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Sample records for nearby starburst galaxy

  1. THE NATURE OF STARBURSTS. I. THE STAR FORMATION HISTORIES OF EIGHTEEN NEARBY STARBURST DWARF GALAXIES

    SciTech Connect

    McQuinn, Kristen B. W.; Skillman, Evan D.; Stark, David; Weisz, Daniel; Cannon, John M.; Dalcanton, Julianne; Williams, Benjamin; Dolphin, Andrew; Hidalgo-RodrIguez, Sebastian

    2010-09-20

    We use archival Hubble Space Telescope observations of resolved stellar populations to derive the star formation histories (SFHs) of 18 nearby starburst dwarf galaxies. In this first paper, we present the observations, color-magnitude diagrams (CMDs), and the SFHs of the 18 starburst galaxies, based on a homogeneous approach to the data reduction, differential extinction, and treatment of photometric completeness. We adopt a star formation rate (SFR) threshold normalized to the average SFR of the individual system as a metric for classifying starbursts in SFHs derived from resolved stellar populations. This choice facilitates finding not only the currently bursting galaxies but also 'fossil' bursts increasing the sample size of starburst galaxies in the nearby (D < 8 Mpc) universe. Thirteen of the eighteen galaxies are experiencing ongoing bursts and five galaxies show fossil bursts. From our reconstructed SFHs, it is evident that the elevated SFRs of a burst are sustained for hundreds of Myr with variations on small timescales. A long >100 Myr temporal baseline is thus fundamental to any starburst definition or identification method. The longer lived bursts rule out rapid 'self-quenching' of starbursts on global scales. The bursting galaxies' gas consumption timescales are shorter than the Hubble time for all but one galaxy confirming the short-lived nature of starbursts based on fuel limitations. Additionally, we find that the strength of the H{alpha} emission usually correlates with the CMD-based SFR during the last 4-10 Myr. However, in four cases, the H{alpha} emission is significantly less than what is expected for models of starbursts; the discrepancy is due to the SFR changing on timescales of a few Myr. The inherently short timescale of the H{alpha} emission limits identifying galaxies as starbursts based on the current characteristics which may or may not be representative of the recent SFH of a galaxy.

  2. The Nature of Starbursts. I. The Star Formation Histories of Eighteen Nearby Starburst Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    McQuinn, Kristen B. W.; Skillman, Evan D.; Cannon, John M.; Dalcanton, Julianne; Dolphin, Andrew; Hidalgo-Rodríguez, Sebastian; Holtzman, Jon; Stark, David; Weisz, Daniel; Williams, Benjamin

    2010-09-01

    We use archival Hubble Space Telescope observations of resolved stellar populations to derive the star formation histories (SFHs) of 18 nearby starburst dwarf galaxies. In this first paper, we present the observations, color-magnitude diagrams (CMDs), and the SFHs of the 18 starburst galaxies, based on a homogeneous approach to the data reduction, differential extinction, and treatment of photometric completeness. We adopt a star formation rate (SFR) threshold normalized to the average SFR of the individual system as a metric for classifying starbursts in SFHs derived from resolved stellar populations. This choice facilitates finding not only the currently bursting galaxies but also "fossil" bursts increasing the sample size of starburst galaxies in the nearby (D < 8 Mpc) universe. Thirteen of the eighteen galaxies are experiencing ongoing bursts and five galaxies show fossil bursts. From our reconstructed SFHs, it is evident that the elevated SFRs of a burst are sustained for hundreds of Myr with variations on small timescales. A long >100 Myr temporal baseline is thus fundamental to any starburst definition or identification method. The longer lived bursts rule out rapid "self-quenching" of starbursts on global scales. The bursting galaxies' gas consumption timescales are shorter than the Hubble time for all but one galaxy confirming the short-lived nature of starbursts based on fuel limitations. Additionally, we find that the strength of the Hα emission usually correlates with the CMD-based SFR during the last 4-10 Myr. However, in four cases, the Hα emission is significantly less than what is expected for models of starbursts; the discrepancy is due to the SFR changing on timescales of a few Myr. The inherently short timescale of the Hα emission limits identifying galaxies as starbursts based on the current characteristics which may or may not be representative of the recent SFH of a galaxy. Based on observations made with the NASA/ESA Hubble Space Telescope

  3. Ionized Gas Observation Toward a Nearby Starburst Galaxy NGC 253

    NASA Astrophysics Data System (ADS)

    Nakanishi, K.; Sorai, K.; Nakai, N.; Kuno, N.; Matsubayashi, K.; Sugai, H.; Takano, S.; Kohno, K.; Nakajima, T.

    2015-12-01

    ALMA observation of a hydrogen recombination emission line toward NGC 253 was performed. NGC 253 is a prototypical starburst galaxy in the nearby universe. The recombination line was clearly detected in the central region of NGC 253 with a spatial resolution of few dozens of parsecs at the galaxy. The line and thermal free-free continuum emission show quite similar spatial distribution, and this fact shows the recombination line certainly traces ionized gas formed by young massive stars. Estimated electron temperature (6500-9000K) from the data are similar to those of Galactic HII regions. The recombination line has large velocity width at the center of the galaxy, and the velocity structure is quite different from that of molecular emission line.

  4. Multi-Wavelength Observations of Nearby Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Janice

    2015-08-01

    Do cycles of violent, intense, but short-lived bursts constitute a significant mode of global star formation in present-day galaxies? Such events can have a profound effect on galaxies, particularly those with shallow potential wells, and observational measures of their prevalence inform our understanding of a wide range of issues in galaxy evolution. I will highlight what we have learned about starbursts from multi-wavelength observations of galaxies in the local volume on both galactic and smaller scales, and explore how connections with the study of the deaths of massive stars may further our understanding of open issues in galaxy evolution.

  5. (12)CO (3-2) & (1-0) emission line observations of nearby starburst galaxy nuclei

    NASA Technical Reports Server (NTRS)

    Devereux, Nicholas; Taniguchi, Yoshiaki; Sanders, D. B.; Nakai, N.; Young, J. S.

    1994-01-01

    New measurements of the (12)CO (1-0) and (12)CO (3-2) line emission are presented for the nuclei of seven nearby starburst galaxies selected from a complete sample of 21 nearby starburst galaxies for which the nuclear star formation rates are measured to be comparable to the archetype starburst galaxies M82 and NGC 253. The new observations capitalize on the coincidence between the beam size of the 45 m Nobeyama telescope at 115 GHz and that of the 15 m James Clerk Maxwell Telescope at 345 GHz to measure the value of the (12)CO (3-2)/(1-0) emission line ratio in a 15 sec (less than or equal to 2.5 kpc) diameter region centered on the nuclear starburst. In principle, the (12)CO (3-2)/(1-0) emission line ratio provides a measure of temperature and optical depth for the (12)CO gas. The error weighted mean value of the (12)CO (3-2)/(1-0) emission line ratio measured for the seven starburst galaxy nuclei is -0.64 +/- 0.06. The (12)CO (3-2)/(1-0) emission line ratio measured for the starburst galaxy nuclei is significantly higher than the average value measured for molecular gas in the disk of the Galaxy, implying warmer temperatures for the molecular gas in starburst galaxy nuclei. On the other hand, the (12)CO (3-2)/(1-0) emission line ratio measured for the starburst galaxy nuclei is not as high as would be expected if the molecular gas were hot, greater than 20 K, and optically thin, tau much less than 1. The total mass of molecular gas contained within the central 1.2-2.8 kpc diameter region of the starburst galaxy nuclei ranges from 10(exp 8) to 10(exp 9) solar mass. While substantial, the molecular gas mass represents only a small percentage, approximately 9%-16%, of the dynamical mass in the same region.

  6. PROPERTIES OF NEARBY STARBURST GALAXIES BASED ON THEIR DIFFUSE GAMMA-RAY EMISSION

    SciTech Connect

    Paglione, Timothy A. D.; Abrahams, Ryan D.

    2012-08-20

    The physical relationship between the far-infrared and radio fluxes of star-forming galaxies has yet to be definitively determined. The favored interpretation, the 'calorimeter model', requires that supernova generated cosmic-ray (CR) electrons cool rapidly via synchrotron radiation. However, this cooling should steepen their radio spectra beyond what is observed, and so enhanced ionization losses at low energies from high gas densities are also required. Further, evaluating the minimum energy magnetic field strength with the traditional scaling of the synchrotron flux may underestimate the true value in massive starbursts if their magnetic energy density is comparable to the hydrostatic pressure of their disks. Gamma-ray spectra of starburst galaxies, combined with radio data, provide a less ambiguous estimate of these physical properties in starburst nuclei. While the radio flux is most sensitive to the magnetic field, the GeV gamma-ray spectrum normalization depends primarily on gas density. To this end, spectra above 100 MeV were constructed for two nearby starburst galaxies, NGC 253 and M82, using Fermi data. Their nuclear radio and far-infrared spectra from the literature are compared to new models of the steady-state CR distributions expected from starburst galaxies. Models with high magnetic fields, favoring galaxy calorimetry, are overall better fits to the observations. These solutions also imply relatively high densities and CR ionization rates, consistent with molecular cloud studies.

  7. OBSERVATIONAL CONSTRAINTS ON THE MOLECULAR GAS CONTENT IN NEARBY STARBURST DWARF GALAXIES

    SciTech Connect

    McQuinn, Kristen B. W.; Skillman, Evan D.; Dalcanton, Julianne J.; Weisz, Daniel R.; Williams, Benjamin F.; Dolphin, Andrew E.; Cannon, John M.; Holtzman, Jon

    2012-06-01

    Using star formation histories derived from optically resolved stellar populations in 19 nearby starburst dwarf galaxies observed with the Hubble Space Telescope, we measure the stellar mass surface densities of stars newly formed in the bursts. By assuming a star formation efficiency (SFE), we then calculate the inferred gas surface densities present at the onset of the starbursts. Assuming an SFE of 1%, as is often assumed in normal star-forming galaxies, and assuming that the gas was purely atomic, translates to very high H I surface densities ({approx}10{sup 2}-10{sup 3} M{sub Sun} pc{sup -2}), which are much higher than have been observed in dwarf galaxies. This implies either higher values of SFE in these dwarf starburst galaxies or the presence of significant amounts of H{sub 2} in dwarfs (or both). Raising the assumed SFEs to 10% or greater (in line with observations of more massive starbursts associated with merging galaxies), still results in H I surface densities higher than observed in 10 galaxies. Thus, these observations appear to require that a significant fraction of the gas in these dwarf starbursts galaxies was in the molecular form at the onset of the bursts. Our results imply molecular gas column densities in the range 10{sup 19}-10{sup 21} cm{sup -2} for the sample. In the galaxies where CO observations have been made, these densities correspond to values of the CO-H{sub 2} conversion factor (X{sub CO}) in the range >(3-80) Multiplication-Sign 10{sup 20} cm{sup -2} (K km s{sup -1}){sup -1}, or up to 40 Multiplication-Sign greater than Galactic X{sub CO} values.

  8. Dynamics of starbursting dwarf galaxies. III. A H I study of 18 nearby objects

    NASA Astrophysics Data System (ADS)

    Lelli, Federico; Verheijen, Marc; Fraternali, Filippo

    2014-06-01

    We investigate the dynamics of starbursting dwarf galaxies, using both new and archival H I observations. We consider 18 nearby galaxies that have been resolved into single stars by HST observations, providing their star formation history and total stellar mass. We find that 9 objects have a regularly rotating H I disk, 7 have a kinematically disturbed H I disk, and 2 show unsettled H I distributions. Two galaxies (NGC 5253 and UGC 6456) show a velocity gradient along the minor axis of the H I disk, which we interpret as strong radial motions. For galaxies with a regularly rotating disk we derive rotation curves, while for galaxies with a kinematically disturbed disk, we estimate the rotation velocities in their outer parts. We derive baryonic fractions within about 3 optical scale lengths and find that, on average, baryons constitute at least 30% of the total mass. Despite the star formation having injected ~1056 ergs in the ISM in the past ~500 Myr, these starbursting dwarfs have both baryonic and gas fractions similar to those of typical dwarf irregulars, suggesting that they did not eject a large amount of gas out of their potential wells. Appendices are available in electronic form at http://www.aanda.orgH I datacubes (FITS files) are only 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/566/A71

  9. THEORETICAL EXPLANATION OF THE COSMIC-RAY PERPENDICULAR DIFFUSION COEFFICIENT IN THE NEARBY STARBURST GALAXY NGC 253

    SciTech Connect

    Buffie, K.; Shalchi, A.; Heesen, V. E-mail: v.heesen@soton.ac.uk

    2013-02-10

    Diffusion coefficients are usually used to describe the propagation of cosmic rays through the universe. Whereas such transport parameters can be obtained from experiments in the solar system, it is difficult to determine diffusion coefficients in the Milky Way or in external galaxies. Recently, a value for the perpendicular diffusion coefficient in the nearby starburst galaxy NGC 253 has been proposed. In the present paper, we reproduce this value theoretically by using an advanced analytical theory for perpendicular diffusion.

  10. Dense gas in nearby galaxies. XIII. CO submillimeter line emission from the starburst galaxy M 82

    NASA Astrophysics Data System (ADS)

    Mao, R. Q.; Henkel, C.; Schulz, A.; Zielinsky, M.; Mauersberger, R.; Störzer, H.; Wilson, T. L.; Gensheimer, P.

    2000-06-01

    12CO J = 1-0, 2-1, 4-3, 7-6, and 13CO 1-0, 2-1, and 3-2 line emission was mapped with angular resolutions of 13'' - 22'' toward the nuclear region of the archetypical starburst galaxy M 82. There are two hotspots on either side of the dynamical center, with the south-western lobe being slightly more prominent. Lobe spacings are not identical for all transitions: For the submillimeter CO lines, the spacing is ~ 15''; for the millimeter lines (CO J = 2-1 and 1-0) the spacing is ~ 26'', indicating the presence of a `low' and a `high' CO excitation component. A Large Velocity Gradient (LVG) excitation analysis of the submillimeter lines leads to inconsistencies, since area and volume filling factors are almost the same, resulting in cloud sizes along the lines-of-sight that match the entire size of the M 82 starburst region. Nevertheless, LVG column densities agree with estimates derived from the dust emission in the far infrared and at submillimeter wavelengths. 22'' beam averaged total column densities are N(CO) ~ 5 1018 and N(H_2) ~ 1023 \\cmsq; the total molecular mass is a few 108 \\solmass. Accounting for high UV fluxes and variations in kinetic temperature and assuming that the observed emission arises from photon dominated regions (PDRs) resolves the problems related to an LVG treatment of the radiative transfer. Spatial densities are as in the LVG case (\

  11. THE STAR CLUSTER SYSTEM IN THE NEARBY STARBURST GALAXY M82

    SciTech Connect

    Lim, Sungsoon; Lee, Myung Gyoon; Hwang, Narae E-mail: mglee@astro.snu.ac.kr

    2013-03-20

    We present a photometric study of star clusters in the nearby starburst galaxy M82 based on the UBVI-, YJ- and H-band Hubble Space Telescope images. We find 1105 star clusters with V < 23 mag. Of those, 1070 are located in the disk region, while 35 star clusters are in the halo region. The star clusters in the disk are composed of a dominant blue population with a color peak at (B - V){sub 0} Almost-Equal-To 0.45, and a weaker red population. The luminosity function of the disk clusters shows a power-law distribution with a power-law index {alpha} = -2.04 {+-} 0.03, and the scale height of their distribution is h{sub z} = 9.''64 {+-} 0.''40 (164 {+-} 7 pc), similar to that of the stellar thin disk of M82. We have derived the ages of {approx}630 star clusters using the spectral energy distribution fit method by comparing UBVI(YJ)H-band photometric data with the simple stellar population models. The age distribution of the disk clusters shows that the most dominant cluster population has ages ranging from 100 Myr to 1 Gyr, with a peak at about 500 Myr. This suggests that M82 has undergone a disk-wide star formation about 500 Myr ago, probably through the interaction with M81. The brightest star clusters in the nuclear region are much brighter than those in other regions, indicating that more massive star clusters are formed in the denser environments. On the other hand, the colors of the halo clusters are similar to those of globular clusters in the Milky Way, and their ages are estimated to be older than 1 Gyr. These are probably genuine old globular clusters in M82.

  12. THE GREEN BANK TELESCOPE MAPS THE DENSE, STAR-FORMING GAS IN THE NEARBY STARBURST GALAXY M82

    SciTech Connect

    Kepley, Amanda A.; Frayer, David; Leroy, Adam K.; Usero, Antonio; Walter, Fabian

    2014-01-01

    Observations of the Milky Way and nearby galaxies show that dense molecular gas correlates with recent star formation, suggesting that the formation of this gas phase may help regulate star formation. A key test of this idea requires wide-area, high-resolution maps of dense molecular gas in galaxies to explore how local physical conditions drive dense gas formation, but these observations have been limited because of the faintness of dense gas tracers like HCN and HCO{sup +}. Here we demonstrate the power of the Robert C. Byrd Green Bank Telescope (GBT)—the largest single-dish millimeter radio telescope—for mapping dense gas in galaxies by presenting the most sensitive maps yet of HCN and HCO{sup +} in the starburst galaxy M82. The HCN and HCO{sup +} in the disk of this galaxy correlates with both recent star formation and more diffuse molecular gas and shows kinematics consistent with a rotating torus. The HCO{sup +} emission extending to the north and south of the disk is coincident with the outflow previously identified in CO and traces the eastern edge of the hot outflowing gas. The central starburst region has a higher ratio of star formation to dense gas than the outer regions, pointing to the starburst as a key driver of this relationship. These results establish that the GBT can efficiently map the dense molecular gas at 90 GHz in nearby galaxies, a capability that will increase further with the 16 element feed array under construction.

  13. Spatially Resolved Stellar Populations Of Nearby Post-Starburst Galaxies In SDSS-IV MaNGA

    NASA Astrophysics Data System (ADS)

    Liu, Charles; Betances, Ashley; Bonilla, Alaina Marie; Gonzalez, Andrea; Migliore, Christina; Goddard, Daniel; Masters, Karen; SDSS-IV MaNGA Team

    2016-01-01

    We have selected five galaxies in the Mapping Nearby Galaxies at APO (MaNGA) project of the latest generation of the Sloan Digital Sky Survey (SDSS-IV) identified as post-starburst (E+A) systems, in the transition between "blue cloud" and "red sequence" galaxies. We measure the equivalent widths of the Balmer series, D4000 break, and metal lines across each galaxy, and produce maps of the stellar age, stellar mass, and metallicities of each galaxy using FIREFLY, a full spectral analysis code. We have found that the measured properties of the galaxies overall generally matches well with single-aperture SDSS spectra from which the original post-starburst identifications were made. The variation in the spatial distributions of the stellar populations, in particular the A-stars, give us insight into the details of the transitional E+A quenching phase. This work was supported by the Alfred P. Sloan Foundation via the SDSS-IV Faculty and Student Team (FAST) initiative, ARC Agreement No. SSP483 to the CUNY College of Staten Island.

  14. Cosmic ray interactions in starbursting galaxies

    NASA Astrophysics Data System (ADS)

    Yoast-Hull, Tova M.

    High quality gamma-ray and radio observations of nearby galaxies offer an unprecedented opportunity to quantitatively study the properties of their cosmic ray populations. Accounting for various interactions and energy losses, I developed a multi-component, single-zone model of the cosmic ray populations in the central molecular zones of star-forming galaxies. Using observational knowledge of the interstellar medium and star formation, I successfully predicted the radio, gamma-ray, and neutrino spectra for nearby starbursts. Using chi-squared tests to compare the models with observational radio and gamma-ray data, I placed constraints on magnetic field strengths, cosmic ray energy densities, and galactic wind (advection) speeds. The initial models were applied to and tested on the prototypical starburst galaxy M82. To further test the model and to explore the differences in environment between starbursts and active galactic nuclei, I studied NGC 253 and NGC 1068, both nearby giant spiral galaxies which have been detected in gamma-rays. Additionally, I demonstrated that the excess GeV energy gamma-ray emission in the Galactic Center is likely not diffuse emission from an additional population of cosmic rays accelerated in supernova remnants. Lastly, I investigated cosmic ray populations in the starburst nuclei of Arp 220, a nearby ultraluminous infrared galaxy which displays a high-intensity mode of star formation more common in young galaxies, and I showed that the nuclei are efficient cosmic-ray proton calorimeters.

  15. Starburst Galaxy NGC 3310

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Scientists using NASA's Hubble Space Telescope are studying the colors of star clusters to determine the age and history of starburst galaxies, a technique somewhat similar to the process of learning the age of a tree by counting its rings.

    This month's Hubble Heritage image showcases the galaxy NGC 3310. It is one of several starburst galaxies, which are hotbeds of star formation, being studied by Dr. Gerhardt Meurer and a team of scientists at Johns Hopkins University, Laurel, Md.

    The picture, taken by Hubble's Wide Field and Planetary Camera 2, is online at http://heritage.stsci.edu and http://oposite.stsci.edu/pubinfo/pr/2001/26 and http://www.jpl.nasa.gov/images/wfpc . The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    Most galaxies form new stars at a fairly slow rate, but starburst galaxies blaze with extremely active star formation. Measuring the clusters' colors yields information about stellar temperatures. Since young stars are blue and older stars redder, the colors relate to their ages.

    NGC 3310 is forming clusters of new stars at a prodigious rate. The new image shows several hundred star clusters, visible as the bright blue, diffuse objects that trace the galaxy's spiral arms. Each of these star clusters represents the formation of up to about a million stars, a process that takes less than 100,000 years. In addition, hundreds of individual young, luminous stars can be seen throughout the galaxy.

    The star clusters become redder with age as the most massive and bluest stars exhaust their fuel and burn out. Measurements in this image of the wide range of cluster colors show their ages range between about one million and more than one hundred million years. This suggests that the starburst 'turned on' more than 100 million years ago. It may have been triggered when NGC 3310 collided with a companion galaxy.

    These observations may change astronomers' view of starbursts. Starbursts were once

  16. A UNIVERSAL, LOCAL STAR FORMATION LAW IN GALACTIC CLOUDS, NEARBY GALAXIES, HIGH-REDSHIFT DISKS, AND STARBURSTS

    SciTech Connect

    Krumholz, Mark R.; Dekel, Avishai; McKee, Christopher F. E-mail: dekel@phys.huji.ac.il

    2012-01-20

    Star formation laws are rules that relate the rate of star formation in a particular region, either an entire galaxy or some portion of it, to the properties of the gas, or other galactic properties, in that region. While observations of Local Group galaxies show a very simple, local star formation law in which the star formation rate per unit area in each patch of a galaxy scales linearly with the molecular gas surface density in that patch, recent observations of both Milky Way molecular clouds and high-redshift galaxies apparently show a more complicated relationship in which regions of equal molecular gas surface density can form stars at quite different rates. These data have been interpreted as implying either that different star formation laws may apply in different circumstances, that the star formation law is sensitive to large-scale galaxy properties rather than local properties, or that there are high-density thresholds for star formation. Here we collate observations of the relationship between gas and star formation rate from resolved observations of Milky Way molecular clouds, from kpc-scale observations of Local Group galaxies, and from unresolved observations of both disk and starburst galaxies in the local universe and at high redshift. We show that all of these data are in fact consistent with a simple, local, volumetric star formation law. The apparent variations stem from the fact that the observed objects have a wide variety of three-dimensional size scales and degrees of internal clumping, so even at fixed gas column density the regions being observed can have wildly varying volume densities. We provide a simple theoretical framework to remove this projection effect, and we use it to show that all the data, from small solar neighborhood clouds with masses {approx}10{sup 3} M{sub Sun} to submillimeter galaxies with masses {approx}10{sup 11} M{sub Sun }, fall on a single star formation law in which the star formation rate is simply {approx}1% of

  17. THE ACS NEARBY GALAXY SURVEY TREASURY. VII. THE NGC 4214 STARBURST AND THE EFFECTS OF STAR FORMATION HISTORY ON DWARF MORPHOLOGY

    SciTech Connect

    Williams, Benjamin F.; Dalcanton, Julianne J.; Gilbert, Karoline M.; Weisz, Daniel R.; Seth, Anil C.; Skillman, Evan D.; Dolphin, Andrew E. E-mail: jd@astro.washington.edu E-mail: dweisz@astro.washington.edu E-mail: skillman@astro.umn.edu

    2011-07-01

    We present deep Hubble Space Telescope WFPC2 optical observations obtained as part of the ACS Nearby Galaxy Survey Treasury as well as early release Wide Field Camera 3 ultraviolet and infrared observations of the nearby dwarf starbursting galaxy NGC 4214. Our data provide a detailed example of how covering such a broad range in wavelength provides a powerful tool for constraining the physical properties of stellar populations. The deepest data reach the ancient red clump at M{sub F814W} {approx} - 0.2. All of the optical data reach the main-sequence turnoff for stars younger than {approx}300 Myr and the blue He-burning sequence for stars younger than 500 Myr. The full color-magnitude diagram (CMD) fitting analysis shows that all three fields in our data set are consistent with {approx}75% of the stellar mass being older than 8 Gyr, in spite of showing a wide range in star formation rates at present. Thus, our results suggest that the scale length of NGC 4214 has remained relatively constant for many gigayears. As previously noted by others, we also find the galaxy has recently ramped up production consistent with its bright UV luminosity and its population of UV-bright massive stars. In the central field we find UV point sources with F336W magnitudes as bright as -9.9. These are as bright as stars with masses of at least 52-56 M{sub sun} and ages near 4 Myr in stellar evolution models. Assuming a standard initial mass function, our CMD is well fitted by an increase in star formation rate beginning 100 Myr ago. The stellar populations of this late-type dwarf are compared with those of NGC 404, an early-type dwarf that is also the most massive galaxy in its local environment. The late-type dwarf appears to have a similar high fraction of ancient stars, suggesting that these dominant galaxies may form at early epochs even if they have low total mass and very different present-day morphologies.

  18. Chandra Observations of Starburst Galaxies

    NASA Technical Reports Server (NTRS)

    Prestwich, Andrea; Lavoie, Anthony R. (Technical Monitor)

    2000-01-01

    We present early X-ray results from Chandra for two starburst galaxies, M82 and NGC3256, obtained using AXAF CCD Imaging Spectrometer (ACIS-I) and the HRC. For M82 the arcsecond spatial resolution enables us to separate the point source component from the extended emission for the first time. Astrometry reveals that most of the X-ray sources are not coincident with the family of compact radio sources believed to be Super Nova Remnants (SNRs). In addition, based on three epoch Chandra observations, several of the X-ray sources are clearly variable indicating that they are binaries. When we deconvolve the extended and point source components detected in the hard X-ray band, we find that 50 percent arises from the extended component. This fact, together with its morphology, constrains the various models proposed to explain the hard X-ray emission. For NGC3256 we resolve two closely separated nuclei. These new data support a pure starburst origin for the total X-ray emission rather than a composite AGN/starburst, thereby making NGC3256 one of the most X-ray luminous starburst galaxies known.

  19. THE NATURE OF STARBURSTS. II. THE DURATION OF STARBURSTS IN DWARF GALAXIES

    SciTech Connect

    McQuinn, Kristen B. W.; Skillman, Evan D.; Stark, David; Weisz, Daniel; Cannon, John M.; Dalcanton, Julianne; Williams, Benjamin; Dolphin, Andrew; Hidalgo-RodrIguez, Sebastian

    2010-11-20

    The starburst phenomenon can shape the evolution of the host galaxy and the surrounding intergalactic medium. The extent of the evolutionary impact is partly determined by the duration of the starburst, which has a direct correlation with both the amount of stellar feedback and the development of galactic winds, particularly for smaller mass dwarf systems. We measure the duration of starbursts in twenty nearby, ongoing, and 'fossil' starbursts in dwarf galaxies based on the recent star formation histories derived from resolved stellar population data obtained with the Hubble Space Telescope. Contrary to the shorter times of 3-10 Myr often cited, the starburst durations we measure range from 450to650 Myr in fifteen of the dwarf galaxies and up to 1.3 Gyr in four galaxies; these longer durations are comparable to or longer than the dynamical timescales for each system. The same feedback from massive stars that may quench the flickering star formation does not disrupt the overall burst event in our sample of galaxies. While five galaxies present fossil bursts, fifteen galaxies show ongoing bursts and thus the final durations may be longer than we report here for these systems. One galaxy shows a burst that has been ongoing for only 20 Myr; we are likely seeing the beginning of a burst event in this system. Using the duration of the starbursts, we calculate that the bursts deposited 10{sup 53.9}-10{sup 57.2} erg of energy into the interstellar medium through stellar winds and supernovae, and produced 3%-26% of the host galaxy's mass.

  20. The Nature of Starbursts. II. The Duration of Starbursts in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    McQuinn, Kristen B. W.; Skillman, Evan D.; Cannon, John M.; Dalcanton, Julianne; Dolphin, Andrew; Hidalgo-Rodríguez, Sebastian; Holtzman, Jon; Stark, David; Weisz, Daniel; Williams, Benjamin

    2010-11-01

    The starburst phenomenon can shape the evolution of the host galaxy and the surrounding intergalactic medium. The extent of the evolutionary impact is partly determined by the duration of the starburst, which has a direct correlation with both the amount of stellar feedback and the development of galactic winds, particularly for smaller mass dwarf systems. We measure the duration of starbursts in twenty nearby, ongoing, and "fossil" starbursts in dwarf galaxies based on the recent star formation histories derived from resolved stellar population data obtained with the Hubble Space Telescope. Contrary to the shorter times of 3-10 Myr often cited, the starburst durations we measure range from 450to650 Myr in fifteen of the dwarf galaxies and up to 1.3 Gyr in four galaxies; these longer durations are comparable to or longer than the dynamical timescales for each system. The same feedback from massive stars that may quench the flickering star formation does not disrupt the overall burst event in our sample of galaxies. While five galaxies present fossil bursts, fifteen galaxies show ongoing bursts and thus the final durations may be longer than we report here for these systems. One galaxy shows a burst that has been ongoing for only 20 Myr we are likely seeing the beginning of a burst event in this system. Using the duration of the starbursts, we calculate that the bursts deposited 1053.9-1057.2 erg of energy into the interstellar medium through stellar winds and supernovae, and produced 3%-26% of the host galaxy's mass. Based on 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., under NASA contract NAS 5-26555.

  1. Observing Nearby Galaxies with CCAT

    NASA Astrophysics Data System (ADS)

    Armus, Lee; Stacey, G. J.; Wilson, C.; Bolatto, A. D.; Rangwala, N.; Nikola, T.; Kauffmann, J.; Bertoldi, F.; Glenn, J.; CCAT Team

    2013-01-01

    CCAT, with its 25m primary, advanced detectors and fast mapping speed will be extremely adept at deep, large-scale surveys for distant, dusty galaxies in the early Universe, and the most deeply buried star-forming complexes in the Milky Way. However, since it will also be sensitive to low surface brightness emission from diffuse dust, and the key far-infrared and mm cooling lines of the ISM, CCAT will also be a superb telescope for studying nearby galaxies in exquisite detail. For the nearest systems (e.g. M83), CCAT will be able to produce diffraction-limited maps in the mid-J CO rotational lines, and the [CI] and [NII] fine-structure lines on physical scales approaching those of individual molecular clouds. For samples of luminous starburst galaxies out to 0.3-0.5, CCAT will offer unprecedented sensitivity and spatial resolution in the high-J CO lines which are critical for pinpointing X-ray dissociation regions heated by AGN. Here, we will outline the strong scientific case for using CCAT to map the cold dust, the molecular gas and the ionized and atomic interstellar medium in local galaxies.

  2. UPDATED NEARBY GALAXY CATALOG

    SciTech Connect

    Karachentsev, Igor D.; Makarov, Dmitry I.; Kaisina, Elena I.

    2013-04-15

    We present an all-sky catalog of 869 nearby galaxies having individual distance estimates within 11 Mpc or corrected radial velocities V{sub LG} < 600 km s{sup -1}. The catalog is a renewed and expanded version of the Catalog of Neighboring Galaxies by Karachentsev et al. It collects data on the following galaxy observables: angular diameters, apparent magnitudes in far-UV, B, and K{sub s} bands, H{alpha} and H I fluxes, morphological types, H I-line widths, radial velocities, and distance estimates. In this Local Volume (LV) sample, 108 dwarf galaxies still remain without measured radial velocities. The catalog yields also calculated global galaxy parameters: linear Holmberg diameter, absolute B magnitude, surface brightness, H I mass, stellar mass estimated via K-band luminosity, H I rotational velocity corrected for galaxy inclination, indicative mass within the Holmberg radius, and three kinds of ''tidal index,'' which quantify the local density environment. The catalog is supplemented with data based on the local galaxies, which presents their optical and available H{alpha} images, as well as other services. We briefly discuss the Hubble flow within the LV and different scaling relations that characterize galaxy structure and global star formation in them. We also trace the behavior of the mean stellar mass density, H I-mass density, and star formation rate density within the volume considered.

  3. Stellar Evolution in Starburst Galaxies

    NASA Technical Reports Server (NTRS)

    Conti, Peter

    2001-01-01

    The main thrust of the program was to obtain UV spectroscopy of a number of massive and hot luminous (OB type) stars in the nearby galaxy called the Small Magellanic Cloud (SMC). The objective was to analyze their atmospheres and winds so as to determine the effect of the lower abundance of the SIVIC on these parameters. Furthermore, the differences in evolution could be investigated. Additionally, the UV spectra themselves would be suitably weighted and systematically combined to provide a template for comparison to very distant galaxies formed in the early history of the Universe which also have a low abundance of elements. The spectra have been obtained and the analysis is proceeding, primarily by the groups in Munich and at STScl who are the leads for this project. Given the important role of the nearby SMC galaxy as a template of low metal abundance, I have begun to investigate the YOUNGEST phases of massive star birth, before the most massive and hottest stars become optically visible. Typically these stars form in clusters, in some cases having tens to hundreds of OB type stars. In this phase, each star is still buried in its natal cloud and visible only in the infrared (IR) from its self-heated dust and/or from radio free-free emission of the surrounding hydrogen (HII) region. Efforts to find and identify these buried clusters were conducted using a large radio telescope. A number of these were found and further analysis of the data is underway. These clusters are not visible optically, but ought to be seen in the IR, and are a likely topic for HST photometry on NICMOS. A proposal to do this will be made next semester. These objects are the precursors of the optically visible clusters that contain massive and hot luminous stars.

  4. AN IONIZATION CONE IN THE DWARF STARBURST GALAXY NGC 5253

    SciTech Connect

    Zastrow, Jordan; Oey, M. S.; Veilleux, Sylvain; McDonald, Michael; Martin, Crystal L.

    2011-11-01

    There are few observational constraints on how the escape of ionizing photons from starburst galaxies depends on galactic parameters. Here we report on the first major detection of an ionization cone in NGC 5253, a nearby starburst galaxy. This high-excitation feature is identified by mapping the emission-line ratios in the galaxy using [S III] {lambda}9069, [S II] {lambda}6716, and H{alpha} narrowband images from the Maryland-Magellan Tunable Filter at Las Campanas Observatory. The ionization cone appears optically thin, which suggests the escape of ionizing photons. The cone morphology is narrow with an estimated solid angle covering just 3% of 4{pi} steradians, and the young, massive clusters of the nuclear starburst can easily generate the radiation required to ionize the cone. Although less likely, we cannot rule out the possibility of an obscured active galactic nucleus source. An echelle spectrum along the minor axis shows complex kinematics that are consistent with outflow activity. The narrow morphology of the ionization cone supports the scenario that an orientation bias contributes to the difficulty in detecting Lyman continuum emission from starbursts and Lyman break galaxies.

  5. Starbursts and Galaxy Evolution: results from COSMOS survey.

    NASA Astrophysics Data System (ADS)

    Muñoz-Tuñón, C.; Hinojosa Goñi, R.; Jairo Méndez Abreu, J.; Sánchez Alméida, J.

    2016-06-01

    The search for starbursts galaxies in COSMOS database by a tailored procedure that uses the photometry from SUBARU, results in 220 targets at z<0.5. The typical mass of the starburst is 10^8 and its distribution is similar to that of the quiescent galaxies in the survey at the same redshift range. From the detailed analysis of the galaxies images using the HST, the star forming clumps are characterized. The galaxies are of three different kinds, Snot, Snot and diffuse light and multiple knots. The mass of the knots are typically one order of magnitude below that of the host galaxy and the clumps in multiple knot galaxies are bigger the closer they are to the center. The sSFR however does not change with the particular position of the burst in their host galaxy, which suggests a similar process independently of their location. This result applies also to the galaxies at the largest z range (0.9). Our interpretation is that the star formation is happening at all possible locations on the galaxy discs, possibly from gas accreted from the halo or the IGM, with clumps which grow as they spiral and get to the centermost regions. Our previous work on nearby SF -tadpole galaxies of similar mass reported metallicity drops coinciding with the location of the burst what we have interpreted as SF driven by cold flows. Our results in COSMOS would be consistent with a similar interpretation and a scenario in which medium mass disks are growing by gas accretion that show up as scattered starbursts knots.

  6. Mapping CS in starburst galaxies: Disentangling and characterising dense gas

    NASA Astrophysics Data System (ADS)

    Kelly, G.; Viti, S.; Bayet, E.; Aladro, R.; Yates, J.

    2015-06-01

    Aims: We observe the dense gas tracer CS in two nearby starburst galaxies to determine how the conditions of the dense gas varies across the circumnuclear regions in starburst galaxies. Methods: Using the IRAM-30m telescope, we mapped the distribution of the CS(2-1) and CS(3-2) lines in the circumnuclear regions of the nearby starburst galaxies NGC 3079 and NGC 6946. We also detected formaldehyde (H2CO) and methanol (CH3OH) in both galaxies. We marginally detect the isotopologue C34S. Results: We calculate column densities under LTE conditions for CS and CH3OH. Using the detections accumulated here to guide our inputs, we link a time and depth dependent chemical model with a molecular line radiative transfer model; we reproduce the observations, showing how conditions where CS is present are likely to vary away from the galactic centres. Conclusions: Using the rotational diagram method for CH3OH, we obtain a lower limit temperature of 14 K. In addition to this, by comparing the chemical and radiative transfer models to observations, we determine the properties of the dense gas as traced by CS (and CH3OH). We also estimate the quantity of the dense gas. We find that, provided there are between 105 and 106 dense cores in our beam, for both target galaxies, emission of CS from warm (T = 100-400 K), dense (n(H2) = 105-6 cm-3) cores, possibly with a high cosmic ray ionisation rate (ζ = 100ζ0) best describes conditions for our central pointing. In NGC 6946, conditions are generally cooler and/or less dense further from the centre, whereas in NGC 3079, conditions are more uniform. The inclusion of shocks allows for more efficient CS formation, which means that gas that is less dense by an order of magnitude is required to replicate observations in some cases.

  7. Starburst in the Interacting HII Galaxy II Zw 40 and in Non-Interacting HII Galaxies

    NASA Astrophysics Data System (ADS)

    Telles, E.

    2010-06-01

    In this poster, I summarize the results of our integral field spectroscopic observations of the nearby prototype of HII galaxies, II Zw 40. Observations with GMOS-IFU on GEMINI-North in the optical allowed us to make a detailed kinematic picture of the central starburst, while SINFONI with adaptive optics on the ESO-VLT gave us a near-IR view of the interplay between the ISM phases. Here, I also address the question that not all starbursts require an external trigger such as a galaxy-galaxy encounter, as it seems to be the case for a fraction of low luminosity HII galaxies. We speculate that these may form stars spontaneously like "popcorn in a pan".

  8. HETDEX: Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Drory, Niv; Gebhardt, K.; Jogee, S.; Fabricius, M.; Greene, J.; HETDEX Collaboration

    2012-01-01

    The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is a blind spectroscopic survey using the VIRUS instrument. VIRUS consists of 75 IFUs distributed across the 22-arcmin field of the upgraded 9.2-m HET. Each 50x50 arcsec IFU is made up of 448 1.5-arcsec fibers, and feeds a pair of spectrographs with a fixed bandpass of 350-550 nm and resolving power R 700. The IFUs have a fill-factor of 1/3 which will be filled-in by dithering. We cover 1/4.5 of our 300-square-degree main survey area with fibers. We reach m_AB 22.6 (21.5,20.7) at S/N 3 (5,10) per resolution element. With these limits, g 17 spiral galaxies will have S/N>3 per resolution element per fiber in the continuum to 2 effective radii, and emission line spectra to at least their optical radius. HETDEX will spatially resolve 4000 local galaxies to that limit without any pre-selection; an additional 9000 local galaxies will have spatially resolved spectroscopy beyond that limit. At g 19 we still obtain integrated galaxy spectra at S/N 10 per resolution element in the continuum. These spatially resolved absorption and emission spectra provide information on star formation, the state of the IGM, and stellar populations, as well as rotation curves for an unbiased galaxy sample unprecedented in size. Since a wealth of information about a galaxy's formation history is encoded in gradients across the galaxy, moving from single-fiber (SDSS-like) spectra to large samples of spatially resolved galaxy spectroscopy opens a new parameter space for future studies of galaxy formation.

  9. Infrared Line Ratios in Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Guiles, S.; Devost, D.; Houck, J. R.

    2004-12-01

    Infrared line ratios are especially well suited to probe the physical conditions in starburst galaxies because they are sensitive to the hardness of the stellar ionizing radiation and are less affected by interstellar extinction than lines at shorter wavelengths. We compare IR line ratios in starburst galaxies obtained by the Infrared Spectrograph (IRS)* on the Spitzer Space Telescope with theoretical models. The models use the STARBURST99 code to generate a spectral energy distribution of a stellar cluster which then serves as the input to the MAPPINGS III photoionization code. We explore various model parameters such as the initial mass function and star formation mode, and we present preliminary results for a number of galaxies in our sample. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA through Contract Number 1257184 issued by JPL/Caltech. * The IRS was a collaborative venture between Cornell University and Ball Aerospace Corporation funded by NASA through the Jet Propulsion Laboratory and the Ames Research Center.

  10. Ionized gas pressure correlates with star formation intensity in nearby starbursts

    NASA Astrophysics Data System (ADS)

    Jiang, Tianxing; Malhotra, Sangeeta; Yang, Huan

    2016-06-01

    We estimate the electron density of the ionized gas and thus the thermal pressure in HII regions; and compare that to the SFR (star formation rate) surface density for a combined sample of about 40 green peas and Lyman Break Analogs at z < 0.30. The electron density of the ionized gas is measured from sulfur line ratio ([SII] 6716 / 6731). We find that the SFR surface density is correlated with the electron density and the thermal pressure in HII regions for the star-forming galaxies with SFR surface density above a certain threshold. This work shows quantitatively the correlation between SFR surface density and electron density and that between SFR surface density and the thermal pressure in HII regions for the nearby starburst galaxies. This is consistent with theoretical models of disks (e.g. Kim et al. (2011) if we assume that the thermal pressure in HII regions is comparable to the total diffuse gas pressure at the midplane of the diffuse neutral gas. It is also in agreement with the results from star-forming galaxies at z ~ 2.5. We might infer that the starburst galaxies at low-redshift (z < 0.3) share similar physical properties to the galaxies at high redshift (z ~ 2.5).

  11. An Atlas of Starburst Galaxy Emission Lines

    NASA Astrophysics Data System (ADS)

    Meskhidze, Helen; Richardson, Chris T.; Ferland, Gary J.

    2015-01-01

    Recent observations of high ionization lines (e.g. [Ne V] and He II λ4686) from star-forming regions have prompted a need to study the production mechanisms of these high ionization lines. Our study addresses the following questions: 1. What are specific cloud parameters that influence the strength of emission lines in starburst galaxies? 2. How can these parameters be tuned in simulations to match observations? We adopt the locally optimally emitting cloud model, a model previously used to study AGN, for our study of star-forming regions. We present the results of hundreds of photoionization simulations spanning 15 orders of magnitude in hydrogen ionizing photon flux and 10 orders of magnitude in hydrogen density. We vary both properties of the starbursts (SEDs, evolutionary histories, ages), as well as cloud properties (such as the abundances and metallicity), tracking nearly 100 emission lines ranging from the UV to the near IR. Finally, we compare these results to the results of other studies on star-forming regions. The results of our photoionization calculations should prove useful for the analysis of starburst galaxy emission-line data.

  12. "Dead quasars" in nearby galaxies?

    PubMed

    Rees, M J

    1990-02-16

    The nuclei of some galaxies undergo violent activity, quasars being the most extreme instances of this phenomenon. Such activity is probably short-lived compared to galactic lifetimes, and was most prevalent when the universe was only about one-fifth of its present age. A massive black hole seems the inevitable end point of such activity, and dead quasars should greatly outnumber active ones. In recent years, studies of stellar motions in the cores of several nearby galaxies indicate the presence of central dark masses which could be black holes. This article discusses how such evidence might be corroborated, and the potential implications for our understanding of active galaxies and black holes.

  13. Far-infrared activity and starburst galaxies

    NASA Technical Reports Server (NTRS)

    Belfort, P.; Mochkovitch, R.; Dennefeld, M.

    1987-01-01

    After the IRAS discovery of galaxies with large far-infrared to blue luminosity ratio, it has been proposed that an enhanced star formation could be the origin of the far-infrared emission through dust heating. Whether a simple photometric model is able to account for the FIR and optical properties of IRAS galaxies was investigated. The L sub IR/L sub B ratio, (B-V) color and H sub alpha equivalent width of normal spirals are well reproduced with smooth star formation histories. In the case of starburst galaxies, several theoretical diagrams allow us to estimate the burst strength and extinction. L sub IR/L sub B ratio up to 100 can be rather easily reached, whereas extreme values probably require IMF truncated at the low end.

  14. The gas content in starburst galaxies

    NASA Technical Reports Server (NTRS)

    Mirabel, I. F.; Sanders, D. B.

    1987-01-01

    The results from two large and homogeneous surveys, one in H I, the other in CO, are used for a statistical review of the gaseous properties of bright infrared galaxies. A constant ratio between the thermal FIR radiation and nonthermal radio emission is a universal property of star formation in spiral galaxies. The current rate of star formation in starburst galaxies is found to be 3-20 times larger than in the Milky Way. Galaxies with the higher FIR luminosities and warmer dust, have the larger mass fractions of molecular to atomic interstellar gas, and in some instances, striking deficiencies of neutral hydrogen are found. A statistical blueshift of the optical systemic velocities relative to the radio systemic velocities, may be due to an outward motion of the optical line-emitting gas. From the high rates of star formation, and from the short times required for the depletion of the interstellar gas, it is concluded that the most luminous infrared galaxies represent a brief but important phase in the evolution of some galaxies, when two galaxies merge changing substantially their overall properties.

  15. Investigating Starburst Galaxy Emission Line Equivalent Widths

    NASA Astrophysics Data System (ADS)

    Meskhidze, Helen; Richardson, Chris T.

    2016-01-01

    Modeling star forming galaxies with spectral synthesis codes allows us to study the gas conditions and excitation mechanisms that are necessary to reproduce high ionization emission lines in both local and high-z galaxies. Our study uses the locally optimally-emitting clouds model to develop an atlas of starburst galaxy emission line equivalent widths. Specifically, we address the following question: What physical conditions are necessary to produce strong high ionization emission lines assuming photoionization via starlight? Here we present the results of our photoionization simulations: an atlas spanning 15 orders of magnitude in ionizing flux and 10 orders of magnitude in hydrogen density that tracks over 150 emission lines ranging from the UV to the near IR. Each simulation grid contains ~1.5x104 photoionization models calculated by supplying a spectral energy distribution, grain content, and chemical abundances. Specifically, we will be discussing the effects on the emission line equivalent widths of varying the metallicity of the cloud, Z = 0.2 Z⊙ to Z = 5.0 Z⊙, and varying the star-formation history, using the instantaneous and continuous evolution tracks and the newly released Starburst99 Geneva rotation tracks.

  16. NuSTAR Observations of Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Ptak, Andrew; Hornschemeier, Ann E.; Wik, Daniel R.; Yukita, Mihoko; Lehmer, Bret; Zezas, Andreas; Maccarone, Tom; Venters, Tonia M.; Antoniou, Vallia; Harrison, Fiona; Stern, Daniel; NuSTAR Starburst Team

    2016-01-01

    NuSTAR, the first satellite with hard X-ray focusing optics, opens up the possibility to not only detect starburstn galaxies above 10 keV for the first time but also characterize their hard X-ray properties. Here we present an overview of a NuSTAR program to survey seven normal/starburst galaxies: NGC 253, M82, M83, NGC 3256, NGC 3310, Arp 299, and M31. We also discuss data analysis strategies. All galaxies have been observed coordinated with either Chandra or XMM-Newton or both. The main results of these observations were: we characterized the typical starburst spectrum above 10 keV and showed that the spectrum is soft (photon index ~ 3) above 7 keV and determined that individually detected sources are generally black holes in a "transition" accretion state or neutron star systems accreting near the Eddington rate, and variability on time scales of weeks to months is typically detected. In the case of NGC 253 we decomposed the unresolved hard X-ray emission between background, unresolved binaries and truly diffuse flux and found that the diffuse flux upper limit is marginally above model predictions for inverse-Compton scattering of IR photons by cosmic rays.

  17. From starburst to quiescence: testing active galactic nucleus feedback in rapidly quenching post-starburst galaxies

    SciTech Connect

    Yesuf, Hassen M.; Faber, S. M.; Trump, Jonathan R.; Koo, David C.; Fang, Jerome J.; Liu, F. S.; Wild, Vivienne; Hayward, Christopher C.

    2014-09-10

    Post-starbursts are galaxies in transition from the blue cloud to the red sequence. Although they are rare today, integrated over time they may be an important pathway to the red sequence. This work uses Sloan Digital Sky Survey, the Galaxy Evolution Explorer, and Wide-field Infrared Survey Explorer observations to identify the evolutionary sequence from starbursts to fully quenched post-starbursts (QPSBs) in the narrow mass range log M(M {sub ☉}) = 10.3-10.7, and identifies 'transiting' post-starbursts (TPSBs) which are intermediate between these two populations. In this mass range, ∼0.3% of galaxies are starbursts, ∼0.1% are QPSBs, and ∼0.5% are the transiting types in between. The TPSBs have stellar properties that are predicted for fast-quenching starbursts and morphological characteristics that are already typical of early-type galaxies. The active galactic nucleus (AGN) fraction, as estimated from optical line ratios, of these post-starbursts is about three times higher (≳ 36% ± 8%) than that of normal star forming galaxies of the same mass, but there is a significant delay between the starburst phase and the peak of nuclear optical AGN activity (median age difference of ≳ 200 ± 100 Myr), in agreement with previous studies. The time delay is inferred by comparing the broadband near-NUV-to-optical photometry with stellar population synthesis models. We also find that starbursts and post-starbursts are significantly more dust obscured than normal star forming galaxies in the same mass range. About 20% of the starbursts and 15% of the TPSBs can be classified as 'dust-obscured galaxies' (DOGs), with a near-UV-to-mid-IR flux ratio of ≳ 900, while only 0.8% of normal galaxies are DOGs. The time delay between the starburst phase and AGN activity suggests that AGNs do not play a primary role in the original quenching of starbursts but may be responsible for quenching later low-level star formation by removing gas and dust during the post-starburst

  18. From Starburst to Quiescence: Testing Active Galactic Nucleus feedback in Rapidly Quenching Post-starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Yesuf, Hassen M.; Faber, S. M.; Trump, Jonathan R.; Koo, David C.; Fang, Jerome J.; Liu, F. S.; Wild, Vivienne; Hayward, Christopher C.

    2014-09-01

    Post-starbursts are galaxies in transition from the blue cloud to the red sequence. Although they are rare today, integrated over time they may be an important pathway to the red sequence. This work uses Sloan Digital Sky Survey, the Galaxy Evolution Explorer, and Wide-field Infrared Survey Explorer observations to identify the evolutionary sequence from starbursts to fully quenched post-starbursts (QPSBs) in the narrow mass range log M(M ⊙) = 10.3-10.7, and identifies "transiting" post-starbursts (TPSBs) which are intermediate between these two populations. In this mass range, ~0.3% of galaxies are starbursts, ~0.1% are QPSBs, and ~0.5% are the transiting types in between. The TPSBs have stellar properties that are predicted for fast-quenching starbursts and morphological characteristics that are already typical of early-type galaxies. The active galactic nucleus (AGN) fraction, as estimated from optical line ratios, of these post-starbursts is about three times higher (gsim 36% ± 8%) than that of normal star forming galaxies of the same mass, but there is a significant delay between the starburst phase and the peak of nuclear optical AGN activity (median age difference of >~ 200 ± 100 Myr), in agreement with previous studies. The time delay is inferred by comparing the broadband near-NUV-to-optical photometry with stellar population synthesis models. We also find that starbursts and post-starbursts are significantly more dust obscured than normal star forming galaxies in the same mass range. About 20% of the starbursts and 15% of the TPSBs can be classified as "dust-obscured galaxies" (DOGs), with a near-UV-to-mid-IR flux ratio of >~ 900, while only 0.8% of normal galaxies are DOGs. The time delay between the starburst phase and AGN activity suggests that AGNs do not play a primary role in the original quenching of starbursts but may be responsible for quenching later low-level star formation by removing gas and dust during the post-starburst phase.

  19. "Dead quasars" in nearby galaxies?

    PubMed

    Rees, M J

    1990-02-16

    The nuclei of some galaxies undergo violent activity, quasars being the most extreme instances of this phenomenon. Such activity is probably short-lived compared to galactic lifetimes, and was most prevalent when the universe was only about one-fifth of its present age. A massive black hole seems the inevitable end point of such activity, and dead quasars should greatly outnumber active ones. In recent years, studies of stellar motions in the cores of several nearby galaxies indicate the presence of central dark masses which could be black holes. This article discusses how such evidence might be corroborated, and the potential implications for our understanding of active galaxies and black holes. PMID:17746076

  20. STAR CLUSTER DISRUPTION IN THE STARBURST GALAXY MESSIER 82

    SciTech Connect

    Li, Shuo; Li, Chengyuan; De Grijs, Richard; Anders, Peter

    2015-01-01

    Using high-resolution, multiple-passband Hubble Space Telescope images spanning the entire optical/near-infrared wavelength range, we obtained a statistically complete U-band-selected sample of 846 extended star clusters across the disk of the nearby starburst galaxy M82. Based on a careful analysis of the clusters' spectral energy distributions, we determined their galaxy-wide age and mass distributions. The M82 clusters exhibit three clear peaks in their age distribution, thus defining relatively young, log (t yr{sup –1}) ≤ 7.5, intermediate-age, log (t yr{sup –1}) in [7.5, 8.5], and old samples, log (t yr{sup –1}) ≥ 8.5. Comparison of the completeness-corrected mass distributions offers a firm handle on the galaxy's star cluster disruption history. The most massive star clusters in the young and old samples are (almost) all concentrated in the most densely populated central region, while the intermediate-age sample's most massive clusters are more spatially dispersed, which may reflect the distribution of the highest-density gas throughout the galaxy's evolutionary history, combined with the solid-body nature of the galaxy's central region.

  1. Densitometry and Thermometry of Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Mangum, J. G.; Darling, J.; Menten, K. M.; Henkel, C.; Aalto, S.; Spaans, M.; van der Werf, P.; Ginsburg, A.; Fomalont, E.; Cotton, B.; Kent, B.

    2016-05-01

    With a goal toward deriving the physical conditions in external galaxies, we have conducted a survey and subsequent high spatial resolution imaging of formaldehyde (H2CO) and ammonia (NH3) emission and absorption in a sample of starburst galaxies. In this article we present the results from a subset of this survey which focuses on high spatial resolution measurements of volume density- and kinetic temperature-sensitive transitions of the H2CO molecule. The volume density structure toward the nuclear region of NGC 253 has been derived from θ ≃ 4 arcsec NRAO Very Large Array (VLA) measurements of the 110 - 111 and 211 - 212 K-doublet transitions of H2CO. The kinetic temperature structure toward NGC 253 and NGC 4945 has been derived from θ ≃ 0.5 - 1.0 arcsec measurements of the H2CO 3K-1K+1 - 2K-1K+1 (near 218 GHz) and 5K-1K+1 - 4K-1K+1 (near 365 GHz) transitions acquired using the Atacama Large Millimeter/submillimeter Array (ALMA). These measurements have allowed us to characterize the dense gas and kinetic temperature structure within these star forming galaxies, which is a first step toward associating dense star-forming gas and the heating processes at work within galaxies.

  2. Panchromatic observations of dwarf starburst galaxies: Infant super star clusters and a low-luminosity AGN

    NASA Astrophysics Data System (ADS)

    Reines, Amy Ellen

    2011-01-01

    Globular star clusters and supermassive black holes are fundamental components of today's massive galaxies, with origins dating back to the very early universe. Both globular clusters and the seeds of supermassive black holes are believed to have formed in the progenitors of modern massive galaxies, although the details are poorly understood. Direct observations of these low-mass, distant, and hence faint systems are unobtainable with current capabilities. However, gas-rich dwarf starburst galaxies in the local universe, analogous in many ways to protogalaxies at high-redshift, can provide critical insight into the early stages of galaxy evolution including the formation of globular clusters and massive black holes. This thesis presents a panchromatic study of nearby dwarf starburst galaxies harboring nascent globular clusters still embedded in their birth material. Infant clusters are identified via their production of thermal radio emission at centimeter wavelengths, which comes from dense gas ionized by young massive stars. By combining radio observations with complementary data at ultraviolet, optical and infrared wavelengths, we obtain a comprehensive view of massive clusters emerging from their gaseous and dusty birth cocoons. This thesis also presents the first example of a nearby dwarf starburst galaxy hosting an actively accreting massive central black hole. The black hole in this dwarf galaxy is unusual in that it is not associated with a bulge, a nuclear star cluster, or any other well-defined nucleus, likely reflecting an early phase of black hole and galaxy evolution that has not been previously observed.

  3. Starbursts: From 30 Doradus to Lyman Break Galaxies

    NASA Astrophysics Data System (ADS)

    de Grijs, R.; González Delgado, R. M.

    2005-05-01

    Starbursts are important features of early galaxy evolution. Many of the distant, high-redshift galaxies we are able to detect are in a starbursting phase, often apparently provoked by a violent gravitational interaction with another galaxy. In fact, if we did not know that major starbursts existed, these conference proceedings testify that we would indeed have difficulties explaining the key properties of the Universe! The enhanced synergy facilitated by the collaboration among observers using cutting-edge ground and space-based facilities, theorists and modellers has made these proceedings into a true reflection of the state of the art in this very rapidly evolving field.

  4. FISICA observations of the starburst galaxy, NGC 1569

    NASA Astrophysics Data System (ADS)

    Clark, D. M.; Eikenberry, S. S.; Raines, S. N.; Gruel, N.; Elston, R.; Guzman, R.; Julian, J.; Boreman, G.; Glenn, P. E.; Hull-Allen, C. G.; Hoffman, J.; Rodgers, M.; Thompson, K.; Flint, S.; Comstock, L.; Myrick, B.

    2006-06-01

    Using the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) we obtained observations of the dwarf starburst galaxy NGC 1569. We present our JH band spectra, particularly noting the existence of extended emission in Paschen β and He I.

  5. The ULX Population in the Starburst Galaxy NGC 253

    NASA Technical Reports Server (NTRS)

    Weaver, K. A.; Heckman, T. M.; Strickland, D. K.

    2004-01-01

    Optimism is mounting for the existence of intermediate mass black holes (IMBH), which occupy the mass spectrum somewhere between the stellar-mass and supermassive varieties. IMBH are naturally predicted by theoretical stellar and black hole evolution models, but the strong attention to them began only recently with the discovery of ultraluminous x-ray sources (ULX). If isotropic and accreting normally, ULX have luminosities tens to thousands of times greater than the Eddington luminosity of a neutron star or stellar-mass black hole. A standard interpretation of their x-ray flux implies that they are powered by IMBH. On the other hand, they may be stellar-mass black holes that are beamed or emit anisotropically. Therefore, the exact nature of ULX is highly controversial. ULX are common in starburst galaxies. At a distance of only 3 Mpc, NGC 253 is bright, nearby, and one of the best-studied starburst galaxies. Approximately 50 distinct x-ray point sources are detected in or near the plane of the galaxy. At least six of these are ULX, with luminosities greater than 10 times that expected for a stellar-mass, accreting compact object. We present new Chandra data from an 80 ksec observation of NGC 253 obtained in 2003 that provides high quality spectra of these sources. Comparing the 1999 and 2003 Chandra observations, the sources have varied significantly over the course of four years, with one of the ULX disappearing completely. The ULX spectra are similar to black-hole XRBs and at least one appears to possess an iron K line. We will discuss what insight these data provide for the nature of ULX in NGC 253 .

  6. HIGH-DENSITY MOLECULAR GAS PROPERTIES OF THE STARBURST GALAXY NGC 1614 REVEALED WITH ALMA

    SciTech Connect

    Imanishi, Masatoshi; Nakanishi, Kouichiro

    2013-09-15

    We present the results of HCN/HCO{sup +}/HNC J = 4-3 transition line observations of the nearby starburst galaxy NGC 1614, obtained with ALMA Cycle 0. We find that high density molecular gas traced with these lines shows a velocity structure such that the northern (southern) side of the nucleus is redshifted (blueshifted) with respect to the nuclear velocity of this galaxy. The redshifted and blueshifted emission peaks are offset by {approx}0.''6 at the northern and southern sides of the nucleus, respectively. At these offset positions, observations at infrared >3 {mu}m indicate the presence of active dusty starbursts, supporting the picture that high-density molecular gas is the site of active starbursts. The enclosed dynamical mass within the central {approx}2'' in radius, derived from the dynamics of the high-density molecular gas, is {approx}10{sup 9} M{sub Sun }, which is similar to previous estimates. Finally, the HCN emission is weaker than HCO{sup +} but stronger than HNC for J = 4-3 for all starburst regions of NGC 1614, as seen for J = 1-0 transition lines in starburst-dominated galaxies.

  7. Hierarchical Star Formation in Nearby LEGUS Galaxies

    NASA Astrophysics Data System (ADS)

    Elmegreen, Debra Meloy; Elmegreen, Bruce G.; Adamo, Angela; Aloisi, Alessandra; Andrews, Jennifer; Annibali, Francesca; Bright, Stacey N.; Calzetti, Daniela; Cignoni, Michele; Evans, Aaron S.; Gallagher, John S., III; Gouliermis, Dimitrios A.; Grebel, Eva K.; Hunter, Deidre A.; Johnson, Kelsey; Kim, Hwihyun; Lee, Janice; Sabbi, Elena; Smith, Linda J.; Thilker, David; Tosi, Monica; Ubeda, Leonardo

    2014-05-01

    Hierarchical structure in ultraviolet images of 12 late-type LEGUS galaxies is studied by determining the numbers and fluxes of nested regions as a function of size from ~1 to ~200 pc, and the number as a function of flux. Two starburst dwarfs, NGC 1705 and NGC 5253, have steeper number-size and flux-size distributions than the others, indicating high fractions of the projected areas filled with star formation. Nine subregions in seven galaxies have similarly steep number-size slopes, even when the whole galaxies have shallower slopes. The results suggest that hierarchically structured star-forming regions several hundred parsecs or larger represent common unit structures. Small galaxies dominated by only a few of these units tend to be starbursts. The self-similarity of young stellar structures down to parsec scales suggests that star clusters form in the densest parts of a turbulent medium that also forms loose stellar groupings on larger scales. The presence of super star clusters in two of our starburst dwarfs would follow from the observed structure if cloud and stellar subregions more readily coalesce when self-gravity in the unit cell contributes more to the total gravitational potential.

  8. HIERARCHICAL STAR FORMATION IN NEARBY LEGUS GALAXIES

    SciTech Connect

    Elmegreen, Debra Meloy; Elmegreen, Bruce G.; Adamo, Angela; Gouliermis, Dimitrios A.; Aloisi, Alessandra; Bright, Stacey N.; Cignoni, Michele; Lee, Janice; Sabbi, Elena; Andrews, Jennifer; Calzetti, Daniela; Annibali, Francesca; Evans, Aaron S.; Johnson, Kelsey; Gallagher III, John S.; Grebel, Eva K.; Hunter, Deidre A.; Kim, Hwihyun; Smith, Linda J.; Thilker, David; and others

    2014-05-20

    Hierarchical structure in ultraviolet images of 12 late-type LEGUS galaxies is studied by determining the numbers and fluxes of nested regions as a function of size from ∼1 to ∼200 pc, and the number as a function of flux. Two starburst dwarfs, NGC 1705 and NGC 5253, have steeper number-size and flux-size distributions than the others, indicating high fractions of the projected areas filled with star formation. Nine subregions in seven galaxies have similarly steep number-size slopes, even when the whole galaxies have shallower slopes. The results suggest that hierarchically structured star-forming regions several hundred parsecs or larger represent common unit structures. Small galaxies dominated by only a few of these units tend to be starbursts. The self-similarity of young stellar structures down to parsec scales suggests that star clusters form in the densest parts of a turbulent medium that also forms loose stellar groupings on larger scales. The presence of super star clusters in two of our starburst dwarfs would follow from the observed structure if cloud and stellar subregions more readily coalesce when self-gravity in the unit cell contributes more to the total gravitational potential.

  9. Detection of gamma rays from a starburst galaxy.

    PubMed

    Acero, F; Aharonian, F; Akhperjanian, A G; Anton, G; Barres de Almeida, U; Bazer-Bachi, A R; Becherini, Y; Behera, B; Bernlöhr, K; Bochow, A; Boisson, C; Bolmont, J; Borrel, V; Brucker, J; Brun, F; Brun, P; Bühler, R; Bulik, T; Büsching, I; Boutelier, T; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Chounet, L-M; Clapson, A C; Coignet, G; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubois, F; Dubus, G; Dyks, J; Dyrda, M; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Fegan, S; Feinstein, F; Fiasson, A; Förster, A; Fontaine, G; Füssling, M; Gabici, S; Gallant, Y A; Gérard, L; Gerbig, D; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Göring, D; Hauser, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Hofverberg, P; Hoppe, S; Horns, D; Jacholkowska, A; de Jager, O C; Jahn, C; Jung, I; Katarzyński, K; Katz, U; Kaufmann, S; Kerschhaggl, M; Khangulyan, D; Khélifi, B; Keogh, D; Klochkov, D; Kluźniak, W; Kneiske, T; Komin, Nu; Kosack, K; Kossakowski, R; Lamanna, G; Lenain, J-P; Lohse, T; Marandon, V; Martineau-Huynh, O; Marcowith, A; Masbou, J; Maurin, D; McComb, T J L; Medina, M C; Méhault, J; Moderski, R; Moulin, E; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Nicholas, B; Niemiec, J; Nolan, S J; Ohm, S; Olive, J-F; de Oña Wilhelmi, E; Orford, K J; Ostrowski, M; Panter, M; Paz Arribas, M; Pedaletti, G; Pelletier, G; Petrucci, P-O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raubenheimer, B C; Raue, M; Rayner, S M; Reimer, O; Renaud, M; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Ruppel, J; Sahakian, V; Santangelo, A; Schlickeiser, R; Schöck, F M; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sikora, M; Skilton, J L; Sol, H; Stawarz, Ł; Steenkamp, R; Stegmann, C; Stinzing, F; Superina, G; Szostek, A; Tam, P H; Tavernet, J-P; Terrier, R; Tibolla, O; Tluczykont, M; van Eldik, C; Vasileiadis, G; Venter, C; Venter, L; Vialle, J P; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Wagner, S J; Ward, M; Zdziarski, A A; Zech, A

    2009-11-20

    Starburst galaxies exhibit in their central regions a highly increased rate of supernovae, the remnants of which are thought to accelerate energetic cosmic rays up to energies of approximately 10(15) electron volts. We report the detection of gamma rays--tracers of such cosmic rays--from the starburst galaxy NGC 253 using the High Energy Stereoscopic System (H.E.S.S.) array of imaging atmospheric Cherenkov telescopes. The gamma-ray flux above 220 billion electron volts is F = (5.5 +/- 1.0(stat) +/- 2.8(sys)) x 10(-13) cm(-2) s(-1), implying a cosmic-ray density about three orders of magnitude larger than that in the center of the Milky Way. The fraction of cosmic-ray energy channeled into gamma rays in this starburst environment is five times as large as that in our Galaxy.

  10. High resolution sub-millimetre mapping of starburst galaxies: Comparison with CO emission

    NASA Technical Reports Server (NTRS)

    Smith, P. A.; Brand, P. W. J. L.; Puxley, Phil J.; Mountain, C. M.; Nakai, Naomasa

    1990-01-01

    Researchers present first results from a program of submillimeter continuum mapping of starburst galaxies, and comparison of their dust and CO emission. This project was prompted by surprising results from the first target, the nearby starburst M82, which shows in the dust continuum a morphology quite unlike that of its CO emission, in contrast to what might be expected if both CO and dust are accurately tracing the molecular hydrogen. Possible explanations for this striking difference are discussed. In the light of these results, the program has been extended to include sub-mm mapping of the nearby, vigorously star forming spirals, M83 and Maffei 2. The latter were also observed extensively in CO, in order to study excitation conditions in its central regions. The James Clerk Maxwell Telescope was used in these studies.

  11. Comparing Local Starbursts to High-Redshift Galaxies: A Search for Lyman-Break Analogs

    NASA Technical Reports Server (NTRS)

    Petty, Sara M.; de Mello, Duila F.; Gallagher III, John S.; Gardner, Jonathan; Lotz, Jennifer M.; Mountain, C. Matt; Smith, Linda J.

    2008-01-01

    We compare the restframe far-ultraviolet (FUV) morphologies of 8 nearby interacting and starburst galaxies (Arp 269, M 82, Mrk 08, NGC 0520, NGC 1068, NGC 3079, NGC 3310, NGC 7673) with 54 galaxies at z approx.1.5 and 46 galaxies at z approx.4 in the Great Observatories Origins Deep Survey (GOODS) images taken with the Advanced Camera for Surveys onboard the Hubble Space Telescope. We calculate the Gini coefficient (G), the second order moment of 20% of the brightest pixels (M20), and the S ersic index (n). We find that 20% (11/54) of z approx.1.5 and 37% (17/46) of z approx.4 galaxies are bulge-like, using G and M20. We also find approx.70% of the z approx.1.5 and z approx.4 galaxies have exponential disks with n > 0.8. The 2D profile combined with the nonparametric methods provides more detail, concerning the nature of disturbed systems, such as merger and post-merger types. We also provide qualitative descriptions of each galaxy system and at each redshift. We conclude that Mrk 08, NGC 3079, and NGC 7673 have similar morphologies as the starburst FUV restframe galaxies and Lyman-break galaxies at z approx.1.5 and 4, and determine that they are Lyman-break analogs.

  12. ALMA Multi-line Imaging of the Nearby Starburst NGC 253

    NASA Astrophysics Data System (ADS)

    Meier, David S.; Walter, Fabian; Bolatto, Alberto D.; Leroy, Adam K.; Ott, Jürgen; Rosolowsky, Erik; Veilleux, Sylvain; Warren, Steven R.; Weiß, Axel; Zwaan, Martin A.; Zschaechner, Laura K.

    2015-03-01

    We present spatially resolved (~50 pc) imaging of molecular gas species in the central kiloparsec of the nearby starburst galaxy NGC 253, based on observations taken with the Atacama Large Millimeter/submillimeter Array. A total of 50 molecular lines are detected over a 13 GHz bandwidth imaged in the 3 mm band. Unambiguous identifications are assigned for 27 lines. Based on the measured high CO/C17O isotopic line ratio (gsim350), we show that 12CO(1-0) has moderate optical depths. A comparison of the HCN and HCO+ with their 13C-substituted isotopologues shows that the HCN(1-0) and HCO+(1-0) lines have optical depths at least comparable to CO(1-0). H13CN/H13CO+ (and H13CN/HN13C) line ratios provide tighter constraints on dense gas properties in this starburst. SiO has elevated abundances across the nucleus. HNCO has the most distinctive morphology of all the bright lines, with its global luminosity dominated by the outer parts of the central region. The dramatic variation seen in the HNCO/SiO line ratio suggests that some of the chemical signatures of shocked gas are being erased in the presence of dominating central radiation fields (traced by C2H and CN). High density molecular gas tracers (including HCN, HCO+, and CN) are detected at the base of the molecular outflow. We also detect hydrogen β recombination lines that, like their α counterparts, show compact, centrally peaked morphologies, distinct from the molecular gas tracers. A number of sulfur based species are mapped (CS, SO, NS, C2S, H2CS, and CH3SH) and have morphologies similar to SiO.

  13. ALMA MULTI-LINE IMAGING OF THE NEARBY STARBURST NGC 253

    SciTech Connect

    Meier, David S.; Walter, Fabian; Zschaechner, Laura K.; Bolatto, Alberto D.; Veilleux, Sylvain; Warren, Steven R.; Leroy, Adam K.; Ott, Jürgen; Rosolowsky, Erik; Weiß, Axel; Zwaan, Martin A.

    2015-03-01

    We present spatially resolved (∼50 pc) imaging of molecular gas species in the central kiloparsec of the nearby starburst galaxy NGC 253, based on observations taken with the Atacama Large Millimeter/submillimeter Array. A total of 50 molecular lines are detected over a 13 GHz bandwidth imaged in the 3 mm band. Unambiguous identifications are assigned for 27 lines. Based on the measured high CO/C{sup 17}O isotopic line ratio (≳350), we show that {sup 12}CO(1-0) has moderate optical depths. A comparison of the HCN and HCO{sup +} with their {sup 13}C-substituted isotopologues shows that the HCN(1-0) and HCO{sup +}(1-0) lines have optical depths at least comparable to CO(1-0). H{sup 13}CN/H{sup 13}CO{sup +} (and H{sup 13}CN/HN{sup 13}C) line ratios provide tighter constraints on dense gas properties in this starburst. SiO has elevated abundances across the nucleus. HNCO has the most distinctive morphology of all the bright lines, with its global luminosity dominated by the outer parts of the central region. The dramatic variation seen in the HNCO/SiO line ratio suggests that some of the chemical signatures of shocked gas are being erased in the presence of dominating central radiation fields (traced by C{sub 2}H and CN). High density molecular gas tracers (including HCN, HCO{sup +}, and CN) are detected at the base of the molecular outflow. We also detect hydrogen β recombination lines that, like their α counterparts, show compact, centrally peaked morphologies, distinct from the molecular gas tracers. A number of sulfur based species are mapped (CS, SO, NS, C{sub 2}S, H{sub 2}CS, and CH{sub 3}SH) and have morphologies similar to SiO.

  14. An actively accreting massive black hole in the dwarf starburst galaxy Henize2-10

    NASA Astrophysics Data System (ADS)

    Reines, Amy E.; Sivakoff, Gregory R.; Johnson, Kelsey E.; Brogan, Crystal L.

    2011-02-01

    Supermassive black holes are now thought to lie at the heart of every giant galaxy with a spheroidal component, including our own Milky Way. The birth and growth of the first `seed' black holes in the earlier Universe, however, is observationally unconstrained and we are only beginning to piece together a scenario for their subsequent evolution. Here we report that the nearby dwarf starburst galaxy Henize2-10 (refs 5 and 6) contains a compact radio source at the dynamical centre of the galaxy that is spatially coincident with a hard X-ray source. From these observations, we conclude that Henize2-10 harbours an actively accreting central black hole with a mass of approximately one million solar masses. This nearby dwarf galaxy, simultaneously hosting a massive black hole and an extreme burst of star formation, is analogous in many ways to galaxies in the infant Universe during the early stages of black-hole growth and galaxy mass assembly. Our results confirm that nearby star-forming dwarf galaxies can indeed form massive black holes, and that by implication so can their primordial counterparts. Moreover, the lack of a substantial spheroidal component in Henize2-10 indicates that supermassive black-hole growth may precede the build-up of galaxy spheroids.

  15. An actively accreting massive black hole in the dwarf starburst galaxy Henize 2-10.

    PubMed

    Reines, Amy E; Sivakoff, Gregory R; Johnson, Kelsey E; Brogan, Crystal L

    2011-02-01

    Supermassive black holes are now thought to lie at the heart of every giant galaxy with a spheroidal component, including our own Milky Way. The birth and growth of the first 'seed' black holes in the earlier Universe, however, is observationally unconstrained and we are only beginning to piece together a scenario for their subsequent evolution. Here we report that the nearby dwarf starburst galaxy Henize 2-10 (refs 5 and 6) contains a compact radio source at the dynamical centre of the galaxy that is spatially coincident with a hard X-ray source. From these observations, we conclude that Henize 2-10 harbours an actively accreting central black hole with a mass of approximately one million solar masses. This nearby dwarf galaxy, simultaneously hosting a massive black hole and an extreme burst of star formation, is analogous in many ways to galaxies in the infant Universe during the early stages of black-hole growth and galaxy mass assembly. Our results confirm that nearby star-forming dwarf galaxies can indeed form massive black holes, and that by implication so can their primordial counterparts. Moreover, the lack of a substantial spheroidal component in Henize 2-10 indicates that supermassive black-hole growth may precede the build-up of galaxy spheroids.

  16. Characterising molecular gas in nearby star forming galaxies

    NASA Astrophysics Data System (ADS)

    Kelly, George; Viti, Serena; Garcia-Burillo, Santiago

    2015-08-01

    Regions of very dense, star-forming gas in the interstellar medium are necessary to maintain star formation activity in hostile conditions. Star-forming regions in these environments are able to resist winds and radiative forces from newly formed stars longer than gas in the surrounding ISM. Subject to a proper interpretation, observations of molecules can be used for many purposes: tracing the reservoir or leftover of the star formation process; tracing the process of star formation itself; and determining the galaxy energetics through influence of newly-formed stars or an AGN on their environments. We map the distribution of several tracer molecules over three nearby galaxies. We begin by mapping two starburst galaxies with single dish observations of the dense gas tracer CS. The formation of CS is modelled under different conditions with results fed into a molecular line radiative transfer model. From this we can obtain the physical conditions of the regions of the ISM where there is a high rate of star-formation, as well as compare how the conditions vary away from the galactic centre. Moving on from here, we use ALMA to map NGC 1068. Observations of several molecules across the AGN and starburst regions are used to determine conditions and processes with a spatial resolution of less than 35 parsecs.

  17. Important Nearby Galaxies without Accurate Distances

    NASA Astrophysics Data System (ADS)

    McQuinn, Kristen

    2014-10-01

    The Spitzer Infrared Nearby Galaxies Survey (SINGS) and its offspring programs (e.g., THINGS, HERACLES, KINGFISH) have resulted in a fundamental change in our view of star formation and the ISM in galaxies, and together they represent the most complete multi-wavelength data set yet assembled for a large sample of nearby galaxies. These great investments of observing time have been dedicated to the goal of understanding the interstellar medium, the star formation process, and, more generally, galactic evolution at the present epoch. Nearby galaxies provide the basis for which we interpret the distant universe, and the SINGS sample represents the best studied nearby galaxies.Accurate distances are fundamental to interpreting observations of galaxies. Surprisingly, many of the SINGS spiral galaxies have numerous distance estimates resulting in confusion. We can rectify this situation for 8 of the SINGS spiral galaxies within 10 Mpc at a very low cost through measurements of the tip of the red giant branch. The proposed observations will provide an accuracy of better than 0.1 in distance modulus. Our sample includes such well known galaxies as M51 (the Whirlpool), M63 (the Sunflower), M104 (the Sombrero), and M74 (the archetypal grand design spiral).We are also proposing coordinated parallel WFC3 UV observations of the central regions of the galaxies, rich with high-mass UV-bright stars. As a secondary science goal we will compare the resolved UV stellar populations with integrated UV emission measurements used in calibrating star formation rates. Our observations will complement the growing HST UV atlas of high resolution images of nearby galaxies.

  18. ACA [CI] observations of the starburst galaxy NGC 253

    NASA Astrophysics Data System (ADS)

    Krips, M.; Martín, S.; Sakamoto, K.; Aalto, S.; Bisbas, T. G.; Bolatto, A. D.; Downes, D.; Eckart, A.; Feruglio, Ch.; García-Burillo, S.; Geach, J.; Greve, T. R.; König, S.; Matsushita, S.; Neri, R.; Offner, S.; Peck, A. B.; Viti, S.; Wagg, J.

    2016-07-01

    Context. Carbon monoxide (CO) is widely used as a tracer of the molecular gas in almost all types of environments. However, several shortcomings of CO complicate usaging it as H2 tracer, such as its optical depth effects, the dependence of its abundance on metallicity, or its susceptibility to dissociation in highly irradiated regions. Neutral carbon emission has been proposed to overcome some of these shortcomings and hence to help revealing the limits of CO as a measure of the molecular gas. Aims: We aim to study the general characteristics of the spatially and spectrally resolved carbon line emission in a variety of extragalactic sources and evaluate its potential as complementary H2 tracer to CO. Methods: We used the Atacama Compact Array to map the [CI](3P1-3P0) line emission in the nearby starburst galaxy NGC 253 at unprecedented angular resolution (~3''). This is the first well-resolved interferometric [CI] map of an extragalactic source. Results: We have detected the [CI] line emission at high significance levels along the central disk of NGC 253 and its edges where expanding shells have previously been found in CO. Globally, the distribution of the [CI] line emission strongly resembles that of CO, confirming the results of previous Galactic surveys that [CI] traces the same molecular gas as CO. However, we also identify a significant increase of [CI] line emission with respect to CO in (some of) the outflow or shocked regions of NGC 253, namely the bipolar outflow emerging from the nucleus. A first-order estimate of the [CI] column densities indicates abundances of [CI] that are very similar to the abundance of CO in NGC 253. Interestingly, we find that the [CI] line is marginally optically thick within the disk. Conclusions: The enhancement of the [CI]/CO line ratios (~0.4-0.6) with respect to Galactic values (≤0.1), especially in the shocked regions of NGC 253, clearly indicates that mechanical perturbation such as shocks and the strong radiation

  19. New Constraints on the Escape of Ionizing Photons from Starburst Galaxies Using Ionization-parameter Mapping

    NASA Astrophysics Data System (ADS)

    Zastrow, Jordan; Oey, M. S.; Veilleux, Sylvain; McDonald, Michael

    2013-12-01

    The fate of ionizing radiation in starburst galaxies is key to understanding cosmic reionization. However, the galactic parameters on which the escape fraction of ionizing radiation depend are not well understood. Ionization-parameter mapping provides a simple, yet effective, way to study the radiative transfer in starburst galaxies. We obtain emission-line ratio maps of [S III]/[S II] for six, nearby, dwarf starbursts: NGC 178, NGC 1482, NGC 1705, NGC 3125, NGC 7126, and He 2-10. The narrowband images are obtained with the Maryland-Magellan Tunable Filter at Las Campanas Observatory. Using these data, we previously reported the discovery of an optically thin ionization cone in NGC 5253, and here we also discover a similar ionization cone in NGC 3125. This latter cone has an opening angle of 40° ± 5° (0.4 sr), indicating that the passageways through which ionizing radiation may travel correspond to a small solid angle. Additionally, there are three sample galaxies that have winds and/or superbubble activity, which should be conducive to escaping radiation, yet they are optically thick. These results support the scenario that an orientation bias limits our ability to directly detect escaping Lyman continuum in many starburst galaxies. A comparison of the star formation properties and histories of the optically thin and thick galaxies is consistent with the model that high escape fractions are limited to galaxies that are old enough (gsim3 Myr) for mechanical feedback to have cleared optically thin passageways in the interstellar medium, but young enough (lsim5 Myr) that the ionizing stars are still present.

  20. New constraints on the escape of ionizing photons from starburst galaxies using ionization-parameter mapping

    SciTech Connect

    Zastrow, Jordan; Oey, M. S.; Veilleux, Sylvain; McDonald, Michael

    2013-12-10

    The fate of ionizing radiation in starburst galaxies is key to understanding cosmic reionization. However, the galactic parameters on which the escape fraction of ionizing radiation depend are not well understood. Ionization-parameter mapping provides a simple, yet effective, way to study the radiative transfer in starburst galaxies. We obtain emission-line ratio maps of [S III]/[S II] for six, nearby, dwarf starbursts: NGC 178, NGC 1482, NGC 1705, NGC 3125, NGC 7126, and He 2-10. The narrowband images are obtained with the Maryland-Magellan Tunable Filter at Las Campanas Observatory. Using these data, we previously reported the discovery of an optically thin ionization cone in NGC 5253, and here we also discover a similar ionization cone in NGC 3125. This latter cone has an opening angle of 40° ± 5° (0.4 sr), indicating that the passageways through which ionizing radiation may travel correspond to a small solid angle. Additionally, there are three sample galaxies that have winds and/or superbubble activity, which should be conducive to escaping radiation, yet they are optically thick. These results support the scenario that an orientation bias limits our ability to directly detect escaping Lyman continuum in many starburst galaxies. A comparison of the star formation properties and histories of the optically thin and thick galaxies is consistent with the model that high escape fractions are limited to galaxies that are old enough (≳3 Myr) for mechanical feedback to have cleared optically thin passageways in the interstellar medium, but young enough (≲5 Myr) that the ionizing stars are still present.

  1. Spectroscopic Observations of the Star Formation Regions in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Kong, X.; Lin, L.; Li, J. R.; Zhou, X.; Zou, H.; Li, H. Y.; Chen, F. Z.; Du, W.; Fan, Z.; Mao, Y. W.; Wang, J.; Zhu, Y. N.; Zhou, Z. M.

    2014-01-01

    During the late 1990s and the first decade of the 21st century, the 8˜10 m scale ground-based telescopes are helping astronomers learn much more about how galaxies develop. The existing 2˜4 m scale telescopes become less important for astrophysical researches. To use the existing 2˜4 m scale telescopes to address important issues in cosmology and extragalactic and galactic astronomy, we have to consider very carefully which kind of things we can do, and which we can not. For this reason, the Time Allocation Committee (TAC) of the National Astronomical Observatories of China (NAOC) 2.16 m telescope decides to support some key projects since 2013. Nearby galaxies supply us with the opportunity to study galaxy dynamics and star formation on large scales, yet are close enough to reveal the details. Star formation regions in nearby galaxies provide an excellent laboratory to study the star formation processes, the evolution of massive stars, and the properties of the surrounding interstellar medium. A wealth of information can be obtained from the spectral analysis of the bright emission lines and the stellar continuum. Considering these, we proposed a long-term project ``Spectroscopic Observations of the Star Formation Regions in Nearby Galaxies'', and it becomes the key project of the NAOC 2.16 m telescope since 2013, supported with 30 dark/grey nights per year. The primary goal of this project is to observe the spectroscopy of star formation regions in 20 nearby galaxies, with the NAOC 2.16 m telescope and the Hectospec/MMT (Multiple Mirror Telescope) multifiber spectrograph by Telescope Access Program (TAP). With the spectra of a large sample of star formation regions, combining multi-wavelength data from UV to IR, we can investigate, understand, and quantify the nature of the deviation from the starbursts' IRX-β (the IR/UV ratio ``IRX'' versus the UV color ``β'') correlation. It will be important for a better understanding of the interaction of dust and

  2. Reconstruction of SDSS Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Kushner, Laura K.; Obric, M.; West, A. A.; Dalcanton, J.

    2006-12-01

    We present The SDSS Multiple Offspring Recombination Engine (SMORE), a newly developed code that automatically and interactively recombines galaxies fragmented by the Sloan Digital Sky Survey (SDSS) Photo pipeline. The SDSS software was optimized for the faint-end of the brightness limit and tends to over-deblend galaxies with angular sizes over 2 arcmin, sometimes separating spiral arms and HII regions from their parent galaxies. This process can remove a large percentage of the flux from the galaxy and bias datasets due to incorrect photometry. SMORE automatically builds galaxies from the fragments ("children"). Decisions on which child to include are made on the basis of its g-r and r-i color (relative to the mean colors of the largest galaxy children), size, distance to the center of the galaxy, type (as assigned by SDSS Photo) and the position angle. If there are pieces for which a decision cannot be made and their relative flux is more than 5% of the total flux of the galaxy, the interactive SMORE gives a user option to manually choose which of those children should be included. Recombined galaxies are built on a clean background without foreground and background objects and new photometry is performed.

  3. Normal and Starburst Galaxies in Deep X-ray Surveys

    NASA Technical Reports Server (NTRS)

    Hornschemeier, Ann

    2006-01-01

    This talk will cover progress of the last several years in unraveling the nature of normal and starburst galaxies in deep X-ray surveys. This includes discussion of the normal galaxy X-ray Luminosity Function in deep field and cluster surveys and what it tells us about the binary populations in galaxies. The utility of broad band X-ray emission, especially as compared to other multiwavelength measurements of current/recent star formation, will be reviewed. These broad band X-ray measurements of star formation are based upon X-ray/Star Formation Rate correlations that span the currently available redshift range (0 < z < 1). I will also discuss new efforts underway to systematically characterize the X-ray emission from galaxies in group and cluster environments, including a new effort underway in the Coma cluster of galaxies. I will finish with discussion of the redshift frontier for studies of X-ray star formation, currently 2 approx.4, where the UV-selected Lyman Break galaxies are the best glimpse we have into X-ray emission from star formation in the early Universe. Lyman Break galaxies are of particular interest due to the overlap in basic properties with starburst galaxies in the more local Universe. Understanding the outflows in such starburst galaxies is of critical importance to constraining the "stellar" portion of cosmic feedback. The talk will close with a brief discussion of distant normal galaxy science with future X-ray observatories such as the upcoming Con-X/XEUS mission(s).

  4. The ultraviolet spectra of nearby radio galaxies

    NASA Technical Reports Server (NTRS)

    Keel, William C.; Windhorst, Rogier A.

    1991-01-01

    New and archival IUE SWP spectra are reported for nine nearby radio galaxies (V is less than 15 mag), together with optical emissionlike data for these galaxies as well as a number of candidates with weaker line emission. Both their UV line and continuum properties, as well as their UV and UV-optical line ratios, are examined. Ly-alpha emission is found to be common among local radio galaxies, at modest luminosities (typically 10 exp 41-42 erg/s). No apparent relation is found between L(Ly-alpha) and radio power for the nearby radio galaxies alone. The Ly-alpha/H-alpha ratio in low power nearby radio galaxies is 2-5 times lower than the prediction for case B recombination. The destruction of Ly-alpha photons by grains during resonant scattering can explain the observed deficiency for reasonable metallicities. The nearby radio galaxies have in general a small C IV/Ly-alpha ratio (less than 0.1). Comparison of the C IV and Ly-alpha strengths with those in luminous AGN suggests that most of the UV continuum comes from the stellar population, and not from the AGN.

  5. The role of massive stars in young starburst galaxies

    NASA Astrophysics Data System (ADS)

    Norris, Richard Paul Furber

    Starburst galaxies are defined as those galaxies undergoing violent star formation over relatively short periods of time (10 to 100 Myr). These objects may form stellar populations of > 106 Msun, containing massive stars with masses > 100 Msun. Although most starburst galaxies are observed at relatively low redshift, recent evidence suggests that these types of galaxies were far more important in the high redshift past. It is believed that the chemical evolution of the Universe has been strongly influenced by this mode of star formation through the dense winds from massive stars and supernovae ejecta. Our understanding of starbursts is still relatively poor, since most are too distant to be resolved. We can gain some understanding of starbursts indirectly through the modelling of associated nebulae via the calculation of theoretical spectral energy distributions (SEDs) and photoionization modelling. This technique heavily relies upon the accuracy of the predicted far UV continuum of the massive star population. This thesis presents a new grid of SEDs for O stars, early B supergiants and Wolf-Rayet stars which have been incorporated into the evolutionary synthesis code Starburst99 (Leitherer et al. 1999). A total of 285 expanding, non-LTE, line-blanketed model atmospheres have been calculated to replace old, inaccurate LTE models for O stars, and pure helium, unblanketed models for W-R stars. These new grids cover five metallicities and the wind parameters are scaled with metallicity. We find that the new models yield significantly less ionizing flux below the He 0 ionizing edge at early phases and as a consequence, nebular He II lambda4686 will not be observable in young starbursts. We use the photoionization code CLOUDY to test the accuracy of the predicted ionizing fluxes from our new models. We find that they are in much better agreement with observed optical and IR nebular line diagnostics than any previous models. The new W-R atmospheres are used in

  6. Diffuse Gamma-Ray Emission from the Starburst Galaxy NGC 253

    NASA Technical Reports Server (NTRS)

    Bertsch, David L.; Paglione, Timothy A. D.; Marscher, Alan P.; Jackson, James M.

    1995-01-01

    The starburst galaxy NGC 253 was observed with the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory (CGRO) satellite. We obtain a 2 sigma upper limit to the gamma-ray emission above 100 MeV of 8 x 10(exp -8) photons/sq cm/s. Because of their large gas column densities and supernova rates, nearby starburst galaxies were predicted to have gamma-ray fluxes detectable by EGRET. Our nondetection of gamma-rays from NGC 253 motivates us to reexamine in detail the premise of supernova acceleration of cosmic rays and the effect of enhanced cloud densities, photon densities, and magnetic fields on the high-energy spectra of galaxies. By modeling the expected gamma-ray and synchrotron spectra from NGC 253, we find that up to 20% of the energy from supernovae is transferred to cosmic rays in the starburst, which is consistent with supernova acceleration models. Our calculations match the EGRET and radio data well with a supernova rate of 0.08/yr, a magnetic field B greater than or approximately equal to 5 x 10(exp -5) G, a density n approximately 300/cu cm, a photon density U(sub ph) approximately 200 eV/cu cm, and an escape timescale tau(sub o) less than or approximately equal to 10 Myr.

  7. Integrated Optical Polarization of nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Jones, Amy; Wang, Lifan; Krisciunas, Kevin; Freeland, Emily

    2012-03-01

    We performed an integrated optical polarization survey of 70 nearby galaxies to study the relationship between linear polarization and galaxy properties. To date this is the largest survey of its kind. The data were collected at McDonald Observatory using the Imaging Grism Polarimeter on the Otto Struve 2.1 m telescope. Most of the galaxies did not have significant level of linear polarization, where the bulk is <1%. A fraction of the galaxies showed a loose correlation between the polarization and position angle of the galaxy, indicating that dust scattering is the main source of optical polarization. The unbarred spiral galaxies are consistent with the predicted relationship with inclination from scattering models of ~sin 2 i.

  8. INTEGRATED OPTICAL POLARIZATION OF NEARBY GALAXIES

    SciTech Connect

    Jones, Amy; Wang Lifan; Krisciunas, Kevin; Freeland, Emily

    2012-03-20

    We performed an integrated optical polarization survey of 70 nearby galaxies to study the relationship between linear polarization and galaxy properties. To date this is the largest survey of its kind. The data were collected at McDonald Observatory using the Imaging Grism Polarimeter on the Otto Struve 2.1 m telescope. Most of the galaxies did not have significant level of linear polarization, where the bulk is <1%. A fraction of the galaxies showed a loose correlation between the polarization and position angle of the galaxy, indicating that dust scattering is the main source of optical polarization. The unbarred spiral galaxies are consistent with the predicted relationship with inclination from scattering models of {approx}sin{sup 2} i.

  9. Hard Gamma Ray Emission from the Starburst Galaxy NGC 253

    NASA Technical Reports Server (NTRS)

    Jackson, James M.; Marscher, Alan M.

    1996-01-01

    We have completed the study to search for hard gamma ray emission from the starburst galaxy NGC 253. Since supernovae are thought to provide the hard gamma ray emission from the Milky Way, starburst galaxies, with their extraordinarily high supernova rates, are prime targets to search for hard gamma ray emission. We conducted a careful search for hard gamma ray emission from NGC 253 using the archival data from the EGRET experiment aboard the CGRO. Because this starburst galaxy happens to lie near the South Galactic Pole, the Galactic gamma ray background is minimal. We found no significant hard gamma ray signal toward NGC 253, although a marginal signal of about 1.5 sigma was found. Because of the low Galactic background, we obtained a very sensitive upper limit to the emission of greater than 100 MeV gamma-rays of 8 x 10(exp -8) photons/sq cm s. Since we expected to detect hard gamma ray emission, we investigated the theory of gamma ray production in a dense molecular medium. We used a leaky-box model to simulate diffusive transport in a starburst region. Since starburst galaxies have high infrared radiation fields, we included the effects of self-Compton scattering, which are usually ignored. By modelling the expected gamma-ray and synchrotron spectra from NGC 253, we find that roughly 5 - 15% of the energy from supernovae is transferred to cosmic rays in the starburst. This result is consistent with supernova acceleration models, and is somewhat larger than the value derived for the Galaxy (3 - 10%). Our calculations match the EGRET and radio data very well with a supernova rate of 0.08/ yr, a magnetic field B approx. greater than 5 x 10(exp -5) G, a density n approx. less than 100/sq cm, a photon density U(sub ph) approx. 200 eV/sq cm, and an escape time scale tau(sub 0) approx. less than 10 Myr. The models also suggest that NGC 253 should be detectable with only a factor of 2 - 3 improvement in sensitivity. Our results are consistent with the standard picture

  10. Gamma-rays from pulsar wind nebulae in starburst galaxies

    NASA Astrophysics Data System (ADS)

    Mannheim, Karl; Elsässer, Dominik; Tibolla, Omar

    2012-07-01

    Recently, gamma-ray emission at TeV energies has been detected from the starburst galaxies NGC253 (Acero et al., 2009) [1] and M82 (Acciari et al., 2009) [2]. It has been claimed that pion production due to cosmic rays accelerated in supernova remnants interacting with the interstellar gas is responsible for the observed gamma rays. Here, we show that the gamma-ray pulsar wind nebulae left behind by the supernovae contribute to the TeV luminosity in a major way. A single pulsar wind nebula produces about ten times the total luminosity of the Sun at energies above 1 TeV during a lifetime of 105 years. A large number of 3 × 104 pulsar wind nebulae expected in a typical starburst galaxy at a distance of 4 Mpc can readily produce the observed TeV gamma rays.

  11. Properties of satellite galaxies in nearby groups

    NASA Astrophysics Data System (ADS)

    Vennik, Jaan

    2016-10-01

    We studied the variation of stellar mass and various star-formation characteristics of satellite galaxies in a volume limited sample of nearby groups as a function of their group-centric distance and of their relative line-of-sight velocity in the group rest frame. We found clear radial dependencies, e.g. massive, red and passive satellites being distributed predominantly near the center of composite group. We also found some evidence of velocity modulation of star-forming properties of satellite galaxies near the group virial radius. We conclude that using kinematical data, it should be feasible to separate dynamical classes of bound, in-falling and 'backsplash' satellite galaxies.

  12. Chandra Images the Seething Cauldron of Starburst Galaxy

    NASA Astrophysics Data System (ADS)

    2000-01-01

    NASA's Chandra X-ray Observatory has imaged the core of the nearest starburst galaxy, Messier 82 (M82). The observatory has revealed a seething cauldron of exploding stars, neutron stars, black holes, 100 million degree gas, and a powerful galactic wind. The discovery will be presented by a team of scientists from Carnegie Mellon University, Pittsburgh, Penn., Pennsylvania State University, University Park, and the University of Michigan, Ann Arbor, on January 14 at the 195th national meeting of the American Astronomical Society. "In the disk of our Milky Way Galaxy, stars form and die in a relatively calm fashion like burning embers in a campfire," said Richard Griffiths, Professor of Astrophysics at Carnegie Mellon University. "But in a starburst galaxy, star birth and death are more like explosions in a fireworks factory." Short-lived massive stars in a starburst galaxy produce supernova explosions, which heat the interstellar gas to millions of degrees, and leave behind neutron stars and black holes. These explosions emit light in the X rays rather than in visible light. Because the superhot components inside starburst galaxies are complex and sometimes confusing, astronomers need an X-ray-detecting telescope with the highest focusing power (spatial resolution) to clearly discriminate the various structures. "NASA's Chandra X-ray Observatory is the perfect tool for studying starburst galaxies since it has the critical combination of high-resolution optics and good sensitivity to penetrating X rays," said Gordon Garmire, the Evan Pugh Professor of Astronomy and Astrophysics at Pennsylvania State University, and head of the team that conceived and built Chandra's Advanced CCD Imaging Spectrograph (ACIS) X-ray camera, which acquired the data. Many intricate structures missed by earlier satellite observatories are now visible in the ACIS image, including more than twenty powerful X-ray binary systems that contain a normal star in a close orbit around a neutron star

  13. PHOTODISSOCIATION CHEMISTRY FOOTPRINTS IN THE STARBURST GALAXY NGC 253

    SciTech Connect

    MartIn, Sergio; MartIn-Pintado, J.; Viti, S.

    2009-12-01

    UV radiation from massive stars is thought to be the dominant heating mechanism of the nuclear interstellar medium (ISM) in the late stages of evolution of starburst galaxies, creating large photodissociation regions (PDRs) and driving a very specific chemistry. We report the first detection of PDR molecular tracers, namely HOC{sup +} and CO{sup +}, and also confirm the detection of the PDR tracer HCO toward the starburst galaxy NGC 253, claimed to be mainly dominated by shock heating and in an earlier stage of evolution than M 82, the prototypical extragalactic PDR. Our CO{sup +} detection suffers from significant blending to a group of transitions of {sup 13}CH{sub 3}OH, tentatively detected for the first time in the extragalactic ISM. These species are efficiently formed in the highly UV-irradiated outer layers of molecular clouds, as observed in the late stage nuclear starburst in M 82. The molecular abundance ratios we derive for these molecules are very similar to those found in M 82. This strongly supports the idea that these molecules are tracing the PDR component associated with the starburst in the nuclear region of NGC 253. The presence of large abundances of PDR molecules in the ISM of NGC 253, which is dominated by shock chemistry, clearly illustrates the potential of chemical complexity studies to establish the evolutionary state of starbursts in galaxies. A comparison with the predictions of chemical models for PDRs shows that the observed molecular ratios are tracing the outer layers of UV-illuminated clouds up to two magnitudes of visual extinction. We combine the column densities of PDR tracers reported in this paper with those of easily photodissociated species, such as HNCO, to derive the fraction of material in the well-shielded core relative to the UV-pervaded envelopes. Chemical models, which include grain formation and photodissociation of HNCO, support the scenario of a photo-dominated chemistry as an explanation to the abundances of the

  14. Orbital masses of nearby luminous galaxies

    SciTech Connect

    Karachentsev, Igor D.; Kudrya, Yuri N. E-mail: yukudrya@gmail.com

    2014-09-01

    We use observational properties of galaxies accumulated in the Updated Nearby Galaxy Catalog to derive a dark matter mass of luminous galaxies via motions of their companions. The data on orbital-to-stellar mass ratio are presented for 15 luminous galaxies situated within 11 Mpc from us: the Milky Way, M31, M81, NGC 5128, IC342, NGC 253, NGC 4736, NGC 5236, NGC 6946, M101, NGC 4258, NGC 4594, NGC 3115, NGC 3627, and NGC 3368, as well as for a composite suite around other nearby galaxies of moderate and low luminosity. The typical ratio for these galaxies is M {sub orb}/M {sub *} = 31, corresponding to the mean local density of matter Ω {sub m} = 0.09, i.e., one-third of the global cosmic density. This quantity seems to be rather an upper limit of dark matter density, since the peripheric population of the suites may suffer from the presence of fictitious unbound members. We note that the Milky Way and M31 halos have lower dimensions and lower stellar masses than those of the other 13 nearby luminous galaxies. However, the dark-to-stellar mass ratio for both the Milky Way and M31 is typical for other neighboring luminous galaxies. The distortion in the Hubble flow, observed around the Local Group and five other neighboring groups, yields their total masses within the radius of a zero velocity surface, R {sub 0}; these masses are slightly lower than the orbital and virial values. This difference may be due to the effect of dark energy producing a kind of 'mass defect' within R {sub 0}.

  15. Suites of dwarfs around Nearby giant galaxies

    SciTech Connect

    Karachentsev, Igor D.; Kaisina, Elena I.; Makarov, Dmitry I. E-mail: kei@sao.ru

    2014-01-01

    The Updated Nearby Galaxy Catalog (UNGC) contains the most comprehensive summary of distances, radial velocities, and luminosities for 800 galaxies located within 11 Mpc from us. The high density of observables in the UNGC makes this sample indispensable for checking results of N-body simulations of cosmic structures on a ∼1 Mpc scale. The environment of each galaxy in the UNGC was characterized by a tidal index Θ{sub 1}, depending on the separation and mass of the galaxy's main disturber (MD). We grouped UNGC galaxies with a common MD in suites, and ranked suite members according to their Θ{sub 1}. All suite members with positive Θ{sub 1} are assumed to be physical companions of the MD. About 58% of the sample are members of physical groups. The distribution of suites by the number of members, n, follows a relation N(n) ∼ n {sup –2}. The 20 most populated suites contain 468 galaxies, i.e., 59% of the UNGC sample. The fraction of MDs among the brightest galaxies is almost 100% and drops to 50% at M{sub B} = –18{sup m}. We discuss various properties of MDs, as well as galaxies belonging to their suites. The suite abundance practically does not depend on the morphological type, linear diameter, or hydrogen mass of the MD, the tightest correlation being with the MD dynamical mass. Dwarf galaxies around MDs exhibit well-known segregation effects: the population of the outskirts has later morphological types, richer H I contents, and higher rates of star formation activity. Nevertheless, there are some intriguing cases where dwarf spheroidal galaxies occur at the far periphery of the suites, as well as some late-type dwarfs residing close to MDs. Comparing simulation results with galaxy groups, most studies assume the Local Group is fairly typical. However, we recognize that the nearby groups significantly differ from each other and there is considerable variation in their properties. The suites of companions around the Milky Way and M31, consisting of the

  16. Starbursts in blue compact dwarf galaxies

    NASA Technical Reports Server (NTRS)

    Thuan, Trinh Xuan

    1987-01-01

    All the arguments for a bursting mode of star formation in blue compact dwarf galaxies (BCD) are summarized. It is shown that spectral synthesis of far-ultraviolet spectra of BCDs constitutes a powerful way to study the star formation history in these galaxies. BCD luminosity functions show jumps and discontinuities. These jumps act like fossil records of the star-forming bursts, aiding in the counting and dating of the bursts.

  17. Searching for GRB Remnants in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Bhargavi, S. G.; Rhoads, J.; Perna, R.; Feldmeier, J.; Greiner, J.

    2004-09-01

    Gamma Ray Bursts (GRBs) are expected to leave behind GRB remnants, similar to how ``standard'' supernovae (SN) leave behind SN remnants. The identification of these remnants in our own and in nearby galaxies would allow a much closer look at GRB birth sites, and possibly lead to the discovery of the compact object left behind. It would also provide independent constraints on GRB rates and energetics. We have initiated an observational program (2002) to search for GRB remnants in nearby galaxies. The identification is based on specific line ratios, such as OIII/Hβ and HeII/Hβ. which are expected to be unusually high in case of GRB remnants according to the theoretical predictions of Perna et al. (2000). The observing strategies and preliminary studies from a test run at 2.34 m VBT as well as archival data from planetary nebulae surveys of spiral galaxies are discussed.

  18. Circumnuclear ring of the starburst galaxy NGC 253. An Infrared view

    NASA Astrophysics Data System (ADS)

    Pérez GarcÍa, A. M.; Melo, V. P.; Acosta-Pulido, J.; Muñoz-Tuñón, C.; RodrÍguez-Espinosa, J. M.

    NGC 253 is a nearby spiral galaxy with an active starburst nucleus. Its proximity allows observation with good spatial resolution with state of the art mid and far IR facilities. Here we present preliminary results obtained from the ISO archive in 5 to 16 microns (ISOCAM-CVF) and 120 to 180 μm (ISOPHOT) ranges. The mid IR spectrum exhibits typical broad PAH features as well as weak atomic emission, which is not seen in the continuum nor in the [ArII] emission line. For the first time we present a far IR map (180 μm) as well as several profiles across the minor axis of the galaxy, showing a variation of the dust temperature. We detect an extension of the cold dust (20K) emission not seen previously in IRAS maps, which may contribute to a large fraction of the galaxy total mass.

  19. Gas distribution and starbursts in shell galaxies

    NASA Technical Reports Server (NTRS)

    Weil, Melinda L.; Hernquist, Lars

    1993-01-01

    Detailed maps of most elliptical galaxies reveal that, whereas the greatest part of their luminous mass originates from a smooth distribution with a surface brightness approximated by a de Vaucouleurs law, a small percentage of their light is contributed by low surface brightness distortions termed 'fine structures'. The sharp-edged features called 'shells' are successfully reproduced by merger and infall models involving accretion from less massive companions. In this context, dwarf spheroidal and compact disk galaxies are likely progenitors of these stellar phenomena. However, it is probable that the sources of shell-forming material also contain significant amounts of gas. This component may play an important role in constraining the formation and evolution of shell galaxies. To investigate the effects of the gaseous component, numerical simulations were performed to study the tidal disruption of dwarf galaxies containing both gas and stars by more massive primaries, and the evolution of the ensuing debris. The calculations were performed with a hybrid N-body/hydrodynamics code. Collisionless matter is evolved using a conventional N-body technique and gas is treated using smoothed particle hydrodynamics in which self-gravitating fluid elements are represented as particles evolving according to Lagrangian hydrodynamic equations. An isothermal equation of state is employed so the gas remains at a temperature 104 K. Owing to the large mass ratio between the primary and companion, the primary is modeled as a rigid potential and the self-gravity of both galaxies is neglected.

  20. Super Star Cluster Nebula in the Starburst Galaxy NGC 660

    NASA Astrophysics Data System (ADS)

    Naiman, J. P.; Turner, J. L.; Tsai, C.-W.; Beck, S. C.; Ho, P. T. P.

    2004-12-01

    We have mapped the starburst galaxy NGC 660 at 100mas resolution at K band (1.3 cm) with the NRAO Very Large Array. A peculiar galaxy at a distance of 13 Mpc, NGC 660 contains concentrated central star formation of power ˜ 2 x 1010 Lsun. Our 1.3 cm continuum image reveals a bright, compact source of less than 10 pc extent with a rising spectral index. We infer that this is optically thick free-free emission from a super star cluster nebula. The nebula is less than 10 pc in size, comparable in luminosity to the ``supernebula" in the dwarf galaxy, NGC 5253. We estimate that there are a few thousand O stars contained in this single young cluster. There are a number of other weaker continuum sources, either slightly smaller or more evolved clusters of similar size within the central 300 parsecs of the galaxy. This work is supported in part by the National Science Foundation.

  1. Radio identifications of UGC galaxies - starbursts and monsters

    SciTech Connect

    Condon, J.J.; Broderick, J.J.

    1988-07-01

    New and previously published observational data on galaxies with declination less than +82 deg from the Uppsala General Catalog (Nilson, 1973) are compiled in extensive tables and characterized in detail. Optical positions are confirmed by measurement of Palomar Sky Survey O prints, and radio identifications for 176 galaxies are made on the basis of 1.4-GHz Green Bank sky maps or 1.49-GHz observations obtained with the C configuration of the VLA in November-December 1986; contour maps based on the latter observations are provided. Radio-selected and IR-selected galaxy populations are found to be similar (and distinct from optically selected populations), and three radio/IR criteria are developed to distinguish galaxies powered by starbursts from those with supermassive black holes or other monster energy sources. 197 references.

  2. Chemical Pollution and Evolution of Massive Starbursts: Cleaning up the Environment in Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Kobulnicky, C.

    1996-12-01

    I present the results of a research program seeking to characterize the impact of massive star-clusters on the chemical and dynamical evolution of metal-poor, irregular and blue compact galaxies. The evolution of high mass stars is thought to contribute the bulk of heavy element enrichment in the interstellar medium, especially alpha -process elements like O, Si, etc. Yet, in actively star-forming galaxies, localized chemical inhomogeneities are seldom observed. Spatially-resolved optical and ultraviolet spectroscopy from the Hubble Space Telescope and ground-based observatories is used to search for chemical enrichment in the vicinity of young star clusters in nearby galaxies. VLA aperture synthesis maps are used to examine the neutral hydrogen content, dynamics, and local environment of the sample galaxies. Despite the spread in evolutionary state of the starbursts determined by the EW of Balmer emission lines and the radio continuum spectral index, few instances of localized enrichment are found. In light of these data, the ``instantaneous enrichment'' scenario for extragalactic HII regions appears less probable than one which operates on long timescales and global spatial scales. The results are consistent with the idea that starburst driven winds expel freshly synthesized metals in a hot 10(6) K phase into the halos of galaxies where they cool, condense into globules, and mix homogeneously with the rest of the galaxy on long (dynamical) timescales. The C/O and N/O ratios of the galaxies are used as new tools for measuring the recent star formation history. Implications for chemical evolution of galaxies both locally and cosmologically are developed.

  3. The infrared supernova rate in starburst galaxies

    NASA Astrophysics Data System (ADS)

    Mannucci, F.; Maiolino, R.; Cresci, G.; Della Valle, M.; Vanzi, L.; Ghinassi, F.; Ivanov, V. D.; Nagar, N. M.; Alonso-Herrero, A.

    2003-04-01

    We report the results of our ongoing search for extincted supernovae (SNe) at near-infrared wavelengths. We have monitored at 2.2 mu m a sample of 46 Luminous Infrared Galaxies and detected 4 SNe. The number of detections is still small but sufficient to provide the first estimate of supernova rate at near-infrared wavelengths. We measure a SN rate of SNNIR_r=7.6+/- 3.8 SNu which is an order of magnitude larger than observed in quiescent galaxies. On the other hand, the observed near-infrared rate is still a factor 3-10 smaller than that estimated from the far-infrared luminosity of the galaxies. Among various possibilities, the most likely scenario is that dust extinction is so high (AV>30) to obscure most SNe even in the near-IR. The role of type Ia SNe is also discussed within this context. We derive the type Ia SN rate as a function of the stellar mass of the galaxy and find a sharp increase toward galaxies with higher activity of star formation. This suggests that a significant fraction of type Ia SNe are associated with young stellar populations. Finally, as a by-product, we give the average K-band light curve of core-collapse SNe based on all the existing data, and review the relation between SN rate and far-infrared luminosity. Based on observations collected at the European Southern Observatory, Chile (proposal 66.B-0417), at the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Centro Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica), and at the Steward Observatory 61'' telescope.

  4. Kinematics and Structure of the Starburst Galaxy NGC 7673

    NASA Astrophysics Data System (ADS)

    Homeier, N. L.; Gallagher, J. S.

    1999-09-01

    The morphology and kinematics of the luminous blue starburst galaxy NGC 7673 are explored using the WIYN (Wisconsin-Indiana-Yale-NOAO) 3.5 m telescope. Signs of a past kinematic disturbance are detected in the outer galaxy; the most notable feature is a luminous ripple located 1.55 arcmin from the center of NGC 7673. Subarcsecond imaging in B and R filters also reveals red dust lanes and blue star clusters that delineate spiral arms in the bright inner disk, and narrowband Hα imaging shows that the luminous star clusters are associated with giant H II regions. The Hα kinematics measured with echelle imaging spectroscopy using the WIYN DensePak fiber array imply that these H II regions are confined to a smoothly rotating disk. The velocity dispersion in ionized gas in the disk is σ~24 km s-1, which sets an upper boundary on the dispersion of young stellar populations. Broad emission components with σ~63 km s-1 found in some regions are likely produced by mechanical power supplied by massive, young stars; a violent starburst is occurring in a kinematically calm disk. Although the asymmetric outer features point to a merger or interaction as the starburst trigger, the inner disk structure constrains the strength of the event to the scale of a minor merger or weak interaction that occurred at least an outer disk dynamical timescale in the past.

  5. Starburst Galaxies: Hard X-ray spectra and contribution to the diffuse background

    NASA Technical Reports Server (NTRS)

    Gruber, Duane E.

    1993-01-01

    During the period of this grant two main tasks were performed: a determination of a selection criterion for starburst galaxies most likely to emit X-rays, and performance of a pilot study of the X-ray emission from nine such systems. Starburst galaxies may be expected to emit flat-spectrum X-ray at energies above 10 keV resulting from the various remnants of the short-lived massive stars which characterize the starburst. The investigation to determine the optimum sample resulted in a change from an X-ray selected (HEAO-2) sample to infrared selection based on the IRAS catalogue. A much broader sample thereby available for study, and selection could be limited to only the nearest objects and still obtain a reasonably large sample. A sample of 99 of the brightest infrared starburst galaxies was settled on for the X-ray survey. For a set of practical size, this was then reduced to a subset of 53, based on luminosity and nearness. X-ray emission from these objects was individually measured from the UCSD HEAO-1 all-sky survey in four energy bands between 13 keV to 160 keV. This data base consists of about 20 optical disk volumes. Net significance for the result was roughly two sigma, and a very hard spectral shape is indicated for the net spectrum of the surveyed galaxies. With the possibility of detection of the class, it was then felt worthwhile to examine fluxes from these sources in other archival data. This was performed with the HEAO-1 A2 data and the HEAO-2 (EINSTEIN) main archive and slew survey. Positive results were also obtained for the sample, but again at weak significance. With three independent measures of weak X-ray fluxes from nearby starburst galaxies, we wrote a letter to the Astrophysical Journal (enclosed) discussing these results and their likely significance, in particular, for the contribution to the cosmic diffuse x-ray background, perhaps as much as 25 percent.

  6. Ultraviolet imaging of the AGN+starburst galaxy NGC 1068

    NASA Technical Reports Server (NTRS)

    Neff, Susan G.; Fanelli, Michael N.; Roberts, Laura J.; O'Connell, Robert W.; Bohlin, Ralph; Roberts, Morton S.; Smith, Andrew M.; Stecher, Theodore P.

    1994-01-01

    Images of the Seyfert 2 galaxy NGC 1068 were obtained at two ultraviolet wavelengths by the Ultraviolet Imaging Telescope (UIT). These data represent the first detailed UV imagery of a composite (active galactic nucleus + starburst) disk galaxy. NGC 1068 cotains multiple components at UV wavelengths: the central active galactic nucleus; a population of very luminous starburst knots; a bright oval inner disk; and a fainter, more circular halo. The most luminous knot, which is located approximately 750 pc from the nucleus at PA 315 deg, is approximately 80 times the luminosity of 30 Doradus and gives NGC 1068 a 'double nucleus' appearance in the UV. Significant extended emission is observed throughout the disk, unlike other disk galaxies so far observed in the UV. The radial brightness profile in both UV bandpasses generally follows an exponential decline to approximately 5 kpc. A faint halo extending to approximately 13 kpc is likely to be a galaxian-sized reflection nebula where ambient dust scatters the intense UV continuum from the inner galaxy. UV colors show a striking asymmetric morphology, which is correlated with the observed molecular CO emission.

  7. ROSAT HRI Observations of the Starburst Galaxy M82

    NASA Astrophysics Data System (ADS)

    Schulman, E.; Bregman, J. N.

    1992-12-01

    Gas-dynamical models of starburst galaxies predict that supernova heating creates a bubble of hot gas which breaks out of the disk. Some models predict a polar outflow in which the hot gas escapes along an edge-brightened chimney-like structure, while others predict spherical galactic winds. In order to test these models we have obtained a 25 ksec ROSAT HRI image of the starburst galaxy M82. Our HRI image has a resolution of about 5''(70 pc) and a field of view of about 30' (20 kpc). The image includes photons with energies between 0.2 and 1.5 keV and is almost an order of magnitude more sensitive than previous images. The X-ray emission extends perpendicular to the disk 3-4 kpc which is comparable to the extent of the emission detected with the Einstein IPC, although our resolution is more than a factor of 10 better. The emission is neither collimated nor spherically distributed, but has a conical distribution in which the emission close to the center of the galaxy is more compact than the emission farther away from the disk. The X-ray emission is not edge-brightened and decreases in hardness with distance from the center of the galaxy. The mean energy in the core is about 0.85 keV, while the mean energy a few kpc from the disk is about 0.25 keV. The shape, temperature, and lack of edge-brightening of the emission is in conflict with some starburst models. ES wishes to acknowledge support from a NASA Graduate Student Research Program Fellowship.

  8. WINGS: WFIRST Infrared Nearby Galaxy Survey

    NASA Astrophysics Data System (ADS)

    Williams, Benjamin

    WFIRST's combination of wide field and high resolution will revolutionize the study of nearby galaxies. We propose to produce and analyze simulated WFIRST data of nearby galaxies and their halos to maximize the scientific yield in the limited observing time available, ensuring the legacy value of WFIRST's eventual archive. We will model both halo structure and resolved stellar populations to optimize WFIRST's constraints on both dark matter and galaxy formation models in the local universe. WFIRST can map galaxy structure down to ~35 mag/square arcsecond using individual stars. The resulting maps of stellar halos and accreting dwarf companions will provide stringent tests of galaxy formation and dark matter models on galactic (and even sub-galactic) scales, which is where the most theoretical tension exists with the Lambda-CDM model. With a careful, coordinated plan, WFIRST can be expected to improve current sample sizes by 2 orders of magnitude, down to surface brightness limits comparable to those currently reached only in the Local Group, and that are >4 magnitudes fainter than achievable from the ground due to limitations in star-galaxy separation. WFIRST's maps of galaxy halos will simultaneously produce photometry for billions of stars in the main bodies of galaxies within 10 Mpc. These data will transform studies of star formation histories that track stellar mass growth as a function of time and position within a galaxy. They also will constrain critical stellar evolution models of the near-infrared bright, rapidly evolving stars that can contribute significantly to the integrated light of galaxies in the near-infrared. Thus, with WFIRST we can derive the detailed evolution of individual galaxies, reconstruct the complete history of star formation in the nearby universe, and put crucial constraints on the theoretical models used to interpret near-infrared extragalactic observations. We propose a three-component work plan that will ensure these gains by

  9. A NICMOS search for obscured supernovae in starburst galaxies

    NASA Astrophysics Data System (ADS)

    Maiolino, Roberto

    2003-07-01

    Recent near-IR monitoring campaigns were successful in detecting obscured supernovae {SNe} in starburst galaxies. The inferred SN rate is much higher than that obtained in previous optical campaigns, but it is still significanly lower than expected by the high level star formation of these systems. One possible explanation for the shortage of SNe is that most of them occur in the nuclear region, where the limited angular resolution of groundbased observations prevents their detection. We propose NICMOS SNAP observations of a sample of starburst galaxies already observed once by NICMOS, with the goal of exploiting its sensitivity and angular resolution to detect nuclear obscured SNe which might have been missed by groundbased surveys. These observation will allow to assess the real SN rate in starbust galaxies and deliver a sample of SN occurring in the extreme environment of galactic nuclei. We expect to detect more than 55 SNe {if the whole sample is observed}. If the number of SNe detected in the program is much lower than expected it would prompt for a revision of our understanding of the relation between the star formation rate and the SN rate.

  10. A Multiwavelength Study of the Starburst Galaxy NGC 7771

    NASA Technical Reports Server (NTRS)

    Davies, Richard I.; Alonso-Herrero, Almudena; Ward, Martin J.

    1997-01-01

    We present a multiwavelength study of the interacting starburst galaxy NGC 7771, including new optical and ultra-violet spectra and a previously unpublished soft X-ray ROSAT image and spectrum. The far-infrared, radio, and X-ray fluxes suggest that a massive burst of star-formation is currently in progress but the small equivalent width of the Balmer emission lines (equivalent width H(alpha approximately equals 100 A), the weak UV flux, the low abundance of ionised oxygen, and the shape of the optical spectrum lead us to conclude that there are few 0 stars. This might normally suggest that star-formation has ceased but the galaxy's barred gravitational potential and large gas reserves imply that this should not be so, and we therefore consider other explanations. We argue that the observations cannot be due to effects of geometry, density bounded nebulae, or dust within the nebulae, and conclude that a truncated IMF is required. The dwarf galaxy NGC 7770 appears to be in the initial stages of a merger with NGC 7771, and the resulting tidal perturbations may have induced the apparent two-armed spiral pattern, and driven a substantial fraction of the disk gas inwards. The presence of a bulge in NGC 7771 may be moderating the starburst so that, while still occuring on a large scale with a supernova rate of 0.8-1/yr, it is less violent and the IMF has a relatively low upper mass limit. We find that there is a cluster of stars obscuring part of the starburst region, and we offer an explanation of its origin.

  11. THE ACS NEARBY GALAXY SURVEY TREASURY

    SciTech Connect

    Dalcanton, Julianne J.; Williams, Benjamin F.; Rosema, Keith; Gogarten, Stephanie M.; Christensen, Charlotte; Gilbert, Karoline; Hodge, Paul; Seth, Anil C.; Dolphin, Andrew; Holtzman, Jon; Skillman, Evan D.; Weisz, Daniel; Cole, Andrew; Girardi, Leo; Karachentsev, Igor D.; Olsen, Knut; Freeman, Ken; Gallart, Carme; De Jong, Roelof S. E-mail: ben@astro.washington.edu E-mail: stephanie@astro.washington.edu E-mail: fabio@astro.washington.edu E-mail: aseth@cfa.harvard.edu

    2009-07-15

    The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D < 4 Mpc). The survey volume encompasses 69 galaxies in diverse environments, including close pairs, small and large groups, filaments, and truly isolated regions. The galaxies include a nearly complete range of morphological types spanning a factor of {approx}10{sup 4} in luminosity and star formation rate. The survey data consist of images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST), supplemented with archival data and new Wide Field Planetary Camera 2 (WFPC2) imaging taken after the failure of ACS. Survey images include wide field tilings covering the full radial extent of each galaxy, and single deep pointings in uncrowded regions of the most massive galaxies in the volume. The new wide field imaging in ANGST reaches median 50% completenesses of m {sub F475W} = 28.0 mag, m {sub F606W} = 27.3 mag, and m {sub F814W} = 27.3 mag, several magnitudes below the tip of the red giant branch (TRGB). The deep fields reach magnitudes sufficient to fully resolve the structure in the red clump. The resulting photometric catalogs are publicly accessible and contain over 34 million photometric measurements of >14 million stars. In this paper we present the details of the sample selection, imaging, data reduction, and the resulting photometric catalogs, along with an analysis of the photometric uncertainties (systematic and random), for both ACS and WFPC2 imaging. We also present uniformly derived relative distances measured from the apparent magnitude of the TRGB.

  12. The IMACS Cluster Building Survey. V. Further Evidence for Starburst Recycling from Quantitative Galaxy Morphologies

    NASA Astrophysics Data System (ADS)

    Abramson, Louis E.; Dressler, Alan; Gladders, Michael D.; Oemler, Augustus, Jr.; Poggianti, Bianca M.; Monson, Andrew; Persson, Eric; Vulcani, Benedetta

    2013-11-01

    Using J- and K s-band imaging obtained as part of the IMACS Cluster Building Survey (ICBS), we measure Sérsic indices for 2160 field and cluster galaxies at 0.31 < z < 0.54. Using both mass- and magnitude-limited samples, we compare the distributions for spectroscopically determined passive, continuously star-forming, starburst, and post-starburst systems and show that previously established spatial and statistical connections between these types extend to their gross morphologies. Outside of cluster cores, we find close structural ties between starburst and continuously star-forming, as well as post-starburst and passive types, but not between starbursts and post-starbursts. These results independently support two conclusions presented in Paper II of this series: (1) most starbursts are the product of a non-disruptive triggering mechanism that is insensitive to global environment, such as minor mergers; (2) starbursts and post-starbursts generally represent transient phases in the lives of "normal" star-forming and quiescent galaxies, respectively, originating from and returning to these systems in closed "recycling" loops. In this picture, spectroscopically identified post-starbursts constitute a minority of all recently terminated starbursts, largely ruling out the typical starburst as a quenching event in all but the densest environments. Data were obtained using the 6.5 m Magellan Telescopes at Las Campanas Observatory, Chile.

  13. THE IMACS CLUSTER BUILDING SURVEY. V. FURTHER EVIDENCE FOR STARBURST RECYCLING FROM QUANTITATIVE GALAXY MORPHOLOGIES

    SciTech Connect

    Abramson, Louis E.; Gladders, Michael D.; Dressler, Alan; Oemler, Augustus Jr.; Monson, Andrew; Persson, Eric; Poggianti, Bianca M.; Vulcani, Benedetta

    2013-11-10

    Using J- and K{sub s}-band imaging obtained as part of the IMACS Cluster Building Survey (ICBS), we measure Sérsic indices for 2160 field and cluster galaxies at 0.31 < z < 0.54. Using both mass- and magnitude-limited samples, we compare the distributions for spectroscopically determined passive, continuously star-forming, starburst, and post-starburst systems and show that previously established spatial and statistical connections between these types extend to their gross morphologies. Outside of cluster cores, we find close structural ties between starburst and continuously star-forming, as well as post-starburst and passive types, but not between starbursts and post-starbursts. These results independently support two conclusions presented in Paper II of this series: (1) most starbursts are the product of a non-disruptive triggering mechanism that is insensitive to global environment, such as minor mergers; (2) starbursts and post-starbursts generally represent transient phases in the lives of 'normal' star-forming and quiescent galaxies, respectively, originating from and returning to these systems in closed 'recycling' loops. In this picture, spectroscopically identified post-starbursts constitute a minority of all recently terminated starbursts, largely ruling out the typical starburst as a quenching event in all but the densest environments.

  14. Alma observations of nearby luminous infrared galaxies with various agn energetic contributions using dense gas tracers

    SciTech Connect

    Imanishi, Masatoshi; Nakanishi, Kouichiro

    2014-07-01

    We present the results of our ALMA Cycle 0 observations, using HCN/HCO{sup +}/HNC J = 4-3 lines, of six nearby luminous infrared galaxies with various energetic contributions from active galactic nuclei (AGNs) estimated from previous infrared spectroscopy. These lines are very effective for probing the physical properties of high-density molecular gas around the hidden energy sources in the nuclear regions of these galaxies. We find that HCN to HCO{sup +} J = 4-3 flux ratios tend to be higher in AGN-important galaxies than in starburst-dominated regions, as was seen at the J = 1-0 transition, while there is no clear difference in the HCN-to-HNC J = 4-3 flux ratios among observed sources. A galaxy with a starburst-type infrared spectral shape and very large molecular line widths shows a high HCN-to-HCO{sup +} J = 4-3 flux ratio, which could be due to turbulence-induced heating. We propose that enhanced HCN J = 4-3 emission relative to HCO{sup +} J = 4-3 could be used to detect more energetic activity than normal starbursts, including deeply buried AGNs, in dusty galaxy populations.

  15. Hα Imaging of Nearby Seyfert Host Galaxies

    NASA Astrophysics Data System (ADS)

    Theios, Rachel L.; Malkan, Matthew A.; Ross, Nathaniel R.

    2016-05-01

    We used narrowband (Δλ = 70 Å) interference filters with the CCD imaging camera on the Nickel 1.0 m telescope at Lick Observatory to observe 31 nearby (z < 0.03) Seyfert galaxies in the 12 μm active galaxy sample. We obtained pure emission-line images of each galaxy, which reach down to a flux limit of 7.3 × 10-15 erg cm-2 s-1 arcsec-2, and corrected these images for [N ii] emission and extinction. We separated the Hα emission line of the “nucleus” (central 100-1000 pc) from that of the host galaxy. The extended Hα emission is expected to be powered by newly formed hot stars, and indeed correlates well with other indicators of current star formation rates (SFRs) in these galaxies: extended 7.7 μm polycyclic aromatic hydrocarbon, total far-infrared, and radio luminosity. Relative to what would be expected from recent star formation, there is a 0.8 dex excess of radio emission in our Seyfert galaxies. The Hα luminosity we measured in the centers of our galaxies is dominated by the active galactic nucleus (AGN), and is linearly correlated with the hard X-ray luminosity. There is, however, an upward offset of 1 dex in this correlation for the Seyfert 1s, because their nuclear Hα emission includes a strong additional contribution from the broad-line region. We found a correlation between SFR and AGN luminosity. In spite of selection effects, we concluded that the absence of bright Seyfert nuclei in galaxies with low SFRs is real, albeit only weakly significant. Finally, we used our measured spatial distributions of Hα emission to determine what these Seyfert galaxies would look like when observed through fixed apertures (e.g., a spectroscopic fiber) at high redshifts. We found that although all of these Seyfert galaxies would be detectable emission-line galaxies at any redshift, most of them would appear to be dominated by (>67%) their H ii region emission. Only the most luminous AGNs (log(L Hα /erg s-1) > 41.5) would still be identified as such at z

  16. Hα Imaging of Nearby Seyfert Host Galaxies

    NASA Astrophysics Data System (ADS)

    Theios, Rachel L.; Malkan, Matthew A.; Ross, Nathaniel R.

    2016-05-01

    We used narrowband (Δλ = 70 Å) interference filters with the CCD imaging camera on the Nickel 1.0 m telescope at Lick Observatory to observe 31 nearby (z < 0.03) Seyfert galaxies in the 12 μm active galaxy sample. We obtained pure emission-line images of each galaxy, which reach down to a flux limit of 7.3 × 10‑15 erg cm‑2 s‑1 arcsec‑2, and corrected these images for [N ii] emission and extinction. We separated the Hα emission line of the “nucleus” (central 100–1000 pc) from that of the host galaxy. The extended Hα emission is expected to be powered by newly formed hot stars, and indeed correlates well with other indicators of current star formation rates (SFRs) in these galaxies: extended 7.7 μm polycyclic aromatic hydrocarbon, total far-infrared, and radio luminosity. Relative to what would be expected from recent star formation, there is a 0.8 dex excess of radio emission in our Seyfert galaxies. The Hα luminosity we measured in the centers of our galaxies is dominated by the active galactic nucleus (AGN), and is linearly correlated with the hard X-ray luminosity. There is, however, an upward offset of 1 dex in this correlation for the Seyfert 1s, because their nuclear Hα emission includes a strong additional contribution from the broad-line region. We found a correlation between SFR and AGN luminosity. In spite of selection effects, we concluded that the absence of bright Seyfert nuclei in galaxies with low SFRs is real, albeit only weakly significant. Finally, we used our measured spatial distributions of Hα emission to determine what these Seyfert galaxies would look like when observed through fixed apertures (e.g., a spectroscopic fiber) at high redshifts. We found that although all of these Seyfert galaxies would be detectable emission-line galaxies at any redshift, most of them would appear to be dominated by (>67%) their H ii region emission. Only the most luminous AGNs (log(L Hα /erg s‑1) > 41.5) would still be identified as

  17. Local starburst galaxies and their descendants. Statistics from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Bergvall, Nils; Marquart, Thomas; Way, Michael J.; Blomqvist, Anna; Holst, Emma; Östlin, Göran; Zackrisson, Erik

    2016-03-01

    Aims: Despite strong interest in the starburst phenomenon in extragalactic astronomy, the concept remains ill-defined. Here we use a strict definition of starburst to examine the statistical properties of starburst galaxies in the local universe. We also seek to establish links between starburst galaxies, post-starburst (hereafter postburst) galaxies, and active galaxies. Methods: Data were selected from the Sloan Digital Sky Survey DR7. We applied a novel method of treating dust attenuation and derive star formation rates, ages, and stellar masses assuming a two-component stellar population model. Dynamical masses are calculated from the width of the Hα line. These masses agree excellently with the photometric masses. The mass (gas+stars) range is ~109-1011.5ℳ⊙. As a selection criterion for starburst galaxies, we use, the birthrate parameter, b = SFR/ ⟨ SFR ⟩, requiring that b ≥ 3. For postburst galaxies, we use, the equivalent width of Hδ in absorption with the criterion EWHδ,abs ≥ 6 Å. Results: We find that only 1% of star-forming galaxies are starburst galaxies. They contribute 3-6% to the stellar production and are therefore unimportant for the local star formation activity. The median starburst age is 70 Myr roughly independent of mass, indicating that star formation is mainly regulated by local feedback processes. The b-parameter strongly depends on burst age. Values close to b = 60 are found at ages ~10 Myr, while almost no starbursts are found at ages >1 Gyr. The median baryonic burst mass fraction of sub-L∗ galaxies is 5% and decreases slowly towards high masses. The median mass fraction of the recent burst in the postburst sample is 5-10%. A smaller fraction of the postburst galaxies, however, originates in non-bursting galaxies. The age-mass distribution of the postburst progenitors (with mass fractions >3%) is bimodal with a break at logℳ(ℳ⊙) ~ 10.6, above which the ages are doubled. The starburst and postburst luminosity

  18. The Radio-Gamma Correlation in Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Eichmann, B.; Becker Tjus, J.

    2016-04-01

    We present a systematic study of non-thermal electron-proton plasma and its emission processes in starburst galaxies in order to explain the correlation between the luminosity in the radio band and the recently observed gamma luminosity. In doing so, a steady state description of the cosmic-ray (CR) electrons and protons within the spatially homogeneous starburst is considered where continuous momentum losses are included as well as catastrophic losses due to diffusion and advection. The primary source of the relativistic CRs, e.g., supernova remnants, provides a quasi-neutral plasma with a power-law spectrum in momentum where we account for rigidity-dependent differences between the electron and proton spectrum. We examine the resulting leptonic and hadronic radiation processes by synchrotron radiation, inverse Compton scattering, Bremsstrahlung, and hadronic pion production. Finally, the observations of NGC 253, M82, NGC 4945, and NGC 1068 in the radio and gamma-ray bands as well as the observed supernova rate are used to constrain a best-fit model. In the case of NGC 253, M82, and NGC 4945 our model is able to accurately describe the data, showing that: (i) supernovae are the dominant particle accelerators for NGC 253, M82, and NGC 4945, but not for NGC 1068; (ii) all considered starburst galaxies are poor proton calorimeters in which for NGC 253 the escape is predominantly driven by the galactic wind, whereas the diffusive escape dominates in NGC 4945 and M82 (at energies >1 TeV); and (iii) secondary electrons from hadronic pion production are important to model the radio flux, but the associated neutrino flux is below the current observation limit.

  19. The Radio–Gamma Correlation in Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Eichmann, B.; Becker Tjus, J.

    2016-04-01

    We present a systematic study of non-thermal electron–proton plasma and its emission processes in starburst galaxies in order to explain the correlation between the luminosity in the radio band and the recently observed gamma luminosity. In doing so, a steady state description of the cosmic-ray (CR) electrons and protons within the spatially homogeneous starburst is considered where continuous momentum losses are included as well as catastrophic losses due to diffusion and advection. The primary source of the relativistic CRs, e.g., supernova remnants, provides a quasi-neutral plasma with a power-law spectrum in momentum where we account for rigidity-dependent differences between the electron and proton spectrum. We examine the resulting leptonic and hadronic radiation processes by synchrotron radiation, inverse Compton scattering, Bremsstrahlung, and hadronic pion production. Finally, the observations of NGC 253, M82, NGC 4945, and NGC 1068 in the radio and gamma-ray bands as well as the observed supernova rate are used to constrain a best-fit model. In the case of NGC 253, M82, and NGC 4945 our model is able to accurately describe the data, showing that: (i) supernovae are the dominant particle accelerators for NGC 253, M82, and NGC 4945, but not for NGC 1068; (ii) all considered starburst galaxies are poor proton calorimeters in which for NGC 253 the escape is predominantly driven by the galactic wind, whereas the diffusive escape dominates in NGC 4945 and M82 (at energies >1 TeV); and (iii) secondary electrons from hadronic pion production are important to model the radio flux, but the associated neutrino flux is below the current observation limit.

  20. THE DRIVING MECHANISM OF STARBURSTS IN GALAXY MERGERS

    SciTech Connect

    Teyssier, Romain; Chapon, Damien; Bournaud, Frederic

    2010-09-10

    We present hydrodynamic simulations of a major merger of disk galaxies, and study the interstellar medium (ISM) dynamics and star formation (SF) properties. High spatial and mass resolutions of 12 pc and 4 x 10{sup 4} M {sub sun} allow us to resolve cold and turbulent gas clouds embedded in a warmer diffuse phase. We compare lower-resolution models, where the multiphase ISM is not resolved and is modeled as a relatively homogeneous and stable medium. While merger-driven bursts of SF are generally attributed to large-scale gas inflows toward the nuclear regions, we show that once a realistic ISM is resolved, the dominant process is actually gas fragmentation into massive and dense clouds and rapid SF therein. As a consequence, SF is more efficient by a factor of up to {approx}10 and is also somewhat more extended, while the gas density probability distribution function rapidly evolves toward very high densities. We thus propose that the actual mechanism of starburst triggering in galaxy collisions can only be captured at high spatial resolution and when the cooling of gas is modeled down to less than 10{sup 3} K. Not only does our model reproduce the properties of the Antennae system, but it also explains the 'starburst mode' recently revealed in high-redshift mergers compared to quiescent disks.

  1. Starbursts and dusty tori in distant 3CR radio galaxies

    NASA Astrophysics Data System (ADS)

    Podigachoski, Pece; Rocca-Volmerange, Brigitte; Barthel, Peter; Drouart, Guillaume; Fioc, Michel

    2016-11-01

    We present a study of the complete ultraviolet to submillimetre spectral energy distributions (SEDs) of 12 3CR radio galaxy hosts in the redshift range 1.0 < z < 2.5, which were all detected in the far-infrared by the Herschel Space Observatory. The study employs the new spectro-chemical evolutionary code PÉGASE.3, in combination with recently published clumpy active galactic nuclei (AGN) torus models. We uncover the properties of the massive host galaxy stellar populations, the AGN torus luminosities, and the properties of the recent starbursts, which had earlier been inferred in these objects from their infrared SEDs. The PÉGASE.3 fitting yields very luminous (up to 1013 L⊙) young stellar populations with ages of several hundred million years in hosts with masses exceeding 1011 M⊙. Dust masses are seen to increase with redshift, and a surprising correlation - or better upper envelope behaviour - is found between the AGN torus luminosity and the starburst luminosity, as revealed by their associated dust components. The latter consistently exceeds the former by a constant factor, over a range of one order of magnitude in both quantities.

  2. Starbursts and dusty tori in distant 3CR radio galaxies

    NASA Astrophysics Data System (ADS)

    Podigachoski, Pece; Rocca-Volmerange, Brigitte; Barthel, Peter; Drouart, Guillaume; Fioc, Michel

    2016-08-01

    We present a study of the complete ultraviolet to submillimetre spectral energy distributions (SEDs) of twelve 3CR radio galaxy hosts in the redshift range 1.0 < z < 2.5, which were all detected in the far-infrared by the Herschel Space Observatory. The study employs the new spectro-chemical evolutionary code PÉGASE.3, in combination with recently published clumpy AGN torus models. We uncover the properties of the massive host galaxy stellar populations, the AGN torus luminosities, and the properties of the recent starbursts, which had earlier been inferred in these objects from their infrared SEDs. The PÉGASE.3 fitting yields very luminous (up to 1013 L⊙) young stellar populations with ages of several hundred million years in hosts with masses exceeding 1011 M⊙. Dust masses are seen to increase with redshift, and a surprising correlation - or better upper envelope behaviour - is found between the AGN torus luminosity and the starburst luminosity, as revealed by their associated dust components. The latter consistently exceeds the former by a constant factor, over a range of one order of magnitude in both quantities.

  3. A NICMOS search for obscured supernovae in starburst galaxies

    NASA Astrophysics Data System (ADS)

    Cresci, G.; Mannucci, F.; Della Valle, M.; Maiolino, R.

    2007-02-01

    The detection of obscured supernovae (SNe) in near-infrared monitoring campaigns of starburst galaxies has shown that a significant fraction of SNe is missed by optical surveys. However, the number of SNe detected in ground-based near-IR observations is still significantly lower than the number of SNe extrapolated from the FIR luminosity of the hosts. A possibility is that most SNe occur within the nuclear regions, where the limited angular resolution of ground-based observations prevents their detection. This issue prompted us to exploit the superior angular resolution of NICMOS-HST to search for obscured SNe within the first kpc from the nucleus of strong starbursting galaxies. A total of 17 galaxies were observed in SNAPSHOT mode. Based on their FIR luminosity, we did not expect to detect fewer than ~ 12 SNe. However, no confirmed SN event was found. From our data we derived an observed nuclear SN rate <0.5 SN/yr per galaxy. The shortage of SN detections can be explained by a combination of several effects. The most important are: i) the existence of a strong extinction, A_V⪆ 11; ii) most SNe occur within the first 0.5 arcsec (which corresponds in our sample to about 500 pc) where even NICMOS is unable to detect SN events. Based on observations made with the NASA/ESA Hubble Space Telescope associated with program 9726, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555, and on data obtained at the VLT through the ESO program 272.D-5043.

  4. Global physical conditions of the interstellar medium in nearby galaxies

    NASA Astrophysics Data System (ADS)

    Negishi, T.; Onaka, T.; Chan, K.-W.; Roellig, T. L.

    2001-08-01

    Far-infrared spectra (43-197 mu m) of 34 nearby galaxies obtained by the Long Wavelength Spectrometer (LWS) aboard the Infrared Space Observatory (ISO) were analyzed to investigate the general properties of interstellar matter in galaxies. The present sample includes not only normal galaxies but also starbursts and active galactic nuclei (AGNs). Far-infrared forbidden lines, such as [C Ii]158 mu m, [O I]63 mu m, [N Ii]122 mu m, and [O Iii]88 mu m, were detected in most of the sample galaxies. [O I]145 mu m line was detected in 13 galaxies. The line fluxes of [C Ii]158 mu m and [N Ii]122 mu m relative to the total far-infrared flux (FIR) decrease as the far-infrared color becomes bluer, while the ratio of the [O I]63 mu m flux to FIR does not show a systematic trend with the color. The [O Iii]88 mu m to FIR ratio shows a large scatter with a weak trend of increase with the color. AGNs do not show any distinguishable trend from normal and starburst galaxies in the far-infrared spectra, suggesting that the far-infrared emission is mainly driven by star-formation activities even in AGNs. We estimate the physical conditions of photodissociation regions (PDRs) in the sample galaxies, such as the far-ultraviolet radiation field intensity G0 and the gas density n by assuming that all the observed [O I]63 mu m and far-infrared continuum emissions come from PDRs. Comparison with PDR models indicates that G0 ranges from 102-104 and n ~ 102-104 cm-3. The present results also suggest that n varies proportionally with G0. The ratio of [C Ii] 158 mu m to CO (J=1-0) line emission supports the linear increase in n with G0. We estimate that about a half of [C Ii]158 mu m emission originates from PDRs and attribute the rest to the emission as coming from low-density diffuse ionized gas. The estimated intensity of [C Ii]158 mu m from the ionized gas is compatible with the observed intensity of [N Ii]122 mu m if both lines come from the same diffuse ionized gas. The present analysis

  5. A massive, cooling-flow-induced starburst in the core of a luminous cluster of galaxies.

    PubMed

    McDonald, M; Bayliss, M; Benson, B A; Foley, R J; Ruel, J; Sullivan, P; Veilleux, S; Aird, K A; Ashby, M L N; Bautz, M; Bazin, G; Bleem, L E; Brodwin, M; Carlstrom, J E; Chang, C L; Cho, H M; Clocchiatti, A; Crawford, T M; Crites, A T; de Haan, T; Desai, S; Dobbs, M A; Dudley, J P; Egami, E; Forman, W R; Garmire, G P; George, E M; Gladders, M D; Gonzalez, A H; Halverson, N W; Harrington, N L; High, F W; Holder, G P; Holzapfel, W L; Hoover, S; Hrubes, J D; Jones, C; Joy, M; Keisler, R; Knox, L; Lee, A T; Leitch, E M; Liu, J; Lueker, M; Luong-Van, D; Mantz, A; Marrone, D P; McMahon, J J; Mehl, J; Meyer, S S; Miller, E D; Mocanu, L; Mohr, J J; Montroy, T E; Murray, S S; Natoli, T; Padin, S; Plagge, T; Pryke, C; Rawle, T D; Reichardt, C L; Rest, A; Rex, M; Ruhl, J E; Saliwanchik, B R; Saro, A; Sayre, J T; Schaffer, K K; Shaw, L; Shirokoff, E; Simcoe, R; Song, J; Spieler, H G; Stalder, B; Staniszewski, Z; Stark, A A; Story, K; Stubbs, C W; Suhada, R; van Engelen, A; Vanderlinde, K; Vieira, J D; Vikhlinin, A; Williamson, R; Zahn, O; Zenteno, A

    2012-08-16

    In the cores of some clusters of galaxies the hot intracluster plasma is dense enough that it should cool radiatively in the cluster's lifetime, leading to continuous 'cooling flows' of gas sinking towards the cluster centre, yet no such cooling flow has been observed. The low observed star-formation rates and cool gas masses for these 'cool-core' clusters suggest that much of the cooling must be offset by feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical and infrared observations of the galaxy cluster SPT-CLJ2344-4243 (ref. 11) at redshift z = 0.596. These observations reveal an exceptionally luminous (8.2 × 10(45) erg s(-1)) galaxy cluster that hosts an extremely strong cooling flow (around 3,820 solar masses a year). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (formation of around 740 solar masses a year), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool-core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star-formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form through accretion of the intracluster medium, rather than (as is currently thought) assembling entirely via mergers.

  6. Direct Measurement of the Supernova Rate in Starburst Galaxies

    NASA Technical Reports Server (NTRS)

    Bregman, Jesse D.; Temi, Pasquale; Rank, David; DeVincenzi, Donald L. (Technical Monitor)

    1999-01-01

    Supernovae play a key role in the dynamics, structure, and chemical evolution of galaxies. The massive stars that end their lives as supernovae live for short times. Many are still associated with dusty star formation regions when they explode, making them difficult to observe at visible wavelengths. In active star forming regions (galactic nuclei and starburst regions), dust extintion is especially severe. Thus, determining the supernova rate in the active star forming regions of galaxies, where the supernova rate can be one or two orders of magnitude higher than the average, has proven to be difficult. From observations of SN1987A, we know that the [NiII] 6.63 micron emission line was the strongest line in the infrared spectrum for a period of a year and a half after the explosion. Since dust extintion is much less at 6.63 pm than at visible wavelengths (A(sub 6.63)/A(sub V) = 0.025), the NiII line can be used as a sensitive probe for the detection of recent supernovae. We have observed a sample of starburst galaxies at 6.63 micron using ISOCAM to search for the NiII emission line characteristic of recent supernovae. We did not detect any NiII line emission brighter than a 5sigma limit of 5 mJy. We can set upper limits to the supernova rate in our sample, scaled to the rate in M82, of less than 0.3 per year at the 90% confidence level using Bayesian methods. Assuming that a supernova would have a NiII with the same luminosity as observed in SN1987A, we find less than 0.09 and 0.15 per year at the 50% and 67% confidence levels. These rates are somewhat less if a more normal type II supernovae has a NiII line luminosity greater than the line in SN1987A.

  7. Direct Measurement of the Supernova Rate in Starburst Galaxies

    NASA Technical Reports Server (NTRS)

    Bregman, J. D.; Temi, P.; Rank, D.

    2000-01-01

    Supernovae play a key role in the dynamics, structure, and chemical evolution of galaxies. The massive stars that end their lives as supernovae live for short enough times that many are still associated with dusty star formation regions when they explode, making them difficult to observe at visible wavelengths. In active star forming regions (galactic nuclei and starburst regions), dust extinction is especially severe. Thus, determining the supernova rate in active star forming regions of galaxies, where the supernova rate can be one or two orders of magnitude higher than the average, has proven to be difficult. From observations of SN1987A, we know that the [NiII] 6.63 micrometer emission line was the strongest line in the infrared spectrum for a period of a year and half after th explosion. Since dust extinction is much less at 6.63 micrometers than at visible wavelengths (A(sub 6.63)/A(sub V) = 0.025), the [NiII] line can be used as a sensitive probe for the detection of recent supernovae. We have observed a sample of starburst galaxies at 6.63 micrometers using ISOCAM to search for the [NiII] emission line characteristic of recent supernovae. We did not detect any [NiII] line emission brighter than a 5-sigma limit of 5 mJy. We can set upper limits to the supernova rate in our sample, scaled ot the rate in M82, of less than 0.3 per year at the 90% confidence level using Bayesian methods. Assuming that a supernova would have a [NiII] line with the same luminosity as observed in SN1987A, we find less than 0.09 and 0.15 per year at the 50% and 67% confidence levels. These rates are somewhat less if a more normal type II supernovae has a [NiII] line luminosity greater than the line in SN1987A.

  8. ORIENTATION OF BRIGHTER GALAXIES IN NEARBY GALAXY CLUSTERS

    SciTech Connect

    Panko, E.; Juszczyk, T.; Flin, P. E-mail: sfflin@cyf-kr.edu.pl

    2009-12-15

    A sample of 6188 nearby galaxy structures, complete to r{sub F} = 18fm3 and containing at least 10 members each, was the observational basis for an investigation of the alignment of bright galaxies with the major axes for the parent clusters. The distribution of position angles for galaxies within the clusters, specifically the brightest, the second brightest, the third, and the tenth brightest galaxies was tested for isotropy. Galaxy position angles appear to be distributed isotropically, as are the distributions of underlying cluster structure position angles. The characterization of galaxy structures according to richness class also appears to be isotropic. Characterization according to BM types, which are known for 1056 clusters, is more interesting. Only in the case of clusters of BM type I is there an alignment of the brightest cluster member with the major axis of the parent cluster. The effect is observed at the 2 significance level. In other investigated cases the distributions are isotropic. The results confirm the special role of cD galaxies in the origin/evolution of large-scale structures.

  9. Extinction Mapping of Nearby Galaxies with LEGUS

    NASA Astrophysics Data System (ADS)

    Kahre, Lauren; Walterbos, Rene A. M.; Sabbi, Elena; Thilker, David A.; Ubeda, Leonardo; LEGUS Science Team

    2016-01-01

    Using 5-band (NUV (2750 A), U, B, V, I) photometry from the Legacy ExtraGalactic Ultraviolet Survey (LEGUS), we generate extinction maps for nearby (within 10 Mpc) galaxies at resolutions of a few arcseconds. Dust is commonly used as a tracer for cold dense gas, either through IR and NIR emission maps or through extinction mapping. Extinction mapping has been used to trace dust column densities in the Milky Way, the Magellanic Clouds, and M31. The maps for M31 use IR and NIR photometry of red giant branch stars, which is more difficult to obtain for more distant galaxies. Our method uses the extinctions derived for individual massive stars using the isochrone-matching method described by Kim et al. (2012). With our 5-band photometry, which extends into the UV, we are able to trace even small amounts of extinction. These maps are then compared to HI and CO maps of the same galaxies with the goal of constraining the dust-to-gas mass ratio, which we can then correlate with the gas phase metallicity from other observations. This poster will demonstrate the technique on a few galaxies, but the project will subsequently be expanded to cover the full LEGUS sample of nearly 50 galaxies. These maps can then be used to correct massive star and cluster photometry and HII region Halpha observations for the effects of extinction in order to better characterize star formation rates and massive stellar populations for other projects, such as initial mass function studies and ionization balance studies for HII regions and the diffuse ionized gas.

  10. New candidate supernova remnants in nearby galaxies

    NASA Astrophysics Data System (ADS)

    Kopsacheili, Maria; Boumis, Panos; Leonidaki, Ioanna; Zezas, Andreas

    2016-06-01

    Supernova remnants (SNRs) are objects of high importance since they provide major amounts of energy to the interstellar medium (ISM), while at the same time, they depict the end-point state of massive stars (M > 8 Mo). In order to investigate the physical properties of these objects and their interplay with their environment, we have embarked in an extensive investigation of the SNR populations in nearby galaxies of different morphological types. This effort has been initiated with six galaxies, mostly irregulars,in the northern hemisphere (Leonidaki et al. 2010, 2013). Following this context, we present new candidate SNRs (down to fluxes of 10^{-16} erg sec^{-1} cm^-2) of five spiral galaxies in the southern hemisphere (NGC 45, NGC 55, NGC 1313, NGC 1672, NGC 7793), based on deep narrow-band Hα and [S II] images observed with the 4m Blanco telescope at CTIO, Chile. The new detections were achieved by calculating the [S II]/Hα flux ratio, where all sources with [S II]/ Hα > 0.4 were considered as candidate SNRs. Furthermore, we use the derived properties of the newly detected candidate SNRs ([S II]/Hα ratios, Hα fluxes) to investigate how they are distributed according to their brightness and their behavior in different environments (irregulars vs. spirals).

  11. CONNECTIONS BETWEEN GALAXY MERGERS AND STARBURST: EVIDENCE FROM THE LOCAL UNIVERSE

    SciTech Connect

    Luo, Wentao; Yang, Xiaohu; Zhang, Youcai E-mail: xyang@sjtu.edu.cn

    2014-07-01

    Major mergers and interactions between gas-rich galaxies with comparable masses are thought to be the main triggers of starburst. In this work, we study, for a large stellar mass range, the interaction rate of the starburst galaxies in the local universe. We focus independently on central and satellite star forming galaxies extracted from the Sloan Digital Sky Survey. Here the starburst galaxies are selected in the star formation rate (SFR) stellar mass plane with SFRs five times larger than the median value found for ''star forming'' galaxies of the same stellar mass. Through visual inspection of their images together with close companions determined using spectroscopic redshifts, we find that ∼50% of the ''starburst'' populations show evident merger features, i.e., tidal tails, bridges between galaxies, double cores, and close companions. In contrast, in the control sample we selected from the normal star forming galaxies, only ∼19% of galaxies are associated with evident mergers. The interaction rates may increase by ∼5% for the starburst sample and 2% for the control sample if close companions determined using photometric redshifts are considered. The contrast of the merger rate between the two samples strengthens the hypothesis that mergers and interactions are indeed the main causes of starburst.

  12. MaNGA: Mapping Nearby Galaxies at Apache Point Observatory

    NASA Astrophysics Data System (ADS)

    Weijmans, A.-M.; MaNGA Team

    2016-10-01

    MaNGA (Mapping Nearby Galaxies at APO) is a galaxy integral-field spectroscopic survey within the fourth generation Sloan Digital Sky Survey (SDSS-IV). It will be mapping the composition and kinematics of gas and stars in 10,000 nearby galaxies, using 17 differently sized fiber bundles. MaNGA's goal is to provide new insights in galaxy formation and evolution, and to deliver a local benchmark for current and future high-redshift studies.

  13. An excess of dusty starbursts related to the Spiderweb galaxy

    NASA Astrophysics Data System (ADS)

    Dannerbauer, H.; Kurk, J. D.; De Breuck, C.; Wylezalek, D.; Santos, J. S.; Koyama, Y.; Seymour, N.; Tanaka, M.; Hatch, N.; Altieri, B.; Coia, D.; Galametz, A.; Kodama, T.; Miley, G.; Röttgering, H.; Sanchez-Portal, M.; Valtchanov, I.; Venemans, B.; Ziegler, B.

    2014-10-01

    We present APEX LABOCA 870 μm observations of the field around the high-redshift radio galaxy MRC1138-262 at z = 2.16. We detect 16 submillimeter galaxies (SMGs) in this ~140 arcmin2 bolometer map with flux densities in the range 3-11 mJy. The raw number counts indicate a density of SMGs that is up to four times that of blank field surveys. Based on an exquisite multiwavelength database, including VLA 1.4 GHz radio and infrared observations, we investigate whether these sources are members of the protocluster structure at z ≈ 2.2. Using Herschel PACS and SPIRE and Spitzer MIPS photometry, we derive reliable far-infrared (FIR) photometric redshifts for all sources. Follow-up VLT ISAAC and SINFONI NIR spectra confirm that four of these SMGs have redshifts of z ≈ 2.2. We also present evidence that another SMG in this field, detected earlier at 850 μm, has a counterpart that exhibits Hα and CO(1-0) emission at z = 2.15. Including the radio galaxy and two SMGs with FIR photometric redshifts at z = 2.2, we conclude that at least eight submm sources are part of the protocluster at z = 2.16 associated with the radio galaxy MRC1138-262. We measure a star formation rate density SFRD ~1500 M⊙ yr-1 Mpc-3, four magnitudes higher than the global SFRD of blank fields at this redshift. Strikingly, these eight sources are concentrated within a region of 2 Mpc (the typical size of clusters in the local universe) and are distributed within the filaments traced by the HAEs at z ≈ 2.2. This concentration of massive, dusty starbursts is not centered on the submillimeter-bright radio galaxy which could support the infalling of these sources into the cluster center. Approximately half (6/11) of the SMGs that are covered by the Hα imaging data are associated with HAEs, demonstrating the potential of tracing SMG counterparts with this population. To summarize, our results demonstrate that submillimeter observations may enable us to study (proto)clusters of massive, dusty

  14. Rotating Nuclear Rings and Extreme Starbursts in Ultraluminous Galaxies

    NASA Astrophysics Data System (ADS)

    Downes, D.; Solomon, P. M.

    1998-11-01

    New CO interferometer data show that the molecular gas in infrared ultraluminous galaxies is in rotating nuclear disks or rings. The CO maps yield disk radii, kinematic major axes, rotation speeds, enclosed dynamical masses, and gas masses. The CO brightness temperatures, the double-peaked CO line profiles, the limits on thermal continuum flux from dust, and the constraint that the gas mass must be less than the dynamical mass all indicate that the CO lines are subthermally excited and moderately opaque (τ = 4 to 10). We fit kinematic models in which most of the CO flux comes from a moderate-density warm intercloud medium, rather than from self-gravitating clouds. Typical ring radii are 300 to 800 pc. We derive gas masses not from a standard CO-to-mass ratio, but from a model of radiative transfer through subthermally excited CO in the molecular disks. This model yields gas masses of ~5 × 109 M⊙, ~5 times lower than the standard method, and a ratio Mgas/L'CO~0.8 M⊙ (K km s-1 pc2)-1. In the nuclear disks, we derive a ratio of gas to dynamical mass of Mgas/Mdyn ~ 1/6, and a maximum ratio of gas to total mass surface density, μ/μtot, of 1/3. For the galaxies VII Zw 31, Arp 193, and IRAS 10565+2448, the CO position-velocity diagrams provide good evidence for rotating molecular rings with a central gap. In addition to the rotating central rings or disks, a new class of star formation region is identified, which we call an extreme starburst. These have a characteristic sizes of only 100 pc, with about 109 M⊙ of gas and an IR luminosity of ~3 × 1011 L⊙ from recently formed OB stars. Four extreme starbursts are identified in the 3 closest galaxies in the sample, including Arp 220, Arp 193, and Mrk 273. These are the most prodigious star formation events in the local universe, each representing about 1000 times as many OB stars as 30 Doradus. In Mrk 231, the CO (2-1) velocity diagram along the line of nodes shows a 1.2" diameter inner disk and a 3" diameter

  15. HNCO Abundances in Galaxies: Tracing the Evolutionary State of Starbursts

    NASA Astrophysics Data System (ADS)

    Martín, Sergio; Martín-Pintado, J.; Mauersberger, R.

    2009-03-01

    The chemistry in the central regions of galaxies is expected to be strongly influenced by their nuclear activity. To find the best tracers of nuclear activity is of key importance to understand the processes taking place in the most obscured regions of galactic nuclei. In this work, we present multiline observations of CS, C34S, HNCO, and C18O in a sample of 11 bright galaxies prototypical for different types of activity. The 32S/34S isotopic ratio is ~10, supporting the idea of an isotopical 34S enrichment due to massive star formation in the nuclear regions of galaxies. Although C32S and C34S do not seem to be significantly affected by the activity type, the HNCO abundance appears highly contrasted among starbursts (SBs). We observed HNCO abundance variations of nearly 2 orders of magnitude. The HNCO molecule is shown to be a good tracer of the amount of molecular material fueling the SB and therefore can be used as a diagnostics of the evolutionary state of a nuclear SB.

  16. The evolution of post-starburst galaxies from z=2 to 0.5

    NASA Astrophysics Data System (ADS)

    Wild, Vivienne; Almaini, Omar; Dunlop, Jim; Simpson, Chris; Rowlands, Kate; Bowler, Rebecca; Maltby, David; McLure, Ross

    2016-11-01

    We present the evolution in the number density and stellar mass functions of photometrically selected post-starburst galaxies in the UKIDSS Ultra Deep Survey, with redshifts of 0.5 < z < 2 and stellar masses log (M/M⊙) >10. We find that this transitionary species of galaxy is rare at all redshifts, contributing ˜5 per cent of the total population at z ˜ 2, to <1 per cent by z ˜ 0.5. By comparing the mass functions of quiescent galaxies to post-starburst galaxies at three cosmic epochs, we show that rapid quenching of star formation can account for 100 per cent of quiescent galaxy formation, if the post-starburst spectral features are visible for ˜250 Myr. The flattening of the low-mass end of the quiescent galaxy stellar mass function seen at z ˜ 1 can be entirely explained by the addition of rapidly quenched galaxies. Only if a significant fraction of post-starburst galaxies have features that are visible for longer than 250 Myr, or they acquire new gas and return to the star-forming sequence, can there be significant growth of the red sequence from a slower quenching route. The shape of the mass function of these transitory post-starburst galaxies resembles that of quiescent galaxies at z ˜ 2, with a preferred stellar mass of log (M/M⊙) ˜10.6, but evolves steadily to resemble that of star-forming galaxies at z < 1. This leads us to propose a dual origin for post-starburst galaxies: (1) at z ≳ 2 they are exclusively massive galaxies that have formed the bulk of their stars during a rapid assembly period, followed by complete quenching of further star formation; (2) at z ≲ 1 they are caused by the rapid quenching of gas-rich star-forming galaxies, independent of stellar mass, possibly due to environment and/or gas-rich major mergers.

  17. The evolution of post-starburst galaxies from z = 2 to z = 0.5

    NASA Astrophysics Data System (ADS)

    Wild, Vivienne; Almaini, Omar; Dunlop, Jim; Simpson, Chris; Rowlands, Kate; Bowler, Rebecca; Maltby, David; McLure, Ross

    2016-08-01

    We present the evolution in the number density and stellar mass functions of photometrically selected post-starburst galaxies in the UKIDSS Deep Survey (UDS), with redshifts of 0.5 < z < 2 and stellar masses log (M/M⊙)>10. We find that this transitionary species of galaxy is rare at all redshifts, contributing ˜5% of the total population at z ˜ 2, to <1% by z ˜ 0.5. By comparing the mass functions of quiescent galaxies to post-starburst galaxies at three cosmic epochs, we show that rapid quenching of star formation can account for 100% of quiescent galaxy formation, if the post-starburst spectral features are visible for ˜250 Myr. The flattening of the low mass end of the quiescent galaxy stellar mass function seen at z ˜ 1 can be entirely explained by the addition of rapidly quenched galaxies. Only if a significant fraction of post-starburst galaxies have features that are visible for longer than 250 Myr, or they acquire new gas and return to the star-forming sequence, can there be significant growth of the red sequence from a slower quenching route. The shape of the mass function of these transitory post-starburst galaxies resembles that of quiescent galaxies at z ˜ 2, with a preferred stellar mass of log (M/M⊙)˜10.6, but evolves steadily to resemble that of star-forming galaxies at z < 1. This leads us to propose a dual origin for post-starburst galaxies: (1) at z ≳ 2 they are exclusively massive galaxies that have formed the bulk of their stars during a rapid assembly period, followed by complete quenching of further star formation; (2) at z ≲ 1 they are caused by the rapid quenching of gas-rich star-forming galaxies, independent of stellar mass, possibly due to environment and/or gas-rich major mergers.

  18. Near-IR spectral evolution of dusty starburst galaxies

    NASA Astrophysics Data System (ADS)

    Lançon, Ariane; Rocca-Volmerange, Brigitte

    1996-11-01

    We propose a multicomponent analysis of starburst galaxies, based on a model that takes into account the young and evolved stellar components and the gas emission, with their respective extinction, in the frame of a coherent dust distribution pattern. Near-IR signatures are preferentially investigated, in order to penetrate as deep as possible into the dusty starburst cores. We computed the 1.4-2.5 μm spectra of synthetic stellar populations evolving through strong, short timescale bursts of star formation (continuum and lines, R ≃ 500). The evolution model is specifically sensitive to cool stellar populations (AGB and red supergiant stars). It takes advantage of the stellar library of Lançon & Rocca-Volmerange (1992) [A&ASS, 96, 593], observed with the same instrument (FTS/CFHT) as the analysed galaxy sample, so that the instrumental effects are minimised. The main near-IR observable constraints are the molecular signatures of CO and H2O and the slope of the continuum, observed over a range exceptionally broad for spectroscopic data. The H - K colour determined from the spectra measures the intrinsic stellar energy distribution but also differential extinction, which is further constrained by optical emission line ratios. Other observational constraints are the near-IR emission lines (Brγ, He I 2.06 μm, [Fe II] 1.64 μm, H2 2.12 μm) and the far-IR luminosity. The coherence of the results relies on the interpretation in terms of stellar populations from which all observable properties are derived, so that the link between the various wavelength ranges is secured. The luminosity LK is used for the absolute calibration. We apply this approach to the typical spectrum of the core of NGC 1614. Consistent solutions for the starburst characteristics (star-formation rate, IMF, burst age, morphology) are found and the role of each observational constraint in deriving satisfactory models is extensively discussed. The acceptable contamination of the K band light by the

  19. Investigating the relation between CO (3-2) and far-infrared luminosities for nearby merging galaxies using ASTE

    NASA Astrophysics Data System (ADS)

    Michiyama, Tomonari; Iono, Daisuke; Nakanishi, Kouichiro; Ueda, Junko; Saito, Toshiki; Ando, Misaki; Kaneko, Hiroyuki; Yamashita, Takuji; Matsuda, Yuichi; Hatsukade, Bunyo; Kikuchi, Kenichi; Komugi, Shinya; Muto, Takayuki

    2016-09-01

    We present the new single-dish CO (3-2) emission data obtained toward 19 early-stage and 7 late-stage nearby merging galaxies using the Atacama Submillimeter Telescope Experiment (ASTE). Combining with the single-dish and interferometric data of galaxies observed in previous studies, we investigate the relation between the CO (3-2) luminosity (L^' }_CO(3-2)) and the far-infrared luminosity (LFIR) in a sample of 29 early-stage and 31 late-stage merging galaxies, and 28 nearby isolated spiral galaxies. We find that normal isolated spiral galaxies and merging galaxies have different slopes (α) in the log L^' }_CO(3-2)-log LFIR plane (α ˜ 0.79 for spirals and ˜1.12 for mergers). The large slope (α > 1) for merging galaxies can be interpreted as evidence for increasing star formation efficiency (SFE = L_FIR/L^' }_CO(3-2)) as a function of LFIR. Comparing our results with sub-kpc-scale local star formation and global starburst activity in the high-z universe, we find deviations from the linear relationship in the log L^' }_CO(3-2)-log LFIR plane for the late-stage mergers and high-z star-forming galaxies. Finally, we find that the average SFE gradually increases from isolated galaxies to merging galaxies and to high-z submillimeter galaxies/quasi-stellar objects. By comparing our findings with results from numerical simulations, we suggest that: (1) inefficient starbursts triggered by disk-wide dense clumps occur in the early stage of interaction, and (2) efficient starbursts triggered by central concentration of gas occur in the final stage. A systematic high spatial resolution survey of diffuse- and dense-gas tracers is the key to confirming this scenario.

  20. Lambda = 3 mm line survey of nearby active galaxies

    NASA Astrophysics Data System (ADS)

    Aladro, R.; Martín, S.; Riquelme, D.; Henkel, C.; Mauersberger, R.; Martín-Pintado, J.; Weiß, A.; Lefevre, C.; Kramer, C.; Requena-Torres, M. A.; Armijos-Abendaño, R. J.

    2015-07-01

    Aims: We aim to better understand the imprints that the nuclear activity in galaxies leaves in the molecular gas. Methods: We used the IRAM 30 m telescope to observe the frequency range ~[86-116] GHz towards the central regions of the starburst galaxies M 83, M 82, and NGC 253, the galaxies hosting an active galactic nucleus (AGN) M 51, NGC 1068, and NGC 7469, and the ultra-luminous infrared galaxies (ULIRGs) Arp 220 and Mrk 231. Assuming local thermodynamic equilibrium (LTE), we calculated the column densities of 27 molecules and 10 isotopologues (or their upper limits in case of non-detections). Results: Among others, we report the first tentative detections of CH3CHO, HNCO, and NS in M 82 and, for the first time in the extragalactic medium, HC5N in NGC 253. Hα recombination lines were only found in M 82 and NGC 253. Vibrationally excited lines of HC3N were only detected in Arp 220. CH3CCH emission is only seen in the starburst-dominated galaxies. By comparison of the fractional abundances among the galaxies, we looked for the molecules that are best suited to characterise the chemistry of each group of galaxies (starbursts, AGNs and ULIRGs), as well as the differences among galaxies within the same group. Conclusions: Suitable species for characterising and comparing starburst galaxies are CH3OH and HNCO as tracers of large-scale shocks, which dominate early to intermediate starburst stages, and CH3CCH, c-C3H2, and HCO as tracers of UV fields, which control the intermediate-to-old or post starburst phases. M 83 shows signs of a shock-dominated environment. NGC 253 is characterised by both strong shocks and some UV fields. M 82 stands out for its bright photo-dissociated region tracers, which indicate an UV field-dominated environment. Regarding AGNs, the abundances of HCN and CN (previously claimed as enhanced in AGNs) in M 51 are similar to those in starburst galaxies, while the HCN/HCO+ ratio is high in M 51 and NGC 1068, but not in NGC 7469. We did not find

  1. ALFALFA DISCOVERY OF THE NEARBY GAS-RICH DWARF GALAXY LEO P. III. AN EXTREMELY METAL DEFICIENT GALAXY

    SciTech Connect

    Skillman, Evan D.; Berg, Danielle A.; Olive, Keith A.; McQuinn, Kristen B. W. E-mail: berg@astro.umn.edu E-mail: kmcquinn@astro.umn.edu; and others

    2013-07-01

    We present KPNO 4 m and LBT/MODS spectroscopic observations of an H II region in the nearby dwarf irregular galaxy Leo P discovered recently in the Arecibo ALFALFA survey. In both observations, we are able to accurately measure the temperature sensitive [O III] {lambda}4363 line and determine a ''direct'' oxygen abundance of 12 + log(O/H) = 7.17 {+-} 0.04. Thus, Leo P is an extremely metal deficient (XMD) galaxy, and, indeed, one of the most metal deficient star-forming galaxies ever observed. For its estimated luminosity, Leo P is consistent with the relationship between luminosity and oxygen abundance seen in nearby dwarf galaxies. Leo P shows normal {alpha} element abundance ratios (Ne/O, S/O, and Ar/O) when compared to other XMD galaxies, but elevated N/O, consistent with the ''delayed release'' hypothesis for N/O abundances. We derive a helium mass fraction of 0.2509{sup +0.0184}{sub -0.0123}, which compares well with the WMAP + BBN prediction of 0.2483 {+-} 0.0002 for the primordial helium abundance. We suggest that surveys of very low mass galaxies compete well with emission line galaxy surveys for finding XMD galaxies. It is possible that XMD galaxies may be divided into two classes: the relatively rare XMD emission line galaxies which are associated with starbursts triggered by infall of low-metallicity gas and the more common, relatively quiescent XMD galaxies like Leo P, with very low chemical abundances due to their intrinsically small masses.

  2. THE STAR FORMATION HISTORY AND CHEMICAL EVOLUTION OF STAR-FORMING GALAXIES IN THE NEARBY UNIVERSE

    SciTech Connect

    Torres-Papaqui, J. P.; Coziol, R.; Ortega-Minakata, R. A.; Neri-Larios, D. M. E-mail: rcoziol@astro.ugto.mx E-mail: daniel@astro.ugto.mx

    2012-08-01

    We have determined the metallicity (O/H) and nitrogen abundance (N/O) of a sample of 122,751 star-forming galaxies (SFGs) from the Data Release 7 of the Sloan Digital Sky Survey. For all these galaxies we have also determined their morphology and obtained a comprehensive picture of their star formation history (SFH) using the spectral synthesis code STARLIGHT. The comparison of the chemical abundance with the SFH allows us to describe the chemical evolution of the SFGs in the nearby universe (z {<=} 0.25) in a manner consistent with the formation of their stellar populations and morphologies. A high fraction (45%) of the SFGs in our sample show an excess abundance of nitrogen relative to their metallicity. We also find this excess to be accompanied by a deficiency of oxygen, which suggests that this could be the result of effective starburst winds. However, we find no difference in the mode of star formation of the nitrogen-rich and nitrogen-poor SFGs. Our analysis suggests that they all form their stars through a succession of bursts of star formation extended over a period of few Gyr. What produces the chemical differences between these galaxies seems therefore to be the intensity of the bursts: the galaxies with an excess of nitrogen are those that are presently experiencing more intense bursts or have experienced more intense bursts in their past. We also find evidence relating the chemical evolution process to the formation of the galaxies: the galaxies with an excess of nitrogen are more massive, and have more massive bulges and earlier morphologies than those showing no excess. Contrary to expectation, we find no evidence that the starburst wind efficiency decreases with the mass of the galaxies. As a possible explanation we propose that the loss of metals consistent with starburst winds took place during the formation of the galaxies, when their potential wells were still building up, and consequently were weaker than today, making starburst winds more

  3. Aspects of the interstellar medium in starburst galaxies

    NASA Technical Reports Server (NTRS)

    Fanelli, Michael N.

    1990-01-01

    Researchers are engaged in a multifaceted program to investigate the stellar content and star formation history of actively star-forming galaxies. A large body of stellar spectra have been examined to identify spectral features characteristic of specific stellar types. These spectral diagnostics are then calibrated in terms of temperature (spectral type), gravity (luminosity class) and metallicity. The spectral data is compiled into a stellar library whose members represent specific locations in the HR diagram. Through the use of population synthesis techniques, both optimizing and evolutionary approaches, the stellar luminosity function in composite populations can be determined by analysis of their integrated light. Researchers have concentrated on the ultraviolet wavelength region (lambda lambda 1200 to 3200), utilizing the International Ultraviolet Explorer (IUE) archives supplemented by additional observations. In the optical, virtually all stars will contribute to the integrated light. In the ultraviolet however, cool stars will produce negligible flux due to their steep ultraviolet-to-visual continua, greatly simplifying the investigation of the hot component in a composite population. The researchers' initial stellar library has been applied to several blue compact galaxies, (BCGs), a class of starburst galaxy which is UV luminous. BCGs possess a complex interstellar medium which affects the emergent stellar continuum in several ways. This presents a challenge to the stellar analysis but affords insight into the properties of the gas and dust from which the massive OB stars have formed. The optimizing synthesis method solves for the stellar luminosity function and extinction simultaneously. This therefore provides an independent measure of the extinction affecting the hot population component. Despite the rise of the reddening law towards the ultraviolet, BCGs are found to be brighter in the ultraviolet than expected.

  4. Aspects of the interstellar medium in starburst galaxies

    NASA Astrophysics Data System (ADS)

    Fanelli, Michael N.

    1990-07-01

    Researchers are engaged in a multifaceted program to investigate the stellar content and star formation history of actively star-forming galaxies. A large body of stellar spectra have been examined to identify spectral features characteristic of specific stellar types. These spectral diagnostics are then calibrated in terms of temperature (spectral type), gravity (luminosity class) and metallicity. The spectral data is compiled into a stellar library whose members represent specific locations in the HR diagram. Through the use of population synthesis techniques, both optimizing and evolutionary approaches, the stellar luminosity function in composite populations can be determined by analysis of their integrated light. Researchers have concentrated on the ultraviolet wavelength region (lambda lambda 1200 to 3200), utilizing the International Ultraviolet Explorer (IUE) archives supplemented by additional observations. In the optical, virtually all stars will contribute to the integrated light. In the ultraviolet however, cool stars will produce negligible flux due to their steep ultraviolet-to-visual continua, greatly simplifying the investigation of the hot component in a composite population. The researchers' initial stellar library has been applied to several blue compact galaxies, (BCGs), a class of starburst galaxy which is UV luminous. BCGs possess a complex interstellar medium which affects the emergent stellar continuum in several ways. This presents a challenge to the stellar analysis but affords insight into the properties of the gas and dust from which the massive OB stars have formed. The optimizing synthesis method solves for the stellar luminosity function and extinction simultaneously. This therefore provides an independent measure of the extinction affecting the hot population component. Despite the rise of the reddening law towards the ultraviolet, BCGs are found to be brighter in the ultraviolet than expected.

  5. Powerful Molecular Outflows in Nearby Active Galaxies

    NASA Astrophysics Data System (ADS)

    Veilleux, Sylvain; Meléndez, Marcio

    2014-07-01

    We report the results from a systematic search for molecular (OH 119 μm) outflows with Herschel-PACS† in a sample of 43 nearby (z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7-μm silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than -50 km s-1, is seen in 26 (70%) of the 37 OH-detected targets, suggesting a wide-angle (~ 145°) outflow geometry. Conversely, unambiguous evidence for molecular inflows, based on the detection of OH absorption profiles with median velocities more redshifted than +50 km s-1, is seen in only 4 objects, suggesting a planar or filamentary geometry for the inflowing gas. Terminal outflow velocities of ~ -1000 km s-1 are measured in several objects, but median outflow velocities are typically ~ -200 km s-1. While the outflow velocities show no statistically significant dependence on the star formation rate, they are distinctly more blueshifted among systems with large AGN fractions and luminosities [log (L AGN/L ⊙) >= 11.8 +/- 0.3]. The quasars in these systems play a dominant role in driving the molecular outflows. In contrast, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.

  6. Detecting planets around stars in nearby galaxies

    NASA Astrophysics Data System (ADS)

    Covone, G.; de Ritis, R.; Dominik, M.; Marino, A. A.

    2000-05-01

    The only way to detect planets around stars at distances gtrsim several kpc is by (photometric or astrometric) microlensing (mu L) observations. In this paper, we show that the capability of photometric mu L extends to the detection of signals caused by planets around stars in nearby galaxies (e.g. M31) and that there is no other method that can achieve this. Due to the large crowding, mu L experiments towards M31 can only observe the high-magnification part of a lensing light curve. Therefore, the dominating channel for mu L signals by planets is in distortions near the peak of high-magnification events as discussed by Griest & Safizadeh (\\cite{GS98}). We calculate the probability to detect planetary anomalies for mu L experiments towards M31 and find that jupiter-like planets around stars in M31 can be detected. Though the characterization of the planet(s) involved in this signal will be difficult, the absence of such signals can yield strong constraints on the abundance of jupiter-like planets.

  7. The Chemical Anatomy of Nuclei of Nearby Barred Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Meier, D. S.; Turner, J. L.

    2004-12-01

    We present images of the millimeter lines of eight molecules---C2H, C34S, N2H+, CH3OH, HNCO, HNC, HC3N, and SO---in the nuclei of the nearby barred spiral galaxies, IC 342 and Maffei 2, made with the OVRO and BIMA arrays. These maps are compared to obtain a picture of changes in chemistry on sizescales of individual giant molecular clouds (GMCs) within a nucleus and between nuclei of similar morphological type. Emission from all species except SO are detected in both galaxies. Marked differences in morphology between the observed species are seen in both galaxies. A principal component analysis (PCA) is performed to quantify differences among the images. In IC 342, the PCA reveals that while all molecules are zeroth order correlated, that is, trace dense GMCs, there are three distinct groups of molecules distinguished by the location of their emission within the nucleus. N2H+ and HNC are widespread and bright, tracing all of the GMCs. C2H and C34S, tracers of photo-dissociation region chemistry, originate exclusively from the central ˜ 5'' ring illuminated by the 60 Myr, massive central cluster. CH3OH (and HNCO), a typical tracer of grain processing, correlates well with the expected locations of bar-induced orbital shocks. In Maffei 2, the PCA demonstrates that its chemistry is quite similar to IC 342, with the molecules tending to couple together in the same groups and with the same structural components of the nucleus. C2H dominates from the central starburst region, but is significantly more extended than IC 342 because its star formation is more extended. The correlation between HNCO and CH3OH in Maffei 2 is even strongly than in IC 342, being entirely dominated by the bar ends and orbit intersections. This provides strong evidence that HNCO is formed by the same processes as CH3OH. Funding for this research is provided by the Laboratory for Astronomical Imaging at the University of Illinois through the NSF grant AST-0228953, and by NSF grants AST-0071276 and

  8. VLA Radio Continuum Imaging of Radio-Infrared Supernebulae in Starburst Galaxies at 1.3 cm

    NASA Astrophysics Data System (ADS)

    Tsai, C.-W.; Turner, J. L.; Beck, S. C.

    2005-12-01

    We present 1''-resolution VLA K-band images of 14 nearby starburst galaxies in which we have detected compact (sub-arcsecond) and luminous mid-IR sources with LWS imaging spectrograph on Keck Observatory. Of the galaxies observed, 11 are detected with strong continuum emission at 1.3 cm. In the VLA K-band where synchrotron emission is weak and dust emission has not yet kicked in, therefore the radio continuum emission should be dominated by thermal free-free emission. The strong extended free-free emission indicates the existence of ˜ 104 - 105 O stars living in active regions of these starburst galaxies. Our K-band maps also reveal many compact sources which are presumbly ''radio-infrared supernebulae", or RISN. These nebulae are dense, young (< 1 Myr), and require the immediate presence of thousands of young O stars within regions only a few parsecs in extent. RISN in these galaxies are excited by massive (105 - 106 MSun) super star clusters (SSCs) which may be the precursors to globular clusters.

  9. The role of magnetic fields in starburst galaxies as revealed by OH megamasers

    SciTech Connect

    McBride, James; Quataert, Eliot; Heiles, Carl; Bauermeister, Amber E-mail: eliot@astro.berkeley.edu

    2014-01-10

    We present estimates of magnetic field strengths in the interstellar media of starburst galaxies derived from measurements of Zeeman splitting associated with OH megamasers. The results for eight galaxies with Zeeman detections suggest that the magnetic energy density in the interstellar medium of starburst galaxies is comparable to their hydrostatic gas pressure, as in the Milky Way. We discuss the significant uncertainties in this conclusion, and possible measurements that could reduce these uncertainties. We also compare the Zeeman splitting derived magnetic field estimates to magnetic field strengths estimated using synchrotron fluxes and assuming that the magnetic field and cosmic rays have comparable energy densities, known as the 'minimum energy' argument. We find that the minimum energy argument systematically underestimates magnetic fields in starburst galaxies, and that the conditions that would be required to produce agreement between the minimum energy estimate and the Zeeman derived estimate of interstellar medium magnetic fields are implausible. The conclusion that magnetic fields in starburst galaxies exceed the minimum energy magnetic fields is consistent with starburst galaxies adhering to the linearity of the far-infrared-radio correlation.

  10. Clumpy and Extended Starbursts in the Brightest Unlensed Submillimeter Galaxies

    NASA Astrophysics Data System (ADS)

    Iono, Daisuke; Yun, Min S.; Aretxaga, Itziar; Hatsukade, Bunyo; Hughes, David; Ikarashi, Soh; Izumi, Takuma; Kawabe, Ryohei; Kohno, Kotaro; Lee, Minju; Matsuda, Yuichi; Nakanishi, Kouichiro; Saito, Toshiki; Tamura, Yoichi; Ueda, Junko; Umehata, Hideki; Wilson, Grant; Michiyama, Tomonari; Ando, Misaki

    2016-09-01

    The central structure in three of the brightest unlensed z = 3-4 submillimeter galaxies is investigated through 0.″015-0.″05 (120-360 pc) 860 μm continuum images obtained using the Atacama Large Millimeter/submillimeter Array (ALMA). The distribution in the central kiloparsec in AzTEC1 and AzTEC8 is extremely complex, and they are composed of multiple ˜200 pc clumps. AzTEC4 consists of two sources that are separated by ˜1.5 kpc, indicating a mid-stage merger. The peak star formation rate densities in the central clumps are ˜300-3000 M ⊙ yr-1 kpc-2, suggesting regions with extreme star formation near the Eddington limit. By comparing the flux obtained by ALMA and Submillimeter Array, we find that 68%-90% of the emission is extended (≳1 kpc) in AzTEC4 and 8. For AzTEC1, we identify at least 11 additional compact (˜200 pc) clumps in the extended 3-4 kpc region. Overall, the data presented here suggest that the luminosity surface densities observed at ≲150 pc scales are roughly similar to that observed in local ULIRGs, as in the eastern nucleus of Arp 220. Between 10% and 30% of the 860 μm continuum is concentrated in clumpy structures in the central kiloparsec, while the remaining flux is distributed over ≳1 kpc regions, some of which could also be clumpy. These sources can be explained by a rapid inflow of gas such as a merger of gas-rich galaxies, surrounded by extended and clumpy starbursts. However, the cold mode accretion model is not ruled out.

  11. Local starburst galaxies and their descendants. Statistics from the Sloan Digital Sky Survey

    NASA Technical Reports Server (NTRS)

    Bergvall, Nils; Marquart, Thomas; Way, Michael J.; Blomqvist, Anna; Holst, Emma; Ostlin, Goran; Zackrisson, Erik

    2016-01-01

    Despite strong interest in the starburst phenomenon in extragalactic astronomy, the concept remains ill-defined. Here we use a strict definition of starburst to examine the statistical properties of starburst galaxies in the local universe. We also seek to establish links between starburst galaxies, post-starburst (hereafter postburst) galaxies, and active galaxies. Data were selected from the Sloan Digital Sky Survey DR7. We applied a novel method of treating dust attenuation and derive star formation rates, ages, and stellar masses assuming a two-component stellar population model. Dynamical masses are calculated from the width of the H-alpha line. These masses agree excellently with the photometric masses. The mass (gas+stars) range is approximately 10( exp 9) - 10(exp 11.5) solar mass. As a selection criterion for starburst galaxies, we use, the birthrate parameter, b = SFR/SFR, requiring that b is greater than 3. For postburst galaxies, we use, the equivalent width of Hdelta in absorption with the criterion EW (sub Hdelta_abs) is greater than 6 A. Results. We find that only 1% of star-forming galaxies are starburst galaxies. They contribute 3-6% to the stellar production and are therefore unimportant for the local star formation activity. The median starburst age is 70 Myr roughly independent of mass, indicating that star formation is mainly regulated by local feedback processes. The b-parameter strongly depends on burst age. Values close to b = 60 are found at ages approximately 10 Myr, while almost no starbursts are found at ages greater than 1 Gyr. The median baryonic burst mass fraction of sub-L galaxies is 5% and decreases slowly towards high masses. The median mass fraction of the recent burst in the postburst sample is 5-10%. A smaller fraction of the postburst galaxies, however, originates in non-bursting galaxies. The age-mass distribution of the postburst progenitors (with mass fractions is greater than 3%) is bimodal with a break at logM(solar mass

  12. Wolf-Rayet stars in nearby galaxies: facts and fancies.

    NASA Astrophysics Data System (ADS)

    Massey, P.; Armandroff, T. E.

    Surveys for Wolf-Rayet stars in nearby galaxies are briefly reviewed. The completeness and yield of these surveys are discussed in light of recent follow-up spectroscopy. A critical evaluation is made of our current knowledge of the Wolf-Rayet population in nearby galaxies, particularly the WC/WN ratio, the WR/O ratio, the WR surface density, and how these quantities vary within a galaxy and between galaxies, particularly as a function of metallicity. The authors compare the spectroscopic properties of Galactic and Magellanic Cloud WR stars with those in the more distant systems.

  13. Gas Chemistry in the Inner Disk of the Nearby Luminous Infrared Galaxy IRAS 04296+2923

    NASA Astrophysics Data System (ADS)

    Meier, David S.; Turner, J.

    2013-01-01

    Luminous infrared galaxies (LIRGs) represent the most active members of the starburst population in the nearby universe. In the closest LIRGs, for example IRAS 04296+2923 (D = 29 Mpc) located behind the Taurus Molecular Cloud, it is possible to image the intimate connection between dense gas and star formation directly. We present high resolution 3'') imaging of selected dense gas tracers, including 13CO, C18O, HCN, HCO+, HNC, CN, HNCO, and CH3OH, towards the nuclear starburst and inner disk of IRAS 04296+2923 compiled with the OVRO and CARMA millimeter interferometers. HCN, HCO+ and HNC are used to constrain the properties of the dense gas component. On nuclear scales we observe the same correlation between dense gas column and the star formation rate seen in earlier global surveys of LIRGs. HCN/CO, HCN/HCO+ and HCN/HNC line ratios suggest that both the dense gas fraction and density are high toward the starburst and fall non-monotonically with radius. CO isotopic line ratios in the inner disk are anomalous, having extremely low 13CO/C18O values. To explain these ratios very high gas opacities, anomalously low 13CO abundances or pronounced non-LTE effects must be invoked. The HCN/CN ratio is used to characterize the extent of photon-dominated regions (PDRs) across the inner disk. This ratio is large compared to starbursts like M 82 and NGC 253 suggesting the burst is still in a young, embedded phase. HNCO and CH3OH are use to trace large scale shocks in this barred galaxy. The chemical morphology of the large-scale bar is compared with nuclear bars in Maffei 2, NGC 6946 and IC 342. This work is supported by the National Science Foundation grant AST-1009620.

  14. THE ROLE OF MERGER STAGE ON GALAXY RADIO SPECTRA IN LOCAL INFRARED-BRIGHT STARBURST GALAXIES

    SciTech Connect

    Murphy, Eric J.

    2013-11-01

    An investigation of the steep, high-frequency (i.e., ν ∼ 12 GHz) radio spectra among a sample of 31 local infrared-bright starburst galaxies is carried out in light of their Hubble-Space-Telescope-based merger classifications. Radio data covering as many as 10 individual bands allow for spectral indices to be measured over three frequency bins between 0.15 and 32.5 GHz. Sources having the flattest spectral indices measured at ∼2 and 4 GHz, arising from large free-free optical depths among the densest starbursts, appear to be in ongoing through post-stage mergers. The spectral indices measured at higher frequencies (i.e., ∼12 GHz) are steepest for sources associated with ongoing mergers in which their nuclei are distinct, but share a common stellar envelope and/or exhibit tidal tails. These results hold after excluding potential active galactic nuclei based on their low 6.2 μm polycyclic aromatic hydrocarbon equivalent widths. Consequently, the low-, mid-, and high-frequency spectral indices each appear to be sensitive to the exact merger stage. It is additionally shown that ongoing mergers, whose progenitors are still separated and share a common envelope and/or exhibit tidal tails, also exhibit excess radio emission relative to what is expected given the far-infrared/radio correlation, suggesting that there may be a significant amount of radio emission that is not associated with ongoing star formation. The combination of these observations, along with high-resolution radio morphologies, leads to a picture in which the steep high-frequency radio spectral indices and excess radio emission arise from radio continuum bridges and tidal tails that are not associated with star formation, similar to what is observed for so-called 'taffy' galaxies. This scenario may also explain the seemingly low far-infrared/radio ratios measured for many high-z submillimeter galaxies, a number of which are merger-driven starbursts.

  15. A dust-obscured massive maximum-starburst galaxy at a redshift of 6.34.

    PubMed

    Riechers, Dominik A; Bradford, C M; Clements, D L; Dowell, C D; Pérez-Fournon, I; Ivison, R J; Bridge, C; Conley, A; Fu, Hai; Vieira, J D; Wardlow, J; Calanog, J; Cooray, A; Hurley, P; Neri, R; Kamenetzky, J; Aguirre, J E; Altieri, B; Arumugam, V; Benford, D J; Béthermin, M; Bock, J; Burgarella, D; Cabrera-Lavers, A; Chapman, S C; Cox, P; Dunlop, J S; Earle, L; Farrah, D; Ferrero, P; Franceschini, A; Gavazzi, R; Glenn, J; Solares, E A Gonzalez; Gurwell, M A; Halpern, M; Hatziminaoglou, E; Hyde, A; Ibar, E; Kovács, A; Krips, M; Lupu, R E; Maloney, P R; Martinez-Navajas, P; Matsuhara, H; Murphy, E J; Naylor, B J; Nguyen, H T; Oliver, S J; Omont, A; Page, M J; Petitpas, G; Rangwala, N; Roseboom, I G; Scott, D; Smith, A J; Staguhn, J G; Streblyanska, A; Thomson, A P; Valtchanov, I; Viero, M; Wang, L; Zemcov, M; Zmuidzinas, J

    2013-04-18

    Massive present-day early-type (elliptical and lenticular) galaxies probably gained the bulk of their stellar mass and heavy elements through intense, dust-enshrouded starbursts--that is, increased rates of star formation--in the most massive dark-matter haloes at early epochs. However, it remains unknown how soon after the Big Bang massive starburst progenitors exist. The measured redshift (z) distribution of dusty, massive starbursts has long been suspected to be biased low in z owing to selection effects, as confirmed by recent findings of systems with redshifts as high as ~5 (refs 2-4). Here we report the identification of a massive starburst galaxy at z = 6.34 through a submillimetre colour-selection technique. We unambiguously determined the redshift from a suite of molecular and atomic fine-structure cooling lines. These measurements reveal a hundred billion solar masses of highly excited, chemically evolved interstellar medium in this galaxy, which constitutes at least 40 per cent of the baryonic mass. A 'maximum starburst' converts the gas into stars at a rate more than 2,000 times that of the Milky Way, a rate among the highest observed at any epoch. Despite the overall downturn in cosmic star formation towards the highest redshifts, it seems that environments mature enough to form the most massive, intense starbursts existed at least as early as 880 million years after the Big Bang.

  16. A dust-obscured massive maximum-starburst galaxy at a redshift of 6.34.

    PubMed

    Riechers, Dominik A; Bradford, C M; Clements, D L; Dowell, C D; Pérez-Fournon, I; Ivison, R J; Bridge, C; Conley, A; Fu, Hai; Vieira, J D; Wardlow, J; Calanog, J; Cooray, A; Hurley, P; Neri, R; Kamenetzky, J; Aguirre, J E; Altieri, B; Arumugam, V; Benford, D J; Béthermin, M; Bock, J; Burgarella, D; Cabrera-Lavers, A; Chapman, S C; Cox, P; Dunlop, J S; Earle, L; Farrah, D; Ferrero, P; Franceschini, A; Gavazzi, R; Glenn, J; Solares, E A Gonzalez; Gurwell, M A; Halpern, M; Hatziminaoglou, E; Hyde, A; Ibar, E; Kovács, A; Krips, M; Lupu, R E; Maloney, P R; Martinez-Navajas, P; Matsuhara, H; Murphy, E J; Naylor, B J; Nguyen, H T; Oliver, S J; Omont, A; Page, M J; Petitpas, G; Rangwala, N; Roseboom, I G; Scott, D; Smith, A J; Staguhn, J G; Streblyanska, A; Thomson, A P; Valtchanov, I; Viero, M; Wang, L; Zemcov, M; Zmuidzinas, J

    2013-04-18

    Massive present-day early-type (elliptical and lenticular) galaxies probably gained the bulk of their stellar mass and heavy elements through intense, dust-enshrouded starbursts--that is, increased rates of star formation--in the most massive dark-matter haloes at early epochs. However, it remains unknown how soon after the Big Bang massive starburst progenitors exist. The measured redshift (z) distribution of dusty, massive starbursts has long been suspected to be biased low in z owing to selection effects, as confirmed by recent findings of systems with redshifts as high as ~5 (refs 2-4). Here we report the identification of a massive starburst galaxy at z = 6.34 through a submillimetre colour-selection technique. We unambiguously determined the redshift from a suite of molecular and atomic fine-structure cooling lines. These measurements reveal a hundred billion solar masses of highly excited, chemically evolved interstellar medium in this galaxy, which constitutes at least 40 per cent of the baryonic mass. A 'maximum starburst' converts the gas into stars at a rate more than 2,000 times that of the Milky Way, a rate among the highest observed at any epoch. Despite the overall downturn in cosmic star formation towards the highest redshifts, it seems that environments mature enough to form the most massive, intense starbursts existed at least as early as 880 million years after the Big Bang. PMID:23598341

  17. Cosmic-ray induced gamma-ray emission from the starburst galaxy NGC 253

    SciTech Connect

    Wang, Xilu; Fields, Brian D.

    2014-05-09

    Cosmic rays in galaxies interact with the interstellar medium and give us a direct view of nuclear and particle interactions in the cosmos. For example, cosmic-ray proton interactions with interstellar hydrogen produce gamma rays via PcrPism→π{sup 0}→γγ. For a 'normal' star-forming galaxy like the Milky Way, most cosmic rays escape the Galaxy before such collisions, but in starburst galaxies with dense gas and huge star formation rate, most cosmic rays do suffer these interactions [1,2]. We construct a 'thick-target' model for starburst galaxies, in which cosmic rays are accelerated by supernovae, and escape is neglected. This model gives an upper limit to the gamma-ray emission. Only two free parameters are involved in the model: cosmic-ray proton acceleration energy rate from supernova and the proton injection spectral index. The pionic gamma-radiation is calculated from 10 MeV to 10 TeV for the starburst galaxy NGC 253, and compared to Fermi and HESS data. Our model fits NGC 253 well, suggesting that cosmic rays in this starburst are in the thick target limit, and that this galaxy is a gamma-ray calorimeter.

  18. Cosmic-ray induced gamma-ray emission from the starburst galaxy NGC 253

    NASA Astrophysics Data System (ADS)

    Wang, Xilu; Fields, Brian D.

    2014-05-01

    Cosmic rays in galaxies interact with the interstellar medium and give us a direct view of nuclear and particle interactions in the cosmos. For example, cosmic-ray proton interactions with interstellar hydrogen produce gamma rays via PcrPism→π0→γγ. For a "normal" star-forming galaxy like the Milky Way, most cosmic rays escape the Galaxy before such collisions, but in starburst galaxies with dense gas and huge star formation rate, most cosmic rays do suffer these interactions [1,2]. We construct a "thick-target" model for starburst galaxies, in which cosmic rays are accelerated by supernovae, and escape is neglected. This model gives an upper limit to the gamma-ray emission. Only two free parameters are involved in the model: cosmic-ray proton acceleration energy rate from supernova and the proton injection spectral index. The pionic gamma-radiation is calculated from 10 MeV to 10 TeV for the starburst galaxy NGC 253, and compared to Fermi and HESS data. Our model fits NGC 253 well, suggesting that cosmic rays in this starburst are in the thick target limit, and that this galaxy is a gamma-ray calorimeter.

  19. HUBBLE SURVEYS DYING STARS IN NEARBY GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    From ground-based telescopes, the glowing gaseous debris surrounding dying, sun-like stars in a nearby galaxy, called the Large Magellanic Cloud, appear as small, shapeless dots of light. But through the 'eyes' of NASA's Hubble Space Telescope, these bright dots take on a variety of shapes, from round- to pinwheel-shaped clouds of gas. Using Hubble's Space Telescope Imaging Spectrograph, scientists probed the glowing gas surrounding 27 dying stars, called planetary nebulae, in the Large Magellanic Cloud. The observations represent the most detailed study of planetary nebulae outside the Milky Way. The six objects in the picture illustrate the assortment of planetary nebulae identified in the galaxy. SMP 16, 30, and 93 are examples of a bipolar nebula, twin lobes of gas projecting away from a dying star. SMP 10 has a pinwheel shape and is known as a 'point-symmetric' nebula. SMP 4 has an elliptical appearance, and SMP 27, consisting of four lobes of gas, is called a 'quadrupolar' nebula. The lines point to the objects' locations in the Large Magellanic Cloud. A ground-based observatory snapped the picture of this galaxy. In the pictures of the planetary nebulae, color corresponds to temperature. Blue represents hotter regions of the nebulae and red, cooler. Scientists are probing these illuminated stellar relics in our neighboring galaxy because they are at relatively the same distance - about 168,000 light-years -- from Earth. Knowing the distance to these objects allows scientists to compare their shapes and sizes, and precisely determine the brightness of their central stars. For this reason, even though these glowing remains of dying stars are about 50 times farther away than the stunning planetary nebulae photographed in the Milky Way, they are of invaluable importance. By sampling this population, scientists noticed that the bipolar nebulae are richer in some heavier elements, such as neon, than those with a more spherical shape. At the dawn of the universe

  20. HUBBLE SURVEYS DYING STARS IN NEARBY GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    From ground-based telescopes, the glowing gaseous debris surrounding dying, sun-like stars in a nearby galaxy, called the Large Magellanic Cloud, appear as small, shapeless dots of light. But through the 'eyes' of NASA's Hubble Space Telescope, these bright dots take on a variety of shapes, from round- to pinwheel-shaped clouds of gas. Using Hubble's Space Telescope Imaging Spectrograph, scientists probed the glowing gas surrounding 27 dying stars, called planetary nebulae, in the Large Magellanic Cloud. The observations represent the most detailed study of planetary nebulae outside the Milky Way. The six objects in the picture illustrate the assortment of planetary nebulae identified in the galaxy. SMP 16, 30, and 93 are examples of a bipolar nebula, twin lobes of gas projecting away from a dying star. SMP 10 has a pinwheel shape and is known as a 'point-symmetric' nebula. SMP 4 has an elliptical appearance, and SMP 27, consisting of four lobes of gas, is called a 'quadrupolar' nebula. The lines point to the objects' locations in the Large Magellanic Cloud. A ground-based observatory snapped the picture of this galaxy. In the pictures of the planetary nebulae, color corresponds to temperature. Blue represents hotter regions of the nebulae and red, cooler. Scientists are probing these illuminated stellar relics in our neighboring galaxy because they are at relatively the same distance - about 168,000 light-years -- from Earth. Knowing the distance to these objects allows scientists to compare their shapes and sizes, and precisely determine the brightness of their central stars. For this reason, even though these glowing remains of dying stars are about 50 times farther away than the stunning planetary nebulae photographed in the Milky Way, they are of invaluable importance. By sampling this population, scientists noticed that the bipolar nebulae are richer in some heavier elements, such as neon, than those with a more spherical shape. At the dawn of the universe

  1. Morphology and Structures of Nearby Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Seo, Mira; Ann, H. B.

    2016-08-01

    We applied GALFIT and STARLIGHT to the r-band images and spectra, respectively, of ~1,100 dwarf galaxies to analyze the structural properties and stellar populations. In most cases, single component with n = 1 ~ 1.5 well describes the luminosity distribution of dwarf galaxies. However, a large fraction of dS0, dE bc , and dE blue galaxies show sub-structures such as spiral arms and rings. There is a bimodal distributions of stellar ages in dS0 galaxies. But other sub-types of dwarf galaxies show a single peak in the stellar distributions.

  2. Galaxy Clustering Around Nearby Luminous Quasars

    NASA Technical Reports Server (NTRS)

    Fisher, Karl B.; Bahcall, John N.; Kirhakos, Sofia; Schneider, Donald P.

    1996-01-01

    We examine the clustering of galaxies around a sample of 20 luminous low redshift (z approx. less than 0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope (HST). The HST resolution makes possible galaxy identification brighter than V = 24.5 and as close as 1 min or 2 min to the quasar. We find a significant enhancement of galaxies within a projected separation of approx. less than 100 1/h kpc of the quasars. If we model the QSO/galaxy correlation function as a power law with a slope given by the galaxy/galaxy correlation function, we find that the ratio of the QSO/galaxy to galaxy/galaxy correlation functions is 3.8 +/- 0.8. The galaxy counts within r less than 15 1/h kpc of the quasars are too high for the density profile to have an appreciable core radius (approx. greater than 100 1/h kpc). Our results reinforce the idea that low redshift quasars are located preferentially in groups of 10-20 galaxies rather than in rich clusters. We see no significant difference in the clustering amplitudes derived from radio-loud and radio-quiet subsamples.

  3. HUBBLE'S ULTRAVIOLET VIEWS OF NEARBY GALAXIES YIELD CLUES TO EARLY UNIVERSE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers are using these three NASA Hubble Space Telescope images to help tackle the question of why distant galaxies have such odd shapes, appearing markedly different from the typical elliptical and spiral galaxies seen in the nearby universe. Do faraway galaxies look weird because they are truly weird? Or, are they actually normal galaxies that look like oddballs, because astronomers are getting an incomplete picture of them, seeing only the brightest pieces? Light from these galaxies travels great distances (billions of light-years) to reach Earth. During its journey, the light is 'stretched' due to the expansion of space. As a result, the light is no longer visible, but has been shifted to the infrared where present instruments are less sensitive. About the only light astronomers can see comes from regions where hot, young stars reside. These stars emit mostly ultraviolet light. But this light is stretched, appearing as visible light by the time it reaches Earth. Studying these distant galaxies is like trying to put together a puzzle with some of the pieces missing. What, then, do distant galaxies really look like? Astronomers studied 37 nearby galaxies to find out. By viewing these galaxies in ultraviolet light, astronomers can compare their shapes with those of their distant relatives. These three Hubble telescope pictures, taken with the Wide Field and Planetary Camera 2, represent a sampling from that survey. Astronomers observed the galaxies in ultraviolet and visible light to study all the stars that make up these 'cities of stars.' The results of their survey support the idea that astronomers are detecting the 'tip of the iceberg' of very distant galaxies. Based on these Hubble ultraviolet images, not all the faraway galaxies necessarily possess intrinsically odd shapes. The results are being presented today at the 197th meeting of the American Astronomical Society in San Diego, CA. The central region of the 'star-burst' spiral galaxy at far left

  4. MOLECULAR GAS AND STAR FORMATION IN NEARBY DISK GALAXIES

    SciTech Connect

    Leroy, Adam K.; Munoz-Mateos, Juan-Carlos; Walter, Fabian; Sandstrom, Karin; Meidt, Sharon; Rix, Hans-Walter; Schinnerer, Eva; Schruba, Andreas; Bigiel, Frank; Bolatto, Alberto; Brinks, Elias; De Blok, W. J. G.; Rosolowsky, Erik; Schuster, Karl-Friedrich; Usero, Antonio

    2013-08-01

    We compare molecular gas traced by {sup 12}CO (2-1) maps from the HERACLES survey, with tracers of the recent star formation rate (SFR) across 30 nearby disk galaxies. We demonstrate a first-order linear correspondence between {Sigma}{sub mol} and {Sigma}{sub SFR} but also find important second-order systematic variations in the apparent molecular gas depletion time, {tau}{sub dep}{sup mol}={Sigma}{sub mol}/{Sigma}{sub SFR}. At the 1 kpc common resolution of HERACLES, CO emission correlates closely with many tracers of the recent SFR. Weighting each line of sight equally, using a fixed {alpha}{sub CO} equivalent to the Milky Way value, our data yield a molecular gas depletion time, {tau}{sub dep}{sup mol}={Sigma}{sub mol}/{Sigma}{sub SFR}{approx}2.2 Gyr with 0.3 dex 1{sigma} scatter, in very good agreement with recent literature data. We apply a forward-modeling approach to constrain the power-law index, N, that relates the SFR surface density and the molecular gas surface density, {Sigma}{sub SFR}{proportional_to}{Sigma}{sub mol}{sup N}. We find N = 1 {+-} 0.15 for our full data set with some scatter from galaxy to galaxy. This also agrees with recent work, but we caution that a power-law treatment oversimplifies the topic given that we observe correlations between {tau}{sub dep}{sup mol} and other local and global quantities. The strongest of these are a decreased {tau}{sub dep}{sup mol} in low-mass, low-metallicity galaxies and a correlation of the kpc-scale {tau}{sub dep}{sup mol} with dust-to-gas ratio, D/G. These correlations can be explained by a CO-to-H{sub 2} conversion factor ({alpha}{sub CO}) that depends on dust shielding, and thus D/G, in the theoretically expected way. This is not a unique interpretation, but external evidence of conversion factor variations makes this the most conservative explanation of the strongest observed {tau}{sub dep}{sup mol} trends. After applying a D/G-dependent {alpha}{sub CO}, some weak correlations between {tau}{sub dep

  5. A Survey of nearby, nearly face-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Garmire, Gordon

    2014-09-01

    This is a continuation of a survey of nearby, nearly face-on spiral galaxies. The main purpose is to search for evidence of collisions with small galaxies that show up in X-rays by the generation of hot shocked gas from the collision. Secondary objectives include study of the spatial distribution point sources in the galaxy and to detect evidence for a central massive blackhole. These are alternate targets.

  6. A Survey of nearby, nearly face-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Garmire, Gordon

    2014-09-01

    This is a continuation of a survey of nearby, nearly face-on spiral galaxies. The main purpose is to search for evidence of collisions with small galaxies that show up in X-rays by the generation of hot shocked gas from the collision. Secondary objectives include study of the spatial distribution point sources in the galaxy and to detect evidence for a central massive blackhole.

  7. Resolving the Chemistry of Molecular Gas that Fuels Luminous Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Meier, David; Turner, Jean; Anderson, Crystal

    2012-10-01

    Energy input from massive stars profoundly impact on how starburst galaxies evolve. Both the triggers of and feedback from star formation manifest themselves in the gas chemistry. We use millimeter interferometry to obtain high spatial resolution maps of CO, HCO^+, CCH, NNH^+, HNCO, CH3OH and SiO, toward the starbursts, Maffei 2, M 82, IRAS 04296+2923 and Arp 220. Dramatic variations in gas chemistry are observed both within the individual galaxies and from galaxy to galaxy. These variations correlate with star formation and gas dynamics. CO isotopologues are used to constrain the evolutionary history of star formation. Species preferentially formed (CCH) and destroyed (NNH^+) in the presence of strong UV radiation map out where energy input from the massive stars dominate. CCH abundances are correlated with star formation rate, except in the most extreme starburst, Arp 220, whereas NNH^+ abundances drop, except for Arp 220. The abundance anomalies in Arp 220 hint that the molecular medium in the most extreme starbursts is different. HNCO, CH3OH and SiO locate shocks due to bars and galaxy-galaxy mergers in these systems. Comparisons between these species suggest shock strength does not change across bars, but does for merger remnants.

  8. THE JAMES CLERK MAXWELL TELESCOPE NEARBY GALAXIES LEGACY SURVEY. II. WARM MOLECULAR GAS AND STAR FORMATION IN THREE FIELD SPIRAL GALAXIES

    SciTech Connect

    Warren, B. E.; Wilson, C. D.; Sinukoff, E.; Israel, F. P.; Van der Werf, P. P.; Serjeant, S.; Bendo, G. J.; Clements, D. L.; Brinks, E.; Irwin, J. A.; Knapen, J. H.; Leech, J.; Tan, B. K.; Matthews, H. E.; Muehle, S.; Mortimer, A. M. J.; Petitpas, G.; Spekkens, K.; Tilanus, R. P. J.; Usero, A. E-mail: wilson@physics.mcmaster.c E-mail: israel@strw.leidenuniv.n

    2010-05-01

    We present the results of large-area {sup 12}CO J = 3-2 emission mapping of three nearby field galaxies, NGC 628, NGC 3521, and NGC 3627, completed at the James Clerk Maxwell Telescope as part of the Nearby Galaxies Legacy Survey. These galaxies all have moderate to strong {sup 12}CO J = 3-2 detections over large areas of the fields observed by the survey, showing resolved structure and dynamics in their warm/dense molecular gas disks. All three galaxies were part of the Spitzer Infrared Nearby Galaxies Survey sample, and as such have excellent published multiwavelength ancillary data. These data sets allow us to examine the star formation properties, gas content, and dynamics of these galaxies on sub-kiloparsec scales. We find that the global gas depletion time for dense/warm molecular gas in these galaxies is consistent with other results for nearby spiral galaxies, indicating this may be independent of galaxy properties such as structures, gas compositions, and environments. Similar to the results from The H I Nearby Galaxy Survey, we do not see a correlation of the star formation efficiency with the gas surface density consistent with the Schmidt-Kennicutt law. Finally, we find that the star formation efficiency of the dense molecular gas traced by {sup 12}CO J = 3-2 is potentially flat or slightly declining as a function of molecular gas density, the {sup 12}CO J = 3-2/J = 1-0 ratio (in contrast to the correlation found in a previous study into the starburst galaxy M83), and the fraction of total gas in molecular form.

  9. CS (5-4) survey towards nearby infrared bright galaxies

    NASA Astrophysics Data System (ADS)

    Wang, Junzhi; Zhang, Zhiyu; Shi, Yong

    2011-09-01

    With the observations of the CS (5-4) line towards a sample of 24 infrared bright galaxies using Heinrich Hertz Submillimeter Telescope (HHSMT), we detected CS (5-4) emission in 14 galaxies, including 12 ultraluminous infrared galaxies (ULIRGs)/luminous infrared galaxies (LIRGs) and two nearby normal galaxies. As a good dense gas tracer, which has been well used for studying star formation in the Milky Way, CS (5-4) can trace the active star-forming gas in galaxies. The correlation between CS (5-4) luminosity, which is estimated with detected CS (5-4) line emission, and the infrared luminosity in these 14 galaxies, is fitted with a correlation coefficient of 0.939 and a slope close to unity. This correlation confirms that dense gas, which is closely linked to star formation, is very important for understanding star formation in galaxies.

  10. AN UPDATED ULTRAVIOLET CATALOG OF GALEX NEARBY GALAXIES

    SciTech Connect

    Bai, Yu; Zou, Hu; Liu, JiFeng; Wang, Song E-mail: zouhu@nao.cas.cn E-mail: songw@nao.cas.cn

    2015-09-15

    The ultraviolet (UV) catalog of nearby galaxies compiled by Gil de Paz et al. presents the integrated photometry and surface brightness profiles for 1034 nearby galaxies observed by GALEX. We provide an updated catalog of 4138 nearby galaxies based on the latest Genral Release (GR6/GR7) of GALEX. These galaxies are selected from HyperLeda with apparent diameters larger than 1′. From the surface brightness profiles accurately measured using the deep NUV and FUV images, we have calculated the asymptotic magnitudes, aperture (D25) magnitudes, colors, structural parameters (effective radii and concentration indices), luminosities, and effective surface brightness for these galaxies. Archival optical and infrared photometry from HyperLeda, 2MASS, and IRAS are also integrated into the catalog. Our parameter measurements and some analyses are consistent with those of Paz et al. The (FUV − K) color provides a good criterion to distinguish between early- and late-type galaxies, which can be improved further using the concentration indices. The IRX–β relation is reformulated with our UV-selected nearby galaxies.

  11. An Updated Ultraviolet Catalog of GALEX Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Bai, Yu; Zou, Hu; Liu, JiFeng; Wang, Song

    2015-09-01

    The ultraviolet (UV) catalog of nearby galaxies compiled by Gil de Paz et al. presents the integrated photometry and surface brightness profiles for 1034 nearby galaxies observed by GALEX. We provide an updated catalog of 4138 nearby galaxies based on the latest Genral Release (GR6/GR7) of GALEX. These galaxies are selected from HyperLeda with apparent diameters larger than 1‧. From the surface brightness profiles accurately measured using the deep NUV and FUV images, we have calculated the asymptotic magnitudes, aperture (D25) magnitudes, colors, structural parameters (effective radii and concentration indices), luminosities, and effective surface brightness for these galaxies. Archival optical and infrared photometry from HyperLeda, 2MASS, and IRAS are also integrated into the catalog. Our parameter measurements and some analyses are consistent with those of Paz et al. The (FUV - K) color provides a good criterion to distinguish between early- and late-type galaxies, which can be improved further using the concentration indices. The IRX-β relation is reformulated with our UV-selected nearby galaxies.

  12. Direct Detection of Lyman Continuum Escape from Local Starburst Galaxies with the Cosmic Origins Spectrograph

    NASA Astrophysics Data System (ADS)

    Leitherer, Claus; Hernandez, Svea; Lee, Janice C.; Oey, M. S.

    2016-05-01

    We report on the detection of Lyman continuum radiation in two nearby starburst galaxies. Tol 0440-381, Tol 1247-232, and Mrk 54 were observed with the Cosmic Origins Spectrograph on board the Hubble Space Telescope. The three galaxies have radial velocities of ˜13,000 km s‑1, permitting a ˜35 Å window on the restframe Lyman continuum shortward of the Milky Way Lyman edge at 912 Å. The chosen instrument configuration using the G140L grating covers the spectral range from 912 to 2000 Å. We developed a dedicated background subtraction method to account for the temporal and spatial background variations of the detector, which is crucial at the low flux levels around 912 Å. This modified pipeline allowed us to significantly improve the statistical and systematic detector noise and will be made available to the community. We detect Lyman continuum in all three galaxies. However, we conservatively interpret the emission in Tol 0440-381 as an upper limit due to possible contamination by geocoronal Lyman series lines. We determined the current star formation properties from the far-ultraviolet continuum and spectral lines and used synthesis models to predict the Lyman continuum radiation emitted by the current population of hot stars. We discuss various model uncertainties such as, among others, atmospheres and evolution models. Lyman continuum escape fractions were derived from a comparison between the observed and predicted Lyman continuum fluxes. Tol 1247-232, Mrk 54, and Tol 0440-381 have absolute escape fractions of (4.5 ± 1.2)%, (2.5 ± 0.72)%, and <(7.1 ± 1.1)%, respectively.

  13. Confirming the First Supermassive Black Hole in a Dwarf Starburst Galaxy

    NASA Astrophysics Data System (ADS)

    Reines, Amy

    2011-10-01

    In the modern universe, supermassive black holes lie at the heart of most, if not all, galaxies with bulges. However, the birth and growth of the first "seed" black holes, back in the earlier universe, is observationally unconstrained. Reines et al. {2011} have recently discovered a candidate million-solar mass black hole in the bulgeless dwarf starburst galaxy Henize 2-10, offering the first opportunity to study a growing black hole in a nearby galaxy much like those in the infant universe. The case for an accreting black hole in Henize 2-10 is strong {e.g. co-spatial non-thermal radio and hard X-ray point sources}, but not watertight. Our proposal aims to confirm {or refute} the presence of this candidate black hole using STIS optical spectroscopy to trace the kinematics and ionization conditions in its immediate vicinity. Existing HST observations show a marginally resolved H-alpha knot coincident with the radio and X-ray point source, so our primary aim is to detect a compact rotating disk of ionized gas, directly yielding a black hole mass. Our secondary aim is to find evidence for AGN-related emission line signatures at the location of the H-alpha knot, and possibly along a narrow jet-like filament. Confirming the presence of a supermassive black hole in Henize 2-10 with these HST observations has immediate implications for our understanding of the birth and early evolution of the first black holes in the high-redshift universe.

  14. Direct Detection of Lyman Continuum Escape from Local Starburst Galaxies with the Cosmic Origins Spectrograph

    NASA Astrophysics Data System (ADS)

    Leitherer, Claus; Hernandez, Svea; Lee, Janice C.; Oey, M. S.

    2016-05-01

    We report on the detection of Lyman continuum radiation in two nearby starburst galaxies. Tol 0440-381, Tol 1247-232, and Mrk 54 were observed with the Cosmic Origins Spectrograph on board the Hubble Space Telescope. The three galaxies have radial velocities of ˜13,000 km s-1, permitting a ˜35 Å window on the restframe Lyman continuum shortward of the Milky Way Lyman edge at 912 Å. The chosen instrument configuration using the G140L grating covers the spectral range from 912 to 2000 Å. We developed a dedicated background subtraction method to account for the temporal and spatial background variations of the detector, which is crucial at the low flux levels around 912 Å. This modified pipeline allowed us to significantly improve the statistical and systematic detector noise and will be made available to the community. We detect Lyman continuum in all three galaxies. However, we conservatively interpret the emission in Tol 0440-381 as an upper limit due to possible contamination by geocoronal Lyman series lines. We determined the current star formation properties from the far-ultraviolet continuum and spectral lines and used synthesis models to predict the Lyman continuum radiation emitted by the current population of hot stars. We discuss various model uncertainties such as, among others, atmospheres and evolution models. Lyman continuum escape fractions were derived from a comparison between the observed and predicted Lyman continuum fluxes. Tol 1247-232, Mrk 54, and Tol 0440-381 have absolute escape fractions of (4.5 ± 1.2)%, (2.5 ± 0.72)%, and <(7.1 ± 1.1)%, respectively.

  15. Superdense Massive Galaxies in the Nearby Universe

    NASA Astrophysics Data System (ADS)

    Trujillo, Ignacio; Cenarro, A. Javier; de Lorenzo-Cáceres, Adriana; Vazdekis, Alexandre; de la Rosa, Ignacio G.; Cava, Antonio

    2009-02-01

    Superdense massive galaxies (re ~ 1 kpc; M ~ 1011 M sun) were common in the early universe (z gsim 1.5). Within some hierarchical merging scenarios, a non-negligible fraction (1%-10%) of these galaxies is expected to survive since that epoch, retaining their compactness and presenting old stellar populations in the present universe. Using the NYU Value-Added Galaxy Catalog from the Sloan Digital Sky Survey Data Release 6, we find only a tiny fraction of galaxies (~0.03%) with re lsim 1.5 kpc and M sstarf gsim 8 × 1010 M sun in the local universe (z < 0.2). Surprisingly, they are relatively young (~2 Gyr) and metal-rich ([Z/H] ~0.2). The consequences of these findings within the current two competing size evolution scenarios for the most massive galaxies ("dry" mergers vs. "puffing up" due to quasar activity) are discussed.

  16. The CLU Nearby Galaxy Catalog: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Cook, David O.; Kasliwal, Mansi M.; iPTF

    2016-01-01

    The intermediate Palomar Transient Factory (iPTF) has been undertaking the Census of the Local Universe (CLU) project to complete our survey of galaxies out to 200 Mpc. CLU deploys four contiguous narrow-band filters to search for extended, emission line (Hα) sources across 3π of the sky. The estimated 5σ limiting flux for a point source is 2×10-17 erg s-1 cm-2 (Rau et al., 2009), which corresponds to a star formation rate (SFR) of 10-3 M⊙ yr-1 at a distance of 200 Mpc. Thus, the CLU galaxy catalog will capture 85% of the B-band light and 92% of the Hα luminosity out to 200 Mpc resulting in tens-of-thousands of newly discovered galaxies. We present the narrowband imaging characteristics, the criteria used for selecting galaxy candidates, and a sub-set of newly discovered galaxies that have been spectroscopically confirmed.

  17. EXTREME EMISSION-LINE GALAXIES IN CANDELS: BROADBAND-SELECTED, STARBURSTING DWARF GALAXIES AT z > 1

    SciTech Connect

    Van der Wel, A.; Rix, H.-W.; Jahnke, K.; Straughn, A. N.; Finkelstein, S. L.; Salmon, B. W.; Koekemoer, A. M.; Ferguson, H. C.; Weiner, B. J.; Wuyts, S.; Bell, E. F.; Faber, S. M.; Trump, J. R.; Koo, D. C.; Hathi, N. P.; Dunlop, J. S.; Newman, J. A.; Dickinson, M.; De Mello, D. F.; and others

    2011-12-01

    We identify an abundant population of extreme emission-line galaxies (EELGs) at redshift z {approx} 1.7 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). Sixty-nine EELG candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared broadband magnitudes. Supported by spectroscopic confirmation of strong [O III] emission lines-with rest-frame equivalent widths {approx}1000 A-in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are galaxies with {approx}10{sup 8} M{sub Sun} in stellar mass, undergoing an enormous starburst phase with M{sub *}/ M-dot{sub *} of only {approx}15 Myr. These bursts may cause outflows that are strong enough to produce cored dark matter profiles in low-mass galaxies. The individual star formation rates and the comoving number density (3.7 Multiplication-Sign 10{sup -4} Mpc{sup -3}) can produce in {approx}4 Gyr much of the stellar mass density that is presently contained in 10{sup 8}-10{sup 9} M{sub Sun} dwarf galaxies. Therefore, our observations provide a strong indication that many or even most of the stars in present-day dwarf galaxies formed in strong, short-lived bursts, mostly at z > 1.

  18. Distributions of molecules in the circumnuclear disk and surrounding starburst ring in the Seyfert galaxy NGC 1068 observed with ALMA

    NASA Astrophysics Data System (ADS)

    Takano, Shuro; Nakajima, Taku; Kohno, Kotaro; Harada, Nanase; Herbst, Eric; Tamura, Yoichi; Izumi, Takuma; Taniguchi, Akio; Tosaki, Tomoka

    2014-07-01

    Sensitive observations with the Atacama Large Millimeter/submillimeter Array (ALMA) allow astronomers to observe the detailed distributions of molecules with relatively weak intensity in nearby galaxies. In particular, we report distributions of several molecular transitions including shock and dust related species (13CO J = 1-0, C18O J = 1-0, 13CN N = 1-0, CS J = 2-1, SO JN = 32-21, HNCO JKa,Kc = 50,5-40,4, HC3N J = 11-10, 12-11, CH3OH JK = 2K-1K, and CH3CN JK = 6K-5K) in the nearby Seyfert 2 galaxy NGC 1068 observed with the ALMA early science program. The central ˜ 1'(˜ 4.3 kpc) of this galaxy was observed in the 100-GHz region covering ˜ 96-100 GHz and ˜ 108-111 GHz with an angular resolution of ˜ 4'' × 2'' (290 pc × 140 pc) to study the effects of an active galactic nucleus and its surrounding starburst ring on molecular abundances. Here, we present images and report a classification of molecular distributions into three main categories: (1) molecules concentrated in the circumnuclear disk (CND) (SO JN = 32-21, HC3N J = 11-10, 12-11, and CH3CN JK = 6K-5K), (2) molecules distributed both in the CND and the starburst ring (CS J = 2-1 and CH3OH JK = 2K-1K), and (3) molecules distributed mainly in the starburst ring (13CO J = 1-0 and C18O J = 1-0). Since most of the molecules such as HC3N observed in the CND are easily dissociated by UV photons and X-rays, our results indicate that these molecules must be effectively shielded. In the starburst ring, the relative intensity of methanol at each clumpy region is not consistent with those of 13CO, C18O, or CS. This difference is probably caused by the unique formation and destruction mechanisms of CH3OH.

  19. Resolved photometry of young massive clusters in the starburst galaxy NGC 4214

    NASA Astrophysics Data System (ADS)

    Sollima, A.; Cignoni, M.; Gratton, R. G.; Tosi, M.; Bragaglia, A.; Lucatello, S.; Meurer, G.

    2014-01-01

    We present the results of deep high-resolution imaging performed with Advanced Camera for Surveys (ACS)/HRC@HST in the most active region of the nearby starburst galaxy NGC 4214. We resolved the stellar populations of five young massive clusters and their surrounding galactic field. The star formation history of this region is characterized by two main bursts occurred within the last 500 Myr, with the oldest episode spread out across an area larger than that covered by the most recent one. The ages derived for the analysed clusters cover a wide range within 6.4 < log t/yr < 8.1 in agreement with those predicted by recent analyses based on integrated photometry. The comparison between the mass of the young associations and that of the surrounding field population with similar ages indicates a high cluster formation efficiency (Γ ˜ 33 per cent) which decreases when old populations are considered. The mass function of the major assembly has been found to be slightly flatter than the Salpeter law with a hint of mass segregation. We found no clear signatures of multiple stellar populations in the two young (log t/yr < 6.8) associations where we were able to resolve their innermost region. The masses and sizes of three clusters indicate that at least one of them could evolve towards a globular cluster-like structure.

  20. Just-After THE FALL: Post-Starburst Galaxies and the E+B Phase

    NASA Astrophysics Data System (ADS)

    Smercina, Adam; Tremonti, Christina A.; Chisholm, John P.

    2015-01-01

    A key question in galaxy evolution is how star formation is quenched. Post-starburst galaxies, which can be identified by their distinctive optical spectra, are excellent laboratories for studying various quenching processes. However, canonical post-starbursts, called E+A's or K+A's, are several 100 Myr past the epoch of active quenching, making it challenging to measure quenching timescales and make inferences about the processes at work. To address this problem, we have identified a sample of 23 young, B-star dominated post-starbursts (E+B's) at z = 0.45 - 0.82 in SDSS-III's Baryon Oscillation Spectroscopic Survey (BOSS). In this new class of objects, we determine how abruptly star formation is truncated and probe the role of various possible feedback mechanisms.This work was supported by the National Science Foundation's REU program through NSF Award AST-1004881.

  1. Distribution of Molecules in the Circumnuclear Disk and Surrounding Starburst Ring in the Seyfert Galaxy NGC 1068 Observed with ALMA

    NASA Astrophysics Data System (ADS)

    Takano, S.; Nakajima, T.; Kohno, K.; Harada, N.; Herbst, E.; Tamura, Y.; Izumi, T.; Taniguchi, A.; Tosaki, T.

    2015-12-01

    We report distributions of several molecular transitions including shock and dust related species (13CO and C18O J = 1-0, 13CN N = 1-0, CS J = 2-1, SO JN = 32-21, HNCO JKa,Kc = 50,5-40,4, HC3N J = 11-10, 12-11, CH3OH JK = 2K-1K, and CH3CN JK = 6K-5K) in the nearby Seyfert 2 galaxy NGC 1068 observed with ALMA. The central ˜1' (˜4.3 kpc) of this galaxy was observed in the 100 GHz region with an angular resolution of ˜4" x 2" (290 pc x 140 pc) to study the effects of an active galactic nucleus and its surrounding starburst ring on molecular abundances. We report a classification of molecular distributions into three main categories. Organic molecules such as CH3CN are found to be concentrated in the circumnuclear disk. In the starburst ring, the intensity of methanol at each clumpy region is not consistent with that of 13CO.

  2. NEARBY GALAXIES IN MORE DISTANT CONTEXTS

    SciTech Connect

    Eskew, Michael; Zaritsky, Dennis E-mail: dzaritsky@as.arizona.edu

    2011-02-15

    We use published reconstructions of the star formation history (SFH) of the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and NGC 300 from the analysis of resolved stellar populations to investigate where such galaxies might land on well-known extragalactic diagnostic plots over the galaxies' lifetime (assuming that nothing other than their stellar populations change). For example, we find that the evolution of these galaxies implies a complex evolution in the Tully-Fisher relation with look-back time and that the observed scatter is consistent with excursions these galaxies take as their stellar populations evolve. We find that the growth of stellar mass is weighted to early times, despite the strongly star-forming current nature of the three systems. Lastly, we find that these galaxies can take circuitous paths across the color-magnitude diagram. For example, it is possible, within the constraints provided by the current determination of its SFH, that the LMC reached the red sequence at intermediate age prior to ending back up on the blue cloud at the current time. Unfortunately, this behavior happens at sufficiently early times that our resolved SFH is crude and insufficiently constraining to convincingly demonstrate that this was the actual evolutionary path. The limited sample size precludes any general conclusions, but we present these as examples how we can bridge the study of resolved populations and the more distant universe.

  3. Hydrogen fluoride toward luminous nearby galaxies: NGC 253 and NGC 4945

    SciTech Connect

    Monje, R. R.; Lis, D. C.; Phillips, T. G.; Lord, S.; Falgarone, E.; Güsten, R.

    2014-04-10

    We present the detection of hydrogen fluoride (HF) in two luminous nearby galaxies, NGC 253 and NGC 4945 using the Heterodyne Instrument for the Far-Infrared on board the Herschel Space Observatory. The HF line toward NGC 253 has a P-Cygni profile, while an asymmetric absorption profile is seen toward NGC 4945. The P-Cygni profile in NGC 253 suggests an outflow of molecular gas with a mass of M(H{sub 2}){sub out} ∼ 1 × 10{sup 7} M {sub ☉} and an outflow rate as large as M-dot ∼6.4 M {sub ☉} yr{sup –1}. In the case of NGC 4945, the axisymmetric velocity components in the HF line profile are compatible with the interpretation of a fast-rotating nuclear ring surrounding the nucleus and the presence of inflowing gas. The gas falls into the nucleus with an inflow rate of ≤1.2 M {sub ☉} yr{sup –1}, inside an inner radius of ≤200 pc. The gas accretion rate to the central active galactic nucleus is much smaller, suggesting that the inflow may be triggering a nuclear starburst. From these results, the HF J = 1-0 line is seen to provide an important probe of the kinematics of absorbing material along the sight-line to nearby galaxies with bright dust continuum and a promising new tracer of molecular gas in high-redshift galaxies.

  4. Hydrogen Fluoride toward Luminous Nearby Galaxies: NGC 253 and NGC 4945

    NASA Astrophysics Data System (ADS)

    Monje, R. R.; Lord, S.; Falgarone, E.; Lis, D. C.; Neufeld, D. A.; Phillips, T. G.; Güsten, R.

    2014-04-01

    We present the detection of hydrogen fluoride (HF) in two luminous nearby galaxies, NGC 253 and NGC 4945 using the Heterodyne Instrument for the Far-Infrared on board the Herschel Space Observatory. The HF line toward NGC 253 has a P-Cygni profile, while an asymmetric absorption profile is seen toward NGC 4945. The P-Cygni profile in NGC 253 suggests an outflow of molecular gas with a mass of M(H2)out ~ 1 × 107 M ⊙ and an outflow rate as large as dot M ~6.4 M ⊙ yr-1. In the case of NGC 4945, the axisymmetric velocity components in the HF line profile are compatible with the interpretation of a fast-rotating nuclear ring surrounding the nucleus and the presence of inflowing gas. The gas falls into the nucleus with an inflow rate of <=1.2 M ⊙ yr-1, inside an inner radius of <=200 pc. The gas accretion rate to the central active galactic nucleus is much smaller, suggesting that the inflow may be triggering a nuclear starburst. From these results, the HF J = 1-0 line is seen to provide an important probe of the kinematics of absorbing material along the sight-line to nearby galaxies with bright dust continuum and a promising new tracer of molecular gas in high-redshift galaxies.

  5. SHAKEN, NOT STIRRED: THE DISRUPTED DISK OF THE STARBURST GALAXY NGC 253

    SciTech Connect

    Davidge, T. J.

    2010-12-10

    Near-infrared images obtained with WIRCam on the Canada-France-Hawaii Telescope are used to investigate the recent history of the nearby Sculptor Group spiral NGC 253, which is one of the nearest starburst galaxies. Bright asymptotic giant branch (AGB) stars are traced out to projected distances of {approx}22-26 kpc ({approx}13-15 disk scale lengths) along the major axis. The distribution of stars in the disk is lopsided, in the sense that the projected density of AGB stars in the northeast portion of the disk between 10 and 20 kpc from the galaxy center is {approx}0.5 dex higher than on the opposite side of the galaxy. A large population of red supergiants is also found in the northeast portion of the disk and, with the exception of the central 2 kpc, this area appears to have been the site of the highest levels of star-forming activity in the galaxy during the past {approx}0.1 Gyr. It is argued that such high levels of localized star formation may have produced a fountain that ejected material from the disk, and the extraplanar H I detected by Boomsma et al. may be one manifestation of such activity. Diffuse stellar structures are found in the periphery of the disk, and the most prominent of these is to the south and east of the galaxy. Bright AGB stars, including cool C stars that are identified based on their J - K colors, are detected out to 15 kpc above the disk plane, and these are part of a diffusely distributed, flattened extraplanar component. Comparisons between observed and model luminosity functions suggest that the extraplanar regions contain stars that formed throughout much of the age of the universe. Additional evidence of a diffuse, extraplanar stellar component that contains moderately young stars comes from archival Galaxy Evolution Explorer images. It is suggested that the disk of NGC 253 was disrupted by a tidal encounter with a now defunct companion. This encounter introduced asymmetries that remain to this day, and the projected distribution

  6. ALFALFA Discovery of the nearby Gas-rich Dwarf Galaxy Leo P. III. An Extremely Metal Deficient Galaxy

    NASA Astrophysics Data System (ADS)

    Skillman, Evan D.; Salzer, John J.; Berg, Danielle A.; Pogge, Richard W.; Haurberg, Nathalie C.; Cannon, John M.; Aver, Erik; Olive, Keith A.; Giovanelli, Riccardo; Haynes, Martha P.; Adams, Elizabeth A. K.; McQuinn, Kristen B. W.; Rhode, Katherine L.

    2013-07-01

    We present KPNO 4 m and LBT/MODS spectroscopic observations of an H II region in the nearby dwarf irregular galaxy Leo P discovered recently in the Arecibo ALFALFA survey. In both observations, we are able to accurately measure the temperature sensitive [O III] λ4363 line and determine a "direct" oxygen abundance of 12 + log(O/H) = 7.17 ± 0.04. Thus, Leo P is an extremely metal deficient (XMD) galaxy, and, indeed, one of the most metal deficient star-forming galaxies ever observed. For its estimated luminosity, Leo P is consistent with the relationship between luminosity and oxygen abundance seen in nearby dwarf galaxies. Leo P shows normal α element abundance ratios (Ne/O, S/O, and Ar/O) when compared to other XMD galaxies, but elevated N/O, consistent with the "delayed release" hypothesis for N/O abundances. We derive a helium mass fraction of 0.2509^{+0.0184}_{-0.0123}, which compares well with the WMAP + BBN prediction of 0.2483 ± 0.0002 for the primordial helium abundance. We suggest that surveys of very low mass galaxies compete well with emission line galaxy surveys for finding XMD galaxies. It is possible that XMD galaxies may be divided into two classes: the relatively rare XMD emission line galaxies which are associated with starbursts triggered by infall of low-metallicity gas and the more common, relatively quiescent XMD galaxies like Leo P, with very low chemical abundances due to their intrinsically small masses. Some of the observations reported here were obtained at the LBT Observatory. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The

  7. Obscured starbursts in galaxy clusters: a MIPS survey of z=0.5 clusters

    NASA Astrophysics Data System (ADS)

    Smail, Ian; Ebeling, Harald; Edge, Alastair; Geach, Jim; Ma, Cheng-Jiun; Wardlow, Julie

    2008-03-01

    We propose panoramic MIPS 24um imaging of four intermediate redshift (z~0.5) clusters selected from the MACS X-ray Survey. We will combine these with observations of four clusters at the same epoch from our pilot study (which span a broader range in mass) to parameterize the evolutionary sequence of infalling field galaxies in terms of the cluster global structure. This analysis will distinguish between the role of global and local environment in determining the star formation histories of starburst galaxies entering the cluster potential from the low-density field. Our previous successful MIPS project has yielded some exciting results - in particular the existence of large populations of starburst galaxies in z~0.5 clusters with strong PAH emission - which have been completely overlooked by previous optical/near-IR surveys of these well-studied systems. These are potentially the missing link between distant spirals and the local passive S0 galaxies which are the dominant population in local clusters. Our initial results point to a strong dependence of star formation on specific cluster properties - either the dynamical state or the cluster mass (or equivalently temperature of the ICM). By specifically targeting four clusters with a narrow range in mass, but a wide range of structures, we aim to determine the key drivers of the variation in the starburst population within clusters. This will provide vital clues as to the physics of environmental transformations of galaxies: an important ingredient of current galaxy evolution models.

  8. High velocity clouds in nearby disk galaxies

    NASA Technical Reports Server (NTRS)

    Schulman, Eric; Bregman, Joel N.; Roberts, Morton S.; Brinks, Elias

    1993-01-01

    Clouds of neutral hydrogen in our galaxy with the absolute value of v greater than 100 km/s cover approximately 10 percent of the sky to a limiting column density of 1 x 10(exp 18) cm(exp -2). These high velocity clouds (HVCs) may dominate the kinetic energy of neutral hydrogen in non-circular motion, and are an important though poorly understood component of galactic gas. It has been suggested that the HVCs can be reproduced by a combination of three phenomena: a galactic fountain driven by disk supernovae which would account for most of the HVCs, material tidally torn from the Magellanic Clouds, and an outer arm complex which is associated with the large scale structure of the warped galactic disk. We sought to detect HVCs in external galaxies in order to test the galactic fountain model.

  9. A connection between star formation activity and cosmic rays in the starburst galaxy M82.

    PubMed

    2009-12-10

    Although Galactic cosmic rays (protons and nuclei) are widely believed to be mainly accelerated by the winds and supernovae of massive stars, definitive evidence of this origin remains elusive nearly a century after their discovery. The active regions of starburst galaxies have exceptionally high rates of star formation, and their large size-more than 50 times the diameter of similar Galactic regions-uniquely enables reliable calorimetric measurements of their potentially high cosmic-ray density. The cosmic rays produced in the formation, life and death of massive stars in these regions are expected to produce diffuse gamma-ray emission through interactions with interstellar gas and radiation. M82, the prototype small starburst galaxy, is predicted to be the brightest starburst galaxy in terms of gamma-ray emission. Here we report the detection of >700-GeV gamma-rays from M82. From these data we determine a cosmic-ray density of 250 eV cm(-3) in the starburst core, which is about 500 times the average Galactic density. This links cosmic-ray acceleration to star formation activity, and suggests that supernovae and massive-star winds are the dominant accelerators.

  10. A connection between star formation activity and cosmic rays in the starburst galaxy M82

    NASA Astrophysics Data System (ADS)

    VERITAS Collaboration; Acciari, V. A.; Aliu, E.; Arlen, T.; Aune, T.; Bautista, M.; Beilicke, M.; Benbow, W.; Boltuch, D.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Celik, O.; Cesarini, A.; Chow, Y. C.; Ciupik, L.; Cogan, P.; Colin, P.; Cui, W.; Dickherber, R.; Duke, C.; Fegan, S. J.; Finley, J. P.; Finnegan, G.; Fortin, P.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Gibbs, K.; Gillanders, G. H.; Godambe, S.; Grube, J.; Guenette, R.; Gyuk, G.; Hanna, D.; Holder, J.; Horan, D.; Hui, C. M.; Humensky, T. B.; Imran, A.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Kieda, D.; Kildea, J.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; Lebohec, S.; Maier, G.; McArthur, S.; McCann, A.; McCutcheon, M.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nagai, T.; Ong, R. A.; Otte, A. N.; Pandel, D.; Perkins, J. S.; Pizlo, F.; Pohl, M.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Roache, E.; Rose, H. J.; Schroedter, M.; Sembroski, G. H.; Smith, A. W.; Steele, D.; Swordy, S. P.; Theiling, M.; Thibadeau, S.; Varlotta, A.; Vassiliev, V. V.; Vincent, S.; Wagner, R. G.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; Weisgarber, T.; Williams, D. A.; Wissel, S.; Wood, M.; Zitzer, B.

    2009-12-01

    Although Galactic cosmic rays (protons and nuclei) are widely believed to be mainly accelerated by the winds and supernovae of massive stars, definitive evidence of this origin remains elusive nearly a century after their discovery. The active regions of starburst galaxies have exceptionally high rates of star formation, and their large size-more than 50 times the diameter of similar Galactic regions-uniquely enables reliable calorimetric measurements of their potentially high cosmic-ray density. The cosmic rays produced in the formation, life and death of massive stars in these regions are expected to produce diffuse γ-ray emission through interactions with interstellar gas and radiation. M82, the prototype small starburst galaxy, is predicted to be the brightest starburst galaxy in terms of γ-ray emission. Here we report the detection of >700-GeV γ-rays from M82. From these data we determine a cosmic-ray density of 250eVcm-3 in the starburst core, which is about 500 times the average Galactic density. This links cosmic-ray acceleration to star formation activity, and suggests that supernovae and massive-star winds are the dominant accelerators.

  11. Star Formation and Gas Accretion in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Yim, Kijeong; van der Hulst, J. M.

    2016-08-01

    In order to quantify the relationship between gas accretion and star formation, we analyse a sample of 29 nearby galaxies from the WHISP survey which contains galaxies with and without evidence for recent gas accretion. We compare combined radial profiles of FUV (GALEX) and IR 24 μm (Spitzer) characterizing distributions of recent star formation with radial profiles of CO (IRAM, BIMA, or CARMA) and H I (WSRT) tracing molecular and atomic gas contents to examine star formation efficiencies in symmetric (quiescent), asymmetric (accreting), and interacting (tidally disturbed) galaxies. In addition, we investigate the relationship between star formation rate and H I in the outer discs for the three groups of galaxies. We confirm the general relationship between gas surface density and star formation surface density, but do not find a significant difference between the three groups of galaxies.

  12. Hot coronae in nearby Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Tortosa, Alessia

    2016-08-01

    The primary X-ray emission in AGN is believed to be produced by Comptonization of optical/UV disk photons scattered up to the X-ray band by a hot corona located above the accretion disk. The emitted spectrum is, at the first order, a power-law with a high-energy cutoff, where the photon index and the cutoff energy are directly related to the temperature and to the optical depth of the plasma of hot electrons responsible for the inverse Compton scattering.To investigate the physical properties of the corona and provide constraints on its parameters, we have studied the broad band spectra of a sample of local Seyfert galaxies observed with NuSTAR (in coordination with XMM-Newton, Suzaku or Swift). We will discuss the general properties of the sample, and show a few particularly interesting cases.

  13. MaNGA: Mapping Nearby Galaxies at Apache Point Observatory

    NASA Astrophysics Data System (ADS)

    Bundy, Kevin

    2015-01-01

    I present the design and execution of a new survey to obtain resolved spectroscopy for 10,000 nearby galaxies called MaNGA (Mapping Nearby Galaxies at Apache Point Observatory). One of three core programs in the 6-year SDSS-IV project that began on July 1st, 2014, MaNGA will deploy 17 fiber-bundle IFUs across the Sloan 2.5m Telescope's 3 degree field-of-view, targeting a mass-selected sample with a median redshift of 0.03, typical spatial resolution of 1-2 kpc, and a per-fiber signal-to-noise ratio of 4-8 in the outskirts of target galaxies. For each galaxy in the sample, MaNGA will provide maps and measured gradients of the composition and dynamics of both stars and gas. Early results highlight MaNGA's potential to shed light on the ionization and chemical enrichment of gas in galaxies, spatial patterns in their star formation histories, and the internal makeup of stellar populations. MaNGA's unprecedented data set will not only provide powerful new insight on galaxy formation and evolution but will serve as a valuable benchmark for future high-z observations from large telescopes as well as space-based facilities.

  14. Mapping Extinction and Star Formation Rates of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Ridenour, Anthony; Takamiya, M.

    2010-01-01

    Star Formation Rate (SFR) is a physical characteristic of galaxies vital to our understanding of such problems as the evolution of the Universe. In computing SFRs obscuring dust systematically lowers them at shorter wavelengths compared to longer wavelengths. This issue of dust extinction has been handled well by multi-wavelength studies of nearby galaxies. Star Formation Rate measurements of distant galaxies are currently reliant on the emission of visible spectroscopic lines like Hα and [OII] after correction for extinction. However, if the visible light is completely obscured an incorrect assumption may be drawn; namely that there is neither SFR nor extinction. The work purposed here is to calibrate the SFR ascertained from Hα emission in nearby galaxies and compare it to radio and infrared emission. The Balmer decrement, or the ratio of Hβ to Hα emission, used to determine extinction, will also be studied and compared to infrared images. 30 nearby galaxies will be sampled and 2-D maps and Balmer decrements will be formed to do two things: measure SFRs and determine differences between Hα and infrared emission, and explore in what ways this difference corresponds with such things as the radio SFR, galaxy luminosity and morphological type. The accuracy of Hα as a SFR indicator and its determination as a sound tool in measuring SFRs of distant galaxies can both be quantified by interpreting these maps. Dr. Marianne Takamiya, the principal investigator and my mentor, secured funds through a grant to the University of Hawai'i at Hilo from The Research Corporation for Science Advancement Cottrell College Science Awards for this research.

  15. Evidence of nuclear disks in starburst galaxies from their radial distribution of supernovae

    NASA Astrophysics Data System (ADS)

    Herrero-Illana, R.; Pérez-Torres, M. Á.; Alberdi, A.

    2012-04-01

    Galaxy-galaxy interactions are expected to be responsible for triggering massive star formation and possibly accretion onto a supermassive black hole, by providing large amounts of dense molecular gas down to the central kiloparsec region. Several scenarios to drive the gas further down to the central ~100 pc, have been proposed, including the formation of a nuclear disk around the black hole, where massive stars would produce supernovae. Here, we probe the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M 82, Arp 299-A, and Arp 220, by using high-angular resolution (≲ 0.''1) radio observations published in the literature (for M 82 and Arp 220), or obtained by ourselves from the European VLBI Network (Arp 299-A). Our main goal was to characterize the nuclear starbursts in those galaxies and thus test scenarios that propose that nuclear disks of sizes ~100 pc form in the central regions of starburst galaxies. We obtained the radial distribution of supernovae (SNe) in the nuclear starbursts of M 82, Arp 299-A, and Arp 220, and derived scale-length values for the putative nuclear disks powering the bursts in those central regions. The scale lengths for the (exponential) disks range from ~20-30 pc for Arp 299-A and Arp 220, up to ~140 pc for M 82. The radial distribution of SNe for the nuclear disks in Arp 299-A and Arp 220 is also consistent with a power-law surface density profile of exponent γ = 1, as expected from detailed hydrodynamical simulations of nuclear disks. Our results support scenarios where a nuclear disk of size ~100 pc is formed in (U)LIRGs, and sustained by gas pressure, in which case the accretion onto the black hole could be lowered by supernova feedback. Appendices are available in electronic form at http://www.aanda.org

  16. Stellar feedback as the origin of an extended molecular outflow in a starburst galaxy.

    PubMed

    Geach, J E; Hickox, R C; Diamond-Stanic, A M; Krips, M; Rudnick, G H; Tremonti, C A; Sell, P H; Coil, A L; Moustakas, J

    2014-12-01

    Recent observations have revealed that starburst galaxies can drive molecular gas outflows through stellar radiation pressure. Molecular gas is the phase of the interstellar medium from which stars form, so these outflows curtail stellar mass growth in galaxies. Previously known outflows, however, involve small fractions of the total molecular gas content and have typical scales of less than a kiloparsec. In at least some cases, input from active galactic nuclei is dynamically important, so pure stellar feedback (the momentum return into the interstellar medium) has been considered incapable of rapidly terminating star formation on galactic scales. Molecular gas has been detected outside the galactic plane of the archetypal starburst galaxy M82 (refs 4 and 5), but so far there has been no evidence that starbursts can propel substantial quantities of cold molecular gas to the same galactocentric radius (about 10 kiloparsecs) as the warmer gas that has been traced by metal ion absorbers in the circumgalactic medium. Here we report observations of molecular gas in a compact (effective radius 100 parsecs) massive starburst galaxy at redshift 0.7, which is known to drive a fast outflow of ionized gas. We find that 35 per cent of the total molecular gas extends approximately 10 kiloparsecs, and one-third of this extended gas has a velocity of up to 1,000 kilometres per second. The kinetic energy associated with this high-velocity component is consistent with the momentum flux available from stellar radiation pressure. This demonstrates that nuclear bursts of star formation are capable of ejecting large amounts of cold gas from the central regions of galaxies, thereby strongly affecting their evolution by truncating star formation and redistributing matter. PMID:25471881

  17. Stellar feedback as the origin of an extended molecular outflow in a starburst galaxy.

    PubMed

    Geach, J E; Hickox, R C; Diamond-Stanic, A M; Krips, M; Rudnick, G H; Tremonti, C A; Sell, P H; Coil, A L; Moustakas, J

    2014-12-01

    Recent observations have revealed that starburst galaxies can drive molecular gas outflows through stellar radiation pressure. Molecular gas is the phase of the interstellar medium from which stars form, so these outflows curtail stellar mass growth in galaxies. Previously known outflows, however, involve small fractions of the total molecular gas content and have typical scales of less than a kiloparsec. In at least some cases, input from active galactic nuclei is dynamically important, so pure stellar feedback (the momentum return into the interstellar medium) has been considered incapable of rapidly terminating star formation on galactic scales. Molecular gas has been detected outside the galactic plane of the archetypal starburst galaxy M82 (refs 4 and 5), but so far there has been no evidence that starbursts can propel substantial quantities of cold molecular gas to the same galactocentric radius (about 10 kiloparsecs) as the warmer gas that has been traced by metal ion absorbers in the circumgalactic medium. Here we report observations of molecular gas in a compact (effective radius 100 parsecs) massive starburst galaxy at redshift 0.7, which is known to drive a fast outflow of ionized gas. We find that 35 per cent of the total molecular gas extends approximately 10 kiloparsecs, and one-third of this extended gas has a velocity of up to 1,000 kilometres per second. The kinetic energy associated with this high-velocity component is consistent with the momentum flux available from stellar radiation pressure. This demonstrates that nuclear bursts of star formation are capable of ejecting large amounts of cold gas from the central regions of galaxies, thereby strongly affecting their evolution by truncating star formation and redistributing matter.

  18. Optical spectroscopy of the radio-loud nuclei of spiral galaxies: Starbursts or monsters

    SciTech Connect

    Heckman, T.M.; Van Breugel, W.; Miley, G.K.; Butcher, H.R.

    1983-08-01

    We present optical spectroscopic data pertaining to the physical state, kinematics, and spatial extent of the emission-line gas near the radio-loud nuclei of spiral galaxies. These data are combined with published optical, radio, and infrared data to evaluate the suggestions by Condon et al. (1982) that the nuclear radio emission in this class of galaxy is produced by multiple supernova remnants generated as a consequence of a nuclear starburst. As a whole, the radio-loud nuclei have stronger emission lines than radio-quiet nuclei of galaxies of similar Hubble/de Vaucouleurs type. This emission-line gas is generally at least as spatially extended as the radio continuum emission. However, we find that only about 1/3 of the spiral galaxies examined have optical spectroscopic properties consistent with those of ''extranuclear starbursts'' (i.e., giant H II regions). The majority of the nuclei seem to require a form of energy input to the ionized gas which is ''harder'' than the Lyman continuum radiation of OB stars, as their emission-line spectra are of the Seyfert or Liner variety. The nuclei with H II region spectra are distinct from the nuclei with Seyfert spectra in terms of radio morphology and radio spectral index, and tend to occur in spiral galaxies of much later Hubble type than do the Seyfert or Liner nuclei (Sc vs Sa). Moreover, the most luminous nuclear radio sources in our sample (PMHz> or =10/sup 22/ Watts Hz/sup -1/ Sr/sup -1/) are not associated with H II region nuclei. We summarize evidence that the putative nuclear starbursts must differ significantly from extranuclear starbursts.

  19. The dwarf galaxy population of nearby galaxy clusters

    NASA Astrophysics Data System (ADS)

    Lisker, Thorsten; Wittmann, Carolin; Pak, Mina; Janz, Joachim; Bialas, Daniel; Peletier, Reynier; Grebel, Eva; Falcon Barroso, Jesus; Toloba, Elisa; Smakced Collaboration, Focus Collaboration

    2015-01-01

    The Fornax, Virgo, Ursa Major and Perseus galaxy clusters all have very different characteristics, in terms of their density, mass, and large-scale environment. We can regard these clusters as laboratories for studying environmental influence on galaxy evolution, using the sensitive low-mass galaxies as probes for external mechanisms. Here we report on recent and ongoing observational studies of the said clusters with imaging and spectroscopy, as well as on the interpretation of present-day cluster galaxy populations with the aid of cosmological simulations.Multicolor imaging data allow us to identify residual star formation in otherwise red early-type dwarf galaxies, which hold clues to the strength of gas stripping processes. Major-axis spectra and 2D kinematical maps provide insight regarding the amount of rotational support and how much dynamical heating a dwarf galaxy may have experienced. To this end, dedicated N-body simulations that follow the evolution of galaxies since early epochs reveal their path through parameter space, and can be compared to observations in order to understand the time-integrated effect of environmental influence.

  20. Radial Star Formation Histories in 15 Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Dale, Daniel A.; Beltz-Mohrmann, Gillian D.; Egan, Arika A.; Hatlestad, Alan J.; Herzog, Laura J.; Leung, Andrew S.; McLane, Jacob N.; Phenicie, Christopher; Roberts, Jareth S.; Barnes, Kate L.; Boquien, Médéric; Calzetti, Daniela; Cook, David O.; Kobulnicky, Henry A.; Staudaher, Shawn M.; van Zee, Liese

    2016-01-01

    New deep optical and near-infrared imaging is combined with archival ultraviolet and infrared data for 15 nearby galaxies mapped in the Spitzer Extended Disk Galaxy Exploration Science survey. These images are particularly deep and thus excellent for studying the low surface brightness outskirts of these disk-dominated galaxies with stellar masses ranging between 108 and {10}11 {M}⊙ . The spectral energy distributions derived from this data set are modeled to investigate the radial variations in the galaxy colors and star formation histories. Taken as a whole, the sample shows bluer and younger stars for larger radii until reversing near the optical radius, whereafter the trend is for redder and older stars for larger galacto-centric distances. These results are consistent with an inside-out disk formation scenario coupled with an old stellar outer disk population formed through radial migration and/or the cumulative history of minor mergers and accretions of satellite dwarf galaxies. However, these trends are quite modest and the variation from galaxy to galaxy is substantial. Additional data for a larger sample of galaxies are needed to confirm or dismiss these modest sample-wide trends.

  1. ROSAT PSPC and HRI observations of the composite starburst/Seyfert 2 galaxy NGC 1672

    NASA Technical Reports Server (NTRS)

    Brandt, W. N.; Halpern, Jules P.; Iwasawa, K.

    1995-01-01

    The nearby barred spiral galaxy NGC 1672 has been observed with the Position Sensitive Proportional Counter (PSPC) and High Resolution Imager (HRI) instruments on board the ROSAT X-ray satellite. NGC 1672 is thought to have an obscured Seyfert nucleus, and it has strong starburst activity as well. Three bright X-ray sources with luminosities 1-2 x 10(exp 40) erg/s are clearly identified with NGC 1672. The strongest lies at the nucleus, and the other two lie at the ends of NGC 1672's prominent bar, locations that are also bright in H alpha and near-infrared images. The nuclear source is resolved by the HRI on about the scale of the recently identified nuclear ring, and one of the sources at the ends of the bar is also probably resolved. The X-ray spectrum of the nuclear source is quite soft, having a Raymond-Smith plasma temperature of approximately equals 0.7 keV and little evidence for intrinsic absorption. The ROSAT band X-ray flux of the nuclear source appears to be dominated not by X-ray binary emission but rather by diffuse gas emission. The absorption and emission properties of the sources, as well as their spatial extents, lead us to models of superbubbles driven by supernovae. However, the large density and emission measure of the nuclear X-ray source stretch the limits that can be comfortably accommodated by these models. We do not detect direct emission from the putative Seyfert nucleus, although an alternative model for the nuclear source is thermal emission from gas that is photoionized by a hidden Seyfert nucleus. The spectra of the other two X-ray sources are harder than that of the nuclear source, and have similar difficulties with regard to superbubble models.

  2. STAR FORMATION RATES FOR STARBURST GALAXIES FROM ULTRAVIOLET, INFRARED, AND RADIO LUMINOSITIES

    SciTech Connect

    Sargsyan, Lusine A.; Weedman, Daniel W. E-mail: dweedman@isc.astro.cornell.edu

    2009-08-20

    We present a comparison of star formation rates (SFR) determined from mid-infrared 7.7 {mu}m polycyclic aromatic hydrocarbon (PAH) luminosity [SFR(PAH)], from 1.4 GHz radio luminosity [SFR(radio)], and from far-ultraviolet luminosity [SFR(UV)] for a sample of 287 starburst galaxies with z < 0.5 having Spitzer IRS observations. The previously adopted relation log [SFR(PAH)] = log [{nu}L {sub {nu}}(7.7 {mu}m)] - 42.57 {+-} 0.2, for SFR in M{sub sun} yr{sup -1} and {nu}L {sub {nu}}(7.7 {mu}m) the luminosity at the peak of the 7.7 {mu}m PAH feature in erg s{sup -1}, is found to agree with SFR(radio). Comparing with SFR(UV) determined independently from ultraviolet observations of the same sources with the Galaxy Evolution Explorer mission (not corrected for dust extinction), the median log [SFR(PAH)/SFR(UV)] = 1.67, indicating that only 2% of the ultraviolet continuum typically escapes extinction by dust within a starburst. This ratio SFR(PAH)/SFR(UV) depends on infrared luminosity, with the form log [SFR(PAH)/SFR(UV)] = (0.53 {+-} 0.05)log [{nu}L{sub {nu}}(7.7 {mu}m)] - 21.5 {+-} 0.18, indicating that more luminous starbursts are also dustier. Using our adopted relation between {nu}L{sub {nu}}(7.7 {mu}m) and L {sub ir}, this becomes log [SFR(PAH)/SFR(UV)]= (0.53 {+-} 0.05)log L{sub ir} - 4.11 {+-} 0.18, for L{sub ir} in L{sub sun}. Only blue compact dwarf galaxies show comparable or greater SFR(UV) compared to SFR(PAH). We also find that the ratio SFR(PAH)/SFR(UV) is similar to that in infrared-selected starbursts for a sample of Markarian starburst galaxies originally selected using optical classification, which implies that there is no significant selection effect in SFR(PAH)/SFR(UV) using starburst galaxies discovered by Spitzer. These results indicate that SFRs determined with ultraviolet luminosities require dust corrections by a factor of {approx}10 for typical local starbursts but this factor increases to >700 for the most luminous starbursts at z {approx} 2

  3. Very deep IRAS survey - constraints on the evolution of starburst galaxies

    SciTech Connect

    Hacking, P.; Houck, J.R.; Condon, J.J.

    1987-05-01

    Counts of sources (primarily starburst galaxies) from a deep 60 microns IRAS survey published by Hacking and Houck (1987) are compared with four evolutionary models. The counts below 100 mJy are higher than expected if no evolution has taken place out to a redshift of approximately 0.2. Redshift measurements of the survey sources should be able to distinguish between luminosity-evolution and density-evolution models and detect as little as a 20 percent brightening or increase in density of infrared sources per billion years ago (H/0/ = 100 km/s per Mpc). Starburst galaxies cannot account for the reported 100 microns background without extreme evolution at high redshifts. 21 references.

  4. HDI in Action: Comparison Imaging of the Interacting Starburst Galaxy NGC 3310

    NASA Astrophysics Data System (ADS)

    Wehner, Elizabeth

    2015-01-01

    NGC 3310 is an interacting starburst galaxy located approximately 18 Mpc away. Previous studies reveal a circumnuclear starburst, substantial star formation in its spiral arms, and an extensive system of tidal debris likely induced from the collision with and subsequent merger of a now-destroyed companion galaxy. A study by Wehner et al. in 2006 revealed the presence of a previously undetected tidal loop in the Northeast quadrant of the system. We have obtained follow up observations of this system using the newly-built Half Degree Imager (HDI) recently mounted on the WIYN 0.9m telescope in Kitt Peak, Arizaon. We present a comparison of deep imaging of NGC 3310 from HDI and from S2KB, the former primary CCD camera on the 0.9m. We present our results for comparison of image depth and image quality in order to assess the new HDI camera for future low surface brightness observations.

  5. A very deep IRAS survey - Constraints on the evolution of starburst galaxies

    NASA Astrophysics Data System (ADS)

    Hacking, Perry; Condon, J. J.; Houck, J. R.

    1987-05-01

    Counts of sources (primarily starburst galaxies) from a deep 60 microns IRAS survey published by Hacking and Houck (1987) are compared with four evolutionary models. The counts below 100 mJy are higher than expected if no evolution has taken place out to a redshift of approximately 0.2. Redshift measurements of the survey sources should be able to distinguish between luminosity-evolution and density-evolution models and detect as little as a 20 percent brightening or increase in density of infrared sources per billion years ago (H/0/ = 100 km/s per Mpc). Starburst galaxies cannot account for the reported 100 microns background without extreme evolution at high redshifts.

  6. Study of Starburst/Activity/Interaction Phenomena based on the Multiple Byurakan-IRAS Galaxies

    NASA Astrophysics Data System (ADS)

    Harutyunyan, Gohar S.; Mickaelian, Areg M.

    2014-07-01

    The Byurakan-IRAS Galaxy (BIG) sample is the result of optical identifications of IRAS PSC sources at high-galactic latitudes using the First Byurakan Survey (FBS) low-dispersion spectra. Among the 1178 objects most are spiral galaxies and many have been proved to be AGN and starburst by spectroscopic observations, as well as there is a number of ULIRGs among these objects. BIG objects contain galaxy pairs, multiples, and small groups that are subject for study on the matter of the real IR-emitter in these systems. Given that these objects are powerful IR sources, they are considered as young systems indicating high rate of evolution and starburst activity exceeding 100 M o /yr. Spectroscopic observations show that all these systems are physical ones and we were able to measure the mutual distances and sizes for all components. Cross-correlations with the recent more accurate IR catalogues, such as 2MASS and WISE, as well as radio ones (NVSS, FIRST), provided accurate coordinates of the IR source and possibility to find the individual galaxy responsible for the IR. However, in almost half of the cases, IR position indicates the intermediate region between the components, which means that it comes from the system as a whole. Some more MW data have been matched to IR and radio to have an overall understanding on these systems. Given that these systems are mostly interacting/merging ones often containing AGN and most of them may be considered as powerful starbursts, it is possible to study starburst/activity/interaction phenomena and their interrelationship.

  7. Uv Imaging of Nearby Galaxies with FOC/96

    NASA Astrophysics Data System (ADS)

    Maoz, Dan

    1991-07-01

    A random sample from among 256 nearby galaxies in the UGC and ESO catalogs will be imaged in the ultraviolet (2200 A) in a Snapshot Survey. Brief (10-minute) exposures will be obtained with the FOC in its F/96 mode with a 22"x22" field of view. The images will be used to search for low-luminosity AGNs that appear as unresolved UV point sources in the nuclei of galaxies. These weak AGNs, which can be detected directly only with HST, will help define the relations between quasars, active galaxies, and normal galaxies. The images will also be used to identify regions of active star formation and to search for compact galactic cores indicative of possible central massive black holes. The sample includes a variety of Hubble types of normal galaxies, as well as peculiar and interacting galaxies. For late-type galaxies, the visible-light leak to the detector will be small (a few %) and the UV light distribution will determine the spatial distribution of young stellar populations. The small field-of-view, high-resolution images will complement rocket-borne and ASTRO observations, and will provide the community with a valuable database. All objects that will be imaged in the UV by other Cycle 2 programs have been removed from the sample.

  8. Diffuse Hard X-Ray Emission in Starburst Galaxies as Synchrotron from Very High Energy Electrons

    NASA Astrophysics Data System (ADS)

    Lacki, Brian C.; Thompson, Todd A.

    2013-01-01

    The origin of the diffuse hard X-ray (2-10 keV) emission from starburst galaxies is a long-standing problem. We suggest that synchrotron emission of 10-100 TeV electrons and positrons (e ±) can contribute to this emission, because starbursts have strong magnetic fields. We consider three sources of e ± at these energies: (1) primary electrons directly accelerated by supernova remnants, (2) pionic secondary e ± created by inelastic collisions between cosmic ray (CR) protons and gas nuclei in the dense interstellar medium of starbursts, and (3) pair e ± produced between the interactions between 10 and 100 TeV γ-rays and the intense far-infrared (FIR) radiation fields of starbursts. We create one-zone steady-state models of the CR population in the Galactic center (R <= 112 pc), NGC 253, M82, and Arp 220's nuclei, assuming a power-law injection spectrum for electrons and protons. We consider different injection spectral slopes, magnetic field strengths, CR acceleration efficiencies, and diffusive escape times, and include advective escape, radiative cooling processes, and secondary and pair e ±. We compare these models to extant radio and GeV and TeV γ-ray data for these starbursts, and calculate the diffuse synchrotron X-ray and inverse Compton (IC) luminosities of these starbursts in the models which satisfy multiwavelength constraints. If the primary electron spectrum extends to ~PeV energies and has a proton/electron injection ratio similar to the Galactic value, we find that synchrotron emission contributes 2%-20% of their unresolved, diffuse hard X-ray emission. However, there is great uncertainty in this conclusion because of the limited information on the CR electron spectrum at these high energies. IC emission is likewise a minority of the unresolved X-ray emission in these starbursts, from 0.1% in the Galactic center to 10% in Arp 220's nuclei, with the main uncertainty being the starbursts' magnetic field. We also model generic starbursts, including

  9. Class I methanol megamasers: a potential probe of starburst activity and feedback in active galaxies

    NASA Astrophysics Data System (ADS)

    Chen, X.; Ellingsen, S. P.; Zhang, J.-S.; Wang, J.-Z.; Shen, Z.-Q.; Wu, Q.-W.; Wu, Z.-Z.

    2016-06-01

    Previous observations have shown that the distribution of 36.2-GHz class I methanol megamaser (MM) emission in Arp 220 is highly correlated with the diffuse X-rays. On this basis it was suggested that methanol MM may be produced either by the effects of galactic-outflow-driven shocks and/or cosmic rays. Here we report the results of a single-dish survey undertaken with the Greenbank Telescope (GBT) to improve our understanding of the pumping conditions of extragalactic class I methanol masers and their relationship to starburst and feedback processes within the host galaxies, towards a sample which includes 16 galaxies which show both extended soft X-ray emission, and either OH or H2O MM emission. Large baseline ripples in the GBT spectra limited our results to tentative detections towards 11 of the target galaxies. Analysis of these tentative detections shows that there are significant correlations between the methanol intensity and the host-galaxy infrared, radio and OH MM emission, but no correlation with the X-ray and H2O MM emission. Some sources show methanol emission significantly offset from the systemic velocity of the galaxy (by up to 1000 km s-1) and we propose that these are associated with galactic-scale outflows from active galactic nuclei (AGNs) feedback. The combined observational properties suggest that class I methanol MMs are related to significant starburst and molecular outflow activity and hence may provide a potential probe of AGN feedback and starburst processes in the host galaxies.

  10. COMPARING ULTRAVIOLET- AND INFRARED-SELECTED STARBURST GALAXIES IN DUST OBSCURATION AND LUMINOSITY

    SciTech Connect

    Sargsyan, Lusine A.; Weedman, Daniel W.; Houck, James R. E-mail: dweedman@isc.astro.cornell.ed

    2010-06-01

    We present samples of starburst galaxies that represent the extremes discovered with infrared and ultraviolet observations, including 25 Markarian galaxies, 23 ultraviolet-luminous galaxies discovered with GALEX, and the 50 starburst galaxies having the largest infrared/ultraviolet ratios. These sources have z < 0.5 and cover a luminosity range of {approx}10{sup 4}. Comparisons between infrared luminosities determined with the 7.7 {mu}m polycyclic aromatic hydrocarbon feature and ultraviolet luminosities from the stellar continuum at 153 nm are used to determine obscuration in starbursts and dependence of this obscuration on infrared or ultraviolet luminosity. A strong selection effect arises for the ultraviolet-selected samples: the brightest sources appear bright because they have the least obscuration. Obscuration correction for the ultraviolet-selected Markarian+GALEX sample has the form log[UV(intrinsic)/UV(observed)] = 0.07({+-}0.04)M(UV) + 2.09 {+-} 0.69 but for the full infrared-selected Spitzer sample is log[UV(intrinsic)/UV(observed)] = 0.17({+-}0.02)M(UV) + 4.55 {+-} 0.4. The relation of total bolometric luminosity L {sub ir} to M(UV) is also determined for infrared-selected and ultraviolet-selected samples. For ultraviolet-selected galaxies, log L {sub ir} = -(0.33 {+-} 0.04)M(UV) + 4.52 {+-} 0.69. For the full infrared-selected sample, log L {sub ir} = -(0.23 {+-} 0.02)M(UV) + 6.99 {+-} 0.41, all for L {sub ir} in L{sub sun} and M(UV) the AB magnitude at rest frame 153 nm. These results imply that obscuration corrections by factors of 2-3 determined from reddening of the ultraviolet continuum for Lyman break galaxies with z>2 are insufficient, and should be at least a factor of 10 for M(UV) {approx} -17, with decreasing correction for more luminous sources.

  11. The Mitchell Spectrograph: Studying Nearby Galaxies with the VIRUS Prototype

    NASA Astrophysics Data System (ADS)

    Blanc, Guillermo A.

    The Mitchell Spectrograph (a.k.a. VIRUS-P) on the 2.7m Harlan J. Smith telescope at McDonald Observatory is currently the largest field of view (FOV) integral field unit (IFU) spectrograph in the world (1.7'x1.7'). It was designed as a prototype for the highly replicable VIRUS spectrograph which consists of a mosaic of IFUs spread over a 16' diameter FOV feeding 150 spectrographs similar to the Mitchell. VIRUS will be deployed on the 9.2 meter Hobby-Eberly Telescope (HET) and will be used to conduct the HET Dark Energy Experiment (HETDEX). Since seeing first light in 2007 the Mitchell Spectrograph has been widely used, among other things, to study nearby galaxies in the local universe where their internal structure and the spatial distribution of different physical parameters can be studied in great detail. These observations have provided important insight into many aspects of the physics behind the formation and evolution of galaxies and have boosted the scientific impact of the 2.7 meter telescope enormously. Here I review the contributions of the Mitchell Spectrograph to the study of nearby galaxies, from the investigation of the spatial distribution of dark matter and the properties of supermassive black holes, to the studies of the process of star formation and the chemical composition of stars and gas in the ISM, which provide important information regarding the formation and evolution of these systems. I highlight the fact that wide field integral field spectrographs on small and medium size telescopes can be powerful cost effective tools to study the astrophysics of galaxies. Finally I briefly discuss the potential of HETDEX for conducting studies on nearby galaxies. The survey parameters make it complimentary and competitive to ongoing and future surveys like SAMI and MANGA.

  12. The SDSS Discovery of a Strongly Lensed Post-Starburst Galaxy at z=0.766

    SciTech Connect

    Shin, Min-Su; Strauss, Michael A.; Oguri, Masamune; Inada, Naohisa; Falco, Emilio E.; Broadhurst, Tom; Gunn, James E.

    2008-09-30

    We present the first result of a survey for strong galaxy-galaxy lenses in Sloan Digital Sky Survey (SDSS) images. SDSS J082728.70+223256.4 was selected as a lensing candidate using selection criteria based on the color and positions of objects in the SDSS photometric catalog. Follow-up imaging and spectroscopy showed this object to be a lensing system. The lensing galaxy is an elliptical at z = 0.349 in a galaxy cluster. The lensed galaxy has the spectrum of a post-starburst galaxy at z = 0.766. The lensing galaxy has an estimated mass of {approx} 1.2 x 10{sup 12} M{sub {circle_dot}} and the corresponding mass to light ratio in the B-band is {approx} 26 M{sub {circle_dot}}/L{sub {circle_dot}} inside 1.1 effective radii of the lensing galaxy. Our study shows how catalogs drawn from multi-band surveys can be used to find strong galaxy-galaxy lenses having multiple lens images. Our strong lensing candidate selection based on photometry-only catalogs will be useful in future multi-band imaging surveys such as SNAP and LSST.

  13. Resolved Star Formation Law In Nearby Infrared-bright Galaxies

    NASA Astrophysics Data System (ADS)

    Rahman, Nurur; Bolatto, A.; Wong, T.; Leroy, A.; Ott, J.; Calzetti, D.; Blitz, L.; Walter, F.; Rosolowsky, E.; West, A.; Vogel, S.; Bigiel, F.; Xue, R.

    2009-05-01

    An accurate knowledge of star formation law is crucial to make progress in understanding galaxy formation and evolution. We are studying this topic using CARMA STING (Survey Toward Infrared-bright Nearby Galaxies), an interferometric CO survey of a sample of 27 star-forming nearby galaxies with a wealth of multi-wavelength data designed to study star formation in environments throughout the blue sequence at sub-kpc scales. We present results for NGC 4254 (M99), one of our sample galaxies. We construct star formation rate surface density (SFRSD) and gas (atomic and molecular) surface density indicators using a combination of high resolution data from CARMA, KPNO, Spitzer, IRAM and VLA. We find a tight correlation between SFRSD and molecular gas surface density (MGSD), whereas the relation between atomic gas surface density and SFRSD shows very large scatter. Within the central 6 kpc (radius) where CARMA is the most sensitive the MGSD derived from CO(1-0) and CO(2-1) shows similar trend, however, in the extended disk the slope, derived from CO(2-1) data alone, gets steeper.

  14. Dusty starburst galaxies in the early Universe as revealed by gravitational lensing.

    PubMed

    Vieira, J D; Marrone, D P; Chapman, S C; De Breuck, C; Hezaveh, Y D; Weiβ, A; Aguirre, J E; Aird, K A; Aravena, M; Ashby, M L N; Bayliss, M; Benson, B A; Biggs, A D; Bleem, L E; Bock, J J; Bothwell, M; Bradford, C M; Brodwin, M; Carlstrom, J E; Chang, C L; Crawford, T M; Crites, A T; de Haan, T; Dobbs, M A; Fomalont, E B; Fassnacht, C D; George, E M; Gladders, M D; Gonzalez, A H; Greve, T R; Gullberg, B; Halverson, N W; High, F W; Holder, G P; Holzapfel, W L; Hoover, S; Hrubes, J D; Hunter, T R; Keisler, R; Lee, A T; Leitch, E M; Lueker, M; Luong-Van, D; Malkan, M; McIntyre, V; McMahon, J J; Mehl, J; Menten, K M; Meyer, S S; Mocanu, L M; Murphy, E J; Natoli, T; Padin, S; Plagge, T; Reichardt, C L; Rest, A; Ruel, J; Ruhl, J E; Sharon, K; Schaffer, K K; Shaw, L; Shirokoff, E; Spilker, J S; Stalder, B; Staniszewski, Z; Stark, A A; Story, K; Vanderlinde, K; Welikala, N; Williamson, R

    2013-03-21

    In the past decade, our understanding of galaxy evolution has been revolutionized by the discovery that luminous, dusty starburst galaxies were 1,000 times more abundant in the early Universe than at present. It has, however, been difficult to measure the complete redshift distribution of these objects, especially at the highest redshifts (z > 4). Here we report a redshift survey at a wavelength of three millimetres, targeting carbon monoxide line emission from the star-forming molecular gas in the direction of extraordinarily bright millimetre-wave-selected sources. High-resolution imaging demonstrates that these sources are strongly gravitationally lensed by foreground galaxies. We detect spectral lines in 23 out of 26 sources and multiple lines in 12 of those 23 sources, from which we obtain robust, unambiguous redshifts. At least 10 of the sources are found to lie at z > 4, indicating that the fraction of dusty starburst galaxies at high redshifts is greater than previously thought. Models of lens geometries in the sample indicate that the background objects are ultra-luminous infrared galaxies, powered by extreme bursts of star formation.

  15. Characterizing the radio continuum emission from intense starburst galaxies

    NASA Astrophysics Data System (ADS)

    Galvin, T. J.; Seymour, N.; Filipović, M. D.; Tothill, N. F. H.; Marvil, J.; Drouart, G.; Symeonidis, M.; Huynh, M. T.

    2016-09-01

    The intrinsic thermal (free-free) and non-thermal (synchrotron) emission components that comprise the radio continuum of galaxies represent unique, dust-free measures of star formation rates (SFR). Such high SFR galaxies will dominate the deepest current and future radio surveys. We disentangle the thermal and non-thermal emission components of the radio continuum of six ultraluminous infrared galaxies (LFIR > 1012.5 L⊙) at redshifts of 0.2 ≤ z ≤ 0.5 and 22 IR selected galaxies. Radio data over a wide frequency range (0.8 < ν < 10 GHz) are fitted with a star-forming galaxy model comprising of thermal and non-thermal components. The luminosities of both radio continuum components are strongly correlated to the 60 μm luminosity across many orders of magnitude (consistent with the far-IR to radio correlation). We demonstrate that the spectral index of the radio continuum spectral energy distribution is a useful proxy for the thermal fraction. We also find that there is an increase in mean and scatter of the thermal fraction with FIR to radio luminosity ratio which could be influenced by different time-scales of the thermal and non-thermal emission mechanisms.

  16. A survey of the molecular ISM properties of nearby galaxies using the Herschel FTS

    SciTech Connect

    Kamenetzky, J.; Rangwala, N.; Glenn, J.; Maloney, P. R.; Conley, A.

    2014-11-10

    The {sup 12}CO J = 4 → 3 to J = 13 → 12 lines of the interstellar medium from nearby galaxies, newly observable with the Herschel SPIRE Fourier transform spectrometer, offer an opportunity to study warmer, more luminous molecular gas than that traced by {sup 12}CO J = 1 → 0. Here we present a survey of 17 nearby infrared-luminous galaxy systems (21 pointings). In addition to photometric modeling of dust, we modeled full {sup 12}CO spectral line energy distributions from J = 1 → 0 to J = 13 → 12 with two components of warm and cool CO gas, and included LTE analysis of [C I], [C II], [N II], and H{sub 2} lines. CO is emitted from a low-pressure/high-mass component traced by the low-J lines and a high-pressure/low-mass component that dominates the luminosity. We found that, on average, the ratios of the warm/cool pressure, mass, and {sup 12}CO luminosity are 60 ± 30, 0.11 ± 0.02, and 15.6 ± 2.7. The gas-to-dust-mass ratios are <120 throughout the sample. The {sup 12}CO luminosity is dominated by the high-J lines and is 4 × 10{sup –4} L {sub FIR} on average. We discuss systematic effects of single-component and multi-component CO modeling (e.g., single-component J ≤ 3 models overestimate gas pressure by ∼0.5 dex), as well as compare to Galactic star-forming regions. With this comparison, we show the molecular interstellar medium of starburst galaxies is not simply an ensemble of Galactic-type giant molecular clouds. The warm gas emission is likely dominated by regions resembling the warm extended cloud of Sgr B2.

  17. Nuclear activity and the environments of nearby radio galaxies

    NASA Technical Reports Server (NTRS)

    Dey, Arjun; Vanbreugel, Wil

    1993-01-01

    Much of our present understanding of galaxy evolution over a large redshift range is based on the study of samples selected on the basis of non-thermal radio emission. It is therefore necessary to understand the relationship between radio source activity and the host galaxy. Recent observations suggest that there is a connection between radio galaxy (RG) activity and radio galaxy evolution. For example, high-redshift RGs (z approx. greater than 0.7) show evidence for significant populations of young stars, and have optical continuum morphologies nearly always aligned with the radio axis (McCarthy et al. 1987; Chambers et al. 1987). This phenomenon is generally attributed to radio jet induced star formation (DeYoung 1989), but the lack of high S/N spectra of the galaxy continua, and recent detections of polarized light in a few objects make it hard to rule out other processes such as scattering or synchrotron radiation. A detailed study of the continuum light in the distant RGs is difficult as they are optically very faint. However, nearby RGs (z approx. less than 0.1) have bluer B-V colors than radio-quiet ellipticals, presumably due to the presence of young stellar populations (Smith and Heckman 1989) and several have extended UV continuum emitting regions along their radio axes (van Bruegel et al. 1985a, b, di Serego Alighieri et al. 1989), reminiscent of the alignment effect seen in the high redshift RGs. We have almost completed a continuum imaging survey of nearby (and therefore optically brighter), powerful RGs to study any possible relationships between the optical continuum light and radio source activity. In particular we are interested in (1) whether these lower redshift RGs shown any evidence of the alignment effect (in their rest-frame UV light) that is seen in the distant RGs, and (2) the effects that the radio source has on the environment of the host galaxy.

  18. Multi-Wavelength Study of Nearby Dwarf Galaxies: Properties of Low-Metallicity Interstellar Media

    NASA Astrophysics Data System (ADS)

    Galliano, Frédéric

    2004-04-01

    This thesis is devoted to the multi-wavelength observations and the modelling of dust, in nearby low-metallicity dwarf galaxies. The main motivations of this project are: (i) the study of dust properties - composition, size distribution, etc. - in non-solar interstellar media; (ii) the study of global spectral energy distributions of dwarf galaxies which are thought, due to their chemical youth, to be similar to primordial galaxies that we can not observe; and (iii) obtaining informations about the chemical evolution of these galaxies by studying the gas-to-dust mass ratio. I begin with the detailed study of mid-infrared ISO spectra of these galaxies. The main spectral characteristics that we outline are: (i) the weakness of the aromatic band emission, compared to what is observed in normal starburst galaxies; (ii) the similarity with Galactic HII region spectra - a steep very small grain continuum and prominent ionic lines. After that, we study the spectra of a more diversified sample - spiral, starburst, dwarf galaxies and HII regions - in order to plot the band ratios. The 6.2/11.3, 7.7/11.3 and 8.6/11.3 correlations are, for the first time, established on such a large sample. They show that dwarf galaxies occupy a particular region in this diagram, different than the one occupied by Galactic HII regions, inducing a different PAH structure - ionization, hydrogenation, size, etc. The second step of this project is the modelling of the spectral energy distributions of four dwarf galaxies (He 2-10, II Zw 40, NGC 1140, NG 1569), from ultraviolet to millimeter. In order to achieve this goal, I have added, to our own observations, data from the litterature. The modelling is done self-consistently, using constraints on dust emission, stellar radiation and on ionic lines. We synthesize the spectral energy distributions of these galaxies, as well as the corresponding extinction curves. The properties that we are able to outline are that: (i) the emission is dominated by

  19. Searching for X-ray sources in nearby late-type galaxies with low-star formation rates

    NASA Astrophysics Data System (ADS)

    Chatterjee, K.; Kaaret, P.; Brorby, M.; Kajava, J. J. E.; Grisé, F.; Farrell, S.; Poutanen, J.

    2016-03-01

    Late-type non-starburst galaxies have been shown to contain X-ray emitting objects, some being ultraluminous X-ray sources. We report on XMM-Newton observations of 11 nearby, late-type galaxies previously observed with the Hubble Space Telescope (HST) in order to find such objects. We found 18 X-ray sources in or near the optical extent of the galaxies, most being point-like. If associated with the corresponding galaxies, the source luminosities range from 2 × 1037 erg s-1 to 6 × 1039 erg s-1. We found one ultraluminous X-ray source, which is in the galaxy IC 5052, and one source coincident with the galaxy IC 4662 with a blackbody temperature of 0.166 ± 0.015 keV that could be a quasi-soft source or a quiescent neutron star X-ray binary in the Milky Way. One X-ray source, XMMU J205206.0-691316, is extended and coincident with a galaxy cluster visible on an HST image. The X-ray spectrum of the cluster reveals a redshift of z = 0.25 ± 0.02 and a temperature of 3.6±0.4 keV. The redshift was mainly determined by a cluster of Fe XXIV lines between the observed energy range 0.8 - 1.0 keV.

  20. 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.

  1. 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.

  2. THE ACS NEARBY GALAXY SURVEY TREASURY. X. QUANTIFYING THE STAR CLUSTER FORMATION EFFICIENCY OF NEARBY DWARF GALAXIES

    SciTech Connect

    Cook, David O.; Dale, Daniel A.; Seth, Anil C.; Johnson, L. Clifton; Weisz, Daniel R.; Fouesneau, Morgan; Dalcanton, Julianne J.; Olsen, Knut A. G.; Engelbracht, Charles W.

    2012-06-01

    We study the relationship between the field star formation and cluster formation properties in a large sample of nearby dwarf galaxies. We use optical data from the Hubble Space Telescope and from ground-based telescopes to derive the ages and masses of the young (t{sub age} {approx}< 100 Myr) cluster sample. Our data provide the first constraints on two proposed relationships between the star formation rate (SFR) of galaxies and the properties of their cluster systems in the low SFR regime. The data show broad agreement with these relationships, but significant galaxy-to-galaxy scatter exists. In part, this scatter can be accounted for by simulating the small number of clusters detected from stochastically sampling the cluster mass function. However, this stochasticity does not fully account for the observed scatter in our data, suggesting that there may be true variations in the fraction of stars formed in clusters in dwarf galaxies. Comparison of the cluster formation and the brightest cluster in our sample galaxies also provide constraints on cluster destruction models.

  3. The Violent Interstellar Medium of Nearby Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Walter, Fabian

    1999-04-01

    High resolution HI observations of nearby dwarf galaxies (most of which are situated in the M81 group at a distance of about 3.2 Mpc) reveal that their neutral interstellar medium (ISM) is dominated by hole-like features most of which are expanding. A comparison of the physical properties of these holes with the ones found in more massive spiral galaxies (such as M31 and M33) shows that they tend to reach much larger sizes in dwarf galaxies. This can be understood in terms of the galaxy's gravitational potential. The origin of these features is still a matter of debate. In general, young star forming regions (OB-associations) are held responsible for their formation. This picture, however, is not without its critics and other mechanisms such as the infall of high velocity clouds, turbulent motions or even gamma ray bursters have been recently proposed. Here I will present one example of a supergiant shell in IC 2574 which corroborates the picture that OB associations are indeed creating these structures. This particular supergiant shell is currently the most promising case to study the effects of the combined effects of stellar winds and supernova explosions which shape the neutral interstellar medium of (dwarf) galaxies.

  4. MaNGA: Mapping Nearby Galaxies at Apache Point Observatory

    NASA Astrophysics Data System (ADS)

    Bundy, Kevin

    2015-04-01

    I describe a new integral field spectroscopic survey called MaNGA (Mapping Nearby Galaxies at Apache Point Observatory). One of three core programs in the 6-year SDSS-IV project† that began on July 1st, 2014, MaNGA will deploy 17 fiber-bundle IFUs across the Sloan 2.5m Telescope's 3 degree field-of-view, targeting a mass-selected sample with a median redshift of 0.03, typical spatial resolution of 1-2 kpc, and a per-fiber signal-to-noise ratio of 4-8 in the outskirts of target galaxies. For each galaxy in the sample, MaNGA will provide maps and measured gradients of the composition and dynamics of both stars and gas. I discuss early results that highlight MaNGA's potential to shed light on the ionization and chemical enrichment of gas in galaxies, spatial patterns in their star formation histories, and the internal makeup of stellar populations. MaNGA's unprecedented data set will not only provide powerful new insight on galaxy formation and evolution but will serve as a valuable benchmark for future high-z observations from large telescopes and space-based facilities.

  5. EXTENDED HCN AND HCO{sup +} EMISSION IN THE STARBURST GALAXY M82

    SciTech Connect

    Salas, P.; Galaz, G.; Salter, D.; Herrera-Camus, R.; Bolatto, A. D.; Kepley, A.

    2014-12-20

    We mapped 3 mm continuum and line emission from the starburst galaxy M82 using the Combined Array for Research in Millimeter-wave Astronomy. We targeted the HCN, HCO{sup +}, HNC, CS, and HC{sub 3}N lines, but here we focus on the HCN and HCO{sup +} emission. The map covers a field of 1.'2 with an ≈5'' resolution. The HCN and HCO{sup +} observations are short spacings corrected. The molecular gas in M82 had been previously found to be distributed in a molecular disk, coincident with the central starburst, and a galactic scale outflow which originates in the central starburst. With the new short spacings-corrected maps we derive some of the properties of the dense molecular gas in the base of the outflow. From the HCN and HCO{sup +} J = (1-0) line emission, and under the assumptions of the gas being optically thin and in local thermodynamic equilibrium, we place lower limits on the amount of dense molecular gas in the base of the outflow. The lower limits are 7 × 10{sup 6} M {sub ☉} and 21 × 10{sup 6} M {sub ☉}, or ≳ 2% of the total molecular mass in the outflow. The kinematics and spatial distribution of the dense gas outside the central starburst suggests that it is being expelled through chimneys. Assuming a constant outflow velocity, the derived outflow rate of dense molecular gas is ≥0.3 M {sub ☉} yr{sup –1}, which would lower the starburst lifetime by ≥5%. The energy required to expel this mass of dense gas is (1-10) × 10{sup 52} erg.

  6. Extended HCN and HCO+ Emission in the Starburst Galaxy M82

    NASA Astrophysics Data System (ADS)

    Salas, P.; Galaz, G.; Salter, D.; Herrera-Camus, R.; Bolatto, A. D.; Kepley, A.

    2014-12-01

    We mapped 3 mm continuum and line emission from the starburst galaxy M82 using the Combined Array for Research in Millimeter-wave Astronomy. We targeted the HCN, HCO+, HNC, CS, and HC3N lines, but here we focus on the HCN and HCO+ emission. The map covers a field of 1.'2 with an ≈5'' resolution. The HCN and HCO+ observations are short spacings corrected. The molecular gas in M82 had been previously found to be distributed in a molecular disk, coincident with the central starburst, and a galactic scale outflow which originates in the central starburst. With the new short spacings-corrected maps we derive some of the properties of the dense molecular gas in the base of the outflow. From the HCN and HCO+ J = (1-0) line emission, and under the assumptions of the gas being optically thin and in local thermodynamic equilibrium, we place lower limits on the amount of dense molecular gas in the base of the outflow. The lower limits are 7 × 106 M ⊙ and 21 × 106 M ⊙, or >~ 2% of the total molecular mass in the outflow. The kinematics and spatial distribution of the dense gas outside the central starburst suggests that it is being expelled through chimneys. Assuming a constant outflow velocity, the derived outflow rate of dense molecular gas is >=0.3 M ⊙ yr-1, which would lower the starburst lifetime by >=5%. The energy required to expel this mass of dense gas is (1-10) × 1052 erg.

  7. Wide Integral Field Infrared Spectroscopic Survey of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Sivanandam, Suresh; Moon, Dae-Sik; Zaritsky, Dennis F.; Chou, Richard; Meyer, Elliot; Ma, Ke; Jarvis, Miranda; Eisner, Joshua A.

    2015-01-01

    We are constructing a novel infrared integral field spectrograph with a large field of view (~50'x20') that will be available on the Kitt Peak 90' Bok telescope this spring. This wide integral field infrared spectrograph (WIFIS) operates over two wavelength ranges, zJ-band (0.9-1.35 microns) and H-band (1.5-1.8 microns), and has moderate spectral resolving power, 3,000 in zJ-band and 2,200 in H-band, respectively. WIFIS' field-of-view is comparable to current optical integral field spectrographs that are carrying out large galaxy surveys, e.g. SAMI, CALIFA, and MaNGA. We are designing a large nearby galaxy survey to complement the data already been taken by these optical integral field spectroscopic surveys. The near-infrared window provides a sensitive probe of the initial mass functions of stellar populations, the OB stellar fractions in massive star forming regions, and the kinematics of and obscured star formation within merging systems. This will be the first large scale infrared integral field spectroscopic survey of nearby galaxies.

  8. Comparing [C II] , HI, and CO Dynamics of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    de Blok, W. J. G.; Walter, F.; Smith, J.-D. T.; Herrera-Camus, R.; Bolatto, A. D.; Requena-Torres, M. A.; Crocker, A. F.; Croxall, K. V.; Kennicutt, R. C.; Koda, J.; Armus, L.; Boquien, M.; Dale, D.; Kreckel, K.; Meidt, S.

    2016-08-01

    The H i and CO components of the interstellar medium (ISM) are usually used to derive the dynamical mass {M}{{dyn}} of nearby galaxies. Both components become too faint to be used as a tracer in observations of high-redshift galaxies. In those cases, the 158 μm line of atomic carbon ([C ii]) may be the only way to derive {M}{{dyn}}. As the distribution and kinematics of the ISM tracer affects the determination of {M}{{dyn}}, it is important to quantify the relative distributions of H i, CO, and [C ii]. H i and CO are well-characterized observationally, however, for [C ii] only very few measurements exist. Here we compare observations of CO, H i, and [C ii] emission of a sample of nearby galaxies, drawn from the HERACLES, THINGS, and KINGFISH surveys. We find that within R 25, the average [C ii] exponential radial profile is slightly shallower than that of the CO, but much steeper than the H i distribution. This is also reflected in the integrated spectrum (“global profile”), where the [C ii] spectrum looks more like that of the CO than that of the H i. For one galaxy, a spectrally resolved comparison of integrated spectra was possible; other comparisons were limited by the intrinsic line-widths of the galaxies and the coarse velocity resolution of the [C ii] data. Using high-spectral-resolution SOFIA [C ii] data of a number of star forming regions in two nearby galaxies, we find that their [C ii] linewidths agree better with those of the CO than the H i. As the radial extent of a given ISM tracer is a key input in deriving {M}{{dyn}} from spatially unresolved data, we conclude that the relevant length-scale to use in determining {M}{{dyn}} based on [C ii] data, is that of the well-characterized CO distribution. This length scale is similar to that of the optical disk.

  9. The Nuclear Activities of Nearby S0 Galaxies

    NASA Astrophysics Data System (ADS)

    Xiao, Meng-Yuan; Gu, Qiu-Sheng; Chen, Yan-Mei; Zhou, Luwenjia

    2016-11-01

    We present a study of nuclear activities in nearby S0 galaxies. After cross-matching the Sloan Digital Sky Survey Data Release 7 with the Third Reference Catalog of Bright Galaxies (RC3) and visually checking the SDSS images, we derive a sample of 583 S0 galaxies with the central spectrophotometric information. In order to separate nebular emission lines from the underlying stellar contribution, we fit the stellar population model to the SDSS spectra of these S0 galaxies. According to the BPT diagram, we find that 8% of S0 galaxies show central star-forming activity, while the fractions of Seyfert, Composite, and low-ionization nuclear emission-line regions (LINERs) are 2%, 8%, and 21.4%, respectively. We also find that star-forming S0s have the lowest stellar masses, over one magnitude lower than the others, and that the active S0s are mainly located in the sparse environment, while the normal S0s are located in the dense environment, which might suggest that the environment plays an important role in quenching star formation and/or AGN activity in S0 galaxies. By performing bulge-disk decomposition of 45 star-forming S0s in g- and r-bands with the 2D fitting software Galfit, as well as exploiting the catalog of 2D photometric decompositions of Meert et al., we find that the bulges of approximately one-third of star-forming S0 galaxies (16/45) are bluer than their disks, while for other types of S0s the bulge and disk components show similar color distributions. Besides, the Sérsic index of most star-forming S0s bulges is less than two, while for normal S0s, it is between two and six.

  10. Understanding the Structure and Evolution of Nearby Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Zheng, Zheng

    2014-01-01

    In order to understand the structure and evolution of disk galaxies, we studied the stellar and gaseous components as well as the star formation rate in nearby disk galaxies. We used PS1 medium deep survey images to derive five-band (grizy) surface brightness profiles down to 30 ABmag/arcsec^2 for about 700 galaxies. From these stellar mass and mass-to-light ratio radial profiles are derived. The stellar mass radial profiles tend to bend-up at large radii, this often traces an extended old stellar population. The mass-to-light ratio profiles tend to rise outside the r25 radii. We also find a larger fraction of up-bending surface brightness profiles than Polen & Trujillo (2006). This may be because their sample is biased towards low surface brightness galaxies. We used HIPASS data as well as VLA HI 21cm data to study the gas component and dynamics of disk galaxies. We used the GALEX UV images to study the star formation of a HI-selected star-forming sample of about 400 galaxies, compiling a database of FUV and NUV radial profiles and related parameters. We used this to study the star forming efficiency (SFE, star formation rate per unit area divided by gas surface mass density) of the sample galaxies. We found that the UV based SFE has a tighter relationship with HI mass than an H_alpha based SFE as typically used in previous studies and the UV SFE is flat across wide range of stellar mass. We constructed a simple model to predict the distribution of interstellar medium and star formation rate in an equilibrium disk with constant two-fluid Toomre Q. This model can reproduces the SFE relations we derived.

  11. Resolving the Milky Way and Nearby Galaxies with WFIRST

    NASA Astrophysics Data System (ADS)

    Kalirai, Jasonjot

    High-resolution studies of nearby stellar populations have served as a foundation for our quest to understand the nature of galaxies. Today, studies of resolved stellar populations constrain fundamental relations -- such as the initial mass function of stars, the time scales of stellar evolution, the timing of mass loss and amount of energetic feedback, the color-magnitude relation and its dependency on age and metallicity, the stellar-dark matter connection in galaxy halos, and the build up of stellar populations over cosmic time -- that represent key ingredients in our prescription to interpret light from the Universe and to measure the physical state of galaxies. More than in any other area of astrophysics, WFIRST will yield a transformative impact in measuring and characterizing resolved stellar populations in the Milky Way and nearby galaxies. The proximity and level of detail that such populations need to be studied at directly map to all three pillars of WFIRST capabilities - sensitivity from a 2.4 meter space based telescope, resolution from 0.1" pixels, and large 0.3 degree field of view from multiple detectors. Our WFIRST GO Science Investigation Team (F) will develop three WFIRST (notional) GO programs related to resolved stellar populations to fully stress WFIRST's Wide Field Instrument. The programs will include a Survey of the Milky Way, a Survey of Nearby Galaxy Halos, and a Survey of Star-Forming Galaxies. Specific science goals for each program will be validated through a wide range of observational data sets, simulations, and new algorithms. As an output of this study, our team will deliver optimized strategies and tools to maximize stellar population science with WFIRST. This will include: new grids of IR-optimized stellar evolution and synthetic spectroscopic models; pipelines and algorithms for optimal data reduction at the WFIRST sensitivity and pixel scale; wide field simulations of MW environments and galaxy halos; cosmological simulations

  12. An extremely prolific supernova factory in the buried nucleus of the starburst galaxy IC 694

    NASA Astrophysics Data System (ADS)

    Pérez-Torres, M. A.; Romero-Cañizales, C.; Alberdi, A.; Polatidis, A.

    2009-11-01

    Context: The central kiloparsec of many local uminous infrared galaxies are known to host intense bursts of massive star formation, leading to numerous explosions of core-collapse supernovae (CCSNe). However, the dust-enshrouded regions where those supernovae explode hamper their detection at optical and near-infrared wavelengths. Aims: We investigate the nuclear region of the starburst galaxy IC 694 (=Arp 299-A) at radio wavelengths, aimed at discovering recently exploded CCSNe, as well as determining their rate of explosion, which carries crucial information about star formation rates, the initial mass function, and the starburst processes in action. Methods: We use the electronic European VLBI Network to image with milliarcsecond resolution the 5.0 GHz compact radio emission of the innermost nuclear region of IC 694. Results: Our observations detect a rich cluster of 26 compact radio emitting sources in the central 150 pc of the nuclear starburst in IC 694. The high brightness temperatures observed for the compact sources are indicative of a non-thermal origin for the observed radio emission, implying that most, if not all, of those sources are young radio supernovae (RSNe) and supernova remnants (SNRs). We find evidence of at least three relatively young, slowly evolving, long-lasting RSNe (A0, A12, and A15) that appear to have unusual properties, suggesting that the conditions in the local circumstellar medium (CSM) play a significant role in determining the radio behaviour of expanding SNe. Their radio luminosities are typical of normal RSNe, which result from the explosion of type IIP/b and type IIL SNe. All of these results provide support for a recent (less than 10-15 Myr) instantaneous starburst in the innermost regions of IC 694. Tables 1, 2 and Appendix are only available in electronic form at http://www.aanda.org

  13. Observations of the impact of starbursts on the interstellar medium in dwarf galaxies

    NASA Technical Reports Server (NTRS)

    Marlowe, Amanda T.; Heckman, Timothy M.; Wyse, Rosemary F. G.; Schommer, Robert

    1995-01-01

    Dwarf galaxies play a crucial role in our understanding of the formation and evolution of galaxies, and the concept of supernova-driven mass outflows is a vital ingredient in theories of the structure and evolution of dwarf galaxies. Despite the theoretical importance of these outflows, there is a very limited amount of direct observational evidence for their existence. We have therefore begun a detailed multi-wave-band search for outflows in dwarf (M(sub B) greater than or = -18) galaxies with extensive recent or ongoing centrally concentrated star formation. We report the first results of this search in the present paper. Observations of the ionized gas in dwarf amorphous galaxies with centrally concentrated populations of massive stars provide evidence for the large-scale expansion of their expansion of their ionized interstellar media. Fabry-Perot H alpha images reveal the presence of kiloparsec-scale 'superbubbles' and filaments which tend to be oriented along the galaxy minor axis. These structures are comparable in size to the chracteristic optical sizes of the galaxies, and dominate the morphology of the galaxies at low surface brightness in H alpha. Since expanding structure of this size and velocity are not observed in all low-mass galaxies with recent or ongoing star formation, we suggest that we are witnessing transient events that likely have a relatively low 'duty cycle' in such galaxies. That is, we argue that the particular galaxies in the present paper have had significantly elevated star formation rates over the past 10(exp 7)-10(exp 8) yr (i.e., these are starburst or young poststarburst systems). This interpretation is consistent with the optical colors and emission-line properties of these galaxies.

  14. Full stellar kinematical profiles of central parts of nearby galaxies

    NASA Astrophysics Data System (ADS)

    Vudragović, A.; Samurović, S.; Jovanović, M.

    2016-09-01

    Context. We present the largest catalog of detailed stellar kinematics of the central parts of nearby galaxies, which includes higher moments of the line-of-sight velocity distribution (LOSVD) function represented by the Gauss-Hermite series. The kinematics is measured on a sample of galaxies selected from the Arecibo Legacy Fast ALFA (Alfalfa) survey using spectroscopy from the Sloan Digital Sky Survey (SDSS DR7). Aims: The SDSS DR7 offers measurements of the LOSVD based on the assumption of a pure Gaussian shape of the broadening function caused by the combination of rotational and random motion of the stars in galaxies. We discuss the consequences of this oversimplification since the velocity dispersion, one of the measured quantities, often serves as the proxy to important modeling parameters such as the black-hole mass and the virial mass of galaxies. Methods: The publicly available pPXF code is used to calculate the full kinematical profile for the sample galaxies including higher moments of their LOSVD. Both observed and synthetic stellar libraries were used and the related template mismatch problem is discussed. Results: For the whole sample of 2180 nearby galaxies reflecting morphological distribution characteristic for the local Universe, we successfully recovered stellar kinematics of their central parts, including higher order moments of the LOSVD function, for signal-to-noise above 50. Conclusions: We show the consequences of the oversimplification of the LOSVD function with Gaussian function on the velocity dispersion for the empirical and the synthetic stellar library. For the empirical stellar library, this approximation leads to an increase in the virial mass of 13% on average, while for the synthetic library the effect is weaker, with an increase of 9% on average. Systematic erroneous estimates of the velocity dispersion comes from the use of the synthetic stellar library instead of the empirical one and is much larger than the value imposed by

  15. Testing the THINGS Star Formation Law in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Meurer, Gerhardt R.; Zheng, Z.; Zwaan, M.; Knezek, P.

    2010-01-01

    The star formation law (SFL) is an essential tool for understanding galaxy evolution. However, the star formation process is not well understood and the broadly used Schmidt-Kennicutt SFL is based on a biased sample of bright nearby spirals. Here we derive a star formation recipe based on the THINGS SFL of Leroy et. al (2008) and Bigiel et al.(2009), which can predict the star formation rate using the rotation curve and stellar mass profile as an input. We use optical and radio rotation curves combined with optical broad band images of HI selected galaxies to make predicted star formation profiles using this prescription which are then compared to our UV and H-alpha images from the SINGG and SUNGG surveys. We look at how the predictions compare to the observations in the two different tracers especially in the outer disks which were not accounted for when the THINGS SFL was derived.

  16. Nearby Galaxy is a Hotbed of Star Birth Activity

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This new image taken with NASA's Hubble Space Telescope (HST) is of the nearby dwarf galaxy NGC 1569. This galaxy is a hotbed of vigorous star birth activity which blows huge bubbles that riddle its main body. The bubble structure is sculpted by the galactic super-winds and outflows caused by a colossal input of energy from collective supernova explosions that are linked with a massive episode of star birth. The bubbles seen in this image are made of hydrogen gas that glows when hit by the fierce wind and radiation from hot young stars and is racked by supernova shocks. Its 'star factories' are also manufacturing brilliant blue star clusters. NGC 1569 had a sudden onset of star birth about 25 million years ago, which subsided about the time the very earliest human ancestors appeared on Earth. The Marshall Space Flight Center had responsibility for the design, development, and construction of the HST.

  17. The Environment of X-Ray Binaries in the Dwarf Starburst Galaxy NGC 1569

    NASA Astrophysics Data System (ADS)

    Clark, David M.; Eikenberry, Stephen S.; Raines, Steven N.

    2008-05-01

    We use deep, J and Ks observations of NGC 1569 acquired with FLAMINGOS on the KPNO 4-m to search for star cluster counterparts to X-ray binaries identified in archived Chandra images of this dwarf starburst galaxy. Performing near-IR photometry on the star cluster counterparts, we determine their colors, luminosities and masses. Comparing these results to the properties for all clusters in this galaxy, we search for trends in clusters associated with X-ray sources. Combining this study with FISICA, near-IR spectral observations, we further characterize the surroundings to X-ray binaries in NGC 1569. Contrasting this work with findings from a similar study performed on the Antennae galaxies, a large, merging system, we investigate the differences in X-ray binary environments.

  18. The Red and Featureless Outer Disks of Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Watkins, Aaron E.; Mihos, J. Christopher; Harding, Paul

    2016-07-01

    We present results from deep, wide-field surface photometry of three nearby (D = 4-7 Mpc) spiral galaxies: M94 (NGC 4736), M64 (NGC 4826), and M106 (NGC 4258). Our imaging reaches a limiting surface brightness of {μ }B ˜ 28-30 mag arcsec-2 and probes colors down to {μ }B ˜ 27.5 mag arcsec-2. We compare our broadband optical data to available ultraviolet and high column density H i data to better constrain the star-forming history and stellar populations of the outermost parts of each galaxy’s disk. Each galaxy has a well-defined radius beyond which little star formation occurs and the disk light appears both azimuthally smooth and red in color, suggestive of old, well-mixed stellar populations. Given the lack of ongoing star formation or blue stellar populations in these galaxies’ outer disks, the most likely mechanisms for their formation are dynamical processes such as disk heating or radial migration, rather than inside-out growth of the disks. This is also implied by the similarity in outer disk properties despite each galaxy showing distinct levels of environmental influence, from a purely isolated galaxy (M94) to one experiencing weak tidal perturbations from its satellite galaxies (M106) to a galaxy recovering from a recent merger (M64), suggesting that a variety of evolutionary histories can yield similar outer disk structure. While this suggests a common secular mechanism for outer disk formation, the large extent of these smooth, red stellar populations—which reach several disk scale lengths beyond the galaxies’ spiral structure—may challenge models of radial migration given the lack of any nonaxisymmetric forcing at such large radii.

  19. Deep photometry and integral magnitudes of 8 nearby galaxies

    NASA Astrophysics Data System (ADS)

    Georgiev, Ts. B.

    2016-02-01

    We estimated integral magnitudes of galaxies trying to include the contribution of the brightest part of their halos. We performed surface photometry based on (i) concentric elliptical rims, corresponding to the peripheral ellipticity of the image, (ii) median estimation of the mean value of the rim pixels, (iii) apparent radial brightness profiles, corresponding to the rim medians, and (iv) magnitude curves of growth, derived by numerical integrations of the apparent rim profiles, without preliminary background estimation and removal. Furthermore, we used the magnitude curves of growth to determine the integral magnitudes (limited by size and deepness of our frames) and compared them with the total magnitudes in the data base HyperLeda. Also, we used the rim-profiles to estimate the background level far enough from the galaxy center and we build (here—only for trial) the intrinsic radial profiles (with background removal). We apply this photometry on 8 nearby galaxies, observed with CCD in the system BVRC IC by the 50 cm Schmidt telescope of the Rozhen NAO in 2003-2004. We build radial profiles which occur to be as average 1.8 times (1.2-2.5 times) larger than in data base NED and of integral brightness that occurs to be about 1.4 times (1.2-1.7 times) higher than in data base HyperLeda. The relative brightness additions, found here, correlate with the color index and anti-correlate with the luminosity of the galaxy.

  20. HI Emission in Nearby X-ray Detected Active Galaxies

    NASA Astrophysics Data System (ADS)

    George, Erin; Winter, L. M.; Zauderer, B.; Darling, J.; Koss, M.

    2013-01-01

    We have measured HI profiles in 96 nearby, active galaxies using the 100-meter Green Bank Telescope (GBT). Our sources contain active galactic nuclei (AGN) detected in the hard X-ray (14-195 keV) from Swift Gamma-ray Burst satellite’s Burst Alert Telescope (BAT) 22-month survey. This survey is unique because the sources were detected in the hard X-ray, allowing us to include galaxies that are otherwise obscured in other bands. The HI profiles we gathered are combined with the published optical, infrared, and X-ray data. We present the systemic velocities, outflow velocities, and cold gas mass in the sources. The mass of the cold gas is compared to the luminous mass in stars in order to find clues to unlock the nature of the host galaxies. A comparison of HI with the bolometric luminosity of the AGN is made. Our observations examine how the reservoir of cold gas is correlated with luminosity, as well. Through these data, we look for evolutionary differences in host galaxy types in order to understand how super massive black holes are fueled.

  1. Observations of Cold Dust in Nearby Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Leeuw, Lerothodi L.; Sansom, Anne E.; Robson, E. Ian; Haas, Martin; Kuno, Nario

    2004-09-01

    Spectral energy distribution (SED) analyses that include new millimeter to far-infrared (FIR) observations obtained with continuum instruments on the Nobeyama and James Clerk Maxwell Telescopes and the Infrared Space Observatory are presented for seven nearby (<45 Mpc) FIR-bright elliptical galaxies. These are analyzed together with archival FIR and shortwave radio data obtained from the NASA/IPAC Extragalactic Database (NED). The radio to infrared SEDs are best-fitted by power law plus graybody models of dust residing in the central galactic regions within a 2.4 kpc diameter and with temperatures between ~21 and 28 K, emissivity index ~=2, and masses from ~1.6 to 19×105Msolar. The emissivity index is consistent with dust constituting amorphous silicate and carbonaceous grains previously modeled for stellar-heated dust observed in the Galaxy and other nearby extragalactic sources. Using updated dust absorption coefficients for this type of dust, dust masses are estimated that are similar to those determined from earlier FIR data alone, even though the latter results implied hotter dust temperatures. Fluxes and masses that are consistent with the new FIR and submillimeter data are estimated for dust cooler than 20 K within the central galactic regions. Tighter physical constraints for such cold, diffuse dust (if it exists) with low surface brightness will need sensitive FIR to submillimeter observations with the Spitzer Space Telescope, SCUBA2, or ALMA.

  2. Black holes at the centers of nearby dwarf galaxies

    SciTech Connect

    Moran, Edward C.; Shahinyan, Karlen; Sugarman, Hannah R.; Vélez, Darik O.; Eracleous, Michael

    2014-12-01

    Using a distance-limited portion of the Sloan Digital Sky Survey (SDSS) Data Release 7, we have identified 28 active galactic nuclei (AGNs) in nearby (d⩽80 Mpc) low-mass, low-luminosity dwarf galaxies. The accreting objects at the galaxy centers are expected to be intermediate-mass black holes (IMBHs) with M{sub BH}⩽10{sup 6} M{sub ⊙}. The AGNs were selected using several optical emission-line diagnostics after careful modeling of the continuum present in the spectra. We have limited our survey to objects with spectral characteristics similar to those of Seyfert nuclei, excluding emission-line galaxies with ambiguous spectra that could be powered by stellar processes. Thus, as a set, the host galaxies in our sample are the least massive objects in the very local universe certain to contain central black holes. Our sample is dominated by narrow-line (type 2) AGNs, and it appears to have a much lower fraction of broad-line objects than that observed for luminous, optically selected Seyfert galaxies. Given our focus on the nearest objects included in the SDSS, our survey is more sensitive to low-luminosity emission than previous optical searches for AGNs in low-mass galaxies. The [O iii] λ5007 luminosities of the Seyfert nuclei in our sample have a median value of L{sub 5007}=2×10{sup 5} L{sub ⊙} and extend down to ∼10{sup 4} L{sub ⊙}. Using published data for broad-line IMBH candidates, we have derived an [O iii] bolometric correction of log(L{sub bol}/L{sub 5007})=3.0±0.3, which is significantly lower than values obtained for high-luminosity AGNs. Applying this correction to our sample, we obtain minimum black hole mass estimates that fall mainly in the 10{sup 3} M{sub ⊙}–10{sup 4} M{sub ⊙} range, which is roughly where the predicted mass functions for different black hole seed formation scenarios overlap the most. In the stellar mass range that includes the bulk of the AGN host galaxies in our sample, we derive a lower limit on the AGN fraction

  3. Lyman Alpha Emitting Galaxies in the Nearby Universe

    NASA Astrophysics Data System (ADS)

    Hayes, Matthew

    2015-07-01

    The Lyman alpha emission line (Lyα) of neutral hydrogen (Hi) is intrinsically the brightest emission feature in the spectrum of astrophysical nebulae, making it a very attractive observational feature with which to survey galaxies. Moreover as an ultraviolet resonance line, Lyα possesses several unique characteristics that make it useful to study the properties of the interstellar medium and ionising stellar population at all cosmic epochs. In this review, I present a summary of Lyα observations of galaxies in the nearby universe. By ultraviolet continuum selection, at the magnitudes reachable with current facilities, only ≈ 5% of the local galaxy population shows a Lyα equivalent width (W Lyα) that exceeds 20 Å. This fraction increases dramatically at higher redshifts, but only in the local universe can we study galaxies in detail and assemble unprecedented multi-wavelength datasets. I discuss many local Lyα observations, showing that when galaxies show net Lyα emission, they ubiquitously also produce large-scale halos of scattered Lyα, that dominate the integrated luminosity. Concerning global measurements, we discuss how W Lyα and the Lyα escape fraction (f Lyα esc) are higher (W Lyα ≳ 20 Å and f Lyα esc ≳ 10%) in galaxies that represent the less massive and younger end of the distribution for local objects. This is connected with various properties, such that Lyα-emitting galaxies have lower metal abundances (median value of 12 + log(O/H) ~ 8.1) and dust reddening. However, the presence of galactic outflows/winds is also vital to Doppler shift the Lyα line out of resonance with the atomic gas, and high W Lyα is found only among galaxies with winds faster than ~ 50 km s-1. The empirical evidence is then assembled into a coherent picture, and the requirement for star-formation-driven feedback is discussed in the context of an evolutionary sequence where the interstellar medium is accelerated and/or subject to hydrodynamical instabilities

  4. Cold Galaxies on FIRE: Modeling the Most Luminous Starbursts in the Universe with Cosmological Zoom Simulations

    NASA Astrophysics Data System (ADS)

    Narayanan, Desika

    2014-10-01

    As the most luminous, heavily star-forming galaxies in the Universe, Submillimeter Galaxies at z 2-4 are key players in galaxy evolution. Since their discovery, SMGs have received significant attention from HST in characterizing their physical morphology, stellar masses, and star formation histories. Unfortunately, these physical constraints have been difficult for theorists to reconcile with galaxy formation simulations. Previous generations of simulations have all either {a} neglected baryons; {b} neglected radiative transfer {and connecting to observations}; or {c} neglected cosmological conditions. Here, we propose to conduct the first ever cosmological hydrodynamic simulations of Submillimeter Galaxy formation that couple with bona fide 3D dust radiative transfer calculations. These ultra-high resolution simulations {parsec-scale} will be the first to resolve the sites of dust obscuration, the cosmic growth history of SMGs, and their evolutionary destiny. Our proposal has two principle goals: {1} Develop the first ever model for SMG formation from cosmological simulations that include both baryons and dust radiative transfer; {2} Capitalize on our parsec-scale resolution to understand the connection between the physical properties of star-forming regions in high-z starbursts, and recent IMF constraints from present-epoch massive galaxies.

  5. The Evolution of Main-Sequence and Starburst Galaxies Across Cosmic Time

    NASA Astrophysics Data System (ADS)

    Aravena, Manuel

    2015-08-01

    In the last decade, significant progress has been achieved in the understanding of the evolution of star formation in galaxies as a function of redshift. Its is now clear that the majority of galaxies at z<3 form a nearly linear correlation between their stellar mass and star formation rates and appear to create most of their stars in timescales of ~1 Gyr. At the highest luminosities, a significant fraction of galaxies deviate from this ‘main-sequence’, showing short duty cycles and thus producing most of their stars in a single burst of star formation (‘starburst’) within a few 100 Myr, being likely driven by major merger activity. Despite the large luminosities of starbursts, main-sequence galaxies appear to dominate the star formation density of the Universe at its peak.While progress has been impressive, a number of questions are still unanswered. In this talk, I will review our current observational understanding of this ‘main-sequence’ vs ‘starburst’ galaxy paradigm, and will address how future observations (e.g. with ALMA) will help us to have better insights into the fundamental properties of these galaxies.

  6. EVOLUTION OF THE HIGH-MASS END OF THE STELLAR INITIAL MASS FUNCTIONS IN STARBURST GALAXIES

    SciTech Connect

    Bekki, Kenji; Meurer, Gerhardt R.

    2013-03-01

    We investigate the time evolution and spatial variation of the stellar initial mass function (IMF) in star-forming disk galaxies by using chemodynamical simulations with an IMF model depending both on local densities and metallicities ([Fe/H]) of the interstellar medium (ISM). We find that the slope ({alpha}) of a power-law IMF (N(m){proportional_to}m {sup -{alpha}}) for stellar masses larger than 1 M{sub Sun} evolves from the canonical Salpeter IMF ({alpha} Almost-Equal-To 2.35) to be moderately top-heavy one ({alpha} Almost-Equal-To 1.9) in the simulated disk galaxies with starbursts triggered by galaxy interaction. We also find that {alpha} in star-forming regions correlates with star formation rate densities ({Sigma}{sub SFR} in units of M{sub Sun} yr{sup -1} kpc{sup -2}). Feedback effects of Type Ia and II supernovae are found to prevent IMFs from being too top-heavy ({alpha} < 1.5). The simulation predicts {alpha} Almost-Equal-To 0.23log {Sigma}{sub SFR} + 1.7 for log {Sigma}{sub SFR} {>=} -2 (i.e., more top-heavy in higher {Sigma}{sub SFR}), which is reasonably consistent with corresponding recent observational results. The present study also predicts that inner regions of starburst disk galaxies have smaller {alpha} and thus are more top-heavy (d{alpha}/dR {approx} 0.07 kpc{sup -1} for R {<=} 5 kpc). The predicted radial {alpha} gradient can be tested against future observational studies of the {alpha} variation in star-forming galaxies.

  7. A high-dispersion molecular gas component in nearby galaxies

    SciTech Connect

    Caldú-Primo, Anahi; Walter, Fabian; Sandstrom, Karin; Schruba, Andreas; Leroy, Adam; De Blok, W. J. G.; Ianjamasimanana, R.; Mogotsi, K. M.

    2013-12-01

    We present a comprehensive study of the velocity dispersion of the atomic (H I) and molecular (H{sub 2}) gas components in the disks (R ≲ R {sub 25}) of a sample of 12 nearby spiral galaxies with moderate inclinations. Our analysis is based on sensitive high-resolution data from the THINGS (atomic gas) and HERACLES (molecular gas) surveys. To obtain reliable measurements of the velocity dispersion, we stack regions several kiloparsecs in size, after accounting for intrinsic velocity shifts due to galactic rotation and large-scale motions. We stack using various parameters: the galactocentric distance, star formation rate surface density, H I surface density, H{sub 2} surface density, and total gas surface density. We fit single Gaussian components to the stacked spectra and measure median velocity dispersions for H I of 11.9 ± 3.1 km s{sup –1} and for CO of 12.0 ± 3.9 km s{sup –1}. The CO velocity dispersions are thus, surprisingly, very similar to the corresponding ones of H I, with an average ratio of σ{sub HI}/σ{sub CO}= 1.0 ± 0.2 irrespective of the stacking parameter. The measured CO velocity dispersions are significantly higher (factor of ∼2) than the traditional picture of a cold molecular gas disk associated with star formation. The high dispersion implies an additional thick molecular gas disk (possibly as thick as the H I disk). Our finding is in agreement with recent sensitive measurements in individual edge-on and face-on galaxies and points toward the general existence of a thick disk of molecular gas, in addition to the well-known thin disk in nearby spiral galaxies.

  8. Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies: II. Control of the H II Region Parameters

    SciTech Connect

    Dopita, M A; Fischera, J; Sutherland, R S; Kewley, L J; Tuffs, R J; Popescu, C C; van Breugel, W; Groves, B A; Leitherer, C

    2006-03-01

    We examine from a theoretical viewpoint how the physical parameters of H II regions are controlled both in normal galaxies and in starburst environments. These parameters are the H II region luminosity function, the time-dependent size, the covering fraction of molecular clouds, the pressure in the ionized gas and the ionization parameter. The factors which control them are the initial mass function of the exciting stars, the cluster mass function, the metallicity and the mean pressure in the surrounding interstellar medium. We investigate the sensitivity of the H{alpha} luminosity to the IMF, and find that this can translate to about 30% variation in derived star formation rates. The molecular cloud dissipation timescale is estimated from a case study of M17 to be {approx} 1 Myr. Based upon H II luminosity function fitting for nearby galaxies, we propose that the cluster mass function has a log-normal form peaking at {approx} 185M{sub {circle_dot}}. This suggests that the cluster mass function is the continuation of the stellar IMF to higher mass. The pressure in the H II regions is controlled by the mechanical luminosity flux from the central cluster. Since this is closely related to the ionizing photon flux, we show that the ionization parameter is not a free variable, and that the diffuse ionized medium may be composed of many large, faint and old H II regions. Finally, we derive theoretical probability distributions for the ionization parameter as a function of metallicity and compare these to those derived for SDSS galaxies.

  9. Models of the Cartwheel ring galaxy: Spokes and starbursts

    NASA Technical Reports Server (NTRS)

    Struck-Marcell, Curtis

    1993-01-01

    Recent observations of this famous ring galaxy, including optical and near-infrared CCD surface photometry, and VLA radio continuum and 21 cm line mapping (Higdon 1992b, in prep.), have inspired a renewed modeling effort. Toomre's (1978, in The Large-scale Structure of the Universe, eds. Longair and Einasto) series of restricted three-body simulations demonstrated how the multiple rings could be produced in a nearly head-on galaxy collision. New models with a halo-dominated potential based on the 21 cm rotation curve are able to reproduce such details as the spacing between rings, ring widths, offset of the nucleus, and several kinematical features, thus providing strong support for the collisional theory. The new observations have shown there are little or no old stars in Cartwheel; it may consist almost entirely of gas and stars produced as a result of compression in the ring wave. To model this process Smooth Particle Hydrodynamics (SPH) simulations of the Cartwheel disk have been performed. Fixed gravitational potentials were used to represent the Cartwheel and a roughly 30 percent mass collision partner. The interaction dynamics was treated as in the usual restricted three-body approximation, and the effects of local self-gravity between disk particles were calculated. We are particularly interested in testing the theory that enhanced star formation in waves is the result of gravitational instability in the compressed region (see e.g. Kennicutt 1989, ApJ 344, 685). The gas surface density in a number of simulations was initialized to a value slightly below the threshold for local gravitational instability throughout most of the disk. The first ring wave produces relatively modest compressions (a factor of order a few), triggering instability in a narrow range of wavelengths. Self-gravity in the disk is calculated over a comparable range of scales. Simulations were run with isothermal, adiabatic, and adiabatic with radiative cooling characterized by a

  10. Starburst galaxies in the COSMOS field: clumpy star-formation at redshift 0 < z < 0.5

    NASA Astrophysics Data System (ADS)

    Hinojosa-Goñi, R.; Muñoz-Tuñón, C.; Méndez-Abreu, J.

    2016-08-01

    Context. At high redshift, starburst galaxies present irregular morphologies with 10-20% of their star formation occurring in giant clumps. These clumpy galaxies are considered the progenitors of local disk galaxies. To understand the properties of starbursts at intermediate and low redshift, it is fundamental to track their evolution and the possible link with the systems at higher z. Aims: We present an extensive, systematic, and multiband search and analysis of the starburst galaxies at redshift (0 < z < 0.5) in the COSMOS field, as well as detailed characteristics of their star-forming clumps by using Hubble Space Telescope/Advance Camera for Surveys (HST/ACS) images. Methods: The starburst galaxies are identified using a tailor-made intermediate-band color excess selection, tracing the simultaneous presence of Hα and [OIII] emission lines in the galaxies. Our methodology uses previous information from the zCOSMOS spectral database to calibrate the color excess as a function of the equivalent width of both spectral lines. This technique allows us to identify 220 starburst galaxies at redshift 0 < z < 0.5 using the SUBARU intermediate-band filters. Combining the high spatial resolution images from the HST/ACS with ground-based multi-wavelength photometry, we identify and parametrize the star-forming clumps in every galaxy. Their principal properties, sizes, masses, and star formation rates are provided. Results: The mass distribution of the starburst galaxies is remarkably similar to that of the whole galaxy sample with a peak around M/M⊙ ~ 2 × 108 and only a few galaxies with M/M⊙ > 1010. We classify galaxies into three main types, depending on their HST morphology: single knot (Sknot), single star-forming knot plus diffuse light (Sknot+diffuse), and multiple star-forming knots (Mknots/clumpy) galaxy. We found a fraction of Mknots/clumpy galaxy fclumpy = 0.24 considering out total sample of starburst galaxies up to z ~ 0.5. The individual star

  11. MAPPING DUST THROUGH EMISSION AND ABSORPTION IN NEARBY GALAXIES

    SciTech Connect

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

    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 {approx}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 A{sub V} measures to infer global dust properties.

  12. High-Velocity Clouds and Superbubbles in Nearby Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Schulman, Eric

    1996-05-01

    The galactic fountain model predicts that energetic stellar winds and supernovae in OB associations produce superbubbles containing hot gas that breaks out of the Galactic disk, cools radiatively as it rises upward, and recombines and returns to the disk ballistically. The hot (T ~ 10^6 K) gas can be observed with X-ray telescopes, while the cool returning neutral hydrogen (H I) is detectable as 21 cm emission from high-velocity clouds (HVCs). In the Milky Way Galaxy, a combination of infalling material tidally torn from the Magellanic Clouds and a galactic fountain can explain the high-velocity clouds that cover about 10% of the sky down to a column density of 2 to 3 X 10^18 cm^-2. Sensitive H I observations of nearby disk galaxies were performed with the Arecibo 305 m radio telescope to search for and measure the mass of HVCs in other galaxies. Ten of 14 galaxies have high-velocity wings that can be modeled as arising from a component of galactic gas with a velocity dispersion of 30 or 50 km s^-1. The HVC mass for the 10 galaxies ranges from 6 X 10^7 solar mass to 4 X 10^9 solar mass, which corresponds to 4 to 14% of the total H I in the galaxies. This is the first survey to search for HVCs in more than a few galaxies, and the results imply that Galactic HVCs are a disk-wide phenomenon with a characteristic distance of 10 to 20 kpc, containing a substantial fraction (~10%) of the neutral hydrogen in the Galaxy and much of the random kinetic energy in neutral gas. 21 cm synthesis imaging of UGC 12732 and NGC 5668, performed with the Very Large Array, confirmed the Arecibo results that the former does not have high-velocity gas while the latter does. Two components of high-velocity gas are present in NGC~5668; one may be from an accretion event, while the other is visible due to the increased H I velocity dispersion throughout the optical disk and may be galactic fountain gas. Neither of these components are visible in the observations of UGC 12732, and this galaxy

  13. The history of star formation in nearby dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Weisz, Daniel Ray

    2010-11-01

    We present detailed analysis of color-magnitude diagrams (CMDs) of resolved stellar populations in nearby dwarf galaxies based on observations taken with the Hubble Space Telescope (HST). From the positions of individual stars on a CMD, we are able to derive the star formation histories (SFHs), i.e., the star formation rate (SFR) as a function of time and metallicity, of the observed stellar populations. Specifically, we apply this technique to a number of nearby dwarf galaxies to better understand the mechanisms driving their evolution. The ACS Nearby Galaxy Survey Treasury program (ANGST) provides multi-color photometry of resolved stars in ˜ 60 nearby dwarf galaxies from images taken with HST. This sample contains 12 dSph, 5 dwarf spiral, 28 dIrr, 12 dSph/dIrr (transition), and 3 tidal dwarf galaxies. The sample spans a range of ˜ 10 in MB and covers a wide range of environments, from highly interacting to truly isolated. From the best fit lifetime SFHs we find three significant results: (1) the average dwarf galaxy formed ˜ 60% of its stars by z ˜ 2 and 70% of its stars by z ˜ 1, regardless of morphological type, (2) the only statistically significant difference between the SFHs of different morphological types is within the most recent 1 Gyr (excluding tidal dwarf galaxies), and (3) the SFHs are complex and the mean values are inconsistent with simple SFH models, e.g., single epoch SF or constant SFH. We then present the recent ( ≲ 1 Gyr) SFHs of nine M81 Group Dwarf Galaxies. Comparing the SFHs, birthrate parameters, fraction of stars formed per time interval, and spatial distribution of stellar components as a function of luminosity, we find only minor differences in SF characteristics among the M81 Group dIs despite a wide range of physical properties. We extend our comparison to select dIs in the Local Group (LG), with similar quality photometry, and again find only minor differences in SF parameters. The lack of a clear trend in SF parameters over

  14. The history of star formation in nearby dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Weisz, Daniel Ray

    2010-11-01

    We present detailed analysis of color-magnitude diagrams (CMDs) of resolved stellar populations in nearby dwarf galaxies based on observations taken with the Hubble Space Telescope (HST). From the positions of individual stars on a CMD, we are able to derive the star formation histories (SFHs), i.e., the star formation rate (SFR) as a function of time and metallicity, of the observed stellar populations. Specifically, we apply this technique to a number of nearby dwarf galaxies to better understand the mechanisms driving their evolution. The ACS Nearby Galaxy Survey Treasury program (ANGST) provides multi-color photometry of resolved stars in ˜ 60 nearby dwarf galaxies from images taken with HST. This sample contains 12 dSph, 5 dwarf spiral, 28 dIrr, 12 dSph/dIrr (transition), and 3 tidal dwarf galaxies. The sample spans a range of ˜ 10 in MB and covers a wide range of environments, from highly interacting to truly isolated. From the best fit lifetime SFHs we find three significant results: (1) the average dwarf galaxy formed ˜ 60% of its stars by z ˜ 2 and 70% of its stars by z ˜ 1, regardless of morphological type, (2) the only statistically significant difference between the SFHs of different morphological types is within the most recent 1 Gyr (excluding tidal dwarf galaxies), and (3) the SFHs are complex and the mean values are inconsistent with simple SFH models, e.g., single epoch SF or constant SFH. We then present the recent ( ≲ 1 Gyr) SFHs of nine M81 Group Dwarf Galaxies. Comparing the SFHs, birthrate parameters, fraction of stars formed per time interval, and spatial distribution of stellar components as a function of luminosity, we find only minor differences in SF characteristics among the M81 Group dIs despite a wide range of physical properties. We extend our comparison to select dIs in the Local Group (LG), with similar quality photometry, and again find only minor differences in SF parameters. The lack of a clear trend in SF parameters over

  15. Hot plasma and black hole binaries in starburst galaxy M82.

    PubMed

    Griffiths, R E; Ptak, A; Feigelson, E D; Garmire, G; Townsley, L; Brandt, W N; Sambruna, R; Bregman, J N

    2000-11-17

    High-resolution x-ray observations of the prototype starburst galaxy Messier 82 (M82) obtained with the advanced CCD (charge-coupled device) imaging spectrometer on board the Chandra X-ray Observatory provide a detailed view of hot plasma and energetic processes. Plasma with temperature of about 40,000,000 kelvin fills the inner 1 kiloparsec, which is much hotter than the 1,000,000 to 2,000,000 kelvin interstellar medium component in the Milky Way Galaxy. Produced by many supernova explosions, this central region is overpressurized and drives M82's prominent galactic wind into the intergalactic medium. We also resolved about 20 compact x-ray sources, many of which could be high-mass x-ray binary star systems containing black holes.

  16. ASCA Observation of Bright X-Ray Sources in the Nearby Spiral Galaxy IC 342

    NASA Astrophysics Data System (ADS)

    Okada, Kyoko; Dotani, Tadayasu; Makishima, Kazuo; Mitsuda, Kazuhisa; Mihara, Tatehiro

    1998-02-01

    X-ray observations of the nearby starburst galaxy IC 342 with ASCA led to the detection of three bright X-ray sources, whose positions are consistent with those from the Einstein and ROSAT observations. The X-ray luminosities of the two sources exceed the Eddington limit of a 1.4MO object by two orders of magnitude for an assumed distance of 4.5 Mpc. The brightest one (source 1) among the three exhibited significant time variations on a time scale of a few hours during the ASCA observation. Thus, the size of the emission region must be smaller than about 10(14) cm. The energy spectrum of the source can be represented either by a power-law with an exponential roll-over, or by an optically thick accretion disk model with a maximum color temperature of 1.77 keV. Although the large luminosity of source 1 may be explained by a ~ 100MO black hole at 4.5 Mpc, the observed energy spectrum is too hard to be accounted for by an optically thick accretion disk around the black hole. Ifsource1 is a relativistic jet source with strong X-ray beaming, both the large luminosity and the hard X-ray spectrum can be explained.

  17. Millimeter Detection of Spitzer-selected High Redshift Hyperluminus Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Lonsdale, Carol J.; Omont, A.; del Carmen Polletta, M.; Zylka, R.; Shupe, D.; Smith, H. E., Jr.; Berta, S.; Bavouzet, N.; Lagache, G.; Farrah, D.; Bertoldi, F.; Cox, P.; de Breuck, C.; Dole, H.; Lutz, D.; Tacconi, L.; Perez-Fournon, I.; Aussel, H.; McCracken, H.; Clements, D.; Rowan-Robinson, M.; Franceschini, A.; Frayer, D.; Surace, J.; Siana, B.

    2006-12-01

    We have used the Mambo instrument on the IRAM 30m telescope to observe at 1.2mm 63 Spitzer-selected z>1 hyperluminous infrared galaxy candidates (HLIRGs) with starburst-dominated mid-infrared (MIR) spectral energy distributions from the SWIRE Legacy survey. The primary selection criteria are a peak in the IRAC 5.8μm band due to the rest frame near-infrared spectrum of evolved stars, a bright detection at 24μm, and very faint optical counterparts. The detection rate with Mambo is very high at 45%, and both the detection rate and the average 1.2mm/24μm flux ratio are much higher than found for previous Spitzer MIR-selected samples, due to the fact that earlier samples favored systems with AGN-dominated MIR emission. Our sample, on the other hand, shows systematically lower 1.2mm/24μm ratios than a sample of Spitzer-detected submillimeter-selected galaxies (SMGs) in a similar redshift range. Thus Spitzer MIR selection complements submillimeter selection of high redshift starburst-dominated HLIRGs, finding a population with substantially different SED shapes. The large MIR/submillimeter flux ratios probably indicate exceptionally luminous 7.7μm PAH emission, based on Spitzer IRS spectra for a subset of these objects (Weedman et al. 2007).

  18. The diffuse gamma-ray flux associated with sub-PEV/PEV neutrinos from starburst galaxies

    SciTech Connect

    Chang, Xiao-Chuan; Wang, Xiang-Yu

    2014-10-01

    One attractive scenario for the excess of sub-PeV/PeV neutrinos recently reported by IceCube is that they are produced by cosmic rays in starburst galaxies colliding with the dense interstellar medium. These proton-proton (pp) collisions also produce high-energy gamma rays, which finally contribute to the diffuse high-energy gamma-ray background. We calculate the diffuse gamma-ray flux with a semi-analytic approach and consider that the very high energy gamma rays will be absorbed in the galaxies and converted into electron-positron pairs, which then lose almost all of their energy through synchrotron radiation in the strong magnetic fields in the starburst region. Since the synchrotron emission goes into energies below GeV, this synchrotron loss reduces the diffuse high-energy gamma-ray flux by a factor of about two, thus leaving more room for other sources to contribute to the gamma-ray background. For an E{sub ν}{sup −2} neutrino spectrum, we find that the diffuse gamma-ray flux contributes about 20% of the observed diffuse gamma-ray background in the 100 GeV range. However, for a steeper neutrino spectrum, this synchrotron loss effect is less important, since the energy fraction in absorbed gamma rays becomes lower.

  19. The Nuclear Near-Infrared Spectral Properties of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Mason, R. E.; Rodríguez-Ardila, A.; Martins, L.; Riffel, R.; González Martín, O.; Ramos Almeida, C.; Ruschel Dutra, D.; Ho, L. C.; Thanjavur, K.; Flohic, H.; Alonso-Herrero, A.; Lira, P.; McDermid, R.; Riffel, R. A.; Schiavon, R. P.; Winge, C.; Hoenig, M. D.; Perlman, E.

    2015-03-01

    We present spectra of the nuclear regions of 50 nearby (D = 1-92 Mpc, median = 20 Mpc) galaxies of morphological types E to Sm. The spectra, obtained with the Gemini Near-IR Spectrograph on the Gemini North telescope, cover a wavelength range of approximately 0.85-2.5 μm at R ˜ 1300-1800. There is evidence that most of the galaxies host an active galactic nucleus (AGN), but the range of AGN luminosities (log (L 2-10 keV [erg s-1]) = 37.0-43.2) in the sample means that the spectra display a wide variety of features. Some nuclei, especially the Seyferts, exhibit a rich emission-line spectrum. Other objects, in particular the type 2 Low Ionization Nuclear Emission Region galaxies, show just a few, weak emission lines, allowing a detailed view of the underlying stellar population. These spectra display numerous absorption features sensitive to the stellar initial mass function, as well as molecular bands arising in cool stars, and many other atomic absorption lines. We compare the spectra of subsets of galaxies known to be characterized by intermediate-age and old stellar populations, and find clear differences in their absorption lines and continuum shapes. We also examine the effect of atmospheric water vapor on the signal-to-noise ratio achieved in regions between the conventional NIR atmospheric windows, which are of potential interest to those planning observations of redshifted emission lines or other features affected by telluric H2O. Further exploitation of this data set is in progress, and the reduced spectra and data reduction tools are made available to the community.

  20. The nuclear near-infrared spectral properties of nearby galaxies

    NASA Astrophysics Data System (ADS)

    Mason, Rachel; Ardila, Alberto; Martins, Lucimara; Riffel, Rogerio; Gonzalez-Martin, Omaira; Ramos Almeida, Christina; Ruschel Dutra, Daniel; Ho, Luis C.; Thanjavur, Karun; Flohic, Helene; Alonso-Herrero, Almudena; Lira, Paulina; McDermid, Richard; Riffel, Rogemar A.; Schiavon, Ricardo P.; Winge, Claudia; Perlman, Eric S.; Hoenig, Michael D.

    2015-01-01

    We present spectra of the nuclear regions of 50 nearby (D = 1 - 92 Mpc, median = 20 Mpc) galaxies of morphological types E to Sm. The spectra, obtained with the Gemini Near-IR Spectrograph on the Gemini North telescope, cover a wavelength range of approximately 0.85-2.5 μm at R˜1300-1800. There is evidence that most of the galaxies host an active galactic nucleus (AGN), but the range of AGN luminosities (log (L2-10 keV [erg s-1]) = 37.0-43.2) in the sample means that the spectra display a wide variety of features. Some nuclei, especially the Seyferts, exhibit a rich emission-line spectrum. Other objects, in particular the type 2 Low Ionisation Nuclear Emission Region galaxies, show just a few, weak emission lines, allowing a detailed view of the underlying stellar population. These spectra display numerous absorption features sensitive to the stellar initial mass function, as well as molecular bands arising in cool stars, and many other atomic absorption lines. We compare the spectra of subsets of galaxies known to be characterised by intermediate-age and old stellar populations, and find clear differences in their absorption lines and continuum shapes. We also examine the effect of atmospheric water vapor on the signal-to-noise ratio achieved in regions between the conventional NIR atmospheric windows, of potential interest to those planning observations of redshifted emission lines or other features affected by telluric H2O. Further exploitation of this data set is in progress, and the reduced spectra and data reduction tools are made available to the community.

  1. LOCALIZED STARBURSTS IN DWARF GALAXIES PRODUCED BY THE IMPACT OF LOW-METALLICITY COSMIC GAS CLOUDS

    SciTech Connect

    Sánchez Almeida, J.; Muñoz-Tuñón, C.; Filho, M. E.; Elmegreen, B. G.; Elmegreen, D. M.; Pérez-Montero, E.; Vílchez, J. M.; Amorín, R.; Ascasibar, Y.; Papaderos, P.

    2015-09-10

    Models of galaxy formation predict that gas accretion from the cosmic web is a primary driver of star formation over cosmic history. Except in very dense environments where galaxy mergers are also important, model galaxies feed from cold streams of gas from the web that penetrate their dark matter halos. Although these predictions are unambiguous, the observational support has been indirect so far. Here, we report spectroscopic evidence for this process in extremely metal-poor galaxies (XMPs) of the local universe, taking the form of localized starbursts associated with gas having low metallicity. Detailed abundance analyses based on Gran Telescopio Canarias optical spectra of 10 XMPs show that the galaxy hosts have metallicities around 60% solar, on average, while the large star-forming regions that dominate their integrated light have low metallicities of some 6% solar. Because gas mixes azimuthally in a rotation timescale (a few hundred Myr), the observed metallicity inhomogeneities are only possible if the metal-poor gas fell onto the disk recently. We analyze several possibilities for the origin of the metal-poor gas, favoring the metal-poor gas infall predicted by numerical models. If this interpretation is correct, XMPs trace the cosmic web gas in their surroundings, making them probes to examine its properties.

  2. Localized Starbursts in Dwarf Galaxies Produced by the Impact of Low-metallicity Cosmic Gas Clouds

    NASA Astrophysics Data System (ADS)

    Sánchez Almeida, J.; Elmegreen, B. G.; Muñoz-Tuñón, C.; Elmegreen, D. M.; Pérez-Montero, E.; Amorín, R.; Filho, M. E.; Ascasibar, Y.; Papaderos, P.; Vílchez, J. M.

    2015-09-01

    Models of galaxy formation predict that gas accretion from the cosmic web is a primary driver of star formation over cosmic history. Except in very dense environments where galaxy mergers are also important, model galaxies feed from cold streams of gas from the web that penetrate their dark matter halos. Although these predictions are unambiguous, the observational support has been indirect so far. Here, we report spectroscopic evidence for this process in extremely metal-poor galaxies (XMPs) of the local universe, taking the form of localized starbursts associated with gas having low metallicity. Detailed abundance analyses based on Gran Telescopio Canarias optical spectra of 10 XMPs show that the galaxy hosts have metallicities around 60% solar, on average, while the large star-forming regions that dominate their integrated light have low metallicities of some 6% solar. Because gas mixes azimuthally in a rotation timescale (a few hundred Myr), the observed metallicity inhomogeneities are only possible if the metal-poor gas fell onto the disk recently. We analyze several possibilities for the origin of the metal-poor gas, favoring the metal-poor gas infall predicted by numerical models. If this interpretation is correct, XMPs trace the cosmic web gas in their surroundings, making them probes to examine its properties.

  3. 3D spectroscopy of merger Seyfert galaxy Mrk 334: nuclear starburst, superwind and the circumnuclear cavern

    NASA Astrophysics Data System (ADS)

    Smirnova, Aleksandrina; Moiseev, Alexei

    2010-01-01

    We are presenting new results on kinematics and structure of the Mrk 334 Seyfert galaxy. Panoramic (3D) spectroscopy is performed at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences using the integral-field Multi-Pupil Fiber Spectrograph (MPFS) and scanning Fabry-Pérot interferometer. The deep images have revealed that Mrk 334 is observed during the final stage of its merging with a massive companion. A possible mass ratio ranges from 1/5 to 1/3. The merger has triggered mass redistribution in the disc resulting in an intensification of nuclear activity and in a burst of star formation in the inner region of the galaxy. The circumnuclear starburst is so intense that its contribution to the gas ionization exceeds that contribution of the active galactic nuclei (AGN). We interpret the nuclear gas outflow with velocities of ~200kms-1 as a galactic superwind that accompanies the violent star formation. This suggestion is consistent with the asymmetric X-ray brightness distribution in Mrk 334. The trajectory of the fragments of the disrupted satellite in the vicinity of the main galaxy nucleus can be traced. In the galaxy disc, a cavern is found that is filled with a low-density ionized gas. We consider this region to be the place where the remnants of the companion have recently penetrated through the gaseous disc of the main galaxy.

  4. From H I to Stars: H I Depletion in Starbursts and Star-forming Galaxies in the ALFALFA Hα Survey

    NASA Astrophysics Data System (ADS)

    Jaskot, A. E.; Oey, M. S.; Salzer, J. J.; Van Sistine, A.; Bell, E. F.; Haynes, M. P.

    2015-07-01

    H i in galaxies traces the fuel for future star formation and reveals the effects of feedback on neutral gas. Using a statistically uniform, H i-selected sample of 565 galaxies from the Arecibo Legacy Fast ALFA (ALFALFA) Hα survey, we explore H i properties as a function of star formation activity. ALFALFA Hα provides R-band and Hα imaging for a volume-limited subset of the 21 cm ALFALFA survey. We identify eight starbursts based on Hα equivalent width and six with enhanced star formation relative to the main sequence. Both starbursts and non-starbursts have similar H i-to-stellar mass ratios ({M}{{H} {{I}}}/{M}*), which suggests that feedback is not depleting the starbursts’ H i. Consequently, the starbursts do have shorter H i depletion times ({t}{dep}), implying more efficient H i-to-H2 conversion. While major mergers likely drive this enhanced efficiency in some starbursts, the lowest-mass starbursts may experience periodic bursts, consistent with enhanced scatter in {t}{dep} at low {M}*. Two starbursts appear to be pre-coalescence mergers; their elevated {M}{{H} {{I}}}/{M}* suggest that H i-to-H2 conversion is still ongoing at this stage. By comparing with the GASS sample, we find that {t}{dep} anticorrelates with stellar surface density for disks, while spheroids show no such trend. Among early-type galaxies, {t}{dep} does not correlate with bulge-to-disk ratio; instead, the gas distribution may determine the star formation efficiency. Finally, the weak connection between galaxies’ specific star formation rates and {M}{{H} {{I}}}/{M}* contrasts with the well-known correlation between {M}{{H} {{I}}}/{M}* and color. We show that dust extinction can explain the H i–color trend, which may arise from the relationship between {M}*, {M}{{H} {{I}}}, and metallicity.

  5. From H I to Stars: H I Depletion in Starbursts and Star-forming Galaxies in the ALFALFA Hα Survey

    NASA Astrophysics Data System (ADS)

    Jaskot, A. E.; Oey, M. S.; Salzer, J. J.; Van Sistine, A.; Bell, E. F.; Haynes, M. P.

    2015-07-01

    H i in galaxies traces the fuel for future star formation and reveals the effects of feedback on neutral gas. Using a statistically uniform, H i-selected sample of 565 galaxies from the Arecibo Legacy Fast ALFA (ALFALFA) Hα survey, we explore H i properties as a function of star formation activity. ALFALFA Hα provides R-band and Hα imaging for a volume-limited subset of the 21 cm ALFALFA survey. We identify eight starbursts based on Hα equivalent width and six with enhanced star formation relative to the main sequence. Both starbursts and non-starbursts have similar H i-to-stellar mass ratios ({M}{{H} {{I}}}/{M}*), which suggests that feedback is not depleting the starbursts’ H i. Consequently, the starbursts do have shorter H i depletion times ({t}{dep}), implying more efficient H i-to-H2 conversion. While major mergers likely drive this enhanced efficiency in some starbursts, the lowest-mass starbursts may experience periodic bursts, consistent with enhanced scatter in {t}{dep} at low {M}*. Two starbursts appear to be pre-coalescence mergers; their elevated {M}{{H} {{I}}}/{M}* suggest that H i-to-H2 conversion is still ongoing at this stage. By comparing with the GASS sample, we find that {t}{dep} anticorrelates with stellar surface density for disks, while spheroids show no such trend. Among early-type galaxies, {t}{dep} does not correlate with bulge-to-disk ratio; instead, the gas distribution may determine the star formation efficiency. Finally, the weak connection between galaxies’ specific star formation rates and {M}{{H} {{I}}}/{M}* contrasts with the well-known correlation between {M}{{H} {{I}}}/{M}* and color. We show that dust extinction can explain the H i-color trend, which may arise from the relationship between {M}*, {M}{{H} {{I}}}, and metallicity.

  6. HST/ACS PHOTOMETRY OF OLD STARS IN NGC 1569: THE STAR FORMATION HISTORY OF A NEARBY STARBURST

    SciTech Connect

    Grocholski, Aaron J.; Van der Marel, Roeland P.; Aloisi, Alessandra E-mail: marel@stsci.edu; and others

    2012-05-15

    We used Hubble Space Telescope/Advanced Camera for Surveys to obtain deep V- and I-band images of NGC 1569, one of the closest and strongest starburst galaxies in the universe. These data allowed us to study the underlying old stellar population, aimed at understanding NGC 1569's evolution over a full Hubble time. We focus on the less-crowded outer region of the galaxy, for which the color-magnitude diagram (CMD) shows predominantly a red giant branch (RGB) that reaches down to the red clump/horizontal branch feature (RC/HB). A simple stellar population analysis gives clear evidence for a more complicated star formation history (SFH) in the outer region. We derive the full SFH using a newly developed code, SFHMATRIX, which fits the CMD Hess diagram by solving a non-negative least-squares problem. Our analysis shows that the relative brightnesses of the RGB tip and RC/HB, along with the curvature and color of the RGB, provide enough information to ameliorate the age-metallicity-extinction degeneracy. The distance/reddening combination that best fits the data is E(B - V) = 0.58 {+-} 0.03 and D = 3.06 {+-} 0.18 Mpc. Star formation began {approx}13 Gyr ago, and this accounts for the majority of the mass in the outer region. However, the initial burst was followed by a relatively low, but constant, rate of star formation until {approx}0.5-0.7 Gyr ago when there may have been a short, low intensity burst of star formation. Stellar metallicity increases over time, consistent with chemical evolution expectations. The dominant old population shows a considerable spread in metallicity, similar to the Milky Way halo. However, the star formation in NGC 1569's outer region lasted much longer than in the Milky Way. The distance and line-of-sight velocity of NGC 1569 indicate that it has moved through the IC 342 group of galaxies, which may have caused this extended star formation. Comparison with other recent work provides no evidence for radial population gradients in the old

  7. Catching a glimpse of the X-ray emission from galaxies in the early Universe by studying nearby low-metallicity galaxies

    NASA Astrophysics Data System (ADS)

    Basu-Zych, Antara; Hornschemeier, Ann; Lehmer, Bret; Ptak, Andrew; Yukita, Mihoko

    2015-09-01

    Deep studies of X-ray emission from galaxies, such as the Chandra Deep Field-South 4 Ms (soon to be 7Ms) survey, have allowed us to peer back in history at X-ray binary formation and evolution over cosmic timescales. X-ray stacking observations of z=1-4 star-forming galaxies reveal that the metallicity evolution of the Universe drives the evolution of the 2-10 keV X-ray luminosity per star formation rate (SFR), which is dominated by high mass X-ray binaries (HMXBs). By finding local (z=0.02-0.2), rare, analogs of these high redshift galaxies, we have found further evidence that the X-ray emission per SFR is elevated compared to typical local star-forming galaxies and this appears to be due to the lower metallicities of these galaxies. Theoretically, metal poor stars produce weaker stellar winds, which results in higher numbers of more massive binaries and therefore leads to higher X-ray luminosities in metal poor populations. Since galaxies in the early universe (and their binaries) formed in a more pristine universe, with few metals, the analogs that we have been studying have cosmological significance. X-ray emission from X-ray binaries and hot gas within galaxies at these early epochs is expected to be important for heating and reionization of the Universe. We will present our current results on the study of HMXB populations in nearby metal-poor starbursts. These primordial analog galaxies represent a challenge for current X-ray facilities, but with modest exposures with Athena, we will obtain high-resolution X-ray spectra permitting detailed study of their properties. We use simulations of the X-ray spectra from these galaxies with Athena to explore the potential capability for measuring column densities (n_H) and metallicities, as well as line shifts to detect outflows that may ultimately enrich the intergalactic medium (IGM).

  8. The Dragonfly nearby Galaxies Survey. I. Substantial Variation in the Diffuse Stellar Halos around Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Merritt, Allison; van Dokkum, Pieter; Abraham, Roberto; Zhang, Jielai

    2016-10-01

    Galaxies are thought to grow through accretion; as less massive galaxies are disrupted and merge over time, their debris results in diffuse, clumpy stellar halos enveloping the central galaxy. Here we present a study of the variation in the stellar halos of galaxies, using data from the Dragonfly Nearby Galaxies Survey (DNGS). The survey consists of wide field, deep ({μ }g\\gt 31 mag arcsec‑2) optical imaging of nearby galaxies using the Dragonfly Telephoto Array. Our sample includes eight spiral galaxies with stellar masses similar to that of the Milky Way, inclinations of 16-19 degrees and distances between 7-18 Mpc. We construct stellar mass surface density profiles from the observed g-band surface brightness in combination with the g ‑ r color as a function of radius, and compute the halo fractions from the excess stellar mass (relative to a disk+bulge fit) beyond 5 half-mass radii. We find a mean halo fraction of 0.009 ± 0.005 and a large rms scatter of {1.01}-0.26+0.9 dex. The peak-to-peak scatter of the halo fraction is a factor of \\gt 100—while some galaxies feature strongly structured halos resembling that of M31, three of the eight have halos that are completely undetected in our data. We conclude that spiral galaxies as a class exhibit a rich variety in stellar halo properties, implying that their assembly histories have been highly non-uniform. We find no convincing evidence for an environmental or stellar mass dependence of the halo fraction in the sample.

  9. The Far-Infrared Energy Distributions of Seyfert and Starburst Galaxies in the Local Universe: Infrared Space Observatory Photometry of the 12 Micron Active Galaxy Sample

    NASA Astrophysics Data System (ADS)

    Spinoglio, Luigi; Andreani, Paola; Malkan, Matthew A.

    2002-06-01

    New far-infrared photometry with ISOPHOT aboard the Infrared Space Observatory (ISO) is presented for 58 galaxies with homogeneous published data for another 32 galaxies, all belonging to the 12 μm galaxy sample-in total, 29 Seyfert 1 galaxies, 35 Seyfert 2 galaxies, and 12 starburst galaxies, or about half of the 12 μm active galaxy sample, plus 14 normal galaxies for comparison. ISO and Infrared Astronomical Satellite (IRAS) data are used to define color-color diagrams and spectral energy distributions (SEDs). Thermal dust emission at two temperatures (one cold at 15-30 K and one warm at 50-70 K) can fit the 60-200 μm SED, with a dust emissivity law proportional to the inverse square of the wavelength. Seyfert 1 galaxies and Seyfert 2 galaxies are indistinguishable longward of 100 μm, while, as already seen by IRAS, the former have flatter SEDs shortward of 60 μm. A mild anticorrelation is found between the [200-100] color and the ``60 μm excess.'' We infer that this is due to the fact that galaxies with a strong starburst component and thus a strong 60 μm flux have a steeper far-infrared turnover. In non-Seyfert galaxies, increasing the luminosity corresponds to increasing the star formation rate, which enhances the 25 and 60 μm emission. This shifts the peak emission from around 150 μm in the most quiescent spirals to shorter than 60 μm in the strongest starburst galaxies. To quantify these trends further, we identified with the IRAS colors three idealized infrared SEDs: pure quiescent disk emission, pure starburst emission, and pure Seyfert nucleus emission. Even between 100 and 200 μm, the quiescent disk emission remains much cooler than the starburst component. Seyfert galaxies have 100-200 μm SEDs ranging from pure disks to pure starbursts, with no apparent contribution from their active nuclei at those wavelengths. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France

  10. 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

    SciTech Connect

    Riechers, Dominik A.; Carilli, Christopher L.; Capak, Peter L.; Yan, Lin; Scoville, Nicholas Z.; Smolčić, Vernesa; Schinnerer, Eva; Yun, Min; Cox, Pierre; Bertoldi, Frank; Karim, Alexander

    2014-12-01

    We report interferometric imaging of [C II]({sup 2} P {sub 3/2}→{sup 2} P {sub 1/2}) and OH({sup 2}Π{sub 1/2} 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]({sup 2} P {sub 3/2}→{sup 2} P {sub 1/2}) emission is distributed over a scale of 3.9 kpc, implying a dynamical mass of 9.7 × 10{sup 10} M {sub ☉}, and a star formation rate (SFR) surface density of Σ{sub SFR} = 530 M {sub ☉} yr{sup –1} kpc{sup –2}. This suggests that AzTEC-3 forms stars at Σ{sub SFR} 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]({sup 2} P {sub 3/2}→{sup 2} P {sub 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 {sub ☉} yr{sup –1}, consistent with a UV-based estimate of 22 M {sub ☉} yr{sup –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.

  11. Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at Z greater than 1

    NASA Technical Reports Server (NTRS)

    VanDerWel, A.; Straughn, A. N.; Rix, H.-W.; Finkelstein, S. L.; Koekemoer, A. M.; Weiner, B. J.; Wuyts, S.; Bell, E. F.; Faber, S. M.; Trump, J. R.; Koo, D.; Ferguson, H. C.; Scarlata, C.; Hathi, N. P.; Dunlop, J. S.; Newman, J. A.; Kocevski, D. D.; Lai, K.; Grogin, N. A.; Rodney, S. A.; Lee, K.-S.; Guo, Y.

    2011-01-01

    We identify an abundant population of extreme emission line galaxies at redshift z=1.6 - 1.8 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). 69 candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared, broad-band fluxes. Supported by spectroscopic confirmation of strong [OIII] emission lines - with equivalent widths approximately 1000A - in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are dwarf galaxies with approximately 10(exp 8) solar mass in stellar mass, undergoing an enormous star-burst phase with M*/M* of only approximately 10 Myr. The star formation activity and the co-moving number density (3.7 x 10(exp -4) Mpc(exp -3)) imply that strong, short-lived bursts play a significant, perhaps even dominant role in the formation and evolution of dwarf galaxies at z greater than 1. The observed star formation activity can produce in less than 5 Gyr the same amount of stellar mass density as is presently contained in dwarf galaxies. Therefore, our observations provide a strong indication that the stellar populations of present-day dwarf galaxies formed mainly in strong, short-lived bursts, mostly at z greater than 1.

  12. Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at Z greater than 1

    NASA Technical Reports Server (NTRS)

    vanderWel, A.; Straughn, A. N.; Rix, H.-W.; Finkelstein, S. L.; Koekemoer, A. M.; Weiner, B. J.; Wuyts, S.; Bell, E. F.; Faber, S. M.; Trump, J. R.; Koo, D. C.; Ferguson, H. C.; Scarlata, C.; Hathi, N. P.; Dunlop, J. S.; Newman, J. A.; Dickinson, M.; Jahnke, K.; Salmon, B. W.; deMello, D. F.; Kkocevski, D. D.; Lai, K.; Grogin, N. A.; Rodney, S. A.; Guo, Yicheng

    2012-01-01

    We identify an abundant population of extreme emission line galaxies (EELGs) at redshift z approx. 1.7 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). 69 EELG candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared broad-band magnitudes. Supported by spectroscopic confirmation of strong [OIII] emission lines . with rest-frame equivalent widths approx. 1000A in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are galaxies with approx.10(exp 8) Solar Mass in stellar mass, undergoing an enormous starburst phase with M*/M* of only approx. 15 Myr. These bursts may cause outflows that are strong enough to produce cored dark matter profiles in low-mass galaxies. The individual star formation rates and the co-moving number density (3.7x10(exp -4) Mpc(sup -3) can produce in approx.4 Gyr much of the stellar mass density that is presently contained in 10(exp 8) - 10(exp 9) Solar Mass dwarf galaxies. Therefore, our observations provide a strong indication that many or even most of the stars in present-day dwarf galaxies formed in strong, short-lived bursts, mostly at z > 1.

  13. Discovery of a Galaxy Cluster with a Violently Starbursting Core at z = 2.506

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Elbaz, David; Daddi, Emanuele; Finoguenov, Alexis; Liu, Daizhong; Schreiber, Corentin; Martín, Sergio; Strazzullo, Veronica; Valentino, Francesco; van der Burg, Remco; Zanella, Anita; Ciesla, Laure; Gobat, Raphael; Le Brun, Amandine; Pannella, Maurilio; Sargent, Mark; Shu, Xinwen; Tan, Qinghua; Cappelluti, Nico; Li, Yanxia

    2016-09-01

    We report the discovery of a remarkable concentration of massive galaxies with extended X-ray emission at z spec = 2.506, which contains 11 massive (M * ≳ 1011 M ⊙) galaxies in the central 80 kpc region (11.6σ overdensity). We have spectroscopically confirmed 17 member galaxies with 11 from CO and the remaining ones from Hα. The X-ray luminosity, stellar mass content, and velocity dispersion all point to a collapsed, cluster-sized dark matter halo with mass M 200c = 1013.9±0.2 M ⊙, making it the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive galaxies classified as quiescent. The star formation rate (SFR) in the 80 kpc core reaches ˜3400 M ⊙ yr-1 with a gas depletion time of ˜200 Myr, suggesting that we caught this cluster in rapid build-up of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst fraction (˜25%, compared to 3%-5% in the field). The presence of both a collapsed, cluster-sized halo and a predominant population of massive SFGs suggests that this structure could represent an important transition phase between protoclusters and mature clusters. It provides evidence that the main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster, providing new insights into massive cluster formation at early epochs. The large integrated stellar mass at such high redshift challenges our understanding of massive cluster formation.

  14. Stellar Populations of Highly Magnified Lensed Galaxies Young Starburst at Z to Approximately 2

    NASA Technical Reports Server (NTRS)

    Wuyts, Eva; Rigby, Jane R.; Gladders, Michael D.; Gilbank, David G.; Sharon, Keren; Gralla, Megan B.; Bayliss, Matthew B.

    2011-01-01

    We present a comprehensive analysis of the rest-frame UV to near-IR spectral energy distributions and rest-frame optical spectra of four of the brightest gravitationally lensed galaxies in the literature: RCSGA 032727-132609 at z = 170, MS1512-cB58 at z = 2.73, SGAS J152745.1+065219 at z = 2.76 and SGAS J12265L3+215220 at z = 2.92. This includes new Spitzer imaging for RCSGA0327 as well as new spectra, near-IR imaging and Spitzer imaging for SGAS1527 and SGAS1226. Lensing magnifications of 3-4 magnitudes allow a detailed study of the stellar populations and physical conditions. We compare star formation rates as measured from the SED fit, the Ha and [O II] .(lambda)3727 emission lines, and the UV+IR bolometric luminosity where 24micron photometry is available. The SFR estimate from the SED fit is consistently higher than the other indicators, which suggests that the Calzetti dust extinction law used in the SED fitting is too flat for young star-forming galaxies at z approx. 2. Our analysis finds similar stellar population parameters for all four lensed galaxies: stellar masses 3 - 7 x 10(exp 9) Stellar mass, young ages approx. 100 Myr, little dust content E(B - V)=0.10-0.25, and star formation rates around 20- 100 Stellar mass/y. Compared to typical values for the galaxy population at z approx. 2, this suggests we are looking at newly formed, starbursting systems that have only recently started the build-up of stellar mass. These results constitute the first detailed, uniform analysis of a sample of the growing number of strongly lensed galaxies known at z approx. 2. Subject headings: galaxies: high-redshift, strong gravitational lensing, infrared: galaxies

  15. Motions in Nearby Galaxy Cluster Reveal Presence of Hidden Superstructure

    NASA Astrophysics Data System (ADS)

    2004-09-01

    A nearby galaxy cluster is facing an intergalactic headwind as it is pulled by an underlying superstructure of dark matter, according to new evidence from NASA's Chandra X-ray Observatory. Astronomers think that most of the matter in the universe is concentrated in long large filaments of dark matter and that galaxy clusters are formed where these filaments intersect. A Chandra survey of the Fornax galaxy cluster revealed a vast, swept-back cloud of hot gas near the center of the cluster. This geometry indicates that the hot gas cloud, which is several hundred thousand light years in length, is moving rapidly through a larger, less dense cloud of gas. The motion of the core gas cloud, together with optical observations of a group of galaxies racing inward on a collision course with it, suggests that an unseen, large structure is collapsing and drawing everything toward a common center of gravity. X-ray Image of Fornax with labels X-ray Image of Fornax with labels "At a relatively nearby distance of about 60 million light years, the Fornax cluster represents a crucial laboratory for studying the interplay of galaxies, hot gas and dark matter as the cluster evolves." said Caleb Scharf of Columbia University in New York, NY, lead author of a paper describing the Chandra survey that was presented at an American Astronomical Society meeting in New Orleans, LA. "What we are seeing could be associated directly with the intergalactic gas surrounding a very large scale structure that stretches over millions of light years." The infalling galaxy group, whose motion was detected by Michael Drinkwater of the University of Melbourne in Australia, and colleagues, is about 3 million light years from the cluster core, so a collision with the core will not occur for a few billion years. Insight as to how this collision will look is provided by the elliptical galaxy NGC 1404 that is plunging into the core of the cluster for the first time. As discussed by Scharf and another group

  16. A Robust Test of the Unified Model for Seyfert Galaxies with Implications for the Starburst Phenomenon

    NASA Technical Reports Server (NTRS)

    Weaver, Kimberly A.

    1997-01-01

    My research involves detailed analysis of X-ray emission from Active Galactic Nuclei (AGN). For over a decade, the paradigm for AGN has rested soundly on the unified model hypothesis, which posits that the only difference between broad-line objects (e.g., Type 1 Seyfert galaxies) and narrow-line objects (e.g., Type 2 Seyferts) is that in the former case our line of sight evades toroidal obscuration surrounding the nucleus, while in the latter, our line of sight is blocked by the optically thick torus. It is well established that some Seyfert 2s contain Seyfert I nuclei (i.e., a hidden broad line region), but whether or not all Seyfert 2s contain obscured Seyfert 1 nuclei or whether some Seyfert 2s are intrinsically Seyfert 2s is not known. Optical, IR, and UV surveys are not appropriate to examine this hypothesis because such emissions are either anisotropic or subject to the effects of obscuration, and thus depend strongly on viewing angle. Hard X-rays, on the other hand, can penetrate gas with column densities as high as 10( exp 24.5) cm(-2) and thus provide reliable, direct probes of the cores of heavily obscured AGN. Combining NASA archival data from the Advanced Satellite of Cosmology and Astrophysics (ASCA), the Rossi X-ray Timing Explorer (RXTE), and Rosat, I am accumulating X-ray data between 0.1 and 60 keV to produce a catalog of the broad-band X-ray spectral properties of Seyfert galaxies. These data will be used to perform concrete tests of the unified model, and (compared with similar data on Starbursts) to examine a possible evolutionary connection between Seyfert and Starburst galaxies.

  17. EVIDENCE FOR AN INTERACTION IN THE NEAREST STARBURSTING DWARF IRREGULAR GALAXY IC 10

    SciTech Connect

    Nidever, David L.; Slater, Colin T.; Bell, Eric F.; Ashley, Trisha; Simpson, Caroline E.; Ott, Jürgen; Johnson, Megan; Stanimirović, Snežana; Putman, Mary; Majewski, Steven R.; Jütte, Eva; Oosterloo, Tom A.; Burton, W. Butler

    2013-12-20

    Using deep 21 cm H I data from the Green Bank Telescope we have detected an ≳18.3 kpc long gaseous extension associated with the starbursting dwarf galaxy IC 10. The newly found feature stretches 1.°3 to the northwest and has a large radial velocity gradient reaching to ∼65 km s{sup –1} lower than the IC 10 systemic velocity. A region of higher column density at the end of the extension that possesses a coherent velocity gradient (∼10 km s{sup –1} across ∼26') transverse to the extension suggests rotation and may be a satellite galaxy of IC 10. The H I mass of IC 10 is 9.5 × 10{sup 7} (d/805 kpc){sup 2} M {sub ☉} and the mass of the new extension is 7.1 × 10{sup 5} (d/805 kpc){sup 2} M {sub ☉}. An IC 10-M31 orbit using known radial velocity and proper motion values for IC 10 show that the H I extension is inconsistent with the trailing portion of the orbit so that an M31-tidal or ram pressure origin seems unlikely. We argue that the most plausible explanation for the new feature is that it is the result of a recent interaction (and possible late merger) with another dwarf galaxy. This interaction could not only have triggered the origin of the recent starburst in IC 10, but could also explain the existence of previously found counter-rotating H I gas in the periphery of the IC 10 which was interpreted as originating from primordial gas infall.

  18. An XMM-Newton and Chandra study of the starburst galaxy IC 10

    NASA Astrophysics Data System (ADS)

    Wang, Q. Daniel; Whitaker, Katherine E.; Williams, Rosa

    2005-09-01

    We present an X-ray study of our nearest starburst galaxy IC 10, based on XMM-Newton and Chandra observations. A list of 73 XMM-Newton and 28 Chandra detections of point-like X-ray sources in the field is provided; a substantial fraction of them are likely stellar objects in the Milky Way due to the low Galactic latitude location of IC 10. The brightest source in the IC 10 field, X-1, has a mean 0.3-8.0 keV luminosity of ~1.2 × 1038ergs-1 and shows a large variation by a factor of up to ~6 on time-scales of ~104 s during the XMM-Newton observation. The X-ray spectra of the source indicate the presence of a multicolour blackbody accretion disc with an inner disc temperature Tin~ 1.1 keV. These results are consistent with the interpretation of the source as a stellar mass black hole (BH), probably accreting from a Wolf-Rayet (W-R) star companion. We infer the mass of this BH to be ~4Msolar if it is not spinning, or a factor of up to ~6 higher if there is significant spinning. We also detect an apparent diffuse soft X-ray emission component of IC 10. An effective method is devised to remove the X-ray CCD-readout streaks of X-1 that strongly affect the study of the diffuse component in the XMM-Newton and Chandra observations. We find that the diffuse X-ray morphology is oriented along the optical body of the galaxy and is chiefly associated with starburst regions. The diffuse component can be characterized by an optically thin thermal plasma with a mean temperature of ~4 × 106 K and a 0.5-2 keV luminosity of ~8 × 1037ergs-1, representing only a small fraction of the expected mechanical energy inputs from massive stars in the galaxy. There is evidence that the hot gas is driving outflows from the starburst regions; therefore, the bulk of the energy inputs may be released in a galactic wind.

  19. 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.

  20. Chandra Examines Black Holes Large and Small in Nearby Galaxy

    NASA Astrophysics Data System (ADS)

    2001-05-01

    Probing a large, nearby galaxy in the constellation of Circinus, NASA’s Chandra X-ray Observatory presents a new view of both the galaxy’s supermassive black hole and a host of potential smaller black holes sprinkled throughout its spiral arms. The results include the first detection of a black hole’s periodic variability in X-rays outside our galactic neighborhood. Astronomers from Penn State University used Chandra to discover a variable object within the dozen or so X-ray emitting sources sprinkled throughout the Circinus galaxy. The intensity of X-rays from this source changes on a cycle of 7.5 hours - the first time this "periodic variability" has been detected at X-ray wavelengths in an object outside the "Local Group" of galaxies. And, along with its brightness, this evidence strongly suggests that the system contains a black hole some 50 times the mass of the Sun. "Extremely luminous X-ray sources such as this one appear to be common among other galaxies," said Franz Bauer, a postdoctoral scholar at Penn State and lead author of a July 2001 paper in The Astronomical Journal. "But until Chandra, we have never had an instrument that could clearly identify whether they were simply massive X-ray binary systems, or if they represented a new class of objects" "The periodic variability in the Chandra data of Circinus provides us with a key signature that these objects are indeed X-ray binary systems," continued Bauer. "This is important because black holes with masses much larger than 10 times the mass of the Sun such as this one are difficult to explain under current theories of star formation and destruction. Definitively finding a periodic signal in one allows us to test some of our past assumptions." The X-ray data acquired by two independent teams -- one at Penn State and George Mason University and the other at the University of Maryland -- also provide evidence that strongly supports the "unified model," a theory in which a large doughnut-shaped ring

  1. PHYSICAL PROPERTIES OF THE CIRCUMNUCLEAR STARBURST RING IN THE BARRED GALAXY NGC 1097

    SciTech Connect

    Hsieh, Pei-Ying; Matsushita, Satoki; Ho, Paul T. P.; Wu, Ya-Lin; Liu, Guilin; Oi, Nagisa

    2011-08-01

    We report high-resolution {sup 12}CO(J = 2-1), {sup 13}CO(J = 2-1), and {sup 12}CO(J = 3-2) imaging of the Seyfert 1/starburst ring galaxy NGC 1097 with the Submillimeter Array for the purpose of studying the physical and kinematic properties of the 1 kpc circumnuclear starburst ring. Individual star clusters as detected in the Hubble Space Telescope map of Pa{alpha} line emission have been used to determine the star formation rate (SFR), and are compared with the properties of the molecular gas. The molecular ring has been resolved into individual clumps at the giant molecular cloud association (GMA) scale of 200-300 pc in all three CO lines. The intersection between the dust lanes and the starburst ring, which is associated with the orbit-crowding region, is resolved into two physically/kinematically distinct features in the 1.''5 x 1.''0 (105 x 70 pc) {sup 12}CO(J = 2-1) map. The clumps associated with the dust lanes have broader line widths, higher surface gas densities, and lower SFRs, while the narrow line clumps associated with the starburst ring have opposite characteristics. A Toomre-Q value lower than unity at the radius of the ring suggests that the molecular ring is gravitationally unstable to fragmentation at GMA scale. The line widths and surface density of the gas mass of the clumps show an azimuthal variation related to the large-scale dynamics. The SFR, on the other hand, is not significantly affected by the dynamics, but has a correlation with the intensity ratio of {sup 12}CO (J = 3-2) and {sup 12}CO(J = 2-1), which traces the denser gas associated with star formation. Our resolved CO map, especially in the orbit-crowding region, observationally demonstrates for the first time that the physical/kinematic properties of GMAs are affected by the large-scale bar-potential dynamics in NGC 1097.

  2. Evidence of Nuclear Disks from the Radial Distribution of CCSNe in Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Herrero-Illana, Rubén; Pérez-Torres, Miguel Ángel; Alberdi, Antxon

    Galaxy-galaxy interactions are expected to be responsible for triggering massive star formation and possibly accretion onto a supermassive black hole, by providing large amounts of dense molecular gas down to the central kiloparsec region. Several scenarios to drive the gas further down to the central ˜ 100 pc, have been proposed, including the formation of a nuclear disk around the black hole, where massive stars would produce supernovae. Here, we probe the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M82, Arp 299-A, and Arp 220, by using high-angular resolution (≲ 0.'1) radio observations. We derived scale-length values for the putative nuclear disks, which range from ˜ 20-30 pc for Arp 299-A and Arp 220, up to ˜ 140 pc for M82. The radial distribution of SNe for the nuclear disks in Arp 299-A and Arp 220 is also consistent with a power-law surface density profile of exponent γ = 1, as expected from detailed hydrodynamical simulations of nuclear disks. This study is detailed in Herrero-Illana, Perez-Torres, and Alberdi [11].

  3. The detection of supergalactic winds: The edge-on starburst galaxy NGC 4631

    NASA Astrophysics Data System (ADS)

    Melo, V.; Muñoz-Tuñón, C.; Recillas, E.; Tenorio-Tagle, G.; Rodríguez-Espinosa, J. M.

    We are studying a sample of spiral galaxies which host nuclear starbursts. Our aim is first to detect supergalactic winds (SGWs) and second to establish the conditions needed for the onset of the supergalactic wind phase. In this contribution we present preliminary work on the galaxy NGC 4631. We analyze Fabry--Perot observations (TAURUS) taken at the 4.2~m William Herschel Telescope Roque de los Muchachos Observatory (ORM). Data have been complemented with long slit spectroscopy (ISIS) taken from the La Palm a (ORM) data archive. Recently X-ray observations from Chandra have evidenced the escaping of hot gas from the disk into the halo. We identify possible SGW features on both sides of the disk. Emission lines are split revealing outflows and blow-out into the galactic halo. More detailed analysis has been undertaken in order to decide wether or not the galaxy has an SGW. Typical sizes of split lines areas range from 55~pc (a bubble feature) to 142.5~pc, the largest extent. Velocities of split lines range from 40 km/s to 85 km/s.

  4. Direct Detections of Young Stars in Nearby Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Ford, H. Alyson; Bregman, Joel N.

    2013-06-01

    Small amounts of star formation in elliptical galaxies are suggested by several results: surprisingly young ages from optical line indices, cooling X-ray gas, and mid-infrared dust emission. Such star formation has previously been difficult to directly detect, but using ultraviolet Hubble Space Telescope Wide Field Camera 3 imaging, we have identified individual young stars and star clusters in four nearby ellipticals. Ongoing star formation is detected in all galaxies, including three ellipticals that have previously exhibited potential signposts of star-forming conditions (NGC 4636, NGC 4697, and NGC 4374), as well as the typical "red and dead" NGC 3379. The current star formation in our closest targets, where we are most complete, is between 2.0 and 9.8 × 10-5 M ⊙ yr-1. The star formation history was roughly constant from 0.5 to 1.5 Gyr (at (3-5) × 10-4 M ⊙ yr-1), but decreased by a factor of several in the past 0.3 Gyr. Most star clusters have a mass between 102 and 104 M ⊙. The specific star formation rates of ~10-16 yr-1 (at the present day) or ~10-14 yr-1 (when averaging over the past Gyr) imply that a fraction 10-8 of the stellar mass is younger than 100 Myr and 10-5 is younger than 1 Gyr, quantifying the level of frosting of recent star formation over the otherwise passive stellar population. There is no obvious correlation between either the presence or spatial distribution of postulated star formation indicators and the star formation we detect. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 11583.

  5. DIRECT DETECTIONS OF YOUNG STARS IN NEARBY ELLIPTICAL GALAXIES

    SciTech Connect

    Ford, H. Alyson; Bregman, Joel N.

    2013-06-20

    Small amounts of star formation in elliptical galaxies are suggested by several results: surprisingly young ages from optical line indices, cooling X-ray gas, and mid-infrared dust emission. Such star formation has previously been difficult to directly detect, but using ultraviolet Hubble Space Telescope Wide Field Camera 3 imaging, we have identified individual young stars and star clusters in four nearby ellipticals. Ongoing star formation is detected in all galaxies, including three ellipticals that have previously exhibited potential signposts of star-forming conditions (NGC 4636, NGC 4697, and NGC 4374), as well as the typical ''red and dead'' NGC 3379. The current star formation in our closest targets, where we are most complete, is between 2.0 and 9.8 Multiplication-Sign 10{sup -5} M{sub Sun} yr{sup -1}. The star formation history was roughly constant from 0.5 to 1.5 Gyr (at (3-5) Multiplication-Sign 10{sup -4} M{sub Sun} yr{sup -1}), but decreased by a factor of several in the past 0.3 Gyr. Most star clusters have a mass between 10{sup 2} and 10{sup 4} M{sub Sun }. The specific star formation rates of {approx}10{sup -16} yr{sup -1} (at the present day) or {approx}10{sup -14} yr{sup -1} (when averaging over the past Gyr) imply that a fraction 10{sup -8} of the stellar mass is younger than 100 Myr and 10{sup -5} is younger than 1 Gyr, quantifying the level of frosting of recent star formation over the otherwise passive stellar population. There is no obvious correlation between either the presence or spatial distribution of postulated star formation indicators and the star formation we detect.

  6. A Chandra X-Ray Investigation of the Violent Interstellar Medium: From Dwarf Starbursts to Ultraluminous Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Grimes, J. P.; Heckman, T.; Strickland, D.; Ptak, A.

    2005-07-01

    We have analyzed observations with the Chandra X-Ray Observatory of the diffuse emission by hot gas in seven dwarf starburst galaxies, six edge-on starburst galaxies, and nine ultraluminous infrared galaxies. These systems cover ranges of ~104 in X-ray luminosity, and several thousand in star formation rate and K-band luminosity (a proxy for stellar mass). Despite this range in fundamental parameters, we find that the properties of the diffuse X-ray emission are very similar in all three classes of starburst galaxies. The spectrum of the diffuse emission is well fitted by thermal emission from gas with kT~0.25-0.8 keV and with several times solar abundance ratios of α-elements to Fe. The ratio of the thermal X-ray to far-infrared luminosity is roughly constant, as is the characteristic surface brightness of the diffuse X-ray emission. The size of the diffuse X-ray source increases systematically with both far-infrared and K-band luminosity. All three classes show strong morphological relationships between the regions of hot gas probed by the diffuse X-ray emission and the warm gas probed by optical line emission. These findings suggest that the same physical mechanism is producing the diffuse X-ray emission in the three types of starbursts. These results are consistent with that mechanism being shocks driven by a galactic ``superwind,'' which is powered by the kinetic energy collectively supplied by stellar winds and supernovae in the starburst.

  7. 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.

  8. Stellar Populations of Highly Magnified Lensed Galaxies: Young Starbursts at Z approximately 2

    NASA Technical Reports Server (NTRS)

    Wuyts, Eva; Rigby, Jane R.; Gladders, Michael D.; Gilbank, David G.; Sharon, Keren; Gralla, Megan B.; Bayliss, Matthew B.

    2012-01-01

    We present a comprehensive analysis of the rest-frame UV to near-IR spectral energy distributions (SEDs) and rest-frame optical spectra of four of the brightest gravitationally lensed galaxies in the literature: RCSGA 032727-132609 at z = 1.70, MS1512-cB58 at z = 2.73, SGAS J152745.1+065219 at z = 2.76, and SGAS J122651.3+215220 at z = 2.92. This includes new Spitzer imaging for RCSGA0327 as well as new spectra, near-IR imaging and Spitzer imaging for SGAS1527 and SGAS1226. Lensing magnifications of 3-4 mag allow a detailed study of the stellar populations and physical conditions. We compare star formation rates (SFRs) as measured from the SED fit, the Ha and [O II] ?3727 emission lines, and the UV+IR bolometric luminosity where 24 micron photometry is available. The SFR estimate from the SED fit is consistently higher than the other indicators, which suggests that the Calzetti dust extinction law used in the SED fitting is too flat for young star-forming galaxies at z 2. Our analysis finds similar stellar population parameters for all four lensed galaxies: stellar masses (3-7) ? 10(exp 9)Solar M young ages approx 100 Myr, little dust content E(B - V) = 0.10-0.25, and SFRs around 20-100 solar M/ yr. Compared to typical values for the galaxy population at z approx. 2, this suggests we are looking at newly formed, starbursting systems that have only recently started the buildup of stellar mass. These results constitute the first detailed, uniform analysis of a sample of the growing number of strongly lensed galaxies known at z approx 2.

  9. A Supermassive Black Hole in a Nearby Galaxy

    NASA Astrophysics Data System (ADS)

    2001-03-01

    ISAAC Inspects the Center of Centaurus A Summary The nearby galaxy Centaurus A harbours a supermassive black hole at its centre . Using the ISAAC instrument at the ESO Very Large Telescope (VLT) , an international team of astronomers [1] has peered right through the spectacular dust lane of the peculiar galaxy Centaurus A , located approximately 11 million light-years away. They were able to probe the thin disk of gas that surrounds the very center of this galaxy. The new measurements show that the compact nucleus in the middle weighs more than 200 million solar masses ! This is too much just to be due to normal stars. The astronomers thus conclude the existence of a supermassive black hole lurking at the centre of Centaurus A . PR Photo 08a/01 : Visual image of the centre of Centaurus A . PR Photo 08b/01 : ISAAC spectrum of the centre of Centaurus A . PR Photo 08c/01 : The corresponding rotation curve from which the mass of the black hole was deduced. A well studied galaxy with a hidden center ESO PR Photo 08a/01 ESO PR Photo 08a/01 [Preview - JPEG: 352 x 400 pix - 160k] [Normal - JPEG: 704 x 800 pix - 376k] Caption : PR Photo 08a/01 shows a small area in the direction of the heavily obscured centre of the peculiar radio galaxy Centaurus A , as seen in visual light. It measures about 80 x 80 arcsec 2 , or 4400 x 4400 light-year 2 at the distance of this galaxy, and has been reproduced from exposures made with the FORS2 multi-mode instrument at the 8.2-m VLT KUEYEN telescope at Paranal. The full field may be seen in PR Photo 05b/00. Technical information about this photo is available below. The galaxy Centaurus A (NGC 5128) is one of the most studied objects in the southern sky. The unique appearance of this galaxy was already noticed by the famous British astronomer John Herschel in 1847 who catalogued the southern skies and made a comprehensive list of "nebulae". A fine photo of Centaurus A from the VLT was published last year as PR Photo 05b/00. Herschel could

  10. DUSTY WINDS: EXTRAPLANAR POLYCYCLIC AROMATIC HYDROCARBON FEATURES OF NEARBY GALAXIES

    SciTech Connect

    McCormick, Alexander; Veilleux, Sylvain; Rupke, David S. N. E-mail: veilleux@astro.umd.edu

    2013-09-10

    Recent observations have shown the presence of dust and molecular material in galactic winds, but relatively little is known about the distribution of these outflow components. To shed some light on this issue, we have used IRAC images from the Spitzer Space Telescope archive to investigate polycyclic aromatic hydrocarbon (PAH) emission from a sample of 16 local galaxies with known winds. Our focus on nearby sources (median distance 8.6 Mpc) has revealed detailed PAH structure in the winds and allowed us to measure extraplanar PAH emission. We have identified extraplanar PAH features on scales of {approx}0.8-6.0 kpc. We find a nearly linear correlation between the amount of extraplanar PAH emission and the total infrared flux, a proxy for star formation activity in the disk. Our results also indicate a correlation between the height of extraplanar PAH emission and star formation rate surface density, which supports the idea of a surface density threshold on the energy or momentum injection rate for producing detectable extraplanar wind material.

  11. HUBBLE PEEKS INTO A STELLAR NURSERY IN A NEARBY GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    HUBBLE PEEKS INTO A STELLAR NURSERY IN A NEARBY GALAXY NASA's Hubble Space Telescope has peered deep into a neighboring galaxy to reveal details of the formation of new stars. Hubble's target was a newborn star cluster within the Small Magellanic Cloud, a small galaxy that is a satellite of our own Milky Way. The new images show young, brilliant stars cradled within a nebula, or glowing cloud of gas, cataloged as N 81. These massive, recently formed stars inside N 81 are losing material at a high rate, sending out strong stellar winds and shock waves and hollowing out a cocoon within the surrounding nebula. The two most luminous stars, seen in the Hubble image as a very close pair near the center of N 81, emit copious ultraviolet radiation, causing the nebula to glow through fluorescence. Outside the hot, glowing gas is cooler material consisting of hydrogen molecules and dust. Normally this material is invisible, but some of it can be seen in silhouette against the nebular background, as long dust lanes and a small, dark, elliptical-shaped knot. It is believed that the young stars have formed from this cold matter through gravitational contraction. Few features can be seen in N 81 from ground-based telescopes, earning it the informal nick-name 'The Blob.' Astronomers were not sure if just one or a few hot stars were embedded in the cloud, or if it was a stellar nursery containing a large number of less massive stars. Hubble's high-resolution imaging shows the latter to be the case, revealing that numerous young, white-hot stars---easily visible in the color picture---are contained within N 81. This crucial information bears strongly on theories of star formation, and N 81 offers a singular opportunity for a close-up look at the turbulent conditions accompanying the birth of massive stars. The brightest stars in the cluster have a luminosity equal to 300,000 stars like our own Sun. Astronomers are especially keen to study star formation in the Small Magellanic

  12. Physical properties and evolutionary state of the Lyman alpha emitting starburst galaxy IRAS 08339+6517

    NASA Astrophysics Data System (ADS)

    Otí-Floranes, H.; Mas-Hesse, J. M.; Jiménez-Bailón, E.; Schaerer, D.; Hayes, M.; Östlin, G.; Atek, H.; Kunth, D.

    2014-06-01

    Context. Though Lyα emission is one of the most used tracers of massive star formation at high redshift, it is strongly affected by neutral gas radiation transfer effects. A correct understanding of these effects is required to properly quantify the star formation rate along the history of the Universe. Aims: We aim to parameterize the escape of Lyα photons as a function of the galaxy properties, in order to properly calibrate the Lyα luminosity as a tracer of star formation intensity at any age of the Universe. Methods: We have embarked on a program to study the properties of the Lyα emission (spectral profile, spatial distribution, relation to Balmer lines intensity,...) in a number of starburst galaxies in the Local Universe. The study is based on Hubble Space Telescope spectroscopic and imaging observations at various wavelengths, X-ray data, and ground-based spectroscopy, complemented with the use of evolutionary population synthesis models. Results: We present here the results obtained for one of those sources, IRAS 08339+6517, a strong Lyα emitter in the Local Universe, which is undergoing an intense episode of massive star formation. We have characterized the properties of the starburst, which transformed 1.4 × 108 M⊙ of gas into stars around 5-6 Myr ago. The mechanical energy released by the central super stellar cluster (SSC), located in the core of the starburst, has created a cavity devoid of gas and dust around it, leaving a clean path through which the UV continuum of the SSC is observed, with almost no extinction. While the average extinction affecting the stellar continuum is significantly larger out of the cavity, with E(B - V) = 0.15 on average, we have not found any evidence for regions with very large extinctions, which could be hiding some young, massive stars not contributing to the global UV continuum. The observed soft and hard X-ray emissions are consistent with this scenario, being originated by the interstellar medium heated by

  13. 2D kinematical study in local luminous compact blue galaxies. Starburst origin in UCM2325+2318

    NASA Astrophysics Data System (ADS)

    Castillo-Morales, A.; Pérez-Gallego, J.; Gallego, J.; Guzmán, R.; Castander, F.; Garland, C.; Gruel, N.; Pisano, D. J.; Muñoz-Mateos, J. C.; Ocaña, F.; Zamorano, J.

    2013-05-01

    Luminous Compact Blue Galaxies (LCBGs) are small, but vigorously star forming galaxies. Their presence at different redshifts denotes their cosmological relevance and implies that local starburst galaxies, when properly selected, are unique laboratories for studying the complex ecosystem of the star formation process over time. We have selected a representative sample of 22 LCBGs from the SDSS and UCM databases which, although small, provides an excellent reference for comparison with current and future surveys of similar starbursts at high-z. We are carrying out a 2D optical spectroscopic study of this LCBG sample, including spatially resolved maps of kinematics, extinction, SFR and metallicity. This will help us to answer questions regarding the nature of these objects. In this poster we show our results on the kinematical study (Pérez-Gallego et al. 2011) which allows us to classify these galaxies into three different classes: rotating disk (RD) 48%, perturbed rotation (PR) 28% and complex kinematics (CK) 24%. We find 5% of objects show evidence of a recent major merger, 10% of a minor merger, and 45% of a companion. This argues in favor of ongoing interactions with close companions as a mechanism for the enhanced star formation activity in these galaxies. We find only 5% of objects with clear evidence of AGN activity, and 27% with kinematics consistent with SN-driven galactic winds. Therefore, a different mechanism may be responsible for quenching the star formation in LCBGs. The detailed analysis of the physical properties for each galaxy in the sample is on progress and we show in this poster the results on UCM2325+2318 as a prototype LCBG. Between the possible mechanisms to explain the starburst activity in this galaxy, our 2D spectroscopic data support the scenario of an on-going interaction with the possibility for clump B to be the dwarf satellite galaxy (Castillo-Morales et al. 2011, Pérez-Gallego et al. 2010).

  14. An enhanced fraction of starbursting galaxies among high Eddington ratio AGNs

    NASA Astrophysics Data System (ADS)

    Bernhard, E.; Mullaney, J. R.; Daddi, E.; Ciesla, L.; Schreiber, C.

    2016-07-01

    We investigate the star-forming properties of 1620 X-ray selected active galactic nuclei (AGN) host galaxies as a function of their specific X-ray luminosity (i.e. X-ray luminosity per unit host stellar mass) - a proxy of the Eddington ratio. Our motivation is to determine whether there is any evidence of a suppression of star formation at high Eddington ratios, which may hint towards `AGN feedback' effects. Star formation rates (SFRs) are derived from fits to Herschel-measured far-infrared spectral energy distributions, taking into account any contamination from the AGN. Herschel-undetected AGNs are included via stacking analyses to provide average SFRs in bins of redshift and specific X-ray luminosity (spanning 0.01 lesssim L_X/M_{ast } lesssim 100 L_{{⊙}} M_{{⊙}}^{-1}). After normalizing for the effects of mass and redshift arising from the evolving galaxy main sequence, we find that the SFRs of high specific luminosity AGNs are slightly enhanced compared to their lower specific luminosity counterparts. This suggests that the SFR distribution of AGN hosts changes with specific X-ray luminosity, a result reinforced by our finding of a significantly higher fraction of starbursting hosts among high specific luminosity AGNs compared to that of the general star-forming galaxy population (i.e. 8-10 per cent versus 3 per cent). Contrary to our original motivation, our findings suggest that high specific luminosity AGNs are more likely to reside in galaxies with enhanced levels of star formation.

  15. A Statistical Approach to Galaxy Cluster Gas Inhomogeneity: Chandra Observations of Nearby Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Reese, Erik D.; Kawahara, H.; Kitayama, T.; Sasaki, S.; Suto, Y.

    2009-01-01

    Motivated by cosmological hydrodynamic simulations, the intracluster medium (ICM) inhomogeneity of galaxy clusters is modeled statistically with a lognormal model for density inhomogeneity. Through mock observations of synthetic clusters the relationship between density inhomogeneities and that of the X-ray surface brightness has been developed. This enables one to infer the statistical properties of the fluctuations of the underlying three-dimensional density distribution of real galaxy clusters from X-ray observations. We explore inhomogeneity in the intracluster medium by applying the above methodology to Chandra observations of a sample of nearby galaxy clusters. We also consider extensions of the model, including Poissonian effects and compare this hybrid lognormal-Poisson model to the nearby cluster Chandra data. EDR gratefully acknowledges support from JSPS (Japan Society for the Promotion of Science) Postdoctoral Fellowhip for Foreign Researchers award P07030. HK is supported by Grands-in-Aid for JSPS of Science Fellows. This work is also supported by Grant-in-Aid for Scientific research of Japanese Ministry of Education, Culture, Sports, Science and Technology (Nos. 20.10466, 19.07030, 16340053, 20340041, and 20540235) and by JSPS Core-to-Core Program "International Research Network for Dark Energy".

  16. THE CARNEGIE-IRVINE GALAXY SURVEY. III. THE THREE-COMPONENT STRUCTURE OF NEARBY ELLIPTICAL GALAXIES

    SciTech Connect

    Huang, Song; Ho, Luis C.; Peng, Chien Y.; Li, Zhao-Yu; Barth, Aaron J.

    2013-03-20

    Motivated by recent developments in our understanding of the formation and evolution of massive galaxies, we explore the detailed photometric structure of a representative sample of 94 bright, nearby elliptical galaxies, using high-quality optical images from the Carnegie-Irvine Galaxy Survey. The sample spans a range of environments and stellar masses, from M{sub *} = 10{sup 10.2} to 10{sup 12.0} M{sub Sun }. We exploit the unique capabilities of two-dimensional image decomposition to explore the possibility that local elliptical galaxies may contain photometrically distinct substructure that can shed light on their evolutionary history. Compared with the traditional one-dimensional approach, these two-dimensional models are capable of consistently recovering the surface brightness distribution and the systematic radial variation of geometric information at the same time. Contrary to conventional perception, we find that the global light distribution of the majority ({approx}>75%) of elliptical galaxies is not well described by a single Sersic function. Instead, we propose that local elliptical galaxies generically contain three subcomponents: a compact (R{sub e} {approx}< 1 kpc) inner component with luminosity fraction f Almost-Equal-To 0.1-0.15; an intermediate-scale (R{sub e} Almost-Equal-To 2.5 kpc) middle component with f Almost-Equal-To 0.2-0.25; and a dominant (f = 0.6), extended (R{sub e} Almost-Equal-To 10 kpc) outer envelope. All subcomponents have average Sersic indices n Almost-Equal-To 1-2, significantly lower than the values typically obtained from single-component fits. The individual subcomponents follow well-defined photometric scaling relations and the stellar mass-size relation. We discuss the physical nature of the substructures and their implications for the formation of massive elliptical galaxies.

  17. Mapping the starburst in blue compact dwarf galaxies. PMAS integral field spectroscopy of Mrk 1418

    NASA Astrophysics Data System (ADS)

    Cairós, L. M.; Caon, N.; Zurita, C.; Kehrig, C.; Weilbacher, P.; Roth, M.

    2009-12-01

    Aims: By means of optical integral field spectroscopy observations, we aim to differentiate and characterize the starburst component in the blue compact dwarf (BCD) galaxy Mrk 1418. In particular we propose to study the stellar and ionized gas morphology, to investigate the ionization mechanism(s) acting in the interstellar medium, and to derive the physical parameters and abundances of the ionized gas. Methods: Integral field spectroscopy observations of Mrk 1418 were carried out with the Potsdam multi-aperture spectrophotometer (PMAS) at the 3.5 m telescope at Calar Alto Observatory. The central 16 arcsec×16 arcsec (1.14 × 1.14 kpc2 at the distance of Mrk 1418) were mapped with a spatial sampling of 1 arcsec; we took data in the 3590-6996 Å spectral range, with a linear dispersion of 3.2 Å per pixel. The seeing was about 1farcs5. From these data we built maps of the most prominent emission lines, namely [O ii], Hβ, [O iii], Hα, [N ii], and [S ii], as well as of several continuum bands, plus maps of the main line ratios: [O iii]/Hβ, [N ii]/Hα, [S ii]/Hα, and Hα/Hβ, and derived the physical parameters and gaseous metal abundances of the different star-forming regions detected in the field of view. Results: Mrk 1418 shows a distorted morphology both in the continuum and in the ionized gas maps; the current star- formation episode is taking place in five knots, distributed around the nucleus of the galaxy. The interstellar medium surrounding these knots is photo-ionized by stars, with no clear evidence for other excitation mechanisms. The galaxy displays an inhomogeneous dust distribution, with the high Hα/Hβ ratio in the central areas indicating a large amount of dust. The oxygen abundances derived for the individual star-forming knots are very similar, suggesting that the ionized interstellar medium is chemically homogeneous in O/H over spatial scales of hundreds of parsecs. This abundance (Z ≈ 0.4 Z⊙ from the empirical calibrations) places Mrk

  18. MAMBO Observations of the COSMOS Field: Probing High Redshift, Dusty Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Carilli, C. L.; Bertoldi, F.; Schinnerer, E.; Voss, H.; Smolcic, V.; Blain, A.; Scoville, N. Z.; Menten, K.; Lutz, D.; Cosmos

    2005-12-01

    The inner 20×20 arcmin2 of the COSMOS field was imaged at 250 GHz (1.2 mm) to an rms noise level of 1 mJy per 11 arcsec beam using the Max-Planck Millimeter Bolometer Array (MAMBO-2) at the IRAM 30-m telescope. We detect 23 sources at significance between 3.5 and 7σ , about half of which are also detected at 1.4 GHz with the VLA with a flux density >3σ = 30 μ Jy. The 250 GHz source areal density in the COSMOS field is comparable to that seen in other deep mm fields. We present the multi-frequency properties of the MAMBO sources, including: (i) HST/ACS i magnitudes (or limits) and morphologies, (ii) ground-based optical and near-IR magnitudes, (iii) XMM X-ray flux densities, and (iv) VLA radio flux densities. We compare radio and optical photometric redshifts, discuss the AGN fraction derived from the X-ray data, and describe the host galaxy properties apparent from the HST and ground based optical imaging. We highlight some relatively bright MAMBO sources that do not show obvious optical counterparts to very faint levels (i'AB > 26.9). These sources could be dusty starburst galaxies at redshifts >3.

  19. Magnetic field surrounding the starburst nucleus of the galaxy M82 from polarized dust emission

    PubMed

    Greaves; Holland; Jenness; Hawarden

    2000-04-13

    Magnetic fields may play an important role in the star-formation process, especially in the central regions of 'starburst' galaxies where star formation is vigorous. But the field directions are very difficult to determine in the dense molecular gas out of which the stars form, so it has hitherto been impossible to test this hypothesis. Dust grains in interstellar clouds tend to be magnetically aligned, and it is possible to determine the alignment direction based on the polarization of optical light due to preferential extinction along the long axes of the aligned grains. This technique works, however, only for diffuse gas, not for the dense molecular gas. Here we report observations of polarized thermal emission from the aligned dust grains in the central region of M82, which directly traces the magnetic field structure (as projected onto the plane of the sky). Organized field lines are seen around the brightest star-forming regions, while in the dusty halo the field lines form a giant magnetic bubble possibly blown out by the galaxy's 'superwind'.

  20. Byurakan-IRAS Galaxy Pairs as Indicators of Starburst and Galaxy Evolution

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.; Sargsyan, L. A.; Mikayelyan, G. A.

    2010-05-01

    The Byurakan-IRAS galaxies (BIG objects; Mickaelian 1995) are the result of a project of optical identifications of IRAS Point Source Catalog (PSC; IRAS 1988) in a 1500 square degree high-galactic latitude (|b|>15°) area based on the Digitized Sky Survey (DSS) images and the Digitized First Byurakan Survey (DFBS, or digitized Markarian survey) low-dispersion spectra. As a result, 1278 galaxies have been identified (as well as galactic objects, Byurakan-IRAS Stars [BIS]), including 42 PSC sources identified with 103 galaxies that make up 30 physical pairs and 12 multiples.

  1. Spectral Analysis and Interpretation of the γ-Ray Emission from the Starburst Galaxy NGC 253

    NASA Astrophysics Data System (ADS)

    Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker, J.; Bernlöhr, K.; Birsin, E.; Biteau, J.; Bochow, A.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Büsching, I.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Gast, H.; Gérard, L.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Göring, D.; Grondin, M.-H.; Häffner, S.; Hague, J. D.; Hahn, J.; Hampf, D.; Harris, J.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Komin, Nu.; Kosack, K.; Kossakowski, R.; Krayzel, F.; Laffon, H.; Lamanna, G.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Moderski, R.; Mohamed, M.; Moulin, E.; Naumann, C. L.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nekrassov, D.; Nguyen, N.; Nicholas, B.; Niemiec, J.; Nolan, S. J.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sheidaei, F.; Skilton, J. L.; Sol, H.; Spengler, G.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorobiov, S.; Vorster, M.; Wagner, S. J.; Ward, M.; White, R.; Wierzcholska, A.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.; H. E. S. S. Collaboration

    2012-10-01

    Very high energy (VHE; E >= 100 GeV) and high-energy (HE; 100 MeV <= E <= 100 GeV) data from γ-ray observations performed with the H.E.S.S. telescope array and the Fermi-LAT instrument, respectively, are analyzed in order to investigate the non-thermal processes in the starburst galaxy NGC 253. The VHE γ-ray data can be described by a power law in energy with differential photon index Γ = 2.14 ± 0.18stat ± 0.30sys and differential flux normalization at 1 TeV of F 0 = (9.6 ± 1.5stat(+ 5.7, -2.9)sys) × 10-14 TeV-1 cm-2 s-1. A power-law fit to the differential HE γ-ray spectrum reveals a photon index of Γ = 2.24 ± 0.14stat ± 0.03sys and an integral flux between 200 MeV and 200 GeV of F(0.2-200 GeV) = (4.9 ± 1.0stat ± 0.3sys) × 10-9 cm-2 s-1. No evidence for a spectral break or turnover is found over the dynamic range of both the LAT instrument and the H.E.S.S. experiment: a combined fit of a power law to the HE and VHE γ-ray data results in a differential photon index Γ = 2.34 ± 0.03 with a p-value of 30%. The γ-ray observations indicate that at least about 20% of the energy of the cosmic rays (CRs) capable of producing hadronic interactions is channeled into pion production. The smooth alignment between the spectra in the HE and VHE γ-ray domain suggests that the same transport processes dominate in the entire energy range. Advection is most likely responsible for charged particle removal from the starburst nucleus from GeV to multiple TeV energies. In a hadronic scenario for the γ-ray production, the single overall power-law spectrum observed would therefore correspond to the mean energy spectrum produced by the ensemble of CR sources in the starburst region. We dedicate this paper to the memory of our colleague Dalibor Nedbal, who died on 2012 May 15 at the age of 31. Dalibor was universally liked and respected as a scientist and colleague and will be greatly missed.

  2. SPECTRAL ANALYSIS AND INTERPRETATION OF THE {gamma}-RAY EMISSION FROM THE STARBURST GALAXY NGC 253

    SciTech Connect

    Abramowski, A.; Acero, F.; Akhperjanian, A. G.; Anton, G.; Balzer, A.; Brucker, J.; Barnacka, A.; Becherini, Y.; Birsin, E.; Biteau, J.; Brun, F.; Bolmont, J.; Brun, P.; Collaboration: H.E.S.S. Collaboration; and others

    2012-10-01

    Very high energy (VHE; E {>=} 100 GeV) and high-energy (HE; 100 MeV {<=} E {<=} 100 GeV) data from {gamma}-ray observations performed with the H.E.S.S. telescope array and the Fermi-LAT instrument, respectively, are analyzed in order to investigate the non-thermal processes in the starburst galaxy NGC 253. The VHE {gamma}-ray data can be described by a power law in energy with differential photon index {Gamma} = 2.14 {+-} 0.18{sub stat} {+-} 0.30{sub sys} and differential flux normalization at 1 TeV of F{sub 0} = (9.6 {+-} 1.5{sub stat}(+ 5.7, -2.9){sub sys}) Multiplication-Sign 10{sup -14} TeV{sup -1} cm{sup -2} s{sup -1}. A power-law fit to the differential HE {gamma}-ray spectrum reveals a photon index of {Gamma} 2.24 {+-} 0.14{sub stat} {+-} 0.03{sub sys} and an integral flux between 200 MeV and 200 GeV of F(0.2-200 GeV) = (4.9 {+-} 1.0{sub stat} {+-} 0.3{sub sys}) Multiplication-Sign 10{sup -9} cm{sup -2} s{sup -1}. No evidence for a spectral break or turnover is found over the dynamic range of both the LAT instrument and the H.E.S.S. experiment: a combined fit of a power law to the HE and VHE {gamma}-ray data results in a differential photon index {Gamma} = 2.34 {+-} 0.03 with a p-value of 30%. The {gamma}-ray observations indicate that at least about 20% of the energy of the cosmic rays (CRs) capable of producing hadronic interactions is channeled into pion production. The smooth alignment between the spectra in the HE and VHE {gamma}-ray domain suggests that the same transport processes dominate in the entire energy range. Advection is most likely responsible for charged particle removal from the starburst nucleus from GeV to multiple TeV energies. In a hadronic scenario for the {gamma}-ray production, the single overall power-law spectrum observed would therefore correspond to the mean energy spectrum produced by the ensemble of CR sources in the starburst region.

  3. Byurakan-IRAS galaxies as massive galaxies with nuclear and starburst activity

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg M.; Harutyunyan, Gohar S.

    2013-07-01

    Byurakan-IRAS Galaxies (BIG) (Mickaelian 1995) are the result of optical identifications of IRAS PSC sources at high-galactic latitudes using the First Byurakan Survey (FBS) low-dispersion spectra (Markarian et al. 1989). Among the 1577 targets, 1178 galaxies have been identified. Most are dusty spiral galaxies and there is a number of ULIRGs among these objects. Our spectroscopic observations, carried out with three telescopes (Byurakan Astrophysical Observatory 2.6m, Russian Special Astrophysical Observatory 6m and Observatoire de Haute Provence 1.93m; Mickaelian & Sargsyan 2010), for 172 galaxies, as well as the SDSS DR8 spectra for 83 galaxies make up the list of 255 spectroscopically studied BIG objects. The classification regarding activity type for narrow-line emission galaxies has been carried out using the diagnostic diagrams by Veilleux & Osterbrock (1987). All possible physical characteristics have been measured and/or calculated, including radial velocities and distances, angular and physical sizes, absolute magnitudes and luminosities (both optical and IR). IR luminosities and star-formation rates have been calculated from the IR fluxes (Duc et al. 1997).

  4. The Magnetized Galactic Wind and Synchrotron Halo of the Starburst Dwarf Galaxy IC 10

    NASA Astrophysics Data System (ADS)

    Chyży, Krzysztof T.; Drzazga, Robert T.; Beck, Rainer; Urbanik, Marek; Heesen, Volker; Bomans, Dominik J.

    2016-03-01

    We aim to explore whether strong magnetic fields can be effectively generated in low-mass dwarf galaxies and, if so, whether such fields can be affected by galactic outflows and spread out into the intergalactic medium (IGM). We performed a radio continuum polarimetry study of IC 10, the nearest starbursting dwarf galaxy, using a combination of multifrequency interferometric (VLA) and single-dish (Effelsberg) observations. VLA observations at 1.43 GHz reveal an extensive and almost spherical radio halo of IC 10 in total intensity, extending twice more than the infrared-emitting galactic disk. The halo is magnetized with a magnetic field strength of 7 μG in the outermost parts. Locally, the magnetic field reaches about 29 μ {{G}} in H ii complexes, becomes more ordered, and weakens to 22 μ {{G}} in the synchrotron superbubble and to 7-10 μG within H i holes. At the higher frequency of 4.86 GHz, we found a large-scale magnetic field structure of X-shaped morphology, similar to that observed in several edge-on spiral galaxies. The X-shaped magnetic structure can be caused by the galactic wind, advecting magnetic fields injected into the interstellar medium by stellar winds and supernova explosions. The radio continuum scale heights at 1.43 GHz indicate the bulk speed of cosmic-ray electrons outflowing from H ii complexes of about 60 km s-1, exceeding the escape velocity of 40 km s-1. Hence, the magnetized galactic wind in IC 10 inflates the extensive radio halo visible at 1.43 GHz and can seed the IGM with both random and ordered magnetic fields. These are signatures of intense material feedback onto the IGM, expected to be prevalent in the protogalaxies of the early universe.

  5. High resolution radio and optical observations of the central starburst in the low-metallicity dwarf galaxy II Zw 40

    SciTech Connect

    Kepley, Amanda A.; Reines, Amy E.; Johnson, Kelsey E.; Walker, Lisa May E-mail: areines@nrao.edu E-mail: lisamay@virginia.edu

    2014-02-01

    The extent to which star formation varies in galaxies with low masses, low metallicities, and high star formation rate surface densities is not well constrained. To gain insight into star formation under these physical conditions, this paper estimates the ionizing photon fluxes, masses, and ages for young massive clusters in the central region of II Zw 40—the prototypical low-metallicity dwarf starburst galaxy—from radio continuum and optical observations. Discrete, cluster-sized sources only account for half the total radio continuum emission; the remainder is diffuse. The young (≲ 5 Myr) central burst has a star formation rate surface density that significantly exceeds that of the Milky Way. Three of the 13 sources have ionizing photon fluxes (and thus masses) greater than R136 in 30 Doradus. Although isolating the effects of galaxy mass and metallicity is difficult, the H II region luminosity function and the internal extinction in the center of II Zw 40 appear to be primarily driven by a merger-related starburst. The relatively flat H II region luminosity function may be the result of an increase in interstellar medium pressure during the merger and the internal extinction is similar to that generated by the clumpy and porous dust in other starburst galaxies.

  6. Mapping Nearby Galaxies at APO: The MaNGA IFU Galaxy Survey

    NASA Astrophysics Data System (ADS)

    Law, David R.; MaNGA Team

    2014-01-01

    MaNGA is a new survey that will begin in August 2014 as part of SDSS-IV with the aim of obtaining integral-field spectroscopy for an unprecedented sample of 10,000 nearby galaxies. MaNGA's key goals are to understand the "life cycle" of present day galaxies from imprinted clues of their birth and assembly, through their ongoing growth via star formation and merging, to their death from quenching at late times. To achieve these goals, MaNGA will channel the impressive capabilities of the SDSS-III BOSS spectrographs in a fundamentally new direction by marshaling the unique power of 2D spectroscopy. MaNGA will deploy 17 pluggable Integral Field Units (IFUs) made by grouping fibers into hexagonal bundles ranging from 19 to 127 fibers each. The spectra obtained by MaNGA will cover the wavelength range 3600-10,000 Angstroms (with a velocity resolution of ~ 60 km/s) and will characterize the internal composition and the dynamical state of a sample of 10,000 galaxies with stellar masses greater than 10^9 Msun and an average redshift of z ~ 0.03. Such IFU observations enable a leap forward because they provide an added dimension to the information available for each galaxy. MaNGA will provide two-dimensional maps of stellar velocity and velocity dispersion, mean stellar age and star formation history, stellar metallicity, element abundance ratio, stellar mass surface density, ionized gas velocity, ionized gas metallicity, star formation rate, and dust extinction for a statistically powerful sample. This legacy dataset will address urgent questions in our understanding of galaxy formation, including 1) The formation history of galaxy subcomponents, including the disk, bulge, and dark matter halo, 2) The nature of present-day galaxy growth via merging and gas accretion, and 3) The processes responsible for terminating star formation in galaxies. Finally, MaNGA will also play a vital role in the coming era of advanced IFU instrumentation, serving as the low-z anchor for

  7. Dark matter searches with Cherenkov telescopes: nearby dwarf galaxies or local galaxy clusters?

    NASA Astrophysics Data System (ADS)

    Sánchez-Conde, Miguel A.; Cannoni, Mirco; Zandanel, Fabio; Gómez, Mario E.; Prada, Francisco

    2011-12-01

    In this paper, we compare dwarf galaxies and galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies (Draco, Ursa Minor, Wilman 1 and Segue 1) and local galaxy clusters (Perseus, Coma, Ophiuchus, Virgo, Fornax, NGC 5813 and NGC 5846), and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure. Willman 1 appears as the best candidate in the sample. However, its mass modeling is still rather uncertain, so probably other candidates with less uncertainties and quite similar fluxes, namely Ursa Minor and Segue 1, might be better options. As for galaxy clusters, Virgo represents the one with the highest flux. However, its large spatial extension can be a serious handicap for IACT observations and posterior data analysis. Yet, other local galaxy cluster candidates with more moderate emission regions, such as Perseus, may represent good alternatives. After comparing dwarfs and clusters, we found that the former exhibit annihilation flux profiles that, at the center, are roughly one order of magnitude higher than those of clusters, although galaxy clusters can yield similar, or even higher, integrated fluxes for the whole object once substructure is taken into account. Even when any of these objects are strictly point-like according to the properties of their annihilation signals, we conclude that dwarf galaxies are best suited for observational strategies based on the search of point-like sources, while galaxy clusters represent best targets for analyses that can deal with rather extended emissions. Finally, we study the detection prospects for present and future IACTs in the framework of the constrained minimal supersymmetric standard model. We

  8. Dark Matter Searches with Cherenkov Telescopes: Nearby Dwarf Galaxies or Local Galaxy Clusters?

    SciTech Connect

    Sanchez-Conde, Miguel A.; Cannoni, Mirco; Zandanel, Fabio; Gomez, Mario E.; Prada, Francisco; /IAA, Granada

    2012-06-06

    In this paper, we compare dwarf galaxies and galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies (Draco, Ursa Minor, Wilman 1 and Segue 1) and local galaxy clusters (Perseus, Coma, Ophiuchus, Virgo, Fornax, NGC 5813 and NGC 5846), and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure. Willman 1 appears as the best candidate in the sample. However, its mass modeling is still rather uncertain, so probably other candidates with less uncertainties and quite similar fluxes, namely Ursa Minor and Segue 1, might be better options. As for galaxy clusters, Virgo represents the one with the highest flux. However, its large spatial extension can be a serious handicap for IACT observations and posterior data analysis. Yet, other local galaxy cluster candidates with more moderate emission regions, such as Perseus, may represent good alternatives. After comparing dwarfs and clusters, we found that the former exhibit annihilation flux profiles that, at the center, are roughly one order of magnitude higher than those of clusters, although galaxy clusters can yield similar, or even higher, integrated fluxes for the whole object once substructure is taken into account. Even when any of these objects are strictly point-like according to the properties of their annihilation signals, we conclude that dwarf galaxies are best suited for observational strategies based on the search of point-like sources, while galaxy clusters represent best targets for analyses that can deal with rather extended emissions. Finally, we study the detection prospects for present and future IACTs in the framework of the constrained minimal supersymmetric standard model. We

  9. Feedback Mechanisms of Starbursts and AGNs through Molecular Outflows

    NASA Astrophysics Data System (ADS)

    Matsushita, S.; Krips, M.; Lim, J.; Muller, S.; Tsai, A.-L.

    2013-10-01

    Our deep molecular line images of nearby starburst galaxies and AGNs exhibit molecular outflows in most galaxies, and have revealed that the molecular outflows co-exist with outflows or jets seen in other wavelengths. In case of starbursts, X-ray outflows have higher energy and pressure than those of molecular outflows, suggesting that plasma outflows are blowing the molecular gas away from starburst regions, which suggests a strong negative feedback. On the other hand, current starburst regions in M82 can be seen at the inner edge of an expanding molecular bubble, suggesting a positive feedback. In case of AGNs, jets seem to entrain the surrounding molecular gas away from the AGNs, suggesting a negative feedback.

  10. THE LYMAN ALPHA MORPHOLOGY OF LOCAL STARBURST GALAXIES: RELEASE OF CALIBRATED IMAGES

    SciTech Connect

    Oestlin, Goeran; Hayes, Matthew; Kunth, Daniel; Atek, Hakim; Mas-Hesse, J. Miguel; Leitherer, Claus; Petrosian, Artashes E-mail: matthew.hayes@unige.ch

    2009-09-15

    We present reduced and calibrated high resolution Lyman-alpha (Ly{alpha}) images for a sample of six local star-forming galaxies. Targets were selected to represent a range in luminosity and metallicity and to include both known Ly{alpha} emitters and nonemitters. Far ultraviolet imaging was carried out with the Solar Blind Channel of the Advanced Camera for Surveys on the Hubble Space Telescope (HST) in the F122M (Ly{alpha} online) and F140LP (continuum) filters. The resulting Ly{alpha} images are the product of careful modeling of both the stellar and nebular continua, facilitated by supporting HST imaging at {lambda} {approx} 2200, 3300, 4400, 5500, H{alpha}, and 8000 A, combined with Starburst 99 evolutionary synthesis models, and prescriptions for dust extinction on the continuum. In all, the resulting morphologies in Ly{alpha}, H{alpha}, and UV continuum are qualitatively very different and we show that the bulk of Ly{alpha} emerges in a diffuse component resulting from resonant scattering events. Ly{alpha} escape fractions, computed from integrated H{alpha} luminosities and recombination theory, are found never to exceed 14%. Internal dust extinction is estimated in each pixel and used to correct Ly{alpha} fluxes. However, the extinction corrections are far too small (by factors from 2.6 to infinity) to reconcile the emerging global Ly{alpha} luminosities with standard recombination predictions. Surprisingly, when comparing the global equivalent widths of Ly{alpha} and H{alpha}, the two quantities appear to be anticorrelated, which may be due to the evolution of mechanical feedback from the starburst. This calls for caution in the interpretation of Ly{alpha} observations in terms of star formation rates. The images presented have a physical resolution 3 orders of magnitude better than attainable at high redshifts from the ground with current instrumentation and our images may therefore serve as useful templates for comparing with observations and modeling of

  11. Star-formation in the central kpc of the starburst/LINER galaxy NGC 1614

    NASA Astrophysics Data System (ADS)

    Olsson, E.; Aalto, S.; Thomasson, M.; Beswick, R.

    2010-04-01

    Aims: The aim is to investigate the star-formation and LINER (low ionization nuclear emission line region) activity within the central kiloparsec of the galaxy NGC 1614. In this paper the radio continuum morphology, which provides a tracer of both nuclear and star-formation activity, and the distribution and dynamics of the cold molecular and atomic gas feeding this activity, are studied. In particular, the nature of an R ≈ 300 pc nuclear ring of star-formation and its relationship to the LINER activity in NGC 1614 is addressed. Methods: A high angular resolution, multi-wavelength study of the LINER galaxy NGC 1614 has been performed. Deep observations of the CO 1-0 spectral line were performed using the Owens Valley Radio Observatory (OVRO). These data have been complemented by extensive multi-frequency radio continuum and Hi absorption observations using the Very Large Array (VLA) and Multi-Element Radio Linked Interferometer Network (MERLIN). Results: Toward the center of NGC 1614, we have detected a ring of radio continuum emission with a radius of 300 pc. This ring is coincident with previous radio and Paα observations. The dynamical mass of the ring based on Hi absorption is 3.1 × 109 M⊙. The peak of the integrated CO 1-0 emission is shifted by 1” to the north-west of the ring center. An upper limit to the molecular gas mass in the ring region is ~1.7 × 109 M⊙. Inside the ring, there is a north to south elongated 1.4 GHz radio continuum feature, with a nuclear peak. This peak is also seen in the 5 GHz radio continuum and in the CO. Conclusions: We suggest that the R = 300 pc star forming ring represents the radius of a dynamical resonance - as an alternative to the scenario that the starburst is propagating outwards from the center into a molecular ring. The ring-like appearance is probably part of a spiral structure. Substantial amounts of molecular gas have passed the radius of the ring and reached the nuclear region. The nuclear peak seen in 5

  12. AN INITIAL MASS FUNCTION STUDY OF THE DWARF STARBURST GALAXY NGC 4214

    SciTech Connect

    Andrews, J. E.; Calzetti, D.; Chandar, R.; Lee, J. C.; Whitmore, B.; Elmegreen, B. G.; Kennicutt, R. C.; Kissel, J. S.; Da Silva, Robert L.; Krumholz, Mark R.; O'Connell, R. W.; Dopita, M. A.; Frogel, Jay A.; Kim, Hwihyun E-mail: callzetti@astro.umass.edu

    2013-04-10

    The production rate of ionizing photons in young ({<=}8 Myr), unresolved stellar clusters in the nearby irregular galaxy NGC 4214 is probed using multi-wavelength Hubble Space Telescope WFC3 data. We normalize the ionizing photon rate by the cluster mass to investigate the upper end of the stellar initial mass function (IMF). We have found that within the uncertainties the upper end of the stellar IMF appears to be universal in this galaxy, and that deviations from a universal IMF can be attributed to stochastic sampling of stars in clusters with masses {approx}<10{sup 3} M{sub Sun }. Furthermore, we have found that there does not seem to be a dependence of the maximum stellar mass on the cluster mass. We have also found that for massive clusters, feedback may cause an underrepresentation in H{alpha} luminosities, which needs to be taken into account when conducting this type of analysis.

  13. GALAXY GROWTH BY MERGING IN THE NEARBY UNIVERSE

    SciTech Connect

    Jiang Tao; Hogg, David W.; Blanton, Michael R.

    2012-11-10

    We measure the mass growth rate by merging for a wide range of galaxy types. We present the small-scale (0.014 h {sup -1} {sub 70} Mpc < r < 11 h {sub 70} {sup -1} Mpc) projected cross-correlation functions w(r {sub p}) of galaxy subsamples from the spectroscopic sample of the NYU Value-Added Galaxy Catalog (5 Multiplication-Sign 10{sup 5} galaxies of redshifts 0.03 < z < 0.15) with galaxy subsamples from the Sloan Digital Sky Survey imaging (4 Multiplication-Sign 10{sup 7} galaxies). We use smooth fits to de-project the two-dimensional functions w(r {sub p}) to obtain smooth three-dimensional real-space cross-correlation functions {xi}(r) for each of several spectroscopic subsamples with each of several imaging subsamples. Because close pairs are expected to merge, the three-space functions and dynamical evolution time estimates provide galaxy accretion rates. We find that the accretion onto massive blue galaxies and onto red galaxies is dominated by red companions, and that onto small-mass blue galaxies, red and blue galaxies make comparable contributions. We integrate over all types of companions and find that at fixed stellar mass, the total fractional accretion rates onto red galaxies ({approx}3 h {sub 70} percent per Gyr) are greater than that onto blue galaxies ({approx}1 h {sub 70} percent per Gyr). These rates are almost certainly overestimates because we have assumed that all close pairs merge as quickly as the merger time that we used. One conclusion of this work is that if the total growth of red galaxies from z = 1 to z = 0 is mainly due to merging, the merger rates must have been higher in the past.

  14. 3D structure of nearby groups of galaxies

    NASA Astrophysics Data System (ADS)

    Makarova, L.; Makarov, D.; Klypin, A.; Gottlöber, S.

    2016-10-01

    Using high accuracy distance estimates, we study the three-dimensional distribution of galaxies in five galaxy groups at a distance less than 5 Mpc from the Milky Way. Due to proximity of these groups our sample of galaxies is nearly complete down to extremely small dwarf galaxies with absolute magnitudes M B = -12. We find that the average number-density profile of the groups shows a steep power-law decline dn/dV ˜ R-3 at distances R=(100-500) kpc consistent with predictions of the standard cosmological model. We also find that there is no indication of a truncation or a cutoff in the density at the expected virial radius: the density profile extends at least to 1.5 Mpc. Vast majority of galaxies within 1.5 Mpc radius around group centres are gas-rich star-forming galaxies. Early-type galaxies are found only in the central ˜ 300 kpc region. Lack of dwarf spheroidal and dwarf elliptical galaxies in the field and in the outskirts of large groups is a clear indication that these galaxies experienced morphological transformation when they came close to the central region of forming galaxy group.

  15. Hot Gas and AGN Feedback in Galaxies and Nearby Groups

    NASA Astrophysics Data System (ADS)

    Jones, Christine; Forman, William; Bogdan, Akos; Randall, Scott; Kraft, Ralph; Churazov, Eugene

    2013-07-01

    Massive galaxies harbor a supermassive black hole at their centers. At high redshifts, these galaxies experienced a very active quasar phase, when, as their black holes grew by accretion, they produced enormous amounts of energy. At the present epoch, these black holes still undergo occasional outbursts, although the mode of their energy release is primarily mechanical rather than radiative. The energy from these outbursts can reheat the cooling gas in the galaxy cores and maintain the red and dead nature of the early-type galaxies. These outbursts also can have dramatic effects on the galaxy-scale hot coronae found in the more massive galaxies. We describe research in three areas related to the hot gas around galaxies and their supermassive black holes. First we present examples of galaxies with AGN outbursts that have been studied in detail. Second, we show that X-ray emitting low-luminosity AGN are present in 80% of the galaxies studied. Third, we discuss the first examples of extensive hot gas and dark matter halos in optically faint galaxies.

  16. MUSE Reveals a Recent Merger in the Post-starburst Host Galaxy of the TDE ASASSN-14li

    NASA Astrophysics Data System (ADS)

    Prieto, J. L.; Krühler, T.; Anderson, J. P.; Galbany, L.; Kochanek, C. S.; Aquino, E.; Brown, J. S.; Dong, Subo; Förster, F.; Holoien, T. W.-S.; Kuncarayakti, H.; Maureira, J. C.; Rosales-Ortega, F. F.; Sánchez, S. F.; Shappee, B. J.; Stanek, K. Z.

    2016-10-01

    We present Multi Unit Spectroscopic Explorer (MUSE) integral field spectroscopic observations of the host galaxy (PGC 043234) of one of the closest (z = 0.0206, D ≃ 90 Mpc) and best-studied tidal disruption events (TDEs), ASASSN-14li. The MUSE integral field data reveal asymmetric and filamentary structures that extend up to ≳10 kpc from the post-starburst host galaxy of ASASSN-14li. The structures are traced only through the strong nebular [O iii] λ5007, [N ii] λ6584, and Hα emission lines. The total off-nuclear [O iii] λ5007 luminosity is 4.7 × 1039 erg s‑1, and the ionized H mass is ∼ {10}4(500/{n}{{e}}) {M}ȯ . Based on the Baldwin–Phillips–Terlevich diagram, the nebular emission can be driven by either AGN photoionization or shock excitation, with AGN photoionization favored given the narrow intrinsic line widths. The emission line ratios and spatial distribution strongly resemble ionization nebulae around fading AGNs such as IC 2497 (Hanny's Voorwerp) and ionization “cones” around Seyfert 2 nuclei. The morphology of the emission line filaments strongly suggest that PGC 043234 is a recent merger, which likely triggered a strong starburst and AGN activity leading to the post-starburst spectral signatures and the extended nebular emission line features we see today. We briefly discuss the implications of these observations in the context of the strongly enhanced TDE rates observed in post-starburst galaxies and their connection to enhanced theoretical TDE rates produced by supermassive black hole binaries.

  17. Constraints on decaying dark matter from Fermi observations of nearby galaxies and clusters

    SciTech Connect

    Dugger, Leanna; Profumo, Stefano; Jeltema, Tesla E. E-mail: tesla@ucolick.org

    2010-12-01

    We analyze the impact of Fermi gamma-ray observations (primarily non-detections) of selected nearby galaxies, including dwarf spheroidals, and of clusters of galaxies on decaying dark matter models. We show that the fact that galaxy clusters do not shine in gamma rays puts the most stringent limits available to-date on the lifetime of dark matter particles for a wide range of particle masses and decay final states. In particular, our results put strong constraints on the possibility of ascribing to decaying dark matter both the increasing positron fraction reported by PAMELA and the high-energy feature in the electron-positron spectrum measured by Fermi. Observations of nearby dwarf galaxies and of the Andromeda Galaxy (M31) do not provide as strong limits as those from galaxy clusters, while still improving on previous constraints in some cases.

  18. STAR-FORMING GALAXY EVOLUTION IN NEARBY RICH CLUSTERS

    SciTech Connect

    Tyler, K. D.; Rieke, G. H.; Bai, L.

    2013-08-20

    Dense environments are known to quench star formation in galaxies, but it is still unknown what mechanism(s) are directly responsible. In this paper, we study the star formation of galaxies in A2029 and compare it to that of Coma, combining indicators at 24 {mu}m, H{alpha}, and UV down to rates of 0.03 M{sub Sun} yr{sup -1}. We show that A2029's star-forming galaxies follow the same mass-SFR relation as the field. The Coma cluster, on the other hand, has a population of galaxies with star formation rates (SFRs) significantly lower than the field mass-SFR relation, indicative of galaxies in the process of being quenched. Over half of these galaxies also host active galactic nuclei. Ram-pressure stripping and starvation/strangulation are the most likely mechanisms for suppressing the star formation in these galaxies, but we are unable to disentangle which is dominating. The differences we see between the two clusters' populations of star-forming galaxies may be related to their accretion histories, with A2029 having accreted its star-forming galaxies more recently than Coma. Additionally, many early-type galaxies in A2029 are detected at 24 {mu}m and/or in the far-UV, but this emission is not directly related to star formation. Similar galaxies have probably been classified as star forming in previous studies of dense clusters, possibly obscuring some of the effects of the cluster environment on true star-forming galaxies.

  19. Nearby galaxies as pointers to a better theory of cosmic evolution.

    PubMed

    Peebles, P J E; Nusser, Adi

    2010-06-01

    The great advances in the network of cosmological tests show that the relativistic Big Bang theory is a good description of our expanding Universe. However, the properties of nearby galaxies that can be observed in greatest detail suggest that a better theory would describe a mechanism by which matter is more rapidly gathered into galaxies and groups of galaxies. This more rapid growth occurs in some theoretical ideas now under discussion.

  20. Nearby galaxies as pointers to a better theory of cosmic evolution.

    PubMed

    Peebles, P J E; Nusser, Adi

    2010-06-01

    The great advances in the network of cosmological tests show that the relativistic Big Bang theory is a good description of our expanding Universe. However, the properties of nearby galaxies that can be observed in greatest detail suggest that a better theory would describe a mechanism by which matter is more rapidly gathered into galaxies and groups of galaxies. This more rapid growth occurs in some theoretical ideas now under discussion. PMID:20520705

  1. Large-Field CO(J = 1→0) Observations of the Starburst Galaxy M 82

    NASA Astrophysics Data System (ADS)

    Salak, Dragan; Nakai, Naomasa; Miyamoto, Yusuke; Yamauchi, Aya; Tsuru, Takeshi G.

    2013-06-01

    We present large-field (15.7 × 16.9 arcmin2) CO(J = 1→0) observations of the starburst galaxy M 82, at an angular resolution of 22" with the NRO 45-m telescope. The CO emission was detected in the galactic disk, outflow (driven by the galactic wind) up to ˜2 kpc above the galactic plane in the halo, and in tidal streams. The kinematics of the outflow (including CO line splitting) suggests that it has the shape of a cylinder that is diverging outwards. The mass and kinetic energy of the molecular gas outflow are estimated to be (0.26-1.0) × 109 M⊙ and (1-4) × 1056 erg. A clump of CO gas was discovered 3.5 kpc above the galactic plane; it coincides with a dark lane previously found in X-ray observations, and a peak in H I emission. A comparison with H I, hot molecular hydrogen and dust suggests that the molecular gas shows signatures of warm and cool components in the outflow and tidal streams, respectively.

  2. Numerical Models of Starburst Galaxies: A Study of Outflows and ISM Morphology in Galactic Cores

    NASA Astrophysics Data System (ADS)

    Tanner, Ryan; Cecil, G. N.; Heitsch, F.

    2014-01-01

    Starbursts and AGN winds in galaxy cores can produce large scale outflows. Whether any given outburst can create an outflow depends on several variables including the rate at which the energy is injected into the interstellar medium (ISM), the distribution of clouds with in the ISM, and the overall shape of the ISM. Previous simulations by Cooper et al. (2008) reproduce linear filaments like that in M 82, but were limited in the parameter space that they could explore. We have modified the public Athena hydro code (Stone et al. 2008) to greatly reduce the computation time of high resolution 3D simulations similar to Cooper et al. (2008) and to handle accurate gas cooling down to lower molecule-forming temperatures (10 K). We are exploring the parameter space of a galactic “blowout”, the origin and evolution of interesting ISM morphology such as the curved filamentary “towers” observed at the center of NGC 3079, and how different ISM morphologies may influence the outflow. These simulations are being compared with spectral imaging obtained with the Herschel space telescope to study the connection between regions of the cold neutral medium, warm neutral medium, and warm ionized medium. Those observations are being presented in another session of this AAS meeting. Our work is supported by NASA/Herschel and NC Space Grant funding.

  3. Millimeter and submillimeter observations of nearby radio galaxies

    NASA Technical Reports Server (NTRS)

    Knapp, G. R.; Patten, Brian M.

    1991-01-01

    Radio galaxies are often observed to be strong long wavelength infrared sources. Twenty-six radio galaxies with strong compact cores were observed at wavelengths near 1 mm with the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. The detections and upper limits establish the presence of excess infrared emission for almost all of the galaxies in the sample. The exceptions are the BL Lac objects, which have smooth continuous spectra from radio to infrared wavelengths. The spectral energy distributions of the infrared emission from the radio galaxies favor a thermal origin due to emission from cool interstellar dust. The amounts of dust inferred to be present approach those observed in large spirals.

  4. Relationship between star formation rate and black hole accretion at z=3: the different contributions in quiescent, normal, and starburst galaxies

    SciTech Connect

    Rodighiero, G.; Franceschini, A.; Baronchelli, I.; Brusa, M.; Delvecchio, I.; Pozzi, F.; Cimatti, A.; Mullaney, J. R.; Lutz, D.; Gruppioni, C.; Silverman, J.

    2015-02-10

    We investigate the co-evolution of the black hole accretion rate (BHAR) and the star formation rate (SFR) in 1.5galaxies displaying a greater diversity of star-forming properties compared to previous studies. We combine X-ray stacking and far-IR photometry of stellar mass-limited samples of normal star-forming, starburst, and quiescent/quenched galaxies in the COSMOS field. We corroborate the existence of a strong correlation between BHAR (i.e., the X-ray luminosity, L{sub X}) and stellar mass (M{sub *}) for normal star-forming galaxies, though we find a steeper relation than previously reported. We find that starbursts show a factor of three enhancement in BHAR compared to normal SF galaxies (against a factor of six excess in SFR), while quiescents show a deficit of a factor times 5.5 at a given mass. One possible interpretation of this is that the starburst phase does not coincide with cosmologically relevant BH growth, or that starburst-inducing mergers are more efficient at boosting SFR than BHAR. Contrary to studies based on smaller samples, we find that the BHAR/SFR ratio of main-sequence (MS) galaxies is not mass invariant, but scales weakly as M{sub ∗}{sup 0.43±0.09}, implying faster BH growth in more massive galaxies at z∼2. Furthermore, BHAR/SFR during the starburst is a factor of two lower than in MS galaxies, at odds with the predictions of hydrodynamical simulations of merger galaxies that foresee a sudden enhancement of L{sub X}/SFR during the merger. Finally, we estimate that the bulk of the accretion density of the universe at z∼2 is associated with normal star-forming systems, with only ∼6(±1)% and ∼11(±1)% associated with starburst and quiescent galaxies, respectively.

  5. HUNTING FOR SUPERMASSIVE BLACK HOLES IN NEARBY GALAXIES WITH THE HOBBY–EBERLY TELESCOPE

    SciTech Connect

    Bosch, Remco C. E. van den; Yıldırım, Akin; Gebhardt, Karl; Walsh, Jonelle L.; Gültekin, Kayhan

    2015-05-15

    We have conducted an optical long-slit spectroscopic survey of 1022 galaxies using the 10 m Hobby–Eberly Telescope (HET) at McDonald Observatory. The main goal of the HET Massive Galaxy Survey (HETMGS) is to find nearby galaxies that are suitable for black hole mass measurements. In order to measure accurately the black hole mass, one should kinematically resolve the region where the black hole dominates the gravitational potential. For most galaxies, this region is much less than an arcsecond. Thus, black hole masses are best measured in nearby galaxies with telescopes that obtain high spatial resolution. The HETMGS focuses on those galaxies predicted to have the largest sphere-of-influence, based on published stellar velocity dispersions or the galaxy fundamental plane. To ensure coverage over galaxy types, the survey targets those galaxies across a face-on projection of the fundamental plane. We present the sample selection and resulting data products from the long-slit observations, including central stellar kinematics and emission line ratios. The full data set, including spectra and resolved kinematics, is available online. Additionally, we show that the current crop of black hole masses are highly biased toward dense galaxies and that especially large disks and low dispersion galaxies are under-represented. This survey provides the necessary groundwork for future systematic black hole mass measurement campaigns.

  6. Hunting for Supermassive Black Holes in Nearby Galaxies With the Hobby-Eberly Telescope

    NASA Astrophysics Data System (ADS)

    van den Bosch, Remco C. E.; Gebhardt, Karl; Gültekin, Kayhan; Yıldırım, Akin; Walsh, Jonelle L.

    2015-05-01

    We have conducted an optical long-slit spectroscopic survey of 1022 galaxies using the 10 m Hobby-Eberly Telescope (HET) at McDonald Observatory. The main goal of the HET Massive Galaxy Survey (HETMGS) is to find nearby galaxies that are suitable for black hole mass measurements. In order to measure accurately the black hole mass, one should kinematically resolve the region where the black hole dominates the gravitational potential. For most galaxies, this region is much less than an arcsecond. Thus, black hole masses are best measured in nearby galaxies with telescopes that obtain high spatial resolution. The HETMGS focuses on those galaxies predicted to have the largest sphere-of-influence, based on published stellar velocity dispersions or the galaxy fundamental plane. To ensure coverage over galaxy types, the survey targets those galaxies across a face-on projection of the fundamental plane. We present the sample selection and resulting data products from the long-slit observations, including central stellar kinematics and emission line ratios. The full data set, including spectra and resolved kinematics, is available online. Additionally, we show that the current crop of black hole masses are highly biased toward dense galaxies and that especially large disks and low dispersion galaxies are under-represented. This survey provides the necessary groundwork for future systematic black hole mass measurement campaigns.

  7. VizieR Online Data Catalog: Updated catalog of GALEX nearby galaxies (Bai+, 2015)

    NASA Astrophysics Data System (ADS)

    Bai, Y.; Zou, H.; Liu, J.; Wang, S.

    2015-10-01

    The ultraviolet (UV) catalog of nearby galaxies compiled by Gil de Paz et al. (2007, J/ApJS/173/185) presents the integrated photometry and surface brightness profiles for 1034 nearby galaxies observed by GALEX. We provide an updated catalog of 4138 nearby galaxies based on the latest General Release (GR6/GR7) of GALEX. These galaxies are selected from HyperLeda with apparent diameters larger than 1'. From the surface brightness profiles accurately measured using the deep NUV and FUV images, we have calculated the asymptotic magnitudes, aperture (D25) magnitudes, colors, structural parameters (effective radii and concentration indices), luminosities, and effective surface brightness for these galaxies. Archival optical and infrared photometry from HyperLeda, 2MASS, and IRAS are also integrated into the catalog. Our parameter measurements and some analyses are consistent with those of Paz et al. The (FUV-K) color provides a good criterion to distinguish between early- and late-type galaxies, which can be improved further using the concentration indices. The IRX-β relation is reformulated with our UV-selected nearby galaxies. (3 data files).

  8. Quantitative constraints on starburst cycles in galaxies with stellar masses in the range 108-1010 M⊙

    NASA Astrophysics Data System (ADS)

    Kauffmann, Guinevere

    2014-07-01

    We have used 4000 Å break and HδA indices in combination with SFR/M* derived from emission line flux measurements to constrain the recent star formation histories of galaxies with stellar masses in the range 108-1010 M⊙. The fraction of the total SFR density in galaxies with ongoing bursts is a strong function of stellar mass, declining from 0.85 at a stellar mass of 108 M⊙ to 0.25 for galaxies with M* ˜ 1010 M⊙. Low-mass galaxies are not all young. The distribution of half-mass formation times for galaxies with stellar masses less than 109 M⊙ is broad, spanning the range 1-10 Gyr. The peak-to-trough variation in star formation rate among the bursting population ranges lies in the range 10-25. In low-mass galaxies, the average duration of the bursts is comparable to the dynamical time of the galaxy. Galaxy structure is correlated with estimated burst mass fraction, but in different ways in low- and high-mass galaxies. High-mass galaxies with large burst mass fractions are more centrally concentrated, indicating that bulge formation is at work. In low-mass galaxies, stellar surface densities μ* decrease as a function of Fburst. These results are in good agreement with the observational predictions of Teyssier et al. and lend further credence to the idea that the cuspy halo problem can be solved by energy input from multiple starbursts over the lifetime of the galaxy. We note that there is no compelling evidence for initial mass function variations in the population of star-forming galaxies in the local Universe.

  9. New low surface brightness dwarf galaxies detected around nearby spirals

    NASA Astrophysics Data System (ADS)

    Karachentsev, I. D.; Riepe, P.; Zilch, T.; Blauensteiner, M.; Elvov, M.; Hochleitner, P.; Hubl, B.; Kerschhuber, G.; Küppers, S.; Neyer, F.; Pölzl, R.; Remmel, P.; Schneider, O.; Sparenberg, R.; Trulson, U.; Willems, G.; Ziegler, H.

    2015-10-01

    We conduct a survey of low surface brightness (LSB) satellite galaxies around the Local Volume massive spirals using long exposures with small amateur telescopes. We identified 27 low and very low surface brightness objects around the galaxies NGC672, 891, 1156, 2683, 3344, 4258, 4618, 4631, and 5457 situated within 10 Mpc from us, and found nothing new around NGC2903, 3239, 4214, and 5585. Assuming that the dwarf candidates are the satellites of the neighboring luminous galaxies, their absolute magnitudes are in the range of -8.6 > M B > -13.3, their effective diameters are 0.4-4.7 kpc, and the average surface brightness is 26ṃ1/□″. The mean linear projected separation of the satellite candidates from the host galaxies is 73 kpc. Our spectroscopic observations of two LSB dwarfs with the Russian 6-meter telescope confirm their physical connection to the host galaxies NGC891 and NGC2683.

  10. Imaging of High Redshift Starburst galaxies in the light of Lyman alpha

    NASA Astrophysics Data System (ADS)

    Beckwith, Steven

    1997-07-01

    The PI is the designated director for STScI but has no experience with HST. The purpose of this proposal is to gain experience with the facility by carrying out a modest observational program that is unique and will not conflict with any community programs. The proposed science is divided into priority 1 and priority 2, for 6 + 4 orbits. This division will allow allocation in parts, if the pressure on DDT is large and the total of 10 orbits unusually difficult to schedule. The priority 1 science is rather predictable and, hence, conservative, consisting of the brightest of the objects under study. The priority 2 science is somewhat riskier, because it is more difficult to estimate object brightnesses in the filters to be used on HST. Both priority 1 and priority 2 observations allow for a large degree of serendipity, because the fields are likely to have more starburst galaxies at the observed redshifts that may show up in Lyman alpha. Exploration of the high redshift u niverse and discovery of the most distant objects is still in its infancy. Only recently have the tools been available to detect normal galaxies at redshifts larger than one when the first galaxies were created {Pescarelle et al. 1996; Hu & McMahon 1996; Cowie & Hu 1998; Steidel et al. 1996}. It seems likely that young galaxies will have a variety of different signatures {Franceschini et al. 1998; Guideroni et al. 1997}, so that it will be necessary to use several diverse techniques to uncover all of them: searches at optical, infrared, x-ray, and radio wavelengths, for example. It is already known that many of the optically selected galaxies using the "dropout" technique are reddened by dust {Pettini et al. 1997}. We carried out two surveys for infrared emission-line galaxies by imaging through narrow {Resolving power 100} and broad band filters between 1 and 2.5 microns and identifying objects that appeared brighter in the narrow filters. Our first survey was designed to uncover emission lines at

  11. High-Resolution Near-Infrared Spectroscopy of an Equivalent Width-Selected Sample of Starbursting Dwarf Galaxies

    NASA Technical Reports Server (NTRS)

    Maseda, Michael V.; VanDerWeL, Arjen; DaChuna, Elisabete; Rix, Hans-Walter; Pacafichi, Camilla; Momcheva, Ivelina; Brammer, Gabriel B.; Franx, Marijn; VanDokkum, Pieter; Bell, Eric F.; Ferguson, Harry C.; Fumagalli, Mattia; Grogin, Norman A.; Kocevski, Dale D.; Koekemoer, Anton M.; Lundgren, Britt F.; Marchesini, Danilo; Nelson, Erica J.; Patel, Shannon; Skelton, Rosalind E.; Straughn, Amber N.; Trump, Jonathan R.; Weiner, Benjamin J.; Whitaker, Katherine E.; Wuyts, Stijn

    2013-01-01

    Spectroscopic observations from the Large Binocular Telescope and the Very Large Telescope reveal kinematically narrow lines (approx. 50 km/s) for a sample of 14 Extreme Emission Line Galaxies (EELGs) at redshifts 1.4 < zeta < 2.3. These measurements imply that the total dynamical masses of these systems are low ( 3 × 10(exp 9) M). Their large [O III]5007 equivalent widths (500 - 1100 A) and faint blue continuum emission imply young ages of 10-100 Myr and stellar masses of 10(exp 8)-10(exp 9) M, confirming the presence of a violent starburst. The stellar mass formed in this vigorous starburst phase thus represents a large fraction of the total (dynamical) mass, without a significantly massive underlying population of older stars. The occurrence of such intense events in shallow potentials strongly suggests that supernova-driven winds must be of critical importance in the subsequent evolution of these systems.

  12. Stellar content of nearby galaxies. III - The local group spiral galaxy M33

    NASA Technical Reports Server (NTRS)

    Wilson, Christine D.; Madore, Barry F.; Freedman, Wendy L.

    1990-01-01

    BVRI CCD photometry is presented for stars brighter than V = 21 mag in four fields in the nearby spiral galaxy M33. V vs (B - V) and I vs (V - I) color-magnitude diagrams clearly show both a young stellar population (as indicated by the blue main sequence and red supergiant plumes) as well as an intermediate-age population of asymptotic giant branch stars. Deep photometry in the outer field (where crowding is less severe) reveals a population consistent in color and magnitude with the tip of the first red giant branch. The M33 distance modulus, 24.6 + or - 0.3 mag, derived from this Population II component is consistent with a recent redetermination of the distance modulus found from Population I Cepheid variables. Finally, some evidence is presented for a radial gradient in the average internal reddening for the fields in M33 reported here.

  13. The spatially resolved correlation between [NII] 205 μm line emission and the 24 μm continuum in nearby galaxies

    NASA Astrophysics Data System (ADS)

    Hughes, T. M.; Baes, M.; Schirm, M. R. P.; Parkin, T. J.; Wu, R.; De Looze, I.; Wilson, C. D.; Viaene, S.; Bendo, G. J.; Boselli, A.; Cormier, D.; Ibar, E.; Karczewski, O. Ł.; Lu, N.; Spinoglio, L.

    2016-03-01

    A correlation between the 24 μm continuum and the [Nii] 205 μm line emission may arise if both quantities trace the star formation activity on spatially-resolved scales within a galaxy, yet has so far only been observed in the nearby edge-on spiral galaxy NGC 891. We therefore assess whether the [Nii] 205-24 μm emission correlation has some physical origin or is merely an artefact of line-of-sight projection effects in an edge-on disc. We search for the presence of a correlation in Herschel and Spitzer observations of two nearby face-on galaxies, M 51 and M 83, and the interacting Antennae galaxies NGC 4038 and 4039. We show that not only is this empirical relationship also observed in face-on galaxies, but also that the correlation appears to be governed by the star formation rate (SFR). Both the nuclear starburst in M 83 and the merger-induced star formation in NGC 4038/9 exhibit less [Nii] emission per unit SFR surface density than the normal star-forming discs. These regions of intense star formation exhibit stronger ionization parameters, as traced by the 70/160 μm far-infrared (FIR) colour. These observations suggest the presence of higher ionization lines that may become more important for gas cooling, thereby reducing the observed [Nii] 205 μm line emission in regions with higher star formation rates. Finally, we present a general relation between the [Nii] 205 μm line flux density and SFR density for normal star-forming galaxies, yet note that future studies should extend this analysis by including observations with wider spatial coverage for a larger sample of galaxies.

  14. Millimeter and submillimeter observations of nearby radio galaxies

    SciTech Connect

    Knapp, G.R.; Patten, B.M. Hawaii, University, Honolulu )

    1991-05-01

    Radio galaxies are often observed to be strong long wavelength infrared sources. Twenty-six radio galaxies with strong compact cores were observed at wavelengths near 1 mm with the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. The detections and upper limits establish the presence of excess infrared emission for almost all of the galaxies in the sample. The exceptions are the BL Lac objects, which have smooth continuous spectra from radio to infrared wavelengths. The spectral energy distributions of the infrared emission from the radio galaxies favor a thermal origin due to emission from cool interstellar dust. The amounts of dust inferred to be present approach those observed in large spirals. 55 refs.

  15. MID-INFRARED PROPERTIES OF NEARBY LUMINOUS INFRARED GALAXIES. I. SPITZER INFRARED SPECTROGRAPH SPECTRA FOR THE GOALS SAMPLE

    SciTech Connect

    Stierwalt, S.; Armus, L.; Surace, J. A.; Inami, H.; Petric, A. O.; Diaz-Santos, T.; Haan, S.; Howell, J.; Marshall, J.; Charmandaris, V.; Kim, D. C.; Mazzarella, J. M.; Chan, B.; Spoon, H. W. W.; Veilleux, S.; Evans, A.; Sanders, D. B.; Appleton, P.; Bothun, G.; Bridge, C. R.; and others

    2013-05-01

    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 low resolution Spitzer Infrared Spectrograph spectra covering 5-38 {mu}m and provide a basic analysis of the mid-IR spectral properties observed for nearby LIRGs. In a companion paper, we discuss detailed fits to the spectra and compare the LIRGs to other classes of galaxies. The GOALS sample of 244 nuclei in 180 luminous (10{sup 11} {<=} L {sub IR}/L {sub Sun} < 10{sup 12}) and 22 ultraluminous (L {sub IR}/L {sub Sun} {>=} 10{sup 12}) IR galaxies represents a complete subset of the IRAS Revised Bright Galaxy Sample and covers a range of merger stages, morphologies, and spectral types. The majority (>60%) of the GOALS LIRGs have high 6.2 {mu}m polycyclic aromatic hydrocarbon (PAH) equivalent widths (EQW{sub 6.2{mu}m} > 0.4 {mu}m) and low levels of silicate absorption (s {sub 9.7{mu}m} > -1.0). There is a general trend among the U/LIRGs for both silicate depth and mid-infrared (MIR) slope to increase with increasing L {sub IR}. U/LIRGs in the late to final stages of a merger also have, on average, steeper MIR slopes and higher levels of dust obscuration. Together, these trends suggest that as gas and dust is funneled toward the center of a coalescing merger, the nuclei become more compact and more obscured. As a result, the dust temperature increases also leading to a steeper MIR slope. The sources that depart from these correlations have very low PAH equivalent width (EQW{sub 6.2{mu}m} < 0.1 {mu}m) consistent with their emission being dominated by an active galactic nucleus (AGN) in the MIR. These extremely low PAH EQW sources separate into two distinct types: relatively unobscured sources with a very hot dust component (and thus very shallow MIR slopes) and heavily dust obscured nuclei with a steep temperature gradient. The most heavily dust obscured sources are also the most compact in their MIR

  16. Studying nearby disk galaxies with the CALIFA survey.

    NASA Astrophysics Data System (ADS)

    Marino, R. A.; Gil de Paz, A.; Sánchez, S. F.; Castillo-Morales, A.; CALIFA Team

    CALIFA, the Calar Alto Legacy Integral Field Area survey, will provide the largest and most comprehensive wide-field IFU survey of galaxies carried out to date, addressing several fundamental issues in galactic structure and evolution. We will observe a statistically well-defined sample of ˜ 600 galaxies in the local universe using 210 observing nights already awarded with the PMAS/PPAK integral field spectrophotometer, mounted on the Calar Alto 3.5m telescope. The definining science drivers for the project are: a) star formation and chemical history of galaxies, b) the physical state of the interstellar medium, c) stellar and gas kinematics in galaxies, and d) the influence of the AGNs on galaxy evolution. The CALIFA project comprises researchers from a large number of institutions worldwide: 8 institutions in Spain, 4 in Germany (CAHA funding countries) and 11 elsewhere, and includes a total of 56 researchers. CALIFA will provide a valuable bridge between large single-aperture surveys such as SDSS and more detailed studies of individual galaxies with PPAK (e.g. PINGS), SAURON, VIRUS-P, and other instruments.

  17. 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.

  18. 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.

  19. 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.

  20. Studying nearby disk galaxies with the CALIFA survey

    NASA Astrophysics Data System (ADS)

    Marino, R. A.; Gil de Paz, A.; Sánchez, S. F.; Castillo-Morales, A.

    2011-11-01

    CALIFA, the Calar Alto Legacy Integral Field Area survey, will provide the largest and most comprehensive wide-field IFU survey of galaxies carried out to date, combining the advantages of imaging and spectroscopy we will able to understand the origin for the observed diversity of galaxies, and the physical mechanisms -intrinsic and environmental- that are responsible for the differences as well as similarities between them. We will observe a statistically well-defined sample of ˜ 600 galaxies in the local universe (0.005 < z < 0.03) using 210 observing nights already awarded with the PMAS/PPAK integral field spectrophotometer, mounted on the Calar Alto 3.5 m telescope. PPAK offers a combination of extremely wide field-of-view (> 1 arcmin^2) with a high filling factor in one single pointing (65%), good spectral resolution, and wavelength sensitivity across the optical spectrum. The spectra will be covering the range 3700-7000 Å in two overlapping setups, one in the red (4300-7000 Å) at a spectral resolution of R ˜ 1000 and one in the blue (3700-5000 Å) at R ˜ 2000. The fully reduced and flux calibrated data of this legacy survey will be made available to the public. Some of definining science drivers for the CALIFA project are the star formation and the chemical history of galaxies; the study of the physical state of the interstellar medium; improve our knowledge on the stellar and gas kinematics in galaxies, and understand the influence of the AGNs on galaxy evolution. The CALIFA project comprises researchers from a large number of institutions worldwide: 8 institutions in Spain, 4 in Germany (CAHA funding countries) and 11 elsewhere, and includes a total of 56 researchers. CALIFA will provide a valuable bridge between large single-aperture surveys such as SDSS and more detailed studies of individual galaxies with PPAK (e.g. PINGS), SAURON, VIRUS-P, and other instruments.

  1. THE DWARF STARBURST HOST GALAXY OF A TYPE Ia SUPERNOVA AT z = 1.55 FROM CANDELS

    SciTech Connect

    Frederiksen, Teddy F.; Hjorth, Jens; Maund, Justyn R.; Rodney, Steven A.; Riess, Adam G.; Dahlen, Tomas; Mobasher, Bahram

    2012-12-01

    We present VLT/X-shooter observations of a high-redshift, Type Ia supernova (SN Ia) host galaxy, discovered with HST/WFC3 as part of the CANDELS Supernova project. The galaxy exhibits strong emission lines of Ly{alpha}, [O II], H{beta}, [O III], and H{alpha} at z = 1.54992{sup +0.00008} {sub -0.00004}. From the emission-line fluxes and spectral energy distribution fitting of broadband photometry we rule out activity from an active galactic nucleus and characterize the host galaxy as a young, low-mass, metal-poor, starburst galaxy with low intrinsic extinction and high Ly{alpha} escape fraction. The host galaxy stands out in terms of the star formation, stellar mass, and metallicity compared to its lower redshift counterparts, mainly because of its high specific star formation rate. If valid for a larger sample of high-redshift SN Ia host galaxies, such changes in the host galaxy properties with redshift are of interest because of the potential impact on the use of SN Ia as standard candles in cosmology.

  2. 3D-HST GRISM SPECTROSCOPY OF A GRAVITATIONALLY LENSED, LOW-METALLICITY STARBURST GALAXY AT z = 1.847

    SciTech Connect

    Brammer, Gabriel B.; Sanchez-Janssen, Ruben; Labbe, Ivo; Franx, Marijn; Fumagalli, Mattia; Patel, Shannon; Da Cunha, Elisabete; Rix, Hans-Walter; Schmidt, Kasper B.; Van der Wel, Arjen; Erb, Dawn K.; Lundgren, Britt; Momcheva, Ivelina; Nelson, Erica; Skelton, Rosalind E.; Van Dokkum, Pieter G.; Wake, David A.; Whitaker, Katherine E.; Marchesini, Danilo; Quadri, Ryan

    2012-10-10

    We present Hubble Space Telescope (HST) imaging and spectroscopy of the gravitational lens SL2SJ02176-0513, a cusp arc at z = 1.847. The UV continuum of the lensed galaxy is very blue, which is seemingly at odds with its redder optical colors. The 3D-HST WFC3/G141 near-infrared spectrum of the lens reveals the source of this discrepancy to be extremely strong [O III] {lambda}5007 and H{beta} emission lines with rest-frame equivalent widths of 2000 {+-} 100 and 520 {+-} 40 A, respectively. The source has a stellar mass {approx}10{sup 8} M{sub Sun }, sSFR {approx} 100 Gyr{sup -1}, and detection of [O III] {lambda}4363 yields a metallicity of 12 + log (O/H) = 7.5 {+-} 0.2. We identify local blue compact dwarf analogs to SL2SJ02176-0513, which are among the most metal-poor galaxies in the Sloan Digital Sky Survey. The local analogs resemble the lensed galaxy in many ways, including UV/optical spectral energy distribution, spatial morphology, and emission line equivalent widths and ratios. Common to SL2SJ02176-0513 and its local counterparts is an upturn at mid-IR wavelengths likely arising from hot dust heated by starbursts. The emission lines of SL2SJ02176-0513 are spatially resolved owing to the combination of the lens and the high spatial resolution of HST. The lensed galaxy is composed of two clumps with combined size r{sub e} {approx}300 pc, and we resolve significant differences in UV color and emission line equivalent width between them. Though it has characteristics occasionally attributed to active galactic nuclei, we conclude that SL2SJ02176-0513 is a low-metallicity star-bursting dwarf galaxy. Such galaxies will be found in significant numbers in the full 3D-HST grism survey.

  3. A Starburst in the Core of a Galaxy Cluster: the Dwarf Irregular NGC 1427A in Fornax

    NASA Astrophysics Data System (ADS)

    Mora, Marcelo D.; Chanamé, Julio; Puzia, Thomas H.

    2015-09-01

    Gas-rich galaxies in dense environments such as galaxy clusters and massive groups are affected by a number of possible types of interactions with the cluster environment, which make their evolution radically different than that of field galaxies. The dwarf irregular galaxy NGC 1427A, presently infalling toward the core of the Fornax galaxy cluster for the first time, offers a unique opportunity to study those processes at a level of detail not possible to achieve for galaxies at higher redshifts, when galaxy-scale interactions were more common. Using the spatial resolution of the Hubble Space Telescope/Advanced Camera for Surveys and auxiliary Very Large Telescope/FORS1 ground-based observations, we study the properties of the most recent episodes of star formation in this gas-rich galaxy, the only one of its type near the core of the Fornax cluster. We study the structural and photometric properties of young star cluster complexes in NGC 1427A, identifying 12 bright such complexes with exceptionally blue colors. The comparison of our broadband near-UV/optical photometry with simple stellar population models yields ages below ˜ 4× {10}6 years and stellar masses from a few 1000 up to ˜ 3× {10}4{M}⊙ , slightly dependent on the assumption of cluster metallicity and initial mass function. Their grouping is consistent with hierarchical and fractal star cluster formation. We use deep Hα imaging data to determine the current star formation rate in NGC 1427A and estimate the ratio, Γ, of star formation occurring in these star cluster complexes to that in the entire galaxy. We find Γ to be among the largest such values available in the literature, consistent with starburst galaxies. Thus a large fraction of the current star formation in NGC 1427A is occurring in star clusters, with the peculiar spatial arrangement of such complexes strongly hinting at the possibility that the starburst is being triggered by the passage of the galaxy through the cluster environment

  4. DGSAT: Dwarf Galaxy Survey with Amateur Telescopes. I. Discovery of low surface brightness systems around nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Javanmardi, B.; Martinez-Delgado, D.; Kroupa, P.; Henkel, C.; Crawford, K.; Teuwen, K.; Gabany, R. J.; Hanson, M.; Chonis, T. S.; Neyer, F.

    2016-04-01

    Context. We introduce the Dwarf Galaxy Survey with Amateur Telescopes (DGSAT) project and report the discovery of eleven low surface brightness (LSB) galaxies in the fields of the nearby galaxies NGC 2683, NGC 3628, NGC 4594 (M 104), NGC 4631, NGC 5457 (M 101), and NGC 7814. Aims: The DGSAT project aims to use the potential of small-sized telescopes to probe LSB features around large galaxies and to increase the sample size of the dwarf satellite galaxies in the Local Volume. Methods: Using long exposure images, fields of the target spiral galaxies are explored for extended LSB objects. After identifying dwarf galaxy candidates, their observed properties are extracted by fitting models to their light profiles. Results: We find three, one, three, one, one, and two new LSB galaxies in the fields of NGC 2683, 3628, 4594, 4631, 5457, and 7814, respectively. In addition to the newly found galaxies, we analyse the structural properties of nine already known galaxies. All of these 20 dwarf galaxy candidates have effective surface brightnesses in the range 25.3 ≲ μe ≲ 28.8 mag arcsec-2 and are fit with Sersic profiles with indices n ≲ 1. Assuming that they are in the vicinity of the above mentioned massive galaxies, their r-band absolute magnitudes, their effective radii, and their luminosities are in the ranges -15.6 ≲ Mr ≲ -7.8, 160 pc ≲ Re ≲ 4.1 kpc, and 0.1 × 106 ≲ (L/L⊙)r ≲ 127 × 106, respectively. To determine whether these LSB galaxies are indeed satellites of the above mentioned massive galaxies, their distances need to be determined via further observations. Conclusions: Using small telescopes, we are readily able to detect LSB galaxies with similar properties to the known dwarf galaxies of the Local Group.

  5. Starbursting brightest cluster galaxy: a Herschel view of the massive cluster MACS J1931.8-2634

    NASA Astrophysics Data System (ADS)

    Santos, J. S.; Balestra, I.; Tozzi, P.; Altieri, B.; Valtchanov, I.; Mercurio, A.; Nonino, M.; Yu, Heng; Rosati, P.; Grillo, C.; Medezinski, E.; Biviano, A.

    2016-02-01

    We investigate the dust-obscured star formation (SF) properties of the massive, X-ray-selected galaxy cluster MACS J1931.8-2634 at z = 0.352. Using far-infrared (FIR) imaging in the range 100-500 μm obtained with the Herschel telescope, we extract 31 sources (2σ) within r ˜ 1 Mpc from the brightest cluster galaxy (BCG). Among these sources, we identify six cluster members for which we perform an analysis of their spectral energy distributions (SEDs). We measure total infrared luminosity (LIR), star formation rate (SFR) and dust temperature. The BCG, with LIR = 1.4 × 1012 L⊙ is an ultraluminous infrared galaxy and hosts a type-II active galactic nuclei (AGN). We decompose its FIR SED into AGN and starburst components and find equal contributions from AGN and starburst. We also recompute the SFR of the BCG finding SFR = 150 ± 15 M⊙ yr-1. We search for an isobaric cooling flow in the cool core using Chandra X-ray data, and find no evidence for gas colder than 1.8 keV in the inner 30 kpc, for an upper limit to the instantaneous mass-deposition rate of 58 M⊙ yr-1 at 95 per cent c.l. This value is 3× lower than the SFR in the BCG, suggesting that the on-going SF episode lasts longer than the intracluster medium cooling events.

  6. THE CHANDRA VIEW OF NEARBY X-SHAPED RADIO GALAXIES

    SciTech Connect

    Hodges-Kluck, Edmund J.; Reynolds, Christopher S.; Miller, M. Coleman; Cheung, Chi C.

    2010-02-20

    We present new and archival Chandra X-ray Observatory observations of X-shaped radio galaxies (XRGs) within z {approx} 0.1 alongside a comparison sample of normal double-lobed FR I and II radio galaxies. By fitting elliptical distributions to the observed diffuse hot X-ray emitting atmospheres (either the interstellar or intragroup medium), we find that the ellipticity and the position angle of the hot gas follow that of the stellar light distribution for radio galaxy hosts in general. Moreover, compared to the control sample, we find a strong tendency for X-shaped morphology to be associated with wings directed along the minor axis of the hot gas distribution. Taken at face value, this result favors the hydrodynamic backflow models for the formation of XRGs which naturally explain the geometry; the merger-induced rapid reorientation models make no obvious prediction about orientation.

  7. Star formation quenching in high-redshift large-scale structure: post-starburst galaxies in the Cl 1604 supercluster at z ∼ 0.9

    SciTech Connect

    Wu, Po-Feng; Gal, Roy R.; Lemaux, Brian C.; Kocevski, Dale D.; Lubin, Lori M.; Rumbaugh, Nicholas; Squires, Gordon K.

    2014-09-01

    The Cl 1604 supercluster at z ∼ 0.9 is one of the most extensively studied high-redshift large-scale structures, with more than 500 spectroscopically confirmed members. It consists of eight clusters and groups, with members numbering from a dozen to nearly a hundred, providing a broad range of environments for investigating the large-scale environmental effects on galaxy evolution. Here we examine the properties of 48 post-starburst galaxies in Cl 1604, comparing them to other galaxy populations in the same supercluster. Incorporating photometry from ground-based optical and near-infrared imaging, along with Spitzer mid-infrared observations, we derive stellar masses for all Cl 1604 members. The colors and stellar masses of the K+A galaxies support the idea that they are progenitors of red sequence galaxies. Their morphologies, residual star formation rates, and spatial distributions suggest that galaxy mergers may be the principal mechanism producing post-starburst galaxies. Interaction between galaxies and the dense intracluster medium (ICM) is also effective, but only in the cores of dynamically evolved clusters. The prevalence of post-starburst galaxies in clusters correlates with the dynamical state of the host cluster, as both galaxy mergers and the dense ICM produce post-starburst galaxies. We also investigate the incompleteness and contamination of K+A samples selected by means of Hδ and [O II] equivalent widths. K+A samples may be up to ∼50% incomplete due to the presence of LINERs/Seyferts, and up to ∼30% of K+A galaxies could have substantial star formation activity.

  8. Heaviest Stellar Black Hole Discovered in Nearby Galaxy

    NASA Astrophysics Data System (ADS)

    2007-10-01

    Astronomers have located an exceptionally massive black hole in orbit around a huge companion star. This result has intriguing implications for the evolution and ultimate fate of massive stars. The black hole is part of a binary system in M33, a nearby galaxy about 3 million light years from Earth. By combining data from NASA's Chandra X-ray Observatory and the Gemini telescope on Mauna Kea, Hawaii, the mass of the black hole, known as M33 X-7, was determined to be 15.7 times that of the Sun. This makes M33 X-7 the most massive stellar black hole known. A stellar black hole is formed from the collapse of the core of a massive star at the end of its life. Chandra X-ray Image of M33 X-7 Chandra X-ray Image of M33 X-7 "This discovery raises all sorts of questions about how such a big black hole could have been formed," said Jerome Orosz of San Diego State University, lead author of the paper appearing in the October 18th issue of the journal Nature. M33 X-7 orbits a companion star that eclipses the black hole every three and a half days. The companion star also has an unusually large mass, 70 times that of the Sun. This makes it the most massive companion star in a binary system containing a black hole. Hubble Optical Image of M33 X-7 Hubble Optical Image of M33 X-7 "This is a huge star that is partnered with a huge black hole," said coauthor Jeffrey McClintock of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "Eventually, the companion will also go supernova and then we'll have a pair of black holes." The properties of the M33 X-7 binary system - a massive black hole in a close orbit around a massive companion star - are difficult to explain using conventional models for the evolution of massive stars. The parent star for the black hole must have had a mass greater than the existing companion in order to have formed a black hole before the companion star. Gemini Optical Image of M33 X-7 Gemini Optical Image of M33 X-7 Such a massive star would

  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. Discovery of new variable radio sources in the nucleus of the nearby galaxy messier 82.

    PubMed

    Kronberg, P P; Sramek, R A

    1985-01-01

    Widespread variability has been discovered in a large population of radio sources close to the nucleus of an active galaxy. The galaxy, Messier 82 (M82), and others similar to it show evidence for enhanced nuclear activity and unusually strong far-infrared emission. The observational data, obtained with the National Radio Astronomy Observatory's Very Large Array in New Mexico over the past 3 years, provide the first direct "look" at a starburst-the phenomenon of sudden, rapid star formation which occurs near the nucleus of a small fraction of galaxies. Nearly all the brightest of about 40 radio sources in M82' s nucleus decreased in intensity over 2.7 years up to October 1983. One source, which in February 1981 was ten times as bright as our Galaxy's most luminous supernova remnant, turned off within only a few months. Most of the other ten strongest sources are declining so rapidly that they will fade into the background within 30 years. Thus, new supernovae are expected to appear in M82' s nucleus every few years. The discovery has revealed the "engine room" of the mysterious activity in M82 and, by implication, similar active galaxies which have disturbed nuclei and which are unusually luminous in the far infrared. An estimate of the rate of energy input by the radio-visible supernovae closely matches the far-infrared luminosities which were recently measured for M82 and other similar galaxies. PMID:17809994

  11. The Contribution of TP-AGB Stars to the Mid-infrared Colors of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Chisari, Nora E.; Kelson, Daniel D.

    2012-07-01

    We study the mid-infrared color space of 30 galaxies from the Spitzer Infrared Nearby Galaxies Survey (SINGS) survey for which Sloan Digital Sky Survey data are also available. We construct two-color maps for each galaxy and compare them to results obtained from combining Maraston evolutionary synthesis models, galactic thermally pulsating asymptotic giant branch (TP-AGB) colors, and smooth star formation histories. For most of the SINGS sample, the spatially extended mid-IR emission seen by Spitzer in normal galaxies is consistent with our simple model in which circumstellar dust from TP-AGB stars dominates at 8 and 24 μm. There is a handful of exceptions that we identify as galaxies that have high star formation rates presumably with star formation histories that cannot be assumed to be smooth, or anemic galaxies, which were depleted of their H I at some point during their evolution and have very low ongoing star formation rates.

  12. THE CONTRIBUTION OF TP-AGB STARS TO THE MID-INFRARED COLORS OF NEARBY GALAXIES

    SciTech Connect

    Chisari, Nora E.; Kelson, Daniel D.

    2012-07-10

    We study the mid-infrared color space of 30 galaxies from the Spitzer Infrared Nearby Galaxies Survey (SINGS) survey for which Sloan Digital Sky Survey data are also available. We construct two-color maps for each galaxy and compare them to results obtained from combining Maraston evolutionary synthesis models, galactic thermally pulsating asymptotic giant branch (TP-AGB) colors, and smooth star formation histories. For most of the SINGS sample, the spatially extended mid-IR emission seen by Spitzer in normal galaxies is consistent with our simple model in which circumstellar dust from TP-AGB stars dominates at 8 and 24 {mu}m. There is a handful of exceptions that we identify as galaxies that have high star formation rates presumably with star formation histories that cannot be assumed to be smooth, or anemic galaxies, which were depleted of their H I at some point during their evolution and have very low ongoing star formation rates.

  13. Atomic-to-Molecular Gas Transition in Nearby Galaxies: What can we learn from the CARMA Survey Toward IR-bright Nearby Galaxies (STING)?

    NASA Astrophysics Data System (ADS)

    Xue, Rui; Wong, Tony

    2011-10-01

    We present a detailed comparison of molecular and atomic gas distributions in 18 nearby galaxies at sub-kpc or kpc scales, based on the CO J = 1 - 0 data from the CARMA Survey Toward IR-Bright Nearby Galaxies (STING) and the HI 21cm data in the NRAO Very Large Array (VLA) archive. The observation spatial coverage extends to a quarter of the optical radius for each galaxy. The average molecular and atomic gas column density sensitivities are ~8M⊙/pc2 and ~3M⊙/pc2 at the comparison resolution. A metallicity dependence of the HI saturation limit was possibly detected in the galaxy sample ( 8.1<12+Log(O/H)<9.0 ). We used the CO and HI pixel-by-pixel comparison results to test models of the atomic-to-molecular transition and CO formation at different metallicities. An acceptable agreement was found at the limited spatial resolutions and sensitivities of the observational datasets.

  14. Star-forming galaxies as the origin of diffuse high-energy backgrounds: gamma-ray and neutrino connections, and implications for starburst history

    SciTech Connect

    Tamborra, Irene; Ando, Shin'ichiro; Murase, Kohta E-mail: s.ando@uva.nl

    2014-09-01

    Star-forming galaxies have been predicted to contribute considerably to the diffuse gamma-ray background as they are guaranteed reservoirs of cosmic rays. Assuming that the hadronic interactions responsible for high-energy gamma rays also produce high-energy neutrinos and that O(100) PeV cosmic rays can be produced and confined in starburst galaxies, we here discuss the possibility that star-forming galaxies are also the main sources of the high-energy neutrinos observed by the IceCube experiment. First, we compute the diffuse gamma-ray background from star-forming galaxies, adopting the latest Herschel PEP/HerMES luminosity function and relying on the correlation between the gamma-ray and infrared luminosities reported by Fermi observations. Then we derive the expected intensity of the diffuse high-energy neutrinos from star-forming galaxies including normal and starburst galaxies. Our results indicate that starbursts, including those with active galactic nuclei and galaxy mergers, could be the main sources of the high-energy neutrinos observed by the IceCube experiment. We find that assuming a cosmic-ray spectral index of 2.1–2.2 for all starburst-like galaxies, our predictions can be consistent with both the Fermi and IceCube data, but larger indices readily fail to explain the observed diffuse neutrino flux. Taking the starburst high-energy spectral index as free parameter, and extrapolating from GeV to PeV energies, we find that the spectra harder than E{sup -2.15} are likely to be excluded by the IceCube data, which can be more constraining than the Fermi data for this population.

  15. HOST GALAXIES OF TYPE Ia SUPERNOVAE FROM THE NEARBY SUPERNOVA FACTORY

    SciTech Connect

    Childress, M.; Aldering, G.; Aragon, C.; Bailey, S.; Fakhouri, H. K.; Hsiao, E. Y.; Kim, A. G.; Loken, S.; Antilogus, P.; Bongard, S.; Canto, A.; Cellier-Holzem, F.; Guy, J.; Baltay, C.; Buton, C.; Kerschhaggl, M.; Kowalski, M.; Chotard, N.; Copin, Y.; Gangler, E. [Universite de Lyon, F-69622, Lyon; Universite de Lyon 1, Villeurbanne; CNRS and others

    2013-06-20

    We present photometric and spectroscopic observations of galaxies hosting Type Ia supernovae (SNe Ia) observed by the Nearby Supernova Factory. Combining Galaxy Evolution Explorer (GALEX) UV data with optical and near-infrared photometry, we employ stellar population synthesis techniques to measure SN Ia host galaxy stellar masses, star formation rates (SFRs), and reddening due to dust. We reinforce the key role of GALEX UV data in deriving accurate estimates of galaxy SFRs and dust extinction. Optical spectra of SN Ia host galaxies are fitted simultaneously for their stellar continua and emission lines fluxes, from which we derive high-precision redshifts, gas-phase metallicities, and H{alpha}-based SFRs. With these data we show that SN Ia host galaxies present tight agreement with the fiducial galaxy mass-metallicity relation from Sloan Digital Sky Survey (SDSS) for stellar masses log(M{sub *}/M{sub Sun }) > 8.5 where the relation is well defined. The star formation activity of SN Ia host galaxies is consistent with a sample of comparable SDSS field galaxies, though this comparison is limited by systematic uncertainties in SFR measurements. Our analysis indicates that SN Ia host galaxies are, on average, typical representatives of normal field galaxies.

  16. Host Galaxies of Type Ia Supernovae from the Nearby Supernova Factory

    NASA Astrophysics Data System (ADS)

    Childress, M.; Aldering, G.; Antilogus, P.; Aragon, C.; Bailey, S.; Baltay, C.; Bongard, S.; Buton, C.; Canto, A.; Cellier-Holzem, F.; Chotard, N.; Copin, Y.; Fakhouri, H. K.; Gangler, E.; Guy, J.; Hsiao, E. Y.; Kerschhaggl, M.; Kim, A. G.; Kowalski, M.; Loken, S.; Nugent, P.; Paech, K.; Pain, R.; Pecontal, E.; Pereira, R.; Perlmutter, S.; Rabinowitz, D.; Rigault, M.; Runge, K.; Scalzo, R.; Smadja, G.; Tao, C.; Thomas, R. C.; Weaver, B. A.; Wu, C.

    2013-06-01

    We present photometric and spectroscopic observations of galaxies hosting Type Ia supernovae (SNe Ia) observed by the Nearby Supernova Factory. Combining Galaxy Evolution Explorer (GALEX) UV data with optical and near-infrared photometry, we employ stellar population synthesis techniques to measure SN Ia host galaxy stellar masses, star formation rates (SFRs), and reddening due to dust. We reinforce the key role of GALEX UV data in deriving accurate estimates of galaxy SFRs and dust extinction. Optical spectra of SN Ia host galaxies are fitted simultaneously for their stellar continua and emission lines fluxes, from which we derive high-precision redshifts, gas-phase metallicities, and Hα-based SFRs. With these data we show that SN Ia host galaxies present tight agreement with the fiducial galaxy mass-metallicity relation from Sloan Digital Sky Survey (SDSS) for stellar masses log(M */M ⊙) > 8.5 where the relation is well defined. The star formation activity of SN Ia host galaxies is consistent with a sample of comparable SDSS field galaxies, though this comparison is limited by systematic uncertainties in SFR measurements. Our analysis indicates that SN Ia host galaxies are, on average, typical representatives of normal field galaxies.

  17. 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.

  18. Black Holes at the Centers of Nearby Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Moran, Edward

    2011-09-01

    As part of a search for intermediate-mass black holes in the local universe, we have assembled a sample of 27 AGNs in dwarf galaxies with absolute magnitudes as faint as -15.5 and stellar masses as low as 4e8 M_sun. Collectively, these are the least massive galaxies known to contain central black holes. Surprisingly, 25 of the objects are narrow-line (type 2) AGNs. As such, they are important in the context of theoretical work, which suggests that at low luminosites AGNs may lack obscuring tori and/or classical broad-line regions. X-ray data will indicate directly whether the AGNs are obscured. The data will also afford measurements of their high-energy luminosities, which will anchor their spectral energy distributions and provide constraints on their black-hole masses.

  19. INFRARED SPECTROSCOPY OF NEARBY RADIO ACTIVE ELLIPTICAL GALAXIES

    SciTech Connect

    Mould, Jeremy; Reynolds, Tristan; Readhead, Tony; Matthews, Keith; Floyd, David; Brown, Michael; Jannuzi, Buell; Atlee, David; Cotter, Garret; Ferrarese, Laura

    2012-11-15

    In preparation for a study of their circumnuclear gas we have surveyed 60% of a complete sample of elliptical galaxies within 75 Mpc that are radio sources. Some 20% of our nuclear spectra have infrared emission lines, mostly Paschen lines, Brackett {gamma}, and [Fe II]. We consider the influence of radio power and black hole mass in relation to the spectra. Access to the spectra is provided here as a community resource.

  20. STAR FORMATION AND RELAXATION IN 379 NEARBY GALAXY CLUSTERS

    SciTech Connect

    Cohen, Seth A.; Hickox, Ryan C.; Wegner, Gary A.

    2015-06-10

    We investigate the relationship between star formation (SF) and level of relaxation in a sample of 379 galaxy clusters at z < 0.2. We use data from the Sloan Digital Sky Survey to measure cluster membership and level of relaxation, and to select star-forming galaxies based on mid-infrared emission detected with the Wide-Field Infrared Survey Explorer. For galaxies with absolute magnitudes M{sub r} < −19.5, we find an inverse correlation between SF fraction and cluster relaxation: as a cluster becomes less relaxed, its SF fraction increases. Furthermore, in general, the subtracted SF fraction in all unrelaxed clusters (0.117 ± 0.003) is higher than that in all relaxed clusters (0.097 ± 0.005). We verify the validity of our SF calculation methods and membership criteria through analysis of previous work. Our results agree with previous findings that a weak correlation exists between cluster SF and dynamical state, possibly because unrelaxed clusters are less evolved relative to relaxed clusters.

  1. MAGNETIC FIELDS IN A SAMPLE OF NEARBY SPIRAL GALAXIES

    SciTech Connect

    Van Eck, C. L.; Brown, J. C.; Shukurov, A.; Fletcher, A. E-mail: jocat@ucalgary.ca E-mail: andrew.fletcher@ncl.ac.uk

    2015-01-20

    Both observations and modeling of magnetic fields in the diffuse interstellar gas of spiral galaxies are well developed, but the theory has been confronted with observations for only a handful of individual galaxies. There is now sufficient data to consider the statistical properties of galactic magnetic fields. We have collected data from the literature on the magnetic fields and interstellar media of 20 spiral galaxies, and tested for various physically motivated correlations between magnetic field and interstellar medium parameters. Clear correlations emerge between the total magnetic field strength and molecular gas density as well as the star formation rate. The magnetic pitch angle exhibits correlations with the total gas density, the star formation rate, and the strength of the axisymmetric component of the mean magnetic field. The total and mean magnetic field strengths exhibit a noticeable degree of correlation, suggesting a universal behavior of the degree of order in galactic magnetic fields. We also compare the predictions of galactic dynamo theory to observed magnetic field parameters and identify directions in which theory and observations might be usefully developed.

  2. Optical and Near Infrared studies of the photometric structure and starburst activity of Blue Compact Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Noeske, K. G.

    2003-03-01

    This thesis describes three studies of Blue Compact Dwarf Galaxies (BCDs), focussed on the structure of the stellar components, the star-forming activity, and the environment of such galaxies, as well as the physical background of their morphological variety. The analysis of deep Near Infrared (NIR) image data of a significant sample of BCDs allows to study the evolved stellar low surface brightness (LSB) components of BCDs more precisely than previous studies at visible wavelengths. Azimuthally averaged radial surface brightness profiles (SBPs) show an exponential intensity distribution of the stellar LSB components at large galactocentric radii. This result, along with the derived exponential scale lengths which are systematically smaller than those of dwarf Irregular and dwarf Elliptical galaxies, agrees with previous optical studies. Towards smaller radii, however, the NIR data reveal an inwards-flattening of the SBPs of the stellar LSB components with respect to their outer exponential slopes in more than half of the BCDs under study. Such inwards-flattening exponential SBPs are frequent in dwarf Irregulars and dwarf Ellipticals, but were hitherto largely undiscovered in the stellar hosts of BCDs. The physical origin of such SBPs in dwarf galaxies is to date not understood. Empirical approaches to their systematization and quantitative investigation are discussed, along with the various implications of the discovery of such SBPs in many BCDs for the understanding of such galaxies. Based on the derived structural information on the stellar LSB components and the starburst components, the hypothesis is raised that below a certain threshold density of the stellar LSB component, of the order of 0.4 solar masses per cubic parsec, burst-like star formation does not occur in gas-rich dwarf galaxies. On this hypothesis, the observed relations between the structure of the stellar LSB components of BCDs and their luminosity can be reproduced, as well as the systematic

  3. ON THE GeV AND TeV DETECTIONS OF THE STARBURST GALAXIES M82 AND NGC 253

    SciTech Connect

    Lacki, Brian C.; Thompson, Todd A.; Quataert, Eliot; Loeb, Abraham; Waxman, Eli

    2011-06-20

    The GeV and TeV emission from M82 and NGC 253 observed by Fermi, HESS, and VERITAS constrain the physics of cosmic rays (CRs) in these dense starbursts. We argue that the {gamma}-rays are predominantly hadronic in origin, as expected by previous studies. The measured fluxes imply that pionic losses are efficient for CR protons in both galaxies: we show that a fraction F{sub cal} {approx} 0.2-0.4 of the energy injected in high-energy primary CR protons is lost to inelastic proton-proton collisions (pion production) before escape, producing {gamma}-rays, neutrinos, and secondary electrons and positrons. We discuss the factor of {approx}2 uncertainties in this estimate, including supernova rate and leptonic contributions to the GeV-TeV emission. We argue that {gamma}-ray data on ULIRGs like Arp 220 can test whether M82 and NGC 253 are truly calorimetric, and we present upper limits on Arp 220 from the Fermi data. We show that the observed ratio of the GeV to GHz fluxes of the starbursts suggests that non-synchrotron cooling processes are important for cooling the CR electron/positron population. We briefly reconsider previous predictions in light of the {gamma}-ray detections, including the starburst contribution to the {gamma}-ray background and CR energy densities. Finally, as a guide for future studies, we list the brightest star-forming galaxies on the sky and present updated predictions for their {gamma}-ray and neutrino fluxes.

  4. The core of the nearby S0 galaxy NGC 7457 imaged with the HST planetary camera

    NASA Technical Reports Server (NTRS)

    Lauer, Tod R.; Faber, S. M.; Holtzman, Jon A.; Baum, William A.; Currie, Douglas G.; Ewald, S. P.; Groth, Edward J.; Hester, J. Jeff; Kelsall, T.

    1991-01-01

    A brief analysis is presented of images of the nearby S0 galaxy NGC 7457 obtained with the HST Planetary Camera. While the galaxy remains unresolved with the HST, the images reveal that any core most likely has r(c) less than 0.052 arcsec. The light distribution is consistent with a gamma = -1.0 power law inward to the resolution limit, with a possible stellar nucleus with luminosity of 10 million solar. This result represents the first observation outside the Local Group of a galaxy nucleus at this spatial resolution, and it suggests that such small, high surface brightness cores may be common.

  5. VizieR Online Data Catalog: Optical supernova remnants in nearby galaxies (Vucetic+, 2015)

    NASA Astrophysics Data System (ADS)

    Vucetic, M. M.; Arbutina, B.; Urosevic, D.

    2015-09-01

    To estimate the contribution from SNRs to the total Hα emission used to determine SFRs in a galaxy, we searched the literature for all galaxies that have optically identified SNRs. In total, there are 25 of them (excluding the Milky Way). In following tables we give data for 18 nearby galaxies which have been surveyed for optical supernova remnants (SNRs). In each table we give coordinates, Hα fluxes, diameters and [SII]/Hα emission line ratios for detected SNRs, found in literature. (19 data files).

  6. Molecular gas in nearby Early-Type Powerful Classical Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Leon, S.; Lim, J.; Combes, F.; Dinh-v-Trung

    We report the detection of CO(1-0) and CO(2-1) emission from the central region of nearby 3CR radio galaxies(z<0.03). Out of 21 galaxies, 8 have been detected in, at least, one of the two CO transitions. The total molecular gas content is below 109 Msun. Their individual CO emission exhibit, for 5 cases, a double-horned line profile that is characteristic of a disk with a central depression at the rising part of its rotation cu or ring distributions of the molecular gas is consistent with the ob dust disks or rings detected optically in the cores of the galaxies. their gas originates from the mergers of two gas-rich disk galaxies, explain the molecular gas in other radio galaxies, then these galaxie long time ago (few Gyr or more) but their remnant elliptical galaxies (last 107 years or less) become active radio galaxies. Instead, we cannibalism of gas-rich galaxies provide a simpler explanation for th molecular gas in the elliptical hosts of radio galaxies (Lim et al. 2 Given the transient nature of their observed disturbances, these gala active in radio soon after the accretion event when sufficient molecu in their nuclei.

  7. XMM-Newton observation of the X-ray point source population of the starburst galaxy IC 342

    NASA Astrophysics Data System (ADS)

    Kong, Albert K. H.

    2003-11-01

    We present the results of an XMM-Newton observation of the starburst galaxy IC 342. Thirty-seven X-ray point sources were detected down to a luminosity limit of ~1037 erg s-1. Most of the sources are located near the spiral arms. The X-ray point source luminosity function is consistent with a power-law shape with a slope of 0.55, typical of starburst galaxies. We also present the energy spectra of several ultraluminous X-ray sources (ULXs), including the luminous X-ray source in the galactic nucleus. Except for the nucleus and a luminous supersoft X-ray source, other ULXs can generally be fitted with a simple power-law spectral model. The nucleus is very luminous (~1040 erg s-1 in 0.2-12 keV) and requires disc blackbody and power-law components to describe the X-ray emission. The spectral fit reveals a cool accretion disc (kT= 0.11 keV) and suggests that the source harbours either an intermediate-mass black hole or a stellar-mass black hole with outflow.

  8. Water Vapor in nearby Infrared Galaxies as Probed by Herschel

    NASA Astrophysics Data System (ADS)

    Yang, Chentao; Gao, Yu; Omont, A.; Liu, Daizhong; Isaak, K. G.; Downes, D.; van der Werf, P. P.; Lu, Nanyao

    2013-07-01

    We report the first systematic study of the submillimeter water vapor rotational emission lines in infrared (IR) galaxies based on the Fourier Transform Spectrometer (FTS) data of Herschel SPIRE. Among the 176 galaxies with publicly available FTS data, 45 have at least one H2O emission line detected. The H2O line luminosities range from ~1 × 105 L ⊙ to ~5 × 107 L ⊙ while the total IR luminosities (L IR) have a similar spread (~1-300 × 1010 L ⊙). In addition, emission lines of H2O+ and H_2^{18}O are also detected. H2O is found, for most galaxies, to be the strongest molecular emitter after CO in FTS spectra. The luminosity of the five most important H2O lines is near-linearly correlated with L IR, regardless of whether or not strong active galactic nucleus signature is present. However, the luminosity of H2O(211-202) and H2O(220-211) appears to increase slightly faster than linear with L IR. Although the slope turns out to be slightly steeper when z ~ 2-4 ULIRGs are included, the correlation is still closely linear. We find that L_{H_2O}/L IR decreases with increasing f 25/f 60, but see no dependence on f 60/f 100, possibly indicating that very warm dust contributes little to the excitation of the submillimeter H2O lines. The average spectral line energy distribution (SLED) of the entire sample is consistent with individual SLEDs and the IR pumping plus collisional excitation model, showing that the strongest lines are H2O(202-111) and H2O(321-312). Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  9. The HST Snapshot Survey of Nearby Dwarf Galaxy Candidates. III. Resolved Dwarf Galaxies In and Beyond the Local Group

    NASA Astrophysics Data System (ADS)

    Grebel, E. K.; Seitzer, P.; Dolphin, A. E.; Geisler, D.; Guhathakurta, P.; Hodge, P. W.; Karachentsev, I. D.; Karachentseva, V. E.; Sarajedini, A.; Sharina, M. E.

    1999-12-01

    We present results for several nearby, resolved dwarf galaxies imaged with WFPC2 in the framework of our HST snapshot survey of nearby dwarf galaxy candidates (Seitzer et al., paper I in this series). All data presented here were analyzed with the automated photometry package HSTPHOT (Dolphin et al., paper IV in this series). Our closest target is the recently discovered Cassiopeia dwarf spheroidal (dSph) galaxy (Karachentsev & Karachentseva 1999, A&A, 341, 355), a new Local Group member and companion of M31 (Grebel & Guhathakurta 1999, ApJ, 511, 101). Our WFPC2 snapshot data reveal a pronounced red horizontal branch in Cas dSph. IC 5152 is a dwarf irregular (dIrr) just beyond the Local Group. Our data show a significant intermediate-age population with a strongly tilted asymptotic giant branch (AGB), a substantial young population, and a wide giant branch. Other nearby galaxies to be discussed include NGC 1560, ESO 471-G006, ESO 470-G018, and KK 035. Most of these galaxies are being resolved into stars for the first time. We describe their properties in detail and derive distances for all dwarfs with a well-defined tip of the red giant branch. Membership of these galaxies in nearby groups is discussed. Support for this work was provided by NASA through grant GO-08192.97A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. EKG acknowledges support by NASA through grant HF-01108.01-98A from the Space Telescope Science Institute. EKG and IDK are supported by the Henri Chrétien International Research Grant administered by the American Astronomical Society. PG is an Alfred P. Sloan Research Fellow.

  10. Population studies in groups and clusters of galaxies. III. A catalog of galaxies in five nearby groups

    SciTech Connect

    Ferguson, H.C.; Sandage, A. Mount Wilson and Las Campanas Observatories, Pasadena, CA Space Telescope Science Institute, Baltimore, MD )

    1990-07-01

    Five nearby groups of galaxies have been surveyed using large-scale plates from the 2.5 m duPont Telescope at Las Campanas Observatory. Catalogs of galaxies brighter than B(T) = 20 are presented for the Leo, Dorado, NGC 1400, NGC 5044, and Antlia groups. A total of 1044 galaxies are included, from visual inspection of 14 plates, covering 31 deg square. Galaxies have been classified in the extended Hubble system, and group memberships have been assigned based on velocity (where available) and morphology. About half the galaxies listed are likely members of one of the nearby groups. The catalogs are complete to B(T) = 18, although the completeness limits vary slightly from group to group. Based on King model fits to the surface density profiles, the core radii of the groups range from 0.3 to 1 Mpc, and central densities range from 120 to 1900 galaxies Mpc exp-3 brighter than M(BT) = -12.5. Dynamical analysis indicates that all of the groups are likely to be gravitationally bound. 64 refs.

  11. UV-selected Young Massive Star Cluster Populations in Nearby Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Smith, Linda J.

    2015-08-01

    The Legacy ExtraGalactic UV Survey (LEGUS) is an HST Treasury program aimed at the investigation of star-formation and its relationship to environment in nearby galaxies. The results of a UV-selected study of young massive star clusters in a sample of nearby galaxies (< 10 Mpc) using detections based on the WFC3/UVIS F275W filter will be presented. Previous studies have used V or I-band detections and tend to ignore clusters younger than 10 Myr old. This very young population, which represents the most recent cluster-forming event in the LEGUS galaxies will be discussed.This poster is presented on behalf of the LEGUS team (PI Daniela Calzetti).

  12. Spectroscopic observations of southern nearby galaxies. I. NGC 2442

    NASA Astrophysics Data System (ADS)

    Bajaja, E.; Agüero, E.; Paolantonio, S.

    1999-04-01

    The galaxy NGC 2442 was observed with a REOSC spectrograph, installed in the 2.15 m CASLEO telescope, in order to derive galactic parameters from the observed optical lines and to compare them with the results of radioastronomical observations made in the continuum, at 843 MHz, with the MOST and in the CO lines with the SEST telescope. Recent publications allowed us to extend the comparison to results from interferometric observations of Hα and H I 21 cm lines and of the continuum at 1415 MHz. The long slit observations were made placing the 5farcm 8 slit at six different positions on the optical image of the galaxy. The emission line intensity ratios at the nuclear region indicate that NGC 2442 is a LINER. The electron temperature and volume density are Te ~ 14 000 K and Ne ~ 530 cm(-3) , respectively. In contrast, a spectrum of a region 87arcsec to the NE shows the typical characteristics of a H Ii region. In this case Te ~ 6,500 K and Ne ~ 10 cm(-3) . Good correlations between the distributions of intensities, velocity fields and rotation curves have been found for the optical and radio lines. It is shown that the three intensity peaks along the line at PA = 40degr were not resolved by the observations at radio frequencies. The steep central rotation curve seen in CO has been confirmed and improved showing the existence of a disc or a ring, with a radius of 12.5 arcsec, rotating at 216/sin(i) km s(-1). Two velocity components in three optical spectra obtained in the nuclear region, have been related to two small Hα regions close to the nucleus and to the central ring. Asymmetries in the distributions of the emitting sources and irregularities in their velocity fields indicate the need of modelling the galaxy before any dynamical study is attempted. Based on observations made in the Complejo Astronomico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina and the National

  13. NGC 1277: A MASSIVE COMPACT RELIC GALAXY IN THE NEARBY UNIVERSE

    SciTech Connect

    Trujillo, Ignacio; Vazdekis, Alexandre; Balcells, Marc; Sánchez-Blázquez, Patricia

    2014-01-10

    As early as 10 Gyr ago, galaxies with more than 10{sup 11} M {sub ☉} of stars already existed. While most of these massive galaxies must have subsequently transformed through on-going star formation and mergers with other galaxies, a small fraction (≲0.1%) may have survived untouched until today. Searches for such relic galaxies, useful windows to explore the early universe, have been inconclusive to date: galaxies with masses and sizes like those observed at high redshift (M {sub *} ≳ 10{sup 11} M {sub ☉}; R{sub e} ≲ 1.5 kpc) have been found in the local universe, but their stars are far too young for the galaxy to be a relic galaxy. This paper explores the first case of a nearby galaxy, NGC 1277 (at a distance of 73 Mpc in the Perseus galaxy cluster), which fulfills many criteria to be considered a relic galaxy. Using deep optical spectroscopy, we derive the star formation history along the structure of the galaxy: the stellar populations are uniformly old (>10 Gyr) with no evidence for more recent star formation episodes. The metallicity of their stars is super-solar ([Fe/H] = 0.20 ± 0.04 with a smooth decline toward the outer regions) and α-enriched ([α/Fe] = 0.4 ± 0.1). This suggests a very short formation time scale for the bulk of the stars in this galaxy. This object also rotates very fast (V {sub rot} ∼ 300 km s{sup –1}) and has a large central velocity dispersion (σ > 300 km s{sup –1}). NGC 1277 allows the exploration in full detail of properties such as the structure, internal dynamics, metallicity, and initial mass function as they were at ∼10-12 Gyr ago when the first massive galaxies were built.

  14. WITNESSING THE FORMATION OF A BRIGHTEST CLUSTER GALAXY IN A NEARBY X-RAY CLUSTER

    SciTech Connect

    Rasmussen, Jesper; Mulchaey, John S.; Bai, Lei; Ponman, Trevor J.; Raychaudhury, Somak; Dariush, Ali

    2010-07-10

    The central dominant galaxies in galaxy clusters constitute the most massive and luminous galaxies in the universe. Despite this, the formation of these brightest cluster galaxies (BCGs) and the impact of this on the surrounding cluster environment remain poorly understood. Here we present multiwavelength observations of the nearby poor X-ray cluster MZ 10451, in which both processes can be studied in unprecedented detail. Chandra observations of the intracluster medium (ICM) in the cluster core, which harbors two optically bright early-type galaxies in the process of merging, show that the system has retained a cool core and a central metal excess. This suggests that any merger-induced ICM heating and mixing remain modest at this stage. Tidally stripped stars seen around either galaxy likely represent an emerging intracluster light component, and the central ICM abundance enhancement may have a prominent contribution from in situ enrichment provided by these stars. The smaller of the merging galaxies shows evidence for having retained a hot gas halo, along with tentative evidence for some obscured star formation, suggesting that not all BCG major mergers at low redshift are completely dissipationless. Both galaxies are slightly offset from the peak of the ICM emission, with all three lying on an axis that roughly coincides with the large-scale elongation of the ICM. Our data are consistent with a picture in which central BCGs are built up by mergers close to the cluster core, by galaxies infalling on radial orbits aligned with the cosmological filaments feeding the cluster.

  15. Environmental Effects on the ISM and Star Formation Properties of Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Mok, Angus; Wilson, Christine

    2015-08-01

    We present the results from a sample of HI flux-selected spiral galaxies within 25 Mpc from the JCMT Nearby Galaxies Legacy Survey (NGLS), subdivided into isolated, group, and Virgo cluster samples. The CO J=3-2 line was observed with the James Clerk Maxwell Telescope (JCMT), a tracer for the dense molecular gas linked to star formation. We combine the CO data with integrated star formation rates using H-alpha measurements and stellar masses from the S4G Survey in order to study the link between the gas and stars inside these galaxies. We find that while the mean atomic gas mass is lower for the Virgo galaxies compared to the isolated galaxies, the distributions of molecular gas masses are not significantly different between the three samples. The specific star formation rate is also lower for the Virgo sample, followed by the group and isolated galaxies. Finally, the molecular gas depletion time is longer for the Virgo galaxies compared to the group and isolated galaxies, which suggests the possible effects of environment on the galaxy's star formation properties.

  16. The distribution of nearby rich clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Postman, Marc; Huchra, John P.; Geller, Margaret J.

    1992-01-01

    Redshifts are acquired for a complete sample of 351 Abell clusters with tenth-ranked galaxy magnitudes (m10) less than or equal to 16.5, including 115 entirely new cluster redshifts. Analysis of the spatial distribution of these clusters reveals no clustering on scales larger than 75/h Mpc. The correlation length is 20.0 (+/-4.3)/h Mpc, consistent with the results from other surveys. The frequency of voids with radii of order 60/h Mpc or less is consistent with the form and amplitude of the observed two-point correlation function. There is no significant difference between the clustering properties of clusters with RC = 0 and RC not less than 1. A percolation analysis yields 23 superclusters, 17 of which are new. The superclusters are not significantly elongated in the radial direction; large-scale peculiar motions are of order 1000 km/s or less.

  17. A NuSTAR SURVEY OF NEARBY ULTRALUMINOUS INFRARED GALAXIES

    SciTech Connect

    Teng, Stacy H.; Rigby, Jane R.; Ptak, Andrew; Stern, Daniel; Alexander, D. M.; Bauer, Franz E.; Boggs, Stephen E.; Craig, William W.; Brandt, W. Niel; Luo, Bin; Christensen, Finn E.; Comastri, Andrea; Farrah, Duncan; Gandhi, Poshak; Hailey, Charles J.; Harrison, Fiona A.; Hickox, Ryan C.; Koss, Michael; and others

    2015-11-20

    We present a Nuclear Spectroscopic Telescope Array (NuSTAR), Chandra, and XMM-Newton survey of nine of the nearest ultraluminous infrared galaxies (ULIRGs). The unprecedented sensitivity of NuSTAR at energies above 10 keV enables spectral modeling with far better precision than was previously possible. Six of the nine sources observed were detected sufficiently well by NuSTAR to model in detail their broadband X-ray spectra, and recover the levels of obscuration and intrinsic X-ray luminosities. Only one source (IRAS 13120–5453) has a spectrum consistent with a Compton-thick active galactic nucleus (AGN), but we cannot rule out that a second source (Arp 220) harbors an extremely highly obscured AGN as well. Variability in column density (reduction by a factor of a few compared to older observations) is seen in IRAS 05189–2524 and Mrk 273, altering the classification of these borderline sources from Compton-thick to Compton-thin. The ULIRGs in our sample have surprisingly low observed fluxes in high-energy (>10 keV) X-rays, especially compared to their bolometric luminosities. They have lower ratios of unabsorbed 2–10 keV to bolometric luminosity, and unabsorbed 2–10 keV to mid-IR [O iv] line luminosity than do Seyfert 1 galaxies. We identify IRAS 08572+3915 as another candidate intrinsically X-ray weak source, similar to Mrk 231. We speculate that the X-ray weakness of IRAS 08572+3915 is related to its powerful outflow observed at other wavelengths.

  18. Discovery of a Galaxy Cluster with a Violently Starbursting Core at z = 2.506

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Elbaz, David; Daddi, Emanuele; Finoguenov, Alexis; Liu, Daizhong; Schreiber, Corentin; Martín, Sergio; Strazzullo, Veronica; Valentino, Francesco; van der Burg, Remco; Zanella, Anita; Ciesla, Laure; Gobat, Raphael; Le Brun, Amandine; Pannella, Maurilio; Sargent, Mark; Shu, Xinwen; Tan, Qinghua; Cappelluti, Nico; Li, Yanxia

    2016-09-01

    We report the discovery of a remarkable concentration of massive galaxies with extended X-ray emission at z spec = 2.506, which contains 11 massive (M * ≳ 1011 M ⊙) galaxies in the central 80 kpc region (11.6σ overdensity). We have spectroscopically confirmed 17 member galaxies with 11 from CO and the remaining ones from Hα. The X-ray luminosity, stellar mass content, and velocity dispersion all point to a collapsed, cluster-sized dark matter halo with mass M 200c = 1013.9±0.2 M ⊙, making it the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive galaxies classified as quiescent. The star formation rate (SFR) in the 80 kpc core reaches ∼3400 M ⊙ yr‑1 with a gas depletion time of ∼200 Myr, suggesting that we caught this cluster in rapid build-up of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst fraction (∼25%, compared to 3%–5% in the field). The presence of both a collapsed, cluster-sized halo and a predominant population of massive SFGs suggests that this structure could represent an important transition phase between protoclusters and mature clusters. It provides evidence that the main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster, providing new insights into massive cluster formation at early epochs. The large integrated stellar mass at such high redshift challenges our understanding of massive cluster formation.

  19. High-Resolution Hα Velocity Fields of Nearby Spiral Galaxies with the Southern African Large Telescope

    NASA Astrophysics Data System (ADS)

    Mitchell, Carl; Williams, Ted; Spekkens, Kristine; Lee-Waddell, Karen; Kuzio de Naray, Rachel; Sellwood, Jerry

    2016-01-01

    In an effort to test ΛCDM predictions of galaxy mass distributions, we have obtained spectrophotometric observations of several nearby spiral galaxies with the Southern African Large Telescope (SALT) Fabry-Pérot (FP) interferometer as part of the RSS Imaging spectroscopy Nearby Galaxy Survey. Utilizing the SALT FP's 8 arcmin field of view and 2 arcsec angular resolution, we have derived 2D velocity fields of the Hα emission line to high spatial resolution at large radii. We have modeled these velocity fields with the DiskFit software package and found them to be in good agreement with lower-resolution velocity fields of the HI 21 cm line for the same galaxies. Here we present our Hα kinematic map of the barred spiral galaxy NGC 578. At the distance to this galaxy (22 Mpc), our kinematic data has a spatial resolution of 185 pc and extends to galactocentric radii of 13 kpc. The high spatial resolution of this data allows us to resolve the inner rising part of the rotation curves, which is compromised by beam smearing in lower-resolution observations. We are using these Hα kinematic data, combined with HI 21 cm kinematics and broadband photometric observations, to place constraints on NGC 578's mass distribution.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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.

  1. The Influence of Galactic Outflows on the Formation of Nearby Dwarf Galaxies.

    PubMed

    Scannapieco; Ferrara; Broadhurst

    2000-06-10

    We show that the gas in growing density perturbations is vulnerable to the influence of winds outflowing from nearby collapsed galaxies that have already formed stars. This suggests that the formation of nearby galaxies with masses less, similar10(9) M( middle dot in circle) is likely to be suppressed, irrespective of the details of galaxy formation. An impinging wind may shock-heat the gas of a nearby perturbation to above the virial temperature, thereby mechanically evaporating the gas, or the baryons may be stripped from the perturbation entirely if they are accelerated to above the escape velocity. We show that baryonic stripping is the most effective of these two processes, because shock-heated clouds that are too large to be stripped are able to radiatively cool within a sound crossing time, limiting evaporation. The intergalactic medium temperatures and star formation rates required for outflows to have a significant influence on the formation of low-mass galaxies are consistent with current observations, but may soon be examined directly via associated distortions in the cosmic microwave background and with near-infrared observations from the Next Generation Space Telescope, which may detect the supernovae from early-forming stars.

  2. The nearby Galaxy structure toward the Vela Gum nebula

    NASA Astrophysics Data System (ADS)

    Giorgi, E. E.; Solivella, G. R.; Perren, G. I.; Vázquez, R. A.

    2015-10-01

    We report on UBVI photometry and spectroscopy for MK classification purposes carried out in the fields of five open clusters projected against the Vela Gum in the Third Galactic Quadrant of the Galaxy. They are Ruprecht 20, Ruprecht 47, Ruprecht 60, NGC 2660 and NGC 2910. We could improve/confirm the parameters of these objects derived before. Ruprecht 20 is not a real physical entity, in agreement with earlier suggestions. Ruprecht 47, a young cluster in the Galactic plane, at 4.4 kpc from the Sun is quite farther than in previous distance estimations and becomes, therefore, a member of the Puppis OB2 association. For the first time Ruprecht 60 was surveyed in UBVI photometry. We found it to be placed at 4.2 kpc from the Sun of about and 1 Gyr old. NGC 2660 is another old object in our survey for which distance and age are coincident with previous findings. NGC 2910 turns out to be a young cluster of Vela OB1 association at a distance of 1.4 kpc approximately and 60 Myr old. The spectroscopic parallax method has been applied to several stars located in the fields of four out of the five clusters to get their distances and reddenings. With this method we found two blue stars in the field of NGC 2910 at distances that make them likely members of Vela OB1 too. Also, projected against the fields of Ruprecht 20 and Ruprecht 47 we have detected other young stars favoring not only the existence of Puppis OB1 and OB2 but conforming a young stellar group at ∼ 1 kpc from the Sun and extending for more than 6 kpc outward the Galaxy. If this is the case, there is a thickening of the thin Galactic disk of more than 300 pc at just 2-3 kpc from the Sun. Ruprecht 60 and NGC 2660 are too old objects that have no physical relation with the associations under discussion. An astonishing result has been the detection in the background of Ruprecht 47 of a young star at the impressive distance of 9.5 kpc from the Sun that could be a member of the innermost part of the Outer Arm

  3. ULTRA-DEEP SUB-KILOPARSEC VIEW OF NEARBY MASSIVE COMPACT GALAXIES

    SciTech Connect

    Trujillo, Ignacio; Ferre-Mateu, Anna

    2012-05-20

    Using Gemini North telescope ultra-deep and high-resolution (sub-kiloparsec) K-band adaptive optics imaging of a sample of four nearby (z {approx} 0.15) massive ({approx}10{sup 11} M{sub Sun }) compact (R < 1.5 kpc) galaxies, we have explored the structural properties of these rare objects with unprecedented detail. Our surface brightness profiles expand over 12 mag in range allowing us to explore the presence of any faint extended envelope on these objects down to stellar mass densities {approx}10{sup 6} M{sub Sun} kpc{sup -2} at radial distances of {approx}15 kpc. We find no evidence for any extended faint tail altering the compactness of these galaxies. Our objects are elongated, visually resembling S0 galaxies, and have a central stellar mass density well above the stellar mass densities of objects with similar stellar mass but normal size in the present universe. If these massive compact objects will eventually transform into normal size galaxies, the processes driving this size growth will have to migrate around (2-3) Multiplication-Sign 10{sup 10} M{sub Sun} stellar mass from their inner (R < 1.7 kpc) region toward their outskirts. Nearby massive compact galaxies share with high-z compact massive galaxies not only their stellar mass, size, and velocity dispersion but also the shape of their profiles and the mean age of their stellar populations. This makes these singular galaxies unique laboratories to explore the early stages of the formation of massive galaxies.

  4. 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.

  5. Hubble Residuals of Nearby SN Ia Are Correlated with Host Galaxy Masses

    SciTech Connect

    Kelly, Patrick L.; Hicken, Malcolm; Burke, David L.; Mandel, Kaisey S.; Kirshner, Robert P.; /Harvard-Smithsonian Ctr. Astrophys.

    2010-05-03

    From Sloan Digital Sky Survey u{prime} g{prime} r{prime} i{prime} z{prime} imaging, we estimate the stellar masses of the host galaxies of 70 low redshift SN Ia (0.015 < z < 0.08) from the hosts absolute luminosities and mass-to-light ratios. These nearby SN were discovered largely by searches targeting luminous galaxies, and we find that their host galaxies are substantially more massive than the hosts of SN discovered by the flux-limited Supernova Legacy Survey. Testing four separate light curve fitters, we detect {approx}2.5{sigma} correlations of Hubble residuals with both host galaxy size and stellar mass, such that SN Ia occurring in physically larger, more massive hosts are {approx}10% brighter after light curve correction. The Hubble residual is the deviation of the inferred distance modulus to the SN, calculated from its apparent luminosity and light curve properties, away from the expected value at the SN redshift. Marginalizing over linear trends in Hubble residuals with light curve parameters shows that the correlations cannot be attributed to a light curve-dependent calibration error. Combining 180 higher-redshift ESSENCE, SNLS, and HigherZ SN with 30 nearby SN whose host masses are less than 10{sup 10.8} M{circle_dot} n a cosmology fit yields 1 + w = 0.22{sub -0.108}{sup +0.152}, while a combination where the 30 nearby SN instead have host masses greater than 10{sup 10.8} M{circle_dot} yields 1 + w = ?0.03{sub -0.143}{sup +0.217}. Progenitor metallicity, stellar population age, and dust extinction correlate with galaxy mass and may be responsible for these systematic effects. Host galaxy measurements will yield improved distances to SN Ia.

  6. HERSCHEL FAR-INFRARED AND SUBMILLIMETER PHOTOMETRY FOR THE KINGFISH SAMPLE OF NEARBY GALAXIES

    SciTech Connect

    Dale, D. A.; Aniano, G.; Draine, B. T.; Engelbracht, C. W.; Hinz, J. L.; Montiel, E. J.; Krause, O.; Groves, B. A.; Roussel, H.; Appleton, P. N.; Armus, L.; Beirao, P.; Bolatto, A. D.; Brandl, B. R.; Calzetti, D.; Crocker, A. F.; Croxall, K. V.; Galametz, M.; Gordon, K. D.; Hao, C.-N.; and others

    2012-01-20

    New far-infrared and submillimeter photometry from the Herschel Space Observatory is presented for 61 nearby galaxies from the Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel (KINGFISH) sample. The spatially integrated fluxes are largely consistent with expectations based on Spitzer far-infrared photometry and extrapolations to longer wavelengths using popular dust emission models. Dwarf irregular galaxies are notable exceptions, as already noted by other authors, as their 500 {mu}m emission shows evidence for a submillimeter excess. In addition, the fraction of dust heating attributed to intense radiation fields associated with photodissociation regions is found to be (21 {+-} 4)% larger when Herschel data are included in the analysis. Dust masses obtained from the dust emission models of Draine and Li are found to be on average nearly a factor of two higher than those based on single-temperature modified blackbodies, as single blackbody curves do not capture the full range of dust temperatures inherent to any galaxy. The discrepancy is largest for galaxies exhibiting the coolest far-infrared colors.

  7. Resolving the extended stellar haloes of nearby galaxies: the wide-field PISCeS survey

    NASA Astrophysics Data System (ADS)

    Crnojevic, Denija; Sand, David J.; Caldwell, Nelson; Guhathakurta, Puragra; McLeod, Brian A.; Seth, Anil; Simon, Joshua D.; Strader, Jay; Toloba, Elisa

    2015-08-01

    I will present results from the wide-field Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS): we investigate the resolved stellar haloes of two nearby galaxies (the spiral NGC253 and the elliptical Centaurus A, D~3.7 Mpc) out to a galactocentric radius of 150 kpc with Magellan/Megacam. The survey led to the discovery of ~20 faint satellites and stunning streams/substructures in two environments substantially different from the Local Group, i.e. the loose Sculptor group of galaxies and the Centaurus A group dominated by an elliptical. These discoveries clearly testify the past and ongoing accretion processes shaping the haloes of these nearby galaxies, and provide the first complete census of their satellite systems down to an unprecedented M_V<-8. This effectively enables the first direct comparison of external galaxies' resolved haloes to the PAndAS survey. The detailed characterization of the stellar content, shape and gradients in the extended haloes of NGC253, Centaurus A and in their satellites represent crucial constraints to theoretical models of galaxy formation and evolution.

  8. Search for Globular Clusters in the Nearby Galaxies II. NGC 3109

    NASA Astrophysics Data System (ADS)

    Blecha, A.

    The author reports on the search for globular clusters around NGC 3109, a SB(s)m nearby galaxy using observations taken with the wide field telescope at La Silla. Clusters are discriminated by using the advanced image processing software (MOAN). From 320 objects, 23 candidates are retained. Their luminosity function peaks at mv = 19.8, thus giving the distance of the parent galaxy as 2.13 Mpc. The radial distribution follows the Dp1/4 law well. The total number of clusters is estimated at 40±25 and the specific frequency Sv = 3 clusters per Mv = -15.

  9. A low-luminosity type-1 QSO sample . IV. Molecular gas contents and conditions of star formation in three nearby Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Moser, Lydia; Krips, Melanie; Busch, Gerold; Scharwächter, Julia; König, Sabine; Eckart, Andreas; Smajić, Semir; García-Marin, Macarena; Valencia-S., Mónica; Fischer, Sebastian; Dierkes, Jens

    2016-03-01

    We present a pilot study of ~3'' resolution observations of low CO transitions with the Submillimeter Array in three nearby Seyfert galaxies, which are part of the low-luminosity quasi-stellar object (LLQSOs) sample consisting of 99 nearby (z = 0.06) type-1 active galactic nuclei (AGN) taken from the Hamburg/ESO quasi-stellar object (QSO) survey. Two sources were observed in 12CO(2-1) and 13CO(2-1) and the third in 12CO(3-2) and HCO+(4-3). None of the sources is detected in continuum emission. More than 80% of the 12CO detected molecular gas is concentrated within a diameter (FWHM) < 1.8 kpc. 13CO is tentatively detected, while HCO+ emission could not be detected. All three objects show indications of a kinematically decoupled central unresolved molecular gas component. The molecular gas masses of the three galaxies are in the range Mmol = (0.7-8.7) × 109M⊙. We give lower limits for the dynamical masses of Mdyn> 1.5 × 109M⊙ and for the dust masses of Mdust> 1.6 × 106M⊙. The R21 = 12CO/13CO(2-1) line luminosity ratios show Galactic values of R21 ~ 5-7 in the outskirts and R21 ≳ 20 in the central region, similar to starbursts and (ultra)luminous infrared galaxies ((U)LIRGs; i.e. LIRGs and ULIRGs), implying higher temperatures and stronger turbulence. All three sources show indications of 12CO(2-1)/12CO(1-0) ratios of ~0.5, suggesting a cold or diffuse gas phase. Strikingly, the 12CO(3-2)/(1-0) ratio of ~1 also indicates a higher excited phase. Since these galaxies have high infrared luminosities of LIR ≥ 1011L⊙ and seem to contain a circumnuclear starburst with minimum surface densities of gas and star formation rate (SFR) around Σmol = 50-550 M⊙pc-2 and ΣSFR = 1.1-3.1 M⊙ kpc-2 yr-1, we conclude that the interstellar medium in the centers of these LIRG Seyferts is strongly affected by violent star formation and better described by the ULIRG mass conversion factor.

  10. Near-Infrared Integral Field Spectroscopy and Mid-Infrared Spectroscopy of the Starburst Galaxy M82

    NASA Astrophysics Data System (ADS)

    Förster Schreiber, N. M.; Genzel, R.; Lutz, D.; Kunze, D.; Sternberg, A.

    2001-05-01

    We present new infrared observations of the central regions of the starburst galaxy M82. The observations consist of near-infrared integral field spectroscopy in the H and K bands obtained with the MPE 3D instrument and of λ=2.4-45 μm spectroscopy from the Short Wavelength Spectrometer (SWS) onboard the Infrared Space Observatory. These measurements are used, together with data from the literature, to (1) reexamine the controversial issue of extinction, (2) determine the physical conditions of the interstellar medium (ISM) within the star-forming regions, and (3) characterize the composition of the stellar populations. Our results provide a set of constraints for detailed starburst modeling, which we present in a companion paper. We find that purely foreground extinction cannot reproduce the global relative intensities of H recombination lines from optical to radio wavelengths. A good fit is provided by a homogeneous mixture of dust and sources, and with a visual extinction of AV=52 mag. The SWS data provide evidence for deviations from commonly assumed extinction laws between 3 and 10 μm. The fine-structure lines of Ne, Ar, and S detected with SWS imply an electron density of ~300 cm-3, and abundance ratios Ne/H and Ar/H nearly solar and S/H about one-fourth solar. The excitation of the ionized gas indicates an average effective temperature for the OB stars of 37,400 K, with little spatial variation across the starburst regions. We find that a random distribution of closely packed gas clouds and ionizing clusters and an ionization parameter of ~10-2.3 represent well the star-forming regions on spatial scales ranging from a few tens to a few hundreds of parsecs. From detailed population synthesis and the mass-to-K-light ratio, we conclude that the near-infrared continuum emission across the starburst regions is dominated by red supergiants with average effective temperatures ranging from 3600 to 4500 K and roughly solar metallicity. Our data rule out significant

  11. An infrared study of starbursts in the interacting galaxy pair Arp 299 (NGC 3690+IC 694)

    SciTech Connect

    Nakagawa, Takao; Nagata, Tetsuya; Geballe, T.R.; Okuda, Haruyuki; Shibai, Hiroshi; Tokyo Univ.; Kyoto Univ.; Joint Astronomy Center, Hilo, HI; Institute of Space and Astronautical Science, Sagamihara )

    1989-05-01

    Extensive infrared observations have been obtained of the three active regions in Arp 299. Multiaperture JHK photometry reveals that the colors of the three regions are totally different from each other, and that there are very red nuclei smaller than 4 arcsec in two of them. Multiaperture spectroscopy of the Br-gamma and the shock-excited H2 lines shows that both the atomic and molecular lines are spatially extended, indicating that Arp 299 is undergoing an active episode of star formation not only in its nuclei but also well outside of them. Although there is some evidence that suggests the presence of a compact, active galactic nucleus, a simple starburst model can explain the bolometric luminosities, production rates of ionizing photons, and H24 line luminosities of each active region in Arp 299. However, each starburst cannot last longer than 10 to the 8th yr. 56 refs.

  12. SKA studies of nearby galaxies: star-formation, accretion processes and molecular gas across all environments

    NASA Astrophysics Data System (ADS)

    Beswick, R.; Brinks, E.; Perez-Torres, M.; Richards, A. M. S.; Aalto, S.; Alberdi, A.; Argo, M. K.; van Bemmel, I.; Conway, J. E.; Dickinson, C.; Fenech, D.; Gray, M. D.; Kloeckner, H. R.; Murphy, E.; Muxlow, T. W. B.; Peel, M. W.; Rushton, A.; Schinnerer, E.

    2015-04-01

    The SKA will be a transformational instrument in the study of our local Universe. In particular, by virtue of its high sensitivity (both to point sources and diffuse low surface brightness emission), angular resolution and the frequency ranges covered, the SKA will undertake a very wide range of astrophysical research in the field of nearby galaxies. By surveying vast numbers of nearby galaxies of all types with $\\mu$Jy sensitivity and sub-arcsecond angular resolutions at radio wavelengths, the SKA will provide the cornerstone of our understanding of star-formation and accretion activity in the local Universe. In this chapter we outline the key continuum and molecular line science areas where the SKA, both during phase-1 and when it becomes the full SKA, will have a significant scientific impact.

  13. Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies: III. Emission Line Diagnostics of Ensembles of H II Regions

    SciTech Connect

    Dopita, M A; Fischera, J; Sutherland, R S; Kewley, L J; Leitherer, C; Tuffs, R J; Popescu, C C; van Breugel, W; Groves, B A

    2006-05-10

    We have built, as far as possible, fully self-consistent models of H II regions around aging clusters of stars. These produce strong emission line diagnostics applicable to either individual H II regions in galaxies, or to the integrated emission line spectra of disk or starburst galaxies. The models assume that the expansion and internal pressure of individual H II regions is driven by the net input of mechanical energy from the central cluster, be it through winds or supernova events. This eliminates the ionization parameter as a free variable, replacing it with a parameter which depends on the ratio of the cluster mass to the pressure in the surrounding interstellar medium. These models explain why H II regions with low abundances have high excitation, and demonstrate that at least part of the warm ionized medium is the result of overlapping faint, old, large, and low pressure H II regions. We present a number of line ratios (at both optical and IR wavelengths) that provide reliable abundance diagnostics for either single H II regions or for integrated galaxy spectra, and others that are sensitive to the age of the cluster stars exciting individual H II regions.

  14. AKARI NEAR-INFRARED SPECTROSCOPIC OBSERVATIONS OF INTERSTELLAR ICES IN THE EDGE-ON STARBURST GALAXY NGC 253

    SciTech Connect

    Yamagishi, Mitsuyoshi; Kaneda, Hidehiro; Ishihara, Daisuke; Oyabu, Shinki; Onaka, Takashi; Shimonishi, Takashi; Suzuki, Toyoaki

    2011-04-10

    We present the spatially resolved near-infrared (2.5-5.0 {mu}m) spectra of the edge-on starburst galaxy NGC 253 obtained with the Infrared Camera on board AKARI. Near the center of the galaxy, we clearly detect the absorption features of interstellar ices (H{sub 2}O: 3.05 {mu}m, CO{sub 2}: 4.27 {mu}m, and XCN: 4.62 {mu}m) and the emission of polycyclic aromatic hydrocarbons (PAHs) at 3.29 {mu}m and the hydrogen recombination line Br{alpha} at 4.05 {mu}m. We find that the distributions of the ices differ from those of the PAH and gas. We calculate the column densities of the ices and derive the abundance ratios of N(CO{sub 2})/N(H{sub 2}O) = 0.17 {+-} 0.05. They are similar to those obtained around the massive young stellar objects in our Galaxy (0.17 {+-} 0.03), although a much stronger interstellar radiation field and higher dust temperature are expected near the center of NGC 253.

  15. A Population of Intermediate-mass Black Holes in Dwarf Starburst Galaxies Up to Redshift=1.5

    NASA Astrophysics Data System (ADS)

    Mezcua, M.; Civano, F.; Fabbiano, G.; Miyaji, T.; Marchesi, S.

    2016-01-01

    We study a sample of ∼50,000 dwarf starburst and late-type galaxies drawn from the COSMOS survey with the aim of investigating the presence of nuclear accreting black holes (BHs) as those seed BHs from which supermassive BHs could grow in the early universe. We divide the sample into five complete redshift bins up to z = 1.5 and perform an X-ray stacking analysis using the Chandra COSMOS-Legacy survey data. After removing the contribution from X-ray binaries and hot gas to the stacked X-ray emission, we still find an X-ray excess in the five redshift bins that can be explained by nuclear accreting BHs. This X-ray excess is more significant for z\\lt 0.5. At higher redshifts, these active galactic nuclei could suffer mild obscuration, as indicated by the analysis of their hardness ratios. The average nuclear X-ray luminosities in the soft band are in the range 1039–1040 erg s‑1. Assuming that the sources accrete at ≥1% the Eddington rate, their BH masses would be ≤105 {M}ȯ , thus in the intermediate-mass BH regime, but their mass would be smaller than the one predicted by the BH-stellar mass relation. If instead the sources follow the correlation between BH mass and stellar mass, they would have sub-Eddington accreting rates of ∼10‑3 and BH masses 1–9 × 105 {M}ȯ . We thus conclude that a population of intermediate-mass BHs exists in dwarf starburst galaxies, at least up to z = 1.5, though their detection beyond the local universe is challenging due to their low luminosity and mild obscuration unless deep surveys are employed.

  16. Physical properties of young stellar populations in 24 starburst galaxies observed with FUSE

    NASA Astrophysics Data System (ADS)

    Pellerin, Anne; Robert, Carmelle

    2007-10-01

    We present the main physical properties of very young stellar populations seen with the Far Ultraviolet Spectroscopic Explorer in 24 individual starbursts. These characteristics have been obtained using the evolutionary spectral synthesis technique in the far-ultraviolet range with the LAVALSB code. For each starburst, quantitative values for age, metallicity, initial mass function slope, stellar mass and internal extinction have been obtained and discussed in details. Limits of the code have been tested. One main conclusion is that most starbursts (and probably all of them) cannot be represented by any continuous star formation burst in the far ultraviolet. Also, quantitative values of various optical diagnostics related to these stellar populations have been predicted. Underlying stellar populations, dominated by B-type stars, have been detected in NGC1140, NGC4449 and possibly NGC3991. We characterized the young stellar populations of less than 5Myr in Seyfert2 nuclei. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. Far Ultraviolet Spectroscopic Explorer (FUSE) is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985. E-mail: pellerin@stsci.edu (AP); carobert@phy.ulaval.ca (CR)

  17. Radial gas motions in The H I Nearby Galaxy Survey (THINGS)

    NASA Astrophysics Data System (ADS)

    Schmidt, Tobias M.; Bigiel, Frank; Klessen, Ralf S.; de Blok, W. J. G.

    2016-04-01

    The study of 21 cm line observations of atomic hydrogen allows detailed insight into the kinematics of spiral galaxies. We use sensitive high-resolution Very Large Array data from The H I Nearby Galaxy Survey (THINGS) to search for radial gas flows primarily in the outer parts (up to 3 × r25) of 10 nearby spiral galaxies. Inflows are expected to replenish the gas reservoir and fuel star formation under the assumption that galaxies evolve approximately in steady state. We carry out a detailed investigation of existing tilted ring fitting schemes and discover systematics that can hamper their ability to detect signatures of radial flows. We develop a new Fourier decomposition scheme that fits for rotational and radial velocities and simultaneously determines position angle and inclination as a function of radius. Using synthetic velocity fields we show that our novel fitting scheme is less prone to such systematic errors and that it is well suited to detect radial inflows in discs. We apply our fitting scheme to 10 THINGS galaxies and find clear indications of, at least partly previously unidentified, radial gas flows, in particular for NGC 2403 and NGC 3198 and to a lesser degree for NGC 7331, NGC 2903 and NGC 6946. The mass flow rates are of the same order but usually larger than the star formation rates. At least for these galaxies a scenario in which continuous mass accretion feeds star formation seems plausible. The other galaxies show a more complicated picture with either no clear inflow, outward motions or complex kinematic signatures.

  18. THE SPECTRAL ENERGY DISTRIBUTION OF POST-STARBURST GALAXIES IN THE NEWFIRM MEDIUM-BAND SURVEY: A LOW CONTRIBUTION FROM TP-AGB STARS

    SciTech Connect

    Kriek, Mariska; Conroy, Charlie; Labbe, Ivo; Whitaker, Katherine E.; Van Dokkum, Pieter G.; Brammer, Gabriel B.; Muzzin, Adam; Franx, Marijn; Quadri, Ryan F.; Illingworth, Garth D.; Rudnick, Gregory

    2010-10-10

    Stellar population synthesis (SPS) models are a key ingredient of many galaxy evolution studies. Unfortunately, the models are still poorly calibrated for certain stellar evolution stages. Of particular concern is the treatment of the thermally pulsing asymptotic giant branch (TP-AGB) phase, as different implementations lead to systematic differences in derived galaxy properties. Post-starburst galaxies are a promising calibration sample, as TP-AGB stars are thought to be most prominently visible during this phase. Here, we use post-starburst galaxies in the NEWFIRM medium-band survey to assess different SPS models. The available photometry allows the selection of a homogeneous and well-defined sample of 62 post-starburst galaxies at 0.7 {approx_lt} z {approx_lt} 2.0, from which we construct a well-sampled composite spectral energy distribution (SED) over the range 1200-40000 A. The SED is well fit by the Bruzual and Charlot SPS models, while the Maraston models do not reproduce the rest-frame optical and near-infrared parts of the SED simultaneously. When the fitting is restricted to {lambda} < 6000 A, the Maraston models overpredict the near-infrared luminosity, implying that these models give too much weight to TP-AGB stars. Using the flexible SPS models by Conroy et al. and assuming solar metallicity, we find that the contribution of TP-AGB stars to the integrated SED is a factor of {approx}3 lower than predicted by the latest Padova TP-AGB models. Whether this is due to lower bolometric luminosities, shorter lifetimes, and/or heavy dust obscuration of TP-AGB stars remains to be addressed. Altogether, our data demand a low contribution from TP-AGB stars to the SED of post-starburst galaxies.

  19. Inverse Compton X-Ray Halos Around High-z Radio Galaxies: A Feedback Mechanism Powered by Far-Infrared Starbursts or the Cosmic Microwave Background?

    NASA Technical Reports Server (NTRS)

    Small, Ian; Blundell, Katherine M.; Lehmer, B. D.; Alexander, D. M.

    2012-01-01

    We report the detection of extended X-ray emission around two powerful radio galaxies at z approx. 3.6 (4C 03.24 and 4C 19.71) and use these to investigate the origin of extended, inverse Compton (IC) powered X-ray halos at high redshifts. The halos have X-ray luminosities of L(sub X) approx. 3 x 10(exp 44) erg/s and sizes of approx.60 kpc. Their morphologies are broadly similar to the approx.60 kpc long radio lobes around these galaxies suggesting they are formed from IC scattering by relativistic electrons in the radio lobes, of either cosmic microwave background (CMB) photons or far-infrared photons from the dust-obscured starbursts in these galaxies. These observations double the number of z > 3 radio galaxies with X-ray-detected IC halos. We compare the IC X-ray-to-radio luminosity ratios for the two new detections to the two previously detected z approx. 3.8 radio galaxies. Given the similar redshifts, we would expect comparable X-ray IC luminosities if millimeter photons from the CMB are the dominant seed field for the IC emission (assuming all four galaxies have similar ages and jet powers). Instead we see that the two z approx. 3.6 radio galaxies, which are 4 fainter in the far-infrared than those at z 3.8, also have approx.4x fainter X-ray IC emission. Including data for a further six z > or approx. 2 radio sources with detected IC X-ray halos from the literature, we suggest that in the more compact, majority of radio sources, those with lobe sizes < or approx.100-200 kpc, the bulk of the IC emission may be driven by scattering of locally produced far-infrared photons from luminous, dust-obscured starbursts within these galaxies, rather than millimeter photons from the CMB. The resulting X-ray emission appears sufficient to ionize the gas on approx.100-200 kpc scales around these systems and thus helps form the extended, kinematically quiescent Ly(alpha) emission line halos found around some of these systems. The starburst and active galactic nucleus

  20. AGN and Starbursts in Dusty Galaxy Mergers: Insights from the Great Observatories All-sky LIRG Survey

    NASA Astrophysics Data System (ADS)

    Mazzarella, Joseph M.

    2014-07-01

    The Great Observatories All-sky LIRG Survey (GOALS) is combining imaging and spectroscopic data from the Herschel, Spitzer, Hubble, GALEX, Chandra, and XMM-Newton space telescopes augmented with extensive ground-based observations in a multiwavelength study of approximately 180 Luminous Infrared Galaxies (LIRGs) and 20 Ultraluminous Infrared Galaxies (ULIRGs) that comprise a statistically complete subset of the 60μm-selected IRAS Revised Bright Galaxy Sample. The objects span the full range of galaxy environments (giant isolated spirals, wide and close pairs, minor and major mergers, merger remnants) and nuclear activity types (Seyfert 1, Seyfert 2, LINER, starburst/HII), with proportions that depend strongly on the total infrared luminosity. I will review the science motivations and present highlights of recent results selected from over 25 peer-reviewed journal articles published recently by the GOALS Team. Statistical investigations include detection of high-ionization Fe K emission indicative of deeply embedded AGN, comparison of UV and far-IR properties, investigations of the fraction of extended emission as a function of wavelength derived from mid-IR spectroscopy, mid-IR spectral diagnostics and spectral energy distributions revealing the relative contributions of AGN and starbursts to powering the bolometric luminosity, and quantitative structure analyses that delineate the evolution of stellar bars and nuclear stellar cusps during the merger process. Multiwavelength dissections of individual systems have unveiled large populations of young star clusters and heavily obscured AGN in early-stage (II Zw 96), intermediate-stage (Mrk 266, Mrk 273), and late-stage (NGC 2623, IC 883) mergers. A recently published study that matches numerical simulations to the observed morphology and gas kinematics in mergers has placed four systems on a timeline spanning 175-260 million years after their first passages, and modeling of additional (U)LIRGs is underway. A very

  1. Resolving the extended stellar halos of nearby galaxies: the wide-field PISCeS survey†

    NASA Astrophysics Data System (ADS)

    Crnojević, D.; Sand, D. J.; Caldwell, N.; Guhathakurta, P.; McLeod, B.; Seth, A.; Simon, J. D.; Strader, J.; Toloba, E.

    2016-08-01

    In the wide-field Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS), we investigate the resolved stellar halos of two nearby galaxies (the elliptical Centaurus A and the spiral Sculptor, D ~ 3.7 Mpc) out to a projected galactocentric radius of 150 kpc with Magellan/Megacam. The survey has led to the discovery of ~20 faint satellites to date, plus prominent streams and substructures in two environments that are substantially different from the Local Group, i.e. the Centaurus A group dominated by an elliptical and the loose Sculptor group of galaxies. These discoveries clearly attest to the importance of past and ongoing accretion processes in shaping the halos of these nearby galaxies, and provide the first census of their satellite systems down to an unprecedented MV < -8. The detailed characterization of the stellar content, shape and gradients in the extended halos of Sculptor, Centaurus A, and their dwarf satellites provides key constraints on theoretical models of galaxy formation and evolution.

  2. Gas distribution, star formation and giant molecular cloud evolution in nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Rebolledo Lara, David Andres

    2013-12-01

    In this thesis, I present a detailed study of the resolved properties of the cold gas in nearby galaxies at different size scales, starting from the whole galactic disk to the size of the Giant Molecular Clouds (GMCs). Differences in the shape and width of global CO and HI spectra of resolved disks of spiral galaxies are systematically investigated using a nearby sample for which high-resolution CO and HI maps are available. I find that CO line widths can be wider than HI widths in galaxies where the rotation curve declines in the outer parts, while they can be narrower in galaxies where the CO does not adequately sample the flat part of the rotation curve. Limited coverage of the CO emission by the telescope beam can mimic the latter effect. A physically based prescription linking the CO and HI radial profiles with the stellar disk is consistent with these findings. Then, I present an analysis performed on high spatial resolution observations of Giant Molecular Clouds in the three nearby spiral galaxies NGC 6946, NGC 628 and M101 obtained with the Combined Array for Research in Millimeter-wave Astronomy (CARMA). Using the automated CPROPS algorithm I identified 112 CO cloud complexes in the CO(1 → 0) map and 145 GMCs in the CO(2 → 1) maps. The properties of the GMCs are similar to values found in other extragalactic studies. Clouds located on-arm present in general higher star formation rates than clouds located in inter-arm regions. Also, I find differences in the distribution of star formation efficiencies in the disk of these galaxies. These differences may be related to the underlying dynamical process that drives the observed spiral arm structure in the disks. In this scenario, in galaxies with nearly symmetric arm shape (e. g., NGC 628), the spiral shocks are triggering star formation along the arms. On other hand, galaxies with flocculent or multi-arm spiral structure (e. g., NGC 6946 and M101) show regions of high star formation efficiency at specific

  3. The variation in molecular gas depletion time among nearby galaxies: what are the main parameter dependences?

    NASA Astrophysics Data System (ADS)

    Huang, Mei-Ling; Kauffmann, Guinevere

    2014-09-01

    We re-analyse correlations between global molecular gas depletion time (tdep) and galaxy parameters for nearby galaxies from the COLD GASS survey. We improve on previous work of Saintonge et al. by estimating star formation rates using the combination of Galaxy Evolution Explorer far-ultraviolet and Wide-field Infrared Survey Explorer 22 μm data and by deriving tdep within a fixed aperture set by the beam size of gas observation. In our new study, we find correlations with much smaller scatter. Dependences of the depletion time on galaxy structural parameters such as stellar surface density and concentration index are now weak or absent. We demonstrate that the primary global parameter correlation is between tdep and specific star formation rate (sSFR); all other remaining correlations can be shown to be induced by this primary dependence. This implies that galaxies with high current-to-past-averaged star formation activity, will drain their molecular gas reservoir sooner. We then analyse tdep on 1 kpc scales in galactic discs using data from the HERA CO-Line Extragalactic Survey survey. There is remarkably good agreement between the global tdep-sSFR relation for the COLD GASS galaxies and that derived for 1 kpc scale grids in discs. This leads to the conclusion that the local molecular gas depletion time in galactic discs is dependent on the local fraction of young-to-old stars.

  4. Gradients of stellar population properties and evolution clues in a nearby galaxy M101

    SciTech Connect

    Lin, Lin; Kong, Xu; Lin, Xuanbin; Mao, Yewei; Cheng, Fuzhen; Zou, Hu; Jiang, Zhaoji; Zhou, Xu E-mail: xkong@ustc.edu.cn

    2013-06-01

    Multiband photometric images from ultraviolet and optical to infrared are collected to derive spatially resolved properties of the nearby Scd-type galaxy M101. With evolutionary stellar population synthesis models, two-dimensional distributions and radial profiles of age, metallicity, dust attenuation, and star formation timescale in the form of the Sandage star formation history are obtained. When fitting with the models, we use the IRX-A {sub FUV} relation, found to depend on a second parameter of birth rate b (ratio of present- and past-averaged star formation rates), to constrain the dust attenuation. There are obvious parameter gradients in the disk of M101, which supports the theory of an 'inside-out' disk growth scenario. Two distinct disk regions with different gradients of age and color are discovered, similar to another late-type galaxy, NGC 628. The metallicity gradient of the stellar content is flatter than that of H II regions. The stellar disk is optically thicker inside than outside and the global dust attenuation of this galaxy is lower compared with galaxies of similar and earlier morphological type. We note that a variational star formation timescale describes the real star formation history of a galaxy. The timescale increases steadily from the center to the outskirt. We also confirm that the bulge in this galaxy is a disk-like pseudobulge, whose evolution is likely to be induced by some secular processes of the small bar which is relatively young, metal-rich, and contains much dust.

  5. The interstellar medium and star formation in nearby galaxies. Ludwig Biermann Award Lecture 2013

    NASA Astrophysics Data System (ADS)

    Bigiel, F.; Cormier, D.; Schmidt, T.

    In this overview article we present some of the key projects we pursue in our Emmy Noether group. Our work is focused on nearby galaxies, where we use multi-wavelength, state-of-the-art survey data to probe distribution, abundance and properties of gas and dust in the interstellar medium (ISM) on [Si II] kpc scales. We study the average, radial distributions of atomic (H I) and molecular hydrogen (H2) across the disks of spiral galaxies and assess local (on 1 kpc scales) correlations between H I, H2 and star formation rate (SFR) surface densities across the inner, optical disks of our sample of [Si II] 30 spiral galaxies. The short H2 depletion times ([Si II] 2 Gyr) we find raises the question of if and how star formation is refueled in galactic disks. We look for such signatures of radial gas flows in our H I data and find compelling evidence at least in one case. We extend and compare our gas-SFR studies to the outer disks of galaxies, where conditions change significantly in the ISM, e.g., low metallicity and dust abundance. We focus on star formation at low-metallicity further with detailed ISM studies in dwarf galaxies, where we combine spectroscopic observations in the infrared with detailed modelling to learn about composition and detailed physical properties of the ISM. Of particular interest is the question of what drives large scale star formation in galaxies at low metallicity.

  6. Exploring the stellar populations of nearby and high redshift galaxies with ELTs

    NASA Astrophysics Data System (ADS)

    Gullieuszik, M.; Falomo, R.; Greggio, L.; Uslenghi, M.; Fantinel, D.

    The high sensitivity and spatial resolution of future ELTs facilities will offer the unique opportunity to probe directly the stellar populations of the very inner regions of galaxies in the local Universe and to derive morphological and photometric information for high redshift galaxies. We present our project aimed at assessing the expected capabilities of ELTs in the study of nearby and high-redshift stellar populations. To this end, we simulated imaging observations of different stellar populations in the local Universe and in high-redhshift galaxies with the MICADO camera at the E-ELT. Detailed photometric analyses of these images were used to probe the feasibility of science cases dealing with photometry of resolved stars in crowded fields, and with surface photometry of distant galaxies. We find that the future facilities will allow us to greatly improve our knowledge of the stellar populations in galaxies, especially in the innermost and most crowded regions. Accurate photometry of turn-off stars in nuclear star clusters of intermediate age will be possible up to distances of ˜ 3 Mpc. The exquisite spacial resolution will also drive great progress in unresolved stellar populations studies, enabling the detailed measurement of structural parameters, colour profiles, and the detection of signature of star formation sub-structures in galaxies at redshifts up to z=3.

  7. THE ORIGIN OF [O II] IN POST-STARBURST AND RED-SEQUENCE GALAXIES IN HIGH-REDSHIFT CLUSTERS

    SciTech Connect

    Lemaux, B. C.; Lubin, L. M.; Kocevski, D.; Shapley, A.; Gal, R. R.; Squires, G. K.

    2010-06-20

    of such galaxies that are classified as LINER/Seyfert, we estimate that at least {approx}20% of galaxies in high-redshift clusters with M{sub *}>10{sup 10}-10{sup 10.5} M{sub sun} contain a LINER/Seyfert component that can be revealed with line ratios. We also investigate the effect such a population has on the global star formation rate of cluster galaxies and the post-starburst fraction, concluding that LINER/Seyferts must be accounted for if these quantities are to be physically meaningful.

  8. The VIRUS-P Exploration of Nearby Galaxies (VENGA): Survey Design and First Results

    NASA Astrophysics Data System (ADS)

    Blanc, G. A.; Gebhardt, K.; Heiderman, A.; Evans, N. J., II; Jogee, S.; van den Bosch, R.; Marinova, I.; Weinzirl, T.; Yoachim, P.; Drory, N.; Fabricius, M.; Fisher, D.; Hao, L.; MacQueen, P. J.; Shen, J.; Hill, G. J.; Kormendy, J.

    2010-10-01

    VENGA is a large-scale extragalactic IFU survey, which maps the bulges, bars and large parts of the outer disks of 32 nearby normal spiral galaxies. The targets are chosen to span a wide range in Hubble types, star formation activities, morphologies, and inclinations, at the same time of having vast available multi-wavelength coverage from the far-UV to the mid-IR, and available CO and 21cm mapping. The VENGA dataset will provide 2D maps of the SFR, stellar and gas kinematics, chemical abundances, ISM density and ionization states, dust extinction and stellar populations for these 32 galaxies. The uniqueness of the VIRUS-P large field of view permits these large-scale mappings to be performed. VENGA will allow us to correlate all these important quantities throughout the different environments present in galactic disks, allowing the conduction of a large number of studies in star formation, structure assembly, galactic feedback and ISM in galaxies.

  9. Long Term Temporal and Spectral Evolution of Point Sources in Nearby Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Durmus, D.; Guver, T.; Hudaverdi, M.; Sert, H.; Balman, Solen

    2016-06-01

    We present the results of an archival study of all the point sources detected in the lines of sight of the elliptical galaxies NGC 4472, NGC 4552, NGC 4649, M32, Maffei 1, NGC 3379, IC 1101, M87, NGC 4477, NGC 4621, and NGC 5128, with both the Chandra and XMM-Newton observatories. Specifically, we studied the temporal and spectral evolution of these point sources over the course of the observations of the galaxies, mostly covering the 2000 - 2015 period. In this poster we present the first results of this study, which allows us to further constrain the X-ray source population in nearby elliptical galaxies and also better understand the nature of individual point sources.

  10. Chandra view on stellar evolution and feedback in a nearby galaxy

    NASA Astrophysics Data System (ADS)

    Oskinova, Lidia

    2014-11-01

    Chandra observations elucidate the life cycle of stars and nebulae in galaxies. The Wing of the nearby SMC galaxy has very low content of metals and is an ideal laboratory to investigate an environment that closely resembles the early Universe. Our ``large program'' observations of star forming regions at the edge of a huge shell in the SMC Wing answered important questions about the birth, life, and death of stars. For the first time we found an accreting X-ray pulsar that is still cradled in a supernova remnant. Despite its youth the pulsar spins very slowly questioning the established theories. Using Chandra we now able to observe how stellar activity changes during stellar evolution and how stellar feedback shapes the surrounding medium in our and other galaxies.

  11. X-ray Properties of the Central kpc of AGN and Starbursts: The Latest News from Chandra

    NASA Technical Reports Server (NTRS)

    Weaver, Kimberly A.; White, Nicholas E. (Technical Monitor)

    2001-01-01

    The X-ray properties of 15 nearby (v less than 3,000 km/s) galaxies that possess AGN (active galactic nuclei) and/or starbursts are discussed. Two-thirds have nuclear extended emission on scales from approx. 0.5 to approx. 1.5 kpc that is either clearly associated with a nuclear outflow or morphologically resembles an outflow. Galaxies that are AGN-dominated tend to have linear structures while starburst-dominated galaxies tend to have plume-like structures. Significant X-ray absorption is present in the starburst regions, indicating that a circumnuclear starburst is sufficient to block an AGN at optical wavelengths. Galaxies with starburst activity possess more X-ray point sources within their central kpc than non-starbursts. Many of these sources are more luminous than typical X-ray binaries. The Chandra results are discussed in terms of the starburst-AGN connection, a revised unified model for AGN, and possible evolutionary scenarios.

  12. THE ROLE OF THE MAGNETIC FIELD IN THE INTERSTELLAR MEDIUM OF THE POST-STARBURST DWARF IRREGULAR GALAXY NGC 1569

    SciTech Connect

    Kepley, Amanda A.; Everett, John; Zweibel, Ellen G.; Wilcots, Eric M.; Muehle, Stefanie; Klein, Uli E-mail: everett@physics.wisc.ed E-mail: ewilcots@astro.wisc.ed E-mail: uklein@astro.uni-bonn.d

    2010-03-20

    NGC 1569 is a nearby dwarf irregular galaxy which underwent an intense burst of star formation 10-40 Myr ago. We present observations that reach surface brightnesses 2-80 times fainter than previous radio continuum observations and the first radio continuum polarization observations of this galaxy at 20 cm, 13 cm, 6 cm, and 3 cm. These observations allow us to probe the relationship of the magnetic field of NGC 1569 to the rest of its interstellar medium (ISM). We confirm the presence of an extended radio continuum halo at 20 cm and see for the first time the radio continuum feature associated with the western Halpha arm at wavelengths shorter than 20 cm. Although, in general, the spectral indices derived for this galaxy steepen as one moves into the halo of the galaxy, there are filamentary regions of flat spectral indices extending to the edge of the galaxy. The spectral index trends in this galaxy support the theory that there is a convective wind at work in this galaxy. There is strong polarized emission at 3 cm and 6 cm and weak polarized emission at 20 cm and 13 cm. We estimate that the thermal fraction is 40%-50% in the center of the galaxy and falls off rapidly with height above the disk. Using this estimate, we derive a total magnetic field strength of 38 {mu}G in the central regions and 10-15 {mu}G in the halo. The magnetic field is largely random in the center of the galaxy; the uniform field is {approx}3-9 {mu}G and is strongest in the halo. Using our total magnetic field strength estimates and the results of previous observations of NGC 1569, we find that the magnetic pressure is the same order of magnitude but, in general, a factor of a few less than the other components of the ISM in this galaxy. The uniform magnetic field in NGC 1569 is closely associated with the Halpha bubbles and filaments. We suggest that a supernova-driven dynamo may be operating in this galaxy. Based on our pressure estimates and the morphology of the magnetic field, the

  13. Extragalactic distance scale derived from ''sosie'' galaxies. I. Distances of 167 galaxies which are sosies of 14 nearby galaxies

    SciTech Connect

    Bottinelli; Gouguenheim, L.; Paturel, G.; de Vaucouleurs, G.

    1985-11-01

    The method of ''sosie'' galaxies is applied to a large sample of galaxies extracted from the BGP catalog of H I line data and the Second Reference Catalogue of Bright Galaxies. The ''sosies'' of 14 calibrating galaxies (primary calibrators and galaxies in the nearest groups) are defined as those having the same parameters, either (1) morphological type T, axis ratio R, and maximum rotation velocity V/sub M/ or (2) T, R, and luminosity index ..lambda../sub c/.

  14. A universal, turbulence-regulated star formation law: from Milky Way clouds to high-redshift disk and starburst galaxies

    NASA Astrophysics Data System (ADS)

    Federrath, Christoph; Salim, Diane; Kewley, Lisa

    2015-08-01

    Whilst the star formation rate (SFR) of molecular clouds and galaxies is key in understanding galaxy evolution, the physical processes which determine the SFR remain unclear. This uncertainty about the underlying physics has resulted in various different star formation laws, all having substantial intrinsic scatter. Extending upon previous works that define the column density of star formation (ΣSFR) by the gas column density (Σgas), we develop a new universal star formation (SF) law based on the multi-freefall prescription of gas. This new SF law relies predominantly on the probability density function (PDF) and on the sonic Mach number of the turbulence in the star-forming clouds. By doing so we derive a relation where the star formation rate (SFR) correlates with the molecular gas mass per multi-freefall time, whereas previous models had used the average, single-freefall time. We define a new quantity called maximum (multi-freefall) gas consumption rate (MGCR) and show that the actual SFR is only about 0.4% of this maximum possible SFR, confirming the observed low efficiency of star formation. We show that placing observations in this new framework (ΣSFR vs. MGCR) yields a significantly improved correlation with 3-4 times reduced scatter compared to previous SF laws and a goodness-of-fit parameter R2 = 0.97. By inverting our new relationship, we provide sonic Mach number predictions for kpc-scale observations of Local Group galaxies as well as unresolved observations of local and high-redshift disk and starburst galaxies that do not have independent, reliable estimates for the turbulent cloud Mach number.

  15. A universal, turbulence-regulated star formation law: from Milky Way clouds to high-redshift disk and starburst galaxies

    NASA Astrophysics Data System (ADS)

    Malinda Salim, Diane; Federrath, Christoph; Kewley, Lisa

    2015-08-01

    Whilst the star formation rate (SFR) of molecular clouds and galaxies is key in understanding galaxy evolution, the physical processes that determine the SFR remain unclear, with significant intrinsic scatter arising from previous approaches at describing its functional dependencies. In lieu of this, we extend upon preceding parameterisations which had defined the column density of star formation, ΣSFR by either the gas column density Σgas or the ratio between Σgas and the average, single-freefall time. We develop a new universal star formation (SF) law that relies predominantly on the probability density function (PDF) and the sonic Mach number of the turbulence in star-forming clouds. By doing so we derive a relation where the SFR correlates with the molecular gas mass per multi-freefall time. We define a new quantity called maximum (multi-freefall) gas consumption rate (MGCR) and show that the actual SFR is only about 0.4% of the MGCR, confirming the observed low efficiency of star formation. We show that placing observations in this new framework (ΣSFR vs. MGCR) yields a significantly improved correlation with 3-4 times reduced scatter compared to previous SF laws and a goodness-of-fit parameter R2=0.97, close to a perfect fit of R2=1. By inverting our new relationship, we provide sonic Mach number predictions for kpc-scale observations of Local Group galaxies as well as unresolved observations of local and high-redshift disk and starburst galaxies that do not have independent, reliable estimates for the turbulent cloud Mach number.

  16. A Universal, Turbulence-regulated Star Formation Law: From Milky Way Clouds to High-redshift Disk and Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Salim, Diane M.; Federrath, Christoph; Kewley, Lisa J.

    2015-06-01

    While the star formation rate (SFR) of molecular clouds and galaxies is key in understanding galaxy evolution, the physical processes that determine the SFR remain unclear. This uncertainty about the underlying physics has resulted in various different star formation (SF) laws, all having substantial intrinsic scatter. Extending upon previous works that define the column density of star formation ({{{Σ }}}{SFR}) by the gas column density ({{{Σ }}}{gas}), we develop a new universal SF law based on the multi-freefall prescription of gas. This new SF law relies predominantly on the probability density function and on the sonic Mach number of the turbulence in the star-forming clouds. By doing so we derive a relation where the SFR correlates with the molecular gas mass per multi-freefall time, whereas previous models had used the average, single-freefall time. We define a new quantity called maximum (multi-freefall) gas consumption rate (MGCR) and show that the actual SFR is only about 0.4% of this maximum possible SFR, confirming the observed low efficiency of SF. We show that placing observations in this new framework ({{{Σ }}}{SFR} versus MGCR) yields a significantly improved correlation with 3-4 times reduced scatter compared to previous SF laws and a goodness-of-fit parameter {R}2=0.97. By inverting our new relationship, we provide sonic Mach number predictions for kiloparsec-scale observations of Local Group galaxies as well as unresolved observations of local and high-redshift disk and starburst galaxies that do not have independent, reliable estimates for the turbulent cloud Mach number.

  17. Preface: The Evolving ISM in the Milky Way and Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Sheth, K.; Noriega-Crespo, A.; Ingalls, J.; Paladini, R.

    2009-01-01

    The fourth Spitzer Science Symposium "The Evolving ISM in the Milky Way and Nearby Galaxies" was held in Pasadena, CA from 2-5 December, 2007. The conference focused on synthesizing recent results for the interstellar medium (ISM) and its interplay with star formation in the Milky Way and nearby galaxies. In the Milky Way and Local Group galaxies we have an unparalleled view of the astrophysics of the interstellar medium, where one can study in detail the spatially-resolved energetics and the complex interplay of physical and chemical processes that govern the ISM. The ISM is both a fossil record of past star formation and evolutionary processes and a natal medium for future star formation.The Spitzer Space Telescope has provided a plethora of exciting results that have revolutionized our understanding of the ISM and star formation, particularly from large programs such as MIPSGAL, GLIMPSE, C2D, etc. How do these new discoveries of the local processes governing the ISM impact our understanding of nearby galaxies? How important are local processes when averaged over an entire galaxy? Legacy programs like SINGS and SAGE are two examples of rich and diverse sets of data for nearby galaxies where such questions may be examined?. ISM physics is the critical ingredient for turning gas and dust diagnostics into information about evolutionary processes such as star formation. The exceptional view of the far-infrared Milky way captured by Spitzer and the extraordinary data gathered from nearby galaxies was the main reason for organizing this conference to synthesize the most recent developments in the coupled fields of the ISM and Nearby Galaxies. Over the three days, we heard invited and contributed talks from over fifty participants. The poster session had over 100 posters and results from nearly a quarter of them were also presented in an abbreviated one to two minute format. The conference also had some firsts. We tried to be as environmentally sensitive as possible by

  18. Highlighting XMM-Newton's Role in Time Domain Studies of Neutron Star and Black Hole X-ray binaries in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Laycock, S.; Yang, J.; Cappallo, R.; Christodoulou, D.; Steiner, J.

    2016-09-01

    XMM-Newton's combination of large effective area, superior event timing, and wide field imaging have provided a powerful capability for time-domain studies of nearby X-ray binary populations. In its first 15 years XMM has accomplished groundbreaking monitoring surveys for X-ray binaries; complemented by RXTE, Chandra, and Nustar. Over the next decade XMM's capabilities will complement a new generation of missions including Astrosat, Hitomi, and NICER. This paper highlights the role of XMM-Newton in combination with other missions, in exploring the HMXB populations of the Small Magellanic Cloud and IC 10. Both are nearby dwarf starburst galaxies, yet their ages and evolutionary scenarios are very different, the consequences of which have led to contrasting X-ray binary populations. In the SMC the definitive sample of X-ray binary pulsars assembled by RXTE is revealing fundamental accretion physics when probed by XMM. Finding and characterizing IC 10's youthful X-ray binaries required the combination of XMM together with Chandra and Nustar. Key results include the revelatory finding of an X-ray irradiated wind masking the mass-function in the WR+BH binary X-1 and the measurement of the BH's spin. Such studies have wide relevance to stellar/galactic evolution, implications for black hole masses and formation channels for BH+BH binaries.

  19. The frequency and properties of young tidal dwarf galaxies in nearby gas-rich groups

    NASA Astrophysics Data System (ADS)

    Lee-Waddell, K.; Spekkens, K.; Chandra, P.; Patra, N.; Cuillandre, J.-C.; Wang, J.; Haynes, M. P.; Cannon, J.; Stierwalt, S.; Sick, J.; Giovanelli, R.

    2016-08-01

    We present high-resolution Giant Metrewave Radio Telescope (GMRT) H I observations and deep Canada-France-Hawaii Telescope (CFHT) optical imaging of two galaxy groups: NGC 4725/47 and NGC 3166/9. These data are part of a multi-wavelength unbiased survey of the gas-rich dwarf galaxy populations in three nearby interacting galaxy groups. The NGC 4725/47 group hosts two tidal knots and one dwarf irregular galaxy (dIrr). Both tidal knots are located within a prominent H I tidal tail, appear to have sufficient mass (Mgas ≈ 108 M⊙) to evolve into long-lived tidal dwarf galaxies (TDGs) and are fairly young in age. The NGC 3166/9 group contains a TDG candidate, AGC 208457, at least three dIrrs and four H I knots. Deep CFHT imaging confirms that the optical component of AGC 208457 is bluer - with a 0.28 mag g - r colour - and a few Gyr younger than its purported parent galaxies. Combining the results for these groups with those from the NGC 871/6/7 group reported earlier, we find that the H I properties, estimated stellar ages and baryonic content of the gas-rich dwarfs clearly distinguish tidal features from their classical counterparts. We optimistically identify four potentially long-lived tidal objects associated with three separate pairs of interacting galaxies, implying that TDGs are not readily produced during interaction events as suggested by some recent simulations. The tidal objects examined in this survey also appear to have a wider variety of properties than TDGs of similar mass formed in current simulations of interacting galaxies, which could be the result of pre- or post-formation environmental influences.

  20. Observations of dwarfs in nearby voids: implications for galaxy formation and evolution

    NASA Astrophysics Data System (ADS)

    Pustilnik, Simon A.

    2016-10-01

    The intermediate results of the ongoing study of deep samples of ~200 galaxies residing in nearby voids, are presented. Their properties are probed via optical spectroscopy, ugri surface photometry, and HI 21-cm line measurements, with emphasis on their evolutionary status. We derive directly the hydrogen mass M(HI), the ratio M(HI)/LB and the evolutionary parameter gas-phase O/H. Their luminosities and integrated colours are used to derive stellar mass M* and the second evolutionary parameter - gas mass-fraction f g). The colours of the outer parts, typically representative of the galaxy oldest stellar population, are used to estimate the upper limits on time since the beginning of the main SF episode. We compare properties of void galaxies with those of the similar late-type galaxies in denser environments. Most of void galaxies show smaller O/H for their luminosity, in average by ~30\\%, indicating slower evolution. Besides, the fraction of ~10\\% of the whole void sample or ~30\\% of the least luminous void LSB dwarfs show the oxygen deficiency by a factor of 2-5. The majority of this group appear very gas-rich, with f g ~(95-99)%, while their outer parts appear rather blue, indicating the time of onset of the main star-formation episode of less than 1-4 Gyr. Such unevolved LSBD galaxies appear not rare among the smallest void objects, but turned out practically missed to date due to the strong observational selection effects. Our results evidense for unusual evolutionary properties of the sizable fraction of void galaxies, and thus, pose the task of better modelling of dwarf galaxy formation and evolution in voids.

  1. Globular clusters as tracers of the halo assembly of nearby central cluster galaxies

    NASA Astrophysics Data System (ADS)

    Hilker, Michael; Richtler, Tom

    2016-08-01

    The properties of globular cluster systems (GCSs) in the core of the nearby galaxy clusters Fornax and Hydra I are presented. In the Fornax cluster we have gathered the largest radial velocity sample of a GCS system so far, which enables us to identify photometric and kinematic sub-populations around the central galaxy NGC 1399. Moreover, ages, metallicities and [α/Fe] abundances of a sub-sample of 60 bright globular clusters (GCs) with high S/N spectroscopy show a multi-modal distribution in the correlation space of these three parameters, confirming heterogeneous stellar populations in the halo of NGC 1399. In the Hydra I cluster very blue GCs were identified. They are not uniformly distributed around the central galaxies. 3-color photometry including the U-band reveals that some of them are of intermediate age. Their location coincides with a group of dwarf galaxies under disruption. This is evidence of a structurally young stellar halo ``still in formation'', which is also supported by kinematic measurements of the halo light that point to a kinematically disturbed system. The most massive GCs divide into generally more extended ultra-compact dwarf galaxies (UCDs) and genuine compact GCs. In both clusters, the spatial distribution and kinematics of UCDs are different from those of genuine GCs. Assuming that some UCDs represent nuclei of stripped galaxies, the properties of those UCDs can be used to trace the assembly of nucleated dwarf galaxies into the halos of central cluster galaxies. We show via semi-analytical approaches within a cosmological simulation that only the most massive UCDs in Fornax-like clusters can be explained by stripped nuclei, whereas the majority of lower mass UCDs belong to the star cluster family.

  2. Nearby Clumpy, Gas Rich, Star-forming Galaxies: Local Analogs of High-redshift Clumpy Galaxies

    NASA Astrophysics Data System (ADS)

    Garland, C. A.; Pisano, D. J.; Mac Low, M.-M.; Kreckel, K.; Rabidoux, K.; Guzmán, R.

    2015-07-01

    Luminous compact blue galaxies (LCBGs) have enhanced star formation rates (SFRs) and compact morphologies. We combine Sloan Digital Sky Survey data with H i data of 29 LCBGs at redshift z ∼ 0 to understand their nature. We find that local LCBGs have high atomic gas fractions (∼50%) and SFRs per stellar mass consistent with some high-redshift star-forming galaxies (SFGs). Many local LCBGs also have clumpy morphologies, with clumps distributed across their disks. Although rare, these galaxies appear to be similar to the clumpy SFGs commonly observed at z ∼ 1–3. Local LCBGs separate into three groups: (1) interacting galaxies (∼20%) (2) clumpy spirals (∼40%) and (3) non-clumpy, non-spirals with regular shapes and smaller effective radii and stellar masses (∼40%). It seems that the method of building up a high gas fraction, which then triggers star formation, is not the same for all local LCBGs. This may lead to a dichotomy in galaxy characteristics. We consider possible gas delivery scenarios and suggest that clumpy spirals, preferentially located in clusters and with companions, are smoothly accreting gas from tidally disrupted companions and/or intracluster gas enriched by stripped satellites. Conversely, as non-clumpy galaxies are preferentially located in the field and tend to be isolated, we suggest clumpy, cold streams, which destroy galaxy disks and prevent clump formation, as a likely gas delivery mechanism for these systems. Other possibilities include smooth cold streams, a series of minor mergers, or major interactions.

  3. NEARBY CLUMPY, GAS RICH, STAR-FORMING GALAXIES: LOCAL ANALOGS OF HIGH-REDSHIFT CLUMPY GALAXIES

    SciTech Connect

    Garland, C. A.; Pisano, D. J.; Rabidoux, K.; Low, M.-M. Mac; Kreckel, K.; Guzmán, R. E-mail: djpisano@mail.wvu.edu E-mail: mordecai@amnh.org E-mail: guzman@astro.ufl.edu

    2015-07-10

    Luminous compact blue galaxies (LCBGs) have enhanced star formation rates (SFRs) and compact morphologies. We combine Sloan Digital Sky Survey data with H i data of 29 LCBGs at redshift z ∼ 0 to understand their nature. We find that local LCBGs have high atomic gas fractions (∼50%) and SFRs per stellar mass consistent with some high-redshift star-forming galaxies (SFGs). Many local LCBGs also have clumpy morphologies, with clumps distributed across their disks. Although rare, these galaxies appear to be similar to the clumpy SFGs commonly observed at z ∼ 1–3. Local LCBGs separate into three groups: (1) interacting galaxies (∼20%); (2) clumpy spirals (∼40%); and (3) non-clumpy, non-spirals with regular shapes and smaller effective radii and stellar masses (∼40%). It seems that the method of building up a high gas fraction, which then triggers star formation, is not the same for all local LCBGs. This may lead to a dichotomy in galaxy characteristics. We consider possible gas delivery scenarios and suggest that clumpy spirals, preferentially located in clusters and with companions, are smoothly accreting gas from tidally disrupted companions and/or intracluster gas enriched by stripped satellites. Conversely, as non-clumpy galaxies are preferentially located in the field and tend to be isolated, we suggest clumpy, cold streams, which destroy galaxy disks and prevent clump formation, as a likely gas delivery mechanism for these systems. Other possibilities include smooth cold streams, a series of minor mergers, or major interactions.

  4. Molecular gas in low-metallicity starburst galaxies:. Scaling relations and the CO-to-H2 conversion factor

    NASA Astrophysics Data System (ADS)

    Amorín, R.; Muñoz-Tuñón, C.; Aguerri, J. A. L.; Planesas, P.

    2016-04-01

    Context. Tracing the molecular gas-phase in low-mass star-forming galaxies becomes extremely challenging due to significant UV photo-dissociation of CO molecules in their low-dust, low-metallicity ISM environments. Aims: We aim to study the molecular content and the star-formation efficiency of a representative sample of 21 blue compact dwarf galaxies (BCDs), previously characterized on the basis of their spectrophotometric properties. Methods: We present CO (1-0) and (2-1) observations conducted at the IRAM-30m telescope. These data are further supplemented with additional CO measurements and multiwavelength ancillary data from the literature. We explore correlations between the derived CO luminosities and several galaxy-averaged properties. Results: We detect CO emission in seven out of ten BCDs observed. For two galaxies these are the first CO detections reported so far. We find the molecular content traced by CO to be correlated with the stellar and Hi masses, star formation rate (SFR) tracers, the projected size of the starburst, and its gas-phase metallicity. BCDs appear to be systematically offset from the Schmidt-Kennicutt (SK) law, showing lower average gas surface densities for a given ΣSFR, and therefore showing extremely low (≲0.1 Gyr) H2 and H2 +Hi depletion timescales. The departure from the SK law is smaller when considering H2 +Hi rather than H2 only, and is larger for BCDs with lower metallicity and higher specific SFR. Thus, the molecular fraction (ΣH2/ ΣHI) and CO depletion timescale (ΣH2/ ΣSFR) of BCDs is found to be strongly correlated with metallicity. Using this, and assuming that the empirical correlation found between the specific SFR and galaxy-averaged H2 depletion timescale of more metal-rich galaxies extends to lower masses, we derive a metallicity-dependent CO-to-H2 conversion factor αCO,Z ∝ (Z/Z⊙)- y, with y = 1.5(±0.3)in qualitative agreement with previous determinations, dust-based measurements, and recent model

  5. Understanding the Physical Conditions in Local Analogs of High-Redshift Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Spiewak, Renée; Erb, Dawn; Tremonti, Christina A.; Berg, Danielle

    2016-01-01

    Observations of strong nebular emission lines in high-redshift galaxies (z~2) can be illuminated through the use of analogous local galaxies (z<0.4), for which many more emission lines can be measured. The observed offset in the "BPT" ([N II]λ6584/Hα vs. [O III]λ5007/Hβ) nebular diagnostic diagram between the locus of high redshift galaxies and that of typical local galaxies indicates a change in the physical conditions of the galaxies with redshift; the cause of this offset is unknown, but it may be associated with the ionization parameter, the hardness of the ionizing spectrum, or the N/O abundance ratio. To study the offset, we have selected a sample of local galaxies from the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey Data Release 12 (SDSS-III/BOSS DR12), which occupies the same space in the [N II]λ6584/Hα vs. [O III]λ5007/Hβ diagnostic diagram as the z~2 sample. Using a suite of >50 different emission lines, most of which are unavailable in analyses of higher redshift galaxies, and a novel method of improving the spectrophotometric calibration of BOSS data, we investigate the metallicity, ionization state, and abundance ratios of this offset sample in order to shed light on the physical conditions in galaxies in the early universe.

  6. VizieR Online Data Catalog: Ultraluminous X-ray sources in nearby galaxies (Liu+, 2005)

    NASA Astrophysics Data System (ADS)

    Liu, J.-F.; Bregman, J. N.

    2005-08-01

    X-ray observations have revealed in other galaxies a class of extranuclear X-ray point sources with X-ray luminosities of 1039-1041ergs/s, exceeding the Eddington luminosity for stellar mass X-ray binaries. These ultraluminous X-ray sources (ULXs) may be powered by intermediate-mass black holes of a few thousand MSun or stellar mass black holes with special radiation processes. In this paper, we present a survey of ULXs in 313 nearby galaxies with D25>1 within 40Mpc with 467 ROSAT High Resolution Imager (HRI) archival observations. The HRI observations are reduced with uniform procedures, refined by simulations that help define the point source detection algorithm employed in this survey. A sample of 562 extragalactic X-ray point sources with LX=1038-1043ergs/s is extracted from 173 survey galaxies, including 106 ULX candidates within the D25 isophotes of 63 galaxies and 110 ULX candidates between 1D25 and 2D25 of 64 galaxies, from which a clean sample of 109 ULXs is constructed to minimize the contamination from foreground or background objects. (3 data files).

  7. Direct imaging of haloes and truncations in face-on nearby galaxies

    NASA Astrophysics Data System (ADS)

    Knapen, J. H.; Peters, S. P. C.; van der Kruit, P. C.; Trujillo, I.; Fliri, J.; Cisternas, M.; Kelvin, L. S.

    2016-08-01

    We use ultra-deep imaging from the IAC Stripe 82 Legacy Project to study the surface photometry of 22 nearby, face-on to moderately inclined spiral galaxies. The reprocessed and co-added SDSS/Stripe 82 imaging allows us to probe down to 29-30 r'-mag/arcsec2 and thus reach into the very faint outskirts of the galaxies. We find extended stellar haloes in over half of our sample galaxies, and truncations in three of them. The presence of stellar haloes and truncations is mutually exclusive, and we argue that the presence of a stellar halo can hide a truncation. We find that the onset of the halo and the truncation scales tightly with galaxy size. We highlight the importance of a proper analysis of the extended wings of the point spread function (PSF), finding that around half the light at the faintest levels is from the inner regions of a galaxy, though not the nucleus, re-distributed to the outskirts by the PSF. We discuss implications of this effect for future deep imaging surveys, such as with the LSST.

  8. Tracing the evolution within nearby galaxy groups: a multi-wavelength approach

    NASA Astrophysics Data System (ADS)

    Bettoni, Daniela; Marino, Antonina; Rampazzo, Roberto; Plana, Henri; Rosado, Margarita; Galletta, Giuseppe; Mazzei, Paola; Bianchi, Luciana; Buson, Lucio M.; Ambrocio-Cruz, Patricia; Gabbasov, Ruslan

    2015-03-01

    Evolutionary scenarios suggest that several mechanisms (from inner secular evolution to accretion/merging) may transform galaxy members, driving groups from an active star forming phase to a more passive, typical of dense environments. We are investigating this transition in a nearby group sample, designed to cover a wide range of properties (see also Marino et al. (2010), Bettoni et al. (2011) and Marino et al. (2012)). We study two groups, USGC U268 and USGC U376 located in different regions of the Leo cloud, through a photometric and kinematic characterization of their member galaxies. We revisit the group membership, using results from recent red-shift surveys, and we investigate their substructures. U268, composed of 10 catalogued members and 11 new added members, has a small fraction (~24%) of early-type galaxies (ETGs). U376 has 16 plus 8 new added members, with ~38% of ETGs. We find the significant substructuring in both groups suggesting that they are likely accreting galaxies. U268 is located in a more loose environment than U376. For each member galaxy, broad band integrated and surface photometry have been obtained in far-UV (FUV) and near-UV (NUV) with GALEX, and in u, g, r, i, z (SDSS) bands. Hα imaging and 2D high resolution kinematical data have been obtained using PUMA Scanning Fabry-Perot interferometer at the 2.12 m telescope in San Pedro Mártir (Baja California, México). We improved the galaxy classification and we detected morphological and kinematical distortions that may be connected to either on-going and/or past interaction/accretion events or environmental induced secular evolution. U268 appears more active than U376, with a large fraction of galaxies showing interaction signatures (60% vs. 13%). The presence of bars among late-type galaxies is ~10% in U268 and 29% in U376. The cumulative distribution of (FUV - NUV) colors of galaxies in U268 is significantly different (bluer) than that of U376's galaxies. Most (80%) of the early

  9. The progenitors of local ultra-massive galaxies across cosmic time: from dusty star-bursting to quiescent stellar populations

    SciTech Connect

    Marchesini, Danilo; Marsan, Cemile Z.; Muzzin, Adam; Franx, Marijn; Stefanon, Mauro; Brammer, Gabriel G.; Vulcani, Benedetta; Fynbo, J. P. U.; Milvang-Jensen, Bo; Dunlop, James S.; Buitrago, Fernando

    2014-10-10

    Using the UltraVISTA catalogs, we investigate the evolution in the 11.4 Gyr since z = 3 of the progenitors of local ultra-massive galaxies (log (M {sub star}/M {sub ☉}) ≈ 11.8; UMGs), providing a complete and consistent picture of how the most massive galaxies at z = 0 have assembled. By selecting the progenitors with a semi-empirical approach using abundance matching, we infer a growth in stellar mass of 0.56{sub −0.25}{sup +0.35} dex, 0.45{sub −0.20}{sup +0.16} dex, and 0.27{sub −0.12}{sup +0.08} dex from z = 3, z = 2, and z = 1, respectively, to z = 0. At z < 1, the progenitors of UMGs constitute a homogeneous population of only quiescent galaxies with old stellar populations. At z > 1, the contribution from star-forming galaxies progressively increases, with the progenitors at 2 < z < 3 being dominated by massive (M {sub star} ≈ 2 × 10{sup 11} M {sub ☉}), dusty (A {sub V} ∼ 1-2.2 mag), star-forming (SFR ∼ 100-400 M {sub ☉} yr{sup –1}) galaxies with a large range in stellar ages. At z = 2.75, ∼15% of the progenitors are quiescent, with properties typical of post-starburst galaxies with little dust extinction and strong Balmer break, and showing a large scatter in color. Our findings indicate that at least half of the stellar content of local UMGs was assembled at z > 1, whereas the remaining was assembled via merging from z ∼ 1 to the present. Most of the quenching of the star-forming progenitors happened between z = 2.75 and z = 1.25, in good agreement with the typical formation redshift and scatter in age of z = 0 UMGs as derived from their fossil records. The progenitors of local UMGs, including the star-forming ones, never lived on the blue cloud since z = 3. We propose an alternative path for the formation of local UMGs that refines previously proposed pictures and that is fully consistent with our findings.

  10. Dissecting the origin of the submillimetre emission in nearby galaxies with Herschel and LABOCA

    NASA Astrophysics Data System (ADS)

    Galametz, M.; Albrecht, M.; Kennicutt, R.; Aniano, G.; Bertoldi, F.; Calzetti, D.; Croxall, K. V.; Dale, D.; Draine, B.; Engelbracht, C.; Gordon, K.; Hinz, J.; Hunt, L. K.; Kirkpatrick, A.; Murphy, E.; Roussel, H.; Skibba, R. A.; Walter, F.; Weiss, A.; Wilson, C. D.

    2014-04-01

    We model the infrared to submillimetre spectral energy distribution of 11 nearby galaxies of the Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel sample using Spitzer and Herschel data and compare model extrapolations at 870 μm (using different fitting techniques) with Large APEX BOlometer CAmera (LABOCA) 870 μm observations. We investigate how the differences between predictions and observations vary with model assumptions or environment. At global scales, we find that modified blackbody models using realistic cold emissivity indices (βc = 2 or 1.5) are able to reproduce the 870 μm observed emission within the uncertainties for most of the sample. Low values (βc < 1.3) would be required in NGC 0337, NGC 1512 and NGC 7793. At local scales, we observe a systematic 870 μm excess when using βc = 2.0. The βc = 1.5 or the Draine & Li (2007) models can reconcile predictions with observations in part of the discs. Some of the remaining `excesses' occur towards the centres and can be partly or fully accounted for by non-dust contributions such as CO(3-2) or, to a lesser extent, free-free or synchrotron emission. In three non-barred galaxies, the remaining excesses rather occur in the disc outskirts. This could be a sign of a flattening of the submm slope (and decrease of the effective emissivity index) with radius in these objects.

  11. VizieR Online Data Catalog: LMXBs detected in nearby galaxies (Zhang+, 2011)

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Gilfanov, M.; Voss, R.; Sivakoff, G. R.; Kraft, R. P.; Brassington, N. J.; Kundu, A.; Jordan, A.; Sarazin, C.

    2011-11-01

    Based on the archival data from the Chandra observations of nearby galaxies, we study different sub populations of low-mass X-ray binaries (LMXBs) - dynamically formed systems in globular clusters (GCs) and in the nucleus of M 31 and (presumably primordial) X-ray binaries in the fields of galaxies. Our aim is to produce accurate luminosity distributions of X-ray binaries in different environments, suitable for quantitative comparison with each other and with the output of population synthesis calculations. Our sample includes seven nearby galaxies (M 31, Maffei 1, Centaurus A, M 81, NGC 3379, NGC 4697, and NGC 4278) and the Milky Way, which together provide relatively uniform coverage down to the luminosity limit of 1035erg/s. In total we have detected 185 LMXBs associated with GCs, 35 X-ray sources in the nucleus of M 31, and 998 field sources of which ~365 are expected to be background AGN. We combine these data, taking special care to accurately account for X-ray and optical incompleteness corrections and the removal of the contamination from the cosmic X-ray background sources, to produce luminosity distributions of X-ray binaries in different environments to far greater accuracy than has been obtained previously. (2 data files).

  12. Commentary "On Two H II Regions near the nucleus of M82" by Recillas-Cruz & Peimbert (1970): The archetype Galaxy of the Starburst Phenomena

    NASA Astrophysics Data System (ADS)

    Recillas, E.; Mayya, Y. D.; Peimbert, M.

    2011-04-01

    This commentary on the paper "On Two H II Regions Near the Nucleus of M82" by E. Recillas-Cruz and M. Peimbert, 1970, BOTT, 5, 35, 247, will recall the first attempt to explain the unusual nuclear appearance of the extragalactic nuclear regions of the M82 galaxy. We present some comments as well on the many studies that since have been made on M82, the prototype of the "Starburst" phenomena.

  13. Galaxy evolution in nearby galaxy groups - III. A GALEX view of NGC 5846, the largest group in the local universe

    NASA Astrophysics Data System (ADS)

    Marino, Antonietta; Mazzei, Paola; Rampazzo, Roberto; Bianchi, Luciana

    2016-06-01

    We explore the co-evolution of galaxies in nearby groups (Vhel ≤ 3000 km s-1) with a multiwavelength approach. We analyse GALEX far-UV (FUV) and near-UV (NUV) imaging, and Sloan Digital Sky Survey u, g, r, i, z data of groups spanning a large range of dynamical phases. We characterize the photometric properties of spectroscopically confirmed galaxy members and investigate the global properties of the groups through a dynamical analysis. Here, we focus on NGC 5846, the third most massive association of early-type galaxies (ETGs) after the Virgo and Fornax clusters. The group, composed of 90 members, is dominated by ETGs (about 80 per cent), and among ETGs about 40 per cent are dwarfs. Results are compared with those obtained for three groups in the LeoII cloud, which are radically different both in member-galaxy population and dynamical properties. The FUV-NUV cumulative colour distribution and the normalized UV luminosity function (LF) significantly differ due to the different fraction of late-type galaxy population. The UV LF of NGC 5846 resembles that of the Virgo cluster, however our analysis suggests that star formation episodes are still occurring in most of the group galaxies, including ETGs. The NUV-i colour distribution, the optical-UV colour-colour diagram, and NUV-r versus Mr colour-magnitude relation suggest that the gas contribution cannot be neglected in the evolution of ETG-type group members. Our analysis highlights that NGC 5846 is still in an active phase of its evolution, notwithstanding the dominance of dwarf and bright ETGs and its virialized configuration.

  14. All the X-ray binaries in the Universe: X-ray Emission from Normal and Starburst Galaxies Near and Far

    NASA Astrophysics Data System (ADS)

    Hornschemeier, Ann; Basu-Zych, Antara; Lehmer, Bret

    2015-08-01

    There has recently been quite a bit of excitement on the role of X-ray emission from galaxies in early heating of the IGM, demonstrating that understanding of X-ray emission from normal and starburst galaxies may have significant impact on structure formation in the Universe. The X-ray output from X-ray binaries and hot gas are both important and may rival the ionizing output of AGN at z>5, particularly for Hydrogen reionization. Here we present our research on constraining the X-ray SED of galaxies across cosmic time via several complementary approaches. In the very local universe (d <~ 30 Mpc including the Local Group) we are using NuSTAR to understand the accretion states and total output of black hole and neutron star binaries using the important lever arm of 0.5-30 keV emission. At intermediate distances (10-100 Mpc), we are comparing the X-ray output of galaxies with star formation histories and population synthesis model predictions using both Chandra and XMM data. In the slightly more distant universe (z~0.1-0.2) we can find rare analogs to primordial starbursts via wide-field optical/UV surveys that may be studied with Chandra. We will finish with a discussion of starburst galaxies emitting X-rays at z>4, which thanks to the extremely deep Chandra Deep Field-South 7 Ms survey, are better constrained than ever before. We discuss survey strategy and how the various pieces of the puzzle fit together regarding the X-ray output of galaxies and their X-ray binary populations over cosmic time. We discuss implications for next-generation missions and instruments, including those with wide-field survey capabilities and high throughput, especially the Athena mission.

  15. The Arizona Radio Observatory Survey of Molecular Gas in Nearby Normal Spiral Galaxies I: The Data

    NASA Astrophysics Data System (ADS)

    Vila-Vilaro, B.; Cepa, J.; Zabludoff, A.

    2015-06-01

    Using the ARO KP 12 m telescope, we have carried out a CO(1-0) and 13CO(1-0) survey of the central regions of 113 “normal” spiral galaxies (i.e., unperturbed and with little or no nuclear activity). Our sample spans the whole range of morphological types (T = 1-7), with distances up to 75 Mpc. The detection rates for the observed objects are 99.1% for CO(1-0) and 75.2% for 13CO(1-0), respectively. For three of the targets in our sample (i.e., NGC 0891, NGC 2903, and NGC 3521), we also carry out 13CO(1-0) mapping along their major axes, which, combined with data from the literature, reveal differences in their molecular gas properties. Analysis of the beam-matched line intensity ratios of CO(1-0)/13CO(1-0) (hereafter {R}1312) indicates that for “normal” spiral galaxies the scatter in {R}1312 is of ≈x3, and has an average value (including upper limits) of 10.4 ± 0.4 (in contrast with the values of 3-5 in typical giant molecular clouds and 13 ± 6 in Starburst Galaxies). No significant correlations (at the ≥2σ level) are found between {R}1312 and the total far-infrared (FIR) luminosity, the FIR colors, and the fraction of area sampled in the disk of each galaxy. There is a tentative (1.4σ significance) correlation between {R}1312 and morphological type along the Hubble sequence. The observed scatter in {R}1312 can be explained by intrinsic variations among the CO conversion factors. The observations presented in this work, which include the most extensive 13CO(1-0) extragalactic survey published so far on “normal” spiral galaxies are ideally suited for use in recovering the “missing” flux of interferometers with elements of similar dish sizes.

  16. Identification of red supergiants in nearby galaxies with mid-IR photometry

    NASA Astrophysics Data System (ADS)

    Britavskiy, N. E.; Bonanos, A. Z.; Mehner, A.; García-Álvarez, D.; Prieto, J. L.; Morrell, N. I.

    2014-02-01

    Context. The role of episodic mass loss in massive-star evolution is one of the most important open questions of current stellar evolution theory. Episodic mass loss produces dust and therefore causes evolved massive stars to be very luminous in the mid-infrared and dim at optical wavelengths. Aims: We aim to increase the number of investigated luminous mid-IR sources to shed light on the late stages of these objects. To achieve this we employed mid-IR selection criteria to identity dusty evolved massive stars in two nearby galaxies. Methods: The method is based on mid-IR colors, using 3.6 μm and 4.5 μm photometry from archival Spitzer Space Telescope images of nearby galaxies and J-band photometry from 2MASS. We applied our criteria to two nearby star-forming dwarf irregular galaxies, Sextans A and IC 1613, selecting eight targets, which we followed-up with spectroscopy. Results: Our spectral classification and analysis yielded the discovery of two M-type supergiants in IC 1613, three K-type supergiants and one candidate F-type giant in Sextans A, and two foreground M giants. We show that the proposed criteria provide an independent way for identifying dusty evolved massive stars that can be extended to all nearby galaxies with available Spitzer/IRAC images at 3.6 μm and 4.5 μm. Based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio de El Roque de Los Muchachos of the Instituto de Astrofísica de Canarias, on the island of La Palma, and the 2.5 m du Pont telescope in operation at Las Campanas Observatory, Chile.Spectra are only 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/562/A75

  17. Hubble Space Telescope/WFPC2 and VLA Observations of the Ionized Gas in the Dwarf Starburst Galaxy NGC 4214

    NASA Astrophysics Data System (ADS)

    MacKenty, John W.; Maíz-Apellániz, Jesús; Pickens, Christopher E.; Norman, Colin A.; Walborn, Nolan R.

    2000-12-01

    We present new Hα and [O III] λ5007 narrowband images of the starbursting dwarf galaxy NGC 4214, obtained with the Wide Field and Planetary Camera (WFPC2) on board the Hubble Space Telescope (HST), together with VLA observations of the same galaxy. The HST images resolve features down to physical scales of 2-5 pc, revealing several young (<10 Myr) star-forming complexes of various ionized gas morphologies (compact knots, complete or fragmentary shells) and sizes (~10-200 pc). Our results are consistent with a uniform set of evolutionary trends: The youngest, smaller, filled regions that presumably are those just emerging from dense star-forming clouds tend to be of high excitation and are highly obscured. Evolved, larger shell-like regions have lower excitation and are less extincted owing to the action of stellar winds and supernovae. In at least one case we find evidence for induced star formation, which has led to a two-stage starburst. Age estimates based on W(Hα) measurements do not agree with those inferred from wind-driven shell models of expanding H II regions. The most likely explanation for this effect is the existence of an ~2 Myr delay in the formation of superbubbles caused by the pressure exerted by the high-density medium in which massive stars are born. We report the detection of a supernova remnant embedded in one of the two large H II complexes of NGC 4214. The dust in NGC 4214 is not located in a foreground screen but is physically associated with the warm ionized gas. Based on observations with the NASA/ESA Hubble Space Telescope and the NRAO Very Large Array. The HST observations were obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-26555. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

  18. THE ACS NEARBY GALAXY SURVEY TREASURY. III. CEPHEIDS IN THE OUTER DISK OF M81

    SciTech Connect

    McCommas, Les P.; Williams, Benjamin F.; Dalcanton, Julianne J.; Davis, Matthew R.; Yoachim, Peter; Dolphin, Andrew E. E-mail: jd@astro.washington.edu E-mail: mrdavis@astro.washington.edu E-mail: adolphin@ratheon.com

    2009-06-15

    The ACS Nearby Galaxy Survey Treasury (ANGST) has acquired deep ACS imaging of a field in the outer disk of the large spiral galaxy M81. These data were obtained over a total of 20 Hubble Space Telescope orbits, providing a baseline long enough to reliably identify Cepheid variable stars in the field. Fundamental mode and first overtone types have been distinguished through comparative fits with corresponding Cepheid light curve templates derived from principal component analysis of confirmed Cepheids in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and Milky Way. A distance modulus of 27.78 {+-} 0.05 {sub r} {+-} 0.14 {sub s} with a corresponding distance of 3.60 {+-} 0.23 Mpc has been calculated from a sample of 11 fundamental mode and two first overtone Cepheids (assuming an LMC distance modulus of {mu}{sub LMC} = 18.41 {+-} 0.10 {sub r} {+-} 0.13 {sub s})

  19. The photometric properties of brightest cluster galaxies. I - Absolute magnitudes in 116 nearby Abell clusters

    NASA Technical Reports Server (NTRS)

    Hoessel, J. G.; Gunn, J. E.; Thuan, T. X.

    1980-01-01

    Two-color aperture photometry of the brightest galaxies in a complete sample of nearby Abell clusters is presented. The results are used to anchor the bright end of the Hubble diagram; essentially the entire formal error for this method is then due to the sample of distant clusters used. New determinations of the systematic trend of galaxy absolute magnitude with the cluster properties of richness and Bautz-Morgan type are derived. When these new results are combined with the Gunn and Oke (1975) data on high-redshift clusters, a formal value (without accounting for any evolution) of q sub 0 = -0.55 + or - 0.45 (1 standard deviations) is found.

  20. The ESO nearby Abell cluster survey. VII. Galaxy density profiles of rich clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Adami, C.; Mazure, A.; Katgert, P.; Biviano, A.

    1998-08-01

    We have analyzed the projected galaxy distributions in a subset of the ENACS cluster sample, viz. in those 77 clusters that have z < 0.1 and R_ACO >= 1 and for which ENACS and COSMOS data are available. For 20 % of these, the distribution of galaxies in the COSMOS catalogue does not allow a reliable centre position to be determined. For the other 62 clusters, we first determined the centre and elongation of the galaxy distribution. Subsequently, we made Maximum-Likelihood fits to the distribution of COSMOS galaxies for 4 theoretical profiles, two with `cores' (generalized King- and Hubble-profiles) and two with `cusps' (generalized Navarro, Frenk and White, or NFW, and de Vaucouleurs profiles). We obtain average core radii (or characteristic radii for the profiles without core) of 128, 189, 292 and 1582 kpc for fits with King, Hubble, NFW and de Vaucouleurs profiles respectively, with dispersions around these average values of 88, 116, 191 and 771 kpc. The surface density of background galaxies is about 4 10(-5) gals arcsec(-2) (with a spread of about 2 10(-5) ), and there is very good agreement between the values found for the 4 profiles. There is also very good agreement on the outer logarithmic slope of the projected galaxy distribution, which is that for the non-generalized King- and Hubble-profile (i.e. beta_ {King} = beta_ {Hubble} = 1, with the corresponding values for the two other model-profiles). We use the Likelihood ratio to investigate whether the observations are significantly better described by profiles with cusps or by profiles with cores. Taking the King and NFW profiles as `model' of either class, we find that about 75 % of the clusters are better fit by the King profile than by the NFW profile. However, for the individual clusters the preference for the King profile is rarely significant at a confidence level of more than 90 %. When we limit ourselves to the central regions it appears that the signifance increases drastically, with 65 % of the

  1. Ionized gas velocity dispersion in nearby dwarf galaxies: looking at supersonic turbulent motions

    NASA Astrophysics Data System (ADS)

    Moiseev, Alexei V.; Lozinskaya, Tatiana A.

    2012-06-01

    We present the results of an ionized gas turbulent motions study in several nearby dwarf galaxies using a scanning Fabry-Perot interferometer with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). Combining the ‘intensity-velocity dispersion’ diagrams (?) with two-dimensional maps of radial velocity dispersion, we found a number of common patterns pointing to the relation between the value of chaotic ionized gas motions and processes of current star formation. In five out of the seven analysed galaxies, we identified expanding shells of ionized gas with diameters of 80-350 pc and kinematic ages of 1-4 Myr. We also demonstrate that the ? diagrams may be useful for the search of supernova remnants, other small expanding shells or unique stars in nearby galaxies. As an example, a candidate luminous blue variable (LBV) was found in UGC 8508. We propose some additions to the interpretation, previously used by Muñoz-Tuñón et al. to explain the ? diagrams for giant star formation regions. In the case of dwarf galaxies, a major part of the regions with high velocity dispersion belongs to the diffuse low surface brightness emission, surrounding the star-forming regions. We attribute this to the presence of perturbed low-density gas with high values of turbulent velocities around the giant H II regions. Based on observations obtained with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. The observations were carried out with the financial support of the Ministry of Education and Science of Russian Federation (contracts no. 16.518.11.7073 and 16.552.11.7028).

  2. Charge-exchange X-ray emission of nearby star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Liu, Jiren; Wang, Q. Daniel; Mao, Shude

    2012-03-01

    Properties of hot gas outflows from galaxies are generally measured from associated X-ray line emission assuming that it represents atomic transitions in thermally excited hot gas. X-ray line emission, however, can also arise from the charge exchange between highly ionized ions and neutral species. The Kα triplet of He-like ions can be used as a powerful diagnostic, because the charge-exchange X-ray emission (CXE) favours the intercombination and forbidden lines, while the thermal emission favours the resonance line. We analyse the O VII triplet of a sample of nine nearby star-forming galaxies observed by the XMM-Newton Reflection Grating Spectrometers. For most galaxies, the forbidden lines are comparable to or stronger than the resonance lines, which is in contrast to the thermal prediction. For NGC 253, M51, M83, M61, NGC 4631, and the Antennae (Arp 244), the observed line ratios are consistent with the ratio of CXE; for M94 and NGC 2903, the observed ratios indicate multiple origins; for M82, different regions show different line ratios, also indicating multiple origins. We discuss other possible mechanisms that can produce a relatively strong forbidden line, such as a collisional non-equilibrium-ionization recombining/ionizing plasma, which are not favoured. These results suggest that the CXE may be a common phenomenon and contribute a significant fraction of the soft X-ray line emission for galaxies with massive star formation.

  3. The abundance properties of nearby late-type galaxies. I. The data

    SciTech Connect

    Pilyugin, L. S.; Grebel, E. K.; Kniazev, A. Y. E-mail: grebel@ari.uni-heidelberg.de

    2014-06-01

    We investigate the oxygen and nitrogen abundance distributions across the optical disks of 130 nearby late-type galaxies using around 3740 published spectra of H II regions. We use these data in order to provide homogeneous abundance determinations for all objects in the sample, including H II regions in which not all of the usual diagnostic lines were measured. Examining the relation between N and O abundances in these galaxies we find that the abundances in their centers and at their isophotal R {sub 25} disk radii follow the same relation. The variation in N/H at a given O/H is around 0.3 dex. We suggest that the observed spread in N/H may be partly caused by the time delay between N and O enrichment and the different star formation histories in galaxies of different morphological types and dimensions. We study the correlations between the abundance properties (central O and N abundances, radial O and N gradients) of a galaxy and its morphological type and dimension.

  4. Probing the magnetic field of the nearby galaxy pair Arp 269

    NASA Astrophysics Data System (ADS)

    Nikiel-Wroczyński, B.; Jamrozy, M.; Soida, M.; Urbanik, M.; Knapik, J.

    2016-06-01

    We present a multiwavelength radio study of the nearby galaxy pair Arp 269 (NGC 4490/85). High sensitivity to extended structures gained by using the merged interferometric and single-dish maps allowed us to reveal a previously undiscovered extension of the radio continuum emission. Its direction is significantly different from that of the neutral gas tail, suggesting that different physical processes might be involved in their creation. The population of radio-emitting electrons is generally young, signifying an ongoing, vigorous star formation - this claim is supported by strong magnetic fields (over 20 μG), similar to the ones found in much larger spiral galaxies. From the study of the spectral energy distribution, we conclude that the electron population in the intergalactic bridge between member galaxies originates from the disc areas, and therefore its age (approximately 3.7-16.9 Myr, depending on the model used) reflects the time-scale of the interaction. We have also discovered an angularly near compact steep source - which is a member of a different galaxy pair - at a redshift of approximately 0.125.

  5. Satellite accretion in action: a tidally disrupting dwarf spheroidal around the nearby spiral galaxy NGC 253

    NASA Astrophysics Data System (ADS)

    Romanowsky, Aaron J.; Martínez-Delgado, David; Martin, Nicolas F.; Morales, Gustavo; Jennings, Zachary G.; GaBany, R. Jay; Brodie, Jean P.; Grebel, Eva K.; Schedler, Johannes; Sidonio, Michael

    2016-03-01

    We report the discovery of NGC 253-dw2, a dwarf spheroidal (dSph) galaxy candidate undergoing tidal disruption around a nearby spiral galaxy, NGC 253 in the Sculptor group: the first such event identified beyond the Local Group. The dwarf was found using small-aperture amateur telescopes, and followed up with Suprime-Cam on the 8 m Subaru Telescope in order to resolve its brightest stars. Using g- and Rc-band photometry, we detect a red giant branch consistent with an old, metal-poor stellar population at a distance of ˜3.5 Mpc. From the distribution of likely member stars, we infer a highly elongated shape with a semimajor axis half-light radius of (2 ± 0.4) kpc. Star counts also yield a luminosity estimate of ˜2 × 106 L⊙,V (MV ˜ -10.7). The morphological properties of NGC 253-dw2 mark it as distinct from normal dSphs and imply ongoing disruption at a projected distance of ˜50 kpc from the main galaxy. Our observations support the hierarchical paradigm wherein massive galaxies continuously accrete less massive ones, and provide a new case study for dSph infall and dissolution dynamics. We also note the continued efficacy of small telescopes for making big discoveries.

  6. VizieR Online Data Catalog: Spectroscopy of HII regions in nearby galaxies (Sanchez+, 2012)

    NASA Astrophysics Data System (ADS)

    Sanchez, S. F.; Rosales-Ortega, F. F.; Marino, R. A.; Iglesias-Paramo, J.; Vilchez, J. M.; Kennicutt, R. C.; Diaz, A. I.; Mast, D.; Monreal-Ibero, A.; Garcia-Benito, R.; Bland-Hawthorn, J.; Perez, E.; Gonzalez Delgado, R.; Husemann, B.; Lopez-Sanchez, A. R.; Cid Fernandes, R.; Kehrig, C.; Walcher, C. J.; Gil de Paz, A.; Ellis, S.

    2012-08-01

    In this work we analyze the spectroscopic properties of a large number of HII regions, ~2600, located in 38 galaxies. The sample of galaxies has been assembled from the face-on spirals in the PINGS survey and a sample described in Marmol-Queralto (2011A&A...534A...8M). All the galaxies were observed using Integral Field Spectroscopy with a similar setup, covering their optical extension up to ~2.4 effective radii within a wavelength range from ~3700 to ~6900Å. We develop a new automatic procedure to detect HII regions, based on the contrast of the Hα intensity maps extracted from the datacubes. Once detected, the procedure provides us with the integrated spectra of each individual segmented region. In total, we derive good quality spectroscopic information for ~2600 independent HII regions/complexes. This is by far the largest nearby 2-dimensional spectroscopic survey presented on this kind of regions up-to-date. Even more, our selection criteria and dataset guarantee that we cover the regions in an unbiased way, regarding the spatial sampling. A well-tested automatic decoupling procedure has been applied to remove the underlying stellar population, deriving the main properties (intensity, dispersion and velocity) of the strongest emission lines in the considered wavelength range (covering from [OII]3727 to [SII]6731). A final catalogue of the spectroscopic properties of these regions has been created for each galaxy. (2 data files).

  7. HOST GALAXY PROPERTIES AND HUBBLE RESIDUALS OF TYPE Ia SUPERNOVAE FROM THE NEARBY SUPERNOVA FACTORY

    SciTech Connect

    Childress, M.; Aldering, G.; Aragon, C.; Bailey, S.; Fakhouri, H. K.; Hsiao, E. Y.; Kim, A. G.; Loken, S.; Antilogus, P.; Bongard, S.; Canto, A.; Cellier-Holzem, F.; Guy, J.; Baltay, C.; Buton, C.; Kerschhaggl, M.; Kowalski, M.; Chotard, N.; Copin, Y.; Gangler, E. [Universite de Lyon, F-69622, Lyon; Universite de Lyon 1, Villeurbanne; CNRS and others

    2013-06-20

    We examine the relationship between Type Ia supernova (SN Ia) Hubble residuals and the properties of their host galaxies using a sample of 115 SNe Ia from the Nearby Supernova Factory. We use host galaxy stellar masses and specific star formation rates fitted from photometry for all hosts, as well as gas-phase metallicities for a subset of 69 star-forming (non-active galactic nucleus) hosts, to show that the SN Ia Hubble residuals correlate with each of these host properties. With these data we find new evidence for a correlation between SN Ia intrinsic color and host metallicity. When we combine our data with those of other published SN Ia surveys, we find the difference between mean SN Ia brightnesses in low- and high-mass hosts is 0.077 {+-} 0.014 mag. When viewed in narrow (0.2 dex) bins of host stellar mass, the data reveal apparent plateaus of Hubble residuals at high and low host masses with a rapid transition over a short mass range (9.8 {<=} log (M{sub *}/M{sub Sun }) {<=} 10.4). Although metallicity has been a favored interpretation for the origin of the Hubble residual trend with host mass, we illustrate how dust in star-forming galaxies and mean SN Ia progenitor age both evolve along the galaxy mass sequence, thereby presenting equally viable explanations for some or all of the observed SN Ia host bias.

  8. BaLROG: The Influence of Bars on the Dynamical Structure in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Seidel, M. K.; Falcón-Barroso, J.; Martínez-Valpuesta, I.; Díaz-García, S.; Laurikainen, E.; Salo, H.; Knapen, J. H.

    2016-10-01

    Using the BaLROG (Bars in Low Redshift Optical Galaxies) sample of 16 morphologically distinct barred spirals, we constrain the influence of bars on nearby galaxies observationally. Our sample appears small compared to ongoing IFU surveys, but offers a tenfold sharper spatial resolution (˜100 pc) as each galaxy is a mosaic of several pointings observed with the IFU spectrograph SAURON. We demonstrate a correlation between the bar strength Qb determined from classical torque analysis using 3.6 μm Spitzer (S4G) images, with Qkin, a kinematic torque, calculated via our new method based solely on the kinematics. Using a large number of N-body simulations, we verify this correlation and the measurement of Qb. We also determine bar strengths from ionized gas kinematics and find that they are ˜2.5 larger than those measured from stellar kinematics. Further, inner kinematic features related to bars as predicted by simulations seem to be stronger for stronger bars. We find a stellar angular momentum dip at 0.2±0.1 bar lengths. In these central regions, about half of our sample also exhibits an anti-correlation of h3 - stellar velocity (v/σ). An increased flattening of the stellar σ gradient with increasing bar strength supports the notion of bar-induced orbit mixing. Our results constrain the spatial scales and magnitude of a kinematic influence of bar-driven secular evolution in present day galaxies.

  9. Neutral carbon and CO in 76 (U)LIRGs and starburst galaxy centers. A method to determine molecular gas properties in luminous galaxies

    NASA Astrophysics Data System (ADS)

    Israel, F. P.; Rosenberg, M. J. F.; van der Werf, P.

    2015-06-01

    In this paper we present fluxes in the [ CI ] lines of neutral carbon at the centers of some 76 galaxies with far-infrared luminosities ranging from 109 to 1012L⊙, as obtained with the Herschel Space Observatory and ground-based facilities, along with the line fluxes of the J = 7-6, J = 4-3, J = 2-112CO, and J = 2-113CO transitions. With this dataset, we determine the behavior of the observed lines with respect to each other and then investigate whether they can be used to characterize the molecular interstellar medium (ISM) of the parent galaxies in simple ways and how the molecular gas properties define the model results. In most starburst galaxies, the [ CI ] to 13CO line flux ratio is much higher than in Galactic star-forming regions, and it is correlated to the total far-infrared luminosity. The [ CI ] (1-0)/12CO (4-3), the [ CI ] (2-1)/12CO (7-6), and the [ CI ] (2-1)/(1-0) flux ratios are correlated, and they trace the excitation of the molecular gas. In the most luminous infrared galaxies (LIRGs), the ISM is fully dominated by dense (n( H2) = 104-105 cm-3) and moderately warm (Tkin ≈ 30 K) gas clouds that appear to have low [C°]/[CO] and [13CO]/[12CO] abundances. In less luminous galaxies, emission from gas clouds at lower densities becomes progressively more important, and a multiple-phase analysis is required to determine consistent physical characteristics. Neither the 12CO nor the [ CI ] velocity-integrated line fluxes are good predictors of molecular hydrogen column densities in individual galaxies. In particular, so-called X( [ CI ]) conversion factors are not superior to X( 12CO) factors. The methods and diagnostic diagrams outlined in this paper also provide a new and relatively straightforward means of deriving the physical characteristics of molecular gas in high-redshift galaxies up to z = 5, which are otherwise hard to determine.

  10. The extragalactic distance scale derived from 'sosie' galaxies. I - Distances of 167 galaxies which are sosies of 14 nearby galaxies

    NASA Astrophysics Data System (ADS)

    Bottinelli, L.; Gouguenheim, L.; Paturel, G.; de Vaucouleurs, G.

    1985-11-01

    The method of "sosie" galaxies is applied to a large sample of galaxies extracted from the BGP catalog of H I line data and the Second Reference Catalogue of Bright Galaxies. The "sosies" of 14 calibrating galaxies (primary calibrators and galaxies in the nearest groups) are defined as those having the same parameters, either (1) morphological type T, axis ratio R, and maximum rotation velocity VM or (2) T, R, and luminosity index Λc. These two sets provide respectively for 127 and 72 galaxies (28 are in common) distance moduli directly derived from apparent magnitudes and/or diameters. The distances obtained here are compared with various other determinations; the agreement is generally good.

  11. THE ACS NEARBY GALAXY SURVEY TREASURY. IX. CONSTRAINING ASYMPTOTIC GIANT BRANCH EVOLUTION WITH OLD METAL-POOR GALAXIES

    SciTech Connect

    Girardi, Leo; Williams, Benjamin F.; Gilbert, Karoline M.; Rosenfield, Philip; Dalcanton, Julianne J.; Marigo, Paola; Boyer, Martha L.; Dolphin, Andrew; Weisz, Daniel R.; Skillman, Evan; Melbourne, Jason; Olsen, Knut A. G.; Seth, Anil C.

    2010-12-01

    In an attempt to constrain evolutionary models of the asymptotic giant branch (AGB) phase at the limit of low masses and low metallicities, we have examined the luminosity functions and number ratios between AGB and red giant branch (RGB) stars from a sample of resolved galaxies from the ACS Nearby Galaxy Survey Treasury. This database provides Hubble Space Telescope optical photometry together with maps of completeness, photometric errors, and star formation histories for dozens of galaxies within 4 Mpc. We select 12 galaxies characterized by predominantly metal-poor populations as indicated by a very steep and blue RGB, and which do not present any indication of recent star formation in their color-magnitude diagrams. Thousands of AGB stars brighter than the tip of the RGB (TRGB) are present in the sample (between 60 and 400 per galaxy), hence, the Poisson noise has little impact in our measurements of the AGB/RGB ratio. We model the photometric data with a few sets of thermally pulsing AGB (TP-AGB) evolutionary models with different prescriptions for the mass loss. This technique allows us to set stringent constraints on the TP-AGB models of low-mass, metal-poor stars (with M < 1.5 M{sub sun}, [Fe/H]{approx}< -1.0). Indeed, those which satisfactorily reproduce the observed AGB/RGB ratios have TP-AGB lifetimes between 1.2 and 1.8 Myr, and finish their nuclear burning lives with masses between 0.51 and 0.55 M{sub sun}. This is also in good agreement with recent observations of white dwarf masses in the M4 old globular cluster. These constraints can be added to those already derived from Magellanic Cloud star clusters as important mileposts in the arduous process of calibrating AGB evolutionary models.

  12. Submillimetric study of nearby galaxies: A tool for new extragalactic molecules

    NASA Astrophysics Data System (ADS)

    Villicana Pedraza, Ilhuiyolitzin; Guesten, Rolf; Armijos Abendaño, Jairo; Carreto, Francisco; Martin, Sergio; Martin-Pintado, Jesus; Requena-Torres, Miguel; Perez-Beaupuits, Juan Pablo

    2016-07-01

    We present the first submillimetre line survey of extragalactic sources carried out by APEX, the results were presented inside of Villicana-Pedraza phd thesis in 2015. The surveys cover the 0.8 mm atmospheric window toward NGC253, NGC4945 and Arp220. We found HCN, C2H, CN, CS, C34S, HCO+, HNC, CO, N2H+, CH3OH are presents in all the sources, while 13CO,C18O and C17O, HNCO, H2CO, H2CS, SO, NO, SO2 were detected toward NGC253 and NGC4945, 13CN, *CO+, OCS, H2S in Arp220, 13CS, NH2CN, SiO in NGC253, and c-C3H2 in NGC4945 were detected. Column densities and rotation temperatures have been determinate using the Local Thermodinamical Equilibrium(LTE) line profile simulation and fitting in the MADCUBA IJ software. The differences found in the 32S/34S and 18O/17O ratios between the GC and the starburst galaxies NGC 4945 and NGC 253 suggest that the gas is less processed in the latter than in the GC. The high 18O/17O ratios in the galaxies NGC 4945 and NGC 253 suggest also material less processed in the nuclei of these galaxies than in the GC. This is consistent with the claim that 17O is a more representative primary product than 18O in stellar nucleosynthesis (Wilson and Rood 1994); Also, we did a Multitransitions study of H3O+ at 307GHz, 364GHz, 388GHz and 396GHz. From our non-LTE analysis of H3O+ in NGC253 with RADEX we found that the collisional excitation cannot explain the observed intensity of the ortho 396 GHz line. Excitation by radiation from the dust in the Far-IR can roughly explain the observations if the H2 densities are relatively low. From the derived H3O+ column densities we conclude that the chemistry of this molecule is dominated by ionization produce by the starburst in NGC253 (UV radiation from the O stars) and Arp 220 (cosmic rays from the supernovae) and likely from the AGN in NGC4549 (X-rays ); We report, for the first time, the tentative detection of the molecular ion HCNH+ (precursor of HCN and HNC) toward a galaxy, NGC4945, the abundance is much

  13. The abundance and spatial distribution of ultra-diffuse galaxies in nearby galaxy clusters

    NASA Astrophysics Data System (ADS)

    van der Burg, Remco F. J.; Muzzin, Adam; Hoekstra, Henk

    2016-05-01

    Recent observations have highlighted a significant population of faint but large (reff> 1.5 kpc) galaxies in the Coma cluster. The origin of these ultra diffuse galaxies (UDGs) remains puzzling, as the interpretation of these observational results has been hindered by the (partly) subjective selection of UDGs, and the limited study of only the Coma (and some examples in the Virgo-) cluster. In this paper we extend the study of UDGs using eight clusters in the redshift range 0.044 galaxies. We find that the abundance of the UDGs we can detect increases with cluster mass, reaching ~200 in typical haloes of M200 ≃ 1015M⊙. For the ensemble cluster we measure the size distribution of UDGs, their colour-magnitude distribution, and their completeness-corrected radial density distribution within the clusters. The morphologically-selected cluster UDGs have colours consistent with the cluster red sequence, and have a steep size distribution that, at a given surface brightness, declines as n [ dex-1 ] ∝ reff-3.4 ± 0.2. Their radial distribution is significantly steeper than NFW in the outskirts, and is significantly shallower in the inner parts. We find them to follow the same radial distribution as the more massive quiescent galaxies in the clusters, except within the core region of r ≲ 0.15 × R200 (or ≲ 300 kpc). Within this region the number density of UDGs drops and is consistent with zero. These diffuse galaxies can only resist tidal forces down to this cluster-centric distance if they are highly centrally dark-matter dominated. The observation that the radial distribution of more compact dwarf galaxies (reff< 1.0 kpc) with similar luminosities follows the same distribution as the UDGs, but exist down to a smaller distance of 100 kpc from the

  14. BRIGHT ULTRAVIOLET REGIONS AND STAR FORMATION CHARACTERISTICS IN NEARBY DWARF GALAXIES

    SciTech Connect

    Melena, Nicholas W.; Hunter, Deidre A.; Zernow, Lea; Elmegreen, Bruce G. E-mail: dah@lowell.edu E-mail: bge@us.ibm.com

    2009-11-15

    We compare star formation in the inner and outer disks of 11 dwarf irregular galaxies (dIm) within 3.6 Mpc. The regions are identified on Galaxy Evolution Explorer near-UV images, and modeled with UV, optical, and near-IR colors to determine masses and ages. A few galaxies have made 10{sup 5}-10{sup 6} M {sub sun} complexes in a starburst phase, while others have not formed clusters in the last 50 Myr. The maximum region mass correlates with the number of regions as expected from the size-of-sample effect. We find no radial gradients in region masses and ages, even beyond the realm of H{alpha} emission, although there is an exponential decrease in the luminosity density and number density of the regions with radius. H{alpha} is apparently lacking in the outer parts only because nebular emission around massive stars is too faint to see. The outermost regions for the five galaxies with H I data formed at average gas surface densities of 1.9-5.9 M {sub sun} pc{sup -2}. These densities are at the low end of commonly considered thresholds for star formation and imply either that local gas densities are higher before star formation begins or subthreshold star formation is possible. The first case could be explained by supernovae triggering and other local processes, while the second case could be explained by gravitational instabilities with angular momentum loss in growing condensations. The distribution of regions on a log(mass) - log(age) plot is examined. The distribution is usually uniform along log(age) for equal intervals of log(mass) and this implies a region count that varies as 1/age. This variation results from either an individual region mass that varies as 1/age or a region disruption probability that varies as 1/age. A correlation between fading-corrected surface brightness and age suggests the former. The implied loss of mass is from fading of region envelopes below the surface brightness limit.

  15. Optical observations of NGC 2915: A nearby blue compact dwarf galaxy

    NASA Technical Reports Server (NTRS)

    Meurer, G. R.; Mackie, G.; Carignan, C.

    1994-01-01

    time scales commonly quoted. However, shortly after the formation of a massive (10(exp 6) solar mass) cluster a BCD will have all the properties of strong starburst galaxy).

  16. What powers the starburst activity of NGC 1068? Star-driven gravitational instabilities caught in the act

    NASA Astrophysics Data System (ADS)

    Romeo, Alessandro B.; Fathi, Kambiz

    2016-08-01

    We explore the role that gravitational instability plays in NGC 1068, a nearby Seyfert galaxy that exhibits unusually vigorous starburst activity. For this purpose, we use the Romeo-Falstad disc instability diagnostics and data from the BIMA Survey of Nearby Galaxies, the Sloan Digital Sky Survey and the Spectrographic Areal Unit for Research on Optical Nebulae. Our analysis illustrates that NGC 1068 is a gravitationally unstable `monster'. Its starburst disc is subject to unusually powerful instabilities. Several processes, including feedback from the active galactic nucleus and starburst activity, try to quench such instabilities from inside out by depressing the surface density of molecular gas across the central kpc, but they do not succeed. Gravitational instability `wins' because it is driven by the stars via their much higher surface density. In this process, stars and molecular gas are strongly coupled, and it is such a coupling that ultimately triggers local gravitational collapse/fragmentation in the molecular gas.

  17. High Mass X-ray Binaries in Nearby Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Rangelov, Blagoy

    High Mass X-ray Binaries (HMXBs), in which a compact object, either black hole or neutron star, is accreting material from a young, massive donor star, often dominate the high-energy emission from nearby star-forming galaxies. These high mass pairs are believed to form in star clusters, where most massive star formation takes place, but to become displaced from their parent clusters either because they are dynamically ejected or because their parent cluster has dissolved. We have conducted a systematic study of the formation and evolution of bright HMXBs in eight nearby galaxies, by detecting HMXBs from their X-ray emission in Chandra X-ray Observatory observations, and identifying their parent clusters and donor stars in optical observations taken with the Hubble Space Telescope. We use the X-ray and optical properties of these systems to determine the ages of the binaries, whether the compact objects are black holes or neutron stars, and to constrain the masses of the donor stars.

  18. The mass of the central black hole in the nearby Seyfert galaxy NGC 5273

    SciTech Connect

    Bentz, Misty C.; Horenstein, Daniel; Bazhaw, Craig; Manne-Nicholas, Emily R.; Ou-Yang, Benjamin J.; Anderson, Matthew; Jones, Jeremy; Norris, Ryan P.; Parks, J. Robert; Saylor, Dicy; Teems, Katherine G.; Turner, Clay

    2014-11-20

    We present the results of a reverberation-mapping program targeting NGC 5273, a nearby early-type galaxy with a broad-lined active galactic nucleus (AGN). Over the course of the monitoring program, NGC 5273 showed strong variability that allowed us to measure time delays in the responses of the broad optical recombination lines to changes in the continuum flux. A weighted average of these measurements results in a black hole mass determination of M {sub BH} = (4.7 ± 1.6) × 10{sup 6} M {sub ☉}. An estimate of the size of the black hole sphere of influence in NGC 5273 puts it just at the limit of the resolution achievable with current ground-based large aperture telescopes. NGC 5273 is therefore an important future target for a black hole mass determination from stellar dynamical modeling, especially because it is the only nearby early-type galaxy hosting an AGN with a reverberation-based mass, allowing the best comparison for the masses determined from these two techniques.

  19. 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.

  20. Deep Chandra Observations of the Compact Starburst Galaxy Henize 2–10: X-Rays from the Massive Black Hole

    NASA Astrophysics Data System (ADS)

    Reines, Amy E.; Reynolds, Mark T.; Miller, Jon M.; Sivakoff, Gregory R.; Greene, Jenny E.; Hickox, Ryan C.; Johnson, Kelsey E.

    2016-10-01

    We present follow-up X-ray observations of the candidate massive black hole (BH) in the nucleus of the low-mass, compact starburst galaxy Henize 2–10. Using new high-resolution observations from the Chandra X-ray Observatory totaling 200 ks in duration, as well as archival Chandra observations from 2001, we demonstrate the presence of a previously unidentified X-ray point source that is spatially coincident with the known nuclear radio source in Henize 2–10 (i.e., the massive BH). We show that the hard X-ray emission previously identified in the 2001 observation is dominated by a source that is distinct from the nucleus, with the properties expected for a high-mass X-ray binary. The X-ray luminosity of the nuclear source suggests the massive BH is radiating significantly below its Eddington limit (∼10{}-6 {L}{Edd}), and the soft spectrum resembles other weakly accreting massive BHs including Sagittarius A*. Analysis of the X-ray light curve of the nucleus reveals the tentative detection of a ∼9 hr periodicity, although additional observations are required to confirm this result. Our study highlights the need for sensitive high-resolution X-ray observations to probe low-level accretion, which is the dominant mode of BH activity throughout the universe.

  1. A CENSUS OF BROAD-LINE ACTIVE GALACTIC NUCLEI IN NEARBY GALAXIES: COEVAL STAR FORMATION AND RAPID BLACK HOLE GROWTH

    SciTech Connect

    Trump, Jonathan R.; Fang, Jerome J.; Faber, S. M.; Koo, David C.; Kocevski, Dale D.

    2013-02-15

    We present the first quantified, statistical map of broad-line active galactic nucleus (AGN) frequency with host galaxy color and stellar mass in nearby (0.01 < z < 0.11) galaxies. Aperture photometry and z-band concentration measurements from the Sloan Digital Sky Survey are used to disentangle AGN and galaxy emission, resulting in estimates of uncontaminated galaxy rest-frame color, luminosity, and stellar mass. Broad-line AGNs are distributed throughout the blue cloud and green valley at a given stellar mass, and are much rarer in quiescent (red sequence) galaxies. This is in contrast to the published host galaxy properties of weaker narrow-line AGNs, indicating that broad-line AGNs occur during a different phase in galaxy evolution. More luminous broad-line AGNs have bluer host galaxies, even at fixed mass, suggesting that the same processes that fuel nuclear activity also efficiently form stars. The data favor processes that simultaneously fuel both star formation activity and rapid supermassive black hole accretion. If AGNs cause feedback on their host galaxies in the nearby universe, the evidence of galaxy-wide quenching must be delayed until after the broad-line AGN phase.

  2. Astrochemistry and star formation in nearby galaxies: from galaxy disks to hot nuclei

    NASA Astrophysics Data System (ADS)

    Aalto, S.

    2016-05-01

    Studying the molecular phase of the interstellar medium in galaxies is fundamental for the understanding of the onset and evolution of compact and extended star formation, and of the growth of supermassive black holes. Molecular line emission is an excellent tracer of chemical, physical and dynamical conditions in the cold neutral gas. Key molecules in extragalactic studies are e.g. HCN, HCO+, HC3N, SiO, CH3OH, H2O. Furthermore, we can use IR excited molecular emission to probe the very inner regions of luminous infrared galaxies allowing us to get past the optically thick dust barrier of the compact obscured nuclei where lines of CO, HCN and HCO+ in their vibrational ground state (ν=0) may be self-absorbed. Finally, molecular outflows and their chemistry are briefly discussed - including new ALMA results on for example the outflow of the lenticular galaxy</