies are also included. We will study the dust continuum, dust minerals (SiC, MgS) and gas-phase molecular bands (especially acetylene). Mass loss rates will be determined using our dust models, and we will measure the fractional abundances of amorphous carbon dust and SiC grains. Only Spitzer can provide these crucial measurements of extra-galactic AGB stars. The result will be our first knowledge of mass loss efficiency, dust formation, and dust abundances, at low to very low metallicities. These data are necessary to obtain reliable models of mass loss and of stellar evolution.

  3. HST/ACS observations of shell galaxies: inner shells, shell colours and dust

    NASA Astrophysics Data System (ADS)

    Sikkema, G.; Carter, D.; Peletier, R. F.; Balcells, M.; Del Burgo, C.; Valentijn, E. A.

    2007-06-01

    Context: Shells in Elliptical Galaxies are faint, sharp-edged features, believed to provide evidence for a merger event. Accurate photometry at high spatial resolution is needed to learn on presence of inner shells, population properties of shells, and dust in shell galaxies. Aims: Learn more about the origin of shells and dust in early type galaxies. Methods: V-I colours of shells and underlying galaxies are derived, using HST Advanced Camera for Surveys (ACS) data. A galaxy model is made locally in wedges and subtracted to determine shell profiles and colours. We applied Voronoi binning to our data to get smoothed colour maps of the galaxies. Comparison with N-body simulations from the literature gives more insight to the origin of the shell features. Shell positions and dust characteristics are inferred from model galaxy subtracted images. Results: The ACS images reveal shells well within the effective radius in some galaxies (at 0.24 re = 1.7 kpc in the case of NGC 5982). In some cases, strong nuclear dust patches prevent detection of inner shells. Most shells have colours which are similar to the underlying galaxy. Some inner shells are redder than the galaxy. All six shell galaxies show out of dynamical equilibrium dust features, like lanes or patches, in their central regions. Our detection rate for dust in the shell ellipticals is greater than that found from HST archive data for a sample of normal early-type galaxies, at the 95% confidence level. Conclusions: The merger model describes better the shell distributions and morphologies than the interaction model. Red shell colours are most likely due to the presence of dust and/or older stellar populations. The high prevalence and out of dynamical equilibrium morphologies of the central dust features point towards external influences being responsible for visible dust features in early type shell galaxies. Inner shells are able to manifest themselves in relatively old shell systems. Based on observations made

  4. First detection of equatorial dark dust lane in a protostellar disk at submillimeter wavelength

    PubMed Central

    Lee, Chin-Fei; Li, Zhi-Yun; Ho, Paul T. P.; Hirano, Naomi; Zhang, Qizhou; Shang, Hsien

    2017-01-01

    In the earliest (so-called “Class 0”) phase of Sun-like (low-mass) star formation, circumstellar disks are expected to form, feeding the protostars. However, these disks are difficult to resolve spatially because of their small sizes. Moreover, there are theoretical difficulties in producing these disks in the earliest phase because of the retarding effects of magnetic fields on the rotating, collapsing material (so-called “magnetic braking”). With the Atacama Large Millimeter/submillimeter Array (ALMA), it becomes possible to uncover these disks and study them in detail. HH 212 is a very young protostellar system. With ALMA, we not only detect but also spatially resolve its disk in dust emission at submillimeter wavelength. The disk is nearly edge-on and has a radius of ~60 astronomical unit. It shows a prominent equatorial dark lane sandwiched between two brighter features due to relatively low temperature and high optical depth near the disk midplane. For the first time, this dark lane is seen at submillimeter wavelength, producing a “hamburger”-shaped appearance that is reminiscent of the scattered-light image of an edge-on disk in optical and near infrared light. Our observations open up an exciting possibility of directly detecting and characterizing small disks around the youngest protostars through high-resolution imaging with ALMA, which provides strong constraints on theories of disk formation. PMID:28439561

  5. First detection of equatorial dark dust lane in a protostellar disk at submillimeter wavelength

    NASA Astrophysics Data System (ADS)

    Lee, Chin-Fei; Li, Zhi-Yun; Ho, Paul T. P.; Hirano, Naomi; Zhang, Qizhou; Shang, Hsien

    2017-04-01

    In the earliest (so-called "Class 0") phase of Sun-like (low-mass) star formation, circumstellar disks are expected to form, feeding the protostars. However, these disks are difficult to resolve spatially because of their small sizes. Moreover, there are theoretical difficulties in producing these disks in the earliest phase because of the retarding effects of magnetic fields on the rotating, collapsing material (so-called "magnetic braking"). With the Atacama Large Millimeter/submillimeter Array (ALMA), it becomes possible to uncover these disks and study them in detail. HH 212 is a very young protostellar system. With ALMA, we not only detect but also spatially resolve its disk in dust emission at submillimeter wavelength. The disk is nearly edge-on and has a radius of 60 astronomical unit. It shows a prominent equatorial dark lane sandwiched between two brighter features due to relatively low temperature and high optical depth near the disk midplane. For the first time, this dark lane is seen at submillimeter wavelength, producing a "hamburger"-shaped appearance that is reminiscent of the scattered-light image of an edge-on disk in optical and near infrared light. Our observations open up an exciting possibility of directly detecting and characterizing small disks around the youngest protostars through high-resolution imaging with ALMA, which provides strong constraints on theories of disk formation.

  6. Dust and ionized gas in elliptical galaxies: Signatures of merging collisions

    NASA Technical Reports Server (NTRS)

    Goudfrooij, Paul; Dejong, Teije

    1993-01-01

    Traditionally elliptical galaxies were thought to be essentially devoid of interstellar matter. However, recent advances in instrumental sensitivity have caused a renaissance of interest in dust and gas in - or associated with - elliptical galaxies. In particular, the technique of co-adding IRAS survey scans has led to the detection of more than half of all ellipticals with BT less than 11 mag. in the Revised Shapley-Ames catalog, indicating the presence of 10(exp 7) - 10(exp 8) solar mass of cold interstellar matter (Jura et al. 1987). In addition, CCD multi-color surface photometry shows dust patches in about 30 percent of the cases studied to date (e.g., Veron-Cetty & Veron 1988). Thorough study of the gas and dust in ellipticals is important to (1) determine its origin (mass-loss from late-type stars, merging collisions with other galaxies or accretion inflows from cooling X-ray gas), and (2) investigate the 3-D shape of ellipticals, as can be derived from the orientation of the dust lanes and the 2-D velocity field of the gas. An important result of our comprehensive CCD imaging program is that a relevant fraction (approximately 40 percent) of the sample objects exhibits dust patches within extended H-alpha+(NII) line-emitting filaments. This common occurrence can be easily accounted for if the dust and gas have an external origin, i.e., mergers or interactions with gas-rich galaxies. Evidence supporting this suggestion: (1) the ionized gas is usually dynamically decoupled from the stellar velocity field (see, e.g., Sharples et al. 1983, Bertola & Bettoni 1988); (2) it is shown in a companion paper (Goudfrooij et al. 1992) that internal stellar mass loss alone can not account for the dust content of elliptical galaxies.

  7. COSMIC EVOLUTION OF DUST IN GALAXIES: METHODS AND PRELIMINARY RESULTS

    SciTech Connect

    Bekki, Kenji

    2015-02-01

    We investigate the redshift (z) evolution of dust mass and abundance, their dependences on initial conditions of galaxy formation, and physical correlations between dust, gas, and stellar contents at different z based on our original chemodynamical simulations of galaxy formation with dust growth and destruction. In this preliminary investigation, we first determine the reasonable ranges of the most important two parameters for dust evolution, i.e., the timescales of dust growth and destruction, by comparing the observed and simulated dust mass and abundances and molecular hydrogen (H{sub 2}) content of the Galaxy. We then investigate the z-evolution of dust-to-gas ratios (D), H{sub 2} gas fraction (f{sub H{sub 2}}), and gas-phase chemical abundances (e.g., A {sub O} = 12 + log (O/H)) in the simulated disk and dwarf galaxies. The principal results are as follows. Both D and f{sub H{sub 2}} can rapidly increase during the early dissipative formation of galactic disks (z ∼ 2-3), and the z-evolution of these depends on initial mass densities, spin parameters, and masses of galaxies. The observed A {sub O}-D relation can be qualitatively reproduced, but the simulated dispersion of D at a given A {sub O} is smaller. The simulated galaxies with larger total dust masses show larger H{sub 2} and stellar masses and higher f{sub H{sub 2}}. Disk galaxies show negative radial gradients of D and the gradients are steeper for more massive galaxies. The observed evolution of dust masses and dust-to-stellar-mass ratios between z = 0 and 0.4 cannot be reproduced so well by the simulated disks. Very extended dusty gaseous halos can be formed during hierarchical buildup of disk galaxies. Dust-to-metal ratios (i.e., dust-depletion levels) are different within a single galaxy and between different galaxies at different z.

  8. Dust properties of Lyman-break galaxies in cosmological simulations

    NASA Astrophysics Data System (ADS)

    Yajima, Hidenobu; Nagamine, Kentaro; Thompson, Robert; Choi, Jun-Hwan

    2014-04-01

    Recent observations have indicated the existence of dust in high-redshift galaxies, however, the dust properties in them are still unknown. Here we present theoretical constraints on dust properties in Lyman-break galaxies (LBGs) at z = 3 by post-processing a cosmological smoothed particle hydrodynamics simulation with radiative transfer calculations. We calculate the dust extinction in 2800 dark matter haloes using the metallicity information of individual gas particles in our simulation. We use only bright galaxies with rest-frame ultraviolet (UV) magnitude M1700 < -20 mag, and study the dust size, dust-to-metal mass ratio, and dust composition. From the comparison of calculated colour excess between B and V band [i.e. E(B - V)] and the observations, we constrain the typical dust size, and show that the best-fitting dust grain size is ˜ 0.05 μm, which is consistent with the results of theoretical dust models for Type II supernova. Our simulation with the dust extinction effect can naturally reproduce the observed rest-frame UV luminosity function of LBGs at z = 3 without assuming an ad hoc constant extinction value. In addition, in order to reproduce the observed mean E(B - V), we find that the dust-to-metal mass ratio needs to be similar to that of the local galaxies, and that the graphite dust is dominant or at least occupy half of dust mass.

  9. DUST-DRIVEN WIND FROM DISK GALAXIES

    SciTech Connect

    Sharma, Mahavir; Nath, Biman B.; Shchekinov, Yuri E-mail: biman@rri.res.in

    2011-08-01

    We study gaseous outflows from disk galaxies driven by radiation pressure on dust grains. We include the effect of bulge and dark matter halo and show that the existence of such an outflow implies a maximum value of disk mass-to-light ratio. We show that the terminal wind speed is proportional to the disk rotation speed in the limit of a cold gaseous outflow, and that in general there is a contribution from the gas sound speed. Using the mean opacity of dust grains and the evolution of the luminosity of a simple stellar population, we then show that the ratio of the wind terminal speed (v{sub {infinity}}) to the galaxy rotation speed (v{sub c}) ranges between 2 and 3 for a period of {approx}10 Myr after a burst of star formation, after which it rapidly decays. This result is independent of any free parameter and depends only on the luminosity of the stellar population and the relation between disk and dark matter halo parameters. We briefly discuss the possible implications of our results.

  10. Surprising detection of an equatorial dust lane on the AGB star IRC+10216

    NASA Astrophysics Data System (ADS)

    Jeffers, S. V.; Min, M.; Waters, L. B. F. M.; Canovas, H.; Pols, O. R.; Rodenhuis, M.; de Juan Ovelar, M.; Keller, C. U.; Decin, L.

    2014-12-01

    Aims: Understanding the formation of planetary nebulae remains elusive because in the preceding asymptotic giant branch (AGB) phase these stars are heavily enshrouded in an optically thick dusty envelope. Methods: To further understand the morphology of the circumstellar environments of AGB stars we observe the closest carbon-rich AGB star IRC+10216 in scattered light. Results: When imaged in scattered light at optical wavelengths, IRC+10216 surprisingly shows a narrow equatorial density enhancement, in contrast to the large-scale spherical rings that have been imaged much further out. We use radiative transfer models to interpret this structure in terms of two models: firstly, an equatorial density enhancement, commonly observed in the more evolved post-AGB stars, and secondly, in terms of a dust rings model, where a local enhancement of mass-loss creates a spiral ring as the star rotates. Conclusions: We conclude that both models can be used to reproduce the dark lane in the scattered light images, which is caused by an equatorially density enhancement formed by dense dust rather than a bipolar outflow as previously thought. We are unable to place constraints on the formation of the equatorial density enhancement by a binary system. Final reduced images (FITS) are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A3Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  11. Simulating the dust content of galaxies: successes and failures

    NASA Astrophysics Data System (ADS)

    McKinnon, Ryan; Torrey, Paul; Vogelsberger, Mark; Hayward, Christopher C.; Marinacci, Federico

    2017-06-01

    We present full-volume cosmological simulations, using the moving-mesh code arepo to study the coevolution of dust and galaxies. We extend the dust model in arepo to include thermal sputtering of grains and investigate the evolution of the dust mass function, the cosmic distribution of dust beyond the interstellar medium and the dependence of dust-to-stellar mass ratio on galactic properties. The simulated dust mass function is well described by a Schechter fit and lies closest to observations at z = 0. The radial scaling of projected dust surface density out to distances of 10 Mpc around galaxies with magnitudes 17 < i < 21 is similar to that seen in Sloan Digital Sky Survey data, albeit with a lower normalization. At z = 0, the predicted dust density of Ωdust ≈ 1.3 × 10-6 lies in the range of Ωdust values seen in low-redshift observations. We find that the dust-to-stellar mass ratio anticorrelates with stellar mass for galaxies living along the star formation main sequence. Moreover, we estimate the 850 μm number density functions for simulated galaxies and analyse the relation between dust-to-stellar flux and mass ratios at z = 0. At high redshift, our model fails to produce enough dust-rich galaxies, and this tension is not alleviated by adopting a top-heavy initial mass function. We do not capture a decline in Ωdust from z = 2 to 0, which suggests that dust production mechanisms more strongly dependent on star formation may help to produce the observed number of dusty galaxies near the peak of cosmic star formation.

  12. ULTRAVIOLET RADIATIVE TRANSFER MODELING OF NEARBY GALAXIES WITH EXTRAPLANAR DUSTS

    SciTech Connect

    Shinn, Jong-Ho; Seon, Kwang-Il

    2015-12-20

    In order to examine their relation to the host galaxy, the extraplanar dusts of six nearby galaxies are modeled, employing a three-dimensional Monte Carlo radiative transfer code. The targets are from the highly inclined galaxies that show dust-scattered ultraviolet halos, and the archival Galaxy Evolution Explorer FUV band images were fitted with the model. The observed images are generally well-reproduced by two dust layers and one light source layer, whose vertical and radial distributions have exponential profiles. We obtained several important physical parameters, such as star formation rate (SFR{sub UV}), face-on optical depth, and scale-heights. Three galaxies (NGC 891, NGC 3628, and UGC 11794) show clear evidence for the existence of an extraplanar dust layer. However, it is found that the remaining three targets (IC 5249, NGC 24, and NGC 4173) do not necessarily need a thick dust disk to model the ultraviolet (UV) halo, because its contribution is too small and the UV halo may be caused by the wing part of the GALEX point spread function. This indicates that the galaxy samples reported to have UV halos may be contaminated by galaxies with negligible extraplanar (halo) dust. The galaxies showing evidence of an extraplanar dust layer fall within a narrow range on the scatter plots between physical parameters such as SFR{sub UV} and extraplanar dust mass. Several mechanisms that could possibly produce the extraplanar dust are discussed. We also found a hint that the extraplanar dust scale-height might not be much different from the polycyclic aromatic hydrocarbon emission characteristic height.

  13. Ultraviolet Radiative Transfer Modeling of Nearby Galaxies with Extraplanar Dusts

    NASA Astrophysics Data System (ADS)

    Shinn, Jong-Ho; Seon, Kwang-Il

    2015-12-01

    In order to examine their relation to the host galaxy, the extraplanar dusts of six nearby galaxies are modeled, employing a three-dimensional Monte Carlo radiative transfer code. The targets are from the highly inclined galaxies that show dust-scattered ultraviolet halos, and the archival Galaxy Evolution Explorer FUV band images were fitted with the model. The observed images are generally well-reproduced by two dust layers and one light source layer, whose vertical and radial distributions have exponential profiles. We obtained several important physical parameters, such as star formation rate (SFRUV), face-on optical depth, and scale-heights. Three galaxies (NGC 891, NGC 3628, and UGC 11794) show clear evidence for the existence of an extraplanar dust layer. However, it is found that the remaining three targets (IC 5249, NGC 24, and NGC 4173) do not necessarily need a thick dust disk to model the ultraviolet (UV) halo, because its contribution is too small and the UV halo may be caused by the wing part of the GALEX point spread function. This indicates that the galaxy samples reported to have UV halos may be contaminated by galaxies with negligible extraplanar (halo) dust. The galaxies showing evidence of an extraplanar dust layer fall within a narrow range on the scatter plots between physical parameters such as SFRUV and extraplanar dust mass. Several mechanisms that could possibly produce the extraplanar dust are discussed. We also found a hint that the extraplanar dust scale-height might not be much different from the polycyclic aromatic hydrocarbon emission characteristic height.

  14. Dust Content of Virgo Star-Forming Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Grossi, M.; Hunt, L. K.; Madden, S.; Vlahakis, C.; Bomans, D. J.; Baes, M.; Bendo, G. J.; Bianchi, S.; Boselli, A.; Clemens, M.; Corbelli, E.; Cortese, L.; Dariush, A.; Davies, J. I.; De Looze, I.; di Serego Alighieri, S.; Fadda, D.; Fritz, J.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Hughes, T. M.; Jones, A. P.; Pierini, D.; Pohlen, M.; Sabatini, S.; Smith, M. W. L.; Verstappen, J.; Xilouris, E. M.; Zibetti, S.

    We investigate the dust properties of a small sample of Virgo cluster dwarf galaxies drawn from the science demonstration phase data set of the Herschel Virgo Cluster Survey (HeViCS). These galaxies have low metallicities (7.8 < 12 + log(O/H) < 8.3) and star formation rates ≲ 0.1 M⊙ yr-1. We measure the spectral energy distribution (SED) from 100 to 500 μm and derive dust temperatures and masses. The SEDs are fitted by a cool component with T ≲ 20 K, implying dust masses around 105 M⊙ and dust-to-gas ratios (D) within the range 10-3-10-2.

  15. Dust formation in Milky Way-like galaxies

    NASA Astrophysics Data System (ADS)

    McKinnon, Ryan; Torrey, Paul; Vogelsberger, Mark

    2016-04-01

    We introduce a dust model for cosmological simulations implemented in the moving-mesh code AREPO and present a suite of cosmological hydrodynamical zoom-in simulations to study dust formation within galactic haloes. Our model accounts for the stellar production of dust, accretion of gas-phase metals on to existing grains, destruction of dust through local supernova activity, and dust driven by winds from star-forming regions. We find that accurate stellar and active galactic nuclei feedback is needed to reproduce the observed dust-metallicity relation and that dust growth largely dominates dust destruction. Our simulations predict a dust content of the interstellar medium which is consistent with observed scaling relations at z = 0, including scalings between dust-to-gas ratio and metallicity, dust mass and gas mass, dust-to-gas ratio and stellar mass, and dust-to-stellar mass ratio and gas fraction. We find that roughly two-thirds of dust at z = 0 originated from Type II supernovae, with the contribution from asymptotic giant branch stars below 20 per cent for z ≳ 5. While our suite of Milky Way-sized galaxies forms dust in good agreement with a number of key observables, it predicts a high dust-to-metal ratio in the circumgalactic medium, which motivates a more realistic treatment of thermal sputtering of grains and dust cooling channels.

  16. A Submillimeter Continuum Survey of Local Dust-obscured Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Jong Chul; Hwang, Ho Seong; Lee, Gwang-Ho

    2016-12-01

    We conduct a 350 μm dust continuum emission survey of 17 dust-obscured galaxies (DOGs) at z = 0.05-0.08 with the Caltech Submillimeter Observatory (CSO). We detect 14 DOGs with S 350 μm = 114-650 mJy and signal-to-noise > 3. By including two additional DOGs with submillimeter data in the literature, we are able to study dust content for a sample of 16 local DOGs, which consist of 12 bump and four power-law types. We determine their physical parameters with a two-component modified blackbody function model. The derived dust temperatures are in the range 57-122 K and 22-35 K for the warm and cold dust components, respectively. The total dust mass and the mass fraction of the warm dust component are 3-34 × 107 M ⊙ and 0.03%-2.52%, respectively. We compare these results with those of other submillimeter-detected infrared luminous galaxies. The bump DOGs, the majority of the DOG sample, show similar distributions of dust temperatures and total dust mass to the comparison sample. The power-law DOGs show a hint of smaller dust masses than other samples, but need to be tested with a larger sample. These findings support that the reason DOGs show heavy dust obscuration is not an overall amount of dust content, but probably the spatial distribution of dust therein.

  17. A Submillimeter Survey of Dust Continuum Emission in Local Dust-Obscured Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Jong Chul; Hwang, Ho Seong; Lee, Gwang-Ho

    2015-08-01

    Dusty star-forming galaxies are responsible for the bulk of cosmic star formation at 1galaxies is far from clear because of their extreme distances. The study of their local analogs helps us to improve understanding of the drivers of the intense star formation activity at high redshift. The submillimeter data on the 'Rayleigh-Jeans' side of the infrared spectral energy distributions (SEDs) of these galaxies are crucial for deriving the physical parameters of the dust content. We therefore conduct a submillimeter survey of local dust-obscured galaxies (DOGs) with the Caltech Submillimeter Observatory and the Submillimeter Array to study their dust properties. We determine the dust masses and temperatures for 16 local DOGs from the SED fit, and compare them with other dusty galaxies to understand a possible evolutionary link among them.

  18. Mapping Dust through Emission and Absorption in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Kreckel, Kathryn; Groves, Brent; Schinnerer, Eva; Johnson, Benjamin D.; Aniano, Gonzalo; Calzetti, Daniela; Croxall, Kevin V.; Draine, Bruce T.; Gordon, Karl D.; Crocker, Alison F.; Dale, Daniel A.; Hunt, Leslie K.; Kennicutt, Robert C.; Meidt, Sharon E.; Smith, J. D. T.; Tabatabaei, Fatemeh S.

    2013-07-01

    Dust has long been identified as a barrier to measuring inherent galaxy properties. However, the link between dust and attenuation is not straightforward and depends on both the amount of dust and its distribution. Herschel imaging of nearby galaxies undertaken as part of the KINGFISH project allows us to map the dust as seen in emission with unprecedented sensitivity and ~1 kpc resolution. We present here new optical integral field unit spectroscopy for eight of these galaxies that provides complementary 100-200 pc scale maps of the dust attenuation through observation of the reddening in both the Balmer decrement and the stellar continuum. The stellar continuum reddening, which is systematically less than that observed in the Balmer decrement, shows no clear correlation with the dust, suggesting that the distribution of stellar reddening acts as a poor tracer of the overall dust content. The brightest H II regions are observed to be preferentially located in dusty regions, and we do find a correlation between the Balmer line reddening and the dust mass surface density for which we provide an empirical relation. Some of the high-inclination systems in our sample exhibit high extinction, but we also find evidence that unresolved variations in the dust distribution on scales smaller than 500 pc may contribute to the scatter in this relation. We caution against the use of integrated AV measures to infer global dust properties.

  19. Molecular gas, dust, and star formation in galaxies. I. Dust properties and scalings in 1600 nearby galaxies

    NASA Astrophysics Data System (ADS)

    Orellana, G.; Nagar, N. M.; Elbaz, D.; Calderón-Castillo, P.; Leiton, R.; Ibar, E.; Magnelli, B.; Daddi, E.; Messias, H.; Cerulo, P.; Slater, R.

    2017-06-01

    Context. Dust and its emission is increasingly being used to constrain the evolutionary stage of a galaxy. A comprehensive characterization of dust, best achieved in nearby bright galaxies, is thus a highly useful resource. Aims: We aim to characterize the relationship between dust properties (mass, luminosity, and temperature) and their relationships with galaxy-wide properties (stellar, atomic, and molecular gas mass, and star formation mode). We also aim to provide equations to accurately estimate dust properties from limited observational datasets. Methods: We assemble a sample of 1630 nearby (z < 0.1) galaxies - over a large range of stellar masses (M∗), star formation rates (SFR) and specific star formation rates (sSFR = SFR/M∗) - for which comprehensive and uniform multi-wavelength observations are available from WISE, IRAS, Planck, and/or SCUBA. The characterization of dust emission comes from spectral energy distribution (SED) fitting using Draine & Li (2007, ApJ, 657, 810) dust models, which we parametrize using two components (warm at 45-70 K and cold at 18-31 K). The subsample of these galaxies with global measurements of CO and/or HI are used to explore the molecular and/or atomic gas content of the galaxies. Results: The total infrared luminosity (LIR), dust mass (Mdust), and dust temperature of the cold component (Tcold) form a plane that we refer to as the dust plane. A galaxy's sSFR drives its position on the dust plane: starburst (high sSFR) galaxies show higher LIR , Mdust , and Tcold compared to main sequence (typical sSFR) and passive galaxies (low sSFR). Starburst galaxies also show higher specific dust masses (Mdust/M∗) and specific gas masses (Mgas/M∗). We confirm earlier findings of an anti-correlation between the dust to stellar mass ratio and M∗ . We also find different anti-correlations depending on sSFR; the anti-correlation becomes stronger as the sSFR increases, with the spread due to different cold dust temperatures. The

  20. Far-reaching dust distribution in galaxy discs

    NASA Astrophysics Data System (ADS)

    Smith, Matthew W. L.; Eales, Stephen A.; De Looze, Ilse; Baes, Maarten; Bendo, George J.; Bianchi, Simone; Boquien, Médéric; Boselli, Alessandro; Buat, Veronique; Ciesla, Laure; Clemens, Marcel; Clements, David L.; Cooray, Asantha R.; Cortese, Luca; Davies, Jonathan I.; Fritz, Jacopo; Gomez, Haley L.; Hughes, Thomas M.; Karczewski, Oskar Ł.; Lu, Nanyao; Oliver, Seb J.; Remy-Ruyer, Aurélie; Spinoglio, Luigi; Viaene, Sebastien

    2016-10-01

    In most studies of dust in galaxies, dust is only detected from its emission to approximately the optical radius of the galaxy. By combining the signal of 110 spiral galaxies observed as part of the Herschel Reference Survey, we are able to improve our sensitivity by an order of magnitude over that for a single object. Here we report the direct detection of dust from its emission that extends out to at least twice the optical radius. We find that the distribution of dust is consistent with an exponential at all radii with a gradient of ˜-1.7 dex R_{25}^{-1}. Our dust temperature declines linearly from ˜25 K in the centre to 15 K at R25 from where it remains constant out to ˜2.0 R25. The surface density of dust declines with radius at a similar rate to the surface density of stars but more slowly than the surface density of the star-formation rate. Studies based on dust extinction and reddening of high-redshift quasars have concluded that there are substantial amounts of dust in intergalactic space. By combining our results with the number counts and angular correlation function from the SDSS, we show that with Milky Way-type dust we can explain the reddening of the quasars by the dust within galactic discs alone. Given the uncertainties in the properties of any intergalactic dust, we cannot rule out its existence, but our results show that statistical investigations of the dust in galactic haloes that use the reddening of high-redshift objects must take account of the dust in galactic discs.

  1. The rarity of dust in metal-poor galaxies.

    PubMed

    Fisher, David B; Bolatto, Alberto D; Herrera-Camus, Rodrigo; Draine, Bruce T; Donaldson, Jessica; Walter, Fabian; Sandstrom, Karin M; Leroy, Adam K; Cannon, John; Gordon, Karl

    2014-01-09

    Galaxies observed at redshift z > 6, when the Universe was less than a billion years old, thus far very rarely show evidence of the cold dust that accompanies star formation in the local Universe, where the dust-to-gas mass ratio is around one per cent. A prototypical example is the galaxy Himiko (z = 6.6), which--a mere 840 million years after the Big Bang--is forming stars at a rate of 30-100 solar masses per year, yielding a mass assembly time of about 150 × 10(6) years. Himiko is thought to have a low fraction (2-3 per cent of the Sun's) of elements heavier than helium (low metallicity), and although its gas mass cannot yet be determined its dust-to-stellar mass ratio is constrained to be less than 0.05 per cent. The local dwarf galaxy I Zwicky 18, which has a metallicity about 4 per cent that of the Sun's and is forming stars less rapidly (assembly time about 1.6 × 10(9) years) than Himiko but still vigorously for its mass, is also very dust deficient and is perhaps one of the best analogues of primitive galaxies accessible to detailed study. Here we report observations of dust emission from I Zw 18, from which we determine its dust mass to be 450-1,800 solar masses, yielding a dust-to-stellar mass ratio of about 10(-6) to 10(-5) and a dust-to-gas mass ratio of 3.2-13 × 10(-6). If I Zw 18 is a reasonable analogue of Himiko, then Himiko's dust mass must be around 50,000 solar masses, a factor of 100 below the current upper limit. These numbers are quite uncertain, but if most high-z galaxies are more like Himiko than like the very-high-dust-mass galaxy SDSS J114816.64 + 525150.3 at z ≈ 6, which hosts a quasar, then our prospects for detecting the gas and dust inside such galaxies are much poorer than hitherto anticipated.

  2. AN INFRARED CENSUS OF DUST IN NEARBY GALAXIES WITH SPITZER (DUSTINGS). I. OVERVIEW

    SciTech Connect

    Boyer, Martha L.; Sonneborn, George; McQuinn, Kristen B. W.; Gehrz, Robert D.; Skillman, Evan; Barmby, Pauline; Bonanos, Alceste Z.; Gordon, Karl D.; Meixner, Margaret; Groenewegen, M. A. T.; Lagadec, Eric; Lennon, Daniel; Marengo, Massimo; Sloan, G. C.; Van Loon, Jacco Th.; Zijlstra, Albert

    2015-01-01

    Nearby resolved dwarf galaxies provide excellent opportunities for studying the dust-producing late stages of stellar evolution over a wide range of metallicity (–2.7 ≲ [Fe/H] ≲ –1.0). Here, we describe DUSTiNGS (DUST in Nearby Galaxies with Spitzer): a 3.6 and 4.5 μm post-cryogen Spitzer Space Telescope imaging survey of 50 dwarf galaxies within 1.5 Mpc that is designed to identify dust-producing asymptotic giant branch (AGB) stars and massive stars. The survey includes 37 dwarf spheroidal, 8 dwarf irregular, and 5 transition-type galaxies. This near-complete sample allows for the building of statistics on these rare phases of stellar evolution over the full metallicity range. The photometry is >75% complete at the tip of the red giant branch for all targeted galaxies, with the exception of the crowded inner regions of IC 10, NGC 185, and NGC 147. This photometric depth ensures that the majority of the dust-producing stars, including the thermally pulsing AGB stars, are detected in each galaxy. The images map each galaxy to at least twice the half-light radius to ensure that the entire evolved star population is included and to facilitate the statistical subtraction of background and foreground contamination, which is severe at these wavelengths. In this overview, we describe the survey, the data products, and preliminary results. We show evidence for the presence of dust-producing AGB stars in eight of the targeted galaxies, with metallicities as low as [Fe/H] = –1.9, suggesting that dust production occurs even at low metallicity.

  3. Evolution of dust extinction curves in galaxy simulation

    NASA Astrophysics Data System (ADS)

    Hou, Kuan-Chou; Hirashita, Hiroyuki; Nagamine, Kentaro; Aoyama, Shohei; Shimizu, Ikkoh

    2017-07-01

    To understand the evolution of extinction curve, we calculate the dust evolution in a galaxy using smoothed particle hydrodynamic simulations incorporating stellar dust production, dust destruction in supernova shocks, grain growth by accretion and coagulation, and grain disruption by shattering. The dust species are separated into carbonaceous dust and silicate. The evolution of grain size distribution is considered by dividing grain population into large and small grains, which allows us to estimate extinction curves. We examine the dependence of extinction curves on the position, gas density and metallicity in the galaxy, and find that extinction curves are flat at t ≲ 0.3 Gyr because stellar dust production dominates the total dust abundance. The 2175 Å bump and far-ultraviolet (FUV) rise become prominent after dust growth by accretion. At t ≳ 3 Gyr, shattering works efficiently in the outer disc and low-density regions, so extinction curves show a very strong 2175 Å bump and steep FUV rise. The extinction curves at t ≳ 3 Gyr are consistent with the Milky Way extinction curve, which implies that we successfully included the necessary dust processes in the model. The outer disc component caused by stellar feedback has an extinction curve with a weaker 2175 Å bump and flatter FUV slope. The strong contribution of carbonaceous dust tends to underproduce the FUV rise in the Small Magellanic Cloud extinction curve, which supports selective loss of small carbonaceous dust in the galaxy. The snapshot at young ages also explains the extinction curves in high-redshift quasars.

  4. Dust and Molecular Gas in the Winds of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    McCormick, Alexander N.

    Galactic winds provide a fundamental mechanism for galaxy evolution. The outflow of material in winds remains the most likely culprit responsible for a host of galaxy observations, plus mounting evidence for galactic winds at times in the past points to their importance in understanding the history of the universe. Therefore, detailed observations of galactic winds are critical to fleshing out the narrative of galaxy evolution. In particular, the dust and molecular gas of a galaxy's interstellar medium (ISM) play crucial roles in the absorption, scattering, and reemission of starlight, the heating of the ISM, and provide critical materials for star formation. We present results from archival Spitzer Space Telescope ata and exceptionally deep Herschel Space Observatory data of the dust and molecular gas found in and around 20 nearby galaxies known to host galactic-scale winds. Selecting nearby galaxies has allowed us the resolution and sensitivity to differentiate dust and molecular gas outside the galaxies and observe their typically faint emission. These are the most detailed surveys currently available of the faint dust and molecular gas components in galactic winds, and we have utilized them to address the following questions: i) What are the location and morphology of dust and molecular gas, and how do these components compare with better known neutral and ionized gas features? ii) How much do dust and molecular gas contribute to the mass and energy of galactic winds? iii) Do the properties of the dust and molecular gas correlate with the properties of the wind-hosting galaxy? Spitzer archival data has revealed kiloparsec-scale polycyclic aromatic hydrocarbon (PAH) structures in the extraplanar regions of nearly all the wind-hosting galaxies we investigated. We found a nearly linear correlation between the extraplanar PAH emission and the total infrared flux, a proxy for star formation. Our results also suggest a correlation between the height of extraplanar

  5. Dust In Hell: Discovery Of Dust In Hot Gas Around Group-Centered Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Temi, Pasquale; Brighenti, F.; Mathews, W. G.

    2007-05-01

    Observations with the Spitzer infrared telescope reveal extended internally produced dust in the hot gas (KT 1 KeV) atmospheres surrounding two optically normal galaxies, NGC 5044 and NGC 4636. We interpret this as a dusty buoyant outflow resulting from energy released by gas accretion onto supermassive black holes in the galaxy cores. Both galaxies have highly disturbed, transient activities in the hot gas and contain strong dust emission at 70 and 160 microns in excess of what expected from normal stellar mass loss. The 70 micron image is clearly extended. The lifetime of dust in hot (KT=1KeV) interstellar gas to destruction by sputtering (ion impacts), 10 million years, establishes the time when the dust first entered the hot gas. Remarkably, in NGC 5044 we observe interstellar PAH dust-molecular emission at 8 microns out to about 5 Kpc that is spatially coincident with extended Halpha+[NII] emission from warm gas. We propose that this dust comes from the destruction and heating of dusty disks in the nuclei of these galaxies, followed by buoyant transport. A simple calculation shows that dust-assisted cooling in outflowing buoyant gas in NGC 5044 can cool the gas within a few Kpc in about 10 million years, explaining the optical line emission observed.

  6. Dust effects on LGRB host galaxies in cosmological simulations

    NASA Astrophysics Data System (ADS)

    Bignone, L. A.; Pellizza, L. J.; Tissera, P. B.

    2016-08-01

    The very energetic long gamma-ray bursts (LGRBs) constitute an extremely important tool to study the cosmological evolution of the Universe up to very high redshift. In this work we study the properties of LGRB host galaxies using numerical simulations of galaxy formation. We combine the galaxy catalogue of a hydrodynamical cosmological simulation with a model for LGRBs, which includes constrains for the mass and metallicity of their progenitors. This allows us to analyse the chemical and physical properties of both LGRBs and their hosts. A current problem is to disentangle the bias introduced on the observed host properties by a possible metallicity dependence of the progenitors, from the selection effects produced by dust obscuration in the hosts. We explore this issue by modelling the effect of dust in host galaxies, using radiative transfer codes. In this work we present preliminary results of this research line.

  7. DUST PROPERTIES OF LOCAL DUST-OBSCURED GALAXIES WITH THE SUBMILLIMETER ARRAY

    SciTech Connect

    Hwang, Ho Seong; Andrews, Sean M.; Geller, Margaret J. E-mail: sandrews@cfa.harvard.edu

    2013-11-01

    We report Submillimeter Array observations of the 880 μm dust continuum emission for four dust-obscured galaxies (DOGs) in the local universe. Two DOGs are clearly detected with S{sub ν}(880 μm) =10-13 mJy and S/N > 5, but the other two are not detected with 3σ upper limits of S{sub ν}(880 μm) =5-9 mJy. Including an additional two local DOGs with submillimeter data from the literature, we determine the dust masses and temperatures for six local DOGs. The infrared luminosities and dust masses for these DOGs are in the ranges of 1.2-4.9 × 10{sup 11}(L{sub ☉}) and 4-14 × 10{sup 7}(M{sub ☉}), respectively. The dust temperatures derived from a two-component modified blackbody function are 23-26 K and 60-124 K for the cold and warm dust components, respectively. Comparison of local DOGs with other infrared luminous galaxies with submillimeter detections shows that the dust temperatures and masses do not differ significantly among these objects. Thus, as argued previously, local DOGs are not a distinctive population among dusty galaxies, but simply represent the high-end tail of the dust obscuration distribution.

  8. Production, Processing, and Consumption of Dust in the Galaxy

    NASA Astrophysics Data System (ADS)

    Gontcharov, G.

    2017-06-01

    The recent results obtained by the modern telescopes and spacecrafts allow us for the first time to compare directly the mass, spatial density and size distribution of the dust grains in the regions of their production, processing and consumption in our Galaxy. The ALMA and VLT/SPHERE telescopes allow us to estimate the production of the dust by supergiants and collapsing core supernovae. The 2MASS, WISE, SDSS, Planck and other telescopes allow us to estimate the processing of the dust in the interstellar medium. After renewed Besançon Galaxy model the medium appears to contain about half the local mass of matter (both baryonic and dark) in the Galactic neighborhood of the Sun. The Helios, Ulysses, Galileo, Cassini and New Horizons spacecrafts allow us to estimate the consumption of the dust by large solid bodies. The results are consistent assuming the local mean spatial density of the dust is about of 3.5×10-26 g/cm3, mean density of the grain is about 1 g/cm3, and the dust production rate is about of 0.015 Solar mass per year for whole the Galaxy.

  9. Dust in the Circumgalactic Medium of Low-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Peek, J. E. G.; Ménard, Brice; Corrales, Lia

    2015-11-01

    Using spectroscopically selected galaxies from the Sloan Digital Sky Survey we present a detection of reddening effects from the circumgalactic medium of galaxies which we attribute to an extended distribution of dust. We detect the mean change in the colors of “standard crayons” correlated with the presence of foreground galaxies at z˜ 0.05 as a function of angular separation. Following Peek & Graves, we create standard crayons using passively evolving galaxies corrected for Milky Way reddening and color-redshift trends, leading to a sample with as little as 2% scatter in color. We devise methods to ameliorate possible systematic effects related to the estimation of colors, and we find an excess reddening induced by foreground galaxies at a level ranging from 10 to 0.5 mmag on scales ranging from 30 kpc to 1 Mpc. We attribute this effect to a large-scale distribution of dust around galaxies similar to the findings of Ménard et al. We find that circumgalactic reddening is a weak function of stellar mass over the range 6× {10}9 {M}⊙ -6× {10}10 {M}⊙ and note that this behavior appears to be consistent with recent results on the distribution of metals in the gas phase. We also find that circumgalactic reddening has no detectable dependence on the specific star formation rate of the host galaxy.

  10. Simulating Galaxy Clusters with Dust Formation and Evolution

    NASA Astrophysics Data System (ADS)

    Gjergo, Eda; Granato, Gian Luigi; Murante, Giuseppe; Ragone-Figueroa, Cinthia

    2017-07-01

    In order to investigate basic properties of galaxies, such as the star formation rate and the masses of baryonic components, it is important to account for dust reprocessing. Dust particles absorb and scatter the stars' optical/UV emission, and they re-radiate thermally in the infrared. A combination of simulations and post-processing radiative transfer computations can produce mock data, which can be compared directly to observations. Until now, however, dust properties have only been included in our simulations by means of post-processing assumptions, leaving room for uncertainties, particularly significant at wavelengths shorter than 100 microns. To reduce these uncertainties, we implemented a state-of-the-art treatment of the production and evolution of dust grains within our simulation code, P-GADGET3. This model traces the creation, evolution, and destruction of dust through various processes. It accounts for the diameter of dust particles with a two-grain-size approximation proposed by H. Hirashita. We will present a first result of our new code applied to zoom-in simulations of massive (M_{200} > 3 × 10^4 M_{⊙}) galaxy clusters, focusing in particular to the early stages of assembly of the cluster at high redshift, around z = 2, where the SF activity is at its maximum and the proto-cluster regions are rich of cold, dust-polluted gas.

  11. DUST OBSCURATION IN LYMAN BREAK GALAXIES AT z {approx} 4

    SciTech Connect

    Ho, I-Ting; Wang, Wei-Hao; Morrison, Glenn E.; Miller, Neal A. E-mail: itho@asiaa.sinica.edu.t

    2010-10-20

    Measuring star formation rates (SFRs) in high-z galaxies with their rest-frame ultraviolet (UV) continuum can be uncertain because of dust obscuration. Prior studies had used the submillimeter emission at 850 {mu}m to determine the intrinsic SFRs of rest-frame UV-selected galaxies, but the results suffered from the low sensitivity and poor resolution ({approx}15''). Here, we use ultradeep Very Large Array 1.4 GHz images with {approx}1''-2'' resolutions to measure the intrinsic SFRs. We perform stacking analyses in the radio images centered on {approx}3500 Lyman break galaxies (LBGs) at z {approx} 4 in the Great Observatories Origins Deep Survey-North and South fields selected with Hubble Space Telescope/Advanced Camera for Surveys data. The stacked radio flux is very low, 0.08 {+-} 0.15 {mu}Jy, implying a mean SFR of 6 {+-} 11 M{sub sun} yr{sup -1}. This is comparable to the uncorrected mean UV SFRs of {approx}5 M{sub sun} yr{sup -1}, implying that the z {approx} 4 LBGs have little dust extinction. The low SFR and dust extinction support the previous results that z {approx} 4 LBGs are in general not submillimeter galaxies. We further show that there is no statistically significant excess of dust-hidden star-forming components within {approx}22 kpc from the LBGs.

  12. INFRARED LUMINOSITIES AND DUST PROPERTIES OF z approx 2 DUST-OBSCURED GALAXIES

    SciTech Connect

    Bussmann, R. S.; Dey, Arjun; Jannuzi, B. T.; Borys, C.; Desai, V.; Sheth, K.; Soifer, B. T.; Le Floc'h, E.; Melbourne, J.

    2009-11-01

    We present SHARC-II 350 mum imaging of twelve 24 mum bright (F{sub 24m}u{sub m} > 0.8 mJy) Dust-Obscured Galaxies (DOGs) and Combined Array for Research in Millimeter-wave Astronomy (CARMA) 1 mm imaging of a subset of two DOGs. These objects are selected from the Booetes field of the NOAO Deep Wide-Field Survey. Detections of four DOGs at 350 mum imply infrared (IR) luminosities which are consistent to within a factor of 2 of expectations based on a warm-dust spectral energy distribution (SED) scaled to the observed 24 mum flux density. The 350 mum upper limits for the 8 non-detected DOGs are consistent with both Mrk 231 and M82 (warm-dust SEDs), but exclude cold dust (Arp 220) SEDs. The two DOGs targeted at 1 mm were not detected in our CARMA observations, placing strong constraints on the dust temperature: T{sub dust} > 35-60 K. Assuming these dust properties apply to the entire sample, we find dust masses of approx3 x 10{sup 8} M{sub sun}. In comparison to other dusty z approx 2 galaxy populations such as submillimeter galaxies (SMGs) and other Spitzer-selected high-redshift sources, this sample of DOGs has higher IR luminosities (2 x 10{sup 13} L{sub sun} versus 6 x 10{sup 12} L{sub sun} for the other galaxy populations) that are driven by warmer dust temperatures (>35-60 K versus approx30 K) and lower inferred dust masses (3 x 10{sup 8} M{sub sun} versus 3 x 10{sup 9} M{sub sun}). Wide-field Herschel and Submillimeter Common-User Bolometer Array-2 surveys should be able to detect hundreds of these power-law-dominated DOGs. We use the existing Hubble Space Telescope and Spitzer/InfraRed Array Camera data to estimate stellar masses of these sources and find that the stellar to gas mass ratio may be higher in our 24 mum bright sample of DOGs than in SMGs and other Spitzer-selected sources. Although much larger sample sizes are needed to provide a definitive conclusion, the data are consistent with an evolutionary trend in which the formation of massive galaxies

  13. Time evolution of interstellar dust and far-infrared luminosity of disk galaxies

    NASA Technical Reports Server (NTRS)

    Wang, Boqi

    1991-01-01

    The evolution of interstellar dust in disk galaxies is modeled, assuming that dust forms predominantly in molecular clouds associated with star formation. Analytical solutions for the dust abundance in disk galaxies as a function of galaxy age are obtained for the prompt initial enrichment and accretion models of chemical evolution, consistent with observations of the heavy element abundance in the Galaxy. Star formation rates in the disks of galaxies are taken as either constant or decreasing exponentially with time. It is found that the total amount of dust in the early history of galaxies can be up to 4 times the value observed today. The total emission from dust in galaxies is calculated, using an average dust temperature derived from IRAS observations. In the strongly evolving models, the far-infrared luminosity from galaxies can be roughly two orders of magnitude larger than the current value.

  14. DUST ATTENUATION IN HIGH REDSHIFT GALAXIES: 'DIAMONDS IN THE SKY'

    SciTech Connect

    Scoville, Nick; Capak, Peter; Steinhardt, Charles; Faisst, Andreas; Kakazu, Yuko; Li, Gongjie

    2015-02-20

    We use observed optical to near-infrared spectral energy distributions (SEDs) of 266 galaxies in the COSMOS survey to derive the wavelength dependence of the dust attenuation at high redshift. All of the galaxies have spectroscopic redshifts in the range z = 2-6.5. The presence of the C IV absorption feature, indicating that the rest-frame UV-optical SED is dominated by OB stars, is used to select objects for which the intrinsic, unattenuated spectrum has a well-established shape. Comparison of this intrinsic spectrum with the observed broadband photometric SED then permits derivation of the wavelength dependence of the dust attenuation. The derived dust attenuation curve is similar in overall shape to the Calzetti curve for local starburst galaxies. We also see the 2175 Å bump feature which is present in the Milky Way and Large Magellanic Cloud extinction curves but not seen in the Calzetti curve. The bump feature is commonly attributed to graphite or polycyclic aromatic hydrocarbons. No significant dependence is seen with redshift between sub-samples at z = 2-4 and z = 4-6.5. The 'extinction' curve obtained here provides a firm basis for color and extinction corrections of high redshift galaxy photometry.

  15. Characterizing Dust Attenuation in Local Star Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Battisti, Andrew; Calzetti, Daniela; Chary, Ranga-Ram

    2017-01-01

    The dust attenuation for a sample of ~10000 local (z ≤ 0.1) star forming galaxies is constrained as a function of their physical properties. We utilize aperture-matched multi-wavelength data from the UV-to-NIR, available from the Galaxy Evolution Explorer, the Sloan Digital Sky Survey, the United Kingdom Infrared Telescope, and the Two Micron All-Sky Survey, to ensure that regions of comparable size in each galaxy are being analyzed. We characterize the dust attenuation through the slope of the UV flux density and the Balmer decrement (Hα/Hβ). The observed relationship between these quantities is similar to the local starburst relation and is not seen to vary strongly with galactic properties. We derive the total attenuation curve over the range 1250 Å < λ < 28500 Å and find that a single attenuation curve is effective for characterizing the majority of galaxies in our sample. This attenuation curve is slightly lower in the far-UV than local starburst galaxies, by roughly 15%, but appears similar at longer wavelengths and has a normalization of RV = 3.7±0.4 (V-band). This indicates that a single attenuation curve is reasonable for wide application in the local Universe.

  16. Dust emission in simulated dwarf galaxies using GRASIL-3D

    NASA Astrophysics Data System (ADS)

    Santos-Santos, I. M.; Domínguez-Tenreiro, R.; Granato, G. L.; Brook, C. B.; Obreja, A.

    2017-03-01

    Recent Herschel observations of dwarf galaxies have shown a wide diversity in the shapes of their IR-submm spectral energy distributions as compared to more massive galaxies, presenting features that cannot be explained with the current models. In order to understand the physics driving these differences, we have computed the emission of a sample of simulated dwarf galaxies using the radiative transfer code GRASIL-3D. This code separately treats the radiative transfer in dust grains from molecular clouds and cirri. The simulated galaxies have masses ranging from 10^6-10^9 M_⊙ and have evolved within a Local Group environment by using CLUES initial conditions. We show that their IR band luminosities are in agreement with observations, with their SEDs reproducing naturally the particular spectral features observed. We conclude that the GRASIL-3D two-component model gives a physical interpretation to the emission of dwarf galaxies, with molecular clouds (cirri) as the warm (cold) dust components needed to recover observational data.

  17. Modelling galaxy spectra in presence of interstellar dust - III. From nearby galaxies to the distant Universe

    NASA Astrophysics Data System (ADS)

    Cassarà, L. P.; Piovan, L.; Chiosi, C.

    2015-07-01

    Improving upon the standard evolutionary population synthesis technique, we present spectrophotometric models of galaxies with morphology going from spherical structures to discs, properly accounting for the effect of dust in the interstellar medium (ISM). The models contain three main physical components: the diffuse ISM made of gas and dust, the complexes of molecular clouds where active star formation occurs, and stars of any age and chemical composition. These models are based on robust evolutionary chemical description providing the total amount of gas and stars present at any age, and matching the properties of galaxies of different morphological types. We have considered the results obtained by Piovan et al. for the properties of the ISM, and those by Cassarà et al. for the spectral energy distribution (SED) of single stellar populations, both in presence of dust, to model the integral SEDs of galaxies of different morphological types, going from pure bulges to discs passing through a number of composite systems with different combinations of the two components. The first part of the paper is devoted to recall the technical details of the method and the basic relations driving the interaction between the physical components of the galaxy. Then, the main parameters are examined and their effects on the SED of three prototype galaxies are highlighted. The theoretical SEDs nicely match the observational ones both for nearby galaxies and those at high redshift.

  18. Modeling Dust Evolution in Galaxies with a Multiphase, Inhomogeneous ISM

    NASA Astrophysics Data System (ADS)

    Zhukovska, Svitlana; Dobbs, Clare; Jenkins, Edward B.; Klessen, Ralf S.

    2016-11-01

    We develop a model of dust evolution in a multiphase, inhomogeneous interstellar medium (ISM) using hydrodynamical simulations of giant molecular clouds in a Milky Way-like spiral galaxy. We improve the treatment of dust growth by accretion in the ISM to investigate the role of the temperature-dependent sticking coefficient and ion-grain interactions. From detailed observational data on the gas-phase Si abundances [{{Si}}{gas}/{{H}}] measured in the local Galaxy, we derive a relation between the average [{{Si}}{gas}/{{H}}] and the local gas density n({{H}}) that we use as a critical constraint for the models. This relation requires a sticking coefficient that decreases with the gas temperature. The relation predicted by the models reproduces the slope of -0.5 for the observed relation in cold clouds, which is steeper than that for the warm medium and is explained by dust growth. We find that growth occurs in the cold medium for all adopted values of the minimum grain size a min from 1 to 5 nm. For the classical cutoff of {a}\\min =5 {nm}, the Coulomb repulsion results in slower accretion and higher [{{Si}}{gas}/{{H}}] than the observed values. For {a}\\min ≲ 3 {nm}, the Coulomb interactions enhance the growth rate, steepen the slope of the [{{Si}}{gas}/{{H}}]-n({{H}}) relation, and provide a better match to observations. The rates of dust re-formation in the ISM by far exceed the rates of dust production by stellar sources. After the initial 140 Myr, the cycle of matter in and out of dust reaches a steady state, in which the dust growth balances the destruction on a similar timescale of 350 Myr.

  19. Are dusty galaxies blue? Insights on UV attenuation from dust-selected galaxies

    SciTech Connect

    Casey, C. M.; Cooray, A.; Scoville, N. Z.; Sanders, D. B.; Lee, N.; Finkelstein, S. L.; Capak, P.; Conley, A.; De Zotti, G.; Farrah, D.; Fu, H.; Le Floc'h, E.; Ilbert, O.; Ivison, R. J.; Takeuchi, T. T.

    2014-12-01

    Galaxies' rest-frame ultraviolet (UV) properties are often used to directly infer the degree to which dust obscuration affects the measurement of star formation rates (SFRs). While much recent work has focused on calibrating dust attenuation in galaxies selected at rest-frame ultraviolet wavelengths, locally and at high-z, here we investigate attenuation in dusty, star forming galaxies (DSFGs) selected at far-infrared wavelengths. By combining multiwavelength coverage across 0.15-500 μm in the COSMOS field, in particular making use of Herschel imaging, and a rich data set on local galaxies, we find an empirical variation in the relationship between the rest-frame UV slope (β) and the ratio of infrared-to-ultraviolet emission (L {sub IR}/L {sub UV} ≡ IRX) as a function of infrared luminosity, or total SFR. Both locally and at high-z, galaxies above SFR ≳ 50 M {sub ☉} yr{sup –1} deviate from the nominal IRX-β relation toward bluer colors by a factor proportional to their increasing IR luminosity. We also estimate contamination rates of DSFGs on high-z dropout searches of <<1% at z ≲ 4-10, providing independent verification that contamination from very dusty foreground galaxies is low in Lyman-break galaxy searches. Overall, our results are consistent with the physical interpretation that DSFGs, e.g., galaxies with >50 M {sub ☉} yr{sup –1}, are dominated at all epochs by short-lived, extreme burst events, producing many young O and B stars that are primarily, yet not entirely, enshrouded in thick dust cocoons. The blue rest-frame UV slopes of DSFGs are inconsistent with the suggestion that most DSFGs at z ∼ 2 exhibit steady-state star formation in secular disks.

  20. RADIAL DISTRIBUTION OF STARS, GAS, AND DUST IN SINGS GALAXIES. II. DERIVED DUST PROPERTIES

    SciTech Connect

    Munoz-Mateos, J. C.; Gil de Paz, A.; Zamorano, J. E-mail: agpaz@astrax.fis.ucm.es

    2009-08-20

    We present a detailed analysis of the radial distribution of dust properties in the SINGS sample, performed on a set of ultraviolet (UV), infrared (IR), and H I surface brightness profiles, combined with published molecular gas profiles and metallicity gradients. The internal extinction, derived from the total-IR (TIR)-to-far-UV (FUV) luminosity ratio, decreases with radius, and is larger in Sb-Sbc galaxies. The TIR-to-FUV ratio correlates with the UV spectral slope {beta}, following a sequence shifted to redder UV colors with respect to that of starbursts. The star formation history (SFH) is identified as the main driver of this departure. Both L {sub TIR}/L {sub FUV} and {beta} correlate well with metallicity, especially in moderately face-on galaxies. The relation shifts to redder colors with increased scatter in more edge-on objects. By applying physical dust models to our radial spectral energy distributions, we have derived radial profiles of the total dust mass surface density, the fraction of the total dust mass contributed by polycyclic aromatic hydrocarbons (PAHs), and the intensity of the radiation field heating the grains. The dust profiles are exponential, their radial scale length being constant from Sb to Sd galaxies (only {approx}10% larger than the stellar scale length). Many S0/a-Sab galaxies have central depressions in their dust radial distributions. The PAH abundance increases with metallicity for 12 + log(O/H) < 9, and at larger metallicities the trend flattens and even reverses, with the SFH being a plausible underlying driver for this behavior. The dust-to-gas ratio is also well correlated with metallicity and therefore decreases with galactocentric radius. Although most of the total emitted IR power (especially in the outer regions of disks) is contributed by dust grains heated by diffuse starlight with a similar intensity as the local Milky Way radiation field, a small amount of the dust mass ({approx}1%) is required to be exposed to very

  1. The Cosmological Evolution of Dust and Gas in Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Archibald, E. N.

    The main epoch of activity for active galactic nuclei appears to have been z~2. Until very recently, the suspected symbiotic link between star formation, galaxy mergers and nuclear activity led people to believe that star formation activity in the Universe also peaked at z~2, despite the failure of searches to find a primeval galaxy at z>1. When a large population of star-forming galaxies was finally discovered at z>2, the astronomical community believed it had entered a new era of understanding how and when most of the stars of the Universe were formed. However, the star-formation rates observed in these systems are relatively modest, a few tens of solar masses per year, and are unable to build a massive elliptical galaxy in anything less than a Hubble time. Furthermore, the stellar populations in local massive ellipticals appear to have been formed in a short-lived, violent, dusty starburst at high-redshift, although it is not clear whether the formation trigger is a galaxy merger or the collapse of a huge halo of gas. The large quantities of dust that are expected during formation will absorb the optical/ultraviolet emission of the young stellar population and re-emit it in the far-infrared waveband. Locally, all powerful radio sources reside in massive elliptical hosts. It is therefore natural to assume that high-redshift radio galaxies are the progenitors or earlier examples of these local systems. This thesis presents a study of the evolution of dust and gas (and hence star formation) in massive ellipticals. A sample of 47 luminous, steep-spectrum, lobe-dominated radio galaxies spanning a wide range of redshifts, 0.77dust emission expected during star-formation episodes at early epochs will be redshifted into the submillimetre waveband, and the strong negative K-correction associated with the

  2. The problematic growth of dust in high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Ferrara, A.; Viti, S.; Ceccarelli, C.

    2016-11-01

    Dust growth via accretion of gas species has been proposed as the dominant process to increase the amount of dust in galaxies. We show here that this hypothesis encounters severe difficulties that make it unfit to explain the observed UV and IR properties of such systems, particularly at high redshifts. Dust growth in the diffuse ISM phases is hampered by (a) too slow accretion rates, (b) too high dust temperatures, and (c) the Coulomb barrier that effectively blocks accretion. In molecular clouds these problems are largely alleviated. Grains are cold (but not colder than the CMB temperature, TCMB ≈ 20 K at redshift z = 6). However, in dense environments accreted materials form icy water mantles, perhaps with impurities. Mantles are immediately (≲1 yr) photo-desorbed as grains return to the diffuse ISM at the end of the cloud lifetime, thus erasing any memory of the growth. We conclude that dust attenuating stellar light at high-z must be ready-made stardust largely produced in supernova ejecta.

  3. Supernovae Detection in Dust Extinguished Galaxies - A Spitzer Survey

    NASA Astrophysics Data System (ADS)

    Casper, Chadwick F.; Dosovitz Fox, Ori; Li, Gary; Filippenko, Alexei

    2016-01-01

    The rate at which supernovae (SNe) occur in ultraluminous infrared galaxies (ULIRGs) is explained by theory. However, past optical surveys of these galaxies have revealed a number 3 to 10 times lower than the number predicted. These surveys used ground-based radio and near-IR observations, but had a number of shortcomings including poor resolution and inability to detect high extinction events. The Spitzer Space Telescope (SST) offers several advantages over these ground-based surveys. First, the SST is able to maintain stable seeing in space. Furthermore, another advantage is at the longer wavelengths provided by Spitzer, the SNe in the nuclear regions of galaxies are less susceptible to extinction effects from dust. In order to detect the SNe through the heavy dust fields in ULIRGs, observations were taken at 3.6 μm with the warm IRAC camera on the SST. Here we present preliminary results from our SST survey of 40 ULIRGs. We describe the sensitivity of the survey given our current detection algorithm, which is limited in large part by an asymmetric Point Spread Function. Ultimately, we explore whether the 'missing' SNe can be accounted for by an extinction from the nucleus.

  4. Host Galaxies of Young Dust-Reddened Quasars

    NASA Astrophysics Data System (ADS)

    Urrutia, T.; Lacy, M.; Becker, R.; Glikman, E.

    2009-10-01

    We present results on a multiwavelength campaign to identify the nature of dust-reddened Type 1 quasars. These quasars were selected by matching FIRST, 2MASS and very red optical counterparts with r'-K > 5. We find a very high fraction of Low Ionization Broad Absorption Line Quasars (LoBALs) among AGN selected with this method, perhaps a sign of quasar feedback. From X-ray observations and Balmer decrement measurements, the obscuring dust is most likely located in a cold absorber such as the host galaxy, rather than from a torus near the AGN. Hubble ACS imaging of a sub-sample of these sources showed a very high fraction of interacting and merging systems. The quasars appear to be very young in which dust from the merging galaxies is still settling in. Spitzer IRS and MIPS data show star formation signatures and deep Silicate absorption features in these objects, but overall the quasar is the dominant source in the Mid-infrared.

  5. What can the occult do for you? Understanding dust geometry in other galaxies from overlapping galaxy pairs.

    NASA Astrophysics Data System (ADS)

    Holwerda, Benne Willem

    2015-08-01

    Interstellar dust is still the dominant uncertainty in Astronomy, limiting precision in e.g., cosmological distance estimates and models of how light is re-processed within a galaxy. When a foreground galaxy serendipitously overlaps a more distant one, the latter backlights the dusty structures in the nearer foreground galaxy. Such an overlapping or occulting galaxy pair can be used to measure the distribution of dust in the closest galaxy with great accuracy. My STARSMOG program uses HST observation of occulting galaxy pairs to accurately map the distribution of dust in foreground galaxies in fine (<100 pc) detail.The primary motivation is threefold: first, almost half of the light from stars in spiral galaxies is absorbed by the interstellar dust grains and re-emitted at longer wavelengths. To model this accurately, one needs to know the distribution and detailed geometry of dust in galaxies. The travel of light through an inhomogeneous medium is radically different from the smooth one and depends strongly on the medium’s inner structure. Secondly, the model for our Universe today includes dark energy, inferred from the distances to supernova, which themselves may be dimmed by intervening dust. An accurate model for the dust extinction in supernova host galaxies is critical to evolve this technique to the next level of accuracy needed to map dark energy. And finally, the fine-scale maps of dust extinction in occuling galaxies can be used to trace the molecular cloud sizes and the role of turbulence in the ISM of these disks. Furthermore, Integral Field Unit observations of such pairs will map the effective extinction curve in these occulting galaxies, disentangling the role of fine-scale geometry and grain composition on these curves.The overlapping galaxy technique promises to deliver a clear understanding of the dust in galaxies: the dust geometry, a probability function of the amount of dimming as a function of galaxy type, its dependence on wavelength and

  6. Gas-to-Dust Ratios in GRB Host Galaxies

    SciTech Connect

    Schady, P.; Page, M. J.; De Pasquale, M.; Mason, K. O.; Morris, D. C.; Roming, P. W. A.; Berk, D. E. van den; Oates, S. R.; Immler, S.

    2008-05-22

    An understanding of GRB host galaxy properties is pivotal to determining the progenitor stars, and is critical in identifying the effect of the GRB local environment on our observations. The imprint left by dust and gas absorption on GRB X-ray and optical afterglows provides an effective probe to the immediate surroundings, and for this well-sampled, multi-wavelength afterglow observations are imperative. Swift's capabilities to obtain simultaneous X-ray and UV/optical data make it ideal to study the dust and gas content in the local environment of GRBs. In these proceedings we further the work from [1], and present the results of analysis on the combined Swift and ground-based spectra of 24 GRB afterglows, which is the largest sample of GRB afterglow spectral energy distributions thus far studied.

  7. Dust and ionized gas in active radio elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Forbes, D. A.; Sparks, W. B.; Macchetto, F. D.

    1990-01-01

    The authors present broad and narrow bandwidth imaging of three southern elliptical galaxies which have flat-spectrum active radio cores (NGC 1052, IC 1459 and NGC 6958). All three contain dust and extended low excitation optical line emission, particularly extensive in the case of NGC 1052 which has a large H alpha + (NII) luminosity. Both NGC 1052 and IC 1459 have a spiral morphology in emission-line images. All three display independent strong evidence that a merger or infall event has recently occurred, i.e., extensive and infalling HI gas in NGC 1052, a counter-rotating core in IC 1459 and Malin-Carter shells in NGC 6958. This infall event is the most likely origin for the emission-line gas and dust, and the authors are currently investigating possible excitation mechanisms (Sparks et al. 1990).

  8. Using dust, gas and stellar mass-selected samples to probe dust sources and sinks in low-metallicity galaxies

    NASA Astrophysics Data System (ADS)

    De Vis, P.; Gomez, H. L.; Schofield, S. P.; Maddox, S.; Dunne, L.; Baes, M.; Cigan, P.; Clark, C. J. R.; Gomez, E. L.; Lara-López, M.; Owers, M.

    2017-10-01

    We combine samples of nearby galaxies with Herschel photometry selected on their dust, metal, H I and stellar mass content, and compare these to chemical evolution models in order to discriminate between different dust sources. In a companion paper, we used an H i-selected sample of nearby galaxies to reveal a subsample of very gas-rich (gas fraction >80 per cent) sources with dust masses significantly below predictions from simple chemical evolution models, and well below Md/M* and Md/Mgas scaling relations seen in dust and stellar-selected samples of local galaxies. We use a chemical evolution model to explain these dust-poor, but gas-rich, sources as well as the observed star formation rates (SFRs) and dust-to-gas ratios. We find that (i) a delayed star formation history is required to model the observed SFRs; (ii) inflows and outflows are required to model the observed metallicities at low gas fractions; (iii) a reduced contribution of dust from supernovae (SNe) is needed to explain the dust-poor sources with high gas fractions. These dust-poor, low stellar mass galaxies require a typical core-collapse SN to produce 0.01-0.16 M⊙ of dust. To match the observed dust masses at lower gas fractions, significant grain growth is required to counteract the reduced contribution from dust in SNe and dust destruction from SN shocks. These findings are statistically robust, though due to intrinsic scatter it is not always possible to find one single model that successfully describes all the data. We also show that the dust-to-metal ratio decreases towards lower metallicity.

  9. Dust evolution processes in normal galaxies at z > 6 detected by ALMA

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Chen; Hirashita, Hiroyuki; Hou, Kuan-Chou

    2017-03-01

    Recent Atacama Large Millimetre/submillimetre Array (ALMA) observations of high-redshift normal galaxies have been providing a great opportunity to clarify the general origin of dust in the Universe, not biased to very bright special objects even at z > 6. To clarify what constraint we can get for the dust enrichment in normal galaxies detected by ALMA, we use a theoretical model that includes major processes driving dust evolution in a galaxy; that is, dust condensation in stellar ejecta, dust growth by the accretion of gas-phase metals and supernova destruction. Using the dust emission fluxes detected in two normal galaxies at z > 6 by ALMA as a constraint, we can get the range of the time-scales (or efficiencies) of the above mentioned processes. We find that if we assume extremely high-condensation efficiency in stellar ejecta (fin ≳ 0.5), rapid dust enrichment by stellar sources in the early phase may be enough to explain the observed ALMA flux, unless dust destruction by supernovae in those galaxies is stronger than that in nearby galaxies. If we assume a condensation efficiency expected from theoretical calculations (fin ≲ 0.1), strong dust growth (even stronger than assumed for nearby galaxies if they are metal-poor galaxies) is required. These results indicate that the normal galaxies detected by ALMA at z > 6 are biased to objects (i) with high dust condensation efficiency in stellar ejecta, (ii) with strong dust growth in very dense molecular clouds or (iii) with efficient dust growth because of fast metal enrichment up to solar metallicity. A measurement of metallicity is crucial to distinguish among these possibilities.

  10. The cycle of interstellar dust in galaxies of different morphological types

    NASA Astrophysics Data System (ADS)

    Calura, F.; Pipino, A.; Matteucci, F.

    2008-03-01

    Aims:We used chemical evolution models for galaxies of different morphological type to perform a detailed study of the evolution of the cosmic dust properties in different environments: the solar neighbourhood, elliptical galaxies and dwarf irregular galaxies. Thanks to the uptodate observations available in the solar vicinity, we intend to study the effects of dust in the chemical evolution of different types of galaxies and, at the same time, to refine investigation of the parameter space to satisfactorily fine-tune the parameters in our study. Methods: We have considered dust production from low and intermediate mass stars, supernovae Ia, supernovae II, and both dust destruction and dust accretion processes in a detailed model of chemical evolution for the solar vicinity. Then, by means of the same dust prescriptions, but adopting different galactic models (different star formation histories and the presence of galactic winds), we extended our study to ellipticals and dwarf irregular galaxies. In all these systems, dust evolution was calculated by means of chemical evolution models that relax the instantaneous recycling approximation and already reproduce the main features of the various galaxies. Results: We have investigated how the assumption of different star formation histories affects the dust production rates, dust depletion, the dust accretion, and destruction rates. We predict dust-to-gas and dust-to-metal ratios in very good agreement with those observed in the solar vicinity. We show how the inclusion of the dust treatment is helpful in solving the so-called Fe discrepancy, as observed in the hot gaseous halos of local ellipticals, and in reproducing the chemical abundances observed in the Lyman Break Galaxies. Finally, our new models can be very useful in future detailed spectro-photometric studies of galaxies.

  11. Understanding The Baryonic Cycle: Confronting Galaxy Physics With The Mass; Metallicity Relation And Dust Content Of Galaxies Over Cosmic Time

    NASA Astrophysics Data System (ADS)

    Popping, Gergö; Somerville, Rachel; Galametz, Maud

    2016-09-01

    The mass-metallicity relation combines the star formation, metal enrichment, feedback, and baryon accretion history of galaxies and acts as a superb probe of the cycle of baryons through galaxies. Reproducing its cosmic evolution is a stringent constraint on models of galaxy formation. I will present new cosmological models of galaxy formation that include various ejective and preventive feedback schemes and detailed chemical evolution and dust chemistry models. I will present the impact of the different feedback schemes on the evolution of the mass;metallicity relation, compare my predictions with observations, and discuss how this comparison helps us constrain the galaxy physics acting on the baryonic cycle. I will further show that proper accounting for dust emphasizes a serious caveat in our understanding of galaxy formation. Galaxies are too metal enriched at early times.

  12. Dust-obscured galaxies in the local universe

    SciTech Connect

    Hwang, Ho Seong; Geller, Margaret J. E-mail: mgeller@cfa.harvard.edu

    2013-06-01

    We use Wide-field Infrared Survey Explorer (WISE), AKARI, and Galaxy Evolution Explorer (GALEX) data to select local analogs of high-redshift (z ∼ 2) dust obscured galaxies (DOGs). We identify 47 local DOGs with S {sub 12μm}/S {sub 0.22μm} ≥ 892 and S {sub 12μm} > 20 mJy at 0.05 < z < 0.08 in the Sloan Digital Sky Survey data release 7. The infrared (IR) luminosities of these DOGs are in the range 3.4 × 10{sup 10} (L {sub ☉}) ≲ L {sub IR} ≲ 7.0 × 10{sup 11} (L {sub ☉}) with a median L {sub IR} of 2.1 × 10{sup 11} (L {sub ☉}). We compare the physical properties of local DOGs with a control sample of galaxies that have lower S {sub 12μm}/S {sub 0.22μm} but have similar redshift, IR luminosity, and stellar mass distributions. Both WISE 12 μm and GALEX near-ultraviolet (NUV) flux densities of DOGs differ from the control sample of galaxies, but the difference is much larger in the NUV. Among the 47 DOGs, 36% ± 7% have small axis ratios in the optical (i.e., b/a < 0.6), larger than the fraction among the control sample (17% ± 3%). There is no obvious sign of interaction for many local DOGs. No local DOGs have companions with comparable optical magnitudes closer than ∼50 kpc. The large- and small-scale environments of DOGs are similar to the control sample. Many physical properties of local DOGs are similar to those of high-z DOGs, even though the IR luminosities of local objects are an order of magnitude lower than for the high-z objects: the presence of two classes (active galactic nuclei- and star formation-dominated) of DOGs, abnormal faintness in the UV rather than extreme brightness in the mid-IR, and diverse optical morphology. These results suggest a common underlying physical origin of local and high-z DOGs. Both seem to represent the high-end tail of the dust obscuration distribution resulting from various physical mechanisms rather than a unique phase of galaxy evolution.

  13. Linking dust emission to fundamental properties in galaxies: the low-metallicity picture

    NASA Astrophysics Data System (ADS)

    Rémy-Ruyer, A.; Madden, S. C.; Galliano, F.; Lebouteiller, V.; Baes, M.; Bendo, G. J.; Boselli, A.; Ciesla, L.; Cormier, D.; Cooray, A.; Cortese, L.; De Looze, I.; Doublier-Pritchard, V.; Galametz, M.; Jones, A. P.; Karczewski, O. Ł.; Lu, N.; Spinoglio, L.

    2015-10-01

    Aims: In this work, we aim to provide a consistent analysis of the dust properties from metal-poor to metal-rich environments by linking them to fundamental galactic parameters. Methods: We consider two samples of galaxies: the Dwarf Galaxy Survey (DGS) and the Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel (KINGFISH), totalling 109 galaxies, spanning almost 2 dex in metallicity. We collect infrared (IR) to submillimetre (submm) data for both samples and present the complete data set for the DGS sample. We model the observed spectral energy distributions (SED) with a physically-motivated dust model to access the dust properties: dust mass, total-IR luminosity, polycyclic aromatic hydrocarbon (PAH) mass fraction, dust temperature distribution, and dust-to-stellar mass ratio. Results: Using a different SED model (modified black body), different dust composition (amorphous carbon in lieu of graphite), or a different wavelength coverage at submm wavelengths results in differences in the dust mass estimate of a factor two to three, showing that this parameter is subject to non-negligible systematic modelling uncertainties. We find half as much dust with the amorphous carbon dust composition. For eight galaxies in our sample, we find a rather small excess at 500 μm (≤1.5σ). We find that the dust SED of low-metallicity galaxies is broader and peaks at shorter wavelengths compared to more metal-rich systems, a sign of a clumpier medium in dwarf galaxies. The PAH mass fraction and dust temperature distribution are found to be driven mostly by the specific star formation rate, sSFR, with secondary effects from metallicity. The correlations between metallicity and dust mass or total-IR luminosity are direct consequences of the stellar mass-metallicity relation. The dust-to-stellar mass ratios of metal-rich sources follow the well-studied trend of decreasing ratio for decreasing sSFR. The relation is more complex for low-metallicity galaxies with high

  14. A Controlled Study of Cold Dust Content in Galaxies from z = 0-2

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, Allison; Pope, Alexandra; Sajina, Anna; Dale, Daniel A.; Díaz-Santos, Tanio; Hayward, Christopher C.; Shi, Yong; Somerville, Rachel S.; Stierwalt, Sabrina; Armus, Lee; Kartaltepe, Jeyhan S.; Kocevski, Dale D.; McIntosh, Daniel H.; Sanders, David B.; Yan, Lin

    2017-07-01

    At z=1{--}3, the formation of new stars is dominated by dusty galaxies whose far-IR emission indicates they contain colder dust than local galaxies of a similar luminosity. We explore the reasons for the evolving IR emission of similar galaxies over cosmic time using (1) local galaxies from GOALS ({L}{IR}={10}11{--}{10}12 {L}⊙ ), (2) galaxies at z˜ 0.1{--}0.5 from 5MUSES ({L}{IR}={10}10{--}{10}12 {L}⊙ ), and (3) IR luminous galaxies spanning z=0.5{--}3 from GOODS and Spitzer xFLS ({L}{IR}> {10}11 {L}⊙ ). All samples have Spitzer mid-IR spectra, and Herschel and ground-based submillimeter imaging covering the full IR spectral energy distribution, allowing us to robustly measure {L}{IR}{SF}, {T}{dust}, and {M}{dust} for every galaxy. Despite similar infrared luminosities, z> 0.5 dusty star-forming galaxies (DSFG) have a factor of 5 higher dust masses and 5 K colder temperatures. The increase in dust mass is linked to an increase in the gas fractions with redshift, and we do not observe a similar increase in stellar mass or star formation efficiency. {L}160{SF}/{L}70{SF}, a proxy for {T}{dust}, is strongly correlated with {L}{IR}{SF}/{M}{dust} independently of redshift. We measure merger classification and galaxy size for a subsample, and there is no obvious correlation between these parameters and {L}{IR}{SF}/{M}{dust} or {L}160{SF}/{L}70{SF}. In DSFG, the change in {L}{IR}{SF}/{M}{dust} can fully account for the observed colder dust temperatures, suggesting that any change in the spatial extent of the interstellar medium is a second-order effect.

  15. Spatially resolved dust emission of extremely metal-poor galaxies*

    NASA Astrophysics Data System (ADS)

    Zhou, Luwenjia; Shi, Yong; Diaz-Santos, Taino; Armus, Lee; Helou, George; Stierwalt, Sabrina; Li, Aigen

    2016-05-01

    We present infrared (IR) spectral energy distributions (SEDs) of individual star-forming regions in four extremely metal-poor (EMP) galaxies with metallicity Z ≲ Z⊙/10 as observed by the Herschel Space Observatory. With the good wavelength coverage of the SED, it is found that these EMP star-forming regions show distinct SED shapes as compared to those of grand design Spirals and higher metallicity dwarfs: they have on average much higher f70μm/f160 μm ratios at a given f160 μm/f250 μm ratio; single modified blackbody (MBB) fittings to the SED at λ ≥ 100 μm still reveal higher dust temperatures and lower emissivity indices compared to that of Spirals, while two MBB fittings to the full SED with a fixed emissivity index (β = 2) show that even at 100 μm, about half of the emission comes from warm (50 K) dust, in contrast to the cold (˜20 K) dust component. Our spatially resolved images furthermore reveal that the far-IR colours including f70 μm/f160 μm, f160 μm/f250 μm and f250 μm/f350 μm are all related to the surface densities of young stars as traced by far-UV, 24 μm and star formation rates (SFRs), but not to the stellar mass surface densities. This suggests that the dust emitting at wavelengths from 70 to 350 μm is primarily heated by radiation from young stars.

  16. THE OBSERVED RELATION BETWEEN STELLAR MASS, DUST EXTINCTION, AND STAR FORMATION RATE IN LOCAL GALAXIES

    SciTech Connect

    Zahid, H. J.; Kewley, L. J.; Kudritzki, R. P.; Yates, R. M.

    2013-02-15

    In this study, we investigate the relation between stellar mass, dust extinction, and star formation rate (SFR) using {approx}150,000 star-forming galaxies from SDSS DR7. We show that the relation between dust extinction and SFR changes with stellar mass. For galaxies at the same stellar mass, dust extinction is anti-correlated with the SFR at stellar masses <10{sup 10} M {sub Sun }. There is a sharp transition in the relation at a stellar mass of 10{sup 10} M {sub Sun }. At larger stellar masses, dust extinction is positively correlated with the SFR for galaxies at the same stellar mass. The observed relation between stellar mass, dust extinction, and SFR presented in this study helps to confirm similar trends observed in the relation between stellar mass, metallicity, and SFR. The relation reported in this study provides important new constraints on the physical processes governing the chemical evolution of galaxies. The correlation between SFR and dust extinction for galaxies with stellar masses >10{sup 10} M {sub Sun} is shown to extend to the population of quiescent galaxies suggesting that the physical processes responsible for the observed relation between stellar mass, dust extinction, and SFR may be related to the processes leading to the shutdown of star formation in galaxies.

  17. Far-infrared and dust properties of present-day galaxies in the EAGLE simulations

    NASA Astrophysics Data System (ADS)

    Camps, Peter; Trayford, James W.; Baes, Maarten; Theuns, Tom; Schaller, Matthieu; Schaye, Joop

    2016-10-01

    The Evolution and Assembly of GaLaxies and their Environments (EAGLE) cosmological simulations reproduce the observed galaxy stellar mass function and many galaxy properties. In this work, we study the dust-related properties of present-day EAGLE galaxies through mock observations in the far-infrared and submm wavelength ranges obtained with the 3D dust radiative transfer code SKIRT. To prepare an EAGLE galaxy for radiative transfer processing, we derive a diffuse dust distribution from the gas particles and we re-sample the star-forming gas particles and the youngest star particles into star-forming regions that are assigned dedicated emission templates. We select a set of redshift-zero EAGLE galaxies that matches the K-band luminosity distribution of the galaxies in the Herschel Reference Survey (HRS), a volume-limited sample of about 300 normal galaxies in the Local Universe. We find overall agreement of the EAGLE dust scaling relations with those observed in the HRS, such as the dust-to-stellar mass ratio versus stellar mass and versus NUV-r colour relations. A discrepancy in the f250/f350 versus f350/f500 submm colour-colour relation implies that part of the simulated dust is insufficiently heated, likely because of limitations in our sub-grid model for star-forming regions. We also investigate the effect of adjusting the metal-to-dust ratio and the covering factor of the photodissociation regions surrounding the star-forming cores. We are able to constrain the important dust-related parameters in our method, informing the calculation of dust attenuation for EAGLE galaxies in the UV and optical domain.

  18. COLD DUST BUT WARM GAS IN THE UNUSUAL ELLIPTICAL GALAXY NGC 4125

    SciTech Connect

    Wilson, C. D.; Cridland, A.; Foyle, K.; Parkin, T. J.; Cooper, E. Mentuch; Roussel, H.; Sauvage, M.; Lebouteiller, V.; Madden, S.; Baes, M.; De Looze, I.; Bendo, G.; Boquien, M.; Boselli, A.; Ciesla, L.; Clements, D. L.; Cooray, A.; Galametz, M.; and others

    2013-10-20

    Data from the Herschel Space Observatory have revealed an unusual elliptical galaxy, NGC 4125, which has strong and extended submillimeter emission from cold dust but only very strict upper limits to its CO and H I emission. Depending on the dust emissivity, the total dust mass is 2-5 × 10{sup 6} M {sub ☉}. While the neutral gas-to-dust mass ratio is extremely low (<12-30), including the ionized gas traced by [C II] emission raises this limit to <39-100. The dust emission follows a similar r {sup 1/4} profile to the stellar light and the dust to stellar mass ratio is toward the high end of what is found in nearby elliptical galaxies. We suggest that NGC 4125 is currently in an unusual phase where evolved stars produced in a merger-triggered burst of star formation are pumping large amounts of gas and dust into the interstellar medium. In this scenario, the low neutral gas-to-dust mass ratio is explained by the gas being heated to temperatures ≥10{sup 4} K faster than the dust is evaporated. If galaxies like NGC 4125, where the far-infrared emission does not trace neutral gas in the usual manner, are common at higher redshift, this could have significant implications for our understanding of high redshift galaxies and galaxy evolution.

  19. The Origin of Dust in the Early Universe: Probing the Star Formation History of Galaxies by Their Dust Content

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Cherchneff, Isabelle

    2010-01-01

    Two distinct scenarios for the origin of the approximately 4 x 10(exp 8) Solar Mass of dust observed in the high-redshift (z = 6.4) quasar J1148+5251 have been proposed. The first assumes that this galaxy is much younger than the age of the universe at that epoch so that only supernovae, could have produced this dust. The second scenario assumes a significantly older galactic age, so that the dust could have formed in lower-mass AGB stars. Presenting new integral solutions for the chemical evolution of metals and dust in galaxies, we offer a critical evaluation of these two scenarios. ^N;"(,, show that the AGB scenario is sensitive to the details of the galaxy's star formation history (SFH), which must consist of an early intense starburst followed by a period of low stellar activity. The presence or absence of massive amounts of dust in high-redshift galaxies can therefore be used to infer their SFH. However, a problem with the AGB scenario is that it produces a stellar mass that is significantly larger than the inferred dynamical mass of J1148+5251, an yet unresolved discrepancy. If this problem persists, then additional sites for the growth or formation of dust, such as molecular clouds or dense clouds around active galactic nuclei, must be considered.

  20. A comparison of extinction curves for dust in galaxies of different Hubble types

    NASA Technical Reports Server (NTRS)

    Townsley, Leisa K.; Price, Jill S.

    1993-01-01

    A sample of 25 galaxies of various Hubble types has been observed in a variety of filters. Extinction curves have been generated for absorption regions in these galaxies using a technique which previously had been used on just a few galaxies; for example, NGC 205, NGC 185, NGC 3077, and M31. The results from these studies suggested that there may be systematic trends in dust properties with Hubble type. This would not be surprising; dust properties should vary with metallicity, for example. It is well known that some galaxies and their interstellar materials should reflect this difference.

  1. Scale Lengths in Disk Surface Brightness as Probes of Dust Extinction in Three Spiral Galaxies: M51, NGC 3631, and NGC 4321

    NASA Astrophysics Data System (ADS)

    Beckman, J. E.; Peletier, R. F.; Knapen, J. H.; Corradi, R. L. M.; Gentet, L. J.

    1996-08-01

    We have measured the radial brightness distributions in the disks of three nearby face-on spiral galaxies, M51, NGC 3631, and NGC 4321 (M100), in the photometric bands B through I, with the addition of the K band for M51 only. The measurements were made by averaging azimuthally, in three modes, the two-dimensional surface brightness over the disks in photometric images of the objects in each band: (1) over each disk as a whole, (2) over the spiral arms alone, and (3) over the interarm zones alone. From these profiles, scale lengths were derived for comparison with schematic exponential disk models that incorporate interstellar dust. These models include both absorption and scattering in their treatment of radiative transfer. The model fits show that the arms exhibit greater optical depth in dust than the interarm zones. The average fraction of emitted stellar light in V that is extinguished by dust within 3 scale lengths of the center of each galaxy does not rise above 20% in any of them. We show that this conclusion is also valid for models with similar overall quantities of dust but in which this is concentrated in lanes. These can also account for the observed scale lengths and their variations.

  2. The opacity of spiral galaxy disks: IX. Dust and gas surface densities

    NASA Astrophysics Data System (ADS)

    Holwerda, B. W.; Allen, R. J.; de Blok, W. J. G.; Bouchard, A.; González-Lópezlira, R. A.; van der Kruit, P. C.; Leroy, A.

    2013-03-01

    Our aim is to explore the relation between gas, atomic and molecular, and dust in spiral galaxies. Gas surface densities are from atomic hydrogen and CO line emission maps. To estimate the dust content, we use the disk opacity as inferred from the number of distant galaxies identified in twelve HST/WFPC2 fields of ten nearby spiral galaxies. The observed number of distant galaxies is calibrated for source confusion and crowding with artificial galaxy counts and here we verify our results with sub-mm surface brightnesses from archival Herschel-SPIRE data. We find that the opacity of the spiral disk does not correlate well with the surface density of atomic (H I) or molecular hydrogen (H_2) alone implying that dust is not only associated with the molecular clouds but also the diffuse atomic disk in these galaxies. Our result is a typical dust-to-gas ratio of 0.04, with some evidence that this ratio declines with galactocentric radius, consistent with recent Herschel results. We discuss the possible causes of this high dust-to-gas ratio; an over-estimate of the dust surface-density, an under-estimate of the molecular hydrogen density from CO maps or a combination of both. We note that while our value of the mean dust-to-gas ratio is high, it is consistent with the metallicity at the measured radii if one assumes the Pilyugin & Thuan (2005) calibration of gas metallicity.

  3. New insight into the relation between star formation activity and dust content in galaxies

    NASA Astrophysics Data System (ADS)

    da Cunha, Elisabete; Eminian, Celine; Charlot, Stéphane; Blaizot, Jérémy

    2010-04-01

    We assemble a sample of 3258 low-redshift galaxies from the Sloan Digital Sky Survey Data Release 6 with complementary photometric observations by the Galaxy Evolution Explorer, the Two Micron All Sky Survey and the Infrared Astronomical Satellite at far-ultraviolet and infrared wavelengths. We use a recent, simple but physically motivated model to interpret the observed spectral energy distributions of the galaxies in this sample in terms of statistical constraints on physical parameters describing the star formation history and dust content. The focus on a subsample of 1658 galaxies with highest signal-to-noise ratio observations enables us to investigate most clearly several strong correlations between various derived physical properties of galaxies. In particular, we find that the typical dust mass Md of a galaxy forming stars at a rate ψ can be estimated remarkably well using the formula over at least three orders of magnitude in both quantities. We also find that the dust-to-stellar mass ratio, the ratio of dust mass to star formation rate and the fraction of dust luminosity contributed by the diffuse interstellar medium (ISM) all correlate strongly with specific star formation rate. A comparison with recent models of chemical and dust evolution of galaxies suggests that these correlations could arise, at least in part, from an evolutionary sequence. As galaxies form stars, their ISM becomes enriched in dust, while the drop in gas supply makes the specific star formation rate decrease. Interestingly, as a result, a young, actively star-forming galaxy with low dust-to-gas ratio may still be highly dusty (in the sense of a high dust-to-stellar mass ratio) because it contains large amounts of interstellar gas. This may be important for the interpretation of the infrared emission from young, gas-rich star-forming galaxies at high redshift. The results presented in this paper should be especially useful to improve the treatment of the ISM properties of galaxies

  4. The interstellar medium in Andromeda's dwarf spheroidal galaxies - I. Content and origin of the interstellar dust

    NASA Astrophysics Data System (ADS)

    De Looze, Ilse; Baes, Maarten; Bendo, George J.; Fritz, Jacopo; Boquien, Médéric; Cormier, Diane; Gentile, Gianfranco; Kennicutt, Robert C.; Madden, Suzanne C.; Smith, Matthew W. L.; Young, Lisa

    2016-07-01

    Dwarf spheroidal galaxies are among the most numerous galaxy population in the Universe, but their main formation and evolution channels are still not well understood. The three dwarf spheroidal satellites (NGC 147, NGC 185, and NGC 205) of the Andromeda galaxy are characterized by very different interstellar medium properties, which might suggest them being at different galaxy evolutionary stages. While the dust content of NGC 205 has been studied in detail in an earlier work, we present new Herschel dust continuum observations of NGC 147 and NGC 185. The non-detection of NGC 147 in Herschel SPIRE maps puts a strong constraint on its dust mass (≤128^{+124}_{-68} M⊙). For NGC 185, we derive a total dust mass Md = 5.1±1.0 × 103 M⊙, which is a factor of ˜2-3 higher than that derived from ISO and Spitzer observations and confirms the need for longer wavelength observations to trace more massive cold dust reservoirs. We, furthermore, estimate the dust production by asymptotic giant branch (AGB) stars and supernovae (SNe). For NGC 147, the upper limit on the dust mass is consistent with expectations of the material injected by the evolved stellar population. In NGC 185 and NGC 205, the observed dust content is one order of magnitude higher compared to the estimated dust production by AGBs and SNe. Efficient grain growth, and potentially longer dust survival times (3-6 Gyr) are required to account for their current dust content. Our study confirms the importance of grain growth in the gas phase to account for the current dust reservoir in galaxies.

  5. Large and small-scale structures and the dust energy balance problem in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Saftly, W.; Baes, M.; De Geyter, G.; Camps, P.; Renaud, F.; Guedes, J.; De Looze, I.

    2015-04-01

    The interstellar dust content in galaxies can be traced in extinction at optical wavelengths, or in emission in the far-infrared. Several studies have found that radiative transfer models that successfully explain the optical extinction in edge-on spiral galaxies generally underestimate the observed FIR/submm fluxes by a factor of about three. In order to investigate this so-called dust energy balance problem, we use two Milky Way-like galaxies produced by high-resolution hydrodynamical simulations. We create mock optical edge-on views of these simulated galaxies (using the radiative transfer code SKIRT), and we then fit the parameters of a basic spiral galaxy model to these images (using the fitting code FitSKIRT). The basic model includes smooth axisymmetric distributions along a Sérsic bulge and exponential disc for the stars, and a second exponential disc for the dust. We find that the dust mass recovered by the fitted models is about three times smaller than the known dust mass of the hydrodynamical input models. This factor is in agreement with previous energy balance studies of real edge-on spiral galaxies. On the other hand, fitting the same basic model to less complex input models (e.g. a smooth exponential disc with a spiral perturbation or with random clumps), does recover the dust mass of the input model almost perfectly. Thus it seems that the complex asymmetries and the inhomogeneous structure of real and hydrodynamically simulated galaxies are a lot more efficient at hiding dust than the rather contrived geometries in typical quasi-analytical models. This effect may help explain the discrepancy between the dust emission predicted by radiative transfer models and the observed emission in energy balance studies for edge-on spiral galaxies.

  6. Dust properties of Lyman-break galaxies at z ~ 3

    NASA Astrophysics Data System (ADS)

    Álvarez-Márquez, J.; Burgarella, D.; Heinis, S.; Buat, V.; Lo Faro, B.; Béthermin, M.; López-Fortín, C. E.; Cooray, A.; Farrah, D.; Hurley, P.; Ibar, E.; Ilbert, O.; Koekemoer, A. M.; Lemaux, B. C.; Pérez-Fournon, I.; Rodighiero, G.; Salvato, M.; Scott, D.; Taniguchi, Y.; Vieira, J. D.; Wang, L.

    2016-03-01

    Context. Since the mid-1990s, the sample of Lyman-break galaxies (LBGs) has been growing thanks to the increasing sensitivities in the optical and in near-infrared telescopes for objects at z> 2.5. However, the dust properties of the LBGs are poorly known because the samples are small and/or biased against far-infrared (far-IR) or submillimeter (submm) observations. Aims: This work explores from a statistical point of view the far-IR and submm properties of a large sample of LBGs at z ~ 3 that cannot be individually detected from current far-IR observations. Methods: We select a sample of 22, 000 LBGs at 2.5 galaxies included in the sample allows us to split it into several bins as a function of UV luminosity (LFUV), UV continuum slope (βUV), and stellar mass (M∗) to better sample their variety. We stack in PACS (100 and 160 μm) images from PACS Evolution Probe survey (PEP), SPIRE (250, 350 and 500 μm) images from the Herschel Multi-tied Extragalactic Survey (HerMES) programs, and AzTEC (1.1 mm) images from the Atacama Submillimeter Telescope Experiment (ASTE). Our stacking procedure corrects the biases induced by galaxy clustering and incompleteness of our input catalogue in dense regions. Results: We obtain the full infrared spectral energy distributions (SED) of subsamples of LBGs and derive the mean IR luminosity as a function of LFUV, βUV, and M∗. The average IRX (or dust attenuation) is roughly constant over the LFUV range, with a mean of 7.9 (1.8 mag). However, it is correlated with βUV, AFUV = (3.15 ± 0.12) + (1.47 ± 0.14) βUV, and stellar mass, log (IRX) = (0.84 ± 0.11)log (M∗/ 1010.35) + 1.17 ± 0.05. We investigate using a statistically controlled stacking analysis as a function of (M∗, βUV), the dispersion of the IRX-βUV and IRX-M∗ plane. On the one hand, the dust attenuation shows a departure of up to 2.8 mag above the mean IRX-βUV relation when log (M

  7. Probing the interstellar dust in galaxies over >10 Gyr of cosmic history

    NASA Astrophysics Data System (ADS)

    Kulkarni, Varsha P.; Aller, Monique C.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam

    2016-11-01

    Dust has a profound effect on the physics and chemistry of the interstellar gas in galaxies and on the appearance of galaxies. Understanding the cosmic evolution of dust with time is therefore crucial for understanding the evolution of galaxies. Despite the importance of interstellar dust, very little is known about its nature and composition in distant galaxies. We summarize the results of our ongoing programs using observations of distant quasars to obtain better constraints on dust grains in foreground galaxies that happen to lie along the quasar sightlines. These observations consist of a combination of mid-infrared data obtained with the Spitzer Space Telescope and optical/UV data obtained with ground-based telescopes and/or the Hubble Space Telescope. The mid-IR data target the 10 μm and 18 μm silicate absorption features, while the optical/UV data allow determinations of element depletions, extinction curves, 2175 Å bumps, etc. Measurements of such properties in absorption-selected galaxies with redshifts ranging from z 0 to z > 2 provide constraints on the evolution of interstellar dust over the past > 10 Gyr . The optical depth of the 10 μm silicate absorption feature (τ10) in these galaxies is correlated with the amount of reddening along the sightline. But there are indications (e.g., based on the τ10 / E(B - V) ratio and possible grain crystallinity) that the dust in these distant galaxies differs in structure and composition from the dust in the Milky Way and the Magellanic Clouds. We briefly discuss the implications of these results for the evolution of galaxies and their star formation history.

  8. A new galactic chemical evolution model with dust: results for dwarf irregular galaxies and DLA systems

    NASA Astrophysics Data System (ADS)

    Gioannini, L.; Matteucci, F.; Vladilo, G.; Calura, F.

    2017-01-01

    We present a galactic chemical evolution model which adopts updated prescriptions for all the main processes governing the dust cycle. We follow in detail the evolution of the abundances of several chemical species (C, O, S, Si, Fe and Zn) in the gas and dust of a typical dwarf irregular galaxy. The dwarf irregular galaxy is assumed to evolve with a low but continuous level of star formation and experience galactic winds triggered by supernova (SN) explosions. We predict the evolution of the gas to dust ratio in such a galaxy and discuss critically the main processes involving dust, such as dust production by asymptotic giant branch stars and Type II SNe, destruction and accretion (gas condensation in clouds). We then apply our model to damped Lyman α (DLA) systems which are believed to be dwarf irregulars, as witnessed by their abundance patterns. Our main conclusions are the following. (i) We can reproduce the observed gas to dust ratio in dwarf galaxies. (ii) We find that the process of dust accretion plays a fundamental role in the evolution of dust and in certain cases it becomes the dominant process in the dust cycle. On the other hand, dust destruction seems to be a negligible process in irregulars. (iii) Concerning DLA systems, we show that the observed gas-phase abundances of silicon, normalized to volatile elements (zinc and sulfur), are in agreement with our model. (iv) The abundances of iron and silicon in DLA systems suggest that the two elements undergo a different history of dust formation and evolution. Our work casts light on the nature of iron-rich dust: the observed depletion pattern of iron is well reproduced only when an additional source of iron dust is considered. Here we explore the possibility of a contribution from Type Ia SNe as well as an efficient accretion of iron nanoparticles.

  9. The Herschel Virgo Cluster Survey. XIII. Dust in early-type galaxies

    NASA Astrophysics Data System (ADS)

    di Serego Alighieri, S.; Bianchi, S.; Pappalardo, C.; Zibetti, S.; Auld, R.; Baes, M.; Bendo, G.; Corbelli, E.; Davies, J. I.; Davis, T.; De Looze, I.; Fritz, J.; Gavazzi, G.; Giovanardi, C.; Grossi, M.; Hunt, L. K.; Magrini, L.; Pierini, D.; Xilouris, E. M.

    2013-04-01

    Aims: We study the dust content of a large optical input sample of 910 early-type galaxies (ETG) in the Virgo cluster, also extending to the dwarf ETG, and examine the results in relation to those on the other cold ISM components. Methods: We have searched for far-infrared emission in all galaxies in the input sample using the 250 μm image of the Herschel Virgo Cluster Survey (HeViCS). This image covers a large fraction of the cluster with an area of ~55 square degrees. For the detected ETG we measured fluxes in five bands from 100 to 500 μm, and estimated the dust mass and temperature with modified black-body fits. Results: Dust is detected above the completeness limit of 25.4 mJy at 250 μm in 46 ETG, 43 of which are in the optically complete part of the input sample. In addition, dust is present at fainter levels in another six ETG. We detect dust in the four ETG with synchrotron emission, including M 87. Dust appears to be much more concentrated than stars and more luminous ETG have higher dust temperatures. Considering only the optically complete input sample and correcting for the contamination by background galaxies, dust detection rates down to the 25.4 mJy limit are 17% for ellipticals, about 40% for lenticulars (S0 + S0a), and around 3% for dwarf ETG. Dust mass does not correlate clearly with stellar mass and is often much greater than expected for a passive galaxy in a closed-box model. The dust-to-stars mass ratio anticorrelates with galaxy luminosity, and for some dwarf ETG reaches values as high as for dusty late-type galaxies. In the Virgo cluster slow rotators appear more likely to contain dust than fast ones. Comparing the dust results with those on Hi there are only eight ETG detected both in dust and in Hi in the HeViCS area; 39 have dust but only an upper limit on Hi, and eight have Hi but only an upper limit on dust. The locations of these galaxies in the cluster are different, with the dusty ETG concentrated in the densest regions, while the

  10. Exploring the Dust Content of Galactic Winds with Herschel: Nearby Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    McCormick, Alexander; Veilleux, S.; Melendez, M.; Bland-Hawthorn, J.; Cecil, G.; Engelbracht, C.; Heitsch, F.; Martin, C. L.; Mueller, T.; Rupke, D.; Trippe, M.; Zastrow, J.

    2014-01-01

    Galactic-scale winds manifest as the "smoking gun" of negative feedback, an essential mechanism for understanding galaxy evolution. Negative feedback has been invoked to resolve a number of issues: the mass-metalicity relation of star-forming galaxies, the tight bulge - black hole mass relation, and the presence of metals in galaxy halos and the intergalactic and intracluster media. Although negative feedback may assert even greater influence at high redshift, where strong starbursts and active galactic nuclei are more commonplace, nearby sources provide the best opportunities for detailed observations of the resultant winds. In recent years, observations have begun to illuminate the less obvious components of galactic-scale winds, including dust and molecular gas. Investigating the spatial distribution and properties of the dust in concert with host galaxy characteristics will give insight into the physics of dust entrainment, outflow energetics, and why the dust survives far outside the host galaxy. We will present results from new, deep Herschel observations of several nearby dwarf galaxies with known galactic-scale winds. Our results will compare flux measurements and the spatial distribution of cold dust in the outflows with star formation properties of the host galaxies. We will also compare these new observations with archival Spitzer and previous H-alpha observations.

  11. Probing the dust properties of galaxies up to submillimetre wavelengths. I. The spectral energy distribution of dwarf galaxies using LABOCA

    NASA Astrophysics Data System (ADS)

    Galametz, M.; Madden, S.; Galliano, F.; Hony, S.; Schuller, F.; Beelen, A.; Bendo, G.; Sauvage, M.; Lundgren, A.; Billot, N.

    2009-12-01

    Aims. We study the dust properties of four low metallicity galaxies by modelling their spectral energy distributions. This modelling enables us to constrain the dust properties such as the mass, the temperature or the composition to characterise the global ISM properties in dwarf galaxies. Methods: We present 870 μm images of four low metallicity galaxies (NGC 1705, Haro 11, Mrk 1089 and UM 311) observed with the Large APEX BOlometer CAmera (LABOCA) on the Atacama Pathfinder EXperiment (APEX) telescope. We modeled their spectral energy distributions combining the submm observations of LABOCA, 2MASS, IRAS, Spitzer photometric data, and the IRS data for Haro 11. Results: We found that the PAH mass abundance is very low in these galaxies, 5 to 50 times lower than the PAH mass fraction of our Galaxy. We also found that a significant mass of dust is revealed when using submm constraints compared to that measured with only mid-IR to far-IR observations extending only to 160 μm. For NGC 1705 and Haro 11, an excess in submillimeter wavelengths was detected when we used our standard dust SED model. We rerun our SED procedure adding a cold dust component (10 K) to better describe the high 870 μm flux derived from LABOCA observations, which significantly improves the fit. We found that at least 70% of the dust mass of these two galaxies can reside in a cold dust component. We also showed that the subsequent dust-to-gas mass ratios, considering HI and CO observations, can be strikingly high for Haro 11 in comparison with what is usually expected for these low-metallicity environments. Furthermore, we derived the star formation rate of our galaxies and compared them to the Schmidt law. Haro 11 falls anomalously far from the Schmidt relation. These results may suggest that a reservoir of hidden gas could be present in molecular form not traced by the current CO observations. While there can be a significant cold dust mass found in Haro 11, the SED peaks at exceptionally short

  12. Galaxies at redshifts 5 to 6 with systematically low dust content and high [C II] emission.

    PubMed

    Capak, P L; Carilli, C; Jones, G; Casey, C M; Riechers, D; Sheth, K; Carollo, C M; Ilbert, O; Karim, A; LeFevre, O; Lilly, S; Scoville, N; Smolcic, V; Yan, L

    2015-06-25

    The rest-frame ultraviolet properties of galaxies during the first three billion years of cosmic time (redshift z > 4) indicate a rapid evolution in the dust obscuration of such galaxies. This evolution implies a change in the average properties of the interstellar medium, but the measurements are systematically uncertain owing to untested assumptions and the inability to detect heavily obscured regions of the galaxies. Previous attempts to measure the interstellar medium directly in normal galaxies at these redshifts have failed for a number of reasons, with two notable exceptions. Here we report measurements of the forbidden C ii emission (that is, [C II]) from gas, and the far-infrared emission from dust, in nine typical star-forming galaxies about one billion years after the Big Bang (z ≈ 5-6). We find that these galaxies have thermal emission that is less than 1/12 that of similar systems about two billion years later, and enhanced [C II] emission relative to the far-infrared continuum, confirming a strong evolution in the properties of the interstellar medium in the early Universe. The gas is distributed over scales of one to eight kiloparsecs, and shows diverse dynamics within the sample. These results are consistent with early galaxies having significantly less dust than typical galaxies seen at z < 3 and being comparable in dust content to local low-metallicity systems.

  13. Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

    NASA Astrophysics Data System (ADS)

    Aller, Monique C.; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli; Beiranvand, Nassim; Morrison, Sean

    Gas and dust grains are fundamental components of the interstellar medium and significantly impact many of the physical processes driving galaxy evolution, such as star-formation, and the heating, cooling, and ionization of the interstellar material. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous quasars, provide a valuable tool to directly study the properties of the interstellar gas and dust in distant, normal galaxies. We have established the presence of silicate dust grains in at least some gas-rich QASs, and find that they exist at higher optical depths than expected for diffuse gas in the Milky Way. Differences in the absorption feature shapes additionally suggest variations in the silicate dust grain properties, such as in the level of grain crystallinity, from system-to-system. We present results from a study of the gas and dust properties of QASs with adequate archival IR data to probe the silicate dust grain properties. We discuss our measurements of the strengths of the 10 and 18 μm silicate dust absorption features in the QASs, and constraints on the grain properties (e.g., composition, shape, crystallinity) based on fitted silicate profile templates. We investigate correlations between silicate dust abundance, reddening, and gas metallicity, which will yield valuable insights into the history of star formation and chemical enrichment in galaxies.

  14. Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

    NASA Technical Reports Server (NTRS)

    Aller, Monique C.; Dwek, Eliahu; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli; Beiranvand, Nassim; hide

    2016-01-01

    Gas and dust grains are fundamental components of the interstellar medium and significantly impact many of the physical processes driving galaxy evolution, such as star-formation, and the heating, cooling, and ionization of the interstellar material. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous quasars, provide a valuable tool to directly study the properties of the interstellar gas and dust in distant, normal galaxies. We have established the presence of silicate dust grains in at least some gas-rich QASs, and find that they exist at higher optical depths than expected for diffuse gas in the Milky Way. Differences in the absorption feature shapes additionally suggest variations in the silicate dust grain properties, such as in the level of grain crystallinity, from system-to-system. We present results from a study of the gas and dust properties of QASs with adequate archival IR data to probe the silicate dust grain properties. We discuss our measurements of the strengths of the 10 and 18 micron silicate dust absorption features in the QASs, and constraints on the grain properties (e.g., composition, shape, crystallinity) based on fitted silicate profile templates. We investigate correlations between silicate dust abundance, reddening, and gas metallicity, which will yield valuable insights into the history of star formation and chemical enrichment in galaxies.

  15. GLOBAL STAR FORMATION RATES AND DUST EMISSION OVER THE GALAXY INTERACTION SEQUENCE

    SciTech Connect

    Lanz, Lauranne; Zezas, Andreas; Smith, Howard A.; Ashby, Matthew L. N.; Fazio, Giovanni G.; Hernquist, Lars; Brassington, Nicola; Da Cunha, Elisabete; Hayward, Christopher C.; Jonsson, Patrik

    2013-05-01

    We measured and modeled spectral energy distributions (SEDs) in 28 bands from the ultraviolet to the far-infrared (FIR) for 31 interacting galaxies in 14 systems. The sample is drawn from the Spitzer Interacting Galaxy Survey, which probes a range of galaxy interaction parameters at multiple wavelengths with an emphasis on the infrared bands. The subset presented in this paper consists of all galaxies for which FIR Herschel SPIRE observations are publicly available. Our SEDs combine the Herschel photometry with multi-wavelength data from Spitzer, GALEX, Swift UVOT, and 2MASS. While the shapes of the SEDs are broadly similar across our sample, strongly interacting galaxies typically have more mid-infrared emission relative to their near-infrared and FIR emission than weakly or moderately interacting galaxies. We modeled the full SEDs to derive host galaxy star formation rates (SFRs), specific star formation rates (sSFRs), stellar masses, dust temperatures, dust luminosities, and dust masses. We find increases in the dust luminosity and mass, SFR, and cold (15-25 K) dust temperature as the interaction progresses from moderately to strongly interacting and between non-interacting and strongly interacting galaxies. We also find increases in the SFR between weakly and strongly interacting galaxies. In contrast, the sSFR remains unchanged across all the interaction stages. The ultraviolet photometry is crucial for constraining the age of the stellar population and the SFR, while dust mass is primarily determined by SPIRE photometry. The SFR derived from the SED modeling agrees well with rates estimated by proportionality relations that depend on infrared emission.

  16. Are High-redshift Galaxies Hot? Temperature of z > 5 Galaxies and Implications for Their Dust Properties

    NASA Astrophysics Data System (ADS)

    Faisst, Andreas L.; Capak, Peter L.; Yan, Lin; Pavesi, Riccardo; Riechers, Dominik A.; Barišić, Ivana; Cooke, Kevin C.; Kartaltepe, Jeyhan S.; Masters, Daniel C.

    2017-09-01

    Recent studies have found a significant evolution and scatter in the relationship between the UV spectral slope (β UV) and the infrared excess (IRX; L IR/L UV) at z > 4, suggesting different dust properties of these galaxies. The total far-infrared (FIR) luminosity is key for this analysis, but it is poorly constrained in normal (main-sequence) star-forming z > 5 galaxies, where often only one single FIR point is available. To better inform estimates of the FIR luminosity, we construct a sample of local galaxies and three low-redshift analogues of z > 5 systems. The trends in this sample suggest that normal high-redshift galaxies have a warmer infrared (IR) spectral energy distribution (SED) compared to average z < 4 galaxies that are used as priors in these studies. The blueshifted peak and mid-IR excess emission could be explained by a combination of a larger fraction of metal-poor interstellar medium being optically thin to ultraviolet (UV) light and a stronger UV radiation field due to high star formation densities. Assuming a maximally warm IR SED suggests a 0.6 dex increase in total FIR luminosities, which removes some tension between the dust attenuation models and observations of the IRX‑β relation at z > 5. Despite this, some galaxies still fall below the minimum IRX‑β relation derived with standard dust cloud models. We propose that radiation pressure in these highly star-forming galaxies causes a spatial offset between dust clouds and young star-forming regions within the lifetime of O/B stars. These offsets change the radiation balance and create viewing-angle effects that can change UV colors at fixed IRX. We provide a modified model that can explain the location of these galaxies on the IRX‑β diagram.

  17. DUST DISK AROUND A BLACK HOLE IN GALAXY NGC 4261

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is a Hubble Space Telescope image of an 800-light-year-wide spiral-shaped disk of dust fueling a massive black hole in the center of galaxy, NGC 4261, located 100 million light-years away in the direction of the constellation Virgo. By measuring the speed of gas swirling around the black hole, astronomers calculate that the object at the center of the disk is 1.2 billion times the mass of our Sun, yet concentrated into a region of space not much larger than our solar system. The strikingly geometric disk -- which contains enough mass to make 100,000 stars like our Sun -- was first identified in Hubble observations made in 1992. These new Hubble images reveal for the first time structure in the disk, which may be produced by waves or instabilities in the disk. Hubble also reveals that the disk and black hole are offset from the center of NGC 4261, implying some sort of dynamical interaction is taking place, that has yet to be fully explained. Credit: L. Ferrarese (Johns Hopkins University) and NASA Image files in GIF and JPEG format, captions, and press release text may be accessed on Internet via anonymous ftp from oposite.stsci.edu in /pubinfo:

  18. Herschel-ATLAS: rapid evolution of dust in galaxies over the last 5 billion years

    NASA Astrophysics Data System (ADS)

    Dunne, L.; Gomez, H. L.; da Cunha, E.; Charlot, S.; Dye, S.; Eales, S.; Maddox, S. J.; Rowlands, K.; Smith, D. J. B.; Auld, R.; Baes, M.; Bonfield, D. G.; Bourne, N.; Buttiglione, S.; Cava, A.; Clements, D. L.; Coppin, K. E. K.; Cooray, A.; Dariush, A.; de Zotti, G.; Driver, S.; Fritz, J.; Geach, J.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Jarvis, M. J.; Kelvin, L.; Pascale, E.; Pohlen, M.; Popescu, C.; Rigby, E. E.; Robotham, A.; Rodighiero, G.; Sansom, A. E.; Serjeant, S.; Temi, P.; Thompson, M.; Tuffs, R.; van der Werf, P.; Vlahakis, C.

    2011-10-01

    We present the first direct and unbiased measurement of the evolution of the dust mass function of galaxies over the past 5 billion years of cosmic history using data from the Science Demonstration Phase of the Herschel-Astrophysical Terahertz Large Area Survey (Herschel-ATLAS). The sample consists of galaxies selected at 250 ?m which have reliable counterparts from the Sloan Digital Sky Survey (SDSS) at z < 0.5, and contains 1867 sources. Dust masses are calculated using both a single-temperature grey-body model for the spectral energy distribution and also a model with multiple temperature components. The dust temperature for either model shows no trend with redshift. Splitting the sample into bins of redshift reveals a strong evolution in the dust properties of the most massive galaxies. At z= 0.4-0.5, massive galaxies had dust masses about five times larger than in the local Universe. At the same time, the dust-to-stellar mass ratio was about three to four times larger, and the optical depth derived from fitting the UV-sub-mm data with an energy balance model was also higher. This increase in the dust content of massive galaxies at high redshift is difficult to explain using standard dust evolution models and requires a rapid gas consumption time-scale together with either a more top-heavy initial mass function (IMF), efficient mantle growth, less dust destruction or combinations of all three. This evolution in dust mass is likely to be associated with a change in overall interstellar medium mass, and points to an enhanced supply of fuel for star formation at earlier cosmic epochs.

  19. Stellar Evolutionary Effects on the Abundances of PAH and SN-Condensed Dust in Galaxies

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2007-01-01

    Spectral and photometric observations of nearby galaxies show a correlation between the strength of their mid-IR aromatic features, attributed to PAH molecules, and their metal abundance, leading to a deficiency of these features in low-metallicity galaxies. We suggest that the observed correlation represents a trend of PAH abundance with galactic age, reflecting the delayed injection of carbon dust into the ISM by AGB stars in the final post-AGB phase of their evolution. We also show that larger dust particles giving rise to the far-IR emission follow a distinct evolutionary trend closely related to the injection of dust by massive stars into the ISM.

  20. Dust and gas in star-forming galaxies at z 3. Extending galaxy uniformity to 11.5 billion years

    NASA Astrophysics Data System (ADS)

    Magdis, G. E.; Rigopoulou, D.; Daddi, E.; Bethermin, M.; Feruglio, C.; Sargent, M.; Dannerbauer, H.; Dickinson, M.; Elbaz, D.; Gomez Guijarro, C.; Huang, J.-S.; Toft, S.; Valentino, F.

    2017-07-01

    We present millimetre dust emission measurements of two Lyman-break galaxies at z 3 and construct for the first time fully sampled infrared spectral energy distributions (SEDs), from mid-IR to the Rayleigh-Jeans tail, of individually detected, unlensed, UV-selected, main sequence (MS) galaxies at z = 3. The SED modelling of the two sources confirms previous findings, based on stacked ensembles, of an increasing mean radiation field ⟨ U ⟩ with redshift, consistent with a rapidly decreasing gas metallicity in z> 2 galaxies. Complementing our study with CO[J = 3 → 2] emission line observations, we have measured the molecular gas mass reservoir (MH2) of the systems using three independent approaches: 1) CO line observations; 2) the dust to gas mass ratio vs. metallicity relation; and 3) a single band, dust emission flux on the Rayleigh-Jeans side of the SED. All techniques return consistent MH2 estimates within a factor of two or less, yielding gas depletion time-scales (τdep ≈ 0.35 Gyr) and gas-to-stellar mass ratios (MH2/M∗ ≈ 0.5-1) for our z 3 massive MS galaxies. The overall properties of our galaxies are consistent with trends and relations established at lower redshifts, extending the apparent uniformity of star-forming galaxies over the last 11.5 billion years. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  1. High-resolution 3D dust radiative transfer in galaxies with DART-Ray

    NASA Astrophysics Data System (ADS)

    Natale, Giovanni; Popescu, Cristina C.; Tuffs, Richard. J.; Debattista, Victor P.; Grootes, Meiert W.

    2015-02-01

    DART-Ray is a 3D ray-tracing dust radiative transfer (RT) code that can be used to derive stellar and dust emission maps of galaxy models and simulations with arbitrary geometries. In addition to the previously published RT algorithm, we have now included in DART-Ray the possibility of calculating the stocastically heated dust emission from each volume element within a galaxy. To show the capabilities of the code, we performed a high-resolution (26 pc) RT calculation for a galaxy N-body+SPH simulation. The simulated galaxy we considered is characterized by a nuclear disc and a flocculent spiral structure. We analysed the derived galaxy maps for the global and local effects of dust on the galaxy attenuation as well as the contribution of scattered radiation to the predicted observed emission. In addition, by performing an additional RT calculation including only the stellar volume emissivity due to young stellar populations (SPs), we derived the contribution to the total dust emission powered by young and old SPs. Full details of this work will be presented in a forthcoming publication.

  2. Stellar Evolutionary Effects on the Abundance of PAHS and SN-Condensed Dust in Galaxies

    NASA Technical Reports Server (NTRS)

    Dwek, Eli

    2007-01-01

    Spectral aid photometric observations of nearby galaxies show a correlation between the strength of their mid-IR aromatic features and their metal abundance, and a deficiency of these features in low-metallicity galaxies. The aromatic features are most commonly attributed to emission from PAH molecules. In this paper, we suggest that the observed correlation represents a trend of PAH abundance with galactic age, reflecting the delayed injection of PAHs and carbon dust into the ISM, by AGB stars in their final, post-AGB phase of their evolution. These AGB stars are the primary sources of PAHs and carbon dust in galaxies, and recycle their ejecta back to the interstellar medium only after a few hundred million years of evolution on the main sequence. In contrast, more massive stars that explode as Type II supernovae inject their metals and dust almost instantaneously after their formation. After determining the PAH abundances in 35 nearby galaxies, we use a chemical evolution model to show that the delayed injection of carbon dust by AGB stars provides a natural explanation to the dependence of the PAH content, in galaxies with metallicity. We also show that larger dust particles giving rise to the far-IR emission follow a distinct evolutionary trend closely related to the injection of dust by massive stars into the ISM.

  3. How does metallicity affect the gas and dust properties of galaxies?

    NASA Astrophysics Data System (ADS)

    Madden, Suzanne C.; Cormier, Diane; Rémy-Ruyer, Aurélie

    Comparison of the ISM properties of a wide range of metal poor galaxies with normal metal-rich galaxies reveals striking differences. We find that the combination of the low dust abundance and the active star formation results in a very porous ISM filled with hard photons, heating the dust in dwarf galaxies to overall higher temperatures than their metal-rich counterparts. This results in photodissociation of molecular clouds to greater depths, leaving relatively large PDR envelopes and difficult-to-detect CO cores. From detailed modeling of the low-metallicity ISM, we find significant fractions of CO-dark H2 - a reservoir of molecular gas not traced by CO, but present in the [CII] and [CI]-emitting envelopes. Self-consistent analyses of the neutral and ionized gas diagnostics along with the dust SED is the necessary way forward in uncovering the multiphase structure of galaxies.

  4. Determining properties of halo dust for the Herschel EDGE-on galaxy Survey (HEDGES)

    NASA Astrophysics Data System (ADS)

    Pezzato, Jacklyn M.; Murphy, Eric J.

    2017-01-01

    The Herschel EDGE-on galaxy Survey (HEDGES) is studying the distribution of dust in the halos of nearby spiral galaxies. More specifically, its goals are to determine the physical characteristics of this dust, what relationship there might be between halo dust content and star formation activity, how halo dust might expose information about the far-infrared (FIR)-Radio correlation, and how the physical distribution of this dust might relate to that of other gas tracers. The work presented here aims to investigate the physical characteristics of this halo dust and how they change with height above and below the plane of the six galaxies in the HEDGES sample: NGC 0891, NGC 3628, NGC 4244, NGC 4517, NGC 4565 and NGC 4631. To achieve this goal, code has been written that, for each galaxy, can extract vertical profiles and photometric data from nine different bands (taken using the Herschel Space Observatory and the Spitzer Space Telescope) in the FIR part of the electromagnetic spectrum. These photometric data are then used to construct a spectral energy distribution (SED) that is fit to dust models.

  5. Far-infrared properties of Markarian galaxies with multiple nuclei - Warm dust emission in mergers

    NASA Technical Reports Server (NTRS)

    Mazzarella, Joseph M.; Bothun, Gregory D.; Boroson, Todd A.

    1991-01-01

    An investigation of coadded IRAS data is performed on 187 Markarian galaxies where distinguishing morphological characteristics or multiple optical nuclei are present. The far-IR properties of Markarian galaxies are compared to the IRAS Bright Galaxy Sample, and a much higher median dust temperature is found in the multiple nucleus galaxies, suggesting that more far-IR luminosity results from active star formation. Both optical/UV and far-IR selection techniques are necessary to extract complete samples of AGNs since the far-IR two-color plane can miss up to 50 percent of the galaxies. A systematic increase in the contribution of warm dust emission due to active star formation and AGNs is found in a statistical comparison of merger candidates and other galaxy samples. The assumed nature of precursor galaxies determines the assumed enhancement of far-IR luminosity caused by galaxy collisions. A model is presented which describes the properties of the Markarian galaxies in terms of enhanced OB star formation and different grain size distributions. The results of the investigation are shown to be consistent with a 'subdued' interpretation of merging galaxies with high luminosities.

  6. Far-infrared properties of Markarian galaxies with multiple nuclei - Warm dust emission in mergers

    NASA Technical Reports Server (NTRS)

    Mazzarella, Joseph M.; Bothun, Gregory D.; Boroson, Todd A.

    1991-01-01

    An investigation of coadded IRAS data is performed on 187 Markarian galaxies where distinguishing morphological characteristics or multiple optical nuclei are present. The far-IR properties of Markarian galaxies are compared to the IRAS Bright Galaxy Sample, and a much higher median dust temperature is found in the multiple nucleus galaxies, suggesting that more far-IR luminosity results from active star formation. Both optical/UV and far-IR selection techniques are necessary to extract complete samples of AGNs since the far-IR two-color plane can miss up to 50 percent of the galaxies. A systematic increase in the contribution of warm dust emission due to active star formation and AGNs is found in a statistical comparison of merger candidates and other galaxy samples. The assumed nature of precursor galaxies determines the assumed enhancement of far-IR luminosity caused by galaxy collisions. A model is presented which describes the properties of the Markarian galaxies in terms of enhanced OB star formation and different grain size distributions. The results of the investigation are shown to be consistent with a 'subdued' interpretation of merging galaxies with high luminosities.

  7. Evidence for Quasar Activity Triggered by Galaxy Mergers in HST Observations of Dust-reddened Quasars

    NASA Astrophysics Data System (ADS)

    Urrutia, Tanya; Lacy, Mark; Becker, Robert H.

    2008-02-01

    We present Hubble Space Telescope ACS images of 13 dust-reddened type 1 quasars selected from the FIRST/2MASS Red Quasar Survey. These quasars have high intrinsic luminosities after correction for dust obscuration (-23.5 >= MB >= - 26.2 from K-magnitude). The images show strong evidence of recent or ongoing interaction in 11 of the 13 cases, even before the quasar nucleus is subtracted. None of the host galaxies are well fit by a simple elliptical profile. The fraction of quasars showing interaction is significantly higher than the 30% seen in samples of host galaxies of normal, unobscured quasars. There is a weak correlation between the amount of dust reddening and the magnitude of interaction in the host galaxy, measured using the Gini coefficient and the concentration index. Although few host galaxy studies of normal quasars are matched to ours in intrinsic quasar luminosity, no evidence has been found for a strong dependence of merger activity on host luminosity in samples of the host galaxies of normal quasars. We thus believe that the high merger fraction in our sample is related to their obscured nature, with a significant amount of reddening occurring in the host galaxy. The red quasar phenomenon seems to have an evolutionary explanation, with the young quasar spending the early part of its lifetime enshrouded in an interacting galaxy. This might be further indication of a link between AGNs and starburst galaxies.

  8. Dust in 3CR radio galaxies: On the FR 1 - FR 2 difference

    NASA Astrophysics Data System (ADS)

    Müller, S. A. H.; Haas, M.; Siebenmorgen, R.; Klaas, U.; Meisenheimer, K.; Chini, R.; Albrecht, M.

    2004-11-01

    We compare three 3CR samples of 11 FR 1 galaxies, 17 FR 2 galaxies and 18 lobe-dominated quasars contained in the ISO Data Archive. In contrast to the powerful FR 2 galaxies with edge-brightened lobes, the low radio power FR 1 galaxies in our sample do not exhibit any high MIR or FIR dust luminosity, which is typical for a buried, intrinsically more luminous AGN. This consolidates the fact already inferred from optical studies that their AGNs have only a relatively low luminosity. Also the FR 1 galaxies show a high FIR/MIR luminosity ratio, compared to quasars, suggesting that their FIR luminosity is substantially powered by the interstellar radiation field (ISRF) of the giant elliptical hosts. Finally, we discuss the FR 1 - FR 2 morphological dichotomy. FR 1 galaxies do not have more interstellar matter (ISM) than FR 2s as traced - on the large scale - by the cool FIR emitting dust and - in the nuclear region - by the warm MIR emitting dust. Due to the lack of central gas we suggest that the black holes of our FR 1 galaxies are fed at a lower accretion rate than those of the FR 2 galaxies. Based on observations with the Infrared Space Observatory ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the UK) and with the participation of ISAS and NASA.

  9. Direct Measurement of Dust Attenuation in z approx. 1.5 Star-Forming Galaxies from 3D-HST: Implications for Dust Geometry and Star Formation Rates

    NASA Technical Reports Server (NTRS)

    Price, Sedona H.; Kriek, Mariska; Brammer, Gabriel B; Conroy, Charlie; Schreiber, Natascha M. Foerster; Franx, Marijn; Fumagalli, Mattia; Lundren, Britt; Momcheva, Ivelina; Nelson, Erica J.; hide

    2013-01-01

    The nature of dust in distant galaxies is not well understood, and until recently few direct dust measurements have been possible. We investigate dust in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between dust towards star-forming regions (measured using Balmer decrements) and the integrated dust properties (derived by comparing spectral energy distributions [SEDs] with stellar population and dust models) for a statistically significant sample of distant galaxies. We select a sample of 163 galaxies between 1.36< or = z< or = 1.5 with H(alpha) SNR > or = 5 and measure Balmer decrements from stacked spectra. First, we stack spectra in bins of integrated stellar dust attenuation, and find that there is extra dust extinction towards star-forming regions (AV,HII is 1.81 times the integrated AV, star), though slightly lower than found for low-redshift starburst galaxies. Next, we stack spectra in bins of specific star formation rate (log sSFR), star formation rate (log SFR), and stellar mass (logM*). We find that on average AV,HII increases with SFR and mass, but decreases with increasing sSFR. The amount of extra extinction also decreases with increasing sSFR and decreasing stellar mass. Our results are consistent with the two-phase dust model - in which galaxies contain both a diffuse and a stellar birth cloud dust component - as the extra extinction will increase once older stars outside the star-forming regions become more dominant. Finally, using our Balmer decrements we derive dust-corrected H(alpha) SFRs, and find evidence that SED fitting produces incorrect SFRs if very rapidly declining SFHs are included in the explored parameter space. Subject headings: dust, extinction- galaxies: evolution- galaxies: high-redshift

  10. The relation between the gas, dust and total mass in edge-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Allaert, Flor

    2015-02-01

    Each component of a galaxy plays its own unique role in regulating the galaxy's evolution. In order to understand how galaxies form and evolve, it is therefore crucial to study the distribution and properties of each of the various components, and the links between them, both radially and vertically. The latter is only possible in edge-on systems. We present the HEROES project, which aims to investigate the 3D structure of the interstellar gas, dust, stars and dark matter in a sample of 7 massive early-type spiral galaxies based on a multi-wavelength data set including optical, NIR, FIR and radio data.

  11. Pixel-based dust-extinction mapping in nearby galaxies: A new approach to lifting the veil of dust

    NASA Astrophysics Data System (ADS)

    Tamura, Kazuyuki

    In the first part of this dissertation, I explore a new approach to mapping dust extinction in galaxies, using the observed and estimated dust-free flux- ratios of optical V -band and mid-IR 3.6 micro-meter emission. Inferred missing V -band flux is then converted into an estimate of dust extinction. While dust features are not clearly evident in the observed ground-based images of NGC 0959, the target of my pilot study, the dust-map created with this method clearly traces the distribution of dust seen in higher resolution Hubble images. Stellar populations are then analyzed through various pixel Color- Magnitude Diagrams and pixel Color-Color Diagrams (pCCDs), both before and after extinction correction. The ( B - 3.6 microns) versus (far-UV - U ) pCCD proves particularly powerful to distinguish pixels that are dominated by different types of or mixtures of stellar populations. Mapping these pixel- groups onto a pixel-coordinate map shows that they are not distributed randomly, but follow genuine galactic structures, such as a previously unrecognized bar. I show that selecting pixel-groups is not meaningful when using uncorrected colors, and that pixel-based extinction correction is crucial to reveal the true spatial variations in stellar populations. This method is then applied to a sample of late-type galaxies to study the distribution of dust and stellar population as a function of their morphological type and absolute magnitude. In each galaxy, I find that dust extinction is not simply decreasing radially, but that is concentrated in localized clumps throughout a galaxy. I also find some cases where star-formation regions are not associated with dust. In the second part, I describe the application of astronomical image analysis tools for medical purposes. In particular, Source Extractor is used to detect nerve fibers in the basement membrane images of human skin-biopsies of obese subjects. While more development and testing is necessary for this kind of work

  12. Submillimeter Observations of CLASH 2882 and the Evolution of Dust in this Galaxy

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Staguhn, Johannes; Arendt, Richard G; Kovacs, Attila; Decarli, Roberto; Egami, Eiichi; Michalowski, Michal J.; Rawle, Timothy D.; Toft, Sune; Walter, Fabian

    2015-01-01

    Two millimeter observations of the MACS J1149.6+2223 cluster have detected a source that was consistent with the location of the lensed MACS 1149-JD galaxy at z = 9.6. A positive identification would have rendered this galaxy as the youngest dust forming galaxy in the universe. Follow up observation with the AzTEC 1.1 mm camera and the IRAM NOrthern Extended Millimeter Array (NOEMA) at 1.3 mm have not confirmed this association. In this paper we show that the NOEMA observations associate the 2 mm source with [PCB2012] 2882,12 source number 2882 in the Cluster Lensing And Supernova survey with Hubble (CLASH) catalog of MACS J1149.6 +2223. This source, hereafter referred to as CLASH 2882, is a gravitationally lensed spiral galaxy at z = 0.99. We combine the Goddard IRAM Superconducting 2-Millimeter Observer (GISMO) 2 mm and NOEMA 1.3 mm fluxes with other (rest frame) UV to far-IR observations to construct the full spectral energy distribution of this galaxy, and derive its star formation history, and stellar and interstellar dust content. The current star formation rate of the galaxy is 54/mu/Solar Mass/yr, and its dust mass is about 5 × 10(exp 7)/mu Solar Mass, where mu is the lensing magnification factor for this source, which has a mean value of 2.7. The inferred dust mass is higher than the maximum dust mass that can be produced by core collapse supernovae and evolved AGB stars. As with many other star forming galaxies, most of the dust mass in CLASH 2882 must have been accreted in the dense phases of the interstellar medium.

  13. Submillimeter Observations of CLASH 2882 and the Evolution of Dust in this Galaxy

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Staguhn, Johannes; Arendt, Richard G; Kovacs, Attila; Decarli, Roberto; Egami, Eiichi; Michalowski, Michal J.; Rawle, Timothy D.; Toft, Sune; Walter, Fabian

    2015-01-01

    Two millimeter observations of the MACS J1149.6+2223 cluster have detected a source that was consistent with the location of the lensed MACS 1149-JD galaxy at z = 9.6. A positive identification would have rendered this galaxy as the youngest dust forming galaxy in the universe. Follow up observation with the AzTEC 1.1 mm camera and the IRAM NOrthern Extended Millimeter Array (NOEMA) at 1.3 mm have not confirmed this association. In this paper we show that the NOEMA observations associate the 2 mm source with [PCB2012] 2882,12 source number 2882 in the Cluster Lensing And Supernova survey with Hubble (CLASH) catalog of MACS J1149.6 +2223. This source, hereafter referred to as CLASH 2882, is a gravitationally lensed spiral galaxy at z = 0.99. We combine the Goddard IRAM Superconducting 2-Millimeter Observer (GISMO) 2 mm and NOEMA 1.3 mm fluxes with other (rest frame) UV to far-IR observations to construct the full spectral energy distribution of this galaxy, and derive its star formation history, and stellar and interstellar dust content. The current star formation rate of the galaxy is 54/mu/Solar Mass/yr, and its dust mass is about 5 × 10(exp 7)/mu Solar Mass, where mu is the lensing magnification factor for this source, which has a mean value of 2.7. The inferred dust mass is higher than the maximum dust mass that can be produced by core collapse supernovae and evolved AGB stars. As with many other star forming galaxies, most of the dust mass in CLASH 2882 must have been accreted in the dense phases of the interstellar medium.

  14. Submillimeter Observations of CLASH 2882 and the Evolution of Dust in this Galaxy

    NASA Astrophysics Data System (ADS)

    Dwek, Eli; Staguhn, Johannes; Arendt, Richard G.; Kovács, Attila; Decarli, Roberto; Egami, Eiichi; Michałowski, Michał J.; Rawle, Timothy D.; Toft, Sune; Walter, Fabian

    2015-11-01

    Two millimeter observations of the MACS J1149.6+2223 cluster have detected a source that was consistent with the location of the lensed MACS 1149-JD galaxy at z = 9.6. A positive identification would have rendered this galaxy as the youngest dust forming galaxy in the universe. Follow up observation with the AzTEC 1.1 mm camera and the IRAM NOrthern Extended Millimeter Array (NOEMA) at 1.3 mm have not confirmed this association. In this paper we show that the NOEMA observations associate the 2 mm source with [PCB2012] 2882,12 source number 2882 in the Cluster Lensing And Supernova survey with Hubble (CLASH) catalog of MACS J1149.6+2223. This source, hereafter referred to as CLASH 2882, is a gravitationally lensed spiral galaxy at z = 0.99. We combine the Goddard IRAM Superconducting 2-Millimeter Observer (GISMO) 2 mm and NOEMA 1.3 mm fluxes with other (rest frame) UV to far-IR observations to construct the full spectral energy distribution of this galaxy, and derive its star formation history, and stellar and interstellar dust content. The current star formation rate of the galaxy is 54{μ }-1 M⊙ yr-1, and its dust mass is about 5 × 107{μ }-1 M⊙, where μ is the lensing magnification factor for this source, which has a mean value of 2.7. The inferred dust mass is higher than the maximum dust mass that can be produced by core collapse supernovae and evolved AGB stars. As with many other star forming galaxies, most of the dust mass in CLASH 2882 must have been accreted in the dense phases of the interstellar medium.

  15. Dust extinction of the stellar continua in starburst galaxies: The ultraviolet and optical extinction law

    NASA Technical Reports Server (NTRS)

    Calzetti, Daniela; Kinney, Anne L.; Storchi-Bergmann, Thaisa

    1994-01-01

    We analyze the International Ultraviolet Explorer (IUE) UV and the optical spectra of 39 starburst and blue compact galaxies in order to study the average properties of dust extinction in extended regions of galaxies. The optical spectra have been obtained using an aperture which matches that of IUE, so comparable regions within each galaxy are sampled. The data from the 39 galaxies are compared with five models for the geometrical distribution of dust, adopting as extinction laws both the Milky Way and the Large Magellanic Cloud laws. The commonly used uniform dust screen is included among the models. We find that none of the five models is in satisfactory agreement with the data. In order to understand the discrepancy between the data and the models, we have derived an extinction law directly from the data in the UV and optical wavelength range. The resulting curve is characterized by an overall slope which is more gray than the Milky Way extinction law's slope, and by the absence of the 2175 A dust feature. Remarkably, the difference in optical depth between the Balmer emission lines H(sub alpha) and H(sub beta) is about a factor of 2 larger than the difference in the optical depth between the continuum underlying the two Balmer lines. We interpret this discrepancy as a consequence of the fact that the hot ionizing stars are associated with dustier regions than the cold stellar population is. The absence of the 2175 A dust feature can be due either to the effects of the scattering and clumpiness of the dust or to a chemical composition different from that of the Milky Way dust grains. Disentangling the two interpretations is not easy because of the complexity of the spatial distribution of the emitting regions. The extinction law of the UV and optical spectral continua of extended regions can be applied to the spectra of medium- and high-redshift galaxies, where extended regions of a galaxy are, by necessity, sampled.

  16. Some effects of dust on photometry of high-z galaxies: Confounding the effects of evolution

    NASA Technical Reports Server (NTRS)

    Thronson, H. A., Jr.; Witt, A. N.; Capuano, J.

    1993-01-01

    Photometric observations of very distant galaxies--e.g., color vs. z or magnitude vs. z, have been used over the past decade or so in investigations into the evolution of the stellar component. Numerous studies have predicted significant color variations as a result of evolution, in addition to the shifting of different rest wavelengths into the band of observation. Although there is significant scatter, the data can be fit with relatively straightforward, plausible models for galaxian evolution. In very few cases are the effects of dust extinction included in the models. This is due in a large part to the uncertainty about the distribution and optical properties of the grains, and even whether or not they are present in significant numbers in some types of galaxies such as ellipticals. It is likely that the effects of dust on broadband observations are the greatest uncertainty in studies of very distant galaxies. We use a detailed Monte Carlo radiative transfer model within a spherical geometry for different star/dust distributions to examine the effects of dust on the broadband colors of galaxies as a function of redshift. The model fully accounts for absorption and angular redistribution in scattering. In this summary, we consider only the effects on color vs. redshift for three simple geometries each with the same total dust optical depth. Elsewhere at this conference, Capuano, Thronson, & Witt consider other effects of altering the relative dust/star distribution.

  17. The Herschel Virgo Cluster Survey. IV. Resolved dust analysis of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Smith, M. W. L.; Vlahakis, C.; Baes, M.; Bendo, G. J.; Bianchi, S.; Bomans, D. J.; Boselli, A.; Clemens, M.; Corbelli, E.; Cortese, L.; Dariush, A.; Davies, J. I.; De Looze, I.; di Serego Alighieri, S.; Fadda, D.; Fritz, J.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Grossi, M.; Hughes, T. M.; Hunt, L. K.; Jones, A. P.; Madden, S.; Pierini, D.; Pohlen, M.; Sabatini, S.; Verstappen, J.; Xilouris, E. M.; Zibetti, S.

    2010-07-01

    We present a resolved dust analysis of three of the largest angular size spiral galaxies, NGC 4501 and NGC 4567/8, in the Herschel Virgo Cluster Survey (HeViCS) science demonstration field. Herschel has unprecedented spatial resolution at far-infrared wavelengths and with the PACS and SPIRE instruments samples both sides of the peak in the far infrared spectral energy distribution (SED). We present maps of dust temperature, dust mass, and gas-to-dust ratio, produced by fitting modified black bodies to the SED for each pixel. We find that the distribution of dust temperature in both systems is in the range ~19-22 K and peaks away from the centres of the galaxies. The distribution of dust mass in both systems is symmetrical and exhibits a single peak coincident with the galaxy centres. This Letter provides a first insight into the future analysis possible with a large sample of resolved galaxies to be observed by Herschel. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  18. Circumstellar dust, PAHs and stellar populations in early-type galaxies: insights from GALEX and WISE

    NASA Astrophysics Data System (ADS)

    Simonian, Gregory V.; Martini, Paul

    2017-02-01

    A majority of early-type galaxies contain interstellar dust, yet the origin of this dust, and why the dust sometimes exhibits unusual polycyclic aromatic hydrocarbon (PAH) ratios, remains a mystery. If the dust is internally produced, it likely originates from the large number of asymptotic giant branch stars associated with the old stellar population. We present GALEX and WISE elliptical aperture photometry of ˜310 early-type galaxies with Spitzer mid-infrared spectroscopy and/or ancillary data from ATLAS3D, to characterize their circumstellar dust and the shape of the radiation field that illuminates the interstellar PAHs. We find that circumstellar dust is ubiquitous in early-type galaxies, which indicates some tension between stellar population age estimates and models for circumstellar dust production in very old stellar populations. We also use dynamical masses from ATLAS3D to show that WISE W1 (3.4 μm) mass-to-light ratios are consistent with the initial mass function variation found by previous work. While the stellar population differences in early-type galaxies correspond to a range of radiation field shapes incident upon the diffuse dust, the ratio of the ionization-sensitive 7.7 μm/11.3 μm PAH feature does not correlate with the shape of the radiation field, nor to variations with the size-sensitive 11.3 μm/17 μm ratio. The 7.7 μm/11.3 μm PAH ratio does tend to be smaller in galaxies with proportionally greater H2 emission, which is evidence that processing of primarily smaller grains by shocks is responsible for the unusual ratios, rather than substantial differences in the overall PAH size or ionization distribution.

  19. The impact of dust in host galaxies on quasar luminosity functions

    NASA Astrophysics Data System (ADS)

    Shirakata, Hikari; Okamoto, Takashi; Enoki, Motohiro; Nagashima, Masahiro; Kobayashi, Masakazu A. R.; Ishiyama, Tomoaki; Makiya, Ryu

    2015-06-01

    We have investigated effects of dust attenuation on quasar luminosity functions at z ˜ 2 using a semi-analytic galaxy formation model combined with a large cosmological N-body simulation. We estimate the dust attenuation of quasars self-consistently with that of galaxies by considering the dust in their host bulges. We find that the luminosity of the bright quasars is strongly dimmed by the dust attenuation, ˜2 mag in the B-band. Assuming the empirical bolometric corrections for active galactic nuclei (AGNs) by Marconi et al., we find that this dust attenuation is too strong to explain the B-band and X-ray quasar luminosity functions simultaneously. We consider two possible mechanisms that weaken the dust attenuation. As such a mechanism, we introduce a time delay for AGN activity, that is, gas fuelling to a central black hole starts sometime after the beginning of the starburst induced by a major merger. The other is the anisotropy in the dust distribution. We find that in order to make the dust attenuation of the quasars negligible, either the gas accretion into the black holes has to be delayed at least three times the dynamical time-scale of their host bulges or the dust covering factor is as small as ˜0.1.

  20. Infrared Spectral Energy Distribution Decomposition of WISE-selected, Hyperluminous Hot Dust-obscured Galaxies

    NASA Astrophysics Data System (ADS)

    Fan, Lulu; Han, Yunkun; Nikutta, Robert; Drouart, Guillaume; Knudsen, Kirsten K.

    2016-06-01

    We utilize a Bayesian approach to fit the observed mid-IR-to-submillimeter/millimeter spectral energy distributions (SEDs) of 22 WISE-selected and submillimeter-detected, hyperluminous hot dust-obscured galaxies (Hot DOGs), with spectroscopic redshift ranging from 1.7 to 4.6. We compare the Bayesian evidence of a torus plusgraybody (Torus+GB) model with that of a torus-only (Torus) model and find that the Torus+GB model has higher Bayesian evidence for all 22 Hot DOGs than the torus-only model, which presents strong evidence in favor of the Torus+GB model. By adopting the Torus+GB model, we decompose the observed IR SEDs of Hot DOGs into torus and cold dust components. The main results are as follows. (1) Hot DOGs in our submillimeter-detected sample are hyperluminous ({L}{IR}≥slant {10}13{L}⊙ ), with torus emission dominating the IR energy output. However, cold dust emission is non-negligible, contributing on average ˜ 24% of total IR luminosity. (2) Compared to QSO and starburst SED templates, the median SED of Hot DOGs shows the highest luminosity ratio between mid-IR and submillimeter at rest frame, while it is very similar to that of QSOs at ˜ 10{--}50 μ {{m}}, suggesting that the heating sources of Hot DOGs should be buried AGNs. (3) Hot DOGs have high dust temperatures ({T}{dust}˜ 72 K) and high IR luminosity of cold dust. The {T}{dust}{--}{L}{IR} relation of Hot DOGs suggests that the increase in IR luminosity for Hot DOGs is mostly due to the increase of the dust temperature, rather than dust mass. Hot DOGs have lower dust masses than submillimeter galaxies (SMGs) and QSOs within a similar redshift range. Both high IR luminosity of cold dust and relatively low dust mass in Hot DOGs can be expected by their relatively high dust temperatures. (4) Hot DOGs have high dust-covering factors (CFs), which deviate from the previously proposed trend of the dust CF decreasing with increasing bolometric luminosity. Finally, we can reproduce the observed

  1. DUST-CORRECTED COLORS REVEAL BIMODALITY IN THE HOST-GALAXY COLORS OF ACTIVE GALACTIC NUCLEI AT z {approx} 1

    SciTech Connect

    Cardamone, Carolin N.; Megan Urry, C.; Brammer, Gabriel; Schawinski, Kevin; Treister, Ezequiel; Gawiser, Eric

    2010-09-20

    Using new, highly accurate photometric redshifts from the MUSYC medium-band survey in the Extended Chandra Deep Field-South (ECDF-S), we fit synthetic stellar population models to compare active galactic nucleus (AGN) host galaxies to inactive galaxies at 0.8 {<=} z {<=} 1.2. We find that AGN host galaxies are predominantly massive galaxies on the red sequence and in the green valley of the color-mass diagram. Because both passive and dusty galaxies can appear red in optical colors, we use rest-frame near-infrared colors to separate passively evolving stellar populations from galaxies that are reddened by dust. As with the overall galaxy population, {approx}25% of the 'red' AGN host galaxies and {approx}75% of the 'green' AGN host galaxies have colors consistent with young stellar populations reddened by dust. The dust-corrected rest-frame optical colors are the blue colors of star-forming galaxies, which imply that these AGN hosts are not passively aging to the red sequence. At z {approx} 1, AGN activity is roughly evenly split between two modes of black hole growth: the first in passively evolving host galaxies, which may be heating up the galaxy's gas and preventing future episodes of star formation, and the second in dust-reddened young galaxies, which may be ionizing the galaxy's interstellar medium and shutting down star formation.

  2. Can planet formation resolve the dust budget crisis in high-redshift galaxies?

    NASA Astrophysics Data System (ADS)

    Forgan, D. H.; Rowlands, K.; Gomez, H. L.; Gomez, E. L.; Schofield, S. P.; Dunne, L.; Maddox, S.

    2017-12-01

    The process of planet formation offers a rich source of dust production via grain growth in protostellar discs, and via grinding of larger bodies in debris disc systems. Chemical evolution models, designed to follow the build up of metals and dust in galaxies, do not currently account for planet formation. We consider the possibility that the apparent underprediction of dust mass in high-redshift galaxies by chemical evolution models could be in part, due to these models neglecting this process, specifically due to their assumption that a large fraction of the dust mass is removed from the interstellar medium during star formation (so-called astration). By adding a planet formation phase into galaxy chemical evolution, we demonstrate that the dust budget crisis can be partially ameliorated by a factor of 1.3-1.5 only if (i) circumstellar discs prevent a large fraction of the dust mass entering the star during its birth, and (ii) that dust mass is preferentially liberated via jets, winds and outflows rather than accreted into planetary-mass bodies.

  3. A Significant Population of Very Luminous Dust-Obscured Galaxies at Redshift z ~ 2

    NASA Astrophysics Data System (ADS)

    Dey, Arjun; Soifer, B. T.; Desai, Vandana; Brand, Kate; Le Floc'h, Emeric; Brown, Michael J. I.; Jannuzi, Buell T.; Armus, Lee; Bussmann, Shane; Brodwin, Mark; Bian, Chao; Eisenhardt, Peter; Higdon, Sarah J.; Weedman, Daniel; Willner, S. P.

    2008-04-01

    The Spitzer Space Telescope has revealed a significant population of high-redshift (z ~ 2) dust-obscured galaxies with large mid-infrared to ultraviolet luminosity ratios. Due to their optical faintness, these galaxies have been previously missed in traditional optical studies of the distant universe. We present a simple method for selecting this high-redshift population based solely on the ratio of the observed mid-infrared 24 μm to optical R-band flux density. We apply this method to observations of the ≈8.6 deg2 NOAO Deep Wide-Field Survey Boötes field, and uncover ≈2600 dust-obscured galaxy candidates [i.e., 0.089 arcmin-2) with 24 μm flux densities F24 μ m >= 0.3 mJy and (R - [ 24]) >= 14 (i.e., Fν(24 μ m)/Fν(R) gtrsim 1000]. These galaxies have no counterparts in the local universe. They represent 7% +/- 0.6% of the 24 μm source population at F24 μ m >= 1 mJy but increase to ≈13% +/- 1% of the population at ≈0.3 mJy. These galaxies exhibit evidence of both star formation and AGN activity, with the brighter 24 μm sources being more AGN-dominated. We have measured spectroscopic redshifts for 86 of these galaxies, and find a broad redshift distribution centered at \\overline{z}≈ 1.99+/- 0.05. The space density of this population is ΣDOG(F24μ m >= 0.3 mJy) = (2.82 +/- 0.05) × 10-5h370 Mpc -3, similar to that of bright submillimeter-selected galaxies at comparable redshifts. These redshifts imply large luminosities, with median ν Lν(8 μ m) ≈ 4 × 1011 L⊙. The infrared luminosity density contributed by this relatively rare dust-obscured galaxy population is log (IRLD) ≈ 8.23+ 0.18-0.30. This is ≈60+ 40-15% of that contributed by z ~ 2 ultraluminous infrared galaxies (ULIRGs, with LIR > 1012 L⊙) our simple selection thus identifies a significant fraction of z ~ 2 ULIRGs. This IRLD is ≈26% +/- 14% of the total contributed by all z ~ 2 galaxies. We suggest that these dust-obscured galaxies are the progenitors of luminous (~4L

  4. Radial Distribution of Stars, Gas, and Dust in SINGS Galaxies. I. Surface Photometry and Morphology

    NASA Astrophysics Data System (ADS)

    Muñoz-Mateos, J. C.; Gil de Paz, A.; Zamorano, J.; Boissier, S.; Dale, D. A.; Pérez-González, P. G.; Gallego, J.; Madore, B. F.; Bendo, G.; Boselli, A.; Buat, V.; Calzetti, D.; Moustakas, J.; Kennicutt, R. C., Jr.

    2009-10-01

    We present ultraviolet through far-infrared (FIR) surface brightness profiles for the 75 galaxies in the Spitzer Infrared Nearby Galaxies Survey (SINGS). The imagery used to measure the profiles includes Galaxy Evolution Explorer UV data, optical images from Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and Sloan Digital Sky Survey, near-IR data from Two Micron All Sky Survey, and mid- and FIR images from Spitzer. Along with the radial profiles, we also provide multi-wavelength asymptotic magnitudes and several nonparametric indicators of galaxy morphology: the concentration index (C 42), the asymmetry (A), the Gini coefficient (G), and the normalized second-order moment of the brightest 20% of the galaxy's flux (\\overline{M}_{20}). In this paper, the first of a series, we describe the technical aspects regarding the surface photometry, and present a basic analysis of the global and structural properties of the SINGS galaxies at different wavelengths. The homogeneity in the acquisition, reduction, and analysis of the results presented here makes these data ideal for multiple unanticipated studies on the radial distribution of the properties of stars, dust, and gas in galaxies. Our radial profiles show a wide range of morphologies and multiple components (bulges, exponential disks, inner and outer disk truncations, etc.) that vary not only from galaxy to galaxy but also with wavelength for a given object. In the optical and near-IR, the SINGS galaxies occupy the same regions in the C 42-A-G-\\overline{M}_{20} parameter space as other normal galaxies in previous studies. However, they appear much less centrally concentrated, more asymmetric, and with larger values of G when viewed in the UV (due to star-forming clumps scattered across the disk) and in the mid-IR (due to the emission of polycyclic aromatic hydrocarbons at 8.0 μm and very hot dust at 24 μm). In an accompanying paper by Muñoz-Mateos et al., we focus on the radial

  5. Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

    NASA Astrophysics Data System (ADS)

    Aller, Monique Christine; Kulkarni, Varsha P.; York, Donald; Welty, Daniel; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli

    2015-08-01

    Gas and dust grains are fundamental components of the interstellar medium and significantly impact many of the physical processes driving galaxy evolution, such as star-formation, and the heating, cooling, and ionization of the interstellar material. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous quasars, provide a valuable tool to directly study the properties of the interstellar gas and dust in distant, normal galaxies. We have established the presence of silicate dust grains in at least some gas-rich QASs, and find that they exist at higher optical depths than expected for diffuse gas in the Milky Way. Differences in the absorption feature shapes additionally suggest variations in the silicate dust grain properties, such as in the level of grain crystallinity, from system-to-system. Recent studies of QASs also find trends in both the gas and dust properties, such as correlations in metallicity with redshift and dust depletions. We present results from a study of the gas and dust properties of QASs with adequate archival IR data to probe the silicate dust grain properties. We discuss our measurements of gas-phase element abundances based on archival high-resolution optical spectra. We also discuss our measurements of the strengths of the 10 and 18 micron silicate dust absorption features in the QASs, and constraints on the grain properties (e.g., composition, shape, crystallinity) based on fitted silicate profile templates. We investigate correlations between absorption redshift, gas metallicity, metal depletions, and silicate dust abundance, which will yield valuable insights into the star formation history. Support is provided by NASA through grant NNX14AG74G and by an award issued by JPL/Caltech, and from US-NSF grants AST-0908890 and AST-1108830 to the U. of S. Carolina.

  6. Herschel-ATLAS: the surprising diversity of dust-selected galaxies in the local submillimetre Universe

    NASA Astrophysics Data System (ADS)

    Clark, C. J. R.; Dunne, L.; Gomez, H. L.; Maddox, S.; De Vis, P.; Smith, M. W. L.; Eales, S. A.; Baes, M.; Bendo, G. J.; Bourne, N.; Driver, S. P.; Dye, S.; Furlanetto, C.; Grootes, M. W.; Ivison, R. J.; Schofield, S. P.; Robotham, A. S. G.; Rowlands, K.; Valiante, E.; Vlahakis, C.; van der Werf, P.; Wright, A. H.; de Zotti, G.

    2015-09-01

    We present the properties of the first 250 μm blind sample of nearby galaxies (15 < D < 46 Mpc) containing 42 objects from the Herschel Astrophysical Terahertz Large Area Survey. Herschel's sensitivity probes the faint end of the dust luminosity function for the first time, spanning a range of stellar mass (7.4 < M⋆ < 11.3 log10 M⊙), star formation activity (-11.8 < SSFR < -8.9 log10 yr-1), gas fraction (3-96 per cent), and colour (0.6 < FUV-KS < 7.0 mag). The median cold dust temperature is 14.6 K, colder than in the Herschel Reference Survey (18.5 K) and Planck Early Release Compact Source Catalogue (17.7 K). The mean dust-to-stellar mass ratio in our sample is higher than these surveys by factors of 3.7 and 1.8, with a dust mass volume density of (3.7 ± 0.7) × 105 M⊙ Mpc-3. Counter-intuitively, we find that the more dust rich a galaxy, the lower its UV attenuation. Over half of our dust-selected sample are very blue in FUV-KS colour, with irregular and/or highly flocculent morphology; these galaxies account for only 6 per cent of the sample's stellar mass but contain over 35 per cent of the dust mass. They are the most actively star-forming galaxies in the sample, with the highest gas fractions and lowest UV attenuation. They also appear to be in an early stage of converting their gas into stars, providing valuable insights into the chemical evolution of young galaxies.

  7. A Search for Stellar Dust Production in Leo P, a Nearby Analog of High Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Boyer, Martha; McDonald, Iain; McQuinn, Kristen; Skillman, Evan; Sonneborn, George; Srinivasan, Sundar; van Loon, Jacco Th.; Zijlstra, Albert; Sloan, Greg

    2016-08-01

    The origin of dust in the early Universe is a matter of debate. One of the main potential dust contributors are Asymptotic Giant Branch (AGB) stars, and several studies have been devoted to investigating whether and how AGB dust production changes in metal-poor environments. Of particular interest are the most massive AGB stars (8-10 Msun), which can in principle enter the dust-producing phase <50 Myr after they form. However, these stars cannot produce their own condensable material (unlike carbon AGB stars), so the efficiency of dust production decreases with metallicity. Evidence for dust production in massive AGB stars more metal-poor than the Magellanic Clouds is scarce due both to the rarity of chemically-unevolved, star-forming systems reachable in the infrared and to the short lifetimes of these stars. The recently discovered galaxy Leo P provides an irresistible opportunity to search for these massive AGB stars: Leo P is a gas-rich, star-forming galaxy, it is nearby enough for resolved star photometry with Spitzer, and its interstellar medium is 0.4 dex more metal-poor than any other accessible star-forming galaxy. Models predict ~3 massive AGB stars may be present in Leo P, and optical HST observations reveal 7 candidates. We propose to use Spitzer to determine whether these stars are dusty, providing valuable constraints to the dust contribution from AGB stars up to at least redshift 3.2, or 11.7 Gyr ago, when massive spheroidals and Galactic globular clusters were still forming. This is a gain of 2.8 Gyr compared to other accessible galaxies. We also request 1 orbit of joint HST time to confirm whether the AGB candidates in Leo P are indeed massive AGB stars belonging to the galaxy. These observations will provide information crucial for potential JWST followup spectroscopy.

  8. Dust-to-gas ratio and metallicity variations in nearby galaxies

    NASA Astrophysics Data System (ADS)

    Issa, M. R.; MacLaren, I.; Wolfendale, A. W.

    1990-09-01

    The dependence of the dust-to-gas ratio on Galacto-centric radius and its relation to the known metallicity gradient in the Galaxy and nearby galaxies is investigated. Despite the large degree of uncertainty associated with both quantities, there is evidence for a correlation, with dust-to-gas ratio and metallicity decreasing at roughly the same rate with increasing radius. Such a result has important implications. For example, attempts using FIR surveys to estimate the conversion between observed CO emission and molecular hydrogen column density should allow for the varying dust-to-gas ratio. Broadbent et al. (1989) used a dust-to-gas ratio that varied in proportion to metallicity, following the approach used by Cox et al. (1986), and confirmed the previously estimated low value for the conversion factor; there is thus support for this result.

  9. Evolution of dust content in galaxies probed by gamma-ray burst afterglows

    NASA Astrophysics Data System (ADS)

    Kuo, Tzu-Ming; Hirashita, Hiroyuki; Zafar, Tayyaba

    2013-12-01

    Because of their brightness, gamma-ray burst (GRB) afterglows are viable targets for investigating the dust content in their host galaxies. Simple intrinsic spectral shapes of GRB afterglows allow us to derive the dust extinction. Recently, the extinction data of GRB afterglows are compiled up to redshift z = 6.3, in combination with hydrogen column densities and metallicities. This data set enables us to investigate the relation between dust-to-gas ratio and metallicity out to high redshift for a wide metallicity range. By applying our evolution models of dust content in galaxies, we find that the dust-to-gas ratios derived from GRB afterglow extinction data are excessively high such that they can be explained with a fraction of gas-phase metals condensed into dust (fin) ˜ 1, while theoretical calculations on dust formation in the wind of asymptotic giant branch stars and in the ejecta of Type II supernovae suggest a much more moderate condensation efficiency (fin ˜ 0.1). Efficient dust growth in dense clouds has difficulty in explaining the excessive dust-to-gas ratio at metallicities Z/Z⊙ < ɛ, where ɛ is the star formation efficiency of the dense clouds. However, if ɛ is as small as 0.01, the dust-to-gas ratio at Z ˜ 10-2 Z⊙ can be explained with nH ≳ 106 cm-3. Therefore, a dense environment hosting dust growth is required to explain the large fraction of metals condensed into dust, but such clouds should have low star formation efficiencies to avoid rapid metal enrichment by stars.

  10. Radial distribution of dust, stars, gas, and star-formation rate in DustPedia⋆ face-on galaxies

    NASA Astrophysics Data System (ADS)

    Casasola, V.; Cassarà, L. P.; Bianchi, S.; Verstocken, S.; Xilouris, E.; Magrini, L.; Smith, M. W. L.; De Looze, I.; Galametz, M.; Madden, S. C.; Baes, M.; Clark, C.; Davies, J.; De Vis, P.; Evans, R.; Fritz, J.; Galliano, F.; Jones, A. P.; Mosenkov, A. V.; Viaene, S.; Ysard, N.

    2017-09-01

    Aims: The purpose of this work is the characterization of the radial distribution of dust, stars, gas, and star-formation rate (SFR) in a sub-sample of 18 face-on spiral galaxies extracted from the DustPedia sample. Methods: This study is performed by exploiting the multi-wavelength DustPedia database, from ultraviolet (UV) to sub-millimeter bands, in addition to molecular (12CO) and atomic (Hi) gas maps and metallicity abundance information available in the literature. We fitted the surface-brightness profiles of the tracers of dust and stars, the mass surface-density profiles of dust, stars, molecular gas, and total gas, and the SFR surface-density profiles with an exponential curve and derived their scale-lengths. We also developed a method to solve for the CO-to-H2 conversion factor (αCO) per galaxy by using dust- and gas-mass profiles. Results: Although each galaxy has its own peculiar behavior, we identified a common trend of the exponential scale-lengths versus wavelength. On average, the scale-lengths normalized to the B-band 25 mag/arcsec2 radius decrease from UV to 70 μm, from 0.4 to 0.2, and then increase back up to 0.3 at 500 microns. The main result is that, on average, the dust-mass surface-density scale-length is about 1.8 times the stellar one derived from IRAC data and the 3.6 μm surface brightness, and close to that in the UV. We found a mild dependence of the scale-lengths on the Hubble stage T: the scale-lengths of the Herschel bands and the 3.6 μm scale-length tend to increase from earlier to later types, the scale-length at 70 μm tends to be smaller than that at longer sub-mm wavelength with ratios between longer sub-mm wavelengths and 70 μm that decrease with increasing T. The scale-length ratio of SFR and stars shows a weak increasing trend towards later types. Our αCO determinations are in the range (0.3-9) M⊙ pc-2 (K km s-1)-1, almost invariant by using a fixed dust-to-gas ratio mass (DGR) or a DGR depending on metallicity

  11. The large scale dust distribution in the inner galaxy

    NASA Technical Reports Server (NTRS)

    Hauser, M. G.; Dwek, E.; Gezari, D.; Silverberg, R.; Kelsall, T.; Stier, M.; Cheung, L.

    1983-01-01

    Initial results are presented from a new large-scale survey of the first quadrant of the galactic plane at wavelengths of 160, 260, and 300 microns. The submillimeter wavelength emission, interpreted as thermal radiation by dust grains, reveals an optically thin disk of angular width about 0.09 deg (FWHM) with a mean dust temperature of 23 K and significant variation of the dust mass column density. Comparison of the dust column density with the gas column density inferred from CO survey data shows a striking spatial correlation. The mean luminosity per hydrogen atom is found to be 2.5 x 10 to the -30th W/H, implying a radiant energy density in the vicinity of the dust an order of magnitude larger than in the solar neighborhood. The data favor dust in molecular clouds as the dominant submillimeter radiation source.

  12. Connecting the Silicate Dust and Gas Properties of Distant Galaxies Using Quasar Absorption Systems

    NASA Astrophysics Data System (ADS)

    Aller, Monique C.; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli; Beiranvand, Nassim; Morrison, Sean

    2016-01-01

    We present recent results from our program investigating the silicate dust properties in distant galaxies using quasar absorption systems. The dust and gas properties of distant galaxies can be characterized by studying the absorption features produced by them along the sightlines to luminous background quasars. Based on our prior finding that silicate dust absorption in z<1.5 quasar absorption systems exhibits a range of optical depths and absorption feature substructures, suggestive of silicate grain property variations, we are investigating silicate dust absorption in quasar absorption systems toward quasars with archival Spitzer Space Telescope Infrared Spectrograph (IRS) spectra. We present our measurements of the 10 and/or 18 micron silicate dust absorption feature(s) in these systems, and discuss constraints on the grain properties, such as composition and crystallinity, based on the shape and substructure present in these features. We also investigate the correlations between the silicate dust properties and the reddening. Connections between the silicate dust and gas phase metal absorption properties can also be probed for some of our targets with archival ground-based spectra. These relationships will yield valuable insights into the star formation history and evolution of metals and dust. This work is supported by NASA through ADAP grant NNX14AG74G and by an award issued by JPL/Caltech, and from US-NSF grant AST-1108830 to the University of South Carolina.

  13. Major-Merger Galaxy Pairs at Z = 0: Dust Properties and Companion Morphology

    NASA Astrophysics Data System (ADS)

    Domingue, Donovan L.; Cao, Chen; Xu, C. Kevin; Jarrett, Thomas H.; Ronca, Joseph; Hill, Emily; Jacques, Allison

    2016-10-01

    We present an analysis of dust properties of a sample of close major-merger galaxy pairs selected by K s magnitude and redshift. The pairs represent the two populations of spiral-spiral (S+S) and mixed morphology spiral-elliptical (S+E). The Code Investigating GALaxy Emission software is used to fit dust models to the Two Micron All Sky Survey, Wide-Field Infrared Survey Explorer, and Herschel flux density measurements, and to derive the parameters describing the polycyclic aromatic hydrocarbons contribution, interstellar radiation field, and photodissociation regions. Model fits verify our previous Spitzer Space Telescope analysis that S+S and S+E pairs do not have the same level of enhancement of star formation and differ in dust composition. The spirals of mixed-morphology galaxy pairs do not exhibit the enhancements in interstellar radiation field and therefore dust temperature for spirals in S+S pairs in contrast to what would be expected according to standard models of gas redistribution due to encounter torques. This suggests the importance of the companion environment/morphology in determining the dust properties of a spiral galaxy in a close major-merger pair.

  14. Probing The Stellar, Gaseous, And Dust Properties Of Galaxies Through Analysis Of Their Spectral Energy Distributions

    NASA Astrophysics Data System (ADS)

    Eufrasio, Rafael T.

    The spectral energy distributions (SEDs) of galaxies are shaped by their physical properties and they are our primary source of information on galaxies stellar, gaseous, and dust content. Nearby galaxies (less than 100 Mpc away) are spatially resolved by current telescopes from the ultraviolet (UV) to radio wavelengths, allowing the study of the SEDs of subgalactic regions. Such studies are necessary for deriving maps and spatial trends of the physical properties across a galaxy. In principle, the complex history of the formation, growth, and evolution of a galaxy or a region of a galaxy can be inferred from its radiative output. In practice, this task is complicated by the fact that a significant fraction of the star formation activity takes place in dust obscured regions, in which a significant fraction of the stellar radiative output is absorbed, scattered, and reradiated by the gas and dust in the interstellar medium (ISM). This reprocessing of the stellar radiation takes place in ionized interstellar gas regions (H II regions) surrounding massive hot stars, in diffuse atomic gas (H I regions), and in dense molecular clouds. For this work, we have analyzed two galaxies in detail, NGC 6872 and NGC 6946, also known as Condor and Fireworks Galaxy, respectively. The Condor galaxy is the largest-known spiral galaxy. It is part a group of galaxies, the Pavo group, with 12 other galaxies. It has, however, interacted in the past ~150 Myr with a smaller companion, previously believed to have shaped the physical extent of the giant spiral. We have performed detailed SED fitting from the UV to mid-infrared (mid-IR) to obtain star formation histories of seventeen sub-galactic regions across the Condor. These regions are large enough to be galaxies themselves, with 32.3 million light-years in diameter. We find that the Condor was already very massive before this interaction and that it was much less affected by the passage of the companion than previously thought. We also

  15. Cosmic reionization on computers. Ultraviolet continuum slopes and dust opacities in high redshift galaxies

    SciTech Connect

    Khakhaleva-Li, Zimu; Gnedin, Nickolay Y.

    2016-03-30

    In this study, we compare the properties of stellar populations of model galaxies from the Cosmic Reionization On Computers (CROC) project with the exiting UV and IR data. Since CROC simulations do not follow cosmic dust directly, we adopt two variants of the dust-follows-metals ansatz to populate model galaxies with dust. Using the dust radiative transfer code Hyperion, we compute synthetic stellar spectra, UV continuum slopes, and IR fluxes for simulated galaxies. We find that the simulation results generally match observational measurements, but, perhaps, not in full detail. The differences seem to indicate that our adopted dust-follows-metals ansatzes are not fully sufficient. While the discrepancies with the exiting data are marginal, the future JWST data will be of much higher precision, rendering highly significant any tentative difference between theory and observations. It is, therefore, likely, that in order to fully utilize the precision of JWST observations, fully dynamical modeling of dust formation, evolution, and destruction may be required.

  16. Cosmic reionization on computers. Ultraviolet continuum slopes and dust opacities in high redshift galaxies

    DOE PAGES

    Khakhaleva-Li, Zimu; Gnedin, Nickolay Y.

    2016-03-30

    In this study, we compare the properties of stellar populations of model galaxies from the Cosmic Reionization On Computers (CROC) project with the exiting UV and IR data. Since CROC simulations do not follow cosmic dust directly, we adopt two variants of the dust-follows-metals ansatz to populate model galaxies with dust. Using the dust radiative transfer code Hyperion, we compute synthetic stellar spectra, UV continuum slopes, and IR fluxes for simulated galaxies. We find that the simulation results generally match observational measurements, but, perhaps, not in full detail. The differences seem to indicate that our adopted dust-follows-metals ansatzes are notmore » fully sufficient. While the discrepancies with the exiting data are marginal, the future JWST data will be of much higher precision, rendering highly significant any tentative difference between theory and observations. It is, therefore, likely, that in order to fully utilize the precision of JWST observations, fully dynamical modeling of dust formation, evolution, and destruction may be required.« less

  17. COSMIC REIONIZATION ON COMPUTERS. ULTRAVIOLET CONTINUUM SLOPES AND DUST OPACITIES IN HIGH REDSHIFT GALAXIES

    SciTech Connect

    Khakhaleva-Li, Zimu; Gnedin, Nickolay Y. E-mail: gnedin@fnal.gov

    2016-04-01

    We compare the properties of stellar populations of model galaxies from the Cosmic Reionization On Computers (CROC) project with the exiting ultraviolet (UV) and IR data. Since CROC simulations do not follow cosmic dust directly, we adopt two variants of the dust-follows-metals ansatz to populate model galaxies with dust. Using the dust radiative transfer code Hyperion, we compute synthetic stellar spectra, UV continuum slopes, and IR fluxes for simulated galaxies. We find that the simulation results generally match observational measurements, but, perhaps, not in full detail. The differences seem to indicate that our adopted dust-follows-metals ansatzes are not fully sufficient. While the discrepancies with the exiting data are marginal, the future James Webb Space Telescope (JWST) data will be of much higher precision, rendering highly significant any tentative difference between theory and observations. It is, therefore, likely, that in order to fully utilize the precision of JWST observations, fully dynamical modeling of dust formation, evolution, and destruction may be required.

  18. Dust evolution processes constrained by extinction curves in nearby galaxies

    NASA Astrophysics Data System (ADS)

    Hou, Kuan-Chou; Hirashita, Hiroyuki; Michałowski, Michał J.

    2016-12-01

    Extinction curves, especially those in the Milky Way (MW), the Large Magellanic Cloud (LMC), and the Small Magellanic Cloud (SMC), have provided us with a clue to the dust properties in the nearby Universe. We examine whether or not these extinction curves can be explained by well-known dust evolution processes. We treat the dust production in stellar ejecta, destruction in supernova shocks, dust growth by accretion and coagulation, and dust disruption by shattering. To make a survey of the large parameter space possible, we simplify the treatment of the grain size distribution evolution by adopting the "two-size approximation," in which we divide the grain population into small (≲0.03 μm) and large (≳0.03 μm) grains. It is confirmed that the MW extinction curve can be reproduced in reasonable ranges for the time-scale of the above processes with a silicate-graphite mixture. This indicates that the MW extinction curve is a natural consequence of the dust evolution through the above processes. We also find that the same models fail to reproduce the SMC/LMC extinction curves. Nevertheless, this failure can be remedied by giving higher supernova destruction rates for small dust particles dust and considering amorphous carbon for carbonaceous dust; these modifications in fact fall in line with previous studies. Therefore, we conclude that the current dust evolution scenario composed of the aforementioned processes is successful in explaining the extinction curves. All the extinction curves favor efficient interstellar processing of dust, especially strong grain growth by accretion and coagulation.

  19. THE MID-IR CONTRIBUTION OF DUST-ENSHROUDED STARS IN SIX NEARBY GALAXIES

    SciTech Connect

    Gerke, J. R.; Kochanek, C. S.

    2013-01-01

    We measure the integrated contributions of dusty asymptotic giant branch (AGB) stars and other luminous red mid-IR sources to the mid-IR luminosities of six galaxies (M81, NGC 2403, NGC 300, M33, and the Magellanic Clouds). We find the dusty AGB stars whose mid-IR fluxes are dominated by dust rather than photospheric emission contribute from 0.6% (M81) to 5.6% (SMC) of the 3.6 {mu}m flux and 1.0% (M81) to 10.1% (SMC) of the 4.5 {mu}m flux. We find a trend of decreasing AGB contribution with increasing galaxy metallicity, luminosity, and mass, and decreasing specific star formation rate (SSFR). However, these galaxy properties are strongly correlated in our sample and the simplest explanation of the trend is galaxy metallicity. Bright, red sources other than dusty AGB stars represent a smaller fraction of the luminosity, {approx}1.2% at 3.6 {mu}m, however, their dust is likely cooler and their contributions are likely larger at longer wavelengths. Excluding the SMC, the contribution from these red sources correlates with the SSFR as we would expect for massive stars. In total, after correcting for dust emission at other wavelengths, the dust around AGB stars radiates 0.1%-0.8% of the bolometric luminosities of the galaxies. Thus, hot dust emission from AGB and other luminous dusty stars represent a small fraction of the total luminosities of the galaxies but a significant fraction of their mid-IR emissions.

  20. IR Fine-Structure Line Signatures of Central Dust-Bounded Nebulae in Luminous Infrared Galaxies

    NASA Technical Reports Server (NTRS)

    Fischer, J.; Allen, R.; Dudley, C. C.; Satyapal, S.; Luhman, M.; Wolfire, M.; Smith, H. A.

    2004-01-01

    To date, the only far-infrared spectroscopic observations of ultraluminous infrared galaxies have been obtained with the European Space Agency s Infrared Space Observatory Long Wavelength Spectrometer. The spectra of these galaxies are characterized by molecular absorption lines and weak emission lines from photodissociation regions (PDRs), but no far-infrared (greater than 40 microns) lines from ionized regions have been detected. ESA s Herschel Space Observatory, slated for launch in 2007, will likely be able to detect these lines in samples of local and moderate redshift ultra luminous galaxies and to enable measurement of the ionization parameters, the slope of the ionizing continuum, and densities present in the ionized regions of these galaxies. The higher spatial resolution of proposed observatories discussed in this workshop will enable isolation of the central regions of local galaxies and detection of these lines in high-redshift galaxies for study of the evolution of galaxies. Here we discuss evidence for the e.ects of absorption by dust within ionized regions and present the spectroscopic signatures predicted by photoionization modeling of dust-bounded regions.

  1. Planck intermediate results. XLIII. Spectral energy distribution of dust in clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Adam, R.; Ade, P. A. R.; Aghanim, N.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bersanelli, M.; Bielewicz, P.; Bikmaev, I.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Burenin, R.; Burigana, C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Chiang, H. C.; Christensen, P. R.; Churazov, E.; Colombo, L. P. L.; Combet, C.; Comis, B.; Couchot, F.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Diego, J. M.; Dole, H.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Elsner, F.; Enßlin, T. A.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Ganga, K.; Génova-Santos, R. T.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Harrison, D. L.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Hornstrup, A.; Hovest, W.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Keihänen, E.; Keskitalo, R.; Khamitov, I.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Macías-Pérez, J. F.; Maffei, B.; Maggio, G.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Nørgaard-Nielsen, H. U.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Valenziano, L.; Valiviita, J.; Van Tent, F.; Vielva, P.; Villa, F.; Wade, L. A.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

    2016-12-01

    Although infrared (IR) overall dust emission from clusters of galaxies has been statistically detected using data from the Infrared Astronomical Satellite (IRAS), it has not been possible to sample the spectral energy distribution (SED) of this emission over its peak, and thus to break the degeneracy between dust temperature and mass. By complementing the IRAS spectral coverage with Planck satellite data from 100 to 857 GHz, we provide new constraints on the IR spectrum of thermal dust emission in clusters of galaxies. We achieve this by using a stacking approach for a sample of several hundred objects from the Planck cluster sample. This procedure averages out fluctuations from the IR sky, allowing us to reach a significant detection of the faint cluster contribution. We also use the large frequency range probed by Planck, together with component-separation techniques, to remove the contamination from both cosmic microwave background anisotropies and the thermal Sunyaev-Zeldovich effect (tSZ) signal, which dominate at ν ≤ 353 GHz. By excluding dominant spurious signals or systematic effects, averaged detections are reported at frequencies 353 GHz ≤ ν ≤ 5000 GHz. We confirm the presence of dust in clusters of galaxies at low and intermediate redshifts, yielding an SED with a shape similar to that of the Milky Way. Planck's resolution does not allow us to investigate the detailed spatial distribution of this emission (e.g. whether it comes from intergalactic dust or simply the dust content of the cluster galaxies), but the radial distribution of the emission appears to follow that of the stacked SZ signal, and thus the extent of the clusters. The recovered SED allows us to constrain the dust mass responsible for the signal and its temperature.

  2. Enhancement of features in galaxy images

    NASA Technical Reports Server (NTRS)

    Djorgovski, S.

    1986-01-01

    Several image-enhancement techniques useful for morphological analysis of galactic or cometary images are described and compared. Such techniques can be used to search for, and investigate the properties of dust lanes, stellar disks or rings, jets, shells, tidal distortions, etc. Applications of the techniques are illustrated on CCD images of the peculiar galaxy Arp 230; this object has a rich morphology, indicative of a merger of two disk galaxies.

  3. Gas and Dust Properties in Dwarf Irregular Galaxies

    NASA Technical Reports Server (NTRS)

    Jones, A. P.; Madden, S. C.; Colgan, S. W. J.; Geis, N.; Haas, M.; Maloney, P.; Nikola, T.; Poglitsch, A.

    1997-01-01

    We present a study of the 158 (micron)meter [C II] fine structure emission line from a sample of 11 low metallicity irregular galaxies using the NASA Kuiper Airborne Observatory (KAO). Our preliminary results demonstrate that the ratio of the 158 (micron)meter [C II] emission to the CO-12(1 yields 0) emission ranges from 6,000 to 46,000. These ratios are significantly enhanced relative to clouds within the Galaxy and to normal metallicity galaxies, which typically have values in the range 2,000 to 6,300. We also find that the [C II] emission in dwarf irregular galaxies can be up to 5% of the far-infrared (FIR) emission, a higher fraction of the FIR than in normal metallicity galaxies. We discuss these results for the dwarf irregular galaxies and compare them to those observed in normal metallicity galaxies. The enhanced 158 (micron)meter [C II] emission relative to CO-12(1 yields 0) emission can be understood in terms of the increased penetration depth of ultraviolet (UV) photons into the clouds in low metallicity environments.

  4. The Herschel Reference Survey: Dust in Early-type Galaxies and across the Hubble Sequence

    NASA Astrophysics Data System (ADS)

    Smith, M. W. L.; Gomez, H. L.; Eales, S. A.; Ciesla, L.; Boselli, A.; Cortese, L.; Bendo, G. J.; Baes, M.; Bianchi, S.; Clemens, M.; Clements, D. L.; Cooray, A. R.; Davies, J. I.; De Looze, I.; di Serego Alighieri, S.; Fritz, J.; Gavazzi, G.; Gear, W. K.; Madden, S.; Mentuch, E.; Panuzzo, P.; Pohlen, M.; Spinoglio, L.; Verstappen, J.; Vlahakis, C.; Wilson, C. D.; Xilouris, E. M.

    2012-04-01

    We present Herschel observations of 62 early-type galaxies (ETGs), including 39 galaxies morphologically classified as S0+S0a and 23 galaxies classified as ellipticals using SPIRE at 250, 350, and 500 μm as part of the volume-limited Herschel Reference Survey (HRS). We detect dust emission in 24% of the ellipticals and 62% of the S0s. The mean temperature of the dust is langTd rang = 23.9 ± 0.8 K, warmer than that found for late-type galaxies in the Virgo Cluster. The mean dust mass for the entire detected early-type sample is logMd = 6.1 ± 0.1 M ⊙ with a mean dust-to-stellar-mass ratio of log(Md /M *) = -4.3 ± 0.1. Including the non-detections, these parameters are logMd = 5.6 ± 0.1 and log(Md /M *) = -5.1 ± 0.1, respectively. The average dust-to-stellar-mass ratio for the early-type sample is fifty times lower, with larger dispersion, than the spiral galaxies observed as part of the HRS, and there is an order-of-magnitude decline in Md /M * between the S0s and ellipticals. We use UV and optical photometry to show that virtually all the galaxies lie close to the red sequence yet the large number of detections of cool dust, the gas-to-dust ratios, and the ratios of far-infrared to radio emission all suggest that many ETGs contain a cool interstellar medium similar to that in late-type galaxies. We show that the sizes of the dust sources in S0s are much smaller than those in early-type spirals and the decrease in the dust-to-stellar-mass ratio from early-type spirals to S0s cannot simply be explained by an increase in the bulge-to-disk ratio. These results suggest that the disks in S0s contain much less dust (and presumably gas) than the disks of early-type spirals and this cannot be explained simply by current environmental effects, such as ram-pressure stripping. The wide range in the dust-to-stellar-mass ratio for ETGs and the lack of a correlation between dust mass and optical luminosity suggest that much of the dust in the ETGs detected by Herschel has

  5. HEAVY DUST OBSCURATION OF z = 7 GALAXIES IN A COSMOLOGICAL HYDRODYNAMIC SIMULATION

    SciTech Connect

    Kimm, Taysun; Cen, Renyue

    2013-10-10

    Hubble Space Telescope observations with the Wide Field Camera 3/Infrared reveal that galaxies at z ∼ 7 have very blue ultraviolet (UV) colors, consistent with these systems being dominated by young stellar populations with moderate or little attenuation by dust. We investigate UV and optical properties of the high-z galaxies in the standard cold dark matter model using a high-resolution adaptive mesh refinement cosmological hydrodynamic simulation. For this purpose, we perform panchromatic three-dimensional dust radiative transfer calculations on 198 galaxies of stellar mass 5 × 10{sup 8}-3 × 10{sup 10} M{sub ☉} with three parameters: the dust-to-metal ratio, the extinction curve, and the fraction of directly escaped light from stars (f{sub esc}). Our stellar mass function is found to be in broad agreement with Gonzalez et al., independent of these parameters. We find that our heavily dust-attenuated galaxies (A{sub V} ∼ 1.8) can also reasonably match modest UV-optical colors, blue UV slopes, as well as UV luminosity functions, provided that a significant fraction (∼10%) of light directly escapes from them. The observed UV slope and scatter are better explained with a Small-Magellanic-Cloud-type extinction curve, whereas a Milky-Way-type curve also predicts blue UV colors due to the 2175 Å bump. We expect that upcoming observations by the Atacama Large Millimeter/submillimeter Array will be able to test this heavily obscured model.

  6. The Herschel Virgo Cluster Survey . VII. Dust in cluster dwarf elliptical galaxies

    NASA Astrophysics Data System (ADS)

    De Looze, I.; Baes, M.; Zibetti, S.; Fritz, J.; Cortese, L.; Davies, J. I.; Verstappen, J.; Bendo, G. J.; Bianchi, S.; Clemens, M.; Bomans, D. J.; Boselli, A.; Corbelli, E.; Dariush, A.; di Serego Alighieri, S.; Fadda, D.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Grossi, M.; Hughes, T. M.; Hunt, L. K.; Jones, A. P.; Madden, S.; Pierini, D.; Pohlen, M.; Sabatini, S.; Smith, M. W. L.; Vlahakis, C.; Xilouris, E. M.

    2010-07-01

    We use the science demonstration phase data of the Herschel Virgo Cluster Survey to search for dust emission of early-type dwarf galaxies in the central regions of the Virgo cluster as an alternative way of identifying the interstellar medium. We present the first possible far-infrared detection of cluster early-type dwarf galaxies: VCC 781 and VCC 951 are detected at the 10σ level in the SPIRE 250 μm image. Both detected galaxies have dust masses of the order of 105 M_⊙ and average dust temperatures ≈20 K. The detection rate (less than 1%) is quite high compared to the 1.7% detection rate for Hi emission, considering that dwarfs in the central regions are more Hi deficient. We conclude that the removal of interstellar dust from dwarf galaxies resulting from ram pressure stripping, harassment, or tidal effects must be as efficient as the removal of interstellar gas. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  7. The dust energy balance in the edge-on spiral galaxy NGC 4565

    NASA Astrophysics Data System (ADS)

    De Looze, Ilse; Baes, Maarten; Bendo, George J.; Ciesla, Laure; Cortese, Luca; de Geyter, Gert; Groves, Brent; Boquien, Médéric; Boselli, Alessandro; Brondeel, Lena; Cooray, Asantha; Eales, Steve; Fritz, Jacopo; Galliano, Frédéric; Gentile, Gianfranco; Gordon, Karl D.; Hony, Sacha; Law, Ka-Hei; Madden, Suzanne C.; Sauvage, Marc; Smith, Matthew W. L.; Spinoglio, Luigi; Verstappen, Joris

    2012-12-01

    We combine new dust continuum observations of the edge-on spiral galaxy NGC 4565 in all Herschel/Spectral and Photometric Imaging Receiver (250, 350 and 500 μm) wavebands, obtained as part of the Herschel Reference Survey, and a large set of ancillary data (Spitzer, Sloan Digital Sky Survey, Galaxy Evolution Explorer) to analyse its dust energy balance. We fit a radiative transfer model for the stars and dust to the optical maps with the fitting algorithm FITSKIRT. To account for the observed ultraviolet and mid-infrared emission, this initial model was supplemented with both obscured and unobscured star-forming regions. Even though these star-forming complexes provide an additional heating source for the dust, the far-infrared/submillimetre emission long wards of 100 μm is underestimated by a factor of 3-4. This inconsistency in the dust energy budget of NGC 4565 suggests that a sizable fraction (two-thirds) of the total dust reservoir (Md ˜ 2.9 × 108 M⊙) consists of a clumpy distribution with no associated young stellar sources. The distribution of those dense dust clouds would be in such a way that they remain unresolved in current far-infrared/submillimetre observations and hardly contribute to the attenuation at optical wavelengths. More than two-thirds of the dust heating in NGC 4565 is powered by the old stellar population, with localized embedded sources supplying the remaining dust heating in NGC 4565. The results from this detailed dust energy balance study in NGC 4565 are consistent with that of similar analyses of other edge-on spirals.

  8. Environmental impacts on dust temperature of star-forming galaxies in the local Universe

    NASA Astrophysics Data System (ADS)

    Matsuki, Yasuhiro; Koyama, Yusei; Nakagawa, Takao; Takita, Satoshi

    2017-04-01

    We present infrared views of the environmental effects on the dust properties in star-forming (SF) galaxies at z ∼ 0, using the AKARI Far-Infrared Surveyor all-sky map and the large spectroscopic galaxy sample from Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We restrict the sample to those within the redshift range of 0.05 < z < 0.07 and the stellar mass range of 9.2 < log 10(M*/M⊙). We select SF galaxies based on their Hα equivalent width (EWHα > 4 Å) and emission line flux ratios. We perform far-infrared (FIR) stacking analyses by splitting the SDSS SF galaxy sample according to their stellar mass, specific star formation rate (SSFRSDSS), and environment. We derive total infrared luminosity (LIR) for each subsample using the average flux densities at WIDE-S (90 μm) and WIDE-L (140 μm) bands, and then compute infrared (IR)-based SFR (SFRIR) from LIR. We find a mild decrease of IR-based SSFR (SSFRIR) amongst SF galaxies with increasing local density (∼0.1-dex level at maximum), which suggests that environmental effects do not instantly shut down the SF activity in galaxies. We also derive average dust temperature (Tdust) using the flux densities at 90 and 140 μm bands. We confirm a strong positive correlation between Tdust and SSFRIR, consistent with recent studies. The most important finding of this study is that we find a marginal trend that Tdust increases with increasing environmental galaxy density. Although the environmental trend is much milder than the SSFR-Tdust correlation, our results suggest that the environmental density may affect the dust temperature in SF galaxies, and that the physical mechanism which is responsible for this phenomenon is not necessarily specific to cluster environments because the environmental dependence of Tdust holds down to relatively low-density environments.

  9. Interstellar Silicate Dust Grain Properties in Distant Galaxies Probed by Quasar Absorption Systems

    NASA Astrophysics Data System (ADS)

    Aller, Monique C.; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam

    2015-01-01

    Dust grains are a fundamental component of the interstellar medium, and significantly impact many of the physical processes driving galaxy evolution, including star formation, and the heating, cooling and ionization of interstellar material. Using the absorption features produced by dust in the spectra of luminous background quasars, it is possible to study the properties of extragalactic interstellar dust grains. We will present results from an ongoing program utilizing existing Spitzer Space Telescope infrared quasar spectra to probe silicate dust grain properties in z<1.4 quasar absorption systems. In combination with complementary ground-based data on associated gas-phase metal absorption lines, we explore connections between the interstellar dust and gas in the quasar absorption systems. Our project yields clear detections of the 10 micron silicate dust absorption feature in the studied systems, as well as detections of the 18 micron silicate dust absorption feature in sources with adequate spectral coverage. Based on measured variations in the breath, peak wavelength, and substructure of the 10 micron absorption features, there appear to be differences in the silicate dust grain properties from system-to-system. We also show indications of trends between the gas-phase metal properties, such as metallicity and gas velocity spread, with the silicate dust grain absorption properties. Support for this work is provided by NASA through an award issued by JPL/Caltech and through NASA grant NNX14AG74G, and from National Science Foundation grants AST-0908890 and AST-1108830 to the University of South Carolina.

  10. Cool dust heating and temperature mixing in nearby star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Hunt, L. K.; Draine, B. T.; Bianchi, S.; Gordon, K. D.; Aniano, G.; Calzetti, D.; Dale, D. A.; Helou, G.; Hinz, J. L.; Kennicutt, R. C.; Roussel, H.; Wilson, C. D.; Bolatto, A.; Boquien, M.; Croxall, K. V.; Galametz, M.; Gil de Paz, A.; Koda, J.; Muñoz-Mateos, J. C.; Sandstrom, K. M.; Sauvage, M.; Vigroux, L.; Zibetti, S.

    2015-04-01

    Physical conditions of the interstellar medium in galaxies are closely linked to the ambient radiation field and the heating of dust grains. In order to characterize dust properties in galaxies over a wide range of physical conditions, we present here the radial surface brightness profiles of the entire sample of 61 galaxies from Key Insights into Nearby Galaxies: Far-Infrared Survey with Herschel (KINGFISH). The main goal of our work is the characterization of the grain emissivities, dust temperatures, and interstellar radiation fields (ISRFs) responsible for heating the dust. We first fit the radial profiles with exponential functions in order to compare stellar and cool-dust disk scalelengths, as measured by 3.6 μm and 250 μm surface brightnesses. Our results show thatthe stellar and dust scalelengths are comparable, with a mean ratio of 1.04, although several galaxies show dust-to-stellar scalelength ratios of 1.5 or more. We then fit the far-infrared spectral energy distribution (SED) in each annular region with single-temperature modified blackbodies using both variable (MBBV) and fixed (MBBF) emissivity indices β, as well as with physically motivated dust models. The KINGFISH profiles are well suited to examining trends of dust temperature Tdust and β because they span a factor of ~200 in the ISRF intensity heating the bulk of the dust mass, Umin. Results from fitting the profile SEDs suggest that, on average, Tdust, dust optical depth τdust, and Umin decrease with radius. The emissivity index β also decreases with radius in some galaxies, but in others is increasing, or rising in the inner regions and falling in the outer ones. Despite the fixed grain emissivity (average β ~ 2.1) of the physically-motivated models, they are well able to accommodate flat spectral slopes with β ≲ 1. An analysis of the wavelength variations of dust emissivities in both the data and the models shows that flatter slopes (β ≲ 1.5) are associated with cooler

  11. Variations in the Dust-to-Gas Ratio in Nearby Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Schruba, Andreas; Walter, F.; Leroy, A.; Kennicutt, R.; Lee, J.; Gil de Paz, A.; Hunter, D.; Ott, J.

    2009-05-01

    We present the first part of a systematic study of the relationship between dust and gas in a large set of nearby dwarf irregular galaxies. These systems are rich in gas but poor in dust and heavy elements, a contrast that sets them apart from the Milky Way and other nearby spiral galaxies. The central role of dust in the creation and shielding of star-forming gas and its close link to the enrichment of the ISM make the dust-to-gas (DGR) ratio a key observable to understand star formation in these systems. We are combining maps of dust emission taken by Spitzer as part of the Local Volume Legacy (LVL) with atomic gas observations by the VLA large programs LITTLE THINGS, VLA-ANGST, and THINGS to measure the DGR as a function of position in a large sample of dwarf galaxies. This will populate the low end of the DGR vs. metallicity relation and allow us to measure the enrichment of the extended HI envelopes that surround many dwarf irregulars. By comparing the DGR in regions of active star formation to the DGR in nearby quiescent, we can also place an upper limit on the amount of H2 that can be present near the star forming peaks, a quantity that is otherwise difficult to constrain.

  12. Stellar Evolutionary Effects on the Abundances of Polycyclic Aromatic Hydrocarbons and Supernova-Condensed Dust in Galaxies

    NASA Astrophysics Data System (ADS)

    Galliano, Frédéric; Dwek, Eli; Chanial, Pierre

    2008-01-01

    Spectral and photometric observations of nearby galaxies show a correlation between the strength of their mid-IR aromatic features, attributed to PAH molecules, and their metal abundances, leading to a deficiency of these features in low-metallicity galaxies. In this paper we suggest that the observed correlation represents a trend of PAH abundance with galactic age, reflecting the delayed injection of carbon dust into the ISM by AGB stars in the final post-AGB phase of their evolution. AGB stars are the primary sources of PAHs and carbon dust in galaxies, and recycle their ejecta back to the ISM after only a few hundred million years of evolution on the main sequence. In contrast, more massive stars that explode as Type II supernovae inject their metals and dust almost instantaneously after their formation. We first determined the PAH abundance in galaxies by constructing detailed models of UV-to-radio SEDs of galaxies that estimate the contribution of dust in PAH-free H II regions, and of PAHs and dust in photodissociation regions, to the IR emission. All model components, the galaxies' stellar content, the properties of their H II regions, and their ionizing and nonionizing radiation fields and dust abundances, are constrained by their observed multiwavelength spectra. After determining the PAH and dust abundances in 35 nearby galaxies using our SED model, we use a chemical evolution model to show that the delayed injection of carbon dust by AGB stars provides a natural explanation for the dependence of the PAH content in galaxies on metallicity. We also show that larger dust particles giving rise to the far-IR emission follow a distinct evolutionary trend closely related to the injection of dust by massive stars into the ISM.

  13. Effects of Metallicity and AGN Activity on the Mid-Infrared Dust Emission of Galaxies

    NASA Astrophysics Data System (ADS)

    Wu, Hong; Zhu, Yi-Nan; Cao, Chen; Qin, Bo

    2007-10-01

    Using a sample of the Spitzer SWIRE-field galaxies whose optical spectra are taken from Data Release 4 of the Sloan Digital Sky Survey, we study possible correlations between the mid-infrared (MIR) dust emission from these galaxies and both their metallicities and AGN activities. We find that both metallicity and AGN activity are well correlated with the following ratios: PAH-to-star, VSG-to-star, and PAH-to-VSG, which can be characterized by νLν[8 μm(dust)]/νLν[3.6 μm], νLν[24 μm]/νLν[3.6 μm], and νLν[8 μm(dust)]/νLν[24 μm], respectively. We argue that our MIR-metallicity correlation could be explained by either the amount of dust (ongoing dust formation) or dust destruction (PAHs and VSGs could be destroyed by hard and intense radiation fields), and that the MIR-AGN correlation could arise due to either PAH destruction or an enhanced VSG continuum by the central AGN.

  14. DUST CONTINUUM EMISSION AS A TRACER OF GAS MASS IN GALAXIES

    SciTech Connect

    Groves, Brent A.; Schinnerer, Eva; Walter, Fabian; Leroy, Adam; Galametz, Maud; Bolatto, Alberto; Hunt, Leslie; Dale, Daniel; Calzetti, Daniela; Croxall, Kevin; Kennicutt, Robert Jr.

    2015-01-20

    We use a sample of 36 galaxies from the KINGFISH (Herschel IR), HERACLES (IRAM CO), and THINGS (Very Large Array H I) surveys to study empirical relations between Herschel infrared (IR) luminosities and the total mass of the interstellar gas (H{sub 2} + H I). Such a comparison provides a simple empirical relationship without introducing the uncertainty of dust model fitting. We find tight correlations, and provide fits to these relations, between Herschel luminosities and the total gas mass integrated over entire galaxies, with the tightest, almost linear, correlation found for the longest wavelength data (SPIRE 500). However, we find that accounting for the gas-phase metallicity (affecting the dust to gas ratio) is crucial when applying these relations to low-mass, and presumably high-redshift, galaxies. The molecular (H{sub 2}) gas mass is found to be better correlated with the peak of the IR emission (e.g., PACS160), driven mostly by the correlation of stellar mass and mean dust temperature. When examining these relations as a function of galactocentric radius, we find the same correlations, albeit with a larger scatter, up to a radius of r ∼ 0.7 r {sub 25} (containing most of a galaxy's baryonic mass). However, beyond that radius, the same correlations no longer hold, with increasing gas (predominantly H I) mass relative to the infrared emission. The tight relations found for the bulk of the galaxy's baryonic content suggest that total gas masses of disk-like (non-merging/ULIRG) galaxies can be inferred from far-infrared continuum measurements in situations where only the latter are available, e.g., in ALMA continuum observations of high-redshift galaxies.

  15. Hubble Space Telescope and Very Large Array Observations of the H2O Gigamaser Galaxy TXS 2226-184.

    PubMed

    Falcke; Wilson; Henkel; Brunthaler; Braatz

    2000-02-10

    We present Hubble Space Telescope/Wide-Field and Planetary Camera 2 images in Halpha + [N ii] lambdalambda6548, 6583 lines and continuum radiation and a VLA map at 8 GHz of the H2O gigamaser galaxy TXS 2226-184. This galaxy has the most luminous H2O maser emission known to date. Our red continuum images reveal a highly elongated galaxy with a dust lane crossing the nucleus. The surface brightness profile is best fitted by a bulge plus exponential disk model, favoring classification as a highly inclined spiral galaxy (i=70&j0;). The color map confirms that the dust lane is aligned with the galaxy major axis and is crossing the putative nucleus. The Halpha + [N ii] map exhibits a gaseous, jetlike structure perpendicular to the nuclear dust lane and the galaxy major axis. The radio map shows compact, steep spectrum emission that is elongated in the same direction as the Halpha + [N ii] emission. By analogy with Seyfert galaxies, we therefore suspect that this alignment reflects an interaction between the radio jet and the interstellar medium. The axes of the nuclear dust disk, the radio emission, and the optical line emission apparently define the axis of the active galactic nucleus. The observations suggest that in this galaxy the nuclear accretion disk, obscuring torus, and large-scale molecular gas layer are roughly coplanar. Our classification of the host galaxy strengthens the trend for megamasers to be found preferentially in highly inclined spiral galaxies.

  16. Extended Red Emission in the Evil Eye Galaxy

    NASA Astrophysics Data System (ADS)

    Majeed, A.; Witt, A. N.; Boroson, T. A.

    1999-05-01

    The Evil Eye galaxy (NGC 4826; M64) is distinguished by an asymmetrically placed, strongly absorbing dust lane across its prominent bulge. We obtained a long-slit spectrum (KPNO 4-m; 5000 Angstroms to 9500 Angstroms) of NGC 4826, with the slit across the galaxy's nucleus, covering equal parts of the obscured and the unobscured portions of the bulge. By comparing the spectral energy distributions at corresponding positions on the bulge, symmetrically placed with respect to the nucleus, we were able to study the wavelength dependent effects of absorption, scattering, and emission by the dust, as well as the presence of ongoing star formation in the dust lane. We report the detection of strong extended red emission (ERE) from the dust lane within about 15 arcsec distance from the nucleus of NGC 4826. The ERE band extends from 5400 Angstroms to 9400 Angstroms , with a peak near 8800 Angstroms. The integrated ERE intensity is about 75 % of that of the estimated scattered light from the dust lane. The ERE shifts toward longer wavelengths and diminishes in intensity as a region of star formation, located beyong 15 arcsec distance, is approached. We interpret the ERE as originating in photoluminescence by nanometer-sized clusters, illuminated by the galaxy's radiation field, in addition to the illumination by the star-forming complex within the dust lane. When examined within the context of ERE observations in the diffuse ISM of our Galaxy and in a variety of other dusty environments such as nebulae, we conclude that the ERE photon conversion efficiency in NGC 4826 is as high as found elsewhere, but that the size of the nanoparticles in NGC 4826 is about twice as large as those thought to exist in the diffuse ISM of our Galaxy.

  17. Herschel-ATLAS/GAMA: a census of dust in optically selected galaxies from stacking at submillimetre wavelengths

    NASA Astrophysics Data System (ADS)

    Bourne, N.; Maddox, S. J.; Dunne, L.; Auld, R.; Baes, M.; Baldry, I. K.; Bonfield, D. G.; Cooray, A.; Croom, S. M.; Dariush, A.; de Zotti, G.; Driver, S. P.; Dye, S.; Eales, S.; Gomez, H. L.; González-Nuevo, J.; Hopkins, A. M.; Ibar, E.; Jarvis, M. J.; Lapi, A.; Madore, B.; Michałowski, M. J.; Pohlen, M.; Popescu, C. C.; Rigby, E. E.; Seibert, M.; Smith, D. J. B.; Tuffs, R. J.; van der Werf, P.; Brough, S.; Buttiglione, S.; Cava, A.; Clements, D. L.; Conselice, C. J.; Fritz, J.; Hopwood, R.; Ivison, R. J.; Jones, D. H.; Kelvin, L. S.; Liske, J.; Loveday, J.; Norberg, P.; Robotham, A. S. G.; Rodighiero, G.; Temi, P.

    2012-04-01

    We use the Herschel-ATLAS survey to conduct the first large-scale statistical study of the submillimetre properties of optically selected galaxies. Using ˜80 000 r-band selected galaxies from 126 deg2 of the GAMA survey, we stack into submillimetre imaging at 250, 350 and 500 μ m to gain unprecedented statistics on the dust emission from galaxies at z < 0.35. We find that low-redshift galaxies account for 5 per cent of the cosmic 250-μm background (4 per cent at 350 μ m; 3 per cent at 500 μ m), of which approximately 60 per cent comes from 'blue' and 20 per cent from 'red' galaxies (rest-frame g-r). We compare the dust properties of different galaxy populations by dividing the sample into bins of optical luminosity, stellar mass, colour and redshift. In blue galaxies we find that dust temperature and luminosity correlate strongly with stellar mass at a fixed redshift, but red galaxies do not follow these correlations and overall have lower luminosities and temperatures. We make reasonable assumptions to account for the contaminating flux from lensing by red-sequence galaxies and conclude that galaxies with different optical colours have fundamentally different dust emission properties. Results indicate that while blue galaxies are more luminous than red galaxies due to higher temperatures, the dust masses of the two samples are relatively similar. Dust mass is shown to correlate with stellar mass, although the dust-to-stellar mass ratio is much higher for low stellar mass galaxies, consistent with the lowest mass galaxies having the highest specific star formation rates. We stack the 250 μ m-to-NUV luminosity ratio, finding results consistent with greater obscuration of star formation at lower stellar mass and higher redshift. Submillimetre luminosities and dust masses of all galaxies are shown to evolve strongly with redshift, indicating a fall in the amount of obscured star formation in ordinary galaxies over the last four billion years.

  18. The low filling factor of dust in the Galaxy

    NASA Astrophysics Data System (ADS)

    Murthy, Jayant; Walker, H. J.; Henry, R. C.

    1992-12-01

    The neighborhood of 745 luminous stars in the IRAS Skyflux plates was examined for the presence of dust heated by the nearby star. One-hundred twenty-three dust clouds were found around only 106 of the stars with a volume filling factor of 0.006 and an intercloud separation of 46 pc. Nowhere was a region found where the dust is smoothly distributed through the volume of space heated by the star; hence an upper limit of 0.06/cu cm is placed on the equivalent gas density in the intercloud regions. Due to the lack of IR emission near the star, it is found that less than 1 percent of the stellar luminosity is reprocessed within 10 pc of the star. The clouds have an average density of 0.22/cu cm and a radius of 1.9 pc, albeit with wide variations in their properties. Two different scale heights of 140 and 540 pc were found for the number of clouds around different groups of stars, which are interpreted as evidence for different distributions of dust in and out of the Galactic disk.

  19. Do Lyman-alpha photons escape from star-forming galaxies through dust-holes?

    NASA Astrophysics Data System (ADS)

    Wofford, Aida

    2012-10-01

    The hydrogen Lyman-alpha line is arguably the most important signature of galaxies undergoing their first violent burst of star formation. Although Lya photons are easily destroyed by dust, candidate Lya emitters have been detected at z>5. Thus the line can potentially be used to probe galaxy formation and evolution, as long as the astrophysical processes that regulate the escape of Lya photons from star-forming galaxies are well understood.We request 15 orbits for imaging in Lya and the FUV continuum with ACS/SBC, and in the H-beta/H-alpha ratio {proxy for dust extinction} with WFC3/UVIS, a sample of isolated non-AGN face-on spirals for which our team previously obtained and analyzed COS FUV spectroscopy of the central regions. Each target shows a different Lya profile, i.e., pure absorption, P-Cygni like, and multiple-emission. From the COS data, we already know the starburst phase and H I gas velocity. The images would greatly increase the impact of our spectroscopic study by enabling us to 1} conclusively determine if Lya photons escape through dust-holes, 2} assess the relative importance of dust extinction, ISM kinematics, and starburst phase in regulating the Lya escape, 3} clarify what we can really learn from the Lya equivalent width, and 4} provide constraints on the dust extinction to Lya 3D radiative transfer models. Ultimately this program will inform our understanding of the Lya escape at high redshift by providing spatially resolved views of the local conditions within star-forming galaxies that favor escape.

  20. Dust Properties, Star Formation, and Chemical Enrichment of Low Luminosity Galaxies

    NASA Astrophysics Data System (ADS)

    van Zee, Liese; Marble, Andrew; Englebracht, Charles; Skillman, Evan

    2009-08-01

    The recently completed Local Volume Legacy (LVL) survey has yielded multi-wavelength observations from the ultraviolet to the radio for a volume-complete sample of 258 galaxies in the local universe, providing detailed information about their star formation rates and dust content. We propose to leverage this rich dataset by obtaining oxygen abundance metallicity measurements for 28 of the lowest luminosity LVL galaxies, in order to investigate the relationship between dust properties, metallicity, and star formation at low-luminosity. Recent studies have suggested departures in this regime from known correlations at higher luminosity; however, these findings have been based on only a few low- luminosity galaxies. Specifically, although the weakening of the aromatic emission features in low luminosity galaxies has largely been ascribed to a metallicity effect, high star formation intensities could also produce the observed trends. The proposed observations will target low luminosity galaxies with low star formation rates (< 0.005 M_⊙ yr^-1) in order to explore the full range of parameter space to determine if the observed behavior of the emission from the IR aromatic features is driven primarily by metallicity or star formation.

  1. Type 2 Quasars at the heart of dust-obscured galaxies (DOGs) at high z

    NASA Astrophysics Data System (ADS)

    Piconcelli, E.; Lanzuisi, G.; Fiore, F.; Feruglio, C.; Vignali, C.; Salvato, M.; Gruppioni, C.

    2010-07-01

    Dust-obscured galaxies (DOGs) represent a recently-discovered, intriguing class of mid-IR luminous sources at high redshifts. Evidence is mounting that DOGs (selected on the basis of extreme optical/mid-IR color cut and high mid-IR flux level) may represent systems caught in the process of host galaxy formation and intense SMBH growth. Here we report the results of an X-ray spectroscopic survey aimed at studying the X-ray properties of these sources and establishing the fraction of Type 2 quasars among them.

  2. DUST-OBSCURED STAR FORMATION IN INTERMEDIATE REDSHIFT GALAXY CLUSTERS

    SciTech Connect

    Finn, Rose A.; Desai, Vandana; Rudnick, Gregory; Poggianti, Bianca; Bell, Eric F.; Hinz, Joannah; Zaritsky, Dennis; Jablonka, Pascale; Milvang-Jensen, Bo; Moustakas, John; Rines, Kenneth E-mail: jmoustakas@ucsd.ed

    2010-09-01

    We present Spitzer MIPS 24 {mu}m observations of sixteen 0.4 < z < 0.8 galaxy clusters drawn from the ESO Distant Cluster Survey. This is the first large 24 {mu}m survey of clusters at intermediate redshift. The depth of our imaging corresponds to a total IR luminosity of 8 x 10{sup 10} L{sub sun}, just below the luminosity of luminous infrared galaxies (LIRGs), and 6{sup +1}{sub -1}% of M{sub V} < -19 cluster members show 24 {mu}m emission at or above this level. We compare with a large sample of coeval field galaxies and find that while the fraction of cluster LIRGs lies significantly below that of the field, the IR luminosities of the field and cluster galaxies are consistent. However, the stellar masses of the EDisCS LIRGs are systematically higher than those of the field LIRGs. A comparison with optical data reveals that {approx}80% of cluster LIRGs are blue and the remaining 20% lie on the red sequence. Of LIRGs with optical spectra, 88{sup +4} {sub -5}% show [O II] emission with EW([O II]) > 5 A, and {approx}75% exhibit optical signatures of dusty starbursts. On average, the fraction of cluster LIRGs increases with projected clustercentric radius but remains systematically lower than the field fraction over the area probed (<1.5x R {sub 200}). The amount of obscured star formation declines significantly over the 2.4 Gyr interval spanned by the EDisCS sample, and the rate of decline is the same for the cluster and field populations. Our results are consistent with an exponentially declining LIRG fraction, with the decline in the field delayed by {approx}1 Gyr relative to the clusters.

  3. Finding and Studying Luminous Dust-Enshrouded Galaxies

    NASA Astrophysics Data System (ADS)

    Blain, A. W.

    2009-12-01

    This meeting was convened to celebrate the career and science interests of Tom Phillips. The possibility of investigating the physics and chemistry of the molecular interstellar medium (ISM) in galaxies, at mm/submm wavelengths has been enabled by many, but Tom's long-standing and consistent contributions are amongst the greatest. Here I will summarize some of the key developments and prospects for better understanding galaxy evolution, by exploiting the energy generated by stars and active galactic nuclei (AGNs) after it has been absorbed and reprocessed by the solid and gaseous components of the ISM. I highlight the difficulties of identifying and diagnosing the discovered objects. The initial burst of activity associated with the galaxies detected when the first mm/submm-wave imaging instruments were fielded is maturing; however, the advent of in particular Herschel Space Observatory (Herschel), the Atacama Large (Sub-)Millimeter Array (ALMA) and the Cornell-Caltech Atacama Telescope (CCAT) mean that the complimentary view provided by far-infrared (IR) sensors to reveal both the detailed astrophysics of star formation taking place star by star, and of the great bursts of activity seen across the Universe is becoming much more powerful.

  4. DUST EXTINCTION AND METALLICITIES OF STAR-FORMING Ly{alpha} EMITTING GALAXIES AT LOW REDSHIFT

    SciTech Connect

    Finkelstein, Steven L.; Papovich, Casey; Cohen, Seth H.; Malhotra, Sangeeta; Rhoads, James E.; Moustakas, John

    2011-06-01

    We present the results of an optical spectroscopic study of 12 GALEX-discovered star-forming Ly{alpha} emitting galaxies (LAEs) at z {approx} 0.3. We measure the emission-line fluxes from these galaxies by fitting their observed spectra to stellar population models in order to correct for underlying stellar absorption. We revisit earlier stellar population model fitting results, finding that excluding now-known active galactic nuclei lowers the typical stellar population age and stellar mass of this sample to {approx}300 Myr and {approx}4 x 10{sup 9} M{sub sun}, respectively. We calculate their dust extinction using the Balmer decrement, and find a typical visual attenuation of A{sub V} {approx} 0.3 mag, similar to that seen in some high-redshift LAEs. Comparing the ratios of Ly{alpha}/H{alpha} and the Ly{alpha} equivalent widths to the measured dust extinction, we find that the interstellar media (ISMs) in these objects appear to be neither enhancing nor seriously attenuating the Ly{alpha} equivalent widths, as would be the case in a quasi-clumpy ISM. Lastly, we perform a detailed analysis of the gas-phase metallicities of these galaxies, and we find that most galaxies in our sample have Z {approx}< 0.4 Z{sub sun}. We find that at a fixed stellar mass, these low-redshift LAE analogs are offset by {approx}0.3-0.6 dex lower metallicity from the general galaxy population at similar redshifts based on the local mass-metallicity relationship. This implies that galaxies with Ly{alpha} in emission may be systematically more metal-poor than star-forming galaxies at the same stellar mass and redshift, similar to preliminary results at z {approx} 2.

  5. Characterizing Dust Attenuation in Local Star-forming Galaxies: Near-infrared Reddening and Normalization

    NASA Astrophysics Data System (ADS)

    Battisti, A. J.; Calzetti, D.; Chary, R.-R.

    2017-05-01

    We characterize the near-infrared dust attenuation for a sample of ˜5500 local (z≲ 0.1) star-forming galaxies and obtain an estimate of their average total-to-selective attenuation k(λ ). We utilize data from the United Kingdom Infrared Telescope and the Two-Micron All Sky Survey, which is combined with previously measured UV-optical data for these galaxies. The average attenuation curve is slightly lower in the far-ultraviolet than in local starburst galaxies by roughly 15% but appears similar at longer wavelengths with a total-to-selective normalization of {R}V={3.67}-0.35+0.44. Under the assumption of energy balance, the total attenuated energy inferred from this curve is found to be broadly consistent with the observed infrared dust emission ({L}{TIR}) in a small sample of local galaxies for which far-infrared measurements are available. However, the significant scatter in this quantity among the sample may reflect large variations in the attenuation properties of individual galaxies. We also derive the attenuation curve for subpopulations of the main sample, separated according to mean stellar population age (via {D}n4000), specific star formation rate, stellar mass, and metallicity, and find that they show only tentative trends with low significance, at least over the range that is probed by our sample. These results indicate that a single curve is reasonable for applications seeking to broadly characterize large samples of galaxies in the local universe, while applications to individual galaxies would yield large uncertainties and is not recommended.

  6. VARIATIONS OF MID- AND FAR-INFRARED LUMINOSITIES AMONG EARLY-TYPE GALAXIES: RELATION TO STELLAR METALLICITY AND COLD DUST

    SciTech Connect

    Mathews, William G.; Brighenti, Fabrizio

    2013-05-01

    The Hubble morphological sequence from early to late galaxies corresponds to an increasing rate of specific star formation. The Hubble sequence also follows a banana-shaped correlation between 24 and 70 {mu}m luminosities, both normalized with the K-band luminosity. We show that this correlation is significantly tightened if galaxies with central active galactic nucleus (AGN) emission are removed, but the cosmic scatter of elliptical galaxies in both 24 and 70 {mu}m luminosities remains significant along the correlation. We find that the 24 {mu}m variation among ellipticals correlates with stellar metallicity, reflecting emission from hot dust in winds from asymptotic giant branch stars of varying metallicity. Infrared surface brightness variations in elliptical galaxies indicate that the K - 24 color profile is U-shaped for reasons that are unclear. In some elliptical galaxies, cold interstellar dust emitting at 70 and 160 {mu}m may arise from recent gas-rich mergers. However, we argue that most of the large range of 70 {mu}m luminosity in elliptical galaxies is due to dust transported from galactic cores by feedback events in (currently IR-quiet) AGNs. Cooler dusty gas naturally accumulates in the cores of elliptical galaxies due to dust-cooled local stellar mass loss and may accrete onto the central black hole, releasing energy. AGN-heated gas can transport dust in cores 5-10 kpc out into the hot gas atmospheres where it radiates extended 70 {mu}m emission but is eventually destroyed by sputtering. This, and some modest star formation, defines a cycle of dust creation and destruction. Elliptical galaxies evidently undergo large transient excursions in the banana plot in times comparable to the sputtering time or AGN duty cycle, 10 Myr. Normally regarded as passive, elliptical galaxies are the most active galaxies in the IR color-color correlation.

  7. Nebular and Stellar Dust Extinction Across the Disk of Emission-line Galaxies on Kiloparsec Scales

    NASA Astrophysics Data System (ADS)

    Hemmati, Shoubaneh; Mobasher, Bahram; Darvish, Behnam; Nayyeri, Hooshang; Sobral, David; Miller, Sarah

    2015-11-01

    We investigate the resolved kiloparsec-scale stellar and nebular dust distribution in eight star-forming galaxies at z ∼ 0.4 in the Great Observatories Origins Deep Survey fields. This is to get a better understanding of the effect of dust attenuation on measurements of physical properties and its variation with redshift. Constructing the observed spectral energy distributions (SEDs) per pixel, based on seven bands of photometric data from Hubble Space Telescope/Advanced Camera for Surveys and WFC3, we performed pixel-by-pixel SED fits to population synthesis models and estimated the small-scale distribution of stellar dust extinction. We use Hα/Hβ nebular emission line ratios from Keck/DEIMOS high-resolution spectra at each spatial resolution element to measure the amount of attenuation faced by ionized gas at different radii from the centers of galaxies. We find a good agreement between the integrated and median of resolved color excess measurements in our galaxies. The ratio of integrated nebular to stellar dust extinction is always greater than unity, but does not show any trend with stellar mass or star formation rate (SFR). We find that inclination plays an important role in the variation of the nebular to stellar excess ratio. The stellar color excess profiles are found to have higher values at the center compared to outer parts of the disk. However, for lower mass galaxies, a similar trend is not found for the nebular color excess. We find that the nebular color excess increases with stellar mass surface density. This explains the absence of radial trend in the nebular color excess in lower mass galaxies which lack a large radial variation of stellar mass surface density. Using standard conversions of SFR surface density to gas mass surface density, and the relation between dust mass surface density and color excess, we find no significant variation in the dust-to-gas ratio in regions with high gas mass surface densities over the scales probed in this

  8. NEBULAR AND STELLAR DUST EXTINCTION ACROSS THE DISK OF EMISSION-LINE GALAXIES ON KILOPARSEC SCALES

    SciTech Connect

    Hemmati, Shoubaneh; Mobasher, Bahram; Darvish, Behnam; Nayyeri, Hooshang; Miller, Sarah; Sobral, David

    2015-11-20

    We investigate the resolved kiloparsec-scale stellar and nebular dust distribution in eight star-forming galaxies at z ∼ 0.4 in the Great Observatories Origins Deep Survey fields. This is to get a better understanding of the effect of dust attenuation on measurements of physical properties and its variation with redshift. Constructing the observed spectral energy distributions (SEDs) per pixel, based on seven bands of photometric data from Hubble Space Telescope/Advanced Camera for Surveys and WFC3, we performed pixel-by-pixel SED fits to population synthesis models and estimated the small-scale distribution of stellar dust extinction. We use Hα/Hβ nebular emission line ratios from Keck/DEIMOS high-resolution spectra at each spatial resolution element to measure the amount of attenuation faced by ionized gas at different radii from the centers of galaxies. We find a good agreement between the integrated and median of resolved color excess measurements in our galaxies. The ratio of integrated nebular to stellar dust extinction is always greater than unity, but does not show any trend with stellar mass or star formation rate (SFR). We find that inclination plays an important role in the variation of the nebular to stellar excess ratio. The stellar color excess profiles are found to have higher values at the center compared to outer parts of the disk. However, for lower mass galaxies, a similar trend is not found for the nebular color excess. We find that the nebular color excess increases with stellar mass surface density. This explains the absence of radial trend in the nebular color excess in lower mass galaxies which lack a large radial variation of stellar mass surface density. Using standard conversions of SFR surface density to gas mass surface density, and the relation between dust mass surface density and color excess, we find no significant variation in the dust-to-gas ratio in regions with high gas mass surface densities over the scales probed in this

  9. Magnetohydrodynamic Simulations of Barred Galaxies

    NASA Astrophysics Data System (ADS)

    Kim, W.-T.

    2013-04-01

    Magnetic fields are pervasive in barred galaxies, especially in gaseous substructures such as dust lanes and nuclear rings. To explore the effects of magnetic fields on the formation of the substructures as well as on the mass inflow rates to the galaxy center, we run two-dimensional, ideal magnetohydrodynamic simulations. We use a modified version of the Athena code whose numerical magnetic diffusivity is shown to be of third order in space. In the bar regions, magnetic fields are compressed and abruptly bent around the dust-lane shocks. The associated magnetic stress not only reduces the peak density of the dust-lane shocks but also removes angular momentum further from the gas that is moving radially in. Nuclear rings that form at the location of centrifugal barrier rather than resonance with the bar are smaller and more radially distributed, and the mass flow rate to the galaxy center is correspondingly larger in models with stronger magnetic fields. Outside the bar regions, the bar potential and strong shear conspire to amplify the field strength near the corotation resonance. The amplified fields transport angular momentum outward, producing trailing magnetic arms with strong fields and low density. The base of the magnetic arms are found to be unstable to a tearing-mode instability of magnetic reconnection. This produces numerous magnetic islands that eventually make the outer regions highly chaotic.

  10. Insights into the content and spatial distribution of dust from the integrated spectral properties of galaxies

    NASA Astrophysics Data System (ADS)

    Chevallard, J.; Charlot, S.; Wandelt, B.; Wild, V.

    2013-07-01

    We present a new approach to investigate the content and spatial distribution of dust in structurally unresolved star-forming galaxies from the observed dependence of integrated spectral properties on galaxy inclination. Motivated by the observation that different stellar populations reside in different spatial components of nearby star-forming galaxies, we develop an innovative combination of generic models of radiative transfer in dusty media with a prescription for the spectral evolution of galaxies, via the association of different geometric components of galaxies with stars in different age ranges. We start by showing that a wide range of radiative transfer models all predict a quasi-universal relation between slope of the attenuation curve at any wavelength, from the ultraviolet to the near-infrared, and V-band attenuation optical depth in the diffuse interstellar medium (ISM), at all galaxy inclinations. This relation predicts steeper (shallower) dust attenuation curves than both the Calzetti and Milky Way curves at small (large) attenuation optical depths, which implies that geometry and orientation effects have a stronger influence on the shape of the attenuation curve than changes in the optical properties of dust grains. We use our new, combined radiative transfer and spectral evolution model to interpret the observed dependence of the Hα/Hβ ratio and ugrizYJH attenuation curve on inclination in a sample of about 23 000 nearby star-forming galaxies, which we correct for systematic biases by developing a general method based on importance sampling. From the exploration of the model parameter space by means of a Bayesian Markov chain Monte Carlo technique, we measure the central face-on B-band optical depth of this sample to be τB⊥ ≈ 1.8 ± 0.2 (corresponding to an angle-averaged {< hat{τ}^ISM_V> _θ }≈ 0.3). We also quantify the enhanced optical depth towards newly formed stars in their birth clouds, finding this to be significantly larger in

  11. HOT DUST OBSCURED GALAXIES WITH EXCESS BLUE LIGHT: DUAL AGN OR SINGLE AGN UNDER EXTREME CONDITIONS?

    SciTech Connect

    Assef, R. J.; Diaz-Santos, T.; Walton, D. J.; Brightman, M.; Stern, D.; Eisenhardt, P. R. M.; Tsai, C.-W.; Alexander, D.; Bauer, F.; Blain, A. W.; Finkelstein, S. L.; Hickox, R. C.; Wu, J. W.

    2016-03-10

    Hot dust-obscured galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the Wide-field Infrared Survey Explorer (WISE) mission from their very red mid-IR colors, and characterized by hot dust temperatures (T > 60 K). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured active galactic nucleus (AGN) that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of eight Hot DOGs that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (i) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (ii) a second unobscured AGN in the system; or (iii) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot DOG WISE J020446.13–050640.8, which was serendipitously observed by Chandra/ACIS-I for 174.5 ks. The X-ray spectrum is consistent with a single, hyper-luminous, highly absorbed AGN, and is strongly inconsistent with the presence of a secondary unobscured AGN. Based on this, we argue that the excess blue emission in this object is most likely either due to reflection or a co-eval starburst. We favor the reflection scenario as the unobscured star formation rate needed to power the UV/optical emission would be ≳1000 M{sub ⊙} yr{sup −1}. Deep polarimetry observations could confirm the reflection hypothesis.

  12. Hot Dust Obscured Galaxies with Excess Blue Light: Dual AGN or Single AGN Under Extreme Conditions?

    NASA Astrophysics Data System (ADS)

    Assef, R. J.; Walton, D. J.; Brightman, M.; Stern, D.; Alexander, D.; Bauer, F.; Blain, A. W.; Diaz-Santos, T.; Eisenhardt, P. R. M.; Finkelstein, S. L.; Hickox, R. C.; Tsai, C.-W.; Wu, J. W.

    2016-03-01

    Hot dust-obscured galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the Wide-field Infrared Survey Explorer (WISE) mission from their very red mid-IR colors, and characterized by hot dust temperatures (T > 60 K). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured active galactic nucleus (AGN) that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of eight Hot DOGs that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (i) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (ii) a second unobscured AGN in the system; or (iii) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot DOG WISE J020446.13-050640.8, which was serendipitously observed by Chandra/ACIS-I for 174.5 ks. The X-ray spectrum is consistent with a single, hyper-luminous, highly absorbed AGN, and is strongly inconsistent with the presence of a secondary unobscured AGN. Based on this, we argue that the excess blue emission in this object is most likely either due to reflection or a co-eval starburst. We favor the reflection scenario as the unobscured star formation rate needed to power the UV/optical emission would be ≳1000 M⊙ yr-1. Deep polarimetry observations could confirm the reflection hypothesis.

  13. Direct measurements of dust attenuation in z ∼ 1.5 star-forming galaxies from 3D-HST: Implications for dust geometry and star formation rates

    SciTech Connect

    Price, Sedona H.; Kriek, Mariska; Brammer, Gabriel B.; Conroy, Charlie; Schreiber, Natascha M. Förster; Wuyts, Stijn; Franx, Marijn; Fumagalli, Mattia; Lundgren, Britt; Momcheva, Ivelina; Nelson, Erica J.; Van Dokkum, Pieter G.; Skelton, Rosalind E.; Whitaker, Katherine E.

    2014-06-10

    The nature of dust in distant galaxies is not well understood, and until recently few direct dust measurements have been possible. We investigate dust in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between dust around star-forming regions (A {sub V,} {sub H} {sub II}) and the integrated dust content (A {sub V,} {sub star}). We select a sample of 163 galaxies between 1.36 ≤ z ≤ 1.5 with Hα signal-to-noise ratio ≥5 and measure Balmer decrements from stacked spectra to calculate A {sub V,} {sub H} {sub II}. First, we stack spectra in bins of A {sub V,} {sub star}, and find that A {sub V,} {sub H} {sub II} = 1.86 A {sub V,} {sub star}, with a significance of σ = 1.7. Our result is consistent with the two-component dust model, in which galaxies contain both diffuse and stellar birth cloud dust. Next, we stack spectra in bins of specific star formation rate (log SSFR), star formation rate (log SFR), and stellar mass (log M {sub *}). We find that on average A {sub V,} {sub H} {sub II} increases with SFR and mass, but decreases with increasing SSFR. Interestingly, the data hint that the amount of extra attenuation decreases with increasing SSFR. This trend is expected from the two-component model, as the extra attenuation will increase once older stars outside the star-forming regions become more dominant in the galaxy spectrum. Finally, using Balmer decrements we derive dust-corrected Hα SFRs, and find that stellar population modeling produces incorrect SFRs if rapidly declining star formation histories are included in the explored parameter space.

  14. Dust-to-gas Ratio in the Extremely Metal-poor Galaxy I Zw 18

    NASA Astrophysics Data System (ADS)

    Herrera-Camus, Rodrigo; Fisher, David B.; Bolatto, Alberto D.; Leroy, Adam K.; Walter, Fabian; Gordon, Karl. D.; Roman-Duval, Julia; Donaldson, Jessica; Meléndez, Marcio; Cannon, John M.

    2012-06-01

    The blue compact dwarf galaxy I Zw 18 is one of the most metal-poor systems known in the local universe (12+log(O/H) = 7.17). In this work we study I Zw 18 using data from Spitzer, Herschel Space Telescope, and IRAM Plateau de Bure Interferometer. Our data set includes the most sensitive maps of I Zw 18, to date, in both the far-infrared and the CO J = 1 → 0 transition. We use dust emission models to derive a dust mass upper limit of only M dust <= 1.1 × 104 M ⊙ (3σ limit). This upper limit is driven by the non-detection at 160 μm, and it is a factor of 4-10 times smaller than previous estimates (depending on the model used). We also estimate an upper limit to the total dust-to-gas mass ratio of M Dust/M gas <= 5.0 × 10-5. If a linear correlation between the dust-to-gas mass ratio and metallicity (measured as O/H) were to hold, we would expect a ratio of 3.9 × 10-4. We also show that the infrared spectral energy distribution is similar to that of starbursting systems.

  15. Small-Angle Scattering of X-Rays from Extragalactic Sources by Dust in Intervening Galaxies

    NASA Astrophysics Data System (ADS)

    Miralda-Escudé, Jordi

    1999-02-01

    Gamma-ray bursts are now known to be a cosmological population of objects, which are often accompanied by X-ray and optical afterglows. The total energy emitted in the afterglow can be similar to the energy radiated in the gamma-ray burst itself. If a galaxy containing a large column density of dust is near the line of sight to a gamma-ray burst, small-angle scattering of the X-rays due to diffraction by the dust grains will give rise to an X-ray echo of the afterglow. A measurement of the angular size of the echo at a certain time after the afterglow is observed yields a combination of the angular diameter distances to the scattering galaxy and the gamma-ray burst that can be used to constrain cosmological models in the same way as a time delay in a gravitational lens. The scattering galaxy will generally cause gravitational lensing as well, and this should modify the shape of the X-ray echo from a circular ring. The main difficulty in detecting this phenomenon is the very low flux expected for the echo. The flux can be increased when the gamma-ray burst is highly magnified by gravitational lensing, or when the deflecting galaxy is at low redshift. X-ray echoes of continuous (but variable) sources, such as quasars, may also be detectable with high-resolution instruments and would allow similar measurements.

  16. Analysis of the spatial distribution of stars, gas and dust in nearby galaxies

    NASA Astrophysics Data System (ADS)

    Muñoz-Mateos, J. C.

    2013-05-01

    I summarize the main result of my thesis, which was awarded the Spanish Astronomical Society Award for the best thesis in Astronomy defended in 2010. This thesis was supervised by Armando Gil de Paz and Jaime Zamorano at Universidad Complutense de Madrid. In this work we quantified how the physical properties of stars, gas and dust vary with radius in nearby galactic disks, and used that information to infer the past assembly and evolution of galaxies. To do so we made use of spatially-resolved multi-wavelength images of nearby galaxies, all the way from the far-UV to the far-IR and radio. By comparing extinction- corrected profiles in the UV, optical and IR with models of disk evolution, we concluded that the current stellar population gradients are consistent with an inside-out growth of disks of ˜ 25% since z ˜ 1. We also found that the dust-to-gas ratio decreases with radius, and is tightly correlated with the local gas metallicity, which is again consistent with an inside-out assembly of disks. We measured the fraction of the dust mass which is in the form of PAHs at different radii. The resulting trend agrees with certain models of dust evolution, in which the abundance of PAHs is primarily determined by a delayed injection of carbon into the ISM by AGB stars.

  17. A map of the temperature of interstellar dust in the Milky Way Galaxy

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A map of the temperature of interstellar dust in the Milky Way Galaxy derived from FIRAS sub-millimeter data. The map is a projection of the full sky in Galactic coordinates. The plane of the Milky Way is horizontal in the middle of the map with the Galactic center at the center. At high frequencies, the continuum in a FIRAS spectrum is dominated by thermal dust emission; at low frequencies, the cosmic microwave background dominates. A single-temperature dust model (with 1.55 adopted as the emissivity spectral index) was used to make this map. Different models can be used and assumptions made, and corresponding temperature and optical depth maps can be derived straightforwardly from the FIRAS Continuum Spectrum Maps (see 'About the Data Products' in the FIRAS section of the COBE Home Page). Reach et al. ( 1995, ApJ, 451, 188, 'Far-Infrared Spectral Observations of the Galaxy by COBE'), for example, report evidence for a ubiquitous cold (5 K) dust component.

  18. CARBON-RICH DUST PRODUCTION IN METAL-POOR GALAXIES IN THE LOCAL GROUP

    SciTech Connect

    Sloan, G. C.; Matsuura, M.; Lagadec, E.; Van Loon, J. Th.; Kraemer, K. E.; McDonald, I.; Zijlstra, A. A.; Groenewegen, M. A. T.; Wood, P. R.; Bernard-Salas, J.

    2012-06-20

    We have observed a sample of 19 carbon stars in the Sculptor, Carina, Fornax, and Leo I dwarf spheroidal galaxies with the Infrared Spectrograph on the Spitzer Space Telescope. The spectra show significant quantities of dust around the carbon stars in Sculptor, Fornax, and Leo I, but little in Carina. Previous comparisons of carbon stars with similar pulsation properties in the Galaxy and the Magellanic Clouds revealed no evidence that metallicity affected the production of dust by carbon stars. However, the more metal-poor stars in the current sample appear to be generating less dust. These data extend two known trends to lower metallicities. In more metal-poor samples, the SiC dust emission weakens, while the acetylene absorption strengthens. The bolometric magnitudes and infrared spectral properties of the carbon stars in Fornax are consistent with metallicities more similar to carbon stars in the Magellanic Clouds than in the other dwarf spheroidals in our sample. A study of the carbon budget in these stars reinforces previous considerations that the dredge-up of sufficient quantities of carbon from the stellar cores may trigger the final superwind phase, ending a star's lifetime on the asymptotic giant branch.

  19. Spitzer Observations of Transient, Extended Dust in Two Elliptical Galaxies: New Evidence of Recent Feedback Energy Release in Galactic Cores

    NASA Astrophysics Data System (ADS)

    Temi, Pasquale; Brighenti, Fabrizio; Mathews, William G.

    2007-09-01

    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 μm out to about 5 kpc. Both NGC 5044 and NGC 4636 have extended 70 μm emission from cold dust exceeding that expected from stellar mass loss. The sputtering lifetime of this extended dust in the ~1 keV interstellar gas, ~107 yr, establishes the time when the dust first entered the hot gas. Evidently the extended dust originated in dusty disks or clouds, commonly observed in elliptical galaxy cores, that were disrupted, heated, and buoyantly transported outward. The surviving central dust in NGC 5044 and NGC 4636 has been disrupted into many small filaments. It is remarkable that the asymmetrically extended 8 μm emission in NGC 5044 is spatially coincident with Hα+[N II] emission from warm gas. A calculation shows that dust-assisted cooling in buoyant hot gas moving out from the galactic core can cool within a few kiloparsecs in ~107 yr, explaining the optical line emission observed. The X-ray images of both galaxies are disturbed. All timescales for transient activity-restoration of equilibrium and buoyant transport in the hot gas, dynamics of surviving dust fragments, and dust sputtering-are consistent with a central release of feedback energy in both galaxies about 107 years ago.

  20. Inclination-dependent Luminosity Function of Spiral Galaxies in the Sloan Digital Sky Survey: Implications for Dust Extinction

    NASA Astrophysics Data System (ADS)

    Shao, Zhengyi; Xiao, Quanbao; Shen, Shiyin; Mo, H. J.; Xia, Xiaoyang; Deng, Zugan

    2007-04-01

    Using a sample of 61,506 spiral galaxies selected from the SDSS DR2, we examine the luminosity function (LF) of spiral galaxies with different inclination angles. We find that the characteristic luminosity of the LF, L*, decreases with increasing inclination, while the faint-end slope, α, depends only weakly on it. The inclination dependence of the LF is consistent with that expected from a simple model in which the optical depth is proportional to the cosine of the inclination angle, and we use a likelihood method to recover both the coefficient in front of the cosine, γ, and the LF for galaxies viewed face-on. The value of γ is quite independent of galaxy luminosity in a given band, and the values of γ obtained in this way for the five SDSS bands give an extinction curve that is a power law of wavelength (τ~λ-n), with a power index of n=0.96+/-0.04. Using the dust extinction for galaxies obtained by Kauffmann and coworkers, we derive an ``extinction-corrected'' luminosity function for spiral galaxies. Dust extinction makes M* dimmer by ~0.5 mag in the z band and by ~1.2 mag in the u band. Since our analysis is based on a sample in which selection effects are well under control, the dimming of edge-on galaxies relative to face-on galaxies is best explained by assuming that galaxy disks are optically thick in dust absorption.

  1. Untangling the nature of spatial variations of cold dust properties in star forming galaxies

    SciTech Connect

    Kirkpatrick, Allison; Calzetti, Daniela; Kennicutt, Robert; Galametz, Maud; Gordon, Karl; Groves, Brent; Tabatabaei, Fatemeh; Hunt, Leslie; Dale, Daniel; Hinz, Joannah

    2014-07-10

    We investigate the far-infrared (IR) dust emission for 20 local star forming galaxies from the Key Insights on Nearby Galaxies: A Far-IR Survey with Herschel (KINGFISH) sample. We model the far-IR/submillimeter spectral energy distribution (SED) using images from Spitzer Space Telescope and Herschel Space Observatory. We calculate the cold dust temperature (T{sub c} ) and emissivity (β) on a pixel by pixel basis (where each pixel ranges from 0.1 to 3 kpc{sup 2}) using a two-temperature modified blackbody fitting routine. Our fitting method allows us to investigate the resolved nature of temperature and emissivity variations by modeling from the galaxy centers to the outskirts (physical scales of ∼15-50 kpc, depending on the size of the galaxy). We fit each SED in two ways: (1) fit T{sub c} and β simultaneously, (2) hold β constant and fit T{sub c} . We compare T{sub c} and β with star formation rates (calculated from L{sub Hα} and L{sub 24μm}), the luminosity of the old stellar population (traced through L{sub 3.6μm}), and the dust mass surface density (traced by 500 μm luminosity, L{sub 500}). We find a significant trend between SFR/L{sub 500} and T{sub c} , implying that the flux of hard UV photons relative to the amount of dust is significantly contributing to the heating of the cold, or diffuse, dust component. We also see a trend between L{sub 3.6}/L{sub 500} and β, indicating that the old stellar population contributes to the heating at far-IR/submillimeter wavelengths. Finally, we find that when β is held constant, T{sub c} exhibits a strongly decreasing radial trend, illustrating that the shape of the far-IR SED is changing radially through a galaxy, thus confirming on a sample almost double in size the trends observed in Galametz et al.

  2. Galaxy Centaurus A

    NASA Image and Video Library

    2003-07-25

    This image of the active galaxy Centaurus A was taken by NASA's Galaxy Evolution Explorer on June 7, 2003. The galaxy is located 30 million light-years from Earth and is seen edge on, with a prominent dust lane across the major axis. In this image the near ultraviolet emission is represented as green, and the far ultraviolet emission as blue. The galaxy exhibits jets of high energy particles, which were traced by the X-ray emission and measured by NASA's Chandra X-ray Observatory. These X-ray emissions are seen as red in the image. Several regions of ultraviolet emission can be seen where the jets of high energy particles intersect with hydrogen clouds in the upper left corner of the image. The emission shown may be the result of recent star formation triggered by the compression of gas by the jet. http://photojournal.jpl.nasa.gov/catalog/PIA04624

  3. PACS photometry of the Herschel Reference Survey - far-infrared/submillimetre colours as tracers of dust properties in nearby galaxies

    NASA Astrophysics Data System (ADS)

    Cortese, L.; Fritz, J.; Bianchi, S.; Boselli, A.; Ciesla, L.; Bendo, G. J.; Boquien, M.; Roussel, H.; Baes, M.; Buat, V.; Clemens, M.; Cooray, A.; Cormier, D.; Davies, J. I.; De Looze, I.; Eales, S. A.; Fuller, C.; Hunt, L. K.; Madden, S.; Munoz-Mateos, J.; Pappalardo, C.; Pierini, D.; Rémy-Ruyer, A.; Sauvage, M.; di Serego Alighieri, S.; Smith, M. W. L.; Spinoglio, L.; Vaccari, M.; Vlahakis, C.

    2014-05-01

    We present Herschel/PACS 100 and 160 μm integrated photometry for the 323 galaxies in the Herschel Reference Survey (HRS), a K-band, volume-limited sample of galaxies in the local Universe. Once combined with the Herschel/SPIRE observations already available, these data make the HRS the largest representative sample of nearby galaxies with homogeneous coverage across the 100-500 μm wavelength range. In this paper, we take advantage of this unique data set to investigate the properties and shape of the far-infrared/submillimetre spectral energy distribution in nearby galaxies. We show that, in the stellar mass range covered by the HRS (8 ≲ log (M*/M⊙) ≲ 12), the far-infrared/submillimetre colours are inconsistent with a single modified blackbody having the same dust emissivity index β for all galaxies. In particular, either β decreases or multiple temperature components are needed, when moving from metal-rich/gas-poor to metal-poor/gas-rich galaxies. We thus investigate how the dust temperature and mass obtained from a single modified blackbody depend on the assumptions made on β. We show that, while the correlations between dust temperature, galaxy structure and star formation rate are strongly model dependent, the dust mass scaling relations are much more reliable, and variations of β only change the strength of the observed trends.

  4. A Multi-Wavelength Census of Dust and Star Formation in Galaxies at z ~ 2

    NASA Astrophysics Data System (ADS)

    Shivaei, Irene; Reddy, Naveen; MOSDEF Collaboration

    2017-01-01

    Redshift of z ~ 2 is an important era in the history of the universe, as it contains the peak of star formation rate density and quasar activity. We study the galaxy properties during this era from two different, yet complementary, aspects: by studying formation of stars and mass assembly, and exploring the properties of galactic dust. We use a wealth of multi-wavelength data, from UV to far-IR, to obtain a complete census of obscured and unobscured star formation in galaxies. Our data consists of rest-frame optical spectra from the MOSDEF survey, rest-frame UV and optical photometric data from the 3D-HST survey, and mid- and far-IR data obtained by the Spitzer and Herschel telescopes. In the MOSDEF survey, we acquired rest-frame optical spectra of ~ 1500 galaxies with the MOSFIRE spectrograph on the Keck I telescope. MOSDEF is currently the largest survey of the rest-frame optical properties of galaxies at 1.37 ≤ z ≤ 3.80. Using the multi-wavelength data sets, we show that Hα SFRs, corrected for dust attenuation using the Hβ line, accurately trace SFRs up to ~ 300 M⊙ yr-1, when compared with panchromatic (UV-to-far-IR) SED models. Using Hα SFRs for a large sample of ~ 200 galaxies at z ~ 2, we explore the SFR-M* relation and show that the slope of this relation is shallower than previously measured. We conclude that the scatter in the SFR-M* relation is dominated by uncertainties in dust correction and cannot be used to measure the star formation stochasticity. Furthermore, we investigate the robustness of Spitzer/MIPS 24 micron flux as an SFR indicator and its variation with ISM physical parameters. We find that 24 micron flux, which at z ~ 2 traces the emission from the PAH grains, significantly depends on metallicity, such that there is a PAH deficiency in metal-poor galaxies. We demonstrate that commonly-used conversions of 24 micron flux to IR luminosity underestimate the IR luminosity of low-mass galaxies by more than a factor of 2. Our results

  5. Spatial distribution of far-infrared emission in spiral galaxies. II. Heating sources and gas-to-dust ratio.

    NASA Astrophysics Data System (ADS)

    Mayya, Y. D.; Rengarajan, T. N.

    1997-09-01

    We study the radial distribution of the temperature of the warm dust and gas-to-dust mass ratios in a sample of 22 spiral galaxies. The heating capabilities of the diffuse interstellar radiation field (ISRF), based on Desert et al. model, are investigated in 13 of the sample galaxies. In general, the temperature of the warm dust decreases away from the center, reaches a minimum value at the mid-disk and increases again in the outer parts of galaxies. Heating a mixture of small and big grains by the ISRF is able to explain the observed behavior qualitatively. However, ultraviolet photons from recent star formation events are necessary for a detailed matching of the warm dust temperature profiles. Very small grains contribute typically more than 50% to the observed flux at 60 microns beyond half the disk radius in galaxies. Optical depth ( tausixty) profiles, derived from the observed 60 microns and warm dust temperature profiles, peak at or close to the galactic center. In 13 of the galaxies, where dust temperature profiles are modeled, we obtain optical depth and dust mass profiles after correction for the contaminating effects of very small grains. These profiles are combined with the gas density profiles in the literature, to generate profiles of the gas-to-dust mass ratio. The resulting gas-to-dust mass ratio decreases by a factor of 8 from the center to the optical isophotal radius, where the value approaches the local galactic value. With the understanding that the dust mass is proportional to metallicity, and that the metallicity increases towards the center of galaxies, one expects the gas-to-dust ratio to decrease towards the center, contrary to what is observed. We demonstrate that the observed steep gradient is a result of the over-estimation of the molecular mass, and can be flattened out to within a factor of 2, if the molecular hydrogen mass is recomputed assuming a metallicity dependent conversion factor from CO intensity to {h two} column density

  6. AN INFRARED CENSUS OF DUST IN NEARBY GALAXIES WITH SPITZER (DUSTiNGS). II. DISCOVERY OF METAL-POOR DUSTY AGB STARS

    SciTech Connect

    Boyer, Martha L.; Sonneborn, George; McQuinn, Kristen B. W.; Gehrz, Robert D.; Skillman, Evan; Barmby, Pauline; Bonanos, Alceste Z.; Gordon, Karl D.; Meixner, Margaret; Groenewegen, M. A. T.; Lagadec, Eric; Lennon, Daniel; Marengo, Massimo; McDonald, Iain; Zijlstra, Albert; Sloan, G. C.; Van Loon, Jacco Th.

    2015-02-10

    The DUSTiNGS survey (DUST in Nearby Galaxies with Spitzer) is a 3.6 and 4.5 μm imaging survey of 50 nearby dwarf galaxies designed to identify dust-producing asymptotic giant branch (AGB) stars and massive stars. Using two epochs, spaced approximately six months apart, we identify a total of 526 dusty variable AGB stars (sometimes called ''extreme'' or x-AGB stars; [3.6]-[4.5] > 0.1 mag). Of these, 111 are in galaxies with [Fe/H] < –1.5 and 12 are in galaxies with [Fe/H] < –2.0, making them the most metal-poor dust-producing AGB stars known. We compare these identifications to those in the literature and find that most are newly discovered large-amplitude variables, with the exception of ≈30 stars in NGC 185 and NGC 147, 1 star in IC 1613, and 1 star in Phoenix. The chemical abundances of the x-AGB variables are unknown, but the low metallicities suggest that they are more likely to be carbon-rich than oxygen-rich and comparisons with existing optical and near-IR photometry confirm that 70 of the x-AGB variables are confirmed or likely carbon stars. We see an increase in the pulsation amplitude with increased dust production, supporting previous studies suggesting that dust production and pulsation are linked. We find no strong evidence linking dust production with metallicity, indicating that dust can form in very metal-poor environments.

  7. Revealing the cold dust in low-metallicity environments. I. Photometry analysis of the Dwarf Galaxy Survey with Herschel

    NASA Astrophysics Data System (ADS)

    Rémy-Ruyer, A.; Madden, S. C.; Galliano, F.; Hony, S.; Sauvage, M.; Bendo, G. J.; Roussel, H.; Pohlen, M.; Smith, M. W. L.; Galametz, M.; Cormier, D.; Lebouteiller, V.; Wu, R.; Baes, M.; Barlow, M. J.; Boquien, M.; Boselli, A.; Ciesla, L.; De Looze, I.; Karczewski, O. Ł.; Panuzzo, P.; Spinoglio, L.; Vaccari, M.; Wilson, C. D.

    2013-09-01

    Context. We present new photometric data from our Herschel guaranteed time key programme, the Dwarf Galaxy Survey (DGS), dedicated to the observation of the gas and dust in low-metallicity environments. A total of 48 dwarf galaxies were observed with the PACS and SPIRE instruments onboard the Herschel Space Observatory at 70, 100, 160, 250, 350, and 500 μm. Aims: The goal of this paper is to provide reliable far-infrared (FIR) photometry for the DGS sample and to analyse the FIR/submillimetre (submm) behaviour of the DGS galaxies. We focus on a systematic comparison of the derived FIR properties (FIR luminosity, LFIR, dust mass, Mdust, dust temperature, T, emissivity index, β) with more metal-rich galaxies and investigate the detection of a potential submm excess. Methods: The data reduction method is adapted for each galaxy in order to derive the most reliable photometry from the final maps. The derived PACS flux densities are compared with the Spitzer MIPS 70 and 160 μm bands. We use colour-colour diagrams to analyse the FIR/submm behaviour of the DGS galaxies and modified blackbody fitting procedures to determine their dust properties. To study the variation in these dust properties with metallicity, we also include galaxies from the Herschel KINGFISH sample, which contains more metal-rich environments, totalling 109 galaxies. Results: The location of the DGS galaxies on Herschel colour-colour diagrams highlights the differences in dust grain properties and/or global environments of low-metallicity dwarf galaxies. The dust in DGS galaxies is generally warmer than in KINGFISH galaxies (TDGS ~ 32 K and TKINGFISH ~ 23 K). The emissivity index, β, is ~1.7 in the DGS, however metallicity does not make a strong effect on β. The proportion of dust mass relative to stellar mass is lower in low-metallicity galaxies: Mdust/Mstar ~ 0.02% for the DGS versus 0.1% for KINGFISH. However, per unit dust mass, dwarf galaxies emit about six times more in the FIR/submm than

  8. Kiloparsec-scale Dust Disks in High-redshift Luminous Submillimeter Galaxies

    NASA Astrophysics Data System (ADS)

    Hodge, J. A.; Swinbank, A. M.; Simpson, J. M.; Smail, I.; Walter, F.; Alexander, D. M.; Bertoldi, F.; Biggs, A. D.; Brandt, W. N.; Chapman, S. C.; Chen, C. C.; Coppin, K. E. K.; Cox, P.; Dannerbauer, H.; Edge, A. C.; Greve, T. R.; Ivison, R. J.; Karim, A.; Knudsen, K. K.; Menten, K. M.; Rix, H.-W.; Schinnerer, E.; Wardlow, J. L.; Weiss, A.; van der Werf, P.

    2016-12-01

    We present high-resolution (0.″16) 870 μm Atacama Large Millimeter/submillimeter Array (ALMA) imaging of 16 luminous ({L}{IR}˜ 4× {10}12 {L}⊙ ) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South. This dust imaging traces the dust-obscured star formation in these z˜ 2.5 galaxies on ˜1.3 kpc scales. The emission has a median effective radius of R e = 0.″24 ± 0.″02, corresponding to a typical physical size of {R}e= 1.8 ± 0.2 kpc. We derive a median Sérsic index of n = 0.9 ± 0.2, implying that the dust emission is remarkably disk-like at the current resolution and sensitivity. We use different weighting schemes with the visibilities to search for clumps on 0.″12 (˜1.0 kpc) scales, but we find no significant evidence for clumping in the majority of cases. Indeed, we demonstrate using simulations that the observed morphologies are generally consistent with smooth exponential disks, suggesting that caution should be exercised when identifying candidate clumps in even moderate signal-to-noise ratio interferometric data. We compare our maps to comparable-resolution Hubble Space Telescope {H}160-band images, finding that the stellar morphologies appear significantly more extended and disturbed, and suggesting that major mergers may be responsible for driving the formation of the compact dust disks we observe. The stark contrast between the obscured and unobscured morphologies may also have implications for SED fitting routines that assume the dust is co-located with the optical/near-IR continuum emission. Finally, we discuss the potential of the current bursts of star formation to transform the observed galaxy sizes and light profiles, showing that the z˜ 0 descendants of these SMGs are expected to have stellar masses, effective radii, and gas surface densities consistent with the most compact massive ({M}* ˜ 1-2 × 1011 {M}⊙ ) early-type galaxies observed locally.

  9. Seeing Galaxies through Thick and Thin. III. Hubble Space Telescope Imaging of the Dust in Backlit Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Keel, William C.; White, Raymond E., III

    2001-03-01

    We present analysis of Wide Field Planetary Camera 2 imaging of two spiral galaxies partially backlit by elliptical or S0 systems in the pairs AM 1316-241 and AM 0500-620, as well as the (probably spiral) foreground system in NGC 1275. Images in B and I are used to determine the reddening curve of dust in these systems. The foreground spiral component of AM 1316-241 shows dust strongly concentrated in discrete arms, with a reddening law very close to the Milky Way mean [R=AV/E(B-V)=3.4+/-0.2]. The dust distribution is scale-free between about 100 pc and the arm dimension, about 8 kpc. The foreground spiral in AM 0500-620 shows dust concentrated in arms and interarm spurs, with measurable interarm extinction as well. In this case, although the dust properties are less well-determined than in AM 1316-241, we find evidence for a steeper extinction law than the Milky Way mean (formally, R~2.5+/-0.4, with substantial variation depending on data quality in each region). The shape of the reddening law suggests that at least in AM 1316-241 we have resolved most of the dust structure. In AM 0500-620 it is less clear that we have resolved most of the dust structure, since the errors are larger. In AM 0500-620, the slope of the perimeter-scale relation (associated with fractal analysis) steepens systematically when going from regions of low to high extinction. A perimeter-smoothing length test for scale-free (fractal) behavior in AM 1316-241 shows a logarithmic slope typically -0.4 on 100-1000 pc scales. However, we cannot determine a unique fractal dimension from the defining area-perimeter relation, so the projected dust distribution is best defined as fractal-like. For scales above 2-4 pixels (120-250 pc), the box-counting estimate yields a fractal dimension close to 1.4, but the perimeter-area relation yields a dimension of 0.7 on large scales and inconsistent results for small scales, so that the distribution shows only some aspects of a fractal nature. In neither galaxy

  10. Polarization in Monte Carlo radiative transfer and dust scattering polarization signatures of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Peest, C.; Camps, P.; Stalevski, M.; Baes, M.; Siebenmorgen, R.

    2017-05-01

    Polarization is an important tool to further the understanding of interstellar dust and the sources behind it. In this paper we describe our implementation of polarization that is due to scattering of light by spherical grains and electrons in the dust Monte Carlo radiative transfer code SKIRT. In contrast to the implementations of other Monte Carlo radiative transfer codes, ours uses co-moving reference frames that rely solely on the scattering processes. It fully supports the peel-off mechanism that is crucial for the efficient calculation of images in 3D Monte Carlo codes. We develop reproducible test cases that push the limits of our code. The results of our program are validated by comparison with analytically calculated solutions. Additionally, we compare results of our code to previously published results. We apply our method to models of dusty spiral galaxies at near-infrared and optical wavelengths. We calculate polarization degree maps and show them to contain signatures that trace characteristics of the dust arms independent of the inclination or rotation of the galaxy.

  11. GAMA/H-ATLAS: The Dust Opacity-Stellar Mass Surface Density Relation for Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Grootes, M. W.; Tuffs, R. J.; Popescu, C. C.; Pastrav, B.; Andrae, E.; Gunawardhana, M.; Kelvin, L. S.; Liske, J.; Seibert, M.; Taylor, E. N.; Graham, Alister W.; Baes, M.; Baldry, I. K.; Bourne, N.; Brough, S.; Cooray, A.; Dariush, A.; De Zotti, G.; Driver, S. P.; Dunne, L.; Gomez, H.; Hopkins, A. M.; Hopwood, R.; Jarvis, M.; Loveday, J.; Maddox, S.; Madore, B. F.; Michałowski, M. J.; Norberg, P.; Parkinson, H. R.; Prescott, M.; Robotham, A. S. G.; Smith, D. J. B.; Thomas, D.; Valiante, E.

    2013-03-01

    We report the discovery of a well-defined correlation between B-band face-on central optical depth due to dust, τ ^f_B, and the stellar mass surface density, μ*, of nearby (z <= 0.13) spiral galaxies: {log}(τ ^{f}_{B}) = 1.12(+/- 0.11) \\cdot {log}({μ _{*}}/{{M}_{⊙ } {kpc}^{-2}}) - 8.6(+/- 0.8). This relation was derived from a sample of spiral galaxies taken from the Galaxy and Mass Assembly (GAMA) survey, which were detected in the FIR/submillimeter (submm) in the Herschel-ATLAS science demonstration phase field. Using a quantitative analysis of the NUV attenuation-inclination relation for complete samples of GAMA spirals categorized according to stellar mass surface density, we demonstrate that this correlation can be used to statistically correct for dust attenuation purely on the basis of optical photometry and Sérsic-profile morphological fits. Considered together with previously established empirical relationships of stellar mass to metallicity and gas mass, the near linearity and high constant of proportionality of the τ ^f_B - μ_{*} relation disfavors a stellar origin for the bulk of refractory grains in spiral galaxies, instead being consistent with the existence of a ubiquitous and very rapid mechanism for the growth of dust in the interstellar medium. We use the τ ^f_B - μ_{*} relation in conjunction with the radiation transfer model for spiral galaxies of Popescu & Tuffs to derive intrinsic scaling relations between specific star formation rate (SFR), stellar mass, and stellar surface density, in which attenuation of the UV light used for the measurement of SFR is corrected on an object-to-object basis. A marked reduction in scatter in these relations is achieved which we demonstrate is due to correction of both the inclination-dependent and face-on components of attenuation. Our results are consistent with a general picture of spiral galaxies in which most of the submm emission originates from grains residing in translucent structures

  12. GAMA/H-ATLAS: THE DUST OPACITY-STELLAR MASS SURFACE DENSITY RELATION FOR SPIRAL GALAXIES

    SciTech Connect

    Grootes, M. W.; Tuffs, R. J.; Andrae, E.; Popescu, C. C.; Pastrav, B.; Gunawardhana, M.; Taylor, E. N.; Kelvin, L. S.; Driver, S. P.; Liske, J.; Seibert, M.; Graham, Alister W.; Baes, M.; Baldry, I. K.; Bourne, N.; Brough, S.; Cooray, A.; Dariush, A.; De Zotti, G.; Dunne, L.; and others

    2013-03-20

    We report the discovery of a well-defined correlation between B-band face-on central optical depth due to dust, {tau}{sup f}{sub B}, and the stellar mass surface density, {mu}{sub *}, of nearby (z {<=} 0.13) spiral galaxies. This relation was derived from a sample of spiral galaxies taken from the Galaxy and Mass Assembly (GAMA) survey, which were detected in the FIR/submillimeter (submm) in the Herschel-ATLAS science demonstration phase field. Using a quantitative analysis of the NUV attenuation-inclination relation for complete samples of GAMA spirals categorized according to stellar mass surface density, we demonstrate that this correlation can be used to statistically correct for dust attenuation purely on the basis of optical photometry and Sersic-profile morphological fits. Considered together with previously established empirical relationships of stellar mass to metallicity and gas mass, the near linearity and high constant of proportionality of the {tau}{sub B}{sup f} - {mu}{sub *} relation disfavors a stellar origin for the bulk of refractory grains in spiral galaxies, instead being consistent with the existence of a ubiquitous and very rapid mechanism for the growth of dust in the interstellar medium. We use the {tau}{sub B}{sup f} - {mu}{sub *} relation in conjunction with the radiation transfer model for spiral galaxies of Popescu and Tuffs to derive intrinsic scaling relations between specific star formation rate (SFR), stellar mass, and stellar surface density, in which attenuation of the UV light used for the measurement of SFR is corrected on an object-to-object basis. A marked reduction in scatter in these relations is achieved which we demonstrate is due to correction of both the inclination-dependent and face-on components of attenuation. Our results are consistent with a general picture of spiral galaxies in which most of the submm emission originates from grains residing in translucent structures, exposed to UV in the diffuse interstellar

  13. Predicting the stellar and non-equilibrium dust emission spectra of high-resolution simulated galaxies with DART-RAY

    NASA Astrophysics Data System (ADS)

    Natale, Giovanni; Popescu, Cristina C.; Tuffs, Richard. J.; Debattista, Victor P.; Fischera, Jörg; Grootes, Meiert W.

    2015-05-01

    We describe the calculation of the stochastically heated dust emission using the 3D ray-tracing dust radiative transfer code DART-RAY, which is designed to solve the dust radiative transfer problem for galaxies with arbitrary geometries. In order to reduce the time required to derive the non-equilibrium dust emission spectra from each volume element within a model, we implemented an adaptive spectral energy distribution library approach, which we tested for the case of axisymmetric galaxy geometries. To show the capabilities of the code, we applied DART-RAY to a high-resolution N-body+SPH galaxy simulation to predict the appearance of the simulated galaxy at a set of wavelengths from the UV to the sub-mm. We analyse the results to determine the effect of dust on the observed radial and vertical profiles of the stellar emission as well as on the attenuation and scattering of light from the constituent stellar populations. We also quantify the proportion of dust re-radiated stellar light powered by young and old stellar populations, both bolometrically and as a function of infrared wavelength.

  14. The Herschel Virgo Cluster Survey. V. Star-forming dwarf galaxies - dust in metal-poor environments

    NASA Astrophysics Data System (ADS)

    Grossi, M.; Hunt, L. K.; Madden, S.; Vlahakis, C.; Bomans, D. J.; Baes, M.; Bendo, G. J.; Bianchi, S.; Boselli, A.; Clemens, M.; Corbelli, E.; Cortese, L.; Dariush, A.; Davies, J. I.; De Looze, I.; di Serego Alighieri, S.; Fadda, D.; Fritz, J.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Hughes, T. M.; Jones, A. P.; Pierini, D.; Pohlen, M.; Sabatini, S.; Smith, M. W. L.; Verstappen, J.; Xilouris, E. M.; Zibetti, S.

    2010-07-01

    We present the dust properties of a small sample of Virgo cluster dwarf galaxies drawn from the science demonstration phase data set of the Herschel Virgo Cluster Survey. These galaxies have low metallicities (7.8 < 12 + log(O/H) < 8.3) and star-formation rates ≲10-1 M⊙ yr-1. We measure the spectral energy distribution (SED) from 100 to 500 μm and derive dust temperatures and dust masses. The SEDs are fitted by a cool component of temperature T ≲ 20 K, implying dust masses around 105 M⊙ and dust-to-gas ratios D within the range 10-3-10-2. The completion of the full survey will yield a larger set of galaxies, which will provide more stringent constraints on the dust content of star-forming dwarf galaxies. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  15. On The Origins Of Cosmic Dust And The Evolution Of Nearby Galaxies With The Herschel Space Observatory

    NASA Astrophysics Data System (ADS)

    Clark, Christopher Jonathan Redfern

    2015-04-01

    Using multiwavelength observations, centred around the unique far-infrared and submillimetre window provided by the Herschel Space Observatory, this thesis investigates the origins and evolution of cosmic dust in the local Universe – by examining individual sources of dust in our own galaxy, and by studying dust in nearby galaxies. I search Herschel observations of the remnants of Kepler’s (SN1604) and Tycho’s (SN1572) supernovæ, both Type-Ia explosions, for evidence of dust creation by these events. Being the only Type-Ia supernovæ known to have occurred in our Galaxy within the past 1,000 years, these remnants are the only ones both close enough to resolve, and young enough that they are dominated by their ejecta dynamics. There is no indication of any recently manufactured dust associated with either supernova remnant. It therefore appears that Type-Ia supernovæ do not contribute significantly to the dust budgets of galaxies. The Crab Nebula, the result of a Type-II supernova (SN1054), is also investigated using Herschel and multiwavelength data. After accounting for other sources of emission, a temperature of Td = 63.1 K and mass of Md = 0.21 M⊙ is derived for the Crab Nebula’s dust component. I create a map of the distribution of dust in the Crab Nebula, the first of its kind, by means of a resolved component separation, revealing that the dust is located in the dense filamentary ejecta. We can be confident that this dust will survive in the long term, and be injected into the galactic dust budget. This is the first detection of manufactured supernova dust for which this can be said. Next I use the Herschel-ATLAS to assemble HAPLESS: the Herschel- ATLAS Phase-1 Limited Extent Spatial Sample – a blind, volume-limited, dust- selected sample of nearby galaxies. The majority of this sample is made up of curious very blue galaxies. Often irregular and/or flocculent in morphology, with extremely blue UV-NIR colours, these galaxies appear to be

  16. Star-dust geometries in galaxies: The effect of interstellar matter distributions on optical and infrared properties of late-type galaxies

    NASA Technical Reports Server (NTRS)

    Capuano, J. M., Jr.; Thronson, H. A., Jr.; Witt, A. N.

    1993-01-01

    The presence of substantial amounts of interstellar dust in late-type galaxies affects observable parameters such as the optical surface brightness, the color, and the ratio of far-infrared to optical luminosity of these galaxies. We conducted radiative transfer calculations for late-type galaxy environments to examine two different scenarios: (1) the effects of increasing amounts of dust in two fixed geometries with different star distributions; and (2) the effects of an evolving dust-star geometry in which the total amount of dust is held constant, for three different star distributions. The calculations were done for ten photometric bands, ranging from the far-ultraviolet to the near-infrared (K), and scattered light was included in the galactic surface brightness at each wavelength. The energy absorbed throughout these ten photometric bands was assumed to re-emerge in the far-infrared as thermal dust emission. We also considered the evolutionary contraction of a constant amount of dust relative to pre-existing star distributions.

  17. Far-infrared constraints on the contamination by dust-obscured galaxies of high-z dropout searches

    NASA Astrophysics Data System (ADS)

    Boone, F.; Schaerer, D.; Pelló, R.; Lutz, D.; Weiss, A.; Egami, E.; Smail, I.; Rex, M.; Rawle, T.; Ivison, R.; Laporte, N.; Beelen, A.; Combes, F.; Blain, A. W.; Richard, J.; Kneib, J.-P.; Zamojski, M.; Dessauges-Zavadsky, M.; Altieri, B.; van der Werf, P.; Swinbank, M.; Pérez-González, P. G.; Clement, B.; Nordon, R.; Magnelli, B.; Menten, K. M.

    2011-10-01

    The spectral energy distributions (SED) of dusty galaxies at intermediate redshift may look similar to very high-redshift galaxies in the optical/near infrared (NIR) domain. This can lead to the contamination of high-redshift galaxy searches based on broad-band optical/NIR photometry by lower redshift dusty galaxies because both kind of galaxies cannot be distinguished. The contamination rate could be as high as 50%. This work shows how the far-infrared (FIR) domain can help to recognize likely low-z interlopers in an optical/NIR search for high-z galaxies. We analyze the FIR SEDs of two galaxies that are proposed to be very high-redshift (z > 7) dropout candidates based on deep Hawk-I/VLT observations. The FIR SEDs are sampled with PACS/Herschel at 100 and 160 μm, with SPIRE/Herschel at 250, 350 and 500 μm and with LABOCA/APEX at 870 μm. We find that redshifts > 7 would imply extreme FIR SEDs (with dust temperatures >100 K and FIR luminosities >1013 L⊙). At z ~ 2, instead, the SEDs of both sources would be compatible with those of typical ultra luminous infrared galaxies or submillimeter galaxies. Considering all available data for these sources from visible to FIR we re-estimate the redshifts and find z ~ 1.6-2.5. Owing to the strong spectral breaks observed in these galaxies, standard templates from the literature fail to reproduce the visible-to-near-IR part of the SEDs even when additional extinction is included. These sources strongly resemble dust-obscured galaxies selected in Spitzer observations with extreme visible-to-FIR colors, and the galaxy GN10 at z = 4. Galaxies with similar SEDs could contaminate other high-redshift surveys.

  18. Polarimetric imaging of the polar ring galaxy NGC 660 - evidence for dust outside the stellar disk

    NASA Astrophysics Data System (ADS)

    Alton, P. B.; Stockdale, D. P.; Scarrott, S. M.; Wolstencroft, R. D.

    2000-05-01

    Optical imaging polarimetry has been carried out for the polar ring, starburst galaxy NGC 660. This galaxy has a highly inclined, severely tidally-disturbed disk which is surrounded by a gas-rich, polar ring. We detect scattered light from a large part of the halo and this is attributable to dust grains residing up to =~ 2.5 kpc from the stellar disk. There is evidence from emission-line imaging carried out in the past, that NGC 660 is host to an energetic outflow of hot gas along the minor axis (a `superwind'). Our results indicate that dust grains are entrained in this same outflow. Polarization due to scattering, however, is also present at positions away from the minor axis suggesting that grains may also be displaced from the stellar disk by tidal forces exerted during galactic collisions. Where the polar ring occludes the stellar disk we observe polarization due to magnetically aligned, dichroic grains. By comparing the recorded polarization with the associated optical extinction we infer that the magnetic field in the ring has a lower (but still comparable) strength to the magnetic field in the Milky Way. We also derive a dust-to-gas ratio for the ring and this is about a factor of 2-3 lower than in the solar neighbourhood (but close to the value measured in some nearby spirals). If the ring comprises the remnants of the `interloper' which collided with NGC 660, we expect that the ruptured galaxy was a massive, metal-rich spiral.

  19. Dust Grains and the Luminosity of Circumnuclear Water Masers in Active Galaxies

    NASA Technical Reports Server (NTRS)

    Collison, Alan J.; Watson, William D.

    1995-01-01

    In previous calculations for the luminosities of 22 GHz water masers, the pumping is reduced and ultimately quenched with increasing depth into the gas because of trapping of the infrared (approximately equals 30-150 micrometers), spectral line radiation of the water molecule. When the absorption (and reemission) of infrared radiation by dust grains is included, we demonstrate that the pumping is no longer quenched but remains constant with increasing optical depth. A temperature difference between the grains and the gas is required. Such conditions are expected to occur, for example, in the circumnuclear masing environments created by X-rays in active galaxies. Here, the calculated 22 GHz maser luminosities are increased by more than an order of magnitude. Application to the well-studied, circumnuclear masing disk in the galaxy NGC 4258 yields a maser luminosity near that inferred from observations if the observed X-ray flux is assumed to be incident onto only the inner surface of the disk.

  20. The metallicity and dust content of a redshift 5 gamma-ray burst host galaxy

    SciTech Connect

    Sparre, M.; Krühler, T.; Fynbo, J. P. U.; Watson, D. J.; De Ugarte Postigo, A.; Hjorth, J.; Malesani, D.; Hartoog, O. E.; Kaper, L.; Wiersema, K.; D'Elia, V.; Afonso, P. M. J.; Covino, S.; Flores, H.; Goldoni, P.; Jakobsson, P.; Klose, S.; Levan, A. J.; and others

    2014-04-20

    Observations of the afterglows of long gamma-ray bursts (GRBs) allow the study of star-forming galaxies across most of cosmic history. Here we present observations of GRB 111008A, from which we can measure metallicity, chemical abundance patterns, dust-to-metals ratio (DTM), and extinction of the GRB host galaxy at z = 5.0. The host absorption system is a damped Lyα absorber with a very large neutral hydrogen column density of log N(H I)/cm{sup −2}=22.30±0.06 and a metallicity of [S/H] = –1.70 ± 0.10. It is the highest-redshift GRB with such a precise metallicity measurement. The presence of fine-structure lines confirms the z = 5.0 system as the GRB host galaxy and makes this the highest redshift where Fe II fine-structure lines have been detected. The afterglow is mildly reddened with A{sub V} = 0.11 ± 0.04 mag, and the host galaxy has a DTM that is consistent with being equal to or lower than typical values in the Local Group.

  1. Do Lyman-alpha photons escape from star-forming galaxies through dust holes?

    NASA Astrophysics Data System (ADS)

    France, Kevin; Wofford, A.; Leitherer, C.; Fleming, B.; McCandliss, S. R.; Nell, N.

    2014-01-01

    H I Lyman-alpha (LyA) is commonly used as a signpost for the entire galaxy at redshifts z>2, and yet spatially and kinematically resolved views of the local conditions within galaxies that determine the integrated properties of this line are scarce. We obtained Hubble Space Telescope (HST) images in continuum-subtracted LyA, H-alpha, H-beta, and far-UV continuum of three low-inclination spiral star-forming galaxies located at redshifts z=0.02, 0.03, and 0.05. This was accomplished using the UVIS and SBC channels of the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS), respectively. Previous HST spectroscopy obtained by our team with the Cosmic Origins Spectrograph (COS) showed that the galaxies display different integrated LyA profiles within their central few kiloparsecs, i.e., pure absorption, single emission, and double emission, which are representative of what is observed between redshifts 0-3. This data is useful for establishing the relative importance of starburst phase, dust content, and gas kinematics in determining the LyA escape. We present preliminary results that combine our spectroscopic and imaging observations.

  2. ALMA Maps of Dust and Warm Dense Gas Emission in the Starburst Galaxy IC 5179

    NASA Astrophysics Data System (ADS)

    Zhao, Yinghe; Lu, Nanyao; Díaz-Santos, Tanio; Xu, C. Kevin; Gao, Yu; Charmandaris, Vassilis; van der Werf, Paul; Zhang, Zhi-Yu; Cao, Chen

    2017-08-01

    We present our high-resolution (0.″15 × 0.″13, ˜34 pc) observations of the CO (6-5) line emission, which probes the warm and dense molecular gas, and the 434 μm dust continuum emission in the nuclear region of the starburst galaxy IC 5179, conducted with the Atacama Large Millimeter Array (ALMA). The CO (6-5) emission is spatially distributed in filamentary structures with many dense cores and shows a velocity field that is characteristic of a circumnuclear rotating gas disk, with 90% of the rotation speed arising within a radius of ≲150 pc. At the scale of our spatial resolution, the CO (6-5) and dust emission peaks do not always coincide, with their surface brightness ratio varying by a factor of ˜10. This result suggests that their excitation mechanisms are likely different, as further evidenced by the southwest to northeast spatial gradient of both CO-to-dust continuum ratio and Pa-α equivalent width. Within the nuclear region (radius ˜ 300 pc) and with a resolution of ˜34 pc, the CO line flux (dust flux density) detected in our ALMA observations is 180 ± 18 Jy km s-1 (71 ± 7 mJy), which accounts for 22% (2.4%) of the total value measured by Herschel. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

  3. Reverberation measurements of the inner radius of the dust torus in 17 Seyfert galaxies

    SciTech Connect

    Koshida, Shintaro; Minezaki, Takeo; Yoshii, Yuzuru; Sakata, Yu; Sugawara, Shota; Kobayashi, Yukiyasu; Suganuma, Masahiro; Enya, Keigo; Tomita, Hiroyuki; Aoki, Tsutomu; Peterson, Bruce A. E-mail: minezaki@ioa.s.u-tokyo.ac.jp

    2014-06-20

    We present the results of a dust reverberation survey for 17 nearby Seyfert 1 galaxies, which provides the largest homogeneous data collection for the radius of the innermost dust torus. A delayed response of the K-band light curve after the V-band light curve was found for all targets, and 49 measurements of lag times between the flux variation of the dust emission in the K band and that of the optical continuum emission in the V band were obtained by the cross-correlation function analysis and also by an alternative method for estimating the maximum likelihood lag. The lag times strongly correlated with the optical luminosity in the luminosity range of M{sub V} = –16 to –22 mag, and the regression analysis was performed to obtain the correlation log Δt (days) = –2.11 – 0.2 M{sub V} assuming Δt∝L {sup 0.5}, which was theoretically expected. We discuss the possible origins of the intrinsic scatter of the dust lag-luminosity correlation, which was estimated to be approximately 0.13 dex, and we find that the difference of internal extinction and delayed response of changes in lag times to the flux variations could have partly contributed to intrinsic scatter. However, we could not detect any systematic change of the correlation with the subclass of the Seyfert type or the Eddington ratio. Finally, we compare the dust reverberation radius with the near-infrared interferometric radius of the dust torus and the reverberation radius of broad Balmer emission lines. The interferometric radius in the K band was found to be systematically larger than the dust reverberation radius in the same band by the about a factor of two, which could be interpreted by the difference between the flux-weighted radius and response-weighted radius of the innermost dust torus. The reverberation radius of the broad Balmer emission lines was found to be systematically smaller than the dust reverberation radius by about a factor of four to five, which strongly supports the unified

  4. VALIDATION OF THE EQUILIBRIUM MODEL FOR GALAXY EVOLUTION TO z ∼ 3 THROUGH MOLECULAR GAS AND DUST OBSERVATIONS OF LENSED STAR-FORMING GALAXIES

    SciTech Connect

    Saintonge, Amélie; Lutz, Dieter; Genzel, Reinhard; Tacconi, Linda J.; Berta, Stefano; Förster Schreiber, Natascha M.; Poglitsch, Albrecht; Sturm, Eckhard; Wuyts, Eva; Wuyts, Stijn; Magnelli, Benjamin; Nordon, Raanan; Baker, Andrew J.; Bandara, Kaushala

    2013-11-20

    We combine IRAM Plateau de Bure Interferometer and Herschel PACS and SPIRE measurements to study the dust and gas contents of high-redshift star-forming galaxies. We present new observations for a sample of 17 lensed galaxies at z = 1.4-3.1, which allow us to directly probe the cold interstellar medium of normal star-forming galaxies with stellar masses of ∼10{sup 10} M{sub ☉}, a regime otherwise not (yet) accessible by individual detections in Herschel and molecular gas studies. The lensed galaxies are combined with reference samples of submillimeter and normal z ∼ 1-2 star-forming galaxies with similar far-infrared photometry to study the gas and dust properties of galaxies in the SFR-M{sub *}-redshift parameter space. The mean gas depletion timescale of main-sequence (MS) galaxies at z > 2 is measured to be only ∼450 Myr, a factor of ∼1.5 (∼5) shorter than at z = 1 (z = 0), in agreement with a (1 + z){sup –1} scaling. The mean gas mass fraction at z = 2.8 is 40% ± 15% (44% after incompleteness correction), suggesting a flattening or even a reversal of the trend of increasing gas fractions with redshift recently observed up to z ∼ 2. The depletion timescale and gas fractions of the z > 2 normal star-forming galaxies can be explained under the 'equilibrium model' for galaxy evolution, in which the gas reservoir of galaxies is the primary driver of the redshift evolution of specific star formation rates. Due to their high star formation efficiencies and low metallicities, the z > 2 lensed galaxies have warm dust despite being located on the star formation MS. At fixed metallicity, they also have a gas-to-dust ratio 1.7 times larger than observed locally when using the same standard techniques, suggesting that applying the local calibration of the δ{sub GDR}-metallicity relation to infer the molecular gas mass of high-redshift galaxies may lead to systematic differences with CO-based estimates.

  5. STAR FORMATION AND DUST OBSCURATION IN THE TIDALLY DISTORTED GALAXY NGC 2442

    SciTech Connect

    Pancoast, Anna; Sajina, Anna; Lacy, Mark; Noriega-Crespo, Alberto; Rho, Jeonghee

    2010-11-01

    We present a detailed investigation of the morphological distribution and level of star formation and dust obscuration in the nearby tidally distorted galaxy NGC 2442. Spitzer images in the IR at 3.6, 4.5, 5.8, 8.0, and 24 {mu}m and GALEX images at 1500 A and 2300 A allow us to resolve the galaxy on scales between {approx}240 and 600 pc. We supplement these with archival data in the B, J, H, and K bands. We use the 8 {mu}m, 24 {mu}m, and FUV (1500 A) emission to study the star formation rate (SFR). We find that, globally, these tracers of star formation give a range of results of {approx}6-11 M{sub sun} yr{sup -1}, with the dust-corrected FUV giving the highest value of SFR. We can reconcile the UV- and IR-based estimates by adopting a steeper UV extinction curve that lies in between the starburst (Calzetti) and Small Magellanic Cloud extinction curves. However, the regions of the highest SFR intensity along the spiral arms are consistent with a starburst-like extinction. Overall, the level of star formation we find is higher than previously published for this galaxy, by about a factor of 2, which, contrary to previous conclusions, implies that the interaction that caused the distorted morphology of NGC 2442 likely also triggered increased levels of star formation activity. We also find marked asymmetry in that the north spiral arm has a noticeably higher SFR than the southern arm. The tip of the southern spiral arm shows a likely tidally distorted peculiar morphology. It is UV bright and shows unusual IRAC colors, consistent with other published tidal features IRAC data. Outside of the spiral arms, we discover what appears to be a superbubble, {approx}1.7 kpc across, which is seen most clearly in the IRAC images. Significant H{alpha}, UV, and IR emission in the area also suggest vigorous ongoing star formation. A known, recent supernova (SN 1999ga) is located at the edge of this superbubble. Although speculative at this stage, this area suggests a large star

  6. Star Dust Formation Activities in AzTEC-3: A Starburst Galaxy at z=5.3

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2011-01-01

    Analyses of of high-redshift ultraluminous infrared OR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. In this lecture we add this constraint to the analysis of AzTEC-3, a starburst galaxy at z=5.3. We construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multi wavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

  7. Star and Dust Formation Activities in AzTEC-3: A Starburst Galaxy at z equals 5.3

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2011-01-01

    Analyses of of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. In this lecture we add this constraint to the analysis of AzTEC-3, a starburst galaxy at z=5.3. We construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multi wavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

  8. Star and Dust Formation Activities in AzTEC-3: A Starburst Galaxy at z=5.3

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2011-01-01

    Analyses of of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. In this lecture we add this constraint to the analysis of AzTEC-3, a starburst galaxy at z=5.3. We construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multiwavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

  9. TURBULENT CAULDRON OF STARBIRTH IN NEARBY ACTIVE GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    NASA's Hubble Space Telescope offers a stunning unprecedented close-up view of a turbulent firestorm of starbirth along a nearly edge-on dust disk girdling Centaurus A, the nearest active galaxy to Earth. A ground-based telescopic view (upper left insert) shows that the dust lane girdles the entire elliptical galaxy. This lane has long been considered the dust remnant of a smaller spiral galaxy that merged with the large elliptical galaxy. The spiral galaxy deposited its gas and dust into the elliptical galaxy, and the shock of the collision compressed interstellar gas, precipitating a flurry of star formation. Resembling looming storm clouds, dark filaments of dust mixed with cold hydrogen gas are silhouetted against the incandescent yellow-orange glow from hot gas and stars behind it. Brilliant clusters of young blue stars lie along the edge of the dark dust rift. Outside the rift the sky is filled with the soft hazy glow of the galaxy's much older resident population of red giant and red dwarf stars. The dusty disk is tilted nearly edge-on, its inclination estimated to be only 10 or 20 degrees from our line-of-sight. The dust lane has not yet had enough time since the recent merger to settle down into a flat disk. At this oblique angle, bends and warps in the dust lane cause us to see a rippled 'washboard' structure. The picture is a mosaic of two Hubble Space Telescope images taken with the Wide Field Planetary Camera 2, on Aug. 1, 1997 and Jan. 10, 1998. The approximately natural color is assembled from images taken in blue, green and red light. Details as small as seven light-years across can be resolved. The blue color is due to the light from extremely hot, newborn stars. The reddish-yellow color is due in part to hot gas, in part to older stars in the elliptical galaxy and in part to scattering of blue light by dust -- the same effect that produces brilliant orange sunsets on Earth. Centaurus A (NGC 5128) Fast Facts: Right Ascension: 13: 25.5 (hours

  10. TURBULENT CAULDRON OF STARBIRTH IN NEARBY ACTIVE GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    NASA's Hubble Space Telescope offers a stunning unprecedented close-up view of a turbulent firestorm of starbirth along a nearly edge-on dust disk girdling Centaurus A, the nearest active galaxy to Earth. A ground-based telescopic view (upper left insert) shows that the dust lane girdles the entire elliptical galaxy. This lane has long been considered the dust remnant of a smaller spiral galaxy that merged with the large elliptical galaxy. The spiral galaxy deposited its gas and dust into the elliptical galaxy, and the shock of the collision compressed interstellar gas, precipitating a flurry of star formation. Resembling looming storm clouds, dark filaments of dust mixed with cold hydrogen gas are silhouetted against the incandescent yellow-orange glow from hot gas and stars behind it. Brilliant clusters of young blue stars lie along the edge of the dark dust rift. Outside the rift the sky is filled with the soft hazy glow of the galaxy's much older resident population of red giant and red dwarf stars. The dusty disk is tilted nearly edge-on, its inclination estimated to be only 10 or 20 degrees from our line-of-sight. The dust lane has not yet had enough time since the recent merger to settle down into a flat disk. At this oblique angle, bends and warps in the dust lane cause us to see a rippled 'washboard' structure. The picture is a mosaic of two Hubble Space Telescope images taken with the Wide Field Planetary Camera 2, on Aug. 1, 1997 and Jan. 10, 1998. The approximately natural color is assembled from images taken in blue, green and red light. Details as small as seven light-years across can be resolved. The blue color is due to the light from extremely hot, newborn stars. The reddish-yellow color is due in part to hot gas, in part to older stars in the elliptical galaxy and in part to scattering of blue light by dust -- the same effect that produces brilliant orange sunsets on Earth. Centaurus A (NGC 5128) Fast Facts: Right Ascension: 13: 25.5 (hours

  11. CHARACTERIZING ULTRAVIOLET AND INFRARED OBSERVATIONAL PROPERTIES FOR GALAXIES. I. INFLUENCES OF DUST ATTENUATION AND STELLAR POPULATION AGE

    SciTech Connect

    Mao Yewei; Kong Xu; Kennicutt, Robert C. Jr.; Hao, Cai-Na; Zhou Xu E-mail: xkong@ustc.edu.cn

    2012-09-20

    The correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color (or ultraviolet spectral slope), i.e., the IRX-UV (or IRX-{beta}) relation, found in studies of starburst galaxies is a prevalent recipe for correcting extragalactic dust attenuation. Considerable dispersion in this relation discovered for normal galaxies, however, complicates its usability. In order to investigate the cause of the dispersion and to have a better understanding of the nature of the IRX-UV relation, in this paper, we select five nearby spiral galaxies, and perform spatially resolved studies on each of the galaxies, with a combination of ultraviolet and infrared imaging data. We measure all positions within each galaxy and divide the extracted regions into young and evolved stellar populations. By means of this approach, we attempt to discover separate effects of dust attenuation and stellar population age on the IRX-UV relation for individual galaxies. In this work, in addition to dust attenuation, stellar population age is interpreted to be another parameter in the IRX-UV function, and the diversity of star formation histories is suggested to disperse the age effects. At the same time, strong evidence shows the need for more parameters in the interpretation of observational data, such as variations in attenuation/extinction law. Fractional contributions of different components to the integrated luminosities of the galaxies suggest that the integrated measurements of these galaxies, which comprise different populations, would weaken the effect of the age parameter on IRX-UV diagrams. The dependence of the IRX-UV relation on luminosity and radial distance in galaxies presents weak trends, which offers an implication of selective effects. The two-dimensional maps of the UV color and the infrared-to-ultraviolet ratio are displayed and show a disparity in the spatial distributions between the two galaxy parameters, which offers a spatial interpretation of the scatter

  12. Dust energy balance study of two edge-on spiral galaxies in the Herschel-ATLAS survey

    NASA Astrophysics Data System (ADS)

    De Geyter, Gert; Baes, Maarten; De Looze, Ilse; Bendo, George J.; Bourne, Nathan; Camps, Peter; Cooray, Asantha; De Zotti, Gianfranco; Dunne, Loretta; Dye, Simon; Eales, Steve A.; Fritz, Jacopo; Furlanetto, Cristina; Gentile, Gianfranco; Hughes, Thomas M.; Ivison, Rob J.; Maddox, Steve J.; Michałowski, Michał J.; Smith, Matthew W. L.; Valiante, Elisabetta; Viaene, Sébastien

    2015-08-01

    Interstellar dust in galaxies can be traced either through its extinction effects on the star light or through its thermal emission at infrared wavelengths. Recent radiative transfer studies of several nearby edge-on galaxies have found an apparent inconsistency in the dust energy balance: the radiative transfer models that successfully explain the optical extinction underestimate the observed fluxes by an average factor of 3. We investigate the dust energy balance for IC 4225 and NGC 5166, two edge-on spiral galaxies observed by the Herschel Space Observatory in the frame of the H-ATLAS survey. We start from models which were constrained from optical data and extend them to construct the entire spectral energy distribution of our galaxies. These predicted values are subsequently compared to the observed far-infrared fluxes. We find that including a young stellar population in the modelling is necessary as it plays a non-negligible part in the heating of the dust grains. While the modelling approach for both galaxies is nearly identical, we find two very different results. As is often seen in other edge-on spiral galaxies, the far-infrared emission of our radiative transfer model of IC 4225 underestimates the observed fluxes by a factor of about 3. For NGC 5166 on the other hand, we find that both the predicted spectral energy distribution as well as the simulated images match the observations particularly well. We explore possible reasons for this difference and conclude that it is unlikely that one single mechanism is the cause of the dust energy balance problem in spiral galaxies. We discuss the different approaches that can be considered in order to get a conclusive answer on the origin this discrepancy.

  13. AKARI observations of dust processing in merger galaxies: NGC2782 and NGC7727

    NASA Astrophysics Data System (ADS)

    Onaka, Takashi; Nakamura, Tomohiko; Sakon, Itsuki; Ohsawa, Ryou; Mori, Tamami; Wu, Ronin; Kaneda, Hidehiro

    2015-08-01

    Dust grains are the major reservoir of heavy elements and play significant roles in the thermal balance and chemistry in the interstellar medium. Where dust grains are formed and how they evolve in the ISM are one of the key issues for the understanding of the material evolution in the Universe. Although theoretical studies have been made, very little is so far known observationally about the lifecycle of dust grains in the ISM and that associated with Galactic scale events. The lifecycle of very small carbonaceous grains that contain polycyclic aromatic hydrocarbons (PAHs) or PAH-like atomic groups are of particular interest because they emit distinct band emission in the near- to mid-infrared region and they are thought to be most vulnerable to environmental conditions. PAHs may be formed in carbon-rich stars, while recent AKARI observations suggest that they may be formed by fragmentation of large carbonaceous grains in shocks in a supernova remnant or a galactic wind (Onaka et al. 2010, A&A, 514, 15; Seok et al. 2012, ApJ, 744, 160).Here we report results of AKARI observations of two mergers. NGC2782 (Arp 215) and NGC7727 (Arp 222). NGC2782 is a merger of 200Myr old. It shows a very long western tail of HI gas by a tidal interaction and the eastern tail that consists mainly of stellar components without an appreciable amount of gas and is thought to be a relic of the colliding low-mass galaxy whose gas component has been stripped off Smith 1994, AJ, 107, 1695. We found significant emission at the 7 μm band of the IRC onboard AKARI, which must come from PAH 6.2 and 7.7 μm bands, in the eastern tail. Based on dust model fitting, we found a low abundance of ~10nm size dust despite of the presence of PAHs, suggesting that PAHs may be formed from fragmentation of ~10nm carbonaceous dust grains. NGC7727 is a 1.2Gyr old merger and shows a SED similar to the NGC2782 tail in the northern tail of the merger event product, suggesting also the formation of PAHs from

  14. The heating of mid-infrared dust in the nearby galaxy M33: A testbed for tracing galaxy evolution

    SciTech Connect

    Calapa, Marie D.; Calzetti, Daniela; Draine, Bruce T. E-mail: calzetti@astro.umass.edu; and others

    2014-04-01

    Infrared emission is an invaluable tool for quantifying star formation in galaxies. Because the 8 μm polycyclic aromatic hydrocarbon (PAH) emission has been found to correlate with other well-known star formation tracers, it has widely been used as a star formation rate (SFR) tracer. There are, however, studies that challenge the accuracy and reliability of the 8 μm emission as a SFR tracer. Our study, part of the Herschel (Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA) M33 Extended Survey (HERM33ES) open time key program, aims at addressing this issue by analyzing the infrared emission from the nearby spiral galaxy M33 at the high spatial scale of ∼75 pc. Combining data from the Herschel Space Observatory and the Spitzer Space Telescope, we find that the 8 μm emission is better correlated with the 250 μm emission, which traces cold interstellar gas, than with the 24 μm emission. Furthermore, the L(8)/L(250) ratio is more tightly correlated with the 3.6 μm emission, a tracer of evolved stellar populations and stellar mass, than with a combination of Hα and 24 μm emission, a tracer of SFR. The L(8)/L(24) ratio is highly depressed in 24 μm luminous regions, which correlate with known H II regions. We also compare our results with the dust emission models by Draine and Li. We confirm that the depression of 8 μm PAH emission near star-forming regions is higher than what is predicted by models; this is possibly an effect of increased stellar radiation from young stars destroying the dust grains responsible for the 8 μm emission as already suggested by other authors. We find that the majority of the 8 μm emission is fully consistent with heating by the diffuse interstellar medium, similar to what recently determined for the dust emission in M31 by Draine et al. We also find that the fraction of 8 μm emission associated with the diffuse

  15. Stellar and dust properties of strongly lensed z~1.5-3 star forming galaxies from the Herschel Lensing Survey

    NASA Astrophysics Data System (ADS)

    Sklias, Panos; Schaerer, Daniel; Dessauges-Zavadsky, Miroslava

    2015-08-01

    Understanding and constraining the early cosmic star formation history of the Universe is a key question of galaxy evolution. In the IR, deep surveys are limited by instrumentation/confusion, so gravitational lensing is a potent tool to probe lower luminosities than detectable in blank fields at redshifts above 1.Utilizing the multi-wavelength photometry (optical to IR/submm) from the Herschel Lensing Survey, we perform SED fitting with different variable star formation histories (SFHs) on a small sample of strongly lensed star forming galaxies at z~1.5-3. Although in general SED modeling of dust obscured galaxies is affected by degeneracies (eg., in age-extinction), we reduce them by imposing energy conservation, i.e. by constraining the dust attenuation thanks to the observed IR luminosities.In order to mitigate the small number statistics, we also apply our method on a larger sample from GOODS-Herschel, and explore its effects on physical parameter determination and extent of applicability.Thanks to lensing, we have robust detections of faint sources below the usual confusion limits of the observing instruments, and thus can characterize the properties of normal star-forming galaxies at epochs surrounding the peak of the cosmic star formation history. We constrain the IR luminosities of sources down to 1011 Lsun, estimate dust masses and temperatures, as well as stellar properties. The IR and - when available - nebular emission observations allow us to discriminate between SFHs, and between starbursts, post-starbursts and Main Sequence galaxies. This is illustrated specifically with for the well known galaxy nicknamed the «Cosmic Eye». We observe that most of our sources have warmer dust temperature that low-z galaxies in the same luminosity range. They are comparable to temperatures of bright IR galaxies at high-z, indicative that there is a general rising trend of temperature with redshift, due to the more intensively star-forming environment at earlier

  16. The Herschel Virgo Cluster Survey. III. A constraint on dust grain lifetime in early-type galaxies

    NASA Astrophysics Data System (ADS)

    Clemens, M. S.; Jones, A. P.; Bressan, A.; Baes, M.; Bendo, G. J.; Bianchi, S.; Bomans, D. J.; Boselli, A.; Corbelli, E.; Cortese, L.; Dariush, A.; Davies, J. I.; De Looze, I.; di Serego Alighieri, S.; Fadda, D.; Fritz, J.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Grossi, M.; Hughes, T. M.; Hunt, L. K.; Madden, S.; Pierini, D.; Pohlen, M.; Sabatini, S.; Smith, M. W. L.; Verstappen, J.; Vlahakis, C.; Xilouris, E. M.; Zibetti, S.

    2010-07-01

    Passive early-type galaxies (ETGs) provide an ideal laboratory for studying the interplay between dust formation around evolved stars and its subsequent destruction in a hot gas. Using Spitzer-IRS and Herschel data we compare the dust production rate in the envelopes of evolved AGB stars with a constraint on the total dust mass. Early-type galaxies which appear to be truly passively evolving are not detected by Herschel. We thus derive a distance independent upper limit to the dust grain survival time in the hostile environment of ETGs of <46±25 Myr for amorphous silicate grains. This implies that ETGs which are detected at far-infrared wavelengths have acquired a cool dusty medium via interaction. Given likely time-scales for ram-pressure stripping, this also implies that only galaxies with dust in a cool (atomic) medium can release dust into the intra-cluster medium. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  17. The Herschel Exploitation of Local Galaxy Andromeda (HELGA). VII. A SKIRT radiative transfer model and insights on dust heating

    NASA Astrophysics Data System (ADS)

    Viaene, S.; Baes, M.; Tamm, A.; Tempel, E.; Bendo, G.; Blommaert, J. A. D. L.; Boquien, M.; Boselli, A.; Camps, P.; Cooray, A.; De Looze, I.; De Vis, P.; Fernández-Ontiveros, J. A.; Fritz, J.; Galametz, M.; Gentile, G.; Madden, S.; Smith, M. W. L.; Spinoglio, L.; Verstocken, S.

    2017-03-01

    The radiation from stars heats dust grains in the diffuse interstellar medium and in star-forming regions in galaxies. Modelling this interaction provides information on dust in galaxies, a vital ingredient for their evolution. It is not straightforward to identify the stellar populations heating the dust, and to link attenuation to emission on a sub-galactic scale. Radiative transfer models are able to simulate this dust-starlight interaction in a realistic, three-dimensional setting. We investigate the dust heating mechanisms on a local and global galactic scale, using the Andromeda galaxy (M 31) as our laboratory. We have performed a series of panchromatic radiative transfer simulations of Andromeda with our code SKIRT. The high inclination angle of M 31 complicates the 3D modelling and causes projection effects. However, the observed morphology and flux density are reproduced fairly well from UV to sub-millimeter wavelengths. Our model reveals a realistic attenuation curve, compatible with previous, observational estimates. We find that the dust in M 31 is mainly (91% of the absorbed luminosity) heated by the evolved stellar populations. The bright bulge produces a strong radiation field and induces non-local heating up to the main star-forming ring at 10 kpc. The relative contribution of unevolved stellar populations to the dust heating varies strongly with wavelength and with galactocentric distance. The dust heating fraction of unevolved stellar populations correlates strongly with NUV-r colour and specific star formation rate. These two related parameters are promising probes for the dust heating sources at a local scale. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  18. THE STAR FORMATION HISTORIES OF z {approx} 2 DUST-OBSCURED GALAXIES AND SUBMILLIMETER-SELECTED GALAXIES

    SciTech Connect

    Bussmann, R. S.; Dey, Arjun; Jannuzi, B. T.; Armus, L.; Desai, V.; Soifer, B. T.; Brown, M. J. I.; Gonzalez, A. H.; Melbourne, J.

    2012-01-10

    The Spitzer Space Telescope has identified a population of ultraluminous infrared galaxies (ULIRGs) at z {approx} 2 that may play an important role in the evolution of massive galaxies. We measure the stellar masses (M{sub *}) of two populations of Spitzer-selected ULIRGs that have extremely red R - [24] colors (dust-obscured galaxies, or DOGs) and compare our results with submillimeter-selected galaxies (SMGs). One set of 39 DOGs has a local maximum in their mid-infrared (mid-IR) spectral energy distribution (SED) at rest frame 1.6 {mu}m associated with stellar emission ({sup b}ump DOGs{sup )}, while the other set of 51 DOGs have power-law mid-IR SEDs that are typical of obscured active galactic nuclei ({sup p}ower-law DOGs{sup )}. We measure M{sub *} by applying Charlot and Bruzual stellar population synthesis models to broadband photometry in the rest-frame ultraviolet, optical, and near-infrared of each of these populations. Assuming a simple stellar population and a Chabrier initial mass function, we find that power-law DOGs and bump DOGs are on average a factor of 2 and 1.5 more massive than SMGs, respectively (median and inter-quartile M{sub *} values for SMGs, bump DOGs, and power-law DOGs are log(M{sub *}/M{sub Sun }) = 10.42{sup +0.42}{sub -0.36}, 10.62{sup +0.36}{sub -0.32}, and 10.71{sup +0.40}{sub -0.34}, respectively). More realistic star formation histories drawn from two competing theories for the nature of ULIRGs at z {approx} 2 (major merger versus smooth accretion) can increase these mass estimates by up to 0.5 dex. A comparison of our stellar masses with the instantaneous star formation rate (SFR) in these z {approx} 2 ULIRGs provides a preliminary indication supporting high SFRs for a given M{sub *}, a situation that arises more naturally in major mergers than in smooth accretion-powered systems.

  19. Dust attenuation in z ~ 1 galaxies from Herschel and 3D-HST Hα measurements

    NASA Astrophysics Data System (ADS)

    Puglisi, A.; Rodighiero, G.; Franceschini, A.; Talia, M.; Cimatti, A.; Baronchelli, I.; Daddi, E.; Renzini, A.; Schawinski, K.; Mancini, C.; Silverman, J.; Gruppioni, C.; Lutz, D.; Berta, S.; Oliver, S. J.

    2016-02-01

    We combined the spectroscopic information from the 3D-HST survey with Herschel data to characterize the Hα dust attenuation properties of a sample of 79 main sequence star-forming galaxies at z ~ 1 in the GOODS-S field. The sample was selected in the far-IR at λ = 100 and/or 160 μm and only includes galaxies with a secure Hα detection (S/N > 3). From the low resolution 3D-HST spectra we measured the redshifts and the Hα fluxes for the whole sample. (A factor of 1/1.2 was applied to the observed fluxes to remove the [NII] contamination.) The stellar masses (M⋆), infrared (LIR), and UV luminosities (LUV) were derived from the spectral energy distributions by fitting multiband data from GALEX near-UV to SPIRE 500 μm. We estimated the continuum extinction Estar(B-V) from both the IRX = LIR/LUV ratio and the UV-slope, β, and found excellent agreement between the two. The nebular extinction was estimated from comparison of the observed SFRHα and SFRUV. We obtained f = Estar(B-V) /Eneb(B-V) = 0.93 ± 0.06, which is higher than the canonical value of f = 0.44 measured in the local Universe. Our derived dust correction produces good agreement between the Hα and IR+UV SFRs for galaxies with SFR ≳ 20M⊙/yr and M⋆ ≳ 5 × 1010M⊙, while objects with lower SFR and M⋆ seem to require a smaller f-factor (i.e. higher Hα extinction correction). Our results then imply that the nebular extinction for our sample is comparable to extinction in the optical-UV continuum and suggest that the f-factor is a function of both M⋆ and SFR, in agreement with previous studies.

  20. Dust Attenuation and H(alpha) Star Formation Rates of Z Approx. 0.5 Galaxies

    NASA Technical Reports Server (NTRS)

    Ly, Chun; Malkan, Matthew A.; Kashikawa, Nobunari; Ota, Kazuaki; Shimasaku, Kazuhiro; Iye, Masanori; Currie, Thayne

    2012-01-01

    Using deep narrow-band and broad-band imaging, we identify 401 z approximately 0.40 and 249 z approximately 0.49 H-alpha line-emitting galaxies in the Subaru Deep Field. Compared to other H-alpha surveys at similar redshifts, our samples are unique since they probe lower H-alpha luminosities, are augmented with multi-wavelength (rest-frame 1000AA--1.5 microns) coverage, and a large fraction (20%) of our samples has already been spectroscopically confirmed. Our spectra allow us to measure the Balmer decrement for nearly 60 galaxies with H-beta detected above 5-sigma. The Balmer decrements indicate an average extinction of A(H-alpha)=0.7(uparrow){+1.4}_{-0.7} mag. We find that the Balmer decrement systematically increases with higher H-alpha luminosities and with larger stellar masses, in agreement with previous studies with sparser samples. We find that the SFRs estimated from modeling the spectral energy distribution (SED) is reliable---we derived an "intrinsic" H-alpha luminosity which is then reddened assuming the color excess from SED modeling. The SED-predicted H-alpha luminosity agrees with H-alpha narrow-band measurements over 3 dex (rms of 0.25 dex). We then use the SED SFRs to test different statistically-based dust corrections for H-alpha and find that adopting one magnitude of extinction is inappropriate: galaxies with lower luminosities are less reddened. We find that the luminosity-dependent dust correction of Hopkins et al. yields consistent results over 3 dex (rms of 0.3 dex). Our comparisons are only possible by assuming that stellar reddening is roughly half of nebular reddening. The strong correspondence argue that with SED modeling, we can derive reliable intrinsic SFRs even in the absence of H-alpha measurements at z approximately 0.5.

  1. Dust in Clusters: Separating the Contribution of Galaxies and Intracluster Media

    NASA Astrophysics Data System (ADS)

    Gutiérrez, C. M.; López-Corredoira, M.

    2017-01-01

    We have analyzed a sample of 327 clusters of galaxies, spanning the range of 0.06–0.70 in redshift. Strong constraints on their mean intracluster emission of dust have been obtained using maps and catalogs from the Herschel MerMES project; within a radius of 5 arcmin centered in each cluster, the 95% C.L. limits obtained are 86.6, 48.2, and 30.9 mJy at the observed frequencies of 250, 350, and 500 μm. From these restrictions, and assuming physical parameters typical of interstellar media in the Milky Way, we have obtained tight upper limits on the visual extinction of background galaxies due to the intracluster media (ICM): AV(95% C.L.) ≲ 10‑3 mag. Strong constraints are also obtained for the mass of such dust; for instance, using the data at 350 μm we establish a 95% upper limit of <109 M⊙ within a circle with a radius of 5 arcmin centered in the clusters. This corresponds to a fraction of the total mass of the clusters of 9.5 × 10‑6, and indicates a deficiency in the gas-to-dust ratio in the ICM by about three orders of magnitude in relation to the value found in the Milky Way. Computing the total infrared luminosity of the clusters in three ranges of redshift (0.05–0.24, 0.24–0.42, and 0.42–0.71) and two ranges of mass (<1014 and >1014 M⊙), respectively, a strong evolution of luminosity in redshift (L ∼ z1.5) for both ranges of masses is found. The results indicate a strong declining in star formation rate with time in the last ∼6 Gyr.

  2. Evolved stars in the Local Group galaxies - I. AGB evolution and dust production in IC 1613

    NASA Astrophysics Data System (ADS)

    Dell'Agli, F.; Di Criscienzo, M.; Boyer, M. L.; García-Hernández, D. A.

    2016-08-01

    We used models of thermally pulsing asymptotic giant branch (AGB) stars, which also describe the dust-formation process in the wind, to interpret the combination of near- and mid-infrared photometric data of the dwarf galaxy IC 1613. This is the first time that this approach is extended to an environment different from the Milky Way and the Magellanic Clouds (MCs). Our analysis, based on synthetic population techniques, shows nice agreement between the observations and the expected distribution of stars in the colour-magnitude diagrams obtained with JHK and Spitzer bands. This allows a characterization of the individual stars in the AGB sample in terms of mass, chemical composition and formation epoch of the progenitors. We identify the stars exhibiting the largest degree of obscuration as carbon stars evolving through the final AGB phases, descending from 1-1.25 M⊙ objects of metallicity Z = 10-3 and from 1.5-2.5 M⊙ stars with Z = 2 × 10-3. Oxygen-rich stars constitute the majority of the sample (˜65 per cent), mainly low-mass stars (<2 M⊙) that produce a negligible amount of dust (≤10-7 M⊙ yr-1). We predict the overall dust-production rate from IC 1613, mostly determined by carbon stars, to be ˜6 × 10-7 M⊙ yr-1 with an uncertainty of 30 per cent. The capability of the current generation of models to interpret the AGB population in an environment different from the MCs opens the possibility to extend this kind of analysis to other Local Group galaxies.

  3. A Generalized Power-law Diagnostic for Infrared Galaxies at z > 1: Active Galactic Nuclei and Hot Interstellar Dust

    NASA Astrophysics Data System (ADS)

    Caputi, K. I.

    2013-05-01

    I present a generalized power-law (PL) diagnostic which allows one to identify the presence of active galactic nuclei (AGNs) in infrared (IR) galaxies at z > 1, down to flux densities at which the extragalactic IR background is mostly resolved. I derive this diagnostic from the analysis of 174 galaxies with S ν(24 μm)>80 μJy and spectroscopic redshifts z spec > 1 in the Chandra Deep Field South, for which I study the rest-frame UV/optical/near-IR spectral energy distributions (SEDs), after subtracting a hot-dust, PL component with three possible spectral indices α = 1.3, 2.0, and 3.0. I obtain that 35% of these 24 μm sources are power-law composite galaxies (PLCGs), which I define as those galaxies for which the SED fitting with stellar templates, without any previous PL subtraction, can be rejected with >2σ confidence. Subtracting the PL component from the PLCG SEDs produces stellar mass correction factors <1.5 in >80% of cases. The PLCG incidence is especially high (47%) at 1.0 < z < 1.5. To unveil which PLCGs host AGNs, I conduct a combined analysis of 4 Ms X-ray data, galaxy morphologies, and a graybody modeling of the hot dust. I find that (1) 77% of all the X-ray AGNs in my 24 μm sample at 1.0 < z < 1.5 are recognized by the PLCG criterion; (2) PLCGs with α = 1.3 or 2.0 have regular morphologies and T dust >~ 1000 K, indicating nuclear activity. Instead, PLCGs with α = 3.0 are characterized by disturbed galaxy dynamics, and a hot interstellar medium can explain their dust temperatures T dust ~ 700-800 K. Overall, my results indicate that the fraction of AGNs among 24 μm sources is between ~30% and 52% at 1.0 < z < 1.5.

  4. Dust in the nuclei of the Seyfert galaxies Markarian 231 and NGC 4151

    SciTech Connect

    Jones, B.; Worrall, D.M.; Rodriguez-Espinosa, J.M.; Stein, W.A.

    1984-09-01

    Observations carried out with a 8-13 micron grating-spectrometer of Mrk 231 and NGC 4151 are reported. The Mrk 231 data can be fitted to various thermal dust emission models or a single power law, with dust extinction. In all the model fits, except for that of graphite and silicon carbide grain emission, a component of silicate absorption of optical depth of not more than 0.7 is required. Confirming published work, the absorption being at the redshift of the low-redshift absorption-line system is ruled out. The high values of silicate optical depth absorption do not give ratios to the galaxy's visual extinction which are comparable to those of galactic H II regions. Weak evidence for a 10-micron absorption feature in NGC 4151 is also reported. This is somewhat contrary to expectation, since the visual extinction of NGC 4151 is lower than that of Mrk 231, and since there is evidence to support a nonthermal rather than thermal dust origin for the infrared continuum emission. 46 references.

  5. Infrared images of merging galaxies

    NASA Technical Reports Server (NTRS)

    Wright, G. S.; James, P. A.; Joseph, R. D.; Mclean, I. S.; Doyon, R.

    1990-01-01

    Infrared imaging of interacting galaxies is especially interesting because their optical appearance is often so chaotic due to extinction by dust and emission from star formation regions, that it is impossible to locate the nuclei or determine the true stellar distribution. However, at near-infrared wavelengths extinction is considerably reduced, and most of the flux from galaxies originates from red giant stars that comprise the dominant stellar component by mass. Thus near infrared images offer the opportunity to study directly components of galactic structure which are otherwise inaccessible. Such images may ultimately provide the framework in which to understand the activity taking place in many of the mergers with high Infrared Astronomy Satellite (IRAS) luminosities. Infrared images have been useful in identifying double structures in the nuclei of interacting galaxies which have not even been hinted at by optical observations. A striking example of this is given by the K images of Arp 220. Graham et al. (1990) have used high resolution imaging to show that it has a double nucleus coincident with the radio sources in the middle of the dust lane. The results suggest that caution should be applied in the identification of optical bright spots as multiple nuclei in the absence of other evidence. They also illustrate the advantages of using infrared imaging to study the underlying structure in merging galaxies. The authors have begun a program to take near infrared images of galaxies which are believed to be mergers of disk galaxies because they have tidal tails and filaments. In many of these the merger is thought to have induced exceptionally luminous infrared emission (cf. Joseph and Wright 1985, Sanders et al. 1988). Although the optical images of the galaxies show spectacular dust lanes and filaments, the K images all have a very smooth distribution of light with an apparently single nucleus.

  6. Gas-to-dust ratios in massive star-forming galaxies at z ˜ 1.4

    NASA Astrophysics Data System (ADS)

    Seko, Akifumi; Ohta, Kouji; Yabe, Kiyoto; Hatsukade, Bunyo; Aono, Yuya; Iono, Daisuke

    2016-08-01

    We present results of 12CO(J = 2-1) observations toward four massive star-forming galaxies at z ˜ 1.4 with the Nobeyama 45 m radio telescope. The galaxies are detected with Spitzer/MIPS in 24 μm and Herschel/SPIRE in 250 μm and 350 μm, and they mostly reside in the main sequence. Their gas-phase metallicities derived by the N2 method using the Hα and [N II]λ 6584 emission lines are near the solar value. CO lines are detected toward three galaxies. The molecular-gas masses obtained are (9.6-35) × 1010 M⊙ by adopting the Galactic CO-to-H2 conversion factor and a CO(2-1)/CO(1-0) flux ratio of 3. The dust masses derived from the modified blackbody model (assuming a dust temperature of 35 K and an emissivity index of 1.5) are (2.4-5.4) × 108 M⊙. Resulting gas-to-dust ratios (not accounting for H I mass) at z ˜ 1.4 are 220-1450, which are several times larger than those in local star-forming galaxies. A dependence of the gas-to-dust ratio on the far-infrared luminosity density is not clearly seen.

  7. GAS AND DUST IN A SUBMILLIMETER GALAXY AT z = 4.24 FROM THE HERSCHEL ATLAS

    SciTech Connect

    Cox, P.; Krips, M.; Neri, R.; Omont, A.; Guesten, R.; Menten, K. M.; Wyrowski, F.; Weiss, A.; Beelen, A.; Gurwell, M. A.; Blundell, R.; Dannerbauer, H.; Negrello, M.; Aretxaga, I.; Hughes, D. H.; Auld, R.; Baes, M.; Buttiglione, S.; Cava, A.

    2011-10-20

    We report ground-based follow-up observations of the exceptional source, ID 141, one of the brightest sources detected so far in the Herschel Astrophysical Terahertz Large Area Survey cosmological survey. ID 141 was observed using the IRAM 30 m telescope and Plateau de Bure interferometer (PdBI), the Submillimeter Array, and the Atacama Pathfinder Experiment submillimeter telescope to measure the dust continuum and emission lines of the main isotope of carbon monoxide and carbon ([C I] and [C II]). The detection of strong CO emission lines with the PdBI confirms that ID 141 is at high redshift (z = 4.243 {+-} 0.001). The strength of the continuum and emission lines suggests that ID 141 is gravitationally lensed. The width ({Delta}V{sub FWHM} {approx} 800 km s{sup -1}) and asymmetric profiles of the CO and carbon lines indicate orbital motion in a disk or a merger. The properties derived for ID 141 are compatible with an ultraluminous (L{sub FIR} {approx} (8.5 {+-} 0.3) x 10{sup 13} {mu}{sup -1}{sub L} L{sub sun}, where {mu}{sub L} is the amplification factor), dense (n {approx} 10{sup 4} cm{sup -3}), and warm (T{sub kin} {approx} 40 K) starburst galaxy, with an estimated star formation rate of (0.7-1.7) x 10{sup 4} {mu}{sup -1}{sub L} M{sub sun} yr{sup -1}. The carbon emission lines indicate a dense (n {approx} 10{sup 4} cm{sup -3}) photon-dominated region, illuminated by a far-UV radiation field a few thousand times more intense than that in our Galaxy. In conclusion, the physical properties of the high-z galaxy ID 141 are remarkably similar to those of local ultraluminous infrared galaxies.

  8. Gas and Dust in a Submillimeter Galaxy at z = 4.24 from the Herschel Atlas

    NASA Astrophysics Data System (ADS)

    Cox, P.; Krips, M.; Neri, R.; Omont, A.; Güsten, R.; Menten, K. M.; Wyrowski, F.; Weiß, A.; Beelen, A.; Gurwell, M. A.; Dannerbauer, H.; Ivison, R. J.; Negrello, M.; Aretxaga, I.; Hughes, D. H.; Auld, R.; Baes, M.; Blundell, R.; Buttiglione, S.; Cava, A.; Cooray, A.; Dariush, A.; Dunne, L.; Dye, S.; Eales, S. A.; Frayer, D.; Fritz, J.; Gavazzi, R.; Hopwood, R.; Ibar, E.; Jarvis, M.; Maddox, S.; Michałowski, M.; Pascale, E.; Pohlen, M.; Rigby, E.; Smith, D. J. B.; Swinbank, A. M.; Temi, P.; Valtchanov, I.; van der Werf, P.; de Zotti, G.

    2011-10-01

    We report ground-based follow-up observations of the exceptional source, ID 141, one of the brightest sources detected so far in the Herschel Astrophysical Terahertz Large Area Survey cosmological survey. ID 141 was observed using the IRAM 30 m telescope and Plateau de Bure interferometer (PdBI), the Submillimeter Array, and the Atacama Pathfinder Experiment submillimeter telescope to measure the dust continuum and emission lines of the main isotope of carbon monoxide and carbon ([C I] and [C II]). The detection of strong CO emission lines with the PdBI confirms that ID 141 is at high redshift (z = 4.243 ± 0.001). The strength of the continuum and emission lines suggests that ID 141 is gravitationally lensed. The width (ΔV FWHM ~ 800 km s-1) and asymmetric profiles of the CO and carbon lines indicate orbital motion in a disk or a merger. The properties derived for ID 141 are compatible with an ultraluminous (L FIR ~ (8.5 ± 0.3) × 1013 μ-1 L L sun, where μL is the amplification factor), dense (n ≈ 104 cm-3), and warm (T kin ≈ 40 K) starburst galaxy, with an estimated star formation rate of (0.7-1.7) × 104 μ-1 L M sun yr-1. The carbon emission lines indicate a dense (n ≈ 104 cm-3) photon-dominated region, illuminated by a far-UV radiation field a few thousand times more intense than that in our Galaxy. In conclusion, the physical properties of the high-z galaxy ID 141 are remarkably similar to those of local ultraluminous infrared galaxies.

  9. Search for Hyperluminous Infrared Dust-obscured Galaxies Selected with WISE and SDSS

    NASA Astrophysics Data System (ADS)

    Toba, Y.; Nagao, T.

    2016-03-01

    We aim to search for hyperluminous infrared (IR) galaxies (HyLIRGs) with IR luminosity {L}{{IR}} > 1013 L⊙ by applying the selection method of dust-obscured galaxies (DOGs). They are spatially rare but could correspond to a maximum phase of cosmic star formation (SF) and/or active galactic nucleus (AGN) activity hence, they are a crucial population for understanding the SF and mass assembly history of galaxies. Combining the optical and IR catalogs obtained from the Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE), we performed the extensive HyLIRGs survey; we selected 5311 IR-bright DOGs with i - [22] > 7.0 and flux at 22 μm > 3.8 mJy in 14,555 deg2, where i and [22] are i-band and 22 μm AB magnitudes, respectively. Among them, 67 DOGs have reliable spectroscopic redshifts that enable us to estimate their total IR luminosity based on the spectral energy distribution fitting. Consequently, we successfully discovered 24 HyLIRGs among the 67 spectroscopically confirmed DOGs. We found that (i) i - [22] color of IR-bright DOGs correlates with the total IR luminosity and (ii) the surface number density of HyLIRGs is >0.17 deg-2. A large fraction (˜73%) of IR-bright DOGs with i - [22] > 7.5 show {L}{{IR}} > 1013 L⊙, and the DOG criterion we adopted could be independently effective against the “W1W2-dropout method,” based on four WISE bands, for searching hyperluminous IR populations of galaxies.

  10. Multicolor CCD photometry of six lenticular and spiral galaxies. Stellar population of the galaxies

    NASA Astrophysics Data System (ADS)

    Gusev, A. S.

    2006-03-01

    The results of multicolor surface photometry of the S0 galaxies NGC 524, NGC 1138, and NGC 7280 and the spiral galaxies NGC 532, NGC 783, and NGC 1589 are analyzed. UBVRI observations were acquired with the 1.5-m telescope of the Maidanak Observatory (Uzbekistan), while JHK data were taken from the 2MASS catalog. The brightness and color distributions in the galaxies are analyzed. Extinction in dust lanes in three spiral galaxies is estimated. The contributions of the radiation of the spherical and disk components in different photometric bands are estimated. Two-color diagrams are used to estimate the composition of the stellar populations in various galaxy components. The variations of the color characteristics in the S0 galaxies is due mostly to radial metallicity gradients.

  11. Using HUBBLE SPACE TELESCOPE Imaging of Nuclear Dust Morphology to Rule Out Bars Fueling Seyfert Nuclei

    NASA Astrophysics Data System (ADS)

    Regan, Michael W.; Mulchaey, John S.

    1999-06-01

    If active galactic nuclei (AGN) are powered by the accretion of matter onto massive black holes, how does the gas in the host galaxy lose the required angular momentum to approach the black hole? Gas easily transfers angular momentum to stars in strong bars, making them likely candidates. Although ground-based searches for bars in active galaxies using both optical and near-infrared surface brightness have not found any excess of bars relative to quiescent galaxies, the searches have not been able to rule out small-scale nuclear bars. To look for these nuclear bars we use Hubble Space Telescope Wide Field and Planetary Camera 2 and Near Infrared Camera and Multi-Object Spectrometer color maps to search for the straight dust lane signature of strong bars. Of the twelve Seyfert galaxies in our sample, only three have dust lanes consistent with a strong nuclear bar. Therefore, strong nuclear bars cannot be the primary fueling mechanism for Seyfert nuclei. We do find that a majority of the galaxies show an spiral morphology in their dust lanes. These spiral arms may be a possible fueling mechanism.

  12. HerMES: THE FAR-INFRARED EMISSION FROM DUST-OBSCURED GALAXIES

    SciTech Connect

    Calanog, J. A.; Wardlow, J.; Fu, Hai; Cooray, A.; Assef, R. J.; Bock, J.; Riechers, D.; Schulz, B.; Casey, C. M.; Conley, A.; Farrah, D.; Oliver, S. J.; Roseboom, I. G.; Ibar, E.; Kartaltepe, J.; Magdis, G.; Rigopoulou, D.; Marchetti, L.; Pérez-Fournon, I.; Scott, Douglas; and others

    2013-09-20

    Dust-obscured galaxies (DOGs) are an ultraviolet-faint, infrared-bright galaxy population that reside at z ∼ 2 and are believed to be in a phase of dusty star-forming and active galactic nucleus (AGN) activity. We present far-infrared (far-IR) observations of a complete sample of DOGs in the 2 deg{sup 2} of the Cosmic Evolution Survey. The 3077 DOGs have (z) = 1.9 ± 0.3 and are selected from 24 μm and r {sup +} observations using a color cut of r {sup +} – [24] ≥ 7.5 (AB mag) and S{sub 24} ≥ 100 μJy. Based on the near-IR spectral energy distributions, 47% are bump DOGs (star formation dominated) and 10% are power-law DOGs (AGN-dominated). We use SPIRE far-IR photometry from the Herschel Multi-tiered Extragalactic Survey to calculate the IR luminosity and characteristic dust temperature for the 1572 (51%) DOGs that are detected at 250 μm (≥3σ). For the remaining 1505 (49%) that are undetected, we perform a median stacking analysis to probe fainter luminosities. Herschel-detected and undetected DOGs have average luminosities of (2.8 ± 0.4) × 10{sup 12} L{sub ☉} and (0.77 ± 0.08) × 10{sup 12} L{sub ☉}, and dust temperatures of (33 ± 7) K and (37 ± 5) K, respectively. The IR luminosity function for DOGs with S{sub 24} ≥ 100 μJy is calculated, using far-IR observations and stacking. DOGs contribute 10%-30% to the total star formation rate (SFR) density of the universe at z = 1.5-2.5, dominated by 250 μm detected and bump DOGs. For comparison, DOGs contribute 30% to the SFR density for all z = 1.5-2.5 galaxies with S{sub 24} ≥ 100 μJy. DOGs have a large scatter about the star formation main sequence and their specific SFRs show that the observed phase of star formation could be responsible for their total observed stellar mass at z ∼ 2.

  13. The broad-line region and dust torus size of the Seyfert 1 galaxy PGC 50427

    NASA Astrophysics Data System (ADS)

    Pozo Nuñez, F.; Ramolla, M.; Westhues, C.; Haas, M.; Chini, R.; Steenbrugge, K.; Barr Domínguez, A.; Kaderhandt, L.; Hackstein, M.; Kollatschny, W.; Zetzl, M.; Hodapp, K. W.; Murphy, M.

    2015-04-01

    We present the results of three-year monitoring campaigns of the z = 0.024 type 1 active Galactic nucleus (AGN) PGC 50427. Using robotic telescopes of the Universitätssternwarte Bochum near Cerro Armazones in Chile, we monitored PGC 50427 in the optical and near-infrared (NIR). Through the use of photometric reverberation mapping with broad- and narrowband filters, we determine the size of the broad-line emitting region by measuring the time delay between the variability of the continuum and the Hα emission line. The Hα emission line responds to blue continuum variations with an average rest frame lag of 19.0 ± 1.23 days. Using single epoch spectroscopy obtained with the Southern African Large Telescope (SALT) we determined a broad-line Hα velocity width of 1020 km s-1 and in combination with the rest frame lag and adoption of a geometric scaling factor f = 5.5, we calculate a black hole mass of MBH ~ 17 × 106 M⊙. Using the flux variation gradient method, we separate the host galaxy contribution from that of the AGN to calculate the rest frame 5100 Å luminosity at the time of our monitoring campaign. We measured small luminosity variations in the AGN (~10%) accross the three years of the monitoring campaign. The rest frame lag and the host-subtracted luminosity permit us to derive the position of PGC 50427 in the BLR size - AGN luminosity diagram, which is remarkably close to the theoretically expected relation of R ∝ L0.5. The simultaneous optical and NIR (J and Ks) observations allow us to determine the size of the dust torus through the use of dust reverberation mapping method. We find that the hot dust emission (~1800 K) lags the optical variations with an average rest frame lag of 46.2 ± 2.60 days. The dust reverberation radius and the nuclear NIR luminosity permit us to derive the position of PGC 50427 on the known τ - MV diagram. The simultaneous observations for the broad-line region and dust thermal emission demonstrate that the innermost dust

  14. The structure of NGC at 100, 160, and 200 microns - Continuum dust emission in a quiescent Sb galaxy

    NASA Technical Reports Server (NTRS)

    Engargiola, G.; Harper, D. A.

    1992-01-01

    Observations of NGC 4565 at 100, 160, and 200 microns with the University of Chicago Far-Infrared Camera and the NASA-Kuiper Airborne Observatory are reported. In order to examine the dependence of FIR emission on spiral structure and star formation activity, these observations of NGC 4565, a quiescent Sb galaxy, are compared with observations of NGC 6946, an active Sc galaxy, made by Engargiola (1991) using the same instruments. Warm dust (30 K) in a bisymmetric spiral pattern superposed on an exponential disk of cool dust (20 K) can account for the FIR morphology of NGC 4565. Optical and IR data suggest that there are more embedded sources heating dust locally in the southeast arm region and more UV radiation from unobscured young stellar associations heating the cool, neutral medium in the northeast arm region.

  15. The large scale gas and dust distribution in the galaxy: Implications for star formation

    NASA Technical Reports Server (NTRS)

    Sodroski, T. J.; Dwek, E.; Hauser, M. G.; Kerr, F. J.

    1987-01-01

    Infrared Astronomy Observations are presented for the diffuse infrared (IR) emissions from the galactic plane at wavelengths of 60 and 100 microns and the total far infrared intensity and its longitudinal variations in the disk were derived. Using available CO, 5 GHz radio-continuum, and HI data, the IR luminosity per hydrogen mass and the ingrared excess (IRE) ratio in the Galaxy were derived. The longitudinal profiles of the 60 and 100 micron emission were linearly decomposed into three components that are associated with molecular (H2), neutral (HI), and ionized (HII) phases in the interstellar medium (ISM), and the relevant dust properties were derived in each phase. Implications of the findings for various models of the diffuse IR emisison and for star formation in the galactic disk are discussed.

  16. HELGA: The Herschel Exploitation of the Local Galaxy Andromeda: Sub-mm Morphology and Dust Properties

    NASA Astrophysics Data System (ADS)

    Fritz, J.; Smith, M. W. L.; Kirk, J.; Helga Collaboration

    2014-03-01

    The results from a large-field Far-Infrared (FIR) and sub-millimeter (sub-mm) survey of our neighbor galaxy M31 are presented. We have obtained Herschel images of a ˜ 5.5 × 2.5 degree area centered on Andromeda. Using 21-cm atomic hydrogen maps, we are able to disentangle genuine emission from M31 from that for foreground Galactic cirrus, allowing us to recognize dusty structures out to ˜ 31 kpc from the center. We first characterize the FIR and sub-mm morphology and then, by de-projecting Herschel maps and running an ad-hoc source extraction algorithm, we reconstruct the intrinsic morphology and the spatial distribution of the molecular complexes. Finally, we study the spatially resolved properties of the dust (temperature, emissivity, mass, etc.) by means of a pixel-by-pixel SED fitting approach.

  17. Inferring the three-dimensional distribution of dust in the Galaxy with a non-parametric method . Preparing for Gaia

    NASA Astrophysics Data System (ADS)

    Rezaei Kh., S.; Bailer-Jones, C. A. L.; Hanson, R. J.; Fouesneau, M.

    2017-02-01

    We present a non-parametric model for inferring the three-dimensional (3D) distribution of dust density in the Milky Way. Our approach uses the extinction measured towards stars at different locations in the Galaxy at approximately known distances. Each extinction measurement is proportional to the integrated dust density along its line of sight (LoS). Making simple assumptions about the spatial correlation of the dust density, we can infer the most probable 3D distribution of dust across the entire observed region, including along sight lines which were not observed. This is possible because our model employs a Gaussian process to connect all LoS. We demonstrate the capability of our model to capture detailed dust density variations using mock data and simulated data from the Gaia Universe Model Snapshot. We then apply our method to a sample of giant stars observed by APOGEE and Kepler to construct a 3D dust map over a small region of the Galaxy. Owing to our smoothness constraint and its isotropy, we provide one of the first maps which does not show the "fingers of God" effect.

  18. Dissection of a Galaxy

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Sometimes, the best way to understand how something works is to take it apart. The same is true for galaxies like NGC 300, which NASA's Spitzer Space Telescope has divided into its various parts. NGC 300 is a face-on spiral galaxy located 7.5 million light-years away in the southern constellation Sculptor.

    This false-color image taken by the infrared array camera on Spitzer readily distinguishes the main star component of the galaxy (blue) from its dusty spiral arms (red). The star distribution peaks strongly in the central bulge where older stars congregate, and tapers off along the arms where younger stars reside.

    Thanks to Spitzer's unique ability to sense the heat or infrared emission from dust, astronomers can now clearly trace the embedded dust structures within NGC 300's arms. When viewed at visible wavelengths, the galaxy's dust appears as dark lanes, largely overwhelmed by bright starlight. With Spitzer, the dust - in particular organic compounds called polycyclic aromatic hydrocarbons - can be seen in vivid detail (red). These organic molecules are produced, along with heavy elements, by the stellar nurseries that pepper the arms.

    The findings provide a better understanding of spiral galaxy mechanics and, in the future, will help decipher more distant galaxies, whose individual components cannot be resolved.

    This image was taken on Nov. 21, 2003 and is composed of photographs obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

  19. Dissection of a Galaxy

    NASA Image and Video Library

    2004-05-11

    Sometimes, the best way to understand how something works is to take it apart. The same is true for galaxies like NGC 300, which NASA's Spitzer Space Telescope has divided into its various parts. NGC 300 is a face-on spiral galaxy located 7.5 million light-years away in the southern constellation Sculptor. This false-color image taken by the infrared array camera on Spitzer readily distinguishes the main star component of the galaxy (blue) from its dusty spiral arms (red). The star distribution peaks strongly in the central bulge where older stars congregate, and tapers off along the arms where younger stars reside. Thanks to Spitzer's unique ability to sense the heat or infrared emission from dust, astronomers can now clearly trace the embedded dust structures within NGC 300's arms. When viewed at visible wavelengths, the galaxy's dust appears as dark lanes, largely overwhelmed by bright starlight. With Spitzer, the dust - in particular organic compounds called polycyclic aromatic hydrocarbons - can be seen in vivid detail (red). These organic molecules are produced, along with heavy elements, by the stellar nurseries that pepper the arms. The findings provide a better understanding of spiral galaxy mechanics and, in the future, will help decipher more distant galaxies, whose individual components cannot be resolved. This image was taken on Nov. 21, 2003 and is composed of photographs obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red). http://photojournal.jpl.nasa.gov/catalog/PIA05879

  20. M81 Galaxy is Pretty in Pink

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The perfectly picturesque spiral galaxy known as Messier 81, or M81, looks sharp in this new composite from NASA's Spitzer and Hubble space telescopes and NASA's Galaxy Evolution Explorer. M81 is a 'grand design' spiral galaxy, which means its elegant arms curl all the way down into its center. It is located about 12 million light-years away in the Ursa Major constellation and is one of the brightest galaxies that can be seen from Earth through telescopes.

    The colors in this picture represent a trio of light wavelengths: blue is ultraviolet light captured by the Galaxy Evolution Explorer; yellowish white is visible light seen by Hubble; and red is infrared light detected by Spitzer. The blue areas show the hottest, youngest stars, while the reddish-pink denotes lanes of dust that line the spiral arms. The orange center is made up of older stars.

  1. M81 Galaxy is Pretty in Pink

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The perfectly picturesque spiral galaxy known as Messier 81, or M81, looks sharp in this new composite from NASA's Spitzer and Hubble space telescopes and NASA's Galaxy Evolution Explorer. M81 is a 'grand design' spiral galaxy, which means its elegant arms curl all the way down into its center. It is located about 12 million light-years away in the Ursa Major constellation and is one of the brightest galaxies that can be seen from Earth through telescopes.

    The colors in this picture represent a trio of light wavelengths: blue is ultraviolet light captured by the Galaxy Evolution Explorer; yellowish white is visible light seen by Hubble; and red is infrared light detected by Spitzer. The blue areas show the hottest, youngest stars, while the reddish-pink denotes lanes of dust that line the spiral arms. The orange center is made up of older stars.

  2. NVESD mine lane facility

    NASA Astrophysics Data System (ADS)

    Habersat, James D.; Marshall, Christopher; Maksymonko, George

    2003-09-01

    The NVESD Mine Lane Facility has recently undergone an extensive renovation. It now consists of an indoor, dry lane portion, a greenhouse portion with moisture-controlled lanes, a control room, and two outdoor lanes. The indoor structure contains six mine lanes, each approximately 2.5m (width) × 1.2m (depth) × 33m(length). These lanes contain six different soil types: magnetite/sand, silt, crusher run gravel (bluestone gravel), bank run gravel (tan gravel), red clay, and white sand. An automated trolley system is used for mounting the various mine detection systems and sensors under test. Data acquisition and data logging is fully automated. The greenhouse structure was added to provide moisture controlled lanes for measuring the effect of moisture on sensor effectiveness. A gantry type crane was installed to permit remotely controlled positioning of a sensor package over any portion of the greenhouse lanes at elevations from ground level up to 5m without shadowing the target area. The roof of the greenhouse is motorized, and can be rolled back to allow full solar loading. A control room overlooking the lanes is complete with recording and monitoring devices and contains controls to operate the trolleys. A facility overview is presented and typical results from recent data collection exercises are presented.

  3. Detecting Reddening by Dust for Star Clusters in the Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Cohn, Amy; Dorman, C.; Guhathakurta, P.; PHAT Collaboration

    2014-01-01

    We have developed a technique to detect reddening by interstellar dust of star clusters in the Andromeda Galaxy, using Hubble Space Telescope ACS/WFC imaging in B and I and spectroscopic data from Keck II DEIMOS spectrograph. These data are from the Panchromatic Hubble Andromeda Treasury (PHAT) and Spectroscopic and Panchromatic Landscape of Andromeda's Stellar Halo (SPLASH) surveys. We compared the observed color indices from the PHAT data to the intrinsic color indices quantitatively inferred from a chi-squared goodness of fit comparison between the SPLASH data and a library of template spectra, to detect reddening. The spectral comparison utilizes the strength of the titanium oxide bands. This technique will be applied to an additional 150 star clusters, in Andromeda, to determine the amount of reddening they have experienced. It will also be used as part of the process of correcting for the reddening, developing a reddening law, and learning more about the physical properties of the dust. This research was carried out under the auspices of UCSC's Science Internship Program. We thank the National Aeronautics and Space Administration and the National Science Foundation for funding support.

  4. HUBBLE SPACE TELESCOPE MORPHOLOGIES OF z {approx} 2 DUST-OBSCURED GALAXIES. II. BUMP SOURCES

    SciTech Connect

    Bussmann, R. S.; Dey, Arjun; Lotz, J.; Jannuzi, B. T.; Armus, L.; Desai, V.; Soifer, B. T.; Brown, M. J. I.; Eisenhardt, P.; Higdon, J.; Higdon, S.; Le Floc'h, E.; Melbourne, J.; Weedman, D.

    2011-05-20

    We present Hubble Space Telescope imaging of 22 ultra-luminous infrared galaxies (ULIRGs) at z {approx} 2 with extremely red R - [24] colors (called dust-obscured galaxies, or DOGs) which have a local maximum in their spectral energy distribution (SED) at rest-frame 1.6 {mu}m associated with stellar emission. These sources, which we call 'bump DOGs', have star formation rates (SFRs) of 400-4000 M{sub sun} yr{sup -1} and have redshifts derived from mid-IR spectra which show strong polycyclic aromatic hydrocarbon emission-a sign of vigorous ongoing star formation. Using a uniform morphological analysis, we look for quantifiable differences between bump DOGs, power-law DOGs (Spitzer-selected ULIRGs with mid-IR SEDs dominated by a power law and spectral features that are more typical of obscured active galactic nuclei than starbursts), submillimeter-selected galaxies, and other less-reddened ULIRGs from the Spitzer Extragalactic First Look Survey. Bump DOGs are larger than power-law DOGs (median Petrosian radius of 8.4 {+-} 2.7 kpc versus 5.5 {+-} 2.3 kpc) and exhibit more diffuse and irregular morphologies (median M{sub 20} of -1.08 {+-} 0.05 versus -1.48 {+-} 0.05). These trends are qualitatively consistent with expectations from simulations of major mergers in which merging systems during the peak SFR period evolve from M{sub 20} = -1.0 to M{sub 20} = -1.7. Less-obscured ULIRGs (i.e., non-DOGs) tend to have more regular, centrally peaked, single-object morphologies rather than diffuse and irregular morphologies. This distinction in morphologies may imply that less-obscured ULIRGs sample the merger near the end of the peak SFR period. Alternatively, it may indicate that the intense star formation in these less-obscured ULIRGs is not the result of a recent major merger.

  5. Hubble Space Telescope Morphologies of z ~ 2 Dust-obscured Galaxies. II. Bump Sources

    NASA Astrophysics Data System (ADS)

    Bussmann, R. S.; Dey, Arjun; Lotz, J.; Armus, L.; Brown, M. J. I.; Desai, V.; Eisenhardt, P.; Higdon, J.; Higdon, S.; Jannuzi, B. T.; Le Floc'h, E.; Melbourne, J.; Soifer, B. T.; Weedman, D.

    2011-05-01

    We present Hubble Space Telescope imaging of 22 ultra-luminous infrared galaxies (ULIRGs) at z ≈ 2 with extremely red R - [24] colors (called dust-obscured galaxies, or DOGs) which have a local maximum in their spectral energy distribution (SED) at rest-frame 1.6 μm associated with stellar emission. These sources, which we call "bump DOGs," have star formation rates (SFRs) of 400-4000 M sun yr-1 and have redshifts derived from mid-IR spectra which show strong polycyclic aromatic hydrocarbon emission—a sign of vigorous ongoing star formation. Using a uniform morphological analysis, we look for quantifiable differences between bump DOGs, power-law DOGs (Spitzer-selected ULIRGs with mid-IR SEDs dominated by a power law and spectral features that are more typical of obscured active galactic nuclei than starbursts), submillimeter-selected galaxies, and other less-reddened ULIRGs from the Spitzer Extragalactic First Look Survey. Bump DOGs are larger than power-law DOGs (median Petrosian radius of 8.4 ± 2.7 kpc versus 5.5 ± 2.3 kpc) and exhibit more diffuse and irregular morphologies (median M 20 of -1.08 ± 0.05 versus -1.48 ± 0.05). These trends are qualitatively consistent with expectations from simulations of major mergers in which merging systems during the peak SFR period evolve from M 20 = -1.0 to M 20 = -1.7. Less-obscured ULIRGs (i.e., non-DOGs) tend to have more regular, centrally peaked, single-object morphologies rather than diffuse and irregular morphologies. This distinction in morphologies may imply that less-obscured ULIRGs sample the merger near the end of the peak SFR period. Alternatively, it may indicate that the intense star formation in these less-obscured ULIRGs is not the result of a recent major merger.

  6. AGN - Dust-Obscured Galaxies at z~1-3 revealed by near-to-far infrared SED-fitting

    NASA Astrophysics Data System (ADS)

    Riguccini, Laurie

    Dust-Obscured galaxies (DOGs, Dey et al. 2008) are bright 24μm-selected sources with extreme obscuration at optical wavelengths (F24μ m /F R > 982). Recent studies (Dey et al. 2008, Bussmann et al. 2009) describe an evolutionary scenario in which the starbursting nature of submillimeter galaxies (SMGs) evolves into the composite nature of DOGs as an underlying AGN grows; this is followed by a quasar phase that terminates star formation (SF), leading to the formation of a passive, massive elliptical galaxy. Within this context, DOGs could provide a key insight to an extremely dusty stage in the evolution of galaxies at z ~ 2, where both AGN and SF activity coexist.

  7. Hubble Space Telescope Observations of the CFA Seyfert 2 Galaxies: The Fueling of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Martini, Paul; Pogge, Richard W.

    1999-12-01

    We present an investigation of possible fueling mechanisms operating in the inner kiloparsec of Seyfert galaxies. We analyze visible and near-infrared Hubble Space Telescope images of 24 Seyfert 2 galaxies from the CfA Redshift Survey sample. In particular, we are searching for the morphological signatures of dynamical processes responsible for transporting gas from kiloparsec scales into the nucleus. The circumnuclear regions are very rich in gas and dust, often taking the form of nuclear spiral dust lanes on scales of a few hundred parsecs. While these nuclear spirals are found in 20 of our 24 Seyfert galaxies, we find only five nuclear bars among the entire sample, strongly reinforcing the conclusions of other investigators that nuclear bars are not the primary means of transporting this material into the nucleus. An estimate of the gas density in the nuclear spirals, based on extinction measurements, suggests that the nuclear spiral dust lanes are probably shocks in nuclear gas disks that are not strongly self-gravitating. Since shocks can dissipate energy and angular momentum, these spiral dust lanes may be the channels by which gas from the host galaxy disks is being fed into the central engines.

  8. Dust Attenuation of the Nebular Regions of z ~ 2 Star-forming Galaxies: Insight from UV, IR, and Emission Lines

    NASA Astrophysics Data System (ADS)

    De Barros, S.; Reddy, N.; Shivaei, I.

    2016-04-01

    We use a sample of 149 spectroscopically confirmed UV-selected galaxies at z ˜ 2 to investigate the relative dust attenuation of the stellar continuum and the nebular emission lines. For each galaxy in the sample, at least one rest-frame optical emission line (Hα/[N ii] λ6583 or [O iii] λ5007) measurement has been taken from the litterature, and 41 galaxies have additional Spitzer/MIPS 24 μm observations that are used to infer infrared luminosities. We use a spectral energy distribution (SED) fitting code that predicts nebular line strengths when fitting the stellar populations of galaxies in our sample, and we perform comparisons between the predictions of our models and the observed/derived physical quantities. We find that on average our code is able to reproduce all the physical quantities (e.g., UV β slopes, infrared luminosities, emission line fluxes), but we need to apply a higher dust correction to the nebular emission compared to the stellar emission for the largest star formation rate (SFR) (log SFR/M⊙ yr-1 > 1.82, Salpeter initial mass function). We find a correlation between SFR and the difference in nebular and stellar color excesses, which could resolve the discrepant results regarding nebular dust correction at z ˜ 2 from previous studies.

  9. PEP/HerMES/COSMOS: What are the dust properties of z ˜ 3 lyman break galaxies?

    NASA Astrophysics Data System (ADS)

    Álvarez-Márquez, A.; Burgarella, D.; Buat, V.; Heinis, S.; Pep/Hermes/Cosmos Teams

    2015-05-01

    Context. Since the mid-90's, the sample of Lyman break galaxies has been growing up thanks to the deeper and deeper sensitivities of the telescope in optical and in near-infrared for objects at z > 2.5. However, the dust properties of these Lyman break galaxies are still elusive of badly known because the samples are small and/or biased.} Aims. We explore the dust properties in a statistical way of a sample of Lyman break galaxies (LBGs) that can not be individually detected in Herschel maps. Methods. We apply a stacking method in the Herschel and AzTEC maps to LBGs selected at 2.5 < z < 3.5 by dropout technique. Thanks to the size of the sample (˜22 000 LBGs), we can split it in several bins as a function of their ultraviolet luminosity (L_{FUV}), their ultraviolet slope (β_{UV}) and their stellar mass (M_{*}) to better catch their variety. The stacking is corrected for the incompleteness in the priors and for the clustering of the stacked galaxies in ultraviolet. Results. We obtain the full infrared spectral energy distributions of our LBGs as a function of their L_{FUV}, their β_{UV} and their M_* and we can characterize them in terms of their dust attenuation A_{FUV}, their star formation rate (SFR).

  10. Interferometric follow-up of WISE hyper-luminous hot, dust-obscured galaxies

    SciTech Connect

    Wu, Jingwen; Wright, Edward L.; Bussmann, R. Shane; Tsai, Chao-Wei; Eisenhardt, Peter R. M.; Stern, Daniel; Moustakas, Leonidas; Petric, Andreea; Blain, Andrew; Bridge, Carrie R.; Benford, Dominic J.; Assef, Roberto J.; Gelino, Christopher R.

    2014-09-20

    The Wide-field Infrared Survey Explorer (WISE) has discovered an extraordinary population of hyper-luminous dusty galaxies that are faint in the two bluer passbands (3.4 μm and 4.6 μm) but are bright in the two redder passbands of WISE (12 μm and 22 μm). We report on initial follow-up observations of three of these hot, dust-obscured galaxies, or Hot DOGs, using the Combined Array for Research in Millimeter-wave Astronomy and the Submillimeter Array interferometer arrays at submillimeter/millimeter wavelengths. We report continuum detections at ∼1.3 mm of two sources (WISE J014946.17+235014.5 and WISE J223810.20+265319.7, hereafter W0149+2350 and W2238+2653, respectively), and upper limits to CO line emission at 3 mm in the observed frame for two sources (W0149+2350 and WISE J181417.29+341224.8, hereafter W1814+3412). The 1.3 mm continuum images have a resolution of 1''-2'' and are consistent with single point sources. We estimate the masses of cold dust are 2.0 × 10{sup 8} M {sub ☉} for W0149+2350 and 3.9 × 10{sup 8} M {sub ☉} for W2238+2653, comparable to cold dust masses of luminous quasars. We obtain 2σ upper limits to the molecular gas masses traced by CO, which are 3.3 × 10{sup 10} M {sub ☉} and 2.3 × 10{sup 10} M {sub ☉} for W0149+2350 and W1814+3412, respectively. We also present high-resolution, near-IR imaging with the WFC3 on the Hubble Space Telescope for W0149+2653 and with NIRC2 on Keck for W2238+2653. The near-IR images show morphological structure dominated by a single, centrally condensed source with effective radius less than 4 kpc. No signs of gravitational lensing are evident.

  11. Observations and modeling of the dust emission from the H2-bright galaxy-wide shock in Stephan's Quintet

    NASA Astrophysics Data System (ADS)

    Guillard, P.; Boulanger, F.; Cluver, M. E.; Appleton, P. N.; Pineau Des Forêts, G.; Ogle, P.

    2010-07-01

    Context. Spitzer Space Telescope observations have detected powerful mid-infrared (mid-IR) H2 rotational line emission from the X-ray emitting large-scale shock (~15 × 35 kpc2) associated with a galaxy collision in Stephan's Quintet (SQ). Because H2 forms on dust grains, the presence of H2 is physically linked to the survival of dust, and we expect some dust emission to originate in the molecular gas. Aims: To test this interpretation, IR observations and dust modeling are used to identify and characterize the thermal dust emission from the shocked molecular gas. Methods: The spatial distribution of the IR emission allows us to isolate the faint PAH and dust continuum emission associated with the molecular gas in the SQ shock. We model the spectral energy distribution (SED) of this emission, and fit it to Spitzer observations. The radiation field is determined with GALEX UV, HST V-band, and ground-based near-IR observations. We consider two limiting cases for the structure of the H2 gas: it is either diffuse and penetrated by UV radiation, or fragmented into clouds that are optically thick to UV. Results: Faint PAH and dust continuum emission are detected in the SQ shock, outside star-forming regions. The 12/24 μm flux ratio in the shock is remarkably close to that of the diffuse Galactic interstellar medium, leading to a Galactic PAH/VSG abundance ratio. However, the properties of the shock inferred from the PAH emission spectrum differ from those of the Galaxy, which may be indicative of an enhanced fraction of large and neutrals PAHs. In both models (diffuse or clumpy H2 gas), the IR SED is consistent with the expected emission from dust associated with the warm (> 150 K) H2 gas, heated by a UV radiation field of intensity comparable to that of the solar neighborhood. This is in agreement with GALEX UV observations that show that the intensity of the radiation field in the shock is GUV = 1.4±0.2 [Habing units]. Conclusions: The presence of PAHs and dust

  12. Modelling galaxy spectra in presence of interstellar dust - II. From the ultraviolet to the far-infrared

    NASA Astrophysics Data System (ADS)

    Piovan, Lorenzo; Tantalo, Rosaria; Chiosi, Cesare

    2006-08-01

    In this paper, we present spectrophotometric models for galaxies of different morphological type whose spectral energy distributions (SEDs) take into account the effect of dust in absorbing ultraviolet-optical (UV-optical) light and re-emitting it in the infrared. The models contain three main components: (i) the diffuse interstellar medium (ISM) composed of gas and dust, (ii) the large complexes of molecular clouds (MCs) in which new stars are formed and (iii) the stars of any age and chemical composition. The galaxy models stand on a robust model of chemical evolution that assuming a suitable prescription for gas infall, initial mass function, star formation rate and stellar ejecta provides the total amounts of gas and stars present at any age together with their chemical history. The chemical models are tailored in such a way to match the gross properties of galaxies of different morphological type. In order to describe the interaction between stars and ISM in building up the total SED of a galaxy, one has to know the spatial distribution of gas and stars. This is made adopting a simple geometrical model for each type of galaxy. The total gas and star mass provided by the chemical model are distributed over the whole volume by means of suitable density profiles, one for each component and depending on the galaxy type (spheroidal, disc and disc plus bulge). The galaxy is then split in suitable volume elements to each of which the appropriate amounts of stars, MCs and ISM are assigned. Each elemental volume bin is at the same time source of radiation from the stars inside and absorber and emitter of radiation from and to all other volume bins and the ISM in between. They are the elemental seeds to calculate the total SED. Using the results for the properties of the ISM and the single stellar populations presented by Piovan et al. we derive the SEDs of galaxies of different morphological type. First, the technical details of the method are described and the basic

  13. The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A Simple Hierarchical Bayesian Model

    NASA Astrophysics Data System (ADS)

    Mandel, Kaisey S.; Scolnic, Daniel M.; Shariff, Hikmatali; Foley, Ryan J.; Kirshner, Robert P.

    2017-06-01

    Conventional Type Ia supernova (SN Ia) cosmology analyses currently use a simplistic linear regression of magnitude versus color and light curve shape, which does not model intrinsic SN Ia variations and host galaxy dust as physically distinct effects, resulting in low color-magnitude slopes. We construct a probabilistic generative model for the dusty distribution of extinguished absolute magnitudes and apparent colors as the convolution of an intrinsic SN Ia color-magnitude distribution and a host galaxy dust reddening-extinction distribution. If the intrinsic color-magnitude (M B versus B - V) slope {β }{int} differs from the host galaxy dust law R B , this convolution results in a specific curve of mean extinguished absolute magnitude versus apparent color. The derivative of this curve smoothly transitions from {β }{int} in the blue tail to R B in the red tail of the apparent color distribution. The conventional linear fit approximates this effective curve near the average apparent color, resulting in an apparent slope {β }{app} between {β }{int} and R B . We incorporate these effects into a hierarchical Bayesian statistical model for SN Ia light curve measurements, and analyze a data set of SALT2 optical light curve fits of 248 nearby SNe Ia at z< 0.10. The conventional linear fit gives {β }{app}≈ 3. Our model finds {β }{int}=2.3+/- 0.3 and a distinct dust law of {R}B=3.8+/- 0.3, consistent with the average for Milky Way dust, while correcting a systematic distance bias of ˜0.10 mag in the tails of the apparent color distribution. Finally, we extend our model to examine the SN Ia luminosity-host mass dependence in terms of intrinsic and dust components.

  14. The selective effect of environment on the atomic and molecular gas-to-dust ratio of nearby galaxies in the Herschel Reference Survey

    NASA Astrophysics Data System (ADS)

    Cortese, L.; Bekki, K.; Boselli, A.; Catinella, B.; Ciesla, L.; Hughes, T. M.; Baes, M.; Bendo, G. J.; Boquien, M.; de Looze, I.; Smith, M. W. L.; Spinoglio, L.; Viaene, S.

    2016-07-01

    We combine dust, atomic (H I) and molecular (H2) hydrogen mass measurements for 176 galaxies in the Herschel Reference Survey to investigate the effect of environment on the gas-to-dust mass (Mgas/Mdust) ratio of nearby galaxies. We find that, at fixed stellar mass, the average Mgas/Mdust ratio varies by no more than a factor of ˜2 when moving from field to cluster galaxies, with Virgo galaxies being slightly more dust rich (per unit of gas) than isolated systems. Remarkably, once the molecular and atomic hydrogen phases are investigated separately, we find that H I-deficient galaxies have at the same time lower M_{H I}/M_dust ratio but higher M_H2/M_dust ratio than H I-normal systems. In other words, they are poorer in atomic but richer in molecular hydrogen if normalized to their dust content. By comparing our findings with the predictions of theoretical models, we show that the opposite behaviour observed in the M_{H I}/M_dust and M_H2/M_dust ratios is fully consistent with outside-in stripping of the interstellar medium (ISM), and is simply a consequence of the different distribution of dust, H I and H2 across the disc. Our results demonstrate that the small environmental variations in the total Mgas/Mdust ratio, as well as in the gas-phase metallicity, do not automatically imply that environmental mechanisms are not able to affect the dust and metal content of the ISM in galaxies.

  15. Life in the fast lane: The dark-matter distribution in the most massive galaxy clusters in the Universe at z>0.5

    NASA Astrophysics Data System (ADS)

    Ebeling, Harald

    2003-07-01

    We propose two-filter ACS observations of a complete sample of 12 very X-ray luminous galaxy clusters at 0.50.5. HST's unique capabilities will allow us to: 1} measure accurately the clusters' dark matter distribution on scales from tens to more than 500/h_50 kpc from observations of strong and weak gravitational lensing, 2} use galaxy-galaxy lensing to measure the shape, extent, and mass content of the dark-matter halos of both cluster and field galaxies, and 3} study the color morphology of mergers and the star formation history of galaxies in a high-density environment. The proposed observations are complemented by Chandra observations of all our targets {all 12 awarded, 11 executed to date} which provide independent constraints on the dark matter and gas distribution in the cluster cores, as well a by extensive groundbased observations of weak lensing on yet larger scales, galaxy dynamics, and the SZ effect.

  16. Life in the fast lane: The dark-matter distribution in the most massive galaxy clusters in the Universe at z>0.5

    NASA Astrophysics Data System (ADS)

    Ebeling, Harald

    2004-07-01

    We propose two-filter ACS observations of a complete sample of 12 very X-ray luminous galaxy clusters at 0.50.5. HST's unique capabilities will allow us to: 1} measure accurately the clusters' dark matter distribution on scales from tens to more than 500/h_50 kpc from observations of strong and weak gravitational lensing, 2} use galaxy-galaxy lensing to measure the shape, extent, and mass content of the dark-matter halos of both cluster and field galaxies, and 3} study the color morphology of mergers and the star formation history of galaxies in a high-density environment. The proposed observations are complemented by Chandra observations of all our targets {all 12 awarded, 11 executed to date} which provide independent constraints on the dark matter and gas distribution in the cluster cores, as well a by extensive groundbased observations of weak lensing on yet larger scales, galaxy dynamics, and the SZ effect.

  17. The identification of dust heating mechanisms in nearby galaxies using Herschel 160/250 and 250/350 μm surface brightness ratios

    NASA Astrophysics Data System (ADS)

    Bendo, G. J.; Baes, M.; Bianchi, S.; Boquien, M.; Boselli, A.; Cooray, A.; Cortese, L.; De Looze, I.; di Serego Alighieri, S.; Fritz, J.; Gentile, G.; Hughes, T. M.; Lu, N.; Pappalardo, C.; Smith, M. W. L.; Spinoglio, L.; Viaene, S.; Vlahakis, C.

    2015-03-01

    We examined variations in the 160/250 and 250/350 μm surface brightness ratios within 24 nearby (<30 Mpc) face-on spiral galaxies observed with the Herschel Space Observatory to identify the heating mechanisms for dust emitting at these wavelengths. The analysis consisted of both qualitative and quantitative comparisons of the 160/250 and 250/350 μm ratios to Hα and 24 μm emission, which trace the light from star-forming regions, and 3.6 μm emission, which traces the light from the older stellar populations of the galaxies. We find broad variations in the heating mechanisms for the dust. In one subset of galaxies, we found evidence that emission at ≤160 μm (and in rare cases potentially at ≤350 μm) originates from dust heated by star-forming regions. In another subset, we found that the emission at ≥250 μm (and sometimes at ≥160 μm) originates from dust heated by the older stellar population. In the rest of the sample, either the results are indeterminate or both of these stellar populations may contribute equally to the global dust heating. The observed variations in dust heating mechanisms do not necessarily match what has been predicted by dust emission and radiative transfer models, which could lead to overestimated dust temperatures, underestimated dust masses, false detections of variability in dust emissivity, and inaccurate star formation rate measurements.

  18. The Herschel Virgo Cluster Survey. IX. Dust-to-gas mass ratio and metallicity gradients in four Virgo spiral galaxies

    NASA Astrophysics Data System (ADS)

    Magrini, L.; Bianchi, S.; Corbelli, E.; Cortese, L.; Hunt, L.; Smith, M.; Vlahakis, C.; Davies, J.; Bendo, G. J.; Baes, M.; Boselli, A.; Clemens, M.; Casasola, V.; De Looze, I.; Fritz, J.; Giovanardi, C.; Grossi, M.; Hughes, T.; Madden, S.; Pappalardo, C.; Pohlen, M.; di Serego Alighieri, S.; Verstappen, J.

    2011-11-01

    Context. Using Herschel data from the open time key project the Herschel Virgo Cluster Survey (HeViCS), we investigated the relationship between the metallicity gradients expressed by metal abundances in the gas phase as traced by the chemical composition of HII regions, and in the solid phase, as traced by the dust-to-gas mass ratio. Aims: We derived the radial gradient of the dust-to-gas mass ratio for all galaxies observed by HeViCS whose metallicity gradients are available in the literature. They are all late type Sbc galaxies, namely NGC 4254, NGC 4303, NGC 4321, and NGC 4501. Methods: We fitted PACS and SPIRE observations with a single-temperature modified blackbody, inferred the dust mass, and calculated two dimensional maps of the dust-to-gas mass ratio, with the total mass of gas from available HI and CO maps. HI moment-1 maps were used to derive the geometric parameters of the galaxies and extract the radial profiles. We examined different dependencies on metallicity of the CO-to-H2 conversion factor (XCO), used to transform the 12CO observations into the amount of molecular hydrogen. Results: We found that in these galaxies the dust-to-gas mass ratio radial profile is extremely sensitive to choice of the XCO value, since the molecular gas is the dominant component in the inner parts. We found that for three galaxies of our sample, namely NGC 4254, NGC 4321, and NGC 4501, the slopes of the oxygen and of the dust-to-gas radial gradients agree up to ~0.6-0.7 R25 using XCO values in the range 1/3-1/2 Galactic XCO. For NGC 4303 a lower value of XCO ~ 0.1 × 1020 is necessary. Conclusions: We suggest that such low XCO values might be due to a metallicity dependence of XCO (from close to linear for NGC 4254, NGC 4321, and NGC 4501 to superlinear for NGC 4303), especially in the radial regions RG < 0.6-0.7 R25 where the molecular gas dominates. On the other hand, the outer regions, where the atomic gas component is dominant, are less affected by the choice of

  19. Astronomer's new guide to the galaxy: largest map of cold dust revealed

    NASA Astrophysics Data System (ADS)

    2009-07-01

    Astronomers have unveiled an unprecedented new atlas of the inner regions of the Milky Way, our home galaxy, peppered with thousands of previously undiscovered dense knots of cold cosmic dust -- the potential birthplaces of new stars. Made using observations from the APEX telescope in Chile, this survey is the largest map of cold dust so far, and will prove an invaluable map for observations made with the forthcoming ALMA telescope, as well as the recently launched ESA Herschel space telescope. ESO PR Photo 24a/09 View of the Galactic Plane from the ATLASGAL survey (annotated and in five sections) ESO PR Photo 24b/09 View of the Galactic Plane from the ATLASGAL survey (annotated) ESO PR Photo 24c/09 View of the Galactic Plane from the ATLASGAL survey (in five sections) ESO PR Photo 24d/09 View of the Galactic Plane from the ATLASGAL survey ESO PR Photo 24e/09 The Galactic Centre and Sagittarius B2 ESO PR Photo 24f/09 The NGC 6357 and NGC 6334 nebulae ESO PR Photo 24g/09 The RCW120 nebula ESO PR Video 24a/09 Annotated pan as seen by the ATLASGAL survey This new guide for astronomers, known as the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) shows the Milky Way in submillimetre-wavelength light (between infrared light and radio waves [1]). Images of the cosmos at these wavelengths are vital for studying the birthplaces of new stars and the structure of the crowded galactic core. "ATLASGAL gives us a new look at the Milky Way. Not only will it help us investigate how massive stars form, but it will also give us an overview of the larger-scale structure of our galaxy", said Frederic Schuller from the Max Planck Institute for Radio Astronomy, leader of the ATLASGAL team. The area of the new submillimetre map is approximately 95 square degrees, covering a very long and narrow strip along the galactic plane two degrees wide (four times the width of the full Moon) and over 40 degrees long. The 16 000 pixel-long map was made with the LABOCA submillimetre

  20. Dust and star formation properties of a complete sample of local galaxies drawn from the Planck Early Release Compact Source Catalogue

    NASA Astrophysics Data System (ADS)

    Clemens, M. S.; Negrello, M.; De Zotti, G.; Gonzalez-Nuevo, J.; Bonavera, L.; Cosco, G.; Guarese, G.; Boaretto, L.; Salucci, P.; Baccigalupi, C.; Clements, D. L.; Danese, L.; Lapi, A.; Mandolesi, N.; Partridge, R. B.; Perrotta, F.; Serjeant, S.; Scott, D.; Toffolatti, L.

    2013-07-01

    We combine Planck High Frequency Instrument data at 857, 545, 353 and 217 GHz with data from Wide-field Infrared Survey Explorer (WISE), Spitzer, IRAS and Herschel to investigate the properties of a well-defined, flux-limited sample of local star-forming galaxies. A 545 GHz flux density limit was chosen so that the sample is 80 per cent complete at this frequency, and the resulting sample contains a total of 234 local, star-forming galaxies. We investigate the dust emission and star formation properties of the sample via various models and calculate the local dust mass function. Although single-component-modified blackbodies fit the dust emission longward of 80 μm very well, with a median β = 1.83, the known degeneracy between dust temperature and β also means that the spectral energy distributions are very well described by a dust component with dust emissivity index fixed at β = 2 and temperature in the range 10-25 K. Although a second, warmer dust component is required to fit shorter wavelength data, and contributes approximately a third of the total infrared emission, its mass is negligible. No evidence is found for a very cold (6-10 K) dust component. The temperature of the cold dust component is strongly influenced by the ratio of the star formation rate to the total dust mass. This implies, contrary to what is often assumed, that a significant fraction of even the emission from ˜20 K dust is powered by ongoing star formation, whether or not the dust itself is associated with star-forming clouds or `cirrus'. There is statistical evidence of a free-free contribution to the 217 GHz flux densities of ≲20 per cent. We find a median dust-to-stellar mass ratio of 0.0046; and that this ratio is anticorrelated with galaxy mass. There is good correlation between dust mass and atomic gas mass (median Md/MHI = 0.022), suggesting that galaxies that have more dust (higher values of Md/M*) have more interstellar medium in general. Our derived dust mass function

  1. The Two-faced Whirlpool Galaxy

    NASA Image and Video Library

    2017-09-27

    NASA image release January 13, 2011 These images by NASA's Hubble Space Telescope show off two dramatically different face-on views of the spiral galaxy M51, dubbed the Whirlpool Galaxy. The image here, taken in visible light, highlights the attributes of a typical spiral galaxy, including graceful, curving arms, pink star-forming regions, and brilliant blue strands of star clusters. In the image above, most of the starlight has been removed, revealing the Whirlpool's skeletal dust structure, as seen in near-infrared light. This new image is the sharpest view of the dense dust in M51. The narrow lanes of dust revealed by Hubble reflect the galaxy's moniker, the Whirlpool Galaxy, as if they were swirling toward the galaxy's core. To map the galaxy's dust structure, researchers collected the galaxy's starlight by combining images taken in visible and near-infrared light. The visible-light image captured only some of the light; the rest was obscured by dust. The near-infrared view, however, revealed more starlight because near-infrared light penetrates dust. The researchers then subtracted the total amount of starlight from both images to see the galaxy's dust structure. The red color in the near-infrared image traces the dust, which is punctuated by hundreds of tiny clumps of stars, each about 65 light-years wide. These stars have never been seen before. The star clusters cannot be seen in visible light because dense dust enshrouds them. The image reveals details as small as 35 light-years across. Astronomers expected to see large dust clouds, ranging from about 100 light-years to more than 300 light-years wide. Instead, most of the dust is tied up in smooth and diffuse dust lanes. An encounter with another galaxy may have prevented giant clouds from forming. Probing a galaxy's dust structure serves as an important diagnostic tool for astronomers, providing invaluable information on how the gas and dust collapse to form stars. Although Hubble is providing incisive

  2. The Two-faced Whirlpool Galaxy

    NASA Image and Video Library

    2017-09-27

    NASA image release January 13, 2011 These images by NASA's Hubble Space Telescope show off two dramatically different face-on views of the spiral galaxy M51, dubbed the Whirlpool Galaxy. The image above, taken in visible light, highlights the attributes of a typical spiral galaxy, including graceful, curving arms, pink star-forming regions, and brilliant blue strands of star clusters. In the image here, most of the starlight has been removed, revealing the Whirlpool's skeletal dust structure, as seen in near-infrared light. This new image is the sharpest view of the dense dust in M51. The narrow lanes of dust revealed by Hubble reflect the galaxy's moniker, the Whirlpool Galaxy, as if they were swirling toward the galaxy's core. To map the galaxy's dust structure, researchers collected the galaxy's starlight by combining images taken in visible and near-infrared light. The visible-light image captured only some of the light; the rest was obscured by dust. The near-infrared view, however, revealed more starlight because near-infrared light penetrates dust. The researchers then subtracted the total amount of starlight from both images to see the galaxy's dust structure. The red color in the near-infrared image traces the dust, which is punctuated by hundreds of tiny clumps of stars, each about 65 light-years wide. These stars have never been seen before. The star clusters cannot be seen in visible light because dense dust enshrouds them. The image reveals details as small as 35 light-years across. Astronomers expected to see large dust clouds, ranging from about 100 light-years to more than 300 light-years wide. Instead, most of the dust is tied up in smooth and diffuse dust lanes. An encounter with another galaxy may have prevented giant clouds from forming. Probing a galaxy's dust structure serves as an important diagnostic tool for astronomers, providing invaluable information on how the gas and dust collapse to form stars. Although Hubble is providing incisive

  3. SIMULTANEOUS MODELING OF THE STELLAR AND DUST EMISSION IN DISTANT GALAXIES: IMPLICATIONS FOR STAR FORMATION RATE MEASUREMENTS

    SciTech Connect

    Utomo, Dyas; Kriek, Mariska; Labbé, Ivo; Fumagalli, Mattia; Conroy, Charlie

    2014-03-10

    We have used near-ultraviolet (NUV) to mid-infrared (MIR) composite spectral energy distributions (SEDs) to simultaneously model the attenuated stellar and dust emission of 0.5 ≲ z ≲ 2.0 galaxies. These composite SEDs were previously constructed from the photometric catalogs of the NEWFIRM Medium-Band Survey by stacking the observed photometry of galaxies that have similar rest-frame NUV-to-NIR SEDs. In this work, we include a stacked MIPS 24 μm measurement for each SED type to extend the SEDs to rest-frame MIR wavelengths. Consistent with previous studies, the observed MIR emission for most SED types is higher than expected from only the attenuated stellar emission. We fit the NUV-to-MIR composite SEDs with the Flexible Stellar Population Synthesis (FSPS) models, which include both stellar and dust emission. We compare the best-fit star formation rates (SFRs) to the SFRs based on simple UV+IR estimators. Interestingly, the UV and IR luminosities overestimate SFRs—compared to the model SFRs—by more than ∼1 dex for quiescent galaxies, while for the highest star-forming galaxies in our sample the two SFRs are broadly consistent. The difference in specific SFRs also shows a gradually increasing trend with declining specific SFR, implying that quiescent galaxies have even lower specific SFRs than previously found. Contributions from evolved stellar populations to both the UV and the MIR SEDs most likely explain the discrepancy. Based on this work, we conclude that SFRs should be determined from modeling the attenuated stellar and dust emission simultaneously, instead of employing simple UV+IR-based SFR estimators.

  4. Early science with the Large Millimeter Telescope: dust constraints in a z ˜ 9.6 galaxy

    NASA Astrophysics Data System (ADS)

    Zavala, J. A.; Michałowski, M. J.; Aretxaga, I.; Wilson, G. W.; Hughes, D. H.; Montaña, A.; Dunlop, J. S.; Pope, A.; Sánchez-Argüelles, D.; Yun, M. S.; Zeballos, M.

    2015-10-01

    Recent observations with the GISMO (Goddard-IRAM Superconducting 2 Millimeter Observer) 2 mm camera revealed a detection 8 arcsec away from the lensed galaxy MACS1149-JD1 at z = 9.6. Within the 17.5 arcsec FWHM GISMO beam, this detection is consistent with the position of the high-redshift galaxy and therefore, if confirmed, this object could be claimed to be the youngest galaxy producing significant quantities of dust. We present higher resolution (8.5 arcsec) observations of this system taken with the AzTEC 1.1 mm camera mounted on the Large Millimeter Telescope Alfonso Serrano. Dust continuum emission at the position of MACS1149-JD1 is not detected with an r.m.s. of 0.17 mJy/beam. However, we find a detection ˜11 arcsec away from MACS1149-JD1, still within the GISMO beam which is consistent with an association to the GISMO source. Combining the AzTEC and GISMO photometry, together with Herschel ancillary data, we derive a zphot = 0.7-1.6 for the dusty galaxy. We conclude therefore that the GISMO and AzTEC detections are not associated with MACS1149-JD1. From the non-detection of MACS1149-JD1 we derive the following (3σ) upper limits corrected for gravitational lensing magnification and for cosmic microwave background effects: dust mass <1.6 × 107 M⊙, IR luminosity <8 × 1010 L⊙, star formation rate <14 M⊙ yr-1, and UV attenuation <2.7 mag. These limits are comparable to those derived for other high-redshift galaxies from deep Atacama Large Millimeter/submillimeter Array observations.

  5. Gravitationally Lensed CO and Dust at High Redshift: New LMT/GTM Images and Spectra of Sub-Millimeter Galaxies

    NASA Astrophysics Data System (ADS)

    Lowenthal, J. D.; Harrington, K.; Berman, D.; Yun, M.; Cybulski, R.; Wilson, G. W.; Aretxaga, I.; Chavez, M.; de La Luz, V.; Erickson, N.; Ferrusca, D.; Gallup, A.; Hughes, D.; Montaña, A.; Narayanan, G.; Sánchez-Argüelles, D.; Schloerb, F. P.; Souccar, K.; Terlevich, E.; Terlevich, R.; Zeballos, M.; Zavala, J. A.

    2017-03-01

    We have assembled a new sample of some of the most FIR-luminous galaxies in the Universe and have imaged them in 1.1 mm dust emission and measured their redshifts 1 < z < 4 via CO emission lines using the 32-m Large Millimeter Telescope / Gran Telescopio Milimétrico (LMT/GTM). Our sample of 31 submm galaxies (SMGs), culled from the Planck and Herschel all-sky surveys, includes 14 of the 21 most luminous galaxies known, with LFIR > 1014 L ⊙ and SFR > 104M⊙/yr. These extreme inferred luminosities - and multiple / extended 1.1 mm images - imply that most or all are strongly gravitationally lensed, with typical magnification μ ~ 10 × . The gravitational lensing provides two significant benefits: (1) it boosts the S/N, and (2) it allows investigation of star formation and gas processes on sub-kpc scales.

  6. The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A Simple Hierarchical Bayesian Model

    NASA Astrophysics Data System (ADS)

    Mandel, Kaisey; Scolnic, Daniel; Shariff, Hikmatali; Foley, Ryan; Kirshner, Robert

    2017-01-01

    Inferring peak optical absolute magnitudes of Type Ia supernovae (SN Ia) from distance-independent measures such as their light curve shapes and colors underpins the evidence for cosmic acceleration. SN Ia with broader, slower declining optical light curves are more luminous (“broader-brighter”) and those with redder colors are dimmer. But the “redder-dimmer” color-luminosity relation widely used in cosmological SN Ia analyses confounds its two separate physical origins. An intrinsic correlation arises from the physics of exploding white dwarfs, while interstellar dust in the host galaxy also makes SN Ia appear dimmer and redder. Conventional SN Ia cosmology analyses currently use a simplistic linear regression of magnitude versus color and light curve shape, which does not model intrinsic SN Ia variations and host galaxy dust as physically distinct effects, resulting in low color-magnitude slopes. We construct a probabilistic generative model for the dusty distribution of extinguished absolute magnitudes and apparent colors as the convolution of an intrinsic SN Ia color-magnitude distribution and a host galaxy dust reddening-extinction distribution. If the intrinsic color-magnitude (MB vs. B-V) slope βint differs from the host galaxy dust law RB, this convolution results in a specific curve of mean extinguished absolute magnitude vs. apparent color. The derivative of this curve smoothly transitions from βint in the blue tail to RB in the red tail of the apparent color distribution. The conventional linear fit approximates this effective curve near the average apparent color, resulting in an apparent slope βapp between βint and RB. We incorporate these effects into a hierarchical Bayesian statistical model for SN Ia light curve measurements, and analyze a dataset of SALT2 optical light curve fits of 277 nearby SN Ia at z < 0.10. The conventional linear fit obtains βapp ≈ 3. Our model finds a βint = 2.2 ± 0.3 and a distinct dust law of RB = 3.7 ± 0

  7. Stars, dust, and the growth of ultraviolet-selected sub-L* galaxies at redshift z˜ 2

    NASA Astrophysics Data System (ADS)

    Sawicki, Marcin

    2012-04-01

    This work concerns the physical properties of very faint (?= 28 AB mag; Mstars,lim˜ 108 M⊙), ultraviolet-selected (UV-selected) sub-L* BX galaxies at z˜ 2.3. Stellar masses, dust content and dust-corrected star formation rates are constrained using broad-band spectral energy distribution fitting, resulting in a number of insights into the nature of these low-mass systems. First, a correlation between rest-frame UV luminosity and galaxy stellar mass appears to exist in BX galaxies and its presence suggests that many sub-L* galaxies at this redshift may have approximately constant, rather than highly variable, star formation histories. A nearly-linear relation between stellar mass and star formation rate is also found, hinting that the rate at which a sub-L* BX galaxy forms its stars is directly related to the mass of stars that it has already formed. A possible explanation for this phenomenon lies in a scenario in which new gas that falls on to the galaxy's host halo along with accreting dark matter is the main source of fuel for ongoing star formation. The instantaneous efficiency of star formation is low in this scenario, of the order of 1 per cent. Turning to bulk quantities, it is found that the low-mass end of the stellar mass function at z˜ 2.3 is steeper than expected from extrapolations of shallower surveys, resulting in a stellar mass density at z˜ 2.3 that is ˜25 per cent of the present-day value; this value is ˜1.5-2 times higher than that given by extrapolations of most of the shallower surveys, suggesting that the build-up of stellar mass in the Universe has proceeded somewhat more rapidly than previously thought. With spectral energy distribution fitting results in hand, an update to the Keck Deep Fields z˜ 2 UV luminosity function finds a steeper faint-end slope than previously reported, α=- 1.47, though this is not as steep as that found by Reddy & Steidel. Finally, it is also found that sub-L* galaxies at z˜ 2 carry very small amounts of

  8. CAN DUST EMISSION BE USED TO ESTIMATE THE MASS OF THE INTERSTELLAR MEDIUM IN GALAXIES-A PILOT PROJECT WITH THE HERSCHEL REFERENCE SURVEY

    SciTech Connect

    Eales, Stephen; Smith, Matthew W. L.; Auld, Robbie; Davies, Jon; Gear, Walter; Gomez, Haley; Baes, Maarten; De Looze, Ilse; Gentile, Gianfranco; Fritz, Jacopo; Bendo, George J.; Bianchi, Simone; Boselli, Alessandro; Ciesla, Laure; Clements, David; Cooray, Asantha; Cortese, Luca; Galametz, Maud; Hughes, Tom; Madden, Suzanne [Laboratoire AIM, CEA and others

    2012-12-20

    The standard method for estimating the mass of the interstellar medium (ISM) in a galaxy is to use the 21 cm line to trace the atomic gas and the CO 1-0 line to trace the molecular gas. In this paper, we investigate the alternative technique of using the continuum dust emission to estimate the mass of gas in all phases of the ISM. Using Herschel observations of 10 galaxies from the Herschel Reference Survey and the Herschel Virgo Cluster Survey, we show that the emission detected by Herschel is mostly from dust that has a temperature and emissivity index similar to that of dust in the local ISM in our galaxy, with the temperature generally increasing toward the center of each galaxy. We calibrate the dust method using the CO and 21 cm observations to provide an independent estimate of the mass of hydrogen in each galaxy, solving the problem of the uncertain ''X-factor'' for the CO observations by minimizing the dispersion in the ratio of the masses estimated using the two methods. With the calibration for the dust method and the estimate of the X-factor produced in this way, the dispersion in the ratio of the two gas masses is 25%. The calibration we obtain for the dust method is similar to those obtained from Herschel observations of M31 and from Planck observations of the Milky Way. We discuss the practical problems in using this method.

  9. The Herschel Exploitation of Local Galaxy Andromeda (HELGA). IV. Dust scaling relations at sub-kpc resolution

    NASA Astrophysics Data System (ADS)

    Viaene, S.; Fritz, J.; Baes, M.; Bendo, G. J.; Blommaert, J. A. D. L.; Boquien, M.; Boselli, A.; Ciesla, L.; Cortese, L.; De Looze, I.; Gear, W. K.; Gentile, G.; Hughes, T. M.; Jarrett, T.; Karczewski, O. Ł.; Smith, M. W. L.; Spinoglio, L.; Tamm, A.; Tempel, E.; Thilker, D.; Verstappen, J.

    2014-07-01

    Context. Dust and stars play a complex game of interactions in the interstellar medium and around young stars. The imprints of these processes are visible in scaling relations between stellar characteristics, star formation parameters, and dust properties. Aims: In the present work, we aim to examine dust scaling relations on a sub-kpc resolution in the Andromeda galaxy (M 31). The goal is to investigate the properties of M 31 on both a global and local scale and compare them to other galaxies of the local universe. Methods: New Herschel observations are combined with available data from GALEX, SDSS, WISE, and Spitzer to construct a dataset covering UV to submm wavelengths. All images were brought to the beam size and pixel grid of the SPIRE 500 μm frame. This divides M 31 in 22 437 pixels of 36 arcseconds in size on the sky, corresponding to physical regions of 137 × 608 pc in the galaxy's disk. A panchromatic spectral energy distribution was modelled for each pixel and maps of the physical quantities were constructed. Several scaling relations were investigated, focussing on the interactions of dust with starlight. Results: We find, on a sub-kpc scale, strong correlations between Mdust/M⋆ and NUV-r, and between Mdust/M⋆ and μ⋆ (the stellar mass surface density). Striking similarities with corresponding relations based on integrated galaxies are found. We decompose M 31 in four macro-regions based on their far-infrared morphology; the bulge, inner disk, star forming ring, and the outer disk region. In the scaling relations, all regions closely follow the galaxy-scale average trends and behave like galaxies of different morphological types. The specific star formation characteristics we derive for these macro-regions give strong hints of an inside-out formation of the bulge-disk geometry, as well as an internal downsizing process. Within each macro-region, however, a great diversity in individual micro-regions is found, regardless of the properties of the

  10. DUSTiNGS. III. Distribution of Intermediate-age and Old Stellar Populations in Disks and Outer Extremities of Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    McQuinn, Kristen B.; Boyer, Martha; DUSTiNGS Team

    2017-06-01

    As part of the DUST in Nearby Galaxies with Spitzer (DUSTiNGS) survey, we have traced the spatial distributions of intermediate-age and old stars in nine dwarf galaxies in the distant parts of the Local Group. We find intermediate age stars are well mixed with the older populations and extend to large radii, indicating that chemical enrichment from these dust-producing stars may occur in the outer regions of galaxies with some frequency. Theories of structure formation in dwarf galaxies must account for the lack of radial gradients in intermediate-age populations and the presence of these stars in the outer extremities of dwarfs. We also identify the tip of the red giant branch (TRGB) in Spitzer IRAC 3.6 μm photometry. Unlike the constant TRGB in the I band, at 3.6 μm, the TRGB magnitude varies by ˜0.7 mag and is not a metallicity independent distance indicator.

  11. Early type galaxies, i.e. ellipticals and lenticulars, are generally considered to be largely devoid of cool gas and associated dust

    NASA Astrophysics Data System (ADS)

    Stadler, Joel Travis; Kotulla, Ralf C.; Gallagher, John S.

    2017-01-01

    In this REU project we employ the unsharp masking technique to study a large sample of relatively bright and extended early type galaxies with imaging from SDSS. While most galaxies behave as expected, showing only a smooth, feature-less light distribution, we find a small but significant population of, in particular, S0-type galaxies with detectable dust features, such as dust disks, rings, or clumps. Based on a cross-match of our dusty early-type galaxies with the catalog of infrared-bright galaxies detected by IRAS reveals that all galaxies in which we find dust are also detected by IRAS, allowing us to better describe the geometry and distribution of the IR-emitting dust to improve modeling of their UV-optical-IR spectral energy distributions. We also found a small subset of galaxies showing evidence for tidal shells and debris, indicating a recent interaction. Lastly, the methods developed as part of this project can easily be adopted for similar and/or larger studies, providing a lasting benefit beyond the science results of this project. This work was supported by the National Science Foundation's REU program through NSF award AST-1560016.

  12. Dust Properties of C ii Detected z ˜ 5.5 Galaxies: New HST/WFC3 Near-IR Observations

    NASA Astrophysics Data System (ADS)

    Barisic, I.; Faisst, A. L.; Capak, P. L.; Pavesi, R.; Riechers, D. A.; Scoville, N. Z.; Cooke, K.; Kartaltepe, J. S.; Casey, C. M.; Smolcic, V.

    2017-08-01

    We examine the rest-frame ultraviolet (UV) properties of 10 [C ii]λ158 μm-detected galaxies at z ˜ 5.5 in COSMOS using new Hubble Space Telescope/Wide Field Camera 3 near-infrared imaging. Together with pre-existing 158 μm continuum and [C ii] line measurements by the Atacama Large Millimeter/submillimeter Array, we study their dust attenuation properties on the IRX-β diagram, which connects the total dust emission (\\propto {IRX}={log}({L}{FIR}/{L}1600)) to the line-of-sight dust column (∝ β). We find systematically bluer UV continuum spectral slopes (β) compared to previous low-resolution ground-based measurements, which relieves some of the tension between models of dust attenuation and observations at high redshifts. While most of the galaxies are consistent with local starburst or Small Magellanic Cloud-like dust properties, we find galaxies with low IRX values and a large range in β that cannot be explained by models of a uniform dust distribution well mixed with stars. A stacking analysis of Keck/DEIMOS optical spectra indicates that these galaxies are metal-poor with young stellar populations that could significantly alter their spatial dust distribution.

  13. QUANTIFYING THE HEATING SOURCES FOR MID-INFRARED DUST EMISSIONS IN GALAXIES: THE CASE OF M 81

    SciTech Connect

    Lu, N.; Zhao, Y.; Bendo, G. J.; Boselli, A.; Baes, M.; De Looze, I.; Wu, H.; Lam, M. I.; Madden, S. C.; Rémy-Ruyer, A.; Wilson, C. D.; Galametz, M.; Cooray, A.; Spinoglio, L.

    2014-12-20

    With the newly available photometric images at 250 and 500 μm from the Herschel Space Observatory, we study quantitative correlations over a sub-kiloparsec scale among three distinct emission components in the interstellar medium of the nearby spiral galaxy M 81 (NGC 3031): (1) I {sub 8} or I {sub 24}, the surface brightness of the mid-infrared emission observed in the Spitzer Space Telescope 8 or 24 μm band, with I {sub 8} and I {sub 24} being dominated by the emissions from polycyclic aromatic hydrocarbons (PAHs) and very small grains (VSGs) of dust, respectively; (2) I {sub 500}, that of the cold dust continuum emission in the Herschel Space Observatory 500 μm band, dominated by the emission from large dust grains heated by evolved stars; and (3) I {sub Hα}, a nominal surface brightness of the Hα line emission, from gas ionized by newly formed massive stars. The results from our correlation study, free from any assumption on or modeling of dust emissivity law or dust temperatures, present solid evidence for significant heating of PAHs and VSGs by evolved stars. In the case of M 81, about 67% (48%) of the 8 μm (24 μm ) emission derives its heating from evolved stars, with the remainder attributed to radiation heating associated with ionizing stars.

  14. K'-band observations of the evil eye galaxy: Are the optical and near-infrared dust albedos identical?

    NASA Technical Reports Server (NTRS)

    Witt, Adolf N.; Lindell, Rebecca S.; Block, David L.; Evans, Rhodri

    1994-01-01

    New measurements of the reduction of the V-band surface brightness across the prominent dust feature in the galaxy NGC 4826 are compared with corresponding increases in the V-K' color within the context of radiative transfer models invoking both absorption and scattering. The K'-band surface brightness is found to be higher than expected from standard dust models. We interpret the difference as resulting from a high effective dust albedo at K', with a likely value in excess of 0.8, provided the near-IR extinction curve in NGC 4826 is identical to the Galactic one. The high effective albedo may result from scattering by dust with a maximum grain size at least twice as large as assumed by standard models, a conclusion already indirectly hinted at by recent studies of dust star-forming regions and reflection nebulae. At least part of the high effective albedo at K' may result from near-IR nonequilibrium continuum emission attributable to very small grains.

  15. K'-band observations of the evil eye galaxy: Are the optical and near-infrared dust albedos identical?

    NASA Astrophysics Data System (ADS)

    Witt, Adolf N.; Lindell, Rebecca S.; Block, David L.; Evans, Rhodri

    1994-05-01

    New measurements of the reduction of the V-band surface brightness across the prominent dust feature in the galaxy NGC 4826 are compared with corresponding increases in the V-K' color within the context of radiative transfer models invoking both absorption and scattering. The K'-band surface brightness is found to be higher than expected from standard dust models. We interpret the difference as resulting from a high effective dust albedo at K', with a likely value in excess of 0.8, provided the near-IR extinction curve in NGC 4826 is identical to the Galactic one. The high effective albedo may result from scattering by dust with a maximum grain size at least twice as large as assumed by standard models, a conclusion already indirectly hinted at by recent studies of dust star-forming regions and reflection nebulae. At least part of the high effective albedo at K' may result from near-IR nonequilibrium continuum emission attributable to very small grains.

  16. Quantifying the Heating Sources for Mid-infrared Dust Emissions in Galaxies: The Case of M 81

    NASA Astrophysics Data System (ADS)

    Lu, N.; Bendo, G. J.; Boselli, A.; Baes, M.; Wu, H.; Madden, S. C.; De Looze, I.; Rémy-Ruyer, A.; Boquien, M.; Wilson, C. D.; Galametz, M.; Lam, M. I.; Cooray, A.; Spinoglio, L.; Zhao, Y.

    2014-12-01

    With the newly available photometric images at 250 and 500 μm from the Herschel Space Observatory, we study quantitative correlations over a sub-kiloparsec scale among three distinct emission components in the interstellar medium of the nearby spiral galaxy M 81 (NGC 3031): (1) I 8 or I 24, the surface brightness of the mid-infrared emission observed in the Spitzer Space Telescope 8 or 24 μm band, with I 8 and I 24 being dominated by the emissions from polycyclic aromatic hydrocarbons (PAHs) and very small grains (VSGs) of dust, respectively; (2) I 500, that of the cold dust continuum emission in the Herschel Space Observatory 500 μm band, dominated by the emission from large dust grains heated by evolved stars; and (3) I Hα, a nominal surface brightness of the Hα line emission, from gas ionized by newly formed massive stars. The results from our correlation study, free from any assumption on or modeling of dust emissivity law or dust temperatures, present solid evidence for significant heating of PAHs and VSGs by evolved stars. In the case of M 81, about 67% (48%) of the 8 μm (24 μm ) emission derives its heating from evolved stars, with the remainder attributed to radiation heating associated with ionizing stars. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  17. K'-band observations of the evil eye galaxy: Are the optical and near-infrared dust albedos identical?

    NASA Technical Reports Server (NTRS)

    Witt, Adolf N.; Lindell, Rebecca S.; Block, David L.; Evans, Rhodri

    1994-01-01

    New measurements of the reduction of the V-band surface brightness across the prominent dust feature in the galaxy NGC 4826 are compared with corresponding increases in the V-K' color within the context of radiative transfer models invoking both absorption and scattering. The K'-band surface brightness is found to be higher than expected from standard dust models. We interpret the difference as resulting from a high effective dust albedo at K', with a likely value in excess of 0.8, provided the near-IR extinction curve in NGC 4826 is identical to the Galactic one. The high effective albedo may result from scattering by dust with a maximum grain size at least twice as large as assumed by standard models, a conclusion already indirectly hinted at by recent studies of dust star-forming regions and reflection nebulae. At least part of the high effective albedo at K' may result from near-IR nonequilibrium continuum emission attributable to very small grains.

  18. Early Science with the Large Millimeter Telescope: observations of dust continuum and CO emission lines of cluster-lensed submillimetre galaxies at z=2.0-4.7

    NASA Astrophysics Data System (ADS)

    Zavala, J. A.; Yun, M. S.; Aretxaga, I.; Hughes, D. H.; Wilson, G. W.; Geach, J. E.; Egami, E.; Gurwell, M. A.; Wilner, D. J.; Smail, Ian; Blain, A. W.; Chapman, S. C.; Coppin, K. E. K.; Dessauges-Zavadsky, M.; Edge, A. C.; Montaña, A.; Nakajima, K.; Rawle, T. D.; Sánchez-Argüelles, D.; Swinbank, A. M.; Webb, T. M. A.; Zeballos, M.

    2015-09-01

    We present Early Science observations with the Large Millimeter Telescope, AzTEC 1.1 mm continuum images and wide bandwidth spectra (73-111 GHz) acquired with the Redshift Search Receiver, towards four bright lensed submillimetre galaxies identified through the Herschel Lensing Survey-snapshot and the Submillimetre Common-User Bolometer Array-2 Cluster Snapshot Survey. This pilot project studies the star formation history and the physical properties of the molecular gas and dust content of the highest redshift galaxies identified through the benefits of gravitational magnification. We robustly detect dust continuum emission for the full sample and CO emission lines for three of the targets. We find that one source shows spectroscopic multiplicity and is a blend of three galaxies at different redshifts (z = 2.040, 3.252, and 4.680), reminiscent of previous high-resolution imaging follow-up of unlensed submillimetre galaxies, but with a completely different search method, that confirm recent theoretical predictions of physically unassociated blended galaxies. Identifying the detected lines as 12CO (Jup = 2-5) we derive spectroscopic redshifts, molecular gas masses, and dust masses from the continuum emission. The mean H2 gas mass of the full sample is (2.0 ± 0.2) × 1011 M⊙/μ, and the mean dust mass is (2.0 ± 0.2) × 109 M⊙/μ, where μ ≈ 2-5 is the expected lens amplification. Using these independent estimations we infer a gas-to-dust ratio of δGDR ≈ 55-75, in agreement with other measurements of submillimetre galaxies. Our magnified high-luminosity galaxies fall on the same locus as other high-redshift submillimetre galaxies, extending the L^' }_CO-LFIR correlation observed for local luminous and ultraluminous infrared galaxies to higher far-infrared and CO luminosities.

  19. A BRIGHT RING OF STAR BIRTH AROUND A GALAXY'S CORE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    n image from NASA's Hubble Space Telescope reveals clusters of infant stars that formed in a ring around the core of the barred-spiral galaxy NGC 4314. This stellar nursery, whose inhabitants were created within the past 5 million years, is the only place in the entire galaxy where new stars are being born. The Hubble image is being presented today (June 11) at the American Astronomical Society meeting in San Diego, Calif. This close-up view by Hubble also shows other interesting details in the galaxy's core: dust lanes, a smaller bar of stars, dust and gas embedded in the stellar ring, and an extra pair of spiral arms packed with young stars. These details make the center resemble a miniature version of a spiral galaxy. While it is not unusual to have dust lanes and rings of gas in the centers of galaxies, it is uncommon to have spiral arms full of young stars in the cores. NGC 4314 is one of the nearest (only 40 million light-years away in the constellation Coma Berenices) examples of a galaxy with a ring of infant stars close to the core. This stellar ring - whose radius is 1,000 light-years - is a great laboratory to study star formation in galaxies. The left-hand image, taken in February 1996 by the 30-inch telescope Prime Focus Camera at the McDonald Observatory in Texas, shows the entire galaxy, including the bar of stars bisecting the core and the outer spiral arms, which begin near the ends of this bar. The box around the galaxy's core pinpoints the focus of the Hubble image. The right-hand image shows Hubble's close-up view of the galaxy's core, taken in December 1995 by the Wide Field and Planetary Camera 2. The bluish-purple clumps that form the ring are the clusters of infant stars. Two dark, wispy lanes of dust and a pair of blue spiral arms are just outside the star-forming ring. The lanes of dust are being shepherded into the ring by the longer, primary stellar bar seen in the ground-based (left-hand) image. The gas is trapped inside the ring

  20. A BRIGHT RING OF STAR BIRTH AROUND A GALAXY'S CORE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    n image from NASA's Hubble Space Telescope reveals clusters of infant stars that formed in a ring around the core of the barred-spiral galaxy NGC 4314. This stellar nursery, whose inhabitants were created within the past 5 million years, is the only place in the entire galaxy where new stars are being born. The Hubble image is being presented today (June 11) at the American Astronomical Society meeting in San Diego, Calif. This close-up view by Hubble also shows other interesting details in the galaxy's core: dust lanes, a smaller bar of stars, dust and gas embedded in the stellar ring, and an extra pair of spiral arms packed with young stars. These details make the center resemble a miniature version of a spiral galaxy. While it is not unusual to have dust lanes and rings of gas in the centers of galaxies, it is uncommon to have spiral arms full of young stars in the cores. NGC 4314 is one of the nearest (only 40 million light-years away in the constellation Coma Berenices) examples of a galaxy with a ring of infant stars close to the core. This stellar ring - whose radius is 1,000 light-years - is a great laboratory to study star formation in galaxies. The left-hand image, taken in February 1996 by the 30-inch telescope Prime Focus Camera at the McDonald Observatory in Texas, shows the entire galaxy, including the bar of stars bisecting the core and the outer spiral arms, which begin near the ends of this bar. The box around the galaxy's core pinpoints the focus of the Hubble image. The right-hand image shows Hubble's close-up view of the galaxy's core, taken in December 1995 by the Wide Field and Planetary Camera 2. The bluish-purple clumps that form the ring are the clusters of infant stars. Two dark, wispy lanes of dust and a pair of blue spiral arms are just outside the star-forming ring. The lanes of dust are being shepherded into the ring by the longer, primary stellar bar seen in the ground-based (left-hand) image. The gas is trapped inside the ring

  1. A population of massive, luminous galaxies hosting heavily dust-obscured gamma-ray bursts: Implications for the use of GRBs as tracers of cosmic star formation

    SciTech Connect

    Perley, D. A.; Levan, A. J.; Tanvir, N. R.; Cenko, S. B.; Bloom, J. S.; Filippenko, A. V.; Morgan, A. N.; Hjorth, J.; Krühler, T.; Fynbo, J. P. U.; Milvang-Jensen, B.; Fruchter, A.; Kalirai, J.; Jakobsson, P.; Prochaska, J. X.

    2013-12-01

    We present observations and analysis of the host galaxies of 23 heavily dust-obscured gamma-ray bursts (GRBs) observed by the Swift satellite during the years 2005-2009, representing all GRBs with an unambiguous host-frame extinction of A{sub V} > 1 mag from this period. Deep observations with Keck, Gemini, Very Large Telescope, Hubble Space Telescope, and Spitzer successfully detect the host galaxies and establish spectroscopic or photometric redshifts for all 23 events, enabling us to provide measurements of the intrinsic host star formation rates, stellar masses, and mean extinctions. Compared to the hosts of unobscured GRBs at similar redshifts, we find that the hosts of dust-obscured GRBs are (on average) more massive by about an order of magnitude and also more rapidly star forming and dust obscured. While this demonstrates that GRBs populate all types of star-forming galaxies, including the most massive, luminous systems at z ≈ 2, at redshifts below 1.5 the overall GRB population continues to show a highly significant aversion to massive galaxies and a preference for low-mass systems relative to what would be expected given a purely star-formation-rate-selected galaxy sample. This supports the notion that the GRB rate is strongly dependent on metallicity, and may suggest that the most massive galaxies in the universe underwent a transition in their chemical properties ∼9 Gyr ago. We also conclude that, based on the absence of unobscured GRBs in massive galaxies and the absence of obscured GRBs in low-mass galaxies, the dust distributions of the lowest-mass and the highest-mass galaxies are relatively homogeneous, while intermediate-mass galaxies (∼10{sup 9} M {sub ☉}) have diverse internal properties.

  2. ZFOURGE: UV to FIR Luminosities and Dust Attenuation Determined from ˜4000 K-Selected Galaxies at 1 < z < 3

    NASA Astrophysics Data System (ADS)

    Forrest, Ben; Tran, Kim-Vy; ZFOURGE Collaboration, CANDELS-H Collaboration

    2016-01-01

    We analyze the UVJ color-color selection technique and the IRX-β dust relation at 1 < z < 3 using data from the Fourstar Galaxy Evolution Survey (ZFOURGE). We build a set of composite SEDs by combining the precise photometric redshifts from a K-band selected sample of ZFOURGE data with public photometry from the Chandra Deep Field South, the Cosmological Evolution Survey, and the Ultra Deep Field. Infrared fluxes are determined from Spitzer/MIPS 24 micron and Herschel/PACS 100 and 160 micron data. From a sample of 4000 K-band selected galaxies, we identify 38 composite SEDs that span the range in UVJ colors and IR to UV flux ratios. These composites lie on the UVJ plane as predicted by their SED shapes.We also find significant deviation from local IRX-β relations. Blue star-forming composites show a slightly elevated IRX value, while red star-forming composites are offset from local relations by as much as 1 dex. We find that the resulting dust attenuation at 1600 Angstroms is over-estimated for these red star-forming galaxies, implying a lower intrinsic SFR than previously inferred, e.g. using the Meurer99 relation.

  3. Far-infrared observations of Sagittarius A - The luminosity and dust density in the central parsec of the Galaxy

    NASA Technical Reports Server (NTRS)

    Becklin, E. E.; Gatley, I.; Werner, M. W.

    1982-01-01

    Far-infrared observations of the central 4 arcmin of the Galaxy with 30-arcsec resolution made simultaneously at 30 microns, 50 microns, and 100 microns are presented. The 30-micron radiation peaks strongly at the position of the galactic center, as determined from the 2-micron surface brightness and the density of ionized gas. The 50- and 100-micron emission is much more extended along the plane and shows two emission lobes, one on either side of the 30-micron peak. At the position of the galactic center itself there is a local minimum in the 100-micron surface brightness. It is concluded that the dust density decreases inward over the central few parsecs of the Galaxy and that the dust density in the central parsec is so low that optical and ultraviolet radiation freely traverses this region. The total luminosity of the sources heating the dust which radiates the far-infrared emission from the central few parsecs is deduced to be between 1 x 10 to the 7th and 3 x 10 to the 7th solar luminosities.

  4. Spitzer Space Telescope Measurements of Dust Reverberation Lags in the Seyfert 1 Galaxy NGC 6418

    NASA Astrophysics Data System (ADS)

    Vazquez, Billy; Galianni, Pasquale; Richmond, Michael; Robinson, Andrew; Axon, David J.; Horne, Keith; Almeyda, Triana; Fausnaugh, Michael; Peterson, Bradley M.; Bottorff, Mark; Gallimore, Jack; Eltizur, Moshe; Netzer, Hagai; Storchi-Bergmann, Thaisa; Marconi, Alessandro; Capetti, Alessandro; Batcheldor, Dan; Buchanan, Catherine; Stirpe, Giovanna; Kishimoto, Makoto; Packham, Christopher; Perez, Enrique; Tadhunter, Clive; Upton, John; Estrada-Carpenter, Vicente

    2015-03-01

    We present results from a 15 month campaign of high-cadence (˜3 days) mid-infrared Spitzer and optical (B and V) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). We find that the 3.6 and 4.5 μm flux variations lag behind those of the optical continuum by 37.2-2.2+2.4 days and 47.1-3.1+3.1 days, respectively. We report a cross-correlation time lag between the 4.5 and 3.6 μm flux of 13.9-0.1+0.5 days. The lags indicate that the dust emitting at 3.6 and 4.5 μm is located at a distance ≈ 1 light-month (≈ 0.03 pc) from the source of the AGN UV-optical continuum. The reverberation radii are consistent with the inferred lower limit to the sublimation radius for pure graphite grains at 1800 K, but smaller by a factor of ˜2 than the corresponding lower limit for silicate grains; this is similar to what has been found for near-infrared (K-band) lags in other AGNs. The 3.6 and 4.5 μm reverberation radii fall above the K-band τ \\propto {{L}0.5} size-luminosity relationship by factors ≲ 2.7 and ≲ 3.4, respectively, while the 4.5 μm reverberation radius is only 27% larger than the 3.6 μm radius. This is broadly consistent with clumpy torus models, in which individual optically thick clouds emit strongly over a broad wavelength range.

  5. GOODS-HERSCHEL: STAR FORMATION, DUST ATTENUATION, AND THE FIR–RADIO CORRELATION ON THE MAIN SEQUENCE OF STAR-FORMING GALAXIES UP TO z ≃ 4

    SciTech Connect

    Pannella, M.; Elbaz, D.; Daddi, E.; Hwang, H. S.; Schreiber, C.; Strazzullo, V.; Aussel, H.; Bethermin, M.; Cibinel, A.; Juneau, S.; Floc’h, E. Le; Leiton, R.; Buat, V.; Charmandaris, V.; Magdis, G.; Ivison, R. J.; Borgne, D. Le; Lin, L.; Morrison, G. E.; and others

    2015-07-10

    We use deep panchromatic data sets in the GOODS-N field, from GALEX to the deepest Herschel far-infrared (FIR) and VLA radio continuum imaging, to explore the evolution of star-formation activity and dust attenuation properties of star-forming galaxies to z ≃ 4, using mass-complete samples. Our main results can be summarized as follows: (i) the slope of the star-formation rate–M{sub *} correlation is consistent with being constant ≃0.8 up to z ≃ 1.5, while its normalization keeps increasing with redshift; (ii) for the first time we are able to explore the FIR–radio correlation for a mass-selected sample of star-forming galaxies: the correlation does not evolve up to z ≃ 4; (iii) we confirm that galaxy stellar mass is a robust proxy for UV dust attenuation in star-forming galaxies, with more massive galaxies being more dust attenuated. Strikingly, we find that this attenuation relation evolves very weakly with redshift, with the amount of dust attenuation increasing by less than 0.3 mag over the redshift range [0.5–4] for a fixed stellar mass; (iv) the correlation between dust attenuation and the UV spectral slope evolves with redshift, with the median UV slope becoming bluer with redshift. By z ≃ 3, typical UV slopes are inconsistent, given the measured dust attenuations, with the predictions of commonly used empirical laws. (v) Finally, building on existing results, we show that gas reddening is marginally larger (by a factor of around 1.3) than the stellar reddening at all redshifts probed. Our results support a scenario where the ISM conditions of typical star-forming galaxies evolve with redshift, such that at z ≥ 1.5 Main Sequence galaxies have ISM conditions moving closer to those of local starbursts.

  6. Optical colours and spectral indices of z = 0.1 eagle galaxies with the 3D dust radiative transfer code skirt

    NASA Astrophysics Data System (ADS)

    Trayford, James W.; Camps, Peter; Theuns, Tom; Baes, Maarten; Bower, Richard G.; Crain, Robert A.; Gunawardhana, Madusha L. P.; Schaller, Matthieu; Schaye, Joop; Frenk, Carlos S.

    2017-09-01

    We present mock optical images, broad-band and H α fluxes, and D4000 spectral indices for 30 145 galaxies from the eagle hydrodynamical simulation at redshift z = 0.1, modelling dust with the skirt Monte Carlo radiative transfer code. The modelling includes a subgrid prescription for dusty star-forming regions, with both the subgrid obscuration of these regions and the fraction of metals in diffuse interstellar dust calibrated against far-infrared fluxes of local galaxies. The predicted optical colours as a function of stellar mass agree well with observation, with the skirt model showing marked improvement over a simple dust-screen model. The orientation dependence of attenuation is weaker than observed because eagle galaxies are generally puffier than real galaxies, due to the pressure floor imposed on the interstellar medium (ISM). The mock H α luminosity function agrees reasonably well with the data, and we quantify the extent to which dust obscuration affects observed H α fluxes. The distribution of D4000 break values is bimodal, as observed. In the simulation, 20 per cent of galaxies deemed 'passive' for the skirt model, i.e. exhibiting D4000 >1.8, are classified 'active' when ISM dust attenuation is not included. The fraction of galaxies with stellar mass greater than 1010 M⊙ that are deemed passive is slightly smaller than observed, which is due to low levels of residual star formation in these simulated galaxies. Colour images, fluxes and spectra of eagle galaxies are to be made available through the public eagle data base.

  7. Galaxies

    SciTech Connect

    Not Available

    1981-01-01

    Normal galaxies, radio galaxies, and Seyfert galaxies are considered. The large magellanic cloud and the great galaxy in Andromedia are highlighted. Quasars and BL lacertae objects are also discussed and a review of the spectral observations of all of these galaxies and celestial objects is presented.

  8. Dust outflows from quiescent spiral disks.

    NASA Astrophysics Data System (ADS)

    Alton, P. B.; Rand, R. J.; Xilouris, E. M.; Bevan, S.; Ferguson, A. M.; Davies, J. I.; Bianchi, S.

    2000-07-01

    We have conducted a search for ``dust chimneys'' in a sample of 10 highly-inclined spiral galaxies (i=86-90deg) which we had previously observed in the Hα emission line (Rand 1996). We have procured B-band CCD images for this purpose and employed unsharp-masking techniques to accentuate the structure of the dust lane. A scattering+absorption radiation transfer model enabled us to separate 5 galaxies from the sample which are sufficiently inclined (i>87deg) for us to reliably identify and quantify dust clouds residing at over 2 scale-heights above the disk. Three of these galaxies possess numerous curvi-linear chimney structures stretching up to 2 kpc from the midplane and the fraction of total galactic dust contained in such structures is of order 1%. Optical extinction offers a lower limit to the amount of dust contained in the extraplanar layer but, by examining the transparent submm thermal emission from NGC 891, we fix an upper limit of 5%. Our results are consistent with a similar recent study by Howk & Savage (1999) which indicates that about half of quiescent spiral disks possess detectable dust chimneys. We have compared our optical images with the corresponding Hα emission-line radiation. We do not find a detailed spatial correspondance between dust chimneys and either sites of recent star-formation or the extraplanar diffuse ionized gas. This is somewhat surprising given that FIR-bright galaxies, such as M 82, are known to entrain dust at the working surface of the starburst-driven outflow (traced in Hα ). It is possible a global correlation exists, with disks experiencing overall higher rates of star-formation also possessing the greatest number of chimneys. This may indicate a timescale difference between the two phenomena with the Hα phase lasting ~ 106 yr but chimneys requiring ~ 107 yr to form. Additionally, we have investigated the edge-on disk NGC 55 which, being ten times closer than galaxies in our main sample, allows us to examine in greater

  9. Dust Attenuation Of Star-Forming Galaxies At Z 3 And Beyond New Insights From Alma Observations (Arxiv:1705.01559)

    NASA Astrophysics Data System (ADS)

    Fudamoto, Y.; Oesch, P.; Schinnerer, E.; Groves, B.; Karim, A.; Magnelli, B.; Sargent, T.; Cassata, P.; Lang, P.; Liu, D.; Le Fèvre, O.; Smolčić, V.; Tasca, L.

    2017-06-01

    We present results on the dust attenuation of galaxies at redshift 3-6 by studying the relationship between the UV spectral slope (ßUV) and the infrared excess (IRX; LIR/LUV) using ALMA far-infrared continuum observations. Our study is based on a sample of 67 massive, star-forming galaxies with a median mass of M* 1010.7 M⊙ spanning a redshift range z=2.6-3.7 (median z=3.2) that were observed with ALMA band-6. Both the individual ALMA detections (41 sources) and stacks including all galaxies show the IRX-ßUV relationship at z 3 is mostly consistent with that of local starburst galaxies on average. However, we find evidence for a large dispersion around the mean relationship by up to ±0.5 dex. Nevertheless, the locally calibrated dust correction factors based on the IRX-ßUV relation are on average applicable to main-sequence z 3 galaxies. This does not appear to be the case at even higher redshifts, however. Using public ALMA observations of z 4-6 galaxies we find evidence for a significant evolution in the IRX-ßUV and the IRX-M* relations beyond z 3 toward lower IRX values. We discuss several caveats that could affect these results, including the assumed dust temperature. ALMA observations of larger z>3 galaxy samples will be required to confirm this intriguing redshift evolution.

  10. The continuum of type 1 Seyfert galaxies. I - A single form modified by the effects of dust

    NASA Technical Reports Server (NTRS)

    Ward, Martin; Elvis, Martin; Fabbiano, G.; Carleton, N. P.; Willner, S. P.

    1987-01-01

    Broad-band measurements from 1 to 20 microns of 26 emission-line active galactic nuclei (AGNs), mainly Seyfert 1 galaxies, have been made. These data have been combined with previous optical and infrared photometry and IRAS 12, 25, 60 and 100 micron fluxes, giving a total sample of 37 AGNs, all of which have hard X-ray measurements. The sample includes all the emission-line AGNs identified in the Piccinotti et al. (1982) survey. When corrected for stellar contributions in the near-infrared, the continuum energy distributions can be classified observationally into three types: (1) bare, minimally reddened AGNs; (2) reddened AGNs; and (3) AGNs for which the far-infrared emission is contaminated by the host galaxy. These classifications reflect a range of luminosities and different environments rather than intrinsic differences in the primary continuum of the AGNs. The data are consistent with a single underlying form of active galaxy continuum modified by the presence of dust and of the host galaxy.

  11. LACK OF INTERACTION BETWEEN THE DUST GRAINS AND THE ANOMALOUS RADIO JET IN THE NEARBY SPIRAL GALAXY NGC 4258

    SciTech Connect

    Laine, Seppo; Krause, Marita; Tabatabaei, Fatemeh S.; Siopis, Christos E-mail: mkrause@mpifr-bonn.mpg.d E-mail: christos.siopis@ulb.ac.b

    2010-10-15

    We obtained Spitzer/IRAC 3.6-8 {mu}m images of the nearby spiral galaxy NGC 4258 to study possible interactions between dust and the radio jet. In our analysis, we also included high-resolution radio continuum, H{alpha}, CO, and X-ray data. Our data reveal that the 8 {mu}m emission, believed to originate largely from polycyclic aromatic hydrocarbon molecules and hot dust, is an excellent tracer of the normal spiral structure in NGC 4258, and hence it originates from the galactic plane. We investigated the possibility of dust destruction by the radio jet by calculating correlation coefficients between the 8 {mu}m and radio continuum emissions along the jet in two independent ways, namely, (1) from wavelet-transformed maps of the original images at different spatial scales and (2) from one-dimensional intensity cuts perpendicular to the projected path of the radio jet on the sky. No definitive sign of a correlation (or anticorrelation) was detected on relevant spatial scales with either approach, implying that any dust destruction must take place at spatial scales that are not resolved by our observations.

  12. Mid-infrared dust in two nearby radio galaxies, NGC 1316 (Fornax A) and NGC 612 (PKS 0131-36)

    NASA Astrophysics Data System (ADS)

    Duah Asabere, B.; Horellou, C.; Jarrett, T. H.; Winkler, H.

    2016-07-01

    Context. Most radio galaxies are hosted by giant gas-poor ellipticals, but some contain significant amounts of dust, which is likely to be of external origin. Aims: In order to characterize the mid-IR properties of two of the most nearby and brightest merger-remnant radio galaxies of the Southern hemisphere, NGC 1316 (Fornax A) and NGC 612 (PKS 0131-36), we used observations with the Wide-field Infrared Survey Explorer (WISE) at wavelengths of 3.4, 4.6, 12 and 22 μm and Spitzer mid-infrared spectra. Methods: By applying a resolution-enhancement technique, new WISE images were produced at angular resolutions ranging from 2.̋6 to 5.̋5. Global measurements were performed in the four WISE bands, and stellar masses and star-formation rates were estimated using published scaling relations. Two methods were used to uncover the distribution of dust, one relying on two-dimensional fits to the 3.4 μm images to model the starlight, and the other one using a simple scaling and subtraction of the 3.4 μm images to estimate the stellar continuum contribution to the emission in the 12 and 22 μm bands. Results: The two galaxies differ markedly in their mid-IR properties. The 3.4 μm brightness distribution can be well represented by the superposition of two Sérsic models in NGC 1316 and by a Sérsic model and an exponential disk in NGC 612. The WISE colors of NGC 1316 are typical of those of early-type galaxies; those of NGC 612 are in the range found for star-forming galaxies. From the 22 μm luminosity, we infer a star-formation rate of ~0.7 M⊙ yr-1 in NGC 1316 and ~7 M⊙ yr-1 in NGC 612. Spitzer spectroscopy shows that the 7.7-to-11.3 μm PAH line ratio is significantly lower in NGC 1316 than in NGC 612. The WISE images reveal resolved emission from dust in the central 1'-2' of the galaxies. In NGC 1316, the extra-nuclear emission coincides with two dusty regions NW and SE of the nucleus seen in extinction in optical images and where molecular gas is known to reside

  13. The dust-to-stellar mass ratio as a valuable tool to probe the evolution of local and distant star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Calura, F.; Pozzi, F.; Cresci, G.; Santini, P.; Gruppioni, C.; Pozzetti, L.; Gilli, R.; Matteucci, F.; Maiolino, R.

    2017-02-01

    The survival of dust grains in galaxies depends on various processes. Dust can be produced in stars, it can grow in the interstellar medium and be destroyed by astration and interstellar shocks. In this paper, we assemble a few data samples of local and distant star-forming galaxies to analyse various dust-related quantities in low- and high-redshift galaxies, and to study how the relations linking the dust mass to the stellar mass and star formation rate evolve with redshift. We interpret the available data by means of chemical evolution models for discs and proto-spheroid (PSPH) starburst galaxies. In particular, we focus on the dust-to-stellar mass (DTS) ratio, as this quantity represents a true measure of how much dust per unit stellar mass survives the various destruction processes in galaxies and is observable. The theoretical models outline the strong dependence of this quantity on the underlying star formation history. Spiral galaxies are characterized by a nearly constant DTS as a function of the stellar mass and cosmic time, whereas PSPHs present an early steep increase of the DTS, which stops at a maximal value and decreases in the latest stages. In their late starburst phase, these models show a decrease of the DTS with their mass, which allows us to explain the observed anti-correlation between the DTS and the stellar mass. The observed redshift evolution of the DTS ratio shows an increase from z ˜ 0 to z ˜ 1, followed by a roughly constant behaviour at 1 ≲ z ≲ 2.5. Our models indicate a steep decrease of the global DTS at early times, which implies an expected decrease of the DTS at larger redshift.

  14. Two-dimensional Magnetohydrodynamic Simulations of Barred Galaxies

    NASA Astrophysics Data System (ADS)

    Kim, Woong-Tae; Stone, James M.

    2012-06-01

    Barred galaxies are known to possess magnetic fields that may affect the properties of bar substructures such as dust lanes and nuclear rings. We use two-dimensional high-resolution magnetohydrodynamic (MHD) simulations to investigate the effects of magnetic fields on the formation and evolution of such substructures, as well as on the mass inflow rates to the galaxy center. The gaseous medium is assumed to be infinitesimally thin, isothermal, non-self-gravitating, and threaded by initially uniform, azimuthal magnetic fields. We find that there exists an outermost x 1-orbit relative to which gaseous responses to an imposed stellar bar potential are completely different between inside and outside. Inside this orbit, gas is shocked into dust lanes and infalls to form a nuclear ring. Magnetic fields are compressed in dust lanes, reducing their peak density. Magnetic stress removes further angular momentum of the gas at the shocks, temporarily causing the dust lanes to bend into an "L" shape and eventually leading to a smaller and more centrally distributed ring than in unmagnetized models. The mass inflow rates in magnetized models correspondingly become larger, by more than two orders of magnitude when the initial fields have an equipartition value with thermal energy, than in the unmagnetized counterparts. Outside the outermost x 1-orbit, on the other hand, an MHD dynamo due to the combined action of the bar potential and background shear operates near the corotation and bar-end regions, efficiently amplifying magnetic fields. The amplified fields shape into trailing magnetic arms with strong fields and low density. The base of the magnetic arms has a thin layer in which magnetic fields with opposite polarity reconnect via a tearing-mode instability. This produces numerous magnetic islands with large density that propagate along the arms to turn the outer disk into a highly chaotic state.

  15. Early Science with the Large Millimeter Telescope: Detection of Dust Emission in Multiple Images of a Normal Galaxy at z > 4 Lensed by a Frontier Fields Cluster

    NASA Astrophysics Data System (ADS)

    Pope, Alexandra; Montaña, Alfredo; Battisti, Andrew; Limousin, Marceau; Marchesini, Danilo; Wilson, Grant W.; Alberts, Stacey; Aretxaga, Itziar; Avila-Reese, Vladimir; Ramón Bermejo-Climent, José; Brammer, Gabriel; Bravo-Alfaro, Hector; Calzetti, Daniela; Chary, Ranga-Ram; Cybulski, Ryan; Giavalisco, Mauro; Hughes, David; Kado-Fong, Erin; Keller, Erica; Kirkpatrick, Allison; Labbe, Ivo; Lange-Vagle, Daniel; Lowenthal, James; Murphy, Eric; Oesch, Pascal; Rosa Gonzalez, Daniel; Sánchez-Argüelles, David; Shipley, Heath; Stefanon, Mauro; Vega, Olga; Whitaker, Katherine; Williams, Christina C.; Yun, Min; Zavala, Jorge A.; Zeballos, Milagros

    2017-04-01

    We directly detect dust emission in an optically detected, multiply imaged galaxy lensed by the Frontier Fields cluster MACSJ0717.5+3745. We detect two images of the same galaxy at 1.1 mm with the AzTEC camera on the Large Millimeter Telescope leaving no ambiguity in the counterpart identification. This galaxy, MACS0717_Az9, is at z > 4 and the strong lensing model (μ = 7.5) allows us to calculate an intrinsic IR luminosity of 9.7 × 1010 L ⊙ and an obscured star formation rate of 14.6 ± 4.5 M ⊙ yr-1. The unobscured star formation rate from the UV is only 4.1 ± 0.3 M ⊙ yr-1, which means the total star formation rate (18.7 ± 4.5 M ⊙ yr-1) is dominated (75%-80%) by the obscured component. With an intrinsic stellar mass of only 6.9 × 109 M ⊙, MACS0717_Az9 is one of only a handful of z > 4 galaxies at these lower masses that is detected in dust emission. This galaxy lies close to the estimated star formation sequence at this epoch. However, it does not lie on the dust obscuration relation (IRX-β) for local starburst galaxies and is instead consistent with the Small Magellanic Cloud attenuation law. This remarkable lower mass galaxy, showing signs of both low metallicity and high dust content, may challenge our picture of dust production in the early universe.

  16. A Tale of Three Galaxies: Anomalous Dust Properties in IRAS F10398+1455, IRAS F21013-0739, and SDSS J0808+3948

    NASA Astrophysics Data System (ADS)

    Xie, Yanxia; Hao, Lei; Li, Aigen

    2014-10-01

    On a galactic scale, the 9.7 μm silicate emission is usually only seen in type 1 active galactic nuclei (AGNs). They usually also display a flat emission continuum at ~5-8 μm and the absence of polycyclic aromatic hydrocarbon (PAH) emission bands. In contrast, starburst galaxies, luminous infrared (IR) galaxies, and ultraluminous IR galaxies exhibit a red 5-8 μm emission continuum, strong 9.7 μm and 18 μm silicate absorption features, and strong PAH emission bands. Here, we report the detection of anomalous dust properties by the Spitzer/Infrared Spectrograph in three galaxies (IRAS F10398+1455, IRAS F21013-0739, and SDSS J0808+3948) which are characterized by the simultaneous detection of a red 5-8 μm emission continuum, the 9.7 and 18 μm silicate emission features, as well as strong PAH emission bands. These apparently contradictory dust IR emission properties are discussed in terms of iron-poor silicate composition, carbon dust deficit, small grain size, and low dust temperature in the young AGN phase of these three galaxies.

  17. A TALE OF THREE GALAXIES: ANOMALOUS DUST PROPERTIES IN IRAS F10398+1455, IRAS F21013–0739, AND SDSS J0808+3948

    SciTech Connect

    Xie, Yanxia; Hao, Lei; Li, Aigen

    2014-10-20

    On a galactic scale, the 9.7 μm silicate emission is usually only seen in type 1 active galactic nuclei (AGNs). They usually also display a flat emission continuum at ∼5-8 μm and the absence of polycyclic aromatic hydrocarbon (PAH) emission bands. In contrast, starburst galaxies, luminous infrared (IR) galaxies, and ultraluminous IR galaxies exhibit a red 5-8 μm emission continuum, strong 9.7 μm and 18 μm silicate absorption features, and strong PAH emission bands. Here, we report the detection of anomalous dust properties by the Spitzer/Infrared Spectrograph in three galaxies (IRAS F10398+1455, IRAS F21013-0739, and SDSS J0808+3948) which are characterized by the simultaneous detection of a red 5-8 μm emission continuum, the 9.7 and 18 μm silicate emission features, as well as strong PAH emission bands. These apparently contradictory dust IR emission properties are discussed in terms of iron-poor silicate composition, carbon dust deficit, small grain size, and low dust temperature in the young AGN phase of these three galaxies.

  18. X-ray observations of dust obscured galaxies in the Chandra deep field south

    NASA Astrophysics Data System (ADS)

    Corral, A.; Georgantopoulos, I.; Comastri, A.; Ranalli, P.; Akylas, A.; Salvato, M.; Lanzuisi, G.; Vignali, C.; Koutoulidis, L.

    2016-08-01

    We present the properties of X-ray detected dust obscured galaxies (DOGs) in the Chandra deep field south. In recent years, it has been proposed that a significant percentage of the elusive Compton-thick (CT) active galactic nuclei (AGN) could be hidden among DOGs. This type of galaxy is characterized by a very high infrared (IR) to optical flux ratio (f24 μm/fR > 1000), which in the case of CT AGN could be due to the suppression of AGN emission by absorption and its subsequent re-emission in the IR. The most reliable way of confirming the CT nature of an AGN is by X-ray spectroscopy. In a previous work, we presented the properties of X-ray detected DOGs by making use of the deepest X-ray observations available at that time, the 2Ms observations of the Chandra deep fields, the Chandra deep field north (CDF-N), and the Chandra deep field south (CDF-S). In that work, we only found a moderate percentage (<50%) of CT AGN among the DOGs sample. However, we pointed out that the limited photon statistics for most of the sources in the sample did not allow us to strongly constrain this number. In this paper, we further explore the properties of the sample of DOGs in the CDF-S presented in that work by using not only a deeper 6Ms Chandra survey of the CDF-S, but also by combining these data with the 3Ms XMM-Newton survey of the CDF-S. We also take advantage of the great coverage of the CDF-S region from the UV to the far-IR to fit the spectral energy distributions (SEDs) of our sources. Out of the 14 AGN composing our sample, 9 are highly absorbed (NH > 1023 cm-2), whereas 2 look unabsorbed, and the other 3 are only moderately absorbed. Among the highly absorbed AGN, we find that only three could be considered CT AGN. In only one of these three cases, we detect a strong Fe Kα emission line; the source is already classified as a CT AGN with Chandra data in a previous work. Here we confirm its CT nature by combining Chandra and XMM-Newton data. For the other two CT

  19. Cosmic dust

    NASA Technical Reports Server (NTRS)

    Brownlee, Donald E.; Sandford, Scott A.

    1992-01-01

    Dust is a ubiquitous component of our galaxy and the solar system. The collection and analysis of extraterrestrial dust particles is important to exobiology because it provides information about the sources of biogenically significant elements and compounds that accumulated in distant regions of the solar nebula and that were later accreted on the planets. The topics discussed include the following: general properties of interplanetary dust; the carbonaceous component of interplanetary dust particles; and the presence of an interstellar component.

  20. The Dust Content and Radiation Fields of Sample of Galaxies in the ELAIS-N1 Field

    NASA Astrophysics Data System (ADS)

    Shalima, P.; Gogoi, Rupjyoti; Pathak, Amit; Misra, Ranjeev; Gupta, Ranjan; Vaidya, D. B.

    2015-08-01

    The Mid-IR colors ($F_{8}/F_{24}$) of galaxies together with their IR-UV luminosity correlations can be used to get some insight into the relative abundance of the different dust grain populations present in them. The ELAIS-N1 field contains thousands of galaxies which do not have optical spectra but have been observed in the Mid-IR by {\\it Spitzer} and UV by {\\it GALEX} making it ideal for these studies. As part of this work we have selected a sample of galaxies from the ELAIS-N1 field which have photometric observations in the MIR and UV as well as photometric redshifts from the SDSS database. We put the constraint that the redshifts are $\\le$ 0.1, thereby giving us a total of 309 galaxies. We find that the majority of the galaxies in the sample are PAH dominated due to their high MIR flux ratio. We also find a reasonable correlation between the Mid-IR and the UV luminosities out of which the Mid-IR emission from PAHs at 8 $\\mu$m is marginally better correlated than the 24 $\\mu$m VSG emission with the UV luminosities. However, if we divide the sample based on their $F_{8}/F_{24}$ ratios which is also an indicator of metallicity, the MIR-UV correlation seems to increase with the $F_{8}/F_{24}$ ratio. But the MIR-UV correlations are not very different for the PAHs and the VSG population within the individual metallicity groups.

  1. The hidden quasar nucleus of a WISE-selected, hyperluminous, dust-obscured galaxy at z ~ 2.3

    NASA Astrophysics Data System (ADS)

    Piconcelli, E.; Vignali, C.; Bianchi, S.; Zappacosta, L.; Fritz, J.; Lanzuisi, G.; Miniutti, G.; Bongiorno, A.; Feruglio, C.; Fiore, F.; Maiolino, R.

    2015-02-01

    We present the first X-ray spectrum of a hot dust-obscured galaxy (DOG), namely W1835+4355 at z ~ 2.3. Hot DOGs represent a very rare population of hyperluminous (≥1047 erg s-1), dust-enshrouded objects at z ≥ 2 recently discovered in the WISE All Sky Survey. The 40 ks XMM-Newton spectrum reveals a continuum as flat (Γ ~ 0.8) as typically seen in heavily obscured AGN. This, along with the presence of strong Fe Kα emission, clearly suggests a reflection-dominated spectrum due to Compton-thick absorption. In this scenario, the observed luminosity of L2-10~ 2 × 1044 erg s-1 is a fraction (<10%) of the intrinsic one, which is estimated to be ≳ 5 × 1045 erg s-1 by using several proxies. The Herschel data allow us to constrain the SED up to the sub-mm band, providing a reliable estimate of the quasar contribution (~75%) to the IR luminosity as well as the amount of star formation (~2100 M⊙ yr-1). Our results thus provide additional pieces of evidence that associate Hot DOGs with an exceptionally dusty phase during which luminous quasars and massive galaxies co-evolve and a very efficient and powerful AGN-driven feedback mechanism is predicted by models.

  2. Simultaneously modelling far-infrared dust emission and its relation to CO emission in star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Shetty, Rahul; Roman-Duval, Julia; Hony, Sacha; Cormier, Diane; Klessen, Ralf S.; Konstandin, Lukas K.; Loredo, Thomas; Pellegrini, Eric W.; Ruppert, David

    2016-07-01

    We present a method to simultaneously model the dust far-infrared (FIR) spectral energy distribution (SED) and the total infrared - carbon monoxide (CO) integrated intensity (SIR-ICO) relationship. The modelling employs a hierarchical Bayesian (HB) technique to estimate the dust surface density, temperature (Teff), and spectral index at each pixel from the observed FIR maps. Additionally, given the corresponding CO map, the method simultaneously estimates the slope and intercept between the FIR and CO intensities, which are global properties of the observed source. The model accounts for correlated and uncorrelated uncertainties, such as those present in Herschel observations. Using synthetic data sets, we demonstrate the accuracy of the HB method, and contrast the results with common non-hierarchical fitting methods. As an initial application, we model the dust and gas on 100 pc scales in the Magellanic Clouds from Herschel FIR and NANTEN CO observations. The slopes of the logSIR-logICO relationship are similar in both galaxies, falling in the range 1.1-1.7. However, in the Small Magellanic Cloud the intercept is nearly three times higher, which can be explained by its lower metallicity than the Large Magellanic Cloud (LMC), resulting in a larger SIR per unit ICO. The HB modelling evidences an increase in Teff in regions with the highest ICO in the LMC. This may be due to enhanced dust heating in the densest molecular regions from young stars. Such simultaneous dust and gas modelling may reveal variations in the properties of the interstellar medium and its association with other galactic characteristics, such as star formation rates and/or metallicities.

  3. UV to IR Luminosities and Dust Attenuation Determined from ~4000 K-selected Galaxies at 1 < z < 3 in the ZFOURGE Survey

    NASA Astrophysics Data System (ADS)

    Forrest, Ben; Tran, Kim-Vy H.; Tomczak, Adam R.; Broussard, Adam; Labbé, Ivo; Papovich, Casey; Kriek, Mariska; Allen, Rebecca J.; Cowley, Michael; Dickinson, Mark; Glazebrook, Karl; van Houdt, Josha; Inami, Hanae; Kacprzak, Glenn G.; Kawinwanichakij, Lalitwadee; Kelson, Daniel; McCarthy, Patrick J.; Monson, Andrew; Morrison, Glenn; Nanayakkara, Themiya; Persson, S. Eric; Quadri, Ryan F.; Spitler, Lee R.; Straatman, Caroline; Tilvi, Vithal

    2016-02-01

    We build a set of composite galaxy spectral energy distributions (SEDs) by de-redshifting and scaling multi-wavelength photometry from galaxies in the ZFOURGE survey, covering the CDFS, COSMOS, and UDS fields. From a sample of ˜4000 Ks-band selected galaxies, we define 38 composite galaxy SEDs that yield continuous low-resolution spectra (R ˜ 45) over the rest-frame range 0.1-4 μm. Additionally, we include far infrared photometry from the Spitzer Space Telescope and the Herschel Space Observatory to characterize the infrared properties of our diverse set of composite SEDs. From these composite SEDs we analyze the rest-frame UVJ colors, as well as the ratio of IR to UV light (IRX) and the UV slope (β) in the IRX-β dust relation at 1 < z < 3. Blue star-forming composite SEDs show IRX and β values consistent with local relations; dusty star-forming galaxies have considerable scatter, as found for local IR bright sources, but on average appear bluer than expected for their IR fluxes. We measure a tight linear relation between rest-frame UVJ colors and dust attenuation for star-forming composites, providing a direct method for estimating dust content from either (U - V) or (V-J) rest-frame colors for star-forming galaxies at intermediate redshifts. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  4. An Exploration of Dusty Galaxies

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-04-01

    Submillimeter galaxies i.e., galaxies that we detect in the submillimeter wavelength range are mysterious creatures. Its only within the last couple decades that weve had telescope technology capable of observing them, and were only now getting to the point where angular resolution limits allow us to examine them closely. A new study has taken advantage of new capabilities to explore the properties of a sample of 52 of thesegalaxies.Dusty Star FormationSubmillimeter galaxies are generally observed in the early universe. Though theyre faint in other wavebands, theyre extremely luminous in infrared and submillimeter their infrared luminosities are typically trillions of times the Suns luminosity. This is thought to be because these galaxies are very actively forming stars at rates of hundreds of times that of the Milky Way!Example 10 10 true-color images of ten submillimeter galaxies in the authors ALMA-identified sample. [Simpson et al. 2017]Submillimeter galaxies are also extremely dusty, so we dont see their star formation directly in optical wavelengths. Instead, we see the stellar light after its been absorbed and reemitted by interstellar dust lanes were indirectly observing heavily obscured star formation.Why look for submillimeter galaxies? Studying them can help us to learn about galaxy and star formation early in our universes history, and help us to understand how the universe has evolved into what we see locally today.Submillimeter StrugglesDue to angular resolution limitations in the past, we often couldnt pin down the exact locations of submillimeter galaxies, preventing us from examining them properly. But now a team of scientists has used the Atacama Large Millimeter/submillimeter array (ALMA) to precisely locate 52 submillimeter galaxies identified by the Submillimeter Common-User Bolometer Array (SCUBA-2) in the UKIDSS Ultra Deep Survey field.The precise locations made possible by ALMA allowed the team led by James Simpson (University of Edinburgh

  5. Midsummer's Dream Galaxies

    NASA Astrophysics Data System (ADS)

    2005-08-01

    -years away in the constellation Coma Berenices (Berenice's Hair). It displays a bright yellowish central bulge that juts out above most impressive dust lanes. Because it is relatively close (it is only 12 times farther away than Messier 31, the Andromeda galaxy, which is the major galaxy closest to us) and relatively large (roughly one third larger than the Milky Way), it does not fit entirely into the field of view of the FORS instrument (about 7 x 7 arcmin2). Many background galaxies are also visible in this FORS image, giving full meaning to their nickname of "island universes". Messier 83 If our Milky Way were to resemble this one, we certainly would be proud of our home! The beautiful spiral galaxy Messier 83 [4] is located in the southern constellation Hydra (the Water Snake) and is also known as NGC 5236 and as the Southern Pinwheel galaxy. Its distance is about 15 million light-years. Being about twice as small as the Milky Way, its size on the sky is 11x10 arcmin2. The image show clumpy, well-defined spiral arms that are rich in young stars, while the disc reveals a complex system of intricate dust lanes. This galaxy is known to be a site of vigorous star formation.

  6. Dust in the Reionization Era: ALMA Observations of a z = 8.38 Gravitationally Lensed Galaxy

    NASA Astrophysics Data System (ADS)

    Laporte, N.; Ellis, R. S.; Boone, F.; Bauer, F. E.; Quénard, D.; Roberts-Borsani, G. W.; Pelló, R.; Pérez-Fournon, I.; Streblyanska, A.

    2017-03-01

    We report on the detailed analysis of a gravitationally lensed Y-band dropout, A2744_YD4, selected from deep Hubble Space Telescope imaging in the Frontier Field cluster Abell 2744. Band 7 observations with the Atacama Large Millimeter/submillimeter Array (ALMA) indicate the proximate detection of a significant 1 mm continuum flux suggesting the presence of dust for a star-forming galaxy with a photometric redshift of z≃ 8. Deep X-SHOOTER spectra confirms the high-redshift identity of A2744_YD4 via the detection of Lyα emission at a redshift z = 8.38. The association with the ALMA detection is confirmed by the presence of [O iii] 88 μm emission at the same redshift. Although both emission features are only significant at the 4σ level, we argue their joint detection and the positional coincidence with a high-redshift dropout in the Hubble Space Telescope images confirms the physical association. Analysis of the available photometric data and the modest gravitational magnification (μ ≃ 2) indicates A2744_YD4 has a stellar mass of ∼2 × 109 {M}ȯ , a star formation rate of ∼20 {M}ȯ yr‑1 and a dust mass of ∼6 × 106 {M}ȯ . We discuss the implications of the formation of such a dust mass only ≃ 200 {Myr} after the onset of cosmic reionization.

  7. Circumnuclear Regions In Barred Spiral Galaxies. 1; Near-Infrared Imaging

    NASA Technical Reports Server (NTRS)

    Perez-Ramirez, D.; Knapen, J. H.; Peletier, R. F.; Laine, S.; Doyon, R.; Nadeau, D.

    2000-01-01

    We present sub-arcsecond resolution ground-based near-infrared images of the central regions of a sample of twelve barred galaxies with circumnuclear star formation activity, which is organized in ring-like regions typically one kiloparsec in diameter. We also present Hubble Space Telescope near-infrared images of ten of our sample galaxies, and compare them with our ground-based data. Although our sample galaxies were selected for the presence of circumnuclear star formation activity, our broad-band near-infrared images are heterogeneous, showing a substantial amount of small-scale structure in some galaxies, and practically none in others. We argue that, where it exists, this structure is caused by young stars, which also cause the characteristic bumps or changes in slope in the radial profiles of ellipticity, major axis position angle, surface brightness and colour at the radius of the circumnuclear ring in most of our sample galaxies. In 7 out of 10 HST images, star formation in the nuclear ring is clearly visible as a large number of small emitting regions, organised into spiral arm fragments, which are accompanied by dust lanes. NIR colour index maps show much more clearly the location of dust lanes and, in certain cases, regions of star formation than single broad-band images. Circumnuclear spiral structure thus outlined appears to be common in barred spiral galaxies with circumnuclear star formation.

  8. A Systematic Investigation of Cold Gas and Dust in "Normal" Star-Forming Galaxies and Starbursts at Redshifts 5-6

    NASA Astrophysics Data System (ADS)

    Riechers, Dominik A.; Carilli, Chris Luke; Capak, Peter L.; COSMOS, HerMES

    2016-01-01

    Cold molecular and atomic gas plays a central role in our understanding of early galaxy formation and evolution. It represents the material that stars form out of, and its mass, distribution, excitation, and dynamics provide crucial insight into the physical processes that support the ongoing star formation and stellar mass buildup. We present some of the most recent progress in studies of gas-rich galaxies out to the highest redshifts through detailed investigations of the cold gas and dust with the most powerful facilities, i.e., the Karl G. Jansky Very Large Array (VLA), the NOrthern Extended Millimeter Array (NOEMA) and the Atacama Large (sub-) Millimeter Array (ALMA). Facilitating the impressive sensitivity of ALMA, this investigation encompasses a systematic study of the star-forming interstellar medium, gas dynamics, and dust obscuration in massive dusty starbursts and (much less luminous and massive) "typical" galaxies at such early epochs. These new results show that "typical" z>5 galaxies are significantly metal-enriched, but not heavily dust-obscured, consistent with a decreasing contribution of dust-obscured star formation to the star formation history of the universe towards the earliest cosmic epochs.

  9. A MINUET OF GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This troupe of four galaxies, known as Hickson Compact Group 87 (HCG 87), is performing an intricate dance orchestrated by the mutual gravitational forces acting between them. The dance is a slow, graceful minuet, occurring over a time span of hundreds of millions of years. The Wide Field and Planetary Camera 2 on NASA's Hubble Space Telescope (HST) provides a striking improvement in resolution over previous ground-based imaging. In particular, this image reveals complex details in the dust lanes of the group's largest galaxy member (HCG 87a), which is actually disk-shaped, but tilted so that we see it nearly edge-on. Both 87a and its elliptically shaped nearest neighbor (87b) have active galactic nuclei which are believed to harbor black holes that are consuming gas. A third group member, the nearby spiral galaxy 87c, may be undergoing a burst of active star formation. Gas flows within galaxies can be intensified by the gravitational tidal forces between interacting galaxies. So interactions can provide fresh fuel for both active nuclei and starburst phenomena. These three galaxies are so close to each other that gravitational forces disrupt their structure and alter their evolution. From the analysis of its spectra, the small spiral near the center of the group could either be a fourth member or perhaps an unrelated background object. The HST image was made by combining images taken in four different color filters in order to create a three-color picture. Regions of active star formation are blue (hot stars) and also pinkish if hot hydrogen gas is present. The complex dark bands across the large edge-on disk galaxy are due to interstellar dust silhouetted against the galaxy's background starlight. A faint tidal bridge of stars can be seen between the edge-on and elliptical galaxies. HCG 87 was selected for Hubble imaging by members of the public who visited the Hubble Heritage website (http://heritage.stsci.edu) during the month of May and registered their votes

  10. A MINUET OF GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This troupe of four galaxies, known as Hickson Compact Group 87 (HCG 87), is performing an intricate dance orchestrated by the mutual gravitational forces acting between them. The dance is a slow, graceful minuet, occurring over a time span of hundreds of millions of years. The Wide Field and Planetary Camera 2 on NASA's Hubble Space Telescope (HST) provides a striking improvement in resolution over previous ground-based imaging. In particular, this image reveals complex details in the dust lanes of the group's largest galaxy member (HCG 87a), which is actually disk-shaped, but tilted so that we see it nearly edge-on. Both 87a and its elliptically shaped nearest neighbor (87b) have active galactic nuclei which are believed to harbor black holes that are consuming gas. A third group member, the nearby spiral galaxy 87c, may be undergoing a burst of active star formation. Gas flows within galaxies can be intensified by the gravitational tidal forces between interacting galaxies. So interactions can provide fresh fuel for both active nuclei and starburst phenomena. These three galaxies are so close to each other that gravitational forces disrupt their structure and alter their evolution. From the analysis of its spectra, the small spiral near the center of the group could either be a fourth member or perhaps an unrelated background object. The HST image was made by combining images taken in four different color filters in order to create a three-color picture. Regions of active star formation are blue (hot stars) and also pinkish if hot hydrogen gas is present. The complex dark bands across the large edge-on disk galaxy are due to interstellar dust silhouetted against the galaxy's background starlight. A faint tidal bridge of stars can be seen between the edge-on and elliptical galaxies. HCG 87 was selected for Hubble imaging by members of the public who visited the Hubble Heritage website (http://heritage.stsci.edu) during the month of May and registered their votes

  11. LIFTING THE VEIL OF DUST TO REVEAL THE SECRETS OF SPIRAL GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have combined information from the NASA Hubble Space Telescope's visible- and infrared-light cameras to show the hearts of four spiral galaxies peppered with ancient populations of stars. The top row of pictures, taken by a ground-based telescope, represents complete views of each galaxy. The blue boxes outline the regions observed by the Hubble telescope. The bottom row represents composite pictures from Hubble's visible- and infrared-light cameras, the Wide Field and Planetary Camera 2 (WFPC2) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). Astronomers combined views from both cameras to obtain the true ages of the stars surrounding each galaxy's bulge. The Hubble telescope's sharper resolution allows astronomers to study the intricate structure of a galaxy's core. The galaxies are ordered by the size of their bulges. NGC 5838, an 'S0' galaxy, is dominated by a large bulge and has no visible spiral arms; NGC 7537, an 'Sbc' galaxy, has a small bulge and loosely wound spiral arms. Astronomers think that the structure of NGC 7537 is very similar to our Milky Way. The galaxy images are composites made from WFPC2 images taken with blue (4445 Angstroms) and red (8269 Angstroms) filters, and NICMOS images taken in the infrared (16,000 Angstroms). They were taken in June, July, and August of 1997. Credits for the ground-based images: Allan Sandage (The Observatories of the Carnegie Institution of Washington) and John Bedke (Computer Sciences Corporation and the Space Telescope Science Institute) Credits for WFPC2 and NICMOS composites: NASA, ESA, and Reynier Peletier (University of Nottingham, United Kingdom)

  12. LIFTING THE VEIL OF DUST TO REVEAL THE SECRETS OF SPIRAL GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have combined information from the NASA Hubble Space Telescope's visible- and infrared-light cameras to show the hearts of four spiral galaxies peppered with ancient populations of stars. The top row of pictures, taken by a ground-based telescope, represents complete views of each galaxy. The blue boxes outline the regions observed by the Hubble telescope. The bottom row represents composite pictures from Hubble's visible- and infrared-light cameras, the Wide Field and Planetary Camera 2 (WFPC2) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). Astronomers combined views from both cameras to obtain the true ages of the stars surrounding each galaxy's bulge. The Hubble telescope's sharper resolution allows astronomers to study the intricate structure of a galaxy's core. The galaxies are ordered by the size of their bulges. NGC 5838, an 'S0' galaxy, is dominated by a large bulge and has no visible spiral arms; NGC 7537, an 'Sbc' galaxy, has a small bulge and loosely wound spiral arms. Astronomers think that the structure of NGC 7537 is very similar to our Milky Way. The galaxy images are composites made from WFPC2 images taken with blue (4445 Angstroms) and red (8269 Angstroms) filters, and NICMOS images taken in the infrared (16,000 Angstroms). They were taken in June, July, and August of 1997. Credits for the ground-based images: Allan Sandage (The Observatories of the Carnegie Institution of Washington) and John Bedke (Computer Sciences Corporation and the Space Telescope Science Institute) Credits for WFPC2 and NICMOS composites: NASA, ESA, and Reynier Peletier (University of Nottingham, United Kingdom)

  13. The First Billion Years project: constraining the dust attenuation law of star-forming galaxies at z ≃ 5

    NASA Astrophysics Data System (ADS)

    Cullen, F.; McLure, R. J.; Khochfar, S.; Dunlop, J. S.; Dalla Vecchia, C.

    2017-09-01

    We present the results of a study investigating the dust attenuation law at z ≃ 5, based on synthetic spectral energy distributions (SEDs) calculated for a sample of N = 498 galaxies drawn from the First Billion Years (FiBY) simulation project. The simulated galaxies at z ≃ 5, which have M1500 ≤ -18.0 and 7.5 ≤ log(M/M}_{⊙}) ≤ 10.2, display a mass-dependent α-enhancement, with a median value of [α /{Fe}]_{z=5} ˜eq 4 × [α /{Fe}]_{Z_{⊙}}. The median Fe/H ratio of the simulated galaxies is 0.14 ± 0.05 which produces steep intrinsic ultraviolet (UV) continuum slopes; 〈βi〉 = -2.4 ± 0.05. Using a set of simple dust attenuation models, in which the wavelength-dependent attenuation is assumed to be of the form A(λ) ∝ λn, we explore the parameter values which best reproduce the observed z = 5 luminosity function (LF) and colour-magnitude relation (CMR). We find that a simple model in which the absolute UV attenuation is a linearly increasing function of log stellar mass (A1500 = 0.5 × log(M/M⊙) - 3.3), and the dust attenuation slope (n) is within the range -0.7 ≤ n ≤ -0.3, can successfully reproduce the LF and CMR over a wide range of stellar population synthesis model assumptions, including the effects of massive binaries. This range of attenuation curves is consistent with a power-law fit to the Calzetti attenuation law in the UV (n = -0.55). In contrast, curves as steep as the Small Magellanic Cloud extinction curve (n = -1.24) are formally ruled out. Finally, we show that our models are consistent with recent 1.3 mm Atacama Large Millimeter Array observations of the Hubble Ultra Deep Field, and predict the form of the z ≃ 5 infrared excess (IRX)-β relation.

  14. Spatial Correlation between Dust and Hα Emission in Dwarf Irregular Galaxies

    NASA Astrophysics Data System (ADS)

    Jimmy; Tran, Kim-Vy; Saintonge, Amélie; Accurso, Gioacchino; Brough, Sarah; Oliva-Altamirano, Paola; Salmon, Brett; Forrest, Ben

    2016-07-01

    Using a sample of dwarf irregular galaxies selected from the ALFALFA blind H i-survey and observed using the VIMOS IFU, we investigate the relationship between Hα emission and Balmer optical depth ({τ }{{b}}). We find a positive correlation between Hα luminosity surface density and Balmer optical depth in 8 of 11 at ≥0.8σ significance (6 of 11 at ≥1.0σ) galaxies. Our spaxels have physical scales ranging from 30 to 80 pc, demonstrating that the correlation between these two variables continues to hold down to spatial scales as low as 30 pc. Using the Spearman’s rank correlation coefficient to test for correlation between {{{Σ }}}{{H}α } and {τ }{{b}} in all the galaxies combined, we find ρ =0.39, indicating a positive correlation at 4σ significance. Our low stellar-mass galaxy results are in agreement with observations of emission line regions in larger spiral galaxies, indicating that this relationship is independent of the size of the galaxy hosting the emission line region. The positive correlation between Hα luminosity and Balmer optical depth within spaxels is consistent with the hypothesis that young star-forming regions are surrounded by dusty birth-clouds. Based on VLT service mode observations (Programs 081.B-0649 and 083.B-0662) gathered at the European Southern Observatory, Chile.

  15. A sub-millimetre survey of dust enshrouded galaxies in the Hubble Deep Field region

    NASA Astrophysics Data System (ADS)

    Borys, Colin James Kelvin

    This thesis investigates the emission of sub-millimetre- wave radiation from galaxies in the Hubble Deep Field North region. The data were obtained from dedicated observing runs from our group and others using the SCUBA camera on the James Clerk Maxwell Telescope. The data were combined using techniques specifically developed here for low signal-to-noise source recovery. The sources found represent over 10% of all cosmological sources SCUBA has detected since it was commissioned. The number of sub-mm galaxies we detect account for a significant fraction of the sub-mm back-ground, and we show that mild extrapolations can reproduce it entirely. We comment on their clustering properties, both with themselves and other high-redshift galaxy types. A multi-wavelength analysis of these galaxies shows that SCUBA sources do not all have similar properties, and are made of a collection including: star-forming radio galaxies; optically invisible objects; active galactic nuclei; and extremely red objects. Reasonable attempts to determine the redshift distribution of the sample show that SCUBA galaxies have a median redshift of around 2, and suggest that the global star formation rate may be dominated by such objects at redshifts beyond about 1. The thesis summarises the current state of extra-galactic sub-mm astronomy, and comments on how new surveys and detectors will allow us to place stronger constraints on the evolution properties of the high-redshift Universe.

  16. The Origins of UV-optical Color Gradients in Star-forming Galaxies at z ˜ 2: Predominant Dust Gradients but Negligible sSFR Gradients

    NASA Astrophysics Data System (ADS)

    Liu, F. S.; Jiang, Dongfei; Faber, S. M.; Koo, David C.; Yesuf, Hassen M.; Tacchella, Sandro; Mao, Shude; Wang, Weichen; Guo, Yicheng; Fang, Jerome J.; Barro, Guillermo; Zheng, Xianzhong; Jia, Meng; Tong, Wei; Liu, Lu; Meng, Xianmin

    2017-07-01

    The rest-frame UV-optical (i.e., NUV - B) color is sensitive to both low-level recent star formation (specific star formation rate—sSFR) and dust. In this Letter, we extend our previous work on the origins of NUV - B color gradients in star-forming galaxies (SFGs) at z˜ 1 to those at z˜ 2. We use a sample of 1335 large (semimajor axis radius {R}{SMA}> 0\\buildrel{\\prime\\prime}\\over{.} 18) SFGs with extended UV emission out to 2{R}{SMA} in the mass range {M}* ={10}9{--}{10}11 {M}⊙ at 1.5< z< 2.8 in the CANDELS/GOODS-S and UDS fields. We show that these SFGs generally have negative NUV - B color gradients (redder centers), and their color gradients strongly increase with galaxy mass. We also show that the global rest-frame FUV - NUV color is approximately linear with {A}{{V}}, which is derived by modeling the observed integrated FUV to NIR spectral energy distributions of the galaxies. Applying this integrated calibration to our spatially resolved data, we find a negative dust gradient (more dust extinguished in the centers), which steadily becomes steeper with galaxy mass. We further find that the NUV - B color gradients become nearly zero after correcting for dust gradients regardless of galaxy mass. This indicates that the sSFR gradients are negligible and dust reddening is likely the principal cause of negative UV-optical color gradients in these SFGs. Our findings support that the buildup of the stellar mass in SFGs at Cosmic Noon is self-similar inside 2{R}{SMA}.

  17. Extended Red Emission in the Evil Eye Galaxy

    NASA Astrophysics Data System (ADS)

    Pierini, D.; Majeed, A.; Boroson, T. A.; Witt, A. N.

    2001-05-01

    The Evil Eye Galaxy (NGC 4826) is a nearby galaxy with an asymmetrically placed, strongly absorbing dust lane across its prominent bulge, associated to an active star formation (SF) region. We obtained accurate low--resolution (4.2 Å/pixel) spectroscopy (KPNO 4-m) of NGC 4826 in the wavelength range 5300--9100Å with a slit of 4.4' length, positioned across the nucleus of the galaxy and encompassing its bulge size. We were able to study the wavelength dependent effects of absorption and scattering by the dust by comparing the stellar SEDs at corresponding positions on the bulge, symmetrically placed with respect to the nucleus, under the assumption that the intrinsic (i.e. unobscured by the dust lane) ISRF is radially symmetric, except for the ongoing SF region. We report on the detection of strong extended red emission (ERE) from the dust lane of NGC 4826 within a radial distance of about 15{' '} from its nucleus, adjacent to the active SF region. At the nucleus, the ERE band extends from about 5800 Å to 9100 Å, with peak near 8300 Å, and the ERE-to-scattered light integrated intensity ratio is about 0.7. At farther distances, approaching the ongoing SF region, the ERE band and peak shift to longer wavelengths, while the integrated ERE intensity diminishes and, finally, vanishes there. The H α line intensity and the index [NII]λ 6583/H α constrain the Lyman continuum photon rate and the effective temperatures of the OB association stars. The ERE-to-scattered light ratio decreases as well but shows a secondary maximum where the opacity of the dust lane peaks. We interpret the ERE nature as photoluminescence by nanometer--sized clusters, illuminated by UV/visible photons of the local radiation field. When examined within the context of ERE observations in the diffuse ISM of our Galaxy and in a variety of other dusty environments, we conclude that the ERE photon conversion efficiency in NGC 4826 is as high as found elsewhere, but that the characteristic size

  18. The Herschel Exploitation of Local Galaxy Andromeda (HELGA). II. Dust and Gas in Andromeda

    NASA Astrophysics Data System (ADS)

    Smith, M. W. L.; Eales, S. A.; Gomez, H. L.; Roman-Duval, J.; Fritz, J.; Braun, R.; Baes, M.; Bendo, G. J.; Blommaert, J. A. D. L.; Boquien, M.; Boselli, A.; Clements, D. L.; Cooray, A. R.; Cortese, L.; De Looze, I.; Ford, G. P.; Gear, W. K.; Gentile, G.; Gordon, K. D.; Kirk, J.; Lebouteiller, V.; Madden, S.; Mentuch, E.; O'Halloran, B.; Page, M. J.; Schulz, B.; Spinoglio, L.; Verstappen, J.; Wilson, C. D.; Thilker, D. A.

    2012-09-01

    We present an analysis of the dust and gas in Andromeda, using Herschel images sampling the entire far-infrared peak. We fit a modified-blackbody model to ~4000 quasi-independent pixels with spatial resolution of ~140 pc and find that a variable dust-emissivity index (β) is required to fit the data. We find no significant long-wavelength excess above this model, suggesting there is no cold dust component. We show that the gas-to-dust ratio varies radially, increasing from ~20 in the center to ~70 in the star-forming ring at 10 kpc, consistent with the metallicity gradient. In the 10 kpc ring the average β is ~1.9, in good agreement with values determined for the Milky Way (MW). However, in contrast to the MW, we find significant radial variations in β, which increases from 1.9 at 10 kpc to ~2.5 at a radius of 3.1 kpc and then decreases to 1.7 in the center. The dust temperature is fairly constant in the 10 kpc ring (ranging from 17 to 20 K), but increases strongly in the bulge to ~30 K. Within 3.1 kpc we find the dust temperature is highly correlated with the 3.6 μm flux, suggesting the general stellar population in the bulge is the dominant source of dust heating there. At larger radii, there is a weak correlation between the star formation rate and dust temperature. We find no evidence for "dark gas" in M31 in contrast to recent results for the MW. Finally, we obtained an estimate of the CO X-factor by minimizing the dispersion in the gas-to-dust ratio, obtaining a value of (1.9 ± 0.4) × 1020 cm-2 [K km s-1]-1. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  19. Lyα Profile, Dust, and Prediction of Lyα Escape Fraction in Green Pea Galaxies

    NASA Astrophysics Data System (ADS)

    Yang, Huan; Malhotra, Sangeeta; Gronke, Max; Rhoads, James E.; Leitherer, Claus; Wofford, Aida; Jiang, Tianxing; Dijkstra, Mark; Tilvi, V.; Wang, Junxian

    2017-08-01

    We studied Lyman-α (Lyα) escape in a statistical sample of 43 Green Peas with HST/COS Lyα spectra. Green Peas are nearby star-forming galaxies with strong [O iii]λ5007 emission lines. Our sample is four times larger than the previous sample and covers a much more complete range of Green Pea properties. We found that about two-thirds of Green Peas are strong Lyα line emitters with rest-frame Lyα equivalent width > 20 \\mathringA . The Lyα profiles of Green Peas are diverse. The Lyα escape fraction, defined as the ratio of observed Lyα flux to intrinsic Lyα flux, shows anti-correlations with a few Lyα kinematic features—both the blue peak and red peak velocities, the peak separations, and the FWHM of the red portion of the Lyα profile. Using properties measured from Sloan Digital Sky Survey optical spectra, we found many correlations—the Lyα escape fraction generally increases at lower dust reddening, lower metallicity, lower stellar mass, and higher [O iii]/[O ii] ratio. We fit their Lyα profiles with the H i shell radiative transfer model and found that the Lyα escape fraction is anti-correlated with the best-fit N H i . Finally, we fit an empirical linear relation to predict {f}{esc}{Lyα } from the dust extinction and Lyα red peak velocity. The standard deviation of this relation is about 0.3 dex. This relation can be used to isolate the effect of intergalactic medium (IGM) scatterings from Lyα escape and to probe the IGM optical depth along the line of sight of each z> 7 Lyα emission-line galaxy in the James Webb Space Telescope era.

  20. ALMA observation of 158 μm [C II] line and dust continuum of a z = 7 normally star-forming galaxy in the epoch of reionization

    SciTech Connect

    Ota, Kazuaki; Walter, Fabian; Da Cunha, Elisabete; González-López, Jorge; Decarli, Roberto; Hodge, Jacqueline A.; Ohta, Kouji; Hatsukade, Bunyo; Nagai, Hiroshi; Iye, Masanori; Kashikawa, Nobunari; Carilli, Chris L.; Egami, Eiichi; Jiang, Linhua; Riechers, Dominik A.; Bertoldi, Frank; Cox, Pierre; Neri, Roberto; Weiss, Axel

    2014-09-01

    We present ALMA observations of the [C II] line and far-infrared (FIR) continuum of a normally star-forming galaxy in the reionization epoch, the z = 6.96 Lyα emitter (LAE) IOK-1. Probing to sensitivities of σ{sub line} = 240 μJy beam{sup –1} (40 km s{sup –1} channel) and σ{sub cont} = 21 μJy beam{sup –1}, we found the galaxy undetected in both [C II] and continuum. Comparison of ultraviolet (UV)-FIR spectral energy distribution (SED) of IOK-1, including our ALMA limit, with those of several types of local galaxies (including the effects of the cosmic microwave background, CMB, on the FIR continuum) suggests that IOK-1 is similar to local dwarf/irregular galaxies in SED shape rather than highly dusty/obscured galaxies. Moreover, our 3σ FIR continuum limit, corrected for CMB effects, implies intrinsic dust mass M {sub dust} < 6.4 × 10{sup 7} M {sub ☉}, FIR luminosity L {sub FIR} < 3.7 × 10{sup 10} L {sub ☉} (42.5-122.5 μm), total IR luminosity L {sub IR} < 5.7 × 10{sup 10} L {sub ☉} (8-1000 μm), and dust-obscured star formation rate (SFR) < 10 M {sub ☉} yr{sup –1}, if we assume that IOK-1 has a dust temperature and emissivity index typical of local dwarf galaxies. This SFR is 2.4 times lower than one estimated from the UV continuum, suggesting that <29% of the star formation is obscured by dust. Meanwhile, our 3σ [C II] flux limit translates into [C II] luminosity, L {sub [C} {sub II]} < 3.4 × 10{sup 7} L {sub ☉}. Locations of IOK-1 and previously observed LAEs on the L {sub [C} {sub II]} versus SFR and L {sub [C} {sub II]}/L {sub FIR} versus L {sub FIR} diagrams imply that LAEs in the reionization epoch have significantly lower gas and dust enrichment than AGN-powered systems and starbursts at similar/lower redshifts, as well as local star-forming galaxies.

  1. GOODS-Herschel: Star Formation, Dust Attenuation, and the FIR-radio Correlation on the Main Sequence of Star-forming Galaxies up to z ≃4

    NASA Astrophysics Data System (ADS)

    Pannella, M.; Elbaz, D.; Daddi, E.; Dickinson, M.; Hwang, H. S.; Schreiber, C.; Strazzullo, V.; Aussel, H.; Bethermin, M.; Buat, V.; Charmandaris, V.; Cibinel, A.; Juneau, S.; Ivison, R. J.; Le Borgne, D.; Le Floc'h, E.; Leiton, R.; Lin, L.; Magdis, G.; Morrison, G. E.; Mullaney, J.; Onodera, M.; Renzini, A.; Salim, S.; Sargent, M. T.; Scott, D.; Shu, X.; Wang, T.

    2015-07-01

    We use deep panchromatic data sets in the GOODS-N field, from GALEX to the deepest Herschel far-infrared (FIR) and VLA radio continuum imaging, to explore the evolution of star-formation activity and dust attenuation properties of star-forming galaxies to z ≃ 4, using mass-complete samples. Our main results can be summarized as follows: (i) the slope of the star-formation rate-M* correlation is consistent with being constant ≃0.8 up to z ≃ 1.5, while its normalization keeps increasing with redshift; (ii) for the first time we are able to explore the FIR-radio correlation for a mass-selected sample of star-forming galaxies: the correlation does not evolve up to z ≃ 4; (iii) we confirm that galaxy stellar mass is a robust proxy for UV dust attenuation in star-forming galaxies, with more massive galaxies being more dust attenuated. Strikingly, we find that this attenuation relation evolves very weakly with redshift, with the amount of dust attenuation increasing by less than 0.3 mag over the redshift range [0.5-4] for a fixed stellar mass; (iv) the correlation between dust attenuation and the UV spectral slope evolves with redshift, with the median UV slope becoming bluer with redshift. By z ≃ 3, typical UV slopes are inconsistent, given the measured dust attenuations, with the predictions of commonly used empirical laws. (v) Finally, building on existing results, we show that gas reddening is marginally larger (by a factor of around 1.3) than the stellar reddening at all redshifts probed. Our results support a scenario where the ISM conditions of typical star-forming galaxies evolve with redshift, such that at z ≥ 1.5 Main Sequence galaxies have ISM conditions moving closer to those of local starbursts. Based on observations collected at the Herschel, Spitzer, Keck, NRAO-VLA, Subaru, KPNO, and CFHT observatories. Herschel is an European Space Agency Cornerstone Mission with science instruments provided by European-led Principal Investigator consortia and

  2. ALMA Observation of 158 μm [C II] Line and Dust Continuum of a z = 7 Normally Star-forming Galaxy in the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Ota, Kazuaki; Walter, Fabian; Ohta, Kouji; Hatsukade, Bunyo; Carilli, Chris L.; da Cunha, Elisabete; González-López, Jorge; Decarli, Roberto; Hodge, Jacqueline A.; Nagai, Hiroshi; Egami, Eiichi; Jiang, Linhua; Iye, Masanori; Kashikawa, Nobunari; Riechers, Dominik A.; Bertoldi, Frank; Cox, Pierre; Neri, Roberto; Weiss, Axel

    2014-09-01

    We present ALMA observations of the [C II] line and far-infrared (FIR) continuum of a normally star-forming galaxy in the reionization epoch, the z = 6.96 Lyα emitter (LAE) IOK-1. Probing to sensitivities of σline = 240 μJy beam-1 (40 km s-1 channel) and σcont = 21 μJy beam-1, we found the galaxy undetected in both [C II] and continuum. Comparison of ultraviolet (UV)-FIR spectral energy distribution (SED) of IOK-1, including our ALMA limit, with those of several types of local galaxies (including the effects of the cosmic microwave background, CMB, on the FIR continuum) suggests that IOK-1 is similar to local dwarf/irregular galaxies in SED shape rather than highly dusty/obscured galaxies. Moreover, our 3σ FIR continuum limit, corrected for CMB effects, implies intrinsic dust mass M dust < 6.4 × 107 M ⊙, FIR luminosity L FIR < 3.7 × 1010 L ⊙ (42.5-122.5 μm), total IR luminosity L IR < 5.7 × 1010 L ⊙ (8-1000 μm), and dust-obscured star formation rate (SFR) < 10 M ⊙ yr-1, if we assume that IOK-1 has a dust temperature and emissivity index typical of local dwarf galaxies. This SFR is 2.4 times lower than one estimated from the UV continuum, suggesting that <29% of the star formation is obscured by dust. Meanwhile, our 3σ [C II] flux limit translates into [C II] luminosity, L [C II] < 3.4 × 107 L ⊙. Locations of IOK-1 and previously observed LAEs on the L [C II] versus SFR and L [C II]/L FIR versus L FIR diagrams imply that LAEs in the reionization epoch have significantly lower gas and dust enrichment than AGN-powered systems and starbursts at similar/lower redshifts, as well as local star-forming galaxies. Based in part on data collected with the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc

  3. A sub-millimetre survey of dust enshrouded galaxies in the Hubble Deep Field North region

    NASA Astrophysics Data System (ADS)

    Borys, C. J.

    2002-12-01

    This thesis investigates the emission of sub-millimetre-wave radiation from galaxies in the Hubble Deep Field North region. The data were obtained from dedicated observing runs from our group and others using the SCUBA camera on the James Clerk Maxwell Telescope. The data were combined using techniques specifically developed here for low signal-to-noise source recovery. The sources found represent over 10% of all cosmological sources SCUBA has detected since it was commissioned. The number of sub-mm galaxies we detect account for a significant fraction of the sub-mm background, and we show that mild extrapolations can reproduce it entirely. We comment on their clustering properties, both with themselves and other high-redshift galaxy types. A multi-wavelength analysis of these galaxies shows that SCUBA sources do not all have similar properties, and are made of a collection including: star-forming radio galaxies; optically invisible objects; active galactic nuclei; and extremely red objects. Reasonable attempts to determine the redshift distribution of the sample show that SCUBA galaxies have a median redshift of around 2, and suggest that the global star formation rate may be dominated by such objects at redshifts beyond about 1. The thesis summarises the current state of extra-galactic sub-mm astronomy, and comments on how new surveys and detectors will allow us to place stronger constraints on the evolution properties of the high-redshift Universe. The research described here was made possible from grants by the Natural Science and Engineering Research Council of Canada, and a generous scholarship from the University of British Columbia.

  4. HIGH-REDSHIFT DUST OBSCURED GALAXIES: A MORPHOLOGY-SPECTRAL ENERGY DISTRIBUTION CONNECTION REVEALED BY KECK ADAPTIVE OPTICS

    SciTech Connect

    Melbourne, J.; Matthews, K.; Soifer, B. T. E-mail: bts@submm.caltech.edu

    2009-06-15

    A simple optical to mid-IR color selection, R - [24]>14, i.e., f {sub {nu}}(24 {mu}m)/f {sub {nu}}(R) {approx}> 1000, identifies highly dust obscured galaxies (DOGs) with typical redshifts of z {approx} 2 {+-} 0.5. Extreme mid-IR luminosities (L {sub IR} > 10{sup 12-14}) suggest that DOGs are powered by a combination of active galactic nuclei (AGNs) and star formation, possibly driven by mergers. In an effort to compare their photometric properties with their rest-frame optical morphologies, we obtained high-spatial resolution (0.''05-0.''1) Keck Adaptive Optics K'-band images of 15 DOGs. The images reveal a wide range of morphologies, including small exponential disks (eight of 15), small ellipticals (four of 15), and unresolved sources (two of 15). One particularly diffuse source could not be classified because of low signal-to-noise ratio. We find a statistically significant correlation between galaxy concentration and mid-IR luminosity, with the most luminous DOGs exhibiting higher concentration and smaller physical size. DOGs with high concentration also tend to have spectral energy distributions (SEDs) suggestive of AGN activity. Thus, central AGN light may be biasing the morphologies of the more luminous DOGs to higher concentration. Conversely, more diffuse DOGs tend to show an SED shape suggestive of star formation. Two of 15 in the sample show multiple resolved components with separations of {approx}1 kpc, circumstantial evidence for ongoing mergers.

  5. Sombrero Galaxy (M104) in Infrared Light

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The razor sharp eye of the Hubble Space Telescope (HST) easily resolves the Sombrero galaxy, Messier 104 (M104). 50,000 light-years across, the galaxy is located 28 million light-years from Earth at the southern edge of the rich Virgo cluster of galaxies. Equivalent to 800 billion suns, Sombrero is one of the most massive objects in that group. The hallmark of Sombrero is a brilliant white, bulbous core encircled by the thick dust lanes comprising the spiral structure of the galaxy. As seen from Earth, the galaxy is tilted nearly edge-on. We view it from just six degrees north of its equatorial plane. This rich system of globular clusters is estimated to be nearly 2,000 in number which is 10 times as many as in our Milky Way galaxy. Similar to the clusters in the Milky Way, the ages range from 10-13 billion years old. Embedded in the bright core of M104 is a smaller disk, which is tilted relative to the large disk. The HST paired with the Spitzer infrared telescope, offers this striking composite capturing the magnificence of the Sombrero galaxy. In the Hubble view, the galaxy resembles a broad-rimmed Mexican hat, whereas in the Spitzer striking infrared view, the galaxy looks more like a bulls eye. The full view provided by Spitzer shows the disk is warped, which is often the result of a gravitational encounter with another galaxy, and clumpy areas spotted in the far edges of the ring indicate young star forming regions. Spitzer detected infrared emission not only from the ring, but from the center of the galaxy as well, where there is a huge black hole believed to be a billion times more massive than our Sun. The Marshall Space Flight Center (MSFC) had responsibility for design, development, and construction of the HST.

  6. DUST ATTENUATION OF THE NEBULAR REGIONS OF z ∼ 2 STAR-FORMING GALAXIES: INSIGHT FROM UV, IR, AND EMISSION LINES

    SciTech Connect

    De Barros, S.; Reddy, N.; Shivaei, I.

    2016-04-01

    We use a sample of 149 spectroscopically confirmed UV-selected galaxies at z ∼ 2 to investigate the relative dust attenuation of the stellar continuum and the nebular emission lines. For each galaxy in the sample, at least one rest-frame optical emission line (Hα/[N ii] λ6583 or [O iii] λ5007) measurement has been taken from the litterature, and 41 galaxies have additional Spitzer/MIPS 24 μm observations that are used to infer infrared luminosities. We use a spectral energy distribution (SED) fitting code that predicts nebular line strengths when fitting the stellar populations of galaxies in our sample, and we perform comparisons between the predictions of our models and the observed/derived physical quantities. We find that on average our code is able to reproduce all the physical quantities (e.g., UV β slopes, infrared luminosities, emission line fluxes), but we need to apply a higher dust correction to the nebular emission compared to the stellar emission for the largest star formation rate (SFR) (log SFR/M{sub ⊙} yr{sup −1} > 1.82, Salpeter initial mass function). We find a correlation between SFR and the difference in nebular and stellar color excesses, which could resolve the discrepant results regarding nebular dust correction at z ∼ 2 from previous studies.

  7. Bright [C ii] and Dust Emission in Three z > 6.6 Quasar Host Galaxies Observed by ALMA

    NASA Astrophysics Data System (ADS)

    Venemans, Bram P.; Walter, Fabian; Zschaechner, Laura; Decarli, Roberto; De Rosa, Gisella; Findlay, Joseph R.; McMahon, Richard G.; Sutherland, Will J.

    2016-01-01

    We present ALMA detections of the [C ii] 158 μm emission line and the underlying far-infrared (FIR) continuum of three quasars at 6.6 < z < 6.9 selected from the VIKING survey. The [C ii] line fluxes range between 1.6 and 3.4 Jy km s-1 ([C ii] luminosities ˜(1.9-3.9) × 109 L⊙). We measure continuum flux densities of 0.56-3.29 mJy around 158 μm (rest frame), with implied FIR luminosities of (0.6-7.5) × 1012 L⊙ and dust masses Md = (0.7-24) × 108 M⊙. In one quasar we derive a dust temperature of {30}-9+12 K from the continuum slope, below the canonical value of 47 K. Assuming that the [C ii] and continuum emission are powered by star formation, we find star formation rates from 100 to 1600 M⊙ yr-1 based on local scaling relations. The L[C ii]/LFIR ratios in the quasar hosts span a wide range from (0.3-4.6) × 10-3, including one quasar with a ratio that is consistent with local star-forming galaxies. We find that the strength of the L[C ii] and 158 μm continuum emission in z ≳ 6 quasar hosts correlates with the quasar’s bolometric luminosity. In one quasar, the [C ii] line is significantly redshifted by ˜1700 km s-1 with respect to the Mg ii broad emission line. Comparing to values in the literature, we find that, on average, the Mg ii is blueshifted by 480 km s-1 (with a standard deviation of 630 km s-1) with respect to the host galaxy redshift, i.e., one of our quasars is an extreme outlier. Through modeling we can rule out a flat rotation curve for our brightest [C ii] emitter. Finally, we find that the ratio of black hole mass to host galaxy (dynamical) mass is higher by a factor of 3-4 (with significant scatter) than local relations.

  8. On the location and composition of the dust in the MCG-6-30-15 warm absorber

    NASA Astrophysics Data System (ADS)

    Ballantyne, D. R.; Weingartner, J. C.; Murray, N.

    2003-10-01

    The warm absorber observed in the Seyfert 1 galaxy MCG-6-30-15 is known to consist of at least two zones and very likely contains dust. Hubble Space Telescope images of MCG-6-30-15 show a dust lane crossing the galaxy just below the nucleus. In this paper, we argue that this dust lane is responsible for the observed reddening of the nuclear emission and the Fe I edge hinted at in the Chandra spectrum of MCG-6-30-15. We further suggest that the gas within the dust lane can comprise much of the low ionization component (i.e., the one contributing the O VII edge) of the observed warm absorber. Moreover, placing the warm absorbing material at such distances (hundreds of pc) can account for the small outflow velocities of the low ionization absorption lines as well as the constancy of the O VII edge. Photoionization models of a dusty interstellar gas cloud (with a column appropriate for the reddening toward MCG-6-30-15) using a toy Seyfert 1 spectral energy distribution show that it is possible to obtain a significant O VII edge (tau ~ 0.2) if the material is ~ 150 pc from the ionizing source. For MCG-6-30-15, such a distance is consistent with the observed dust lane. We emphasize the point first made by Kraemer et al.: dusty interstellar material will likely contribute to the warm absorber, and should be included in spectral modeling. The current data on MCG-6-30-15 is unable to constrain the dust composition within the warm absorber. Astronomical silicate is a viable candidate, but there are indications of a very low O abundance in the dust, which is inconsistent with a silicate origin. If true, this may indicate that there were repeated cycles of grain destruction and growth from shocks in the interstellar medium of MCG-6-30-15. Pure iron grains are an unlikely dust constituent due to the limit on their abundance in the Galaxy, yet they cannot be ruled out. The high column densities inferred from the highly ionized zone of the warm absorber implies that this gas is

  9. UVI colour gradients of 0.4 < z < 1.4 star-forming main-sequence galaxies in CANDELS: dust extinction and star formation profiles

    NASA Astrophysics Data System (ADS)

    Wang, Weichen; Faber, S. M.; Liu, F. S.; Guo, Yicheng; Pacifici, Camilla; Koo, David C.; Kassin, Susan A.; Mao, Shude; Fang, Jerome J.; Chen, Zhu; Koekemoer, Anton M.; Kocevski, Dale D.; Ashby, M. L. N.

    2017-08-01

    This paper uses radial colour profiles to infer the distributions of dust, gas and star formation in z = 0.4-1.4 star-forming main-sequence galaxies. We start with the standard UVJ-based method to estimate dust extinction and specific star formation rate (sSFR). By replacing J with I band, a new calibration method suitable for use with ACS+WFC3 data is created (i.e. UVI diagram). Using a multi-wavelength multi-aperture photometry catalogue based on CANDELS (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey), UVI colour profiles of 1328 galaxies are stacked in stellar mass and redshift bins. The resulting colour gradients, covering a radial range of 0.2-2.0 effective radii, increase strongly with galaxy mass and with global AV. Colour gradient directions are nearly parallel to the Calzetti extinction vector, indicating that dust plays a more important role than stellar population variations. With our calibration, the resulting AV profiles fall much more slowly than stellar mass profiles over the measured radial range. sSFR gradients are nearly flat without central quenching signatures, except for M⋆ > 1010.5 M⊙, where central declines of 20-25 per cent are observed. Both sets of profiles agree well with previous radial sSFR and (continuum) AV measurements. They are also consistent with the sSFR profiles and, if assuming a radially constant gas-to-dust ratio, gas profiles in recent hydrodynamic models. We finally discuss the striking findings that SFR scales with stellar mass density in the inner parts of galaxies, and that dust content is high in the outer parts despite low stellar mass surface densities there.

  10. How Dead are Dead Galaxies? Mid-Infrared Fluxes of Quiescent Galaxies at Redshift 0.3< Z< 2.5: Implications for Star Formation Rates and Dust Heating

    NASA Technical Reports Server (NTRS)

    Fumagalli, Mattia; Labbe, Ivo; Patel, Shannon G.; Franx, Marijn; vanDokkum, Pieter; Brammer, Gabriel; DaCunha, Elisabete; FoersterSchreiber, Natascha M.; Kriek, Mariska; Quadri, Ryan; hide

    2013-01-01

    We investigate star formation rates of quiescent galaxies at high redshift (0.3 < z < 2.5) using 3D-HST WFC3 grism spectroscopy and Spitzer mid-infrared data. We select quiescent galaxies on the basis of the widely used UVJ color-color criteria. Spectral energy distribution fitting (rest frame optical and near-IR) indicates very low star formation rates for quiescent galaxies (sSFR approx. 10(exp -12)/yr. However, SED fitting can miss star formation if it is hidden behind high dust obscuration and ionizing radiation is re-emitted in the mid-infrared. It is therefore fundamental to measure the dust-obscured SFRs with a mid-IR indicator. We stack the MIPS-24 micron images of quiescent objects in five redshift bins centered on z = 0.5, 0.9, 1.2, 1.7, 2.2 and perform aperture photometry. Including direct 24 micron detections, we find sSFR approx. 10(exp -11.9) × (1 + z)(sup 4)/yr. These values are higher than those indicated by SED fitting, but at each redshift they are 20-40 times lower than those of typical star forming galaxies. The true SFRs of quiescent galaxies might be even lower, as we show that the mid-IR fluxes can be due to processes unrelated to ongoing star formation, such as cirrus dust heated by old stellar populations and circumstellar dust. Our measurements show that star formation quenching is very efficient at every redshift. The measured SFR values are at z > 1.5 marginally consistent with the ones expected from gas recycling (assuming that mass loss from evolved stars refuels star formation) and well above that at lower redshifts.

  11. How dead are dead galaxies? Mid-infrared fluxes of quiescent galaxies at redshift 0.3 < z < 2.5: implications for star formation rates and dust heating

    SciTech Connect

    Fumagalli, Mattia; Labbé, Ivo; Patel, Shannon G.; Franx, Marijn; Van Dokkum, Pieter; Momcheva, Ivelina; Nelson, Erica; Brammer, Gabriel; Da Cunha, Elisabete; Rix, Hans-Walter; Maseda, Michael; Schreiber, Natascha M. Förster; Kriek, Mariska; Quadri, Ryan; Wake, David; Lundgren, Britt; Whitaker, Katherine E.; Marchesini, Danilo; Pacifici, Camilla; Skelton, Rosalind E.

    2014-11-20

    We investigate star formation rates (SFRs) of quiescent galaxies at high redshift (0.3 < z < 2.5) using 3D-HST WFC3 grism spectroscopy and Spitzer mid-infrared data. We select quiescent galaxies on the basis of the widely used UVJ color-color criteria. Spectral energy distribution (SED) fitting (rest-frame optical and near-IR) indicates very low SFRs for quiescent galaxies (sSFR ∼ 10{sup –12} yr{sup –1}). However, SED fitting can miss star formation if it is hidden behind high dust obscuration and ionizing radiation is re-emitted in the mid-infrared. It is therefore fundamental to measure the dust-obscured SFRs with a mid-IR indicator. We stack the MIPS 24 μm images of quiescent objects in five redshift bins centered on z = 0.5, 0.9, 1.2, 1.7, 2.2 and perform aperture photometry. Including direct 24 μm detections, we find sSFR ∼ 10{sup –11.9} × (1 + z){sup 4} yr{sup –1}. These values are higher than those indicated by SED fitting, but at each redshift they are 20-40 times lower than those of typical star-forming galaxies. The true SFRs of quiescent galaxies might be even lower, as we show that the mid-IR fluxes can be due to processes unrelated to ongoing star formation, such as cirrus dust heated by old stellar populations and circumstellar dust. Our measurements show that star formation quenching is very efficient at every redshift. The measured SFR values are at z > 1.5 marginally consistent with the ones expected from gas recycling (assuming that mass loss from evolved stars refuels star formation) and well below that at lower redshifts.

  12. DUSTiNGS. III. Distribution of Intermediate-age and Old Stellar Populations in Disks and Outer Extremities of Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    McQuinn, Kristen B. W.; Boyer, Martha L.; Mitchell, Mallory B.; Skillman, Evan D.; Gehrz, R. D.; Groenewegen, Martin A. T.; McDonald, Iain; Sloan, G. C.; van Loon, Jacco Th.; Whitelock, Patricia A.; Zijlstra, Albert A.

    2017-01-01

    We have traced the spatial distributions of intermediate-age and old stars in nine dwarf galaxies in the distant parts of the Local Group, using multi-epoch 3.6 and 4.5 μm data from the DUST in Nearby Galaxies with Spitzer (DUSTiNGS) survey. Using complementary optical imaging from the Hubble Space Telescope, we identify the tip of the red giant branch (TRGB) in the 3.6 μm photometry, separating thermally pulsating asymptotic giant branch stars from the larger red giant branch populations. Unlike the constant TRGB in the I band, at 3.6 μm, the TRGB magnitude varies by ˜0.7 mag, making it unreliable as a distance indicator. The intermediate-age and old stars are well mixed in two-thirds of the sample, with no evidence of a gradient in the ratio of the intermediate-age to old stellar populations outside the central ˜1‧-2‧. Variable AGB stars are detected in the outer extremities of the galaxies, indicating that chemical enrichment from these dust-producing stars may occur in the outer regions of galaxies with some frequency. Theories of structure formation in dwarf galaxies must account for the lack of radial gradients in intermediate-age populations and the presence of these stars in the outer extremities of dwarfs. Finally, we identify unique features in individual galaxies, such as extended tidal features in Sex A and Sag DIG and a central concentration of AGB stars in the inner regions of NGC 185 and NGC 147.

  13. ISM and dust properties of normal star-forming galaxies at z~2 derived by Herschel and ALMA with the help of gravitational lensing

    NASA Astrophysics Data System (ADS)

    Schaerer, Daniel; Boone, Frederic; Dessauges-Zavadsky, Miroslava; Sklias, Panos

    2015-08-01

    Using strong gravitational lensing provided by massive galaxy clusters we have studied a sample of normal star-forming galaxies at z~1.5-3 selected from the Herschel Lensing Survey (HLS). The observations include deep ground-based, HST, Spitzer, and Herschel imaging, plus LABOCA/SCUBA2 data, and IRAM CO observations.Targetted [CII] 158 micron observations of one z=2.013 galaxy from this sample were recently obtained with ALMA, resulting in the first detection of this important ISM cooling line in a faint LIRG (with LIR~1.e11 Lsun), which is magnified by a factor ~50.We discuss the behavior of [CII] and CO emission with other physical properties such as IR luminosity, dust temperature, galaxy metallicity, specific star formation rate, and many other quantities which are measured for our lensed galaxies. We also compare the z~2 data to nearby galaxies and to recent detections and upper limits of [CII] in z>6 Lyman break galaxies and Lyman alpha emitters.

  14. THE WYOMING SURVEY FOR H{alpha}. III. A MULTI-WAVELENGTH LOOK AT ATTENUATION BY DUST IN GALAXIES OUT TO z {approx} 0.4

    SciTech Connect

    Moore, Carolynn A.; Dale, Daniel A.; Barlow, Rebecca J.; Cohen, Seth A.; Cook, David O.; Johnson, L. C.; Kattner, ShiAnne M.; Staudaher, Shawn M.; Lee, Janice C.

    2010-07-15

    We report results from the Wyoming Survey for H{alpha} (WySH), a comprehensive four-square degree survey to probe the evolution of star-forming galaxies over the latter half of the age of the universe. We have supplemented the H{alpha} data from WySH with infrared data from the Spitzer Wide-area Infrared Extragalactic Survey and ultraviolet data from the Galaxy Evolution Explorer Deep Imaging Survey. This data set provides a multi-wavelength look at the evolution of the attenuation by dust, and here we compare a traditional measure of dust attenuation (L(TIR)/L(FUV)) to a diagnostic based on a recently developed robust star formation rate (SFR) indicator, [Ha{sub obs}+24{mu}m]/Ha{sub obs}. With such data over multiple epochs, the evolution in the attenuation by dust with redshift can be assessed. We present results from the ELAIS-N1 and Lockman Hole regions at z {approx} 0.16, 0.24, 0.32, and 0.40. While the ensemble averages of both diagnostics are relatively constant from epoch to epoch, each epoch individually exhibits a larger attenuation by dust for higher SFRs. Hence, an epoch-to-epoch comparison at a fixed SFR suggests a mild decrease in dust attenuation with redshift.

  15. Mid-infrared properties of luminous infrared galaxies. II. Probing the dust and gas physics of the goals sample

    SciTech Connect

    Stierwalt, S.; Armus, L.; Diaz-Santos, T.; Marshall, J.; Haan, S.; Howell, J.; Murphy, E. J.; Inami, H.; Petric, A. O.; Charmandaris, V.; Evans, A. S.; Iwasawa, K.; Kim, D. C.; Rich, J. A.; Spoon, H. W. W.; U, V.

    2014-08-01

    The Great Observatories All-sky LIRG Survey (GOALS) is a comprehensive, multiwavelength study of luminous infrared galaxies (LIRGs) in the local universe. Here, we present the results of a multi-component, spectral decomposition analysis of the low-resolution mid-infrared (MIR) Spitzer Infrared Spectrograph spectra from 5-38 μm of 244 LIRG nuclei. The detailed fits and high-quality spectra allow for characterization of the individual polycyclic aromatic hydrocarbon (PAH) features, warm molecular hydrogen emission, and optical depths for both silicate dust grains and water ices. We find that starbursting LIRGs, which make up the majority of the GOALS sample, are very consistent in their MIR properties (i.e., τ{sub 9.7μm}, τ{sub ice}, neon line ratios, and PAH feature ratios). However, as their EQW{sub 6.2{sub μm}} decreases, usually an indicator of an increasingly dominant active galactic nucleus (AGN), LIRGs cover a larger spread in these MIR parameters. The contribution from PAH emission to the total IR luminosity (L(PAH)/L(IR)) in LIRGs varies from 2%-29% and LIRGs prior to their first encounter show significantly higher L(PAH)/L(IR) ratios on average. We observe a correlation between the strength of the starburst (represented by IR8 = L{sub IR}/L{sub 8{sub μm}}) and the PAH fraction at 8 μm but no obvious link between IR8 and the 7.7 to 11.3 PAH ratio, suggesting that the fractional photodissociation region (PDR) emission, and not the overall grain properties, is associated with the rise in IR8 for galaxies off the starburst main sequence. We detect crystalline silicate features in ∼6% of the sample but only in the most obscure sources (s{sub 9.7{sub μm}} < –1.24). Ice absorption features are observed in ∼11% (56%) of GOALS LIRGs (ULIRGs) in sources with a range of silicate depths. Most GOALS LIRGs have L(H{sub 2})/L(PAH) ratios elevated above those observed for normal star-forming galaxies and exhibit a trend for increasing L(H{sub 2})/L

  16. Properties of Dust Obscured Galaxies in the Nep-Deep Field

    NASA Astrophysics Data System (ADS)

    Oi, Nagisa; Matsuhara, Hideo; Pearson, Chris; Buat, Veronique; Burgarella, Denis; Malkan, Matt; Miyaji, Takamitsu; AKARI-NEP Team

    2017-03-01

    We selected 47 DOGs at z∼1.5 using optical R (or r^{'}), AKARI 18 μm, and 24 μm color in the AKARI North Ecliptic Pole (NEP) Deep survey field. Using the colors among 3, 4, 7, and 9μm, we classified them into 3 groups; bump DOGs (23 sources), power-law DOGs (16 sources), and unknown DOGs (8 sources). We built spectral energy distributions (SEDs) with optical to far-infrared photometric data and investigated their properties using SED fitting method. We found that AGN activity such as a AGN contribution to the infrared luminosity and a Chandra detection rate for bump and power-law DOGs are significantly different, while stellar component properties like a stellar mass and a star-formation rate are similar to each other. A specific star-formation rate range of power-law DOGs is slightly higher than that of bump DOGs with wide overlap. Herschel/PACS detection rates are almost the same between bump and power-law DOGs. On the other hand SPIRE detection rates show large differences between bump and power-law DOGs. These results might be explained by differences in dust temperatures. Both groups of DOGs host hot and/or warm dust (∼ 50 Kelvin), and many bump DOGs contain cooler dust (≤ 30 Kelvin)

  17. HERschel Observations of Edge-on Spirals (HEROES). I. Far-infrared morphology and dust mass determination

    NASA Astrophysics Data System (ADS)

    Verstappen, J.; Fritz, J.; Baes, M.; Smith, M. W. L.; Allaert, F.; Bianchi, S.; Blommaert, J. A. D. L.; De Geyter, G.; De Looze, I.; Gentile, G.; Gordon, K. D.; Holwerda, B. W.; Viaene, S.; Xilouris, E. M.

    2013-08-01

    Context. Edge-on spiral galaxies with prominent dust lanes provide us with an excellent opportunity to study the distribution and properties of the dust within them. The HEROES project was set up to observe a sample of seven large edge-on galaxies across various wavelengths for this investigation. Aims: Within this first paper, we present the Herschel observations and perform a qualitative and quantitative analysis on them, and we derive some global properties of the far infrared and submillimetre emission. Methods: We determine horizontal and vertical profiles from the Herschel observations of the galaxies in the sample and describe the morphology. Modified black-body fits to the global fluxes, measured using aperture photometry, result in dust temperatures and dust masses. The latter values are compared to those that are derived from radiative transfer models taken from the literature. Results: On the whole, our Herschel flux measurements agree well with archival values. We find that the exponential horizontal dust distribution model often used in the literature generally provides a good description of the observed horizontal profiles. Three out of the seven galaxies show signatures of extended vertical emission at 100 and 160 μm at the 5σ level, but in two of these it is probably due to deviations from an exactly edge-on orientation. Only for NGC 4013, a galaxy in which vertically extended dust has already been detected in optical images, we can detect vertically extended dust, and the derived scaleheight agrees with the value estimated through radiative transfer modelling. Our analysis hints at a correlation between the dust scaleheight and its degree of clumpiness, which we infer from the difference between the dust masses as calculated from modelling of optical data and from fitting the spectral energy distribution of Herschel datapoints. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia

  18. Global dust attenuation in disc galaxies: strong variation with specific star formation and stellar mass, and the importance of sample selection

    NASA Astrophysics Data System (ADS)

    Devour, Brian M.; Bell, Eric F.

    2016-06-01

    We study the relative dust attenuation-inclination relation in 78 721 nearby galaxies using the axis ratio dependence of optical-near-IR colour, as measured by the Sloan Digital Sky Survey, the Two Micron All Sky Survey, and the Wide-field Infrared Survey Explorer. In order to avoid to the greatest extent possible attenuation-driven biases, we carefully select galaxies using dust attenuation-independent near- and mid-IR luminosities and colours. Relative u-band attenuation between face-on and edge-on disc galaxies along the star-forming main sequence varies from ˜0.55 mag up to ˜1.55 mag. The strength of the relative attenuation varies strongly with both specific star formation rate and galaxy luminosity (or stellar mass). The dependence of relative attenuation on luminosity is not monotonic, but rather peaks at M3.4 μm ≈ -21.5, corresponding to M* ≈ 3 × 1010 M⊙. This behaviour stands seemingly in contrast to some older studies; we show that older works failed to reliably probe to higher luminosities, and were insensitive to the decrease in attenuation with increasing luminosity for the brightest star-forming discs. Back-of-the-envelope scaling relations predict the strong variation of dust optical depth with specific star formation rate and stellar mass. More in-depth comparisons using the scaling relations to model the relative attenuation require the inclusion of star-dust geometry to reproduce the details of these variations (especially at high luminosities), highlighting the importance of these geometrical effects.

  19. A Spitzer IRS Low-Resolution Spectroscopic Search for Buried AGNs in Nearby Ultraluminous Infrared Galaxies: A Constraint on Geometry Between Energy Sources and Dust

    DTIC Science & Technology

    2007-07-01

    Spectroscopic Search for Buried AGNs in Nearby Ultraluminous Infrared Galaxies: A Constraint on Geometry Between Energy Sources and Dust 5a. CONTRACT NUMBER...ionizing UV–soft- X - ray radiation. However, compared to the classical Seyfert AGNs, ULIRGs are known to contain a sub- stantially larger amount of gas...the PAHs are destroyed by strong X - ray ra- diation from the AGN (Voit 1992; Siebenmorgen et al. 2004). If the PAHs are sufficiently shielded by

  20. GALEX-SDSS-WISE Legacy Catalog (GSWLC): Star Formation Rates, Stellar Masses, and Dust Attenuations of 700,000 Low-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Salim, Samir; Lee, Janice C.; Janowiecki, Steven; da Cunha, Elisabete; Dickinson, Mark; Boquien, Médéric; Burgarella, Denis; Salzer, John J.; Charlot, Stéphane

    2016-11-01

    In this paper, we present the GALEX-SDSS-WISE Legacy Catalog (GSWLC), a catalog of physical properties (stellar masses, dust attenuations, and star formation rates [SFRs]) for ˜700,000 galaxies with Sloan Digital Sky Survey (SDSS) redshifts below 0.3. GSWLC contains galaxies within the Galaxy Evolution Explorer footprint, regardless of a UV detection, covering 90% of SDSS. The physical properties were obtained from UV/optical spectral energy distribution (SED) fitting following Bayesian methodology of Salim et al., with improvements such as blending corrections for low-resolution UV photometry, flexible dust attenuation laws, and emission-line corrections. GSWLC also includes mid-IR SFRs derived from IR templates based on 22 μ {{m}} Wide-field Infrared Survey Explorer observations. These estimates are independent of UV/optical SED fitting, in order to separate possible systematics. The paper argues that the comparison of specific SFRs (sSFRs) is more informative and physically motivated than the comparison of SFRs. The sSFRs resulting from the UV/optical SED fitting are compared to the mid-IR sSFRs and to sSFRs from three published catalogs. For “main-sequence” galaxies with no active galactic nucleus (AGN) all sSFRs are in very good agreement (within 0.1 dex on average). In particular, the widely used aperture-corrected SFRs from the MPA/JHU catalog show no systematic offsets, in contrast to some integral field spectroscopy results. For galaxies below the main sequence (log sSFR \\lt -11), mid-IR (s)SFRs based on fixed luminosity-SFR conversion are severely biased (up to 2 dex) because the dust is primarily heated by old stars. Furthermore, mid-IR (s)SFRs are overestimated by up to 0.6 dex for galaxies with AGNs, presumably due to nonstellar dust heating. UV/optical (s)SFRs are thus preferred to IR-based (s)SFRs for quenched galaxies and those that host AGNs.

  1. High-Redshift Dust Obscured Galaxies: A Morphology-Spectral Energy Distribution Connection Revealed by Keck Adaptive Optics

    NASA Astrophysics Data System (ADS)

    Melbourne, J.; Bussman, R. S.; Brand, K.; Desai, V.; Armus, L.; Dey, Arjun; Jannuzi, B. T.; Houck, J. R.; Matthews, K.; Soifer, B. T.

    2009-06-01

    A simple optical to mid-IR color selection, R - [24]>14, i.e., f ν(24 μm)/f ν(R) gsim 1000, identifies highly dust obscured galaxies (DOGs) with typical redshifts of z ~ 2 ± 0.5. Extreme mid-IR luminosities (L IR > 1012-14) suggest that DOGs are powered by a combination of active galactic nuclei (AGNs) and star formation, possibly driven by mergers. In an effort to compare their photometric properties with their rest-frame optical morphologies, we obtained high-spatial resolution (0farcs05-0farcs1) Keck Adaptive Optics K'-band images of 15 DOGs. The images reveal a wide range of morphologies, including small exponential disks (eight of 15), small ellipticals (four of 15), and unresolved sources (two of 15). One particularly diffuse source could not be classified because of low signal-to-noise ratio. We find a statistically significant correlation between galaxy concentration and mid-IR luminosity, with the most luminous DOGs exhibiting higher concentration and smaller physical size. DOGs with high concentration also tend to have spectral energy distributions (SEDs) suggestive of AGN activity. Thus, central AGN light may be biasing the morphologies of the more luminous DOGs to higher concentration. Conversely, more diffuse DOGs tend to show an SED shape suggestive of star formation. Two of 15 in the sample show multiple resolved components with separations of ~1 kpc, circumstantial evidence for ongoing mergers. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  2. Chemical abundances in the PN Wray16-423 in the Sagittarius dwarf spheroidal galaxy: constraining the dust composition

    NASA Astrophysics Data System (ADS)

    Otsuka, Masaaki

    2015-10-01

    We performed a detailed analysis of elemental abundances, dust features, and polycyclic aromatic hydrocarbons (PAHs) in the C-rich planetary nebula (PN) Wray16-423 in the Sagittarius dwarf spheroidal galaxy, based on a unique data set taken from the Subaru/HDS, MPG/ESO FEROS, HST/WFPC2, and Spitzer/IRS. We performed the first measurements of Kr, Fe, and recombination O abundance in this PN. The extremely small [Fe/H] implies that most Fe atoms are in the solid phase, considering into account the abundance of [Ar/H]. The Spitzer/IRS spectrum displays broad 16-24 μm and 30 μm features, as well as PAH bands at 6-9 and 10-14 μm. The unidentified broad 16-24 μm feature may not be related to iron sulphide (FeS), amorphous silicate, or PAHs. Using the spectral energy distribution model, we derived the luminosity and effective temperature of the central star, and the gas and dust masses. The observed elemental abundances and derived gas mass are in good agreement with asymptotic giant branch nucleosynthesis models for an initial mass of 1.90 M⊙ and a metallicity of Z = 0.004. We infer that respectively about 80, 50, and 90 per cent of the Mg, S, and Fe atoms are in the solid phase. We also assessed the maximum possible magnesium sulphide (MgS) and iron-rich sulphide (Fe50S) masses and tested whether these species can produce the band flux of the observed 30 μm feature. Depending on what fraction of the sulphur is in sulphide molecules such as CS, we conclude that MgS and Fe50S could be possible carriers of the 30 μm feature in this PN.

  3. Probing the Peak Epoch of Cosmic Star Formation (1Galaxies Behind the Lensing Clusters: UV Luminosity Function and the Dust Attenuation

    NASA Astrophysics Data System (ADS)

    Alavi, Anahita; Siana, Brian D.; Richard, Johan; Rafelski, Marc; Jauzac, Mathilde; Limousin, Marceau; Stark, Daniel; Teplitz, Harry I.

    2016-01-01

    Obtaining a complete census of cosmic star formation requires an understanding of faint star-forming galaxies that are far below the detection limits of current surveys. To search for the faint galaxies, we use the power of strong gravitational lensing from foreground galaxy clusters to boost the detection limits of HST to much fainter luminosities. Using the WFC3/UVIS on board the HST, we obtain deep UV images of 4 lensing clusters with existing deep optical and near-infrared data (three from Frontier Fields survey). Building multiband photometric catalogs and applying a photometric redshift selection, we uncover a large population of dwarf galaxies (-18.5galaxies keeps increasing steeply toward very faint magnitudes (MUV=-12.5). As an important implication of a steep faint-end slope LF, we show that the faint galaxies (-18.550%) at these redshifts. We use this unique sample to investigate further the various properties of dwarf galaxies as it is claimed to deviate from the trends seen for the more massive galaxies. Recent hydro-dynamical simulations and observations of local dwarfs show that these galaxies have episodic bursts of star formation on short time scales (< 10 Myr). We find that the bursty star formation histories (SFHs) cause a large intrinsic scatter in UV colors (β) at MUV > -16, comparing a sample of low mass galaxies from simulations with bursty SFHs with our comprehensive measurements of the observed β values. As this scatter can also be due to the dust extinction, we distinguish these two effects by measuring the dust attenuation using Balmer decrement (Hα/Hβ) ratios from our MOSFIRE/Keck spectroscopy.

  4. GETTING TO THE HEART OF A GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This collage of images in visible and infrared light reveals how the barred spiral galaxy NGC 1365 is feeding material into its central region, igniting massive star birth and probably causing its bulge of stars to grow. The material also is fueling a black hole in the galaxy's core. A galaxy's bulge is a central, football-shaped structure composed of stars, gas, and dust. The black-and-white image in the center, taken by a ground-based telescope, displays the entire galaxy. But the telescope's resolution is not powerful enough to reveal the flurry of activity in the galaxy's hub. The blue box in the galaxy's central region outlines the area observed by the NASA Hubble Space Telescope's visible-light camera, the Wide Field and Planetary Camera 2 (WFPC2). The red box pinpoints a narrower view taken by the Hubble telescope's infrared camera, the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). A barred spiral is characterized by a lane of stars, gas, and dust slashing across a galaxy's central region. It has a small bulge that is dominated by a disk of material. The spiral arms begin at both ends of the bar. The bar is funneling material into the hub, which triggers star formation and feeds the bulge. The visible-light picture at upper left is a close-up view of the galaxy's hub. The bright yellow orb is the nucleus. The dark material surrounding the orb is gas and dust that is being funneled into the central region by the bar. The blue regions pinpoint young star clusters. In the infrared image at lower right, the Hubble telescope penetrates the dust seen in the WFPC2 picture to reveal more clusters of young stars. The bright blue dots represent young star clusters; the brightest of the red dots are young star clusters enshrouded in dust and visible only in the infrared image. The fainter red dots are older star clusters. The WFPC2 image is a composite of three filters: near-ultraviolet (3327 Angstroms), visible (5552 Angstroms), and near-infrared (8269

  5. GETTING TO THE HEART OF A GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This collage of images in visible and infrared light reveals how the barred spiral galaxy NGC 1365 is feeding material into its central region, igniting massive star birth and probably causing its bulge of stars to grow. The material also is fueling a black hole in the galaxy's core. A galaxy's bulge is a central, football-shaped structure composed of stars, gas, and dust. The black-and-white image in the center, taken by a ground-based telescope, displays the entire galaxy. But the telescope's resolution is not powerful enough to reveal the flurry of activity in the galaxy's hub. The blue box in the galaxy's central region outlines the area observed by the NASA Hubble Space Telescope's visible-light camera, the Wide Field and Planetary Camera 2 (WFPC2). The red box pinpoints a narrower view taken by the Hubble telescope's infrared camera, the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). A barred spiral is characterized by a lane of stars, gas, and dust slashing across a galaxy's central region. It has a small bulge that is dominated by a disk of material. The spiral arms begin at both ends of the bar. The bar is funneling material into the hub, which triggers star formation and feeds the bulge. The visible-light picture at upper left is a close-up view of the galaxy's hub. The bright yellow orb is the nucleus. The dark material surrounding the orb is gas and dust that is being funneled into the central region by the bar. The blue regions pinpoint young star clusters. In the infrared image at lower right, the Hubble telescope penetrates the dust seen in the WFPC2 picture to reveal more clusters of young stars. The bright blue dots represent young star clusters; the brightest of the red dots are young star clusters enshrouded in dust and visible only in the infrared image. The fainter red dots are older star clusters. The WFPC2 image is a composite of three filters: near-ultraviolet (3327 Angstroms), visible (5552 Angstroms), and near-infrared (8269

  6. Dirbe evidence for a wrap in the interstellar dust layer and stellar disk of the galaxy

    NASA Technical Reports Server (NTRS)

    Freudenreich, H. T.; Berriman, G. B.; Dwek, E.; Hauser, M. G.; Kelsall, T.; Moseley, S. H.; Silverberg, R. F.; Sodroski, T. J.; Toller, G. N.; Weiland, J. L.

    1994-01-01

    The Diffuse Infrared Background Experiment (DIRBE) of the Cosmic Background Explorer (COBE) has mapped the surface brightness distributions of the Galactic plane at wavelengths from 1.25 to 240 micrometers. In these maps the latitude of peak brightness, as a function of longitude, traces a roughly sinusoidal curve of period approximately 360 deg. In the far-infrared, where emission by interstellar dust dominates the surface brightness, this curve agrees well with that derived from maps of the velocity-integrated H 1, suggesting that the layers of dust and neutral atomic hydrogen are similarly displaced from the Galactic plane. In the near-infrared (lambda less than 5 micrometers), where old disk stars dominate the emission, the brightness crest exhibits the same phase but roughly half the amplitude. The reduced amplitude of the warp in stellar light could result from a lesser warping of the stellar disk, or from a more rapid falloff of the density of stars relative to the density of gas, possibly due to a radial truncation of the disk.

  7. Dirbe evidence for a wrap in the interstellar dust layer and stellar disk of the galaxy

    NASA Technical Reports Server (NTRS)

    Freudenreich, H. T.; Berriman, G. B.; Dwek, E.; Hauser, M. G.; Kelsall, T.; Moseley, S. H.; Silverberg, R. F.; Sodroski, T. J.; Toller, G. N.; Weiland, J. L.

    1994-01-01

    The Diffuse Infrared Background Experiment (DIRBE) of the Cosmic Background Explorer (COBE) has mapped the surface brightness distributions of the Galactic plane at wavelengths from 1.25 to 240 micrometers. In these maps the latitude of peak brightness, as a function of longitude, traces a roughly sinusoidal curve of period approximately 360 deg. In the far-infrared, where emission by interstellar dust dominates the surface brightness, this curve agrees well with that derived from maps of the velocity-integrated H 1, suggesting that the layers of dust and neutral atomic hydrogen are similarly displaced from the Galactic plane. In the near-infrared (lambda less than 5 micrometers), where old disk stars dominate the emission, the brightness crest exhibits the same phase but roughly half the amplitude. The reduced amplitude of the warp in stellar light could result from a lesser warping of the stellar disk, or from a more rapid falloff of the density of stars relative to the density of gas, possibly due to a radial truncation of the disk.

  8. Ultra-faint ultraviolet galaxies at z ∼ 2 behind the lensing cluster A1689: The luminosity function, dust extinction, and star formation rate density

    SciTech Connect

    Alavi, Anahita; Siana, Brian; Freeman, William R.; Dominguez, Alberto; Richard, Johan; Stark, Daniel P.; Robertson, Brant; Scarlata, Claudia; Teplitz, Harry I.; Rafelski, Marc; Kewley, Lisa

    2014-01-10

    We have obtained deep ultraviolet imaging of the lensing cluster A1689 with the WFC3/UVIS camera onboard the Hubble Space Telescope in the F275W (30 orbits) and F336W (4 orbits) filters. These images are used to identify z ∼ 2 star-forming galaxies via their Lyman break, in the same manner that galaxies are typically selected at z ≥ 3. Because of the unprecedented depth of the images and the large magnification provided by the lensing cluster, we detect galaxies 100× fainter than previous surveys at this redshift. After removing all multiple images, we have 58 galaxies in our sample in the range –19.5 < M {sub 1500} < –13 AB mag. Because the mass distribution of A1689 is well constrained, we are able to calculate the intrinsic sensitivity of the observations as a function of source plane position, allowing for accurate determinations of effective volume as a function of luminosity. We fit the faint-end slope of the luminosity function to be α = –1.74 ± 0.08, which is consistent with the values obtained for 2.5 < z < 6. Notably, there is no turnover in the luminosity function down to M {sub 1500} = –13 AB mag. We fit the UV spectral slopes with photometry from existing Hubble optical imaging. The observed trend of increasingly redder slopes with luminosity at higher redshifts is observed in our sample, but with redder slopes at all luminosities and average reddening of (E(B – V)) = 0.15 mag. We assume the stars in these galaxies are metal poor (0.2 Z {sub ☉}) compared to their brighter counterparts (Z {sub ☉}), resulting in bluer assumed intrinsic UV slopes and larger derived values for dust extinction. The total UV luminosity density at z ∼ 2 is 4.31{sub −0.60}{sup +0.68}×10{sup 26} erg s{sup –1} Hz{sup –1} Mpc{sup –3}, more than 70% of which is emitted by galaxies in the luminosity range of our sample. Finally, we determine the global star formation rate density from UV-selected galaxies at z ∼ 2 (assuming a constant dust

  9. Stellar Absorption Line Analysis of Local Star-forming Galaxies: The Relation between Stellar Mass, Metallicity, Dust Attenuation, and Star Formation Rate

    NASA Astrophysics Data System (ADS)

    Zahid, H. Jabran; Kudritzki, Rolf-Peter; Conroy, Charlie; Andrews, Brett; Ho, I.-Ting

    2017-09-01

    We analyze the optical continuum of star-forming galaxies in the Sloan Digital Sky Survey by fitting stacked spectra with stellar population synthesis models to investigate the relation between stellar mass, stellar metallicity, dust attenuation, and star formation rate. We fit models calculated with star formation and chemical evolution histories that are derived empirically from multi-epoch observations of the stellar mass–star formation rate and the stellar mass–gas-phase metallicity relations, respectively. We also fit linear combinations of single-burst models with a range of metallicities and ages. Star formation and chemical evolution histories are unconstrained for these models. The stellar mass–stellar metallicity relations obtained from the two methods agree with the relation measured from individual supergiant stars in nearby galaxies. These relations are also consistent with the relation obtained from emission-line analysis of gas-phase metallicity after accounting for systematic offsets in the gas-phase metallicity. We measure dust attenuation of the stellar continuum and show that its dependence on stellar mass and star formation rate is consistent with previously reported results derived from nebular emission lines. However, stellar continuum attenuation is smaller than nebular emission line attenuation. The continuum-to-nebular attenuation ratio depends on stellar mass and is smaller in more massive galaxies. Our consistent analysis of stellar continuum and nebular emission lines paves the way for a comprehensive investigation of stellar metallicities of star-forming and quiescent galaxies.

  10. Hyper-luminous dust-obscured galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE

    NASA Astrophysics Data System (ADS)

    Toba, Yoshiki; Nagao, Tohru; Strauss, Michael A.; Aoki, Kentaro; Goto, Tomotsugu; Imanishi, Masatoshi; Kawaguchi, Toshihiro; Terashima, Yuichi; Ueda, Yoshihiro; Bosch, James; Bundy, Kevin; Doi, Yoshiyuki; Inami, Hanae; Komiyama, Yutaka; Lupton, Robert H.; Matsuhara, Hideo; Matsuoka, Yoshiki; Miyazaki, Satoshi; Morokuma, Tomoki; Nakata, Fumiaki; Oi, Nagisa; Onoue, Masafusa; Oyabu, Shinki; Price, Paul; Tait, Philip J.; Takata, Tadafumi; Tanaka, Manobu M.; Terai, Tsuyoshi; Turner, Edwin L.; Uchida, Tomohisa; Usuda, Tomonori; Utsumi, Yousuke; Yamada, Yoshihiko; Wang, Shiang-Yu

    2015-10-01

    We present the photometric properties of a sample of infrared (IR) bright dust-obscured galaxies (DOGs). Combining wide and deep optical images obtained with the Hyper Suprime-Cam on the Subaru Telescope and all-sky mid-IR (MIR) images taken with Wide-Field Infrared Survey Explorer, we discovered 48 DOGs with i - Ks > 1.2 and i - [22] > 7.0, where i, Ks, and [22] represent AB magnitude in the i-band, Ks-band, and 22 μm, respectively, in the GAMA 14 hr field (˜ 9 deg2). Among these objects, 31 (˜ 65%) show power-law spectral energy distributions (SEDs) in the near-IR (NIR) and MIR regime, while the remainder show an NIR bump in their SEDs. Assuming that the redshift distribution for our DOGs sample is Gaussian, with mean and sigma z = 1.99 ± 0.45, we calculated their total IR luminosity using an empirical relation between 22 μm luminosity and total IR luminosity. The average value of the total IR luminosity is (3.5 ± 1.1) × 1013 L⊙, which classifies them as hyper-luminous infrared galaxies. We also derived the total IR luminosity function (LF) and IR luminosity density (LD) for a flux-limited subsample of 18 DOGs with 22 μm flux greater than 3.0 mJy and with i-band magnitude brighter than 24 AB magnitude. The derived space density for this subsample is log φ = -6.59 ± 0.11 [Mpc-3]. The IR LF for DOGs including data obtained from the literature is fitted well by a double-power law. The derived lower limit for the IR LD for our sample is ρIR ˜ 3.8 × 107 [L⊙ Mpc-3] and its contributions to the total IR LD, IR LD of all ultra-luminous infrared galaxies, and that of all DOGs are > 3%, > 9%, and > 15%, respectively.

  11. Star formation histories, extinction, and dust properties of strongly lensed z ~ 1.5-3 star-forming galaxies from the Herschel Lensing Survey

    NASA Astrophysics Data System (ADS)

    Sklias, P.; Zamojski, M.; Schaerer, D.; Dessauges-Zavadsky, M.; Egami, E.; Rex, M.; Rawle, T.; Richard, J.; Boone, F.; Simpson, J. M.; Smail, I.; van der Werf, P.; Altieri, B.; Kneib, J. P.

    2014-01-01

    Context. Multi-wavelength, optical to IR/submm observations of strongly lensed galaxies identified by the Herschel Lensing Survey are used to determine the physical properties of high-redshift star-forming galaxies close to or below the detection limits of blank fields. Aims: We aim to constrain theIR stellar and dust content, and to determine star formation rates and histories, dust attenuation and extinction laws, and other related properties. Methods: We studied a sample of seven galaxies with spectroscopic redshifts z ~ 1.5-3 that have been detected with precision thanks to gravitational lensing, and whose spectral energy distribution (SED) has been determined from the rest-frame UV to the IR/mm domain. For comparison, our sample includes two previously well-studied lensed galaxies, MS1512-cB58 and the Cosmic Eye, for which we also provide updated Herschel measurements. We performed SED fits of the full photometry of each object, and of the optical and infrared parts separately, exploring various star formation histories, using different extinction laws, and exploring the effects of nebular emission. The IR luminosity, in particular, is predicted consistently from the stellar population model. The IR observations and emission line measurements, where available, are used as a posteriori constraints on the models. We also explored energy conserving models, that we created by using the observed IR/UV ratio to estimate the extinction. Results: Among the models we have tested, models with exponentially declining star-forming histories including nebular emission and assuming the Calzetti attenuation law best fit most of the observables. Models assuming constant or rising star formation histories predict in most cases too much IR luminosity. The SMC extinction law underpredicts the IR luminosity in most cases, except for two out of seven galaxies, where we cannot distinguish between different extinction laws. Our sample has a median lensing-corrected IR luminosity ~3

  12. a Snapshot Survey of X-Ray Selected Central Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Edge, Alastair

    1999-07-01

    Central cluster galaxies are the most massive stellar systems known and have been used as standard candles for many decades. Only recently have central cluster galaxies been recognised to exhibit a wide variety of small scale {<100 pc} features that can only be reliably detected with HST resolution. The most intriguing of these are dust lanes which have been detected in many central cluster galaxies. Dust is not expected to survive long in the hostile cluster environment unless shielded by the ISM of a disk galaxy or very dense clouds of cold gas. WFPC2 snapshot images of a representative subset of the central cluster galaxies from an X-ray selected cluster sample would provide important constraints on the formation and evolution of dust in cluster cores that cannot be obtained from ground-based observations. In addition, these images will allow the AGN component, the frequency of multiple nuclei, and the amount of massive-star formation in central cluster galaxies to be ass es sed. The proposed HST observatio ns would also provide high-resolution images of previously unresolved gravitational arcs in the most massive clusters in our sample resulting in constraints on the shape of the gravitational potential of these systems. This project will complement our extensive multi-frequency work on this sample that includes optical spectroscopy and photometry, VLA and X-ray images for the majority of the 210 targets.

  13. ISM Masses and the Star formation Law at Z = 1 to 6: ALMA Observations of Dust Continuum in 145 Galaxies in the COSMOS Survey Field

    NASA Astrophysics Data System (ADS)

    Scoville, N.; Sheth, K.; Aussel, H.; Vanden Bout, P.; Capak, P.; Bongiorno, A.; Casey, C. M.; Murchikova, L.; Koda, J.; Álvarez-Márquez, J.; Lee, N.; Laigle, C.; McCracken, H. J.; Ilbert, O.; Pope, A.; Sanders, D.; Chu, J.; Toft, S.; Ivison, R. J.; Manohar, S.

    2016-04-01

    ALMA Cycle 2 observations of long-wavelength dust emission in 145 star-forming galaxies are used to probe the evolution of the star-forming interstellar medium (ISM). We also develop a physical basis and empirical calibration (with 72 low-z and z ˜ 2 galaxies) for using the dust continuum as a quantitative probe of ISM masses. The galaxies with the highest star formation rates (SFRs) at < z> = 2.2 and 4.4 have gas masses up to 100 times that of the Milky Way and gas mass fractions reaching 50%-80%, i.e., gas masses 1-4× their stellar masses. We find a single high-z star formation law: {SFR}=35 {M}{mol}0.89× {(1+z)}z=20.95× {({sSFR})}{MS}0.23 {M}⊙ yr-1—an approximately linear dependence on the ISM mass and an increased star formation efficiency per unit gas mass at higher redshift. Galaxies above the main sequence (MS) have larger gas masses but are converting their ISM into stars on a timescale only slightly shorter than those on the MS; thus, these “starbursts” are largely the result of having greatly increased gas masses rather than an increased efficiency of converting gas to stars. At z > 1, the entire population of star-forming galaxies has ˜2-5 times shorter gas depletion times than low-z galaxies. These shorter depletion times indicate a different mode of star formation in the early universe—most likely dynamically driven by compressive, high-dispersion gas motions—a natural consequence of the high gas accretion rates.

  14. Stellar populations in the edge-on spiral galaxy NGC 4565. I - Surface brightness and color distributions

    NASA Technical Reports Server (NTRS)

    Jensen, E. B.; Thuan, T. X.

    1982-01-01

    Results are presented for photographic and photoelectric photometry of the edge-on Sb galaxy NGC 4565. Major-axis, minor-axis, and perpendicular surface brightness profiles are determined, along with color gradients parallel and perpendicular to the plane of the galaxy. It is found that the galaxy's light can be deconvolved naturally into five components: (1) a starlike nucleus located at the center of the bulge and the edge of the dust lane; (2) a thin disk containing the gas and dust, the young OB stars, and the spiral arms; (3) a thick disk that may be a locally isothermal sheet of old Population I metal-rich stars; (4) a bulge that merges smoothly into the thick disk at a radial distance of about 2.9 kpc; and (5) a corona whose light dominates the perpendicular profiles from about 2.9 to at least 8.2 kpc above the galactic plane.

  15. Unveiling the Composite Nature of Dust-Obscured Galaxies (DOGs) with Herschel

    NASA Astrophysics Data System (ADS)

    Riguccini, Laurie A.; Le Floc'h, Emeric; Mullaney, James

    2015-08-01

    DOGs are bright 24um-selected sources with extreme obscuration at optical wavelengths. Some of them are characterized by a rising power-law continuum of hot dust (T_D ~ 200-1000 K) in the near-IR emission indicating that their mid-IR luminosity is dominated by an AGN. Whereas DOGs with a fainter 24um flux display a stellar bump and their mid-IR luminosity is believed to be mainly powered by dusty star-formation. Another explanation is that the mid-IR emission still comes from AGN activity but the torus emission is so obscured that it becomes negligible with respect to the emission from the host component.In an effort to characterize the nature of the physical processes underlying their IR emission, we focus on DOGs (F24/FR>982) within the COSMOS field with Herschel data and derive their far-IR properties (e.g., total IR luminosities; mid-to-far IR colors; dust temperatures and masses and AGN contribution) based on SED fitting.Of particular interest are the 24um-bright DOGs (F24>1mJy). They present bluer far-IR/mid-IR colors than the rest of the sample, unveiling the potential presence of an AGN. The AGN contribution to the total 8-1000um flux increases as a function of the rest-frame 8um-luminosity irrespective of the redshift, with a stronger contribution at lower redshift. This confirms that faint DOGs (F24<1mJy) are dominated by star-formation while brighter DOGs show a larger contribution from an AGN.Is this FIR-selection technique allowing us to probe a new population of obscured AGN? Or does it corresponds to already known AGN in the X-rays, NIR or radio? The wealth of multi wavelength data in COSMOS will allow us to describe our results here.

  16. Watching a Cannibal Galaxy Dine

    NASA Astrophysics Data System (ADS)

    2009-11-01

    A new technique using near-infrared images, obtained with ESO's 3.58-metre New Technology Telescope (NTT), allows astronomers to see through the opaque dust lanes of the giant cannibal galaxy Centaurus A, unveiling its "last meal" in unprecedented detail - a smaller spiral galaxy, currently twisted and warped. This amazing image also shows thousands of star clusters, strewn like glittering gems, churning inside Centaurus A. Centaurus A (NGC 5128) is the nearest giant, elliptical galaxy, at a distance of about 11 million light-years. One of the most studied objects in the southern sky, by 1847 the unique appearance of this galaxy had already caught the attention of the famous British astronomer John Herschel, who catalogued the southern skies and made a comprehensive list of nebulae. Herschel could not know, however, that this beautiful and spectacular appearance is due to an opaque dust lane that covers the central part of the galaxy. This dust is thought to be the remains of a cosmic merger between a giant elliptical galaxy and a smaller spiral galaxy full of dust. Between 200 and 700 million years ago, this galaxy is indeed believed to have consumed a smaller spiral, gas-rich galaxy - the contents of which appear to be churning inside Centaurus A's core, likely triggering new generations of stars. First glimpses of the "leftovers" of this meal were obtained thanks to observations with the ESA Infrared Space Observatory , which revealed a 16 500 light-year-wide structure, very similar to that of a small barred galaxy. More recently, NASA's Spitzer Space Telescope resolved this structure into a parallelogram, which can be explained as the remnant of a gas-rich spiral galaxy falling into an elliptical galaxy and becoming twisted and warped in the process. Galaxy merging is the most common mechanism to explain the formation of such giant elliptical galaxies. The new SOFI images, obtained with the 3.58-metre New Technology Telescope at ESO's La Silla Observatory

  17. The H I-Rich Elliptical Galaxy NGC 5266

    NASA Astrophysics Data System (ADS)

    Morganti, R.; Sadler, E. M.; Oosterloo, T.; Pizzella, A.; Bertola, F.

    1997-03-01

    We present new ion{H}{1} images of the dust-lane elliptical galaxy NGC 5266 already known from single-dish observations to contain a large amount of ion{H}{1}. Our new data confirm that NGC 5266 contains ~2.4 x 10(10) msun (for Hdeg = 50 kmsMp) of neutral hydrogen, i.e. more than most spiral galaxies of similar luminosity. The gas extends to ~8(') each side of the nucleus, or 8 times the optical half-light radius R_e. Surprisingly, most of the ion{H}{1} extends almost orthogonal to the optical dust lane. A small fraction of the ion{H}{1} is associated with the dust lane and there are some hints of a faint warp connecting the two structures. The ion{H}{1} distribution is somewhat clumpy and asymmetric, but the overall velocity field in the inner 4(') can be successfully modeled by assuming that the gas lies mainly in two perpendicular planes - in the plane of the dust lane in the central parts and orthogonal to this in the outer regions. Beyond the 4(') radius, the gas has a different structure and may be in two tidal tails, or an edge-on ring. Measurement of the ion{H}{1} rotation curve is affected by asymmetries in the gas distribution, but the rotation velocity is at least 250 kms at a radius of 4(') , and a flat rotation curve of ~270 kms is consistent with the data. This would imply a value of M / L_B ~8 at ~4 R_e. If the outermost ion{H}{1} is in an edge-on ring, we estimate M / L_B ~16 at ~8 R_e. Comparing this with the value derived from optical observations for the inner region we find an increase of M / L_B by a factor ~2.7 at r ~4 R_e, and by 5.3 at r ~8 R_e. The large amount of neutral gas observed in NGC 5266 (M_HI/L_B ~0.2) and the ion{H}{1} morphology, suggest that this object may have formed from the merger of two spiral galaxies. If so, NGC 5266 probably represents a relatively old merger remnant since most of the ion{H}{1} gas appears settled.

  18. Interstellar Dust: Contributed Papers

    NASA Technical Reports Server (NTRS)

    Tielens, Alexander G. G. M. (Editor); Allamandola, Louis J. (Editor)

    1989-01-01

    A coherent picture of the dust composition and its physical characteristics in the various phases of the interstellar medium was the central theme. Topics addressed included: dust in diffuse interstellar medium; overidentified infrared emission features; dust in dense clouds; dust in galaxies; optical properties of dust grains; interstellar dust models; interstellar dust and the solar system; dust formation and destruction; UV, visible, and IR observations of interstellar extinction; and quantum-statistical calculations of IR emission from highly vibrationally excited polycyclic aromatic hydrocarbon (PAH) molecules.

  19. Evolution of the dust emission of massive galaxies up to z = 4 and constraints on their dominant mode of star formation

    NASA Astrophysics Data System (ADS)

    Béthermin, Matthieu; Daddi, Emanuele; Magdis, Georgios; Lagos, Claudia; Sargent, Mark; Albrecht, Marcus; Aussel, Hervé; Bertoldi, Frank; Buat, Véronique; Galametz, Maud; Heinis, Sébastien; Ilbert, Olivier; Karim, Alexander; Koekemoer, Anton; Lacey, Cedric; Le Floc'h, Emeric; Navarrete, Felipe; Pannella, Maurilio; Schreiber, Corentin; Smolčić, Vernesa; Symeonidis, Myrto; Viero, Marco

    2015-01-01

    We aim to measure the average dust and molecular gas content of massive star-forming galaxies (>3 × 1010M⊙) up to z = 4 in the COSMOS field to determine if the intense star formation observed at high redshift is induced by major mergers or is caused by large gas reservoirs. Firstly, we measured the evolution of the average spectral energy distributions as a function of redshift using a stacking analysis of Spitzer, Herschel, LABOCA, and AzTEC data for two samples of galaxies: normal star-forming objects and strong starbursts, as defined by their distance to the main sequence. We found that the mean intensity of the radiation field ⟨ U ⟩ heating the dust (strongly correlated with dust temperature) increases with increasing redshift up to z = 4 in main-sequence galaxies. We can reproduce this evolution with simple models that account for the decrease in the gas metallicity with redshift. No evolution of ⟨ U ⟩ with redshift is found in strong starbursts. We then deduced the evolution of the molecular gas fraction (defined here as Mmol/ (Mmol + M⋆)) with redshift and found a similar, steeply increasing trend for both samples. At z ~ 4, this fraction reaches ~60%. The average position of the main-sequence galaxies is on the locus of the local, normal star-forming disks in the integrated Schmidt-Kennicutt diagram (star formation rate versus mass of molecular gas), suggesting that the bulk of the star formation up to z = 4 is dominated by secular processes. Appendices are available in electronic form at http://www.aanda.org

  20. The Black Hole Masses and Star Formation Rates of z>1 Dust Obscured Galaxies: Results from Keck OSIRIS Integral Field Spectroscopy

    NASA Astrophysics Data System (ADS)

    Melbourne, J.; Peng, Chien Y.; Soifer, B. T.; Urrutia, Tanya; Desai, Vandana; Armus, L.; Bussmann, R. S.; Dey, Arjun; Matthews, K.

    2011-04-01

    We have obtained high spatial resolution Keck OSIRIS integral field spectroscopy of four z ~ 1.5 ultra-luminous infrared galaxies that exhibit broad Hα emission lines indicative of strong active galactic nucleus (AGN) activity. The observations were made with the Keck laser guide star adaptive optics system giving a spatial resolution of 0farcs1 or <1 kpc at these redshifts. These high spatial resolution observations help to spatially separate the extended narrow-line regions—possibly powered by star formation—from the nuclear regions, which may be powered by both star formation and AGN activity. There is no evidence for extended, rotating gas disks in these four galaxies. Assuming dust correction factors as high as A(Hα) = 4.8 mag, the observations suggest lower limits on the black hole masses of (1-9) × 108 M sun and star formation rates <100 M sun yr-1. The black hole masses and star formation rates of the sample galaxies appear low in comparison to other high-z galaxies with similar host luminosities. We explore possible explanations for these observations, including host galaxy fading, black hole growth, and the shut down of star formation.

  1. Dust-depletion sequences in damped Lyman-α absorbers. A unified picture from low-metallicity systems to the Galaxy

    NASA Astrophysics Data System (ADS)

    De Cia, A.; Ledoux, C.; Mattsson, L.; Petitjean, P.; Srianand, R.; Gavignaud, I.; Jenkins, E. B.

    2016-12-01

    We study metal depletion due to dust in the interstellar medium (ISM) to infer the properties of dust grains and characterize the metal and dust content of galaxies down to low metallicity and intermediate redshift z. We provide metal column densities and abundances of a sample of 70 damped Lyman-α absorbers (DLAs) towards quasars, observed at high spectral resolution with the Very Large Telescope (VLT) Ultraviolet and Visual Echelle Spectrograph (UVES). This is the largest sample of phosphorus abundances measured in DLAs so far. We use literature measurements for Galactic clouds to cover the high-metallicity end. We discover tight (scatter ≲ 0.2 dex) correlations between [Zn/Fe] and the observed relative abundances from dust depletion. This implies that grain growth in the ISM is an important process of dust production. These sequences are continuous in [Zn/Fe] from dust-free to dusty DLAs, and to Galactic clouds, suggesting that the availability of refractory metals in the ISM is crucial for dust production, regardless of the star formation history. We observe [S/Zn] up to 0.25 dex in DLAs, which is broadly consistent with Galactic stellar abundances. Furthermore, we find a good agreement between the nucleosynthetic pattern of Galactic halo stars and our observations of the least dusty DLAs. This supports recent star formation in low-metallicity DLAs. The derived depletions of Zn, O, P, S, Si, Mg, Mn, Cr, and Fe correlate with [Zn/Fe], with steeper slopes for more refractory elements. P is mostly not affected by dust depletion. We present canonical depletion patterns to be used as reference in future studies of relative abundances and depletion. We derive the total (dust-corrected) metallicity, typically -2 ≲ [M/H] tot ≲ 0 for DLAs, and scattered around solar metallicity for the Galactic ISM. The dust-to-metal ratio (mathcal{{DTM}}) increases with metallicity, again supporting the importance of grain growth for dust production. The dust extinction AV

  2. NuSTAR Observations of WISE J1036+0449, a Galaxy at z~1 Obscured by Hot Dust

    NASA Astrophysics Data System (ADS)

    Ricci, C.; Assef, R. J.; Stern, D.; Nikutta, R.; Alexander, D. M.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Blain, A. W.; Boggs, S.; Boorman, P. G.; Brandt, W. N.; Brightman, M.; Chang, C. S.; Chen, C.-T. J.; Christensen, F. E.; Comastri, A.; Craig, W. W.; Díaz-Santos, T.; Eisenhardt, P. R.; Farrah, D.; Gandhi, P.; Hailey, C. J.; Harrison, F. A.; Jun, H. D.; Koss, M. J.; LaMassa, S.; Lansbury, G. B.; Markwardt, C. B.; Stalevski, M.; Stanley, F.; Treister, E.; Tsai, C.-W.; Walton, D. J.; Wu, J. W.; Zappacosta, L.; Zhang, W. W.

    2017-01-01

    Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorer’s all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. Most known hot DOGs are located at z> 1.5, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 hot DOG candidates at z˜ 1, where they are significantly brighter and easier to study. We validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot DOGs for one of these objects, WISE J1036+0449 ({L}{Bol}≃ 8× {10}46 {erg} {{{s}}}-1). We find evidence of a broadened component in Mg ii, which would imply a black hole mass of {M}{BH}≃ 2× {10}8 {M}⊙ and an Eddington ratio of {λ }{Edd}≃ 2.7. WISE J1036+0449 is the first hot DOG detected by the Nuclear Spectroscopic Telescope Array, and observations show that the source is heavily obscured, with a column density of {N}{{H}}≃ (2{--}15)× {10}23 {{cm}}-2. The source has an intrinsic 2-10 keV luminosity of ˜ 6× {10}44 {erg} {{{s}}}-1, a value significantly lower than that expected from the mid-infrared/X-ray correlation. We also find that other hot DOGs observed by X-ray facilities show a similar deficiency of X-ray flux. We discuss the origin of the X-ray weakness and the absorption properties of hot DOGs. Hot DOGs at z≲ 1 could be excellent laboratories to probe the characteristics of the accretion flow and of the X-ray emitting plasma at extreme values of the Eddington ratio.

  3. NuSTAR Observations of WISE J1036+0449, A Galaxy at zeta approx 1 Obscured by Hot Dust

    NASA Technical Reports Server (NTRS)

    Ricci, C.; Assef, R. J.; Stern, Daniel K.; Nikutta, R.; Alexander, D. M.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Blain, A.W.; Zhang, William W.; hide

    2017-01-01

    Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorer's all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. Most known hot DOGs are located at z > 1.5, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 hot DOG candidates at z approx. 1, where they are significantly brighter and easier to study. We validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot DOGs for one of these objects, WISE J1036+0449 (L(sub BOL) approx. = 8 x 10(exp 46) erg/s). We find evidence of a broadened component in Mg II, which would imply a black hole mass of M(BH) approx. = 2 x 10(exp 8) Stellar Mass and an Eddington ratio of lambda(sub Edd) approx. = 2.7. WISE J1036+0449 is the first hot DOG detected by the Nuclear Spectroscopic Telescope Array, and observations show that the source is heavily obscured, with a column density of N(sub H) approx. = (2-15) x 10(exp 23)/sq cm. The source has an intrinsic 2-10 keV luminosity of approx. 6 x 10(exp 44) erg/s, a value significantly lower than that expected from the mid-infrared X-ray correlation. We also find that other hot DOGs observed by X-ray facilities show a similar deficiency of X-ray flux. We discuss the origin of the X-ray weakness and the absorption properties of hot DOGs. Hot DOGs at z < or approx. 1 could be excellent laboratories to probe the characteristics of the accretion flow and of the X-ray emitting plasma at extreme values of the Eddington ratio.

  4. NuSTAR Observations of WISE J1036+0449, A Galaxy at Z Approx. 1 Obscured by Hot Dust

    NASA Technical Reports Server (NTRS)

    Ricci, C.; Assef, R. J.; Stern, D.; Nikutta, R.; Alexander, D. M.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Blain, A. W.; Boggs, S.; hide

    2017-01-01

    Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorer's all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. Most known hot DOGs are located at z > 1.5, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 hot DOG candidates at z approx. 1, where they are significantly brighter and easier to study. We validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot DOGs for one of these objects, WISE J1036+0449 (L(BOL) approx. = 8 x 10(exp 46) erg/s). We find evidence of a broadened component in Mg II, which would imply a black hole mass of M(BH) approx. = 2 x 10(exp 8) Stellar Mass and an Eddington ratio of lambda(Edd) approx. = 2.7. WISE J1036+0449 is the first hot DOG detected by the Nuclear Spectroscopic Telescope Array, and observations show that the source is heavily obscured, with a column density of N(H) approx. = (2-15) x 10(exp 23)/sq cm. The source has an intrinsic 2-10 keV luminosity of approx. 6 x 10(exp 44) erg/s, a value significantly lower than that expected from the mid-infrared X-ray correlation. We also find that other hot DOGs observed by X-ray facilities show a similar deficiency of X-ray flux. We discuss the origin of the X-ray weakness and the absorption properties of hot DOGs. Hot DOGs at z < or approx. 1 could be excellent laboratories to probe the characteristics of the accretion flow and of the X-ray emitting plasma at extreme values of the Eddington ratio.

  5. Star-forming dwarf galaxies in the Virgo cluster: the link between molecular gas, atomic gas, and dust

    NASA Astrophysics Data System (ADS)

    Grossi, M.; Corbelli, E.; Bizzocchi, L.; Giovanardi, C.; Bomans, D.; Coelho, B.; De Looze, I.; Gonçalves, T. S.; Hunt, L. K.; Leonardo, E.; Madden, S.; Menéndez-Delmestre, K.; Pappalardo, C.; Riguccini, L.

    2016-05-01

    We present 12CO(1-0) and 12CO(2-1) observations of a sample of 20 star-forming dwarfs selected from the Herschel Virgo Cluster Survey, with oxygen abundances ranging from 12 + log (O / H) ~ 8.1 to 8.8. CO emission is observed in ten galaxies and marginally detected in another one. CO fluxes correlate with the FIR 250 μm emission, and the dwarfs follow the same linear relation that holds for more massive spiral galaxies extended to a wider dynamical range. We compare different methods to estimate H2 molecular masses, namely a metallicity-dependent CO-to-H2 conversion factor and one dependent on H-band luminosity. The molecular-to-stellar mass ratio remains nearly constant at stellar masses ≲ 109 M⊙, contrary to the atomic hydrogen fraction, MHI/M∗, which increases inversely with M∗. The flattening of the MH2/M∗ ratio at low stellar masses does not seem to be related to the effects of the cluster environment because it occurs for both Hi-deficient and Hi-normal dwarfs. The molecular-to-atomic ratio is more tightly correlated with stellar surface density than metallicity, confirming that the interstellar gas pressure plays a key role in determining the balance between the two gaseous components of the interstellar medium. Virgo dwarfs follow the same linear trend between molecular gas mass and star formation rate as more massive spirals, but gas depletion timescales, τdep, are not constant and range between 100 Myr and 6 Gyr. The interaction with the Virgo cluster environment is removing the atomic gas and dust components of the dwarfs, but the molecular gas appears to be less affected at the current stage of evolution within the cluster. However, the correlation between Hi deficiency and the molecular gas depletion time suggests that the lack of gas replenishment from the outer regions of the disc is lowering the star formation activity. Based on observations carried out with the IRAM 30-m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany

  6. Recognition of fast lane changing behavior

    NASA Astrophysics Data System (ADS)

    Guo, Yingshi; Wang, Chang

    2014-10-01

    Aiming at the lane change behavior recognition requirements of lane change warning system, natural lane change samples were captured by using a test vehicle. Steering angle and distance between vehicle and lane mark were used as characteristic parameters of lane change behavior. Support vector machine (SVM) method was used to establish recognizing model of lane change. The sample data were filtered by Kaiman filter. Variance-Bayesian filter model was used to fast lane change behavior identification. Final recognition results show that the recognition rate for the real lane change samples can reach 92.5273% and the proposed model can also meet the real time and reliability requirements of lane change warning system.

  7. Clustering of Infrared-bright Dust-obscured Galaxies Revealed by the Hyper Suprime-Cam and WISE

    NASA Astrophysics Data System (ADS)

    Toba, Yoshiki; Nagao, Tohru; Kajisawa, Masaru; Oogi, Taira; Akiyama, Masayuki; Ikeda, Hiroyuki; Coupon, Jean; Strauss, Michael A.; Wang, Wei-Hao; Tanaka, Masayuki; Niida, Mana; Imanishi, Masatoshi; Lee, Chien-Hsiu; Matsuhara, Hideo; Matsuoka, Yoshiki; Onoue, Masafusa; Terashima, Yuichi; Ueda, Yoshihiro; Harikane, Yuichi; Komiyama, Yutaka; Miyazaki, Satoshi; Noboriguchi, Akatoki; Usuda, Tomonori

    2017-01-01

    We present measurements of the clustering properties of a sample of infrared (IR) bright dust-obscured galaxies (DOGs). Combining 125 deg2 of wide and deep optical images obtained with the Hyper Suprime-Cam on the Subaru Telescope and all-sky mid-IR images taken with Wide-Field Infrared Survey Explorer, we have discovered 4367 IR-bright DOGs with {(i-[22])}{AB}> 7.0 and flux density at 22 μ {{m}}> 1.0 mJy. We calculate the angular autocorrelation function (ACF) for a uniform subsample of 1411 DOGs with 3.0 mJy < flux (22 μ {{m}}) < 5.0 mJy and {i}{AB} < 24.0. The ACF of our DOG subsample is well-fit with a single power law, ω (θ ) = (0.010 ± 0.003) {θ }-0.9, where θ is in degrees. The correlation amplitude of IR-bright DOGs is larger than that of IR-faint DOGs, which reflects a flux dependence of the DOG clustering, as suggested by Brodwin et al. We assume that the redshift distribution for our DOG sample is Gaussian, and consider two cases: (1) the redshift distribution is the same as IR-faint DOGs with flux at 22 μ {{m}} < 1.0 mJy, mean and sigma z = 1.99 ± 0.45, and (2) z = 1.19 ± 0.30, as inferred from their photometric redshifts. The inferred correlation length of IR-bright DOGs is r0 = 12.0 ± 2.0 and 10.3 ± 1.7 {h}-1 Mpc, respectively. IR-bright DOGs reside in massive dark matter halos with a mass of {log}[< {M}{{h}}> /({h}-1 {M}⊙ )]={13.57}-0.55+0.50 and {13.65}-0.52+0.45 in the two cases, respectively.

  8. Galaxy Zoo 2: A Detailed Morphological Catalog of 295,000 Galaxies from SDSS

    NASA Astrophysics Data System (ADS)

    Willett, Kyle; Lintott, C. J.; Bamford, S. P.; Masters, K. L.; Simmons, B.; Fortson, L.; Schawinski, K.; Simpson, R.

    2013-01-01

    The Galaxy Zoo 2 (GZ2) citizen science project was designed to obtain detailed morphological classifications of roughly a quarter million bright galaxies in the SDSS North Galactic Cap. This was enabled by more than 16 million classifications of images by 80,000 volunteer citizen scientists. Galaxy Zoo 2 greatly extends the original classifications of the Galaxy Zoo project (which primarily identified spiral and elliptical galaxies) by adding quantification of details such as oblateness, bars, bulge strength and shape, spiral arm multiplicity and tightness, and the existence of rarer features such as mergers, lenses, and dust lanes. We present preliminary results on our debiasing methods, addressing both biases from individual citizen scientist classifiers and intrinsic biases as a function of redshift, size, and absolute magnitude. We compare the GZ2 data to catalogs produced by professional astronomers and by machine-learning algorithms. Citizen science results can be directly compared to these techniques by examining the galaxies that appear in both samples. The weighted vote fractions in GZ2 show good agreement with expert classifications for fine structure morphology, particularly in identifying galactic bars and prominent bulges. The bulge classification in particular is shown to be a reasonable proxy from which T-Types can be derived using GZ2 data. A notable strength of the final catalog will be its size, with more than an order of magnitude more galaxies than extant morphological catalogs. GZ2 will be a unique resource to establish the full panoply of galaxy morphologies, as well as a baseline for studying how galaxies evolve over cosmic timescales.

  9. ALMA Imaging of Gas and Dust in a Galaxy Protocluster at Redshift 5.3: [C II] Emission in "Typical" Galaxies and Dusty Starbursts ≈1 Billion Years after the Big Bang

    NASA Astrophysics Data System (ADS)

    Riechers, Dominik A.; Carilli, Christopher L.; Capak, Peter L.; Scoville, Nicholas Z.; Smolčić, Vernesa; Schinnerer, Eva; Yun, Min; Cox, Pierre; Bertoldi, Frank; Karim, Alexander; Yan, Lin

    2014-12-01

    We report interferometric imaging of [C II](2 P 3/2→2 P 1/2) and OH(2Π1/2 J = 3/2→1/2) emission toward the center of the galaxy protocluster associated with the z = 5.3 submillimeter galaxy (SMG) AzTEC-3, using the Atacama Large (sub)Millimeter Array (ALMA). We detect strong [C II], OH, and rest-frame 157.7 μm continuum emission toward the SMG. The [C II](2 P 3/2→2 P 1/2) emission is distributed over a scale of 3.9 kpc, implying a dynamical mass of 9.7 × 1010 M ⊙, and a star formation rate (SFR) surface density of ΣSFR = 530 M ⊙ yr-1 kpc-2. This suggests that AzTEC-3 forms stars at ΣSFR approaching the Eddington limit for radiation pressure supported disks. We find that the OH emission is slightly blueshifted relative to the [C II] line, which may indicate a molecular outflow associated with the peak phase of the starburst. We also detect and dynamically resolve [C II](2 P 3/2→2 P 1/2) emission over a scale of 7.5 kpc toward a triplet of Lyman-break galaxies with moderate UV-based SFRs in the protocluster at ~95 kpc projected distance from the SMG. These galaxies are not detected in the continuum, suggesting far-infrared SFRs of <18-54 M ⊙ yr-1, consistent with a UV-based estimate of 22 M ⊙ yr-1. The spectral energy distribution of these galaxies is inconsistent with nearby spiral and starburst galaxies, but resembles those of dwarf galaxies. This is consistent with expectations for young starbursts without significant older stellar populations. This suggests that these galaxies are significantly metal-enriched, but not heavily dust-obscured, "normal" star-forming galaxies at z > 5, showing that ALMA can detect the interstellar medium in "typical" galaxies in the very early universe.

  10. A Spatially Resolved Study of Cold Dust, Molecular Gas, H ii Regions, and Stars in the z = 2.12 Submillimeter Galaxy ALESS67.1

    NASA Astrophysics Data System (ADS)

    Chen, Chian-Chou; Hodge, J. A.; Smail, Ian; Swinbank, A. M.; Walter, Fabian; Simpson, J. M.; Calistro Rivera, Gabriela; Bertoldi, F.; Brandt, W. N.; Chapman, S. C.; da Cunha, Elisabete; Dannerbauer, H.; De Breuck, C.; Harrison, C. M.; Ivison, R. J.; Karim, A.; Knudsen, K. K.; Wardlow, J. L.; Weiß, A.; van der Werf, P. P.

    2017-09-01

    We present detailed studies of a z = 2.12 submillimeter galaxy, ALESS67.1, using sub-arcsecond resolution ALMA, adaptive optics-aided VLT/SINFONI, and Hubble Space Telescope (HST)/CANDELS data to investigate the kinematics and spatial distributions of dust emission (870 μm continuum), 12CO(J = 3–2), strong optical emission lines, and visible stars. Dynamical modeling of the optical emission lines suggests that ALESS67.1 is not a pure rotating disk but a merger, consistent with the apparent tidal features revealed in the HST imaging. Our sub-arcsecond resolution data set allows us to measure half-light radii for all the tracers, and we find a factor of 4–6 smaller sizes in dust continuum compared to all the other tracers, including 12CO; also, ultraviolet (UV) and Hα emission are significantly offset from the dust continuum. The spatial mismatch between the UV continuum and the cold dust and gas reservoir supports the explanation that geometrical effects are responsible for the offset of the dusty galaxy on the IRX–β diagram. Using a dynamical method we derive an {α }{CO}=1.8+/- 1.0, consistent with other submillimeter galaxies (SMGs) that also have resolved CO and dust measurements. Assuming a single {α }{CO} value we also derive resolved gas and star formation rate surface densities, and find that the core region of the galaxy (≲ 5 kpc) follows the trend of mergers on the Schmidt–Kennicutt relationship, whereas the outskirts (≳ 5 kpc) lie on the locus of normal star-forming galaxies, suggesting different star formation efficiencies within one galaxy. Our results caution against using single size or morphology for different tracers of the star formation activity and gas content of galaxies, and therefore argue the need to use spatially resolved, multi-wavelength observations to interpret the properties of SMGs, and perhaps even for z> 1 galaxies in general.

  11. The Hidden Galaxy

    NASA Image and Video Library

    2011-01-18

    Maffei 2 is the poster child for an infrared galaxy that is almost invisible to optical telescopes. But this infrared image from NASA Spitzer Space Telescope penetrates the dust to reveal the galaxy in all its glory.

  12. Star Formation in Galaxies

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Topics addressed include: star formation; galactic infrared emission; molecular clouds; OB star luminosity; dust grains; IRAS observations; galactic disks; stellar formation in Magellanic clouds; irregular galaxies; spiral galaxies; starbursts; morphology of galactic centers; and far-infrared observations.

  13. WINGS-SPE II: A catalog of stellar ages and star formation histories, stellar masses and dust extinction values for local clusters galaxies

    NASA Astrophysics Data System (ADS)

    Fritz, J.; Poggianti, B. M.; Cava, A.; Valentinuzzi, T.; Moretti, A.; Bettoni, D.; Bressan, A.; Couch, W. J.; D'Onofrio, M.; Dressler, A.; Fasano, G.; Kjærgaard, P.; Moles, M.; Omizzolo, A.; Varela, J.

    2011-02-01

    Context. The WIde-field Nearby Galaxy clusters Survey (wings) is a project whose primary goal is to study the galaxy populations in clusters in the local universe (z < 0.07) and of the influence of environment on their stellar populations. This survey has provided the astronomical community with a high quality set of photometric and spectroscopic data for 77 and 48 nearby galaxy clusters, respectively. Aims: In this paper we present the catalog containing the properties of galaxies observed by the wings SPEctroscopic (wings-spe) survey, which were derived using stellar populations synthesis modelling approach. We also check the consistency of our results with other data in the literature. Methods: Using a spectrophotometric model that reproduces the main features of observed spectra by summing the theoretical spectra of simple stellar populations of different ages, we derive the stellar masses, star formation histories, average age and dust attenuation of galaxies in our sample. Results: ~ 5300 spectra were analyzed with spectrophotometric techniques, and this allowed us to derive the star formation history, stellar masses and ages, and extinction for the wings spectroscopic sample that we present in this paper. Conclusions: The comparison with the total mass values of the same galaxies derived by other authors based on sdss data, confirms the reliability of the adopted methods and data. Based on observations taken at the Anglo Australian Telescope (3.9 m- AAT), and at the William Herschel Telescope (4.2 m- WHT).Full Table 2 is available in electronic form both at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A45, and by querying the wings database at http://web.oapd.inaf.it/wings/new/index.html

  14. GOODS-HERSCHEL: GAS-TO-DUST MASS RATIOS AND CO-TO-H{sub 2} CONVERSION FACTORS IN NORMAL AND STARBURSTING GALAXIES AT HIGH-z

    SciTech Connect

    Magdis, Georgios E.; Rigopoulou, D.; Daddi, E.; Elbaz, D.; Sargent, M.; Dannerbauer, H.; Aussel, H.; Hwang, H. S.; Pannella, M.; Mullaney, J.; Leiton, R.; Walter, F.; Hodge, J.; Charmandaris, V.; Riechers, D.; Carilli, C.; Scott, D.

    2011-10-10

    We explore the gas-to-dust mass ratio (M{sub gas}/M{sub d}) and the CO luminosity-to-M{sub gas} conversion factor ({alpha}{sub CO}) of two well-studied galaxies in the Great Observatories Origins Deep Survey North field that are expected to have different star-forming modes, the starburst GN20 at z = 4.05 and the normal star-forming galaxy BzK-21000 at z = 1.52. Detailed sampling is available for their Rayleigh-Jeans emission via ground-based millimeter (mm) interferometry (1.1-6.6 mm) along with Herschel PACS and SPIRE data that probe the peak of their infrared emission. Using the physically motivated Draine and Li models, as well as a modified blackbody function, we measure the dust mass (M{sub dust}) of the sources and find (2.0{sup +0.7} {sub -0.6} x 10{sup 9}) M{sub sun} for GN20 and (8.6{sup +0.6} {sub -0.9} x 10{sup 8}) M{sub sun} for BzK-21000. The addition of mm data reduces the uncertainties of the derived M{sub dust} by a factor of {approx}2, allowing the use of the local M{sub gas}/M{sub d} versus metallicity relation to place constraints on the {alpha}{sub CO} values of the two sources. For GN20 we derive a conversion factor of {alpha}{sub CO} < 1.0 M{sub sun} pc{sup -2} (K km s{sup -1}){sup -1}, consistent with that of local ultra-luminous infrared galaxies, while for BzK-21000 we find a considerably higher value, {alpha}{sub CO} {approx}4.0 M{sub sun} pc{sup -2} (K km s{sup -1}){sup -1}, in agreement with an independent kinematic derivation reported previously. The implied star formation efficiency is {approx}25 L{sub sun}/M{sub sun} for BzK-21000, a factor of {approx}5-10 lower than that of GN20. The findings for these two sources support the existence of different disk-like and starburst star formation modes in distant galaxies, although a larger sample is required to draw statistically robust results.

  15. The Role of Star Formation and AGN in Dust Heating of z=0.3-2.8 Galaxies - II. Informing IR AGN Fraction Estimates through Simulations

    NASA Astrophysics Data System (ADS)

    Roebuck, Eric; Sajina, Anna; Hayward, Christopher C.; Pope, Alexandra; Kirkpatrick, Allison; Hernquist, Lars; Yan, Lin

    2016-12-01

    A key question in extragalactic studies is the determination of the relative roles of stars and active galactic nuclei (AGNs) in powering dusty galaxies at z ˜ 1-3 where the bulk of star formation and AGN activity took place. In Paper I, we present a sample of 336 24 μm selected (Ultra)Luminous Infrared Galaxies, (U)LIRGs, at z˜ 0.3-2.8, where we focus on determining the AGN contribution to the IR luminosity. Here, we use hydrodynamic simulations with dust radiative transfer of isolated and merging galaxies to investigate how well the simulations reproduce our empirical IR AGN fraction estimates and determine how IR AGN fractions relate to the UV-mm AGN fraction. We find that: (1) IR AGN fraction estimates based on simulations are in qualitative agreement with the empirical values when host reprocessing of the AGN light is considered; (2) for star-forming galaxy (SFG)-AGN composites our empirical methods may be underestimating the role of AGN, as our simulations imply \\gt 50 % AGN fractions, ˜ 3× higher than previous estimates; (3) 6% of our empirically classified SFGs have AGN fractions ≳50%. While this is a small percentage of SFGs, if confirmed it would imply that the true number density of AGNs may be underestimated; (4) this comparison depends on the adopted AGN template—those that neglect the contribution of warm dust lower the empirical fractions by up to two times; and (5) the IR AGN fraction is only a good proxy for the intrinsic UV-mm AGN fraction when the extinction is high ({A}V≳ 1 or up to and including coalescence in a merger).

  16. The Interacting Galaxy Pair KPG 390: Hα Kinematics

    NASA Astrophysics Data System (ADS)

    Repetto, P.; Rosado, M.; Gabbasov, R.; Fuentes-Carrera, I.

    2010-04-01

    In this work, we present scanning Fabry-Perot (FP) Hα observations of the isolated interacting galaxy pair NGC 5278/79 obtained with the PUMA FP interferometer. We derived velocity fields and rotation curves for both galaxies. For NGC 5278 we also obtained the residual velocity map to investigate the non-circular motions, and estimated its mass by fitting the rotation curve with disk+halo components. We test three different types of halos (pseudo-isothermal, Hernquist, and Navarro-Frenk-White) and obtain satisfactory fits to the rotation curve for all profiles. The amount of dark matter required by the pseudo-isothermal profile is about 10 times smaller than that for the other two halo distributions. Finally, our kinematical results together with the analysis of dust lane distribution and of surface brightness profiles along the minor axis allowed us to determine univocally that both components of the interacting pair are trailing spirals.

  17. THE INTERACTING GALAXY PAIR KPG 390: H{alpha} KINEMATICS

    SciTech Connect

    Repetto, P.; Rosado, M.; Gabbasov, R.; Fuentes-Carrera, I.

    2010-04-15

    In this work, we present scanning Fabry-Perot (FP) H{alpha} observations of the isolated interacting galaxy pair NGC 5278/79 obtained with the PUMA FP interferometer. We derived velocity fields and rotation curves for both galaxies. For NGC 5278 we also obtained the residual velocity map to investigate the non-circular motions, and estimated its mass by fitting the rotation curve with disk+halo components. We test three different types of halos (pseudo-isothermal, Hernquist, and Navarro-Frenk-White) and obtain satisfactory fits to the rotation curve for all profiles. The amount of dark matter required by the pseudo-isothermal profile is about 10 times smaller than that for the other two halo distributions. Finally, our kinematical results together with the analysis of dust lane distribution and of surface brightness profiles along the minor axis allowed us to determine univocally that both components of the interacting pair are trailing spirals.

  18. Gas inflow patterns and nuclear rings in barred galaxies

    NASA Astrophysics Data System (ADS)

    Shen, Juntai; Li, Zhi

    2017-06-01

    Nuclear rings, dust lanes, and nuclear spirals are common structures in the inner region of barred galaxies, with their shapes and properties linked to the physical parameters of the galaxies. We use high-resolution hydrodynamical simulations to study gas inflow patterns in barred galaxies, with special attention on the nuclear rings. The location and thickness of nuclear ringsare tightly correlated with galactic properties, such as the bar pattern speed and bulge central density, within certain ranges. We identify the backbone of nuclear rings with a major orbital family of bars. The rings form exactly at the radius where the residual angular momentum of inflowing gas balances the centrifugal force. We propose a new simple method to predict the bar pattern speed for barred galaxies possessing a nuclear ring, without actually doing simulations. We apply this method to some real galaxies and find that our predicted bar pattern speed compare reasonably well with other estimates. Our study may have important implications for using nuclear ringsto measure the parameters of real barred galaxies with detailed gas kinematics. We have also extended current hydrodynamical simulations to model gas features in the Milky Way.

  19. Feathers in CO: CARMA CO(1-0) Observations of Four Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    La Vigne, Misty A.; Vogel, S. N.

    2007-12-01

    Feathers are striking extinction features that emerge from a spiral arm dust lane and arch into the interarm. Based on a study of HST archival images, La Vigne et al. 2006 find that feathers are common in a range of spiral galaxy types, and that observations of M51 suggest feathers emerge from giant molecular associations (GMAs) and can be associated with much of the star formation in a spiral galaxy. To evaluate whether the conclusions based on M51 can be more generally applied, we have observed CO(1-0) emission in four spiral galaxies at 2-3” resolution using the newly operational CARMA millimeter wave array. Maps of NGC 0628, NGC 3627, NGC 4637, and NGC 5055 are presented and implications for theories for the origin of feathers are discussed. CARMA operations are supported by the NSF under a cooperative agreement, and by the partner universities.

  20. Performance of Driver-Vehicle in Aborted Lane Change Maneuvers

    NASA Technical Reports Server (NTRS)

    Lee, Allan Y.

    1995-01-01

    A 'lane change crash' is defined as a family of collisions that occurred when a driver attempts to change lane and strikes or is struck by a vehicle in the adjacent lane. One type of maneuver that is commonly used to avert a lane change crash involved aborting the intended lane change, and returning the vehicle to the original lane of the subject vehicle.

  1. A Grazing Encounter Between Two Spiral Galaxies

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The larger and more massive galaxy is cataloged as NGC 2207 (on the left in the Hubble Heritage image), and the smaller one on the right is IC 2163. Strong tidal forces from NGC 2207 have distorted the shape of IC 2163, flinging out stars and gas into long streamers stretching out a hundred thousand light-years toward the right-hand edge of the image. Computer simulations, carried out by a team led by Bruce and Debra Elmegreen, demonstrate the leisurely timescale over which galactic collisions occur. In addition to the Hubble images, measurements made with the National Science Foundation's Very Large Array Radio Telescope in New Mexico reveal the motions of the galaxies and aid the reconstruction of the collision. The calculations indicate that IC 2163 is swinging past NGC 2207 in a counterclockwise direction, having made its closest approach 40 million years ago. However, IC 2163 does not have sufficient energy to escape from the gravitational pull of NGC 2207, and is destined to be pulled back and swing past the larger galaxy again in the future. The high resolution of the Hubble telescope image reveals dust lanes in the spiral arms of NGC 2207, clearly silhouetted against IC 2163, which is in the background. Hubble also reveals a series of parallel dust filaments extending like fine brush strokes along the tidally stretched material on the right-hand side. The large concentrations of gas and dust in both galaxies may well erupt into regions of active star formation in the near future. Trapped in their mutual orbit around each other, these two galaxies will continue to distort and disrupt each other. Eventually, billions of years from now, they will merge into a single, more massive galaxy. It is believed that many present-day galaxies, including the Milky Way, were assembled from a similar process of coalescence of smaller galaxies occurring over billions of years. This image was created from 3 separate pointings of Hubble. The Wide Field Planetary Camera 2 data

  2. Hubble Reveals Sombrero Galaxy (M104)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    In the 19th century, astronomer V. M. Slipher first discovered a hat-like object that appeared to be rushing away from us at 700 miles per second. This enormous velocity offered some of the earliest clues that it was really another galaxy, and that the universe was expanding in all directions. The trained razor sharp eye of the Hubble Space Telescope (HST) easily resolves this Sombrero galaxy, Messier 104 (M104). The galaxy is 50,000 light-years across and is located 28 million light-years from Earth at the southern edge of the rich Virgo cluster of galaxies. Equivalent to 800 billion suns, Sombrero is one of the most massive objects in that group. The hallmark of Sombrero is a brilliant white, bulbous core encircled by the thick dust lanes comprising the spiral structure of the galaxy. As seen from Earth, the galaxy is tilted nearly edge-on. We view it from just six degrees north of its equatorial plane. At a relatively bright magnitude of +8, M104 is just beyond the limit of naked-eye visibility and is easily seen through small telescopes. This rich system of globular clusters are estimated to be nearly 2,000 in number which is 10 times as many as in our Milky Way galaxy. The ages of the clusters are similar to the clusters in the Milky Way, ranging from 10-13 billion years old. Embedded in the bright core of M104 is a smaller disk, which is tilted relative to the large disk. X-ray emission suggests that there is material falling into the compact core, where a 1-billion-solar-mass black hole resides. The Marshall Space Flight Center (MSFC) had responsibility for design, development, and construction of the HST.

  3. Hubble Reveals Sombrero Galaxy (M104)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    In the 19th century, astronomer V. M. Slipher first discovered a hat-like object that appeared to be rushing away from us at 700 miles per second. This enormous velocity offered some of the earliest clues that it was really another galaxy, and that the universe was expanding in all directions. The trained razor sharp eye of the Hubble Space Telescope (HST) easily resolves this Sombrero galaxy, Messier 104 (M104). The galaxy is 50,000 light-years across and is located 28 million light-years from Earth at the southern edge of the rich Virgo cluster of galaxies. Equivalent to 800 billion suns, Sombrero is one of the most massive objects in that group. The hallmark of Sombrero is a brilliant white, bulbous core encircled by the thick dust lanes comprising the spiral structure of the galaxy. As seen from Earth, the galaxy is tilted nearly edge-on. We view it from just six degrees north of its equatorial plane. At a relatively bright magnitude of +8, M104 is just beyond the limit of naked-eye visibility and is easily seen through small telescopes. This rich system of globular clusters are estimated to be nearly 2,000 in number which is 10 times as many as in our Milky Way galaxy. The ages of the clusters are similar to the clusters in the Milky Way, ranging from 10-13 billion years old. Embedded in the bright core of M104 is a smaller disk, which is tilted relative to the large disk. X-ray emission suggests that there is material falling into the compact core, where a 1-billion-solar-mass black hole resides. The Marshall Space Flight Center (MSFC) had responsibility for design, development, and construction of the HST.

  4. Ultra-faint Ultraviolet Galaxies at z ~ 2 behind the Lensing Cluster A1689: The Luminosity Function, Dust Extinction, and Star Formation Rate Density

    NASA Astrophysics Data System (ADS)

    Alavi, Anahita; Siana, Brian; Richard, Johan; Stark, Daniel P.; Scarlata, Claudia; Teplitz, Harry I.; Freeman, William R.; Dominguez, Alberto; Rafelski, Marc; Robertson, Brant; Kewley, Lisa

    2014-01-01

    We have obtained deep ultraviolet imaging of the lensing cluster A1689 with the WFC3/UVIS camera onboard the Hubble Space Telescope in the F275W (30 orbits) and F336W (4 orbits) filters. These images are used to identify z ~ 2 star-forming galaxies via their Lyman break, in the same manner that galaxies are typically selected at z >= 3. Because of the unprecedented depth of the images and the large magnification provided by the lensing cluster, we detect galaxies 100× fainter than previous surveys at this redshift. After removing all multiple images, we have 58 galaxies in our sample in the range -19.5 < M 1500 < -13 AB mag. Because the mass distribution of A1689 is well constrained, we are able to calculate the intrinsic sensitivity of the observations as a function of source plane position, allowing for accurate determinations of effective volume as a function of luminosity. We fit the faint-end slope of the luminosity function to be α = -1.74 ± 0.08, which is consistent with the values obtained for 2.5 < z < 6. Notably, there is no turnover in the luminosity function down to M 1500 = -13 AB mag. We fit the UV spectral slopes with photometry from existing Hubble optical imaging. The observed trend of increasingly redder slopes with luminosity at higher redshifts is observed in our sample, but with redder slopes at all luminosities and average reddening of langE(B - V)rang = 0.15 mag. We assume the stars in these galaxies are metal poor (0.2 Z ⊙) compared to their brighter counterparts (Z ⊙), resulting in bluer assumed intrinsic UV slopes and larger derived values for dust extinction. The total UV luminosity density at z ~ 2 is 4.31^{+0.68}_{-0.60} \\times 10^{26} erg s-1 Hz-1 Mpc-3, more than 70% of which is emitted by galaxies in the luminosity range of our sample. Finally, we determine the global star formation rate density from UV-selected galaxies at z ~ 2 (assuming a constant dust extinction correction of 4.2 over all luminosities and a Kroupa initial

  5. The Most Luminous Heavily Obscured Quasars Have a High Merger Fraction: Morphological Study of WISE-selected Hot Dust-obscured Galaxies

    NASA Astrophysics Data System (ADS)

    Fan, Lulu; Han, Yunkun; Fang, Guanwen; Gao, Ying; Zhang, Dandan; Jiang, Xiaoming; Wu, Qiaoqian; Yang, Jun; Li, Zhao

    2016-05-01

    Previous studies have shown that Wide-field Infrared Survey Explorer-selected hyperluminous, hot dust-obscured galaxies (Hot DOGs) are powered by highly dust-obscured, possibly Compton-thick active galactic nuclei (AGNs). High obscuration provides us a good chance to study the host morphology of the most luminous AGNs directly. We analyze the host morphology of 18 Hot DOGs at z ˜ 3 using Hubble Space Telescope/WFC3 imaging. We find that Hot DOGs have a high merger fraction (62 ± 14%). By fitting the surface brightness profiles, we find that the distribution of Sérsic indices in our Hot DOG sample peaks around 2, which suggests that most Hot DOGs have transforming morphologies. We also derive the AGN bolometric luminosity (˜1014 L ⊙) of our Hot DOG sample by using IR spectral energy distributions decomposition. The derived merger fraction and AGN bolometric luminosity relation is well consistent with the variability-based model prediction. Both the high merger fraction in an IR-luminous AGN sample and relatively low merger fraction in a UV/optical-selected, unobscured AGN sample can be expected in the merger-driven evolutionary model. Finally, we conclude that Hot DOGs are merger-driven and may represent a transit phase during the evolution of massive galaxies, transforming from the dusty starburst-dominated phase to the unobscured QSO phase.

  6. STScI-PRC95-30 HUBBLE SEES DETAILED NEW STRUCTURES IN THREE RADIO GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    These Hubble Space Telescope images, combined with radio maps produced by the Very Large Array Radio Interferometer (blue contour lines), show surprisingly varied and intricate structures of gas and stars that suggest the mechanisms powering radio galaxies are more complex than thought previously. The bizarre, never before seen detail may be a combination of light from massive star forming regions, small satellite dwarf galaxies, and bow shocks caused by jets of hot gas blasted out of the galaxies' cores by suspected black holes. [LEFT] - 3C265. Hubble resolves numerous bright star clusters or dwarf 'satellite' galaxies surrounding a bright central compact structure. The line corresponds to the axis of the galaxy's radio emissions, which unlike other radio galaxies, is in a different direction from the optical region. The star forming regions might result from a collision between galaxies. The jet that produces the radio emissions might have further intensified star formation. [CENTER] - 3C324. A number of small interacting components are distributed roughly along the radio axis in this source. Comparison of the Hubble image with that from the United Kingdom Infrared Telescope suggests that the central regions of this galaxy are obscured by a large dust lane. [RIGHT] - 3C368. One of the best studied radio galaxies, this image is composed of a very smooth cigar-shaped emission region closely aligned with the radio axis, upon which is superimposed a string of bright knots that might be stars or dust. This suggests that a jet of high speed gas, presumably ejected from a black hole at the core of the galaxy, might be triggering star formation along its path. Credit: M. Longair (Cambridge University, England), NASA, and NRAO

  7. Hubble Peers at the Heart of a Spiral Galaxy

    NASA Image and Video Library

    2017-09-27

    This new Hubble image is centered on NGC 5793, a spiral galaxy over 150 million light-years away in the constellation of Libra. This galaxy has two particularly striking features: a beautiful dust lane and an intensely bright center — much brighter than that of our own galaxy, or indeed those of most spiral galaxies we observe. NGC 5793 is a Seyfert galaxy. These galaxies have incredibly luminous centers that are thought to be caused by hungry supermassive black holes — black holes that can be billions of times the size of the sun — that pull in and devour gas and dust from their surroundings. This galaxy is of great interest to astronomers for many reasons. For one, it appears to house objects known as masers. Whereas lasers emit visible light, masers emit microwave radiation. The term "masers" comes from the acronym Microwave Amplification by Stimulated Emission of Radiation. Maser emission is caused by particles that absorb energy from their surroundings and then re-emit this in the microwave part of the spectrum. Naturally occurring masers, like those observed in NGC 5793, can tell us a lot about their environment; we see these kinds of masers in areas where stars are forming. In NGC 5793 there are also intense mega-masers, which are thousands of times more luminous than the sun. Credit: NASA, ESA, and E. Perlman (Florida Institute of Technology) NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  8. FORMATION OF DENSE MOLECULAR GAS AND STARS AT THE CIRCUMNUCLEAR STARBURST RING IN THE BARRED GALAXY NGC 7552

    SciTech Connect

    Pan, Hsi-An; Lim, Jeremy; Matsushita, Satoki; Wong, Tony; Ryder, Stuart

    2013-05-01

    We present millimeter molecular line complemented by optical observations, along with a reanalysis of archival centimeter H I and continuum data, to infer the global dynamics and determine where dense molecular gas and massive stars preferentially form in the circumnuclear starburst ring of the barred-spiral galaxy NGC 7552. We find diffuse molecular gas in a pair of dust lanes each running along the large-scale galactic bar, as well as in the circumnuclear starburst ring. We do not detect dense molecular gas in the dust lanes, but find such gas concentrated in two knots where the dust lanes make contact with the circumnuclear starburst ring. When convolved to the same angular resolution as the images in dense gas, the radio continuum emission of the circumnuclear starburst ring also exhibits two knots, each lying downstream of an adjacent knot in dense gas. The results agree qualitatively with the idea that massive stars form from dense gas at the contact points, where diffuse gas is channeled into the ring along the dust lanes, and later explode as supernovae downstream of the contact points. Based on the inferred rotation curve, however, the propagation time between the respective pairs of dense gas and centimeter continuum knots is about an order of magnitude shorter than the lifetimes of OB stars. We discuss possible reasons for this discrepancy, and conclude that either the initial mass function is top-heavy or massive stars in the ring do not form exclusively at the contact points where dense molecular gas is concentrated.

  9. Star Formation Laws in Both Galactic Massive Clumps and External Galaxies: Extensive Study with Dust Coninuum, HCN (4-3), and CS (7-6)

    NASA Astrophysics Data System (ADS)

    Liu, Tie; Kim, Kee-Tae; Yoo, Hyunju; Liu, Sheng-yuan; Tatematsu, Ken'ichi; Qin, Sheng-Li; Zhang, Qizhou; Wu, Yuefang; Wang, Ke; Goldsmith, Paul F.; Juvela, Mika; Lee, Jeong-Eun; Tóth, L. Viktor; Mardones, Diego; Garay, Guido; Bronfman, Leonardo; Cunningham, Maria R.; Li, Di; Lo, Nadia; Ristorcelli, Isabelle; Schnee, Scott

    2016-10-01

    We observed 146 Galactic clumps in HCN (4-3) and CS (7-6) with the Atacama Submillimeter Telescope Experiment 10 m telescope. A tight linear relationship between star formation rate and gas mass traced by dust continuum emission was found for both Galactic clumps and the high redshift (z > 1) star forming galaxies (SFGs), indicating a constant gas depletion time of ˜100 Myr for molecular gas in both Galactic clumps and high z SFGs. However, low z galaxies do not follow this relation and seem to have a longer global gas depletion time. The correlations between total infrared luminosities (L TIR) and molecular line luminosities ({L}{mol}\\prime ) of HCN (4-3) and CS (7-6) are tight and sublinear extending down to clumps with L TIR ˜ 103 L ⊙. These correlations become linear when extended to external galaxies. A bimodal behavior in the L TIR-{L}{mol}\\prime correlations was found for clumps with different dust temperature, luminosity-to-mass ratio, and σ line/σ vir. Such bimodal behavior may be due to evolutionary effects. The slopes of L TIR-L‧mol correlations become more shallow as clumps evolve. We compared our results with lower J transition lines in Wu et al. (2010). The correlations between clump masses and line luminosities are close to linear for low effective excitation density tracers but become sublinear for high effective excitation density tracers for clumps with L TIR larger than L TIR ˜ 104.5 L ⊙. High effective excitation density tracers cannot linearly trace the total clump masses, leading to a sublinear correlations for both M clump-L‧mol and L TIR-L‧mol relations.

  10. The Kiloparsec-scale Star Formation Law at Redshift 4: Widespread, Highly Efficient Star Formation in the Dust-obscured Starburst Galaxy GN20

    NASA Astrophysics Data System (ADS)

    Hodge, J. A.; Riechers, D.; Decarli, R.; Walter, F.; Carilli, C. L.; Daddi, E.; Dannerbauer, H.

    2015-01-01

    We present high-resolution observations of the 880 μm (rest-frame FIR) continuum emission in the z = 4.05 submillimeter galaxy GN20 from the IRAM Plateau de Bure Interferometer (PdBI). These data resolve the obscured star formation (SF) in this unlensed galaxy on scales of 0.''3 × 0.''2 (~2.1 × 1.3 kpc). The observations reveal a bright (16 ± 1 mJy) dusty starburst centered on the cold molecular gas reservoir and showing a bar-like extension along the major axis. The striking anti-correlation with the Hubble Space Telescope/Wide Field Camera 3 imaging suggests that the copious dust surrounding the starburst heavily obscures the rest-frame UV/optical emission. A comparison with 1.2 mm PdBI continuum data reveals no evidence for variations in the dust properties across the source within the uncertainties, consistent with extended SF, and the peak star formation rate surface density (119 ± 8 M ⊙ yr-1 kpc-2) implies that the SF in GN20 remains sub-Eddington on scales down to 3 kpc2. We find that the SF efficiency (SFE) is highest in the central regions of GN20, leading to a resolved SF law with a power-law slope of ΣSFR ~ Σ _H_2^2.1+/- 1.0, and that GN20 lies above the sequence of normal star-forming disks, implying that the dispersion in the SF law is not due solely to morphology or choice of conversion factor. These data extend previous evidence for a fixed SFE per free-fall time to include the star-forming medium on ~kiloparsec scales in a galaxy 12 Gyr ago. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

  11. Some stars are totally metal: a new mechanism driving dust across star-forming clouds, and consequences for planets, stars, and galaxies

    SciTech Connect

    Hopkins, Philip F.

    2014-12-10

    Dust grains in neutral gas behave as aerodynamic particles, so they can develop large local density fluctuations entirely independent of gas density fluctuations. Specifically, gas turbulence can drive order-of-magnitude 'resonant' fluctuations in the dust density on scales where the gas stopping/drag timescale is comparable to the turbulent eddy turnover time. Here we show that for large grains (size ≳ 0.1 μm, containing most grain mass) in sufficiently large molecular clouds (radii ≳ 1-10 pc, masses ≳ 10{sup 4} M {sub ☉}), this scale becomes larger than the characteristic sizes of prestellar cores (the sonic length), so large fluctuations in the dust-to-gas ratio are imprinted on cores. As a result, star clusters and protostellar disks formed in large clouds should exhibit significant abundance spreads in the elements preferentially found in large grains (C, O). This naturally predicts populations of carbon-enhanced stars, certain highly unusual stellar populations observed in nearby open clusters, and may explain the 'UV upturn' in early-type galaxies. It will also dramatically change planet formation in the resulting protostellar disks, by preferentially 'seeding' disks with an enhancement in large carbonaceous or silicate grains. The relevant threshold for this behavior scales simply with cloud densities and temperatures, making straightforward predictions for clusters in starbursts and high-redshift galaxies. Because of the selective sorting by size, this process is not necessarily visible in extinction mapping. We also predict the shape of the abundance distribution—when these fluctuations occur, a small fraction of the cores may actually be seeded with abundances Z ∼ 100 (Z) such that they are almost 'totally metal' (Z ∼ 1)! Assuming the cores collapse, these totally metal stars would be rare (1 in ∼10{sup 4} in clusters where this occurs), but represent a fundamentally new stellar evolution channel.

  12. Kinematics of NGC 4826: A sleeping beauty galaxy, not an evil eye

    NASA Technical Reports Server (NTRS)

    Rubin, Vera C.

    1994-01-01

    A recent high resolution H I study of the Sab galaxy NGC 4826 (1992) reveals that the sense of rotation of the neutral gas reverses from the inner to the outer disk. The present paper reports on optical spectra at high velocity resolution in four position angles in NGC 4826, which cover the region of the gas reversal and which reveal a high degree of complexity. In the inner disk, which includes the prominent dusty lane, the stars and gas rotate in concert, and the spiral arms trail (for the adopted geometry). Arcs of ionized gas are observed partially encircling the nucleus; expansion velocities reach 400 km/s. At distances just beyond the prominent dust lane, the ionized gas exhibits a rapid, orderly velocity fall and within 500 parsecs it has reversed from 180 km/s prograde to 200 km/s retrograde; it also has a component radial toward the nucleus of over 100 km/s. The stars, however, continue their prograde rotation. Beyond this transition zone, the neutral gas continues its retrograde rotation, stellar velocities are prograde, but the sense of the almost circular arms is not established. Because of its kinematical complexity as well as its proximity, NGC 4826 is an excellent early-type galaxy in which to observe the long term effects of gas acquistion or a galaxy merger on a disk galaxy.

  13. Kinematics of NGC 4826: A sleeping beauty galaxy, not an evil eye

    NASA Technical Reports Server (NTRS)

    Rubin, Vera C.

    1994-01-01

    A recent high resolution H I study of the Sab galaxy NGC 4826 (1992) reveals that the sense of rotation of the neutral gas reverses from the inner to the outer disk. The present paper reports on optical spectra at high velocity resolution in four position angles in NGC 4826, which cover the region of the gas reversal and which reveal a high degree of complexity. In the inner disk, which includes the prominent dusty lane, the stars and gas rotate in concert, and the spiral arms trail (for the adopted geometry). Arcs of ionized gas are observed partially encircling the nucleus; expansion velocities reach 400 km/s. At distances just beyond the prominent dust lane, the ionized gas exhibits a rapid, orderly velocity fall and within 500 parsecs it has reversed from 180 km/s prograde to 200 km/s retrograde; it also has a component radial toward the nucleus of over 100 km/s. The stars, however, continue their prograde rotation. Beyond this transition zone, the neutral gas continues its retrograde rotation, stellar velocities are prograde, but the sense of the almost circular arms is not established. Because of its kinematical complexity as well as its proximity, NGC 4826 is an excellent early-type galaxy in which to observe the long term effects of gas acquistion or a galaxy merger on a disk galaxy.

  14. Far-infrared Properties of Infrared-bright Dust-obscured Galaxies Selected with IRAS and AKARI Far-infrared All-sky Survey

    NASA Astrophysics Data System (ADS)

    Toba, Yoshiki; Nagao, Tohru; Wang, Wei-Hao; Matsuhara, Hideo; Akiyama, Masayuki; Goto, Tomotsugu; Koyama, Yusei; Ohyama, Youich; Yamamura, Issei

    2017-05-01

    We investigate the star-forming activity of a sample of infrared (IR)-bright dust-obscured galaxies (DOGs) that show an extreme red color in the optical and IR regime, {(i-[22])}{AB}> 7.0. Combining an IR-bright DOG sample with the flux at 22 μm > 3.8 mJy discovered by Toba & Nagao with the IRAS faint source catalog version 2 and AKARI far-IR (FIR) all-sky survey bright source catalog version 2, we selected 109 DOGs with FIR data. For a subsample of seven IR-bright DOGs with spectroscopic redshifts (0.07< z< 1.0) that were obtained from the literature, we estimated their IR luminosity, star formation rate (SFR), and stellar mass based on the spectral energy distribution fitting. We found that (1) the WISE 22 μm luminosity at the observed frame is a good indicator of IR luminosity for IR-bright DOGs and (2) the contribution of the active galactic nucleus to IR luminosity increases with IR luminosity. By comparing the stellar mass and SFR relation for our DOG sample and the literature, we found that most of the IR-bright DOGs lie significantly above the main sequence of star-forming galaxies at similar redshift, indicating that the majority of IRAS- or AKARI-detected IR-bright DOGs are starburst galaxies.

  15. FIRST DETECTION OF ULTRAVIOLET EMISSION FROM A DETACHED DUST SHELL: GALAXY EVOLUTION EXPLORER OBSERVATIONS OF THE CARBON ASYMPTOTIC GIANT BRANCH STAR U Hya

    SciTech Connect

    Sanchez, Enmanuel; Montez, Rodolfo Jr.; Stassun, Keivan G.; Ramstedt, Sofia

    2015-01-10

    We present the discovery of an extended ring of ultraviolet (UV) emission surrounding the asymptotic giant branch (AGB) star U Hya in archival observations performed by the Galaxy Evolution Explorer. This is the third discovery of extended UV emission from a carbon AGB star and the first from an AGB star with a detached shell. From imaging and photometric analysis of the FUV and NUV images, we determined that the UV ring has a radius of ∼110'', thus indicating that the emitting material is likely associated with the detached shell seen in the infrared. We find that scattering of the central point source of NUV and FUV emission by the dust shell is negligible. Moreover, we find that scattering of the interstellar radiation field by the dust shell can contribute at most ∼10% of the FUV flux. Morphological and photometric evidence suggests that shocks caused by the star's motion through space and, possibly, shock-excited H{sub 2} molecules are the most likely origins of the UV flux. In contrast to previous examples of extended UV emission from AGB stars, the extended UV emission from U Hya does not show a bow-shock-like structure, which is consistent with a lower space velocity and lower interstellar medium density. This suggests the detached dust shell is the source of the UV-emitting material and can be used to better understand the formation of detached shells.

  16. Road Lane Detection by Discriminating Dashed and Solid Road Lanes Using a Visible Light Camera Sensor

    PubMed Central

    Hoang, Toan Minh; Hong, Hyung Gil; Vokhidov, Husan; Park, Kang Ryoung

    2016-01-01

    With the increasing need for road lane detection used in lane departure warning systems and autonomous vehicles, many studies have been conducted to turn road lane detection into a virtual assistant to improve driving safety and reduce car accidents. Most of the previous research approaches detect the central line of a road lane and not the accurate left and right boundaries of the lane. In addition, they do not discriminate between dashed and solid lanes when detecting the road lanes. However, this discrimination is necessary for the safety of autonomous vehicles and the safety of vehicles driven by human drivers. To overcome these problems, we propose a method for road lane detection that distinguishes between dashed and solid lanes. Experimental results with the Caltech open database showed that our method outperforms conventional methods. PMID:27548176

  17. Road Lane Detection by Discriminating Dashed and Solid Road Lanes Using a Visible Light Camera Sensor.

    PubMed

    Hoang, Toan Minh; Hong, Hyung Gil; Vokhidov, Husan; Park, Kang Ryoung

    2016-08-18

    With the increasing need for road lane detection used in lane departure warning systems and autonomous vehicles, many studies have been conducted to turn road lane detection into a virtual assistant to improve driving safety and reduce car accidents. Most of the previous research approaches detect the central line of a road lane and not the accurate left and right boundaries of the lane. In addition, they do not discriminate between dashed and solid lanes when detecting the road lanes. However, this discrimination is necessary for the safety of autonomous vehicles and the safety of vehicles driven by human drivers. To overcome these problems, we propose a method for road lane detection that distinguishes between dashed and solid lanes. Experimental results with the Caltech open database showed that our method outperforms conventional methods.

  18. Magnetic fields in barred galaxies. I. The atlas

    NASA Astrophysics Data System (ADS)

    Beck, R.; Shoutenkov, V.; Ehle, M.; Harnett, J. I.; Haynes, R. F.; Shukurov, A.; Sokoloff, D. D.; Thierbach, M.

    2002-08-01

    The total and polarized radio continuum emission of 20 barred galaxies was observed with the Very Large Array (VLA) at lambda 3, 6, 18 and 22 cm and with the Australia Telescope Compact Array (ATCA) at lambda 6 cm and 13 cm. Maps at 30\\arcsec angular resolution are presented here. Polarized emission (and therefore a large-scale regular magnetic field) was detected in 17 galaxies. Most galaxies of our sample are similar to non-barred galaxies with respect to the radio/far-infrared flux correlation and equipartition strength of the total magnetic field. Galaxies with highly elongated bars are not always radio-bright. We discuss the correlation of radio properties with the aspect ratio of the bar and other measures of the bar strength. We introduce a new measure of the bar strength, Lambda , related to the quadrupole moment of the bar's gravitational potential. The radio surface brightness I of the barred galaxies in our sample is correlated with Lambda , I~Lambda 0.4+/-0.1, and thus is highest in galaxies with a long bar where the velocity field is distorted by the bar over a large fraction of the disc. In these galaxies, the pattern of the regular field is significantly different from that in non-barred galaxies. In particular, field enhancements occur upstream of the dust lanes where the field lines are oriented at large angles to the bar's major axis. Polarized radio emission seems to be a good indicator of large-scale non-axisymmetric motions. Tables 3, 4 and Figs. 8-10, 13, 15, 16, 18 and 22 are only available in electronic form at http://www.edpsciences.org

  19. Shipping lanes or offshore rigs

    SciTech Connect

    Not Available

    1980-09-01

    This information was from the Los Angeles Steamship Association (LASSA) luncheon meeting. The problems of limiting access and availability of the Santa Barbara/Santa Catalina channels to commercial vessel traffic and other related uses. LASSA speaks for about 85% of the maritime industry in Southern California. The Association is actively seeking a compromise with the oil companies in keeping the Vessel Traffic Separation Scheme (VTSS) in the channels; however, the Western Oil and Gas Association (WOGA) is seeking to abolish VTSS as currently established in the channels and move the sea lanes outside the Channel Islands, and open up the entire Santa Barbara Channel to unlimited drilling sites. LASSA claims that moving the VTSS sea lanes outside of the Channel Islands would add 18 to 22 miles to the average trip from San Francisco to Los Angeles, with fuel cost etc. would make for a big loss to the merchant ship operators. LASSA has offered to support the concept of opening up the Buffer Zone that separates the Sea Lanes themselves to exploratory drilling. This two mile wide stretch of water is off limits to vessels and it would open new areas to the oil companies heretofore unaccessible to them. (DP)