Science.gov

Sample records for andromeda spiral galaxy

  1. Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Walterbos, R.; Murdin, P.

    2000-11-01

    The Andromeda galaxy is the closest SPIRAL GALAXY to the MILKY WAY, just visible to the naked eye on a dark night as a faint smudge of light in the constellation Andromeda. The earliest records of the Andromeda nebula, as it is still often referred to, date back to AD 964, to the `Book of the Fixed Stars' published by the Persian astronomer AL-SÛFI. The first European to officially note the Andro...

  2. Andromeda Galaxy

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    This image is a Galaxy Evolution Explorer observation of the large galaxy in Andromeda, Messier 31. The Andromeda galaxy is the most massive in the local group of galaxies that includes our Milky Way. Andromeda is the nearest large galaxy to our own. The image is a mosaic of 10 separate Galaxy Evolution Explorer images taken in September, 2003. The color image (with near ultraviolet shown by red and far ultraviolet shown by blue) shows blue regions of young, hot, high mass stars tracing out the spiral arms where star formation is occurring, and the central orange-white 'bulge' of old, cooler stars formed long ago. The star forming arms of Messier 31 are unusual in being quite circular rather than the usual spiral shape. Several companion galaxies can also be seen. These include Messier 32, a dwarf elliptical galaxy directly below the central bulge and just outside the spiral arms, and Messier 110 (M110), which is above and to the right of the center. M110 has an unusual far ultraviolet bright core in an otherwise 'red,' old star halo. Many other regions of star formation can be seen far outside the main body of the galaxy.

  3. Amazing Andromeda Galaxy

    NASA Technical Reports Server (NTRS)

    2006-01-01

    The many 'personalities' of our great galactic neighbor, the Andromeda galaxy, are exposed in this new composite image from NASA's Galaxy Evolution Explorer and the Spitzer Space Telescope.

    The wide, ultraviolet eyes of Galaxy Evolution Explorer reveal Andromeda's 'fiery' nature -- hotter regions brimming with young and old stars. In contrast, Spitzer's super-sensitive infrared eyes show Andromeda's relatively 'cool' side, which includes embryonic stars hidden in their dusty cocoons.

    Galaxy Evolution Explorer detected young, hot, high-mass stars, which are represented in blue, while populations of relatively older stars are shown as green dots. The bright yellow spot at the galaxy's center depicts a particularly dense population of old stars.

    Swaths of red in the galaxy's disk indicate areas where Spitzer found cool, dusty regions where stars are forming. These stars are still shrouded by the cosmic clouds of dust and gas that collapsed to form them.

    Together, Galaxy Evolution Explorer and Spitzer complete the picture of Andromeda's swirling spiral arms. Hints of pinkish purple depict regions where the galaxy's populations of hot, high-mass stars and cooler, dust-enshrouded stars co-exist.

    Located 2.5 million light-years away, the Andromeda is our largest nearby galactic neighbor. The galaxy's entire disk spans about 260,000 light-years, which means that a light beam would take 260,000 years to travel from one end of the galaxy to the other. By comparison, our Milky Way galaxy's disk is about 100,000 light-years across.

    This image is a false color composite comprised of data from Galaxy Evolution Explorer's far-ultraviolet detector (blue), near-ultraviolet detector (green), and Spitzer's multiband imaging photometer at 24 microns (red).

  4. Neutral hydrogen survey of andromeda galaxy.

    PubMed

    Brundage, W D; Kraus, J D

    1966-07-22

    A neutral hydrogen survey of the Andromeda galaxy (M31) has been conducted with the 260-foot (80m) Ohio State University radio telescope. The neutral hydrogen is concentrated in the spiral arm regions, with but relatively small amounts near the center of the galaxy. Similar deficiencies have been found near the center of M33 and our galaxy, suggesting similar evolutionary processes in the three galaxies. PMID:17839713

  5. Unveiling the Boxy Bulge and Bar of the Andromeda Spiral Galaxy

    NASA Astrophysics Data System (ADS)

    Beaton, R. L.; Athanassoula, E.; Majewski, S. R.; Guhathakurta, P.; Skrutskie, M. F.; Patterson, R. J.; Bureau, M.

    2005-12-01

    For the past 50 years a number of studies have suggested that the center of M31 may be barred. These optical studies, however, have been hampered by the highly inclined (i=77.5o) disk of M31 and the obscuring effects of its embedded dust, which strongly influence the observed isophotal structure of the M31 center. We analyze a new near-infrared survey of M31 by the Two Micron All Sky Survey (2MASS) 6X program. These data, covering the full extent of the optical disk, present a view of the central structure of M31 almost completely unfettered by dust. This new portrait vividly reveals a central bulge dominating the near infrared light profile from 3 to 1000 arcsecs along the semi-major axis, and with a number of interesting properties: (1) prominent boxy isophotes across the extent of the bulge, (2) a position angle inclined by about 10o from that of the M31 disk, (3) strong isophotal twisting in the innermost regions of the bulge, and (4) the presence of ansae symmetrically extending beyond the bulge along the position angle of the galaxy disk. In other highly inclined disks such properties have been associated with the presence of central bars obscured by projection effects. In the case of M31, these features have been well reproduced in a fully self consistent N-body simulation of a barred galaxy with a boxy bulge. The models further suggest the existence of an additional classical bulge component at the center of M31, and imply that the bar itself extends beyond the observationally established extent of the boxy bulge. This publication makes use of data products from 2MASS, which is a joint project of U Mass and IPAC/CalTech, funded by NASA and the NSF. This work was supported by NSF grants AST-0307842 and AST-0307966, as well as a SIM Key Project grant, NASA/JPL contract 1228235. MFS acknowledges support from NASA/JPL contract 1234021. This work was also partially supported by the Celerity Foundation. EA thanks the INSU/CNRS, the Région PACA and the University

  6. Tidal interaction of small satellite galaxies with spiral primaries

    NASA Technical Reports Server (NTRS)

    Byrd, Gene G.

    1988-01-01

    The interaction of the disks of spiral galaxies and small companions is discussed. The gravitational drag effects of the disk on small satellites are of particular interest. Studies of the Andromeda Galaxy and its satellites, M32 and NGC 205, reveal the usefulness of few-body test-particle simulations in explaining many features of spiral galaxies and their satellites.

  7. Rebuilding Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    2005-01-01

    Major Observing Programme Leads to New Theory of Galaxy Formation Summary Most present-day large galaxies are spirals, presenting a disc surrounding a central bulge. Famous examples are our own Milky Way or the Andromeda Galaxy. When and how did these spiral galaxies form? Why do a great majority of them present a massive central bulge? An international team of astronomers [1] presents new convincing answers to these fundamental questions. For this, they rely on an extensive dataset of observations of galaxies taken with several space- and ground-based telescopes. In particular, they used over a two-year period, several instruments on ESO's Very Large Telescope. Among others, their observations reveal that roughly half of the present-day stars were formed in the period between 8,000 million and 4,000 million years ago, mostly in episodic burst of intense star formation occurring in Luminous Infrared Galaxies. From this and other evidence, the astronomers devised an innovative scenario, dubbed the "spiral rebuilding". They claim that most present-day spiral galaxies are the results of one or several merger events. If confirmed, this new scenario could revolutionise the way astronomers think galaxies formed. PR Photo 02a/05: Luminosity - Oxygen Abundance Relation for Galaxies (VLT) PR Photo 02b/05: The Spiral Rebuilding Scenario A fleet of instruments How and when did galaxies form? How and when did stars form in these island universes? These questions are still posing a considerable challenge to present-day astronomers. Front-line observational results obtained with a fleet of ground- and space-based telescopes by an international team of astronomers [1] provide new insights into these fundamental issues. For this, they embarked on an ambitious long-term study at various wavelengths of 195 galaxies with a redshift [2] greater than 0.4, i.e. located more than 4000 million light-years away. These galaxies were studied using ESO's Very Large Telescope, as well as the

  8. The dwarf spheroidal galaxy Andromeda I

    SciTech Connect

    Mould, J.; Kristian, J. Mount Wilson and Las Campanas Observatories, Pasadena, CA )

    1990-05-01

    Images of Andromeda I in the visual and near-infrared show a giant branch characteristic of galactic globular clusters of intermediate metallicity. The distance of the galaxy is estimated from the tip of the giant branch to be 790 + or - 60 kpc. The physical dimensions and luminosity are similar to those of the dwarf spheroidal in Sculptor. There is no evidence for an intermediate age population in Andromeda I, and appropriate upper limits are specified. There is marginal evidence for a color gradient in the galaxy, a phenomenon not previously noted in a dwarf spheroidal. 21 refs.

  9. Chandra X-Ray Observatory Image of Andromeda Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Chandra X-Ray Observatory took this first x-ray picture of the Andromeda Galaxy (M31) on October 13, 1999. The blue dot in the center of the image is a 'cool' million-degree x-ray source where a supermassive black hole with the mass of 30-million suns is located. The x-rays are produced by matter furneling toward the black hole. Numerous other hotter x-ray sources are also apparent. Most of these are probably due to x-ray binary systems, in which a neutron star or black hole is in close orbit around a normal star. While the gas falling into the central black hole is cool, it is only cool by comparison to the 100 other x-ray sources in the Andromeda Galaxy. To be detected by an x-ray telescope, the gas must have a temperature of more than a million degrees. The Andromeda Galaxy is our nearest neighbor spiral galaxy at a distance of two million light years. It is similar to our own Milky Way in size, shape, and also contains a supermassive black hole at the center. (Photo Credit: NASA/CXC/SAO/S. Murray, M. Garcia)

  10. The Andromeda galaxy in gamma-rays

    NASA Technical Reports Server (NTRS)

    Oezel, M. E.; Berkhuijsen, E. M.

    1987-01-01

    Implications of high-energy gamma-ray observations of the Andromeda galaxy with the next generation of satellites Gamma-1 and GRO are discussed in the context of the origin of cosmic rays and gamma-ray processes. The present estimate of the total gamma-ray flux of this galaxy at energies above 100 MeV is a factor of about three less than previous estimates.

  11. Superluminous Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Ogle, Patrick M.; Lanz, Lauranne; Nader, Cyril; Helou, George

    2016-02-01

    We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster galaxies, with r-band monochromatic luminosity Lr = 8-14L* (4.3-7.5 × 1044 erg s-1). These super spiral galaxies are also giant and massive, with diameter D = 57-134 kpc and stellar mass Mstars = 0.3-3.4 × 1011M⊙. We find 53 super spirals out of a complete sample of 1616 SDSS galaxies with redshift z < 0.3 and Lr > 8L*. The closest example is found at z = 0.089. We use existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS and Wide-field Infrared Survey Explorer colors are consistent with normal star-forming spirals on the blue sequence. However, the extreme masses and rapid SFRs of 5-65 M⊙ yr-1 place super spirals in a sparsely populated region of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a diverse range of environments, from isolation to cluster centers. We find four super spiral galaxy systems that are late-stage major mergers—a possible clue to their formation. We suggest that super spirals are a remnant population of unquenched, massive disk galaxies. They may eventually become massive lenticular galaxies after they are cut off from their gas supply and their disks fade.

  12. Radio Map of the Andromeda Galaxy.

    PubMed

    Macleod, J M

    1964-07-24

    The University of Illinois radio telescope has resolved the 610.5 Mcy/sec disk component of radio emission from the large galaxy M 31 into several discrete concentrations. In two cases, these correspond to the crossing of the optical major axis by spiral arms. A spur of emission extends southeast from the galaxy near the minor axis. PMID:17816977

  13. Are spiral galaxies heavy smokers

    SciTech Connect

    Davies, J.; Disney, M.; Phillipps, S )

    1990-07-01

    The dustiness of spiral galaxies is discussed. Starburst galaxies and the shortage of truly bright spiral galaxies is cited as evidence that spiral galaxies are far dustier than has been thought. The possibility is considered that the dust may be hiding missing mass.

  14. Spiral Galaxies Stripped Bare

    NASA Astrophysics Data System (ADS)

    2010-10-01

    Six spectacular spiral galaxies are seen in a clear new light in images from ESO's Very Large Telescope (VLT) at the Paranal Observatory in Chile. The pictures were taken in infrared light, using the impressive power of the HAWK-I camera, and will help astronomers understand how the remarkable spiral patterns in galaxies form and evolve. HAWK-I [1] is one of the newest and most powerful cameras on ESO's Very Large Telescope (VLT). It is sensitive to infrared light, which means that much of the obscuring dust in the galaxies' spiral arms becomes transparent to its detectors. Compared to the earlier, and still much-used, VLT infrared camera ISAAC, HAWK-I has sixteen times as many pixels to cover a much larger area of sky in one shot and, by using newer technology than ISAAC, it has a greater sensitivity to faint infrared radiation [2]. Because HAWK-I can study galaxies stripped bare of the confusing effects of dust and glowing gas it is ideal for studying the vast numbers of stars that make up spiral arms. The six galaxies are part of a study of spiral structure led by Preben Grosbøl at ESO. These data were acquired to help understand the complex and subtle ways in which the stars in these systems form into such perfect spiral patterns. The first image shows NGC 5247, a spiral galaxy dominated by two huge arms, located 60-70 million light-years away. The galaxy lies face-on towards Earth, thus providing an excellent view of its pinwheel structure. It lies in the zodiacal constellation of Virgo (the Maiden). The galaxy in the second image is Messier 100, also known as NGC 4321, which was discovered in the 18th century. It is a fine example of a "grand design" spiral galaxy - a class of galaxies with very prominent and well-defined spiral arms. About 55 million light-years from Earth, Messier 100 is part of the Virgo Cluster of galaxies and lies in the constellation of Coma Berenices (Berenice's Hair, named after the ancient Egyptian queen Berenice II). The third

  15. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Chiba, Masashi

    The magnetic-field characteristics in spiral galaxies are investigated, with emphasis on the Milky Way. The dynamo theory is considered, and axisymmetric spiral (ASS) and bisymmetric spiral (BSS) magnetic fields are analyzed. Toroidal and poloidal magnetic fields are discussed.

  16. Backwards Spiral Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Astronomers using NASA's Hubble Space Telescope have found a spiral galaxy that may rotate in the opposite direction from what was expected.

    A picture of the oddball galaxy is available at http://heritage.stsci.edu or http://oposite.stsci.edu/pubinfo/pr/2002/03 or http://www.jpl.nasa.gov/images/wfpc . It was taken in May 2001 by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    The picture showed which side of galaxy NGC 4622 is closer to Earth; that information helped astronomers determine that the galaxy may be spinning clockwise. The image shows NGC 4622 and its outer pair of winding arms full of new stars, shown in blue.

    Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise.

    NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. Astronomers suspect this oddity was caused by the interaction of NGC 4622 with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a smaller companion galaxy.

    Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 lies 111 million light-years away in the direction of the constellation Centaurus.

    The science team, consisting of Drs. Ron Buta and Gene Byrd from the University of Alabama, Tuscaloosa, and Tarsh Freeman of Bevill State

  17. Molecular Gas Velocity Dispersions in the Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Caldú-Primo, Anahi; Schruba, Andreas

    2016-02-01

    In order to characterize the distribution of molecular gas in spiral galaxies, we study the line profiles of CO (1 - 0) emission in Andromeda, our nearest massive spiral galaxy. We compare observations performed with the IRAM 30 m single-dish telescope and with the CARMA interferometer at a common resolution of 23 arcsec ≈ 85 pc × 350 pc and 2.5 km s-1. When fitting a single Gaussian component to individual spectra, the line profile of the single dish data is a factor of 1.5 ± 0.4 larger than the interferometric data one. This ratio in line widths is surprisingly similar to the ratios previously observed in two other nearby spirals, NGC 4736 and NGC 5055, but measured at ˜0.5-1 kpc spatial scale. In order to study the origin of the different line widths, we stack the individual spectra in five bins of increasing peak intensity and fit two Gaussian components to the stacked spectra. We find a unique narrow component of FWHM = 7.5 ± 0.4 km s-1 visible in both the single dish and the interferometric data. In addition, a broad component with FWHM = 14.4 ± 1.5 km s-1 is present in the single-dish data, but cannot be identified in the interferometric data. We interpret this additional broad line width component detected by the single dish as a low brightness molecular gas component that is extended on spatial scales >0.5 kpc, and thus filtered out by the interferometer. We search for evidence of line broadening by stellar feedback across a range of star formation rates but find no such evidence on ˜100 pc spatial scale when characterizing the line profile by a single Gaussian component.

  18. ANDROMEDA XXVIII: A DWARF GALAXY MORE THAN 350 kpc FROM ANDROMEDA

    SciTech Connect

    Slater, Colin T.; Bell, Eric F.; Martin, Nicolas F.

    2011-11-20

    We report the discovery of a new dwarf galaxy, Andromeda XXVIII, using data from the recently released Sloan Digital Sky Survey Data Release 8. The galaxy is a likely satellite of Andromeda, and, at a separation of 365{sup +17}{sub -1} kpc, would be one of the most distant of Andromeda's satellites. Its heliocentric distance is 650{sup +150}{sub -80} kpc, and analysis of its structure and luminosity shows that it has an absolute magnitude of M{sub V} = -8.5{sup +0.4}{sub -1.0} and half-light radius of r{sub h} = 210{sup +60}{sub -50} pc, similar to many other faint Local Group dwarfs. With presently available imaging we are unable to determine whether there is ongoing or recent star formation, which prevents us from classifying it as a dwarf spheroidal or a dwarf irregular.

  19. Molecular Gas in the Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Gerard, Benjamin; Darling, J. K.; Amiri, N.

    2014-01-01

    We present results from an Andromeda Galaxy (M31) survey of star-forming regions based on 24 μm luminosity for H2O masers, NH3 (1,1) and NH3 (2,2) lines, and Hydrogen recombination lines (H66α). Although five H2O masers were detected in the initial survey of 206 regions towards M31, we do not detect additional H2O masers in a follow up survey of 300 similar compact 24 μm regions. We do not detect NH3 (1,1), NH3 (2,2), or H66α lines in any of the 506 regions. The typical rms noise for 3.3 km s-1 channels in individual spectra is 2.5 mJy. Additionally, averaging all 506 spectra, shifted to the correct radial velocity, yields no detection for H2O, NH3 (1,1), NH3 (2,2), or H66α. The typical rms noise for 3.3 km s-1 channels in stacked spectra is 0.13 mJy. The non-detection of NH3 provides an upper limit on NH3 integrated flux, NH3 column density, and corresponding dense gas fraction. We compare the NH3 integrated flux upper limit with Galactic NH3 integrated flux data, scaled to the distance of M31, and find that the M31 NH3 abundance is consistent with the Galactic NH3 abundance. We calculate the ratio of NH3 (1,1) integrated flux to Herschel 500 μm flux density for molecular cloud-sized regions in M31 and the Galaxy. Comparing this ratio between M31 and the Galaxy also indicates that the M31 NH3 abundance is consistent with the Galactic NH3 abundance.

  20. Observations of the andromeda galaxy at 11-centimeter wavelength.

    PubMed

    Cooley, R C; Roberts, M S; Swenson, G W

    1967-05-26

    Observations of the Andromeda galaxy (M31) at 2695 megahertz reveal more detail than do earlier measurements at lower frequency. The region is highly confused but there is apparently a more dense clustering of sources within the optical outline of the galaxy than without. One source (OA33) near M31 has an interesting. flat spectrum. PMID:17774052

  1. A survey of HI gas toward the Andromeda galaxy

    NASA Astrophysics Data System (ADS)

    Kerp, J.; Kalberla, P. M. W.; Ben Bekhti, N.; Flöer, L.; Lenz, D.; Winkel, B.

    2016-05-01

    Context. The subsequent coalescence of low-mass halos over cosmic time is thought to be the major formation channel of massive spiral galaxies like the Milky Way and the Andromeda galaxy (M 31). The gaseous halo of a massive galaxy is considered to be the reservoir of baryonic matter persistently fueling the star formation in the disk. Because of its proximity, M 31 is the ideal object for studying the structure of the halo gas in great detail. Aims: Using the latest neutral atomic hydrogen (HI) data of the Effelsberg-Bonn HI Survey (EBHIS) allows comprising a comprehensive inventory of gas associated with M 31. The primary aim is to differentiate between physical structures belonging to the Milky Way Galaxy and M 31 and accordingly to test the presence of a M 31 neutral gaseous halo. Methods: Analyzing the spatially fully sampled EBHIS data makes it feasible to trace coherent HI structures in space and radial velocity. To disentangle Milky Way and M 31 HI emission we use a new approach, along with the traditional path of setting an upper radial velocity limit, by calculating a difference second moment map. Results: We argue that M 31's disk is physically connected to an asymmetric HI halo of tens of kpc size, the M 31 cloud. We confirm the presence of a coherent low-velocity HI filament located in between M 31 and M 33 aligned at the sky with the clouds at systemic velocity. The physical parameters of the HI filament are comparable to those of the HI clouds at systemic velocity. We also detected an irregularly shaped HI cloud that is is positionally located close to but offset from the stellar body of And XIX.

  2. The Prolate Dark Matter Halo of the Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Hayashi, Kohei; Chiba, Masashi

    2014-07-01

    We present new limits on the global shape of the dark matter halo in the Andromeda galaxy using and generalizing non-spherical mass models developed by Hayashi & Chiba and compare our results with theoretical predictions of cold dark matter (CDM) models. This is motivated by the fact that CDM models predict non-spherical virialized dark halos, which reflect the process of mass assembly in the galactic scale. Applying our models to the latest kinematic data of globular clusters and dwarf spheroidal galaxies in the Andromeda halo, we find that the most plausible cases for Andromeda yield a prolate shape for its dark halo, irrespective of assumed density profiles. We also find that this prolate dark halo in Andromeda is consistent with theoretical predictions in which the satellites are distributed anisotropically and preferentially located along major axes of their host halos. It is a reflection of the intimate connection between galactic dark matter halos and the cosmic web. Therefore, our result is profound in understanding internal dynamics of halo tracers in Andromeda, such as orbital evolutions of tidal stellar streams, which play important roles in extracting the abundance of CDM subhalos through their dynamical effects on stream structures.

  3. The prolate dark matter halo of the Andromeda galaxy

    SciTech Connect

    Hayashi, Kohei; Chiba, Masashi E-mail: chiba@astr.tohoku.ac.jp

    2014-07-01

    We present new limits on the global shape of the dark matter halo in the Andromeda galaxy using and generalizing non-spherical mass models developed by Hayashi and Chiba and compare our results with theoretical predictions of cold dark matter (CDM) models. This is motivated by the fact that CDM models predict non-spherical virialized dark halos, which reflect the process of mass assembly in the galactic scale. Applying our models to the latest kinematic data of globular clusters and dwarf spheroidal galaxies in the Andromeda halo, we find that the most plausible cases for Andromeda yield a prolate shape for its dark halo, irrespective of assumed density profiles. We also find that this prolate dark halo in Andromeda is consistent with theoretical predictions in which the satellites are distributed anisotropically and preferentially located along major axes of their host halos. It is a reflection of the intimate connection between galactic dark matter halos and the cosmic web. Therefore, our result is profound in understanding internal dynamics of halo tracers in Andromeda, such as orbital evolutions of tidal stellar streams, which play important roles in extracting the abundance of CDM subhalos through their dynamical effects on stream structures.

  4. RR Lyrae stars in the Andromeda satellite galaxies

    NASA Astrophysics Data System (ADS)

    Cusano, F.; Garofalo, A.; Clementini, G.

    2016-05-01

    In this contribution we summarize results on the search for variable stars and the study of the resolved stellar populations in four dwarf spheroidal satellites of the Andromeda galaxy that we have observed with the Large Binocular Cameras (LBC) at the Large Binocular Telescope (LBT).

  5. Galaxy Zoo: passive red spirals

    NASA Astrophysics Data System (ADS)

    Masters, Karen L.; Mosleh, Moein; Romer, A. Kathy; Nichol, Robert C.; Bamford, Steven P.; Schawinski, Kevin; Lintott, Chris J.; Andreescu, Dan; Campbell, Heather C.; Crowcroft, Ben; Doyle, Isabelle; Edmondson, Edward M.; Murray, Phil; Raddick, M. Jordan; Slosar, Anže; Szalay, Alexander S.; Vandenberg, Jan

    2010-06-01

    We study the spectroscopic properties and environments of red (or passive) spiral galaxies found by the Galaxy Zoo project. By carefully selecting face-on disc-dominated spirals, we construct a sample of truly passive discs (i.e. they are not dust reddened spirals, nor are they dominated by old stellar populations in a bulge). As such, our red spirals represent an interesting set of possible transition objects between normal blue spiral galaxies and red early types, making up ~6 per cent of late-type spirals. We use optical images and spectra from Sloan Digital Sky Survey to investigate the physical processes which could have turned these objects red without disturbing their morphology. We find red spirals preferentially in intermediate density regimes. However, there are no obvious correlations between red spiral properties and environment suggesting that environment alone is not sufficient to determine whether a galaxy will become a red spiral. Red spirals are a very small fraction of all spirals at low masses (M* < 1010 Msolar), but are a significant fraction of the spiral population at large stellar masses showing that massive galaxies are red independent of morphology. We confirm that as expected, red spirals have older stellar populations and less recent star formation than the main spiral population. While the presence of spiral arms suggests that a major star formation could not have ceased a long ago (not more than a few Gyr), we show that these are also not recent post-starburst objects (having had no significant star formation in the last Gyr), so star formation must have ceased gradually. Intriguingly, red spirals are roughly four times as likely than the normal spiral population to host optically identified Seyfert/low-ionization nuclear emission region (LINER; at a given stellar mass and even accounting for low-luminosity lines hidden by star formation), with most of the difference coming from the objects with LINER-like emission. We also find a

  6. Rocket ultraviolet imagery of the Andromeda galaxy

    NASA Technical Reports Server (NTRS)

    Carruthers, G. R.; Opal, C. B.; Heckathorn, H. M.

    1978-01-01

    Far-UV electrographic imagery of M31 is presented which was obtained during a sounding-rocket flight with an electrographic Schmidt camera sensitive in the wavelength range from 1230 to 2000 A. The resolution in the imagery is such that 50% of the energy from a point source is confined within a circle 40 arcsec in radius. Two conspicuous features are observed in the UV image of M31: one corresponding to a bright association (NGC 206) in the SW region of the disk and one centered on the galactic nucleus. Indications of the general spiral-arm structure are also evident. Absolute photometry and brightness distributions are obtained for the observed features, and both the central region and NGC 206 are shown to be diffuse sources. It is found that the brightness distribution of the central region is a flat ellipse with its major axis closely aligned with the major axis of the galaxy, which favors a source model consisting of young early-type stars close to the galactic plane and constitutes strong evidence against a nonthermal point source at the galactic center.

  7. HUBBLE REVEALS 'BACKWARDS' SPIRAL GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have found a spiral galaxy that may be spinning to the beat of a different cosmic drummer. To the surprise of astronomers, the galaxy, called NGC 4622, appears to be rotating in the opposite direction to what they expected. Pictures by NASA's Hubble Space Telescope helped astronomers determine that the galaxy may be spinning clockwise by showing which side of the galaxy is closer to Earth. A Hubble telescope photo of the oddball galaxy is this month's Hubble Heritage offering. The image shows NGC 4622 and its outer pair of winding arms full of new stars [shown in blue]. Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. To add to the conundrum, NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction it is rotating. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise. NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. What caused this galaxy to behave differently from most galaxies? Astronomers suspect that NGC 4622 interacted with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a small companion galaxy. The galaxy's core provides new evidence for a merger between NGC 4622 and a smaller galaxy. This information could be the key to understanding the unusual leading arms. Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way Galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 resides 111 million light-years away in the constellation Centaurus. The pictures were taken in May 2001 with Hubble

  8. THE SPIRAL GALAXY M100

    NASA Technical Reports Server (NTRS)

    2002-01-01

    An image of the grand design of spiral galaxy M100 obtained with NASA's Hubble Space Telescope resolves individual stars within the majestic spiral arms. (These stars typically appeared blurred together when viewed with ground-based telescopes.) Hubble has the ability to resolve individual stars in other galaxies and measure accurately the light from very faint stars. This makes space telescope invaluable for identifying a rare class of pulsating stars, called Cepheid Variable stars embedded within M100's spiral arms. Cepheids are reliable cosmic distance mileposts. The interval it takes for the Cepheid to complete one pulsation is a direct indication of the stars's intrinsic brightness. This value can be used to make a precise measurement of the galaxy's distance, which turns out to be 56 million light-years. M100 (100th object in the Messier catalog of non-stellar objects) is a majestic face-on spiral galaxy. It is a rotating system of gas and stars, similar to our own galaxy, the Milky Way. Hubble routinely can view M100 with a level of clarity and sensitivity previously possible only for the very few nearby galaxies that compose our 'Local Group.'' M100 is a member of the huge Virgo cluster of an estimated 2,500 galaxies. The galaxy can be seen by amateur astronomers as a faint, pinwheel-shaped object in the spring constellation Coma Berenices. Technical Information: The Hubble Space Telescope image was taken on December 31, 1993 with the Wide Field Planetary Camera 2 (WFPC 2). This color picture is a composite of several images taken in different colors of light. Blue corresponds to regions containing hot newborn stars. The Wide Field and Planetary Camera 2 was developed by the Jet Propulsion Laboratory (JPL) and managed by the Goddard Space Flight Center for NASA's Office of Space Science. Credit: J. Trauger, JPL and NASA

  9. Andromeda

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    (abbrev. And, gen. Andromedae; area 722 sq. deg.) A northern constellation that lies between Perseus and Pegasus, and culminates at midnight in early October. It is named after the daughter of King Cepheus and Queen Cassiopeia in Greek mythology, who was rescued by Perseus from being sacrificed to the sea monster Cetus, and is usually shown on early celestial charts as a chained maiden. Its brigh...

  10. Chandra Finds a "Cool" Black Hole at the Heart of the Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    2000-01-01

    In its first look at the Andromeda Galaxy (M31), NASA's Chandra X-ray Observatory has found that the gas funneling into a supermassive black hole in the heart of this galaxy is a "cool" million degrees Celsius. This unexpected result adds one more quirk to the strange behavior previously observed at the center of M31. A team of scientists from the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass., reported on this observation at the 195th national meeting of the American Astronomical Society in Atlanta, Ga. The team is led by Drs. Stephen Murray and Michael Garcia, and includes Drs. Frank Primini, William Forman, Christine Jones, and Ralph Kraft. Chandra took its first X-ray picture of the Andromeda Galaxy with the Advanced CCD Imaging Spectrometer on October 13, 1999. More than100 individual X-ray sources were seen. One of these sources was at the previously determined position of the central supermassive black hole, which has the mass of 30 million suns. With many X-ray emitting stars in the center of M31 there was a slight chance that one of them might be at this position just by coincidence. The low temperature of the suspected central source, as compared to the other sources, gave the team the clue they needed. "When we found that what we suspected was the central object was also anomalously cool, we KNEW we had it- one coincidence might be believable, but two was too much to ignore!" said Garcia. While the gas falling into the central black hole is cool, it is only cool by comparison to the 100 other X-ray sources in the Andromeda Galaxy. To be detected by an X-ray telescope, the gas must have a temperature of more than a million degrees Celsius. The typical X-ray star in the Andromeda Galaxy has a temperature of several tens of millions of degrees. In contrast, the temperature of the supermassive black hole source is a few million degrees Celsius. The Andromeda Galaxy is our nearest neighbor spiral galaxy at a distance of two million light years

  11. PERSEUS I: A DISTANT SATELLITE DWARF GALAXY OF ANDROMEDA

    SciTech Connect

    Martin, Nicolas F.; Laevens, Benjamin P. M.; Schlafly, Edward F.; Rix, Hans-Walter; Slater, Colin T.; Bell, Eric F.; Bernard, Edouard J.; Ferguson, Annette M. N.; Finkbeiner, Douglas P.; Burgett, William S.; Chambers, Kenneth C.; Hodapp, Klaus W.; Kaiser, Nicholas; Kudritzki, Rolf-Peter; Magnier, Eugene A.; Morgan, Jeffrey S.; Tonry, John L.; Draper, Peter W.; Metcalfe, Nigel; Price, Paul A.; and others

    2013-12-10

    We present the discovery of a new dwarf galaxy, Perseus I/Andromeda XXXIII, found in the vicinity of Andromeda (M31) in stacked imaging data from the Pan-STARRS1 3π survey. Located 27.°9 away from M31, Perseus I has a heliocentric distance of 785 ± 65 kpc, compatible with it being a satellite of M31 at 374{sub −10}{sup +14} kpc from its host. The properties of Perseus I are typical for a reasonably bright dwarf galaxy (M{sub V} = –10.3 ± 0.7), with an exponential half-light radius of r{sub h} = 1.7 ± 0.4 arcmin or r{sub h}=400{sub −85}{sup +105} pc at this distance, and a moderate ellipticity (ϵ=0.43{sub −0.17}{sup +0.15}). The late discovery of Perseus I is due to its fairly low surface brightness (μ{sub 0}=25.7{sub −0.9}{sup +1.0} mag arcsec{sup –2}), and to the previous lack of deep, high quality photometric data in this region. If confirmed to be a companion of M31, the location of Perseus I, far east from its host, could place interesting constraints on the bulk motion of the satellite system of M31.

  12. DEEP OPTICAL PHOTOMETRY OF SIX FIELDS IN THE ANDROMEDA GALAXY

    SciTech Connect

    Brown, Thomas M.; Smith, Ed; Ferguson, Henry C.; Kalirai, Jason S.; Guhathakurta, Puragra; Renzini, Alvio; Rich, R. Michael; VandenBerg, Don A. E-mail: edsmith@stsci.edu E-mail: jkalirai@stsci.edu E-mail: randy.a.kimble@nasa.gov E-mail: alvio.renzini@oapd.inaf.it E-mail: vandenbe@uvic.ca

    2009-09-01

    Using the Advanced Camera for Surveys on the Hubble Space Telescope, we have obtained deep optical images reaching well below the oldest main-sequence turnoff in six fields of the Andromeda Galaxy. The fields fall at four positions on the southeast minor axis, one position in the giant stellar stream, and one position on the northeast major axis. These data were obtained as part of three large observing programs designed to probe the star formation history of the stellar population in various structures of the galaxy. In this paper, we present the images, catalogs, and artificial star tests for these observing programs as a supplement to the analyses published previously. These high-level science products are also archived at the Multimission Archive at the Space Telescope Science Institute.

  13. Slow bars in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Fridman, A. M.; Khoruzhii, O. V.

    2000-11-01

    Here we put forward some arguments in favour of the existence of slow bars. More then a half of spiral galaxies have in their central regions a bar - a structure in the form of triaxial ellipsoid. Historically two models of the bar were developed - those of the so called ``slow'' and ``fast'' bars. In both cases the bar is in some resonance with the galactic disc region near the bar ends - it is the corotation resonance for a fast bar and the inner Lindblad resonance for a slow bar. For the same angular velocity the fast bar would be larger then the slow bar. Alternatively, for the same size the fast bar would have much higher angular velocity, that being the reason for the terminology used. Up till now, the direct measurement of angular velocity of a bar has been an open problem. This is why all arguments on the nature of bar observed in some particular galaxy are inevitably indirect. Despite the fact that the model of slow bars was developed slightly earlier, the main part of attention was focused on the fast bars. Presently many researchers believe in the existence of the fast bars in real galaxies, while discussions on the existence of the slow bars continue so far. In this Letter we demonstrate that the bar detected in the grand design spiral galaxy NGC 157 is the slow bar.

  14. ANDROMEDA XXIX: A NEW DWARF SPHEROIDAL GALAXY 200 kpc FROM ANDROMEDA

    SciTech Connect

    Bell, Eric F.; Slater, Colin T.; Martin, Nicolas F.

    2011-11-20

    We report the discovery of a new dwarf galaxy, Andromeda XXIX (And XXIX), using data from the recently released Sloan Digital Sky Survey Data Release 8, and confirmed by Gemini North telescope Multi-Object Spectrograph imaging data. And XXIX appears to be a dwarf spheroidal galaxy, separated on the sky by a little more than 15 Degree-Sign from M31, with a distance inferred from the tip of the red giant branch of 730 {+-} 75 kpc, corresponding to a three-dimensional separation from M31 of 207{sup +20}{sub -2} kpc (close to M31's virial radius). Its absolute magnitude, as determined by comparison to the red giant branch luminosity function of the Draco dwarf spheroidal, is M{sub V} = -8.3 {+-} 0.4. And XXIX's stellar populations appear very similar to Draco's; consequently, we estimate a metallicity for And XXIX of [Fe/H] {approx}-1.8. The half-light radius of And XXIX is 360 {+-} 60 pc and its ellipticity is 0.35 {+-} 0.06, typical of dwarf satellites of the Milky Way and M31 at this absolute magnitude range.

  15. Stellar Populations in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    MacArthur, L. A.; Courteau, S.; Bell, E. F.; Holtzman, J. A.

    2004-12-01

    We investigate optical and near-IR color gradients in a sample of 172 low-inclination galaxies spanning Hubble types S0--Irr. The colors are compared to stellar population synthesis models from which luminosity-weighted average ages and metallicities are determined. We explore the effects of different underlying star formation histories and additional bursts of star formation. Because the observed gradients show radial structure, we measure ``inner'' and ``outer'' disk age and metallicity gradients. Relative trends in age and metallicity and their gradients are explored as a function of Hubble type, rotational velocity, total near-IR galaxy magnitude, central surface brightness, and scale length. We find strong correlations in age and metallicity with Hubble type, rotational velocity, total magnitude, and central surface brightness in the sense that earlier-type, faster rotating, more luminous, and higher surface brightness galaxies are older and more metal-rich, suggesting an early and more rapid star formation history for these galaxies. The increasing trends level off for T ⪉ 4 (Sbc and earlier), V {rot} ⪆ 120 km s-1, MK ⪉ -23 mag, and μ 0 ⪉ 18.5 mag arcsec-2. Outer disk gradients are weaker than the inner gradients as expected for a slower variation of the potential and surface brightness in the outer parts. We find that stronger age gradients are associated with weaker metallicity gradients. Relative trends in gradients with galaxy parameters do not agree with predictions of semi-analytic models of hierarchical galaxy formation, possibly as a result of bar-induced radial flows. However, the observed trends are in agreement with chemo-spectro photometric models of spiral galaxy evolution based on CDM-motivated scaling laws but including none of the hierarchical merging characteristics. This implies a strong dependence of the star formation history of spiral galaxies on the galaxy potential and halo spin parameter. L.A.M. and S.C acknowledge support

  16. Andromeda Galaxy: Extension of the 610.5-Megacyle-per-Second Map.

    PubMed

    Dickel, J R; Macleod, J M; Swenson, G W

    1965-11-12

    A radio map of the Andromeda galaxy, M 31, made with the 400-foot (122 m) radio telescope at the University of Illinois has been extended northward to cover the full optical extent of the galaxy. Several condensations of radio emission appear along the major axis of the galaxy, and other radio features are resolved. PMID:17837867

  17. Molecular gas in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Casoli, F.; Sauty, S.; Gerin, M.; Boselli, A.; Fouque, P.; Braine, J.; Gavazzi, G.; Lequeux, J.; Dickey, J.

    1998-03-01

    The molecular hydrogen content of a galaxy is a key parameter for its activity and future evolution. Its variations with basic properties such as size, mass, morphological type, and environment, the ratio of molecular to atomic gas masses, should provide us with a better view of galaxy evolution. Such studies have been done in the past by Sage (1993a) or the FCRAO group (e.g. Young & Knezek 1989), and have led to controversial results, for example about the MHH /MHI ratio. While Sage (1993a), using a distance-limited sample of 65 galaxies and the \\COA line emission as a tracer of the HH mass, finds that most galaxies have MHH /MHI lower than 1, Young & Knezek (1989) and Young et al. (1995), from a different sample of 178 objects, claim equal amounts of gas in the molecular and atomic phase. Here we again tackle this problem, by gathering a much larger sample of 582 objects, not only from the literature but also from several \\COA surveys that we have completed and which are largely unpublished. Our sample is clearly not complete and contains a large number of cluster galaxies as well as many more massive objects than a distance-limited sample. Contrary to previous analyses, we have taken into account the non-detections by using the survival analysis method. Our sample includes 105 isolated galaxies, observed by us, that we use as a reference sample in order to determine whether cluster galaxies are CO-deficient. We find that the ratio of HH and HI masses is on the average lower than 1, with = log(0.20) +/- 0.04 (median = log(0.27) +/- 0.04). For spirals with types Sa to Sc, we have slightly higher values: log(0.28) and log(0.34) respectively. The actual HH masses and MHH /MHI ratios could be lower than given above if, as suggested by recent gamma -ray and 1.3 mm continuum data, the conversion factor between \\COA emissivities and HH masses for large spiral galaxies is lower than the value adopted here (X=2.310(20) cm(-2) /(Kkms(-1) )). The

  18. SEEN AND UNSEEN TIDAL CAUSTICS IN THE ANDROMEDA GALAXY

    SciTech Connect

    Sanderson, R. E.; Bertschinger, E.

    2010-12-20

    Indirect detection of high-energy particles from dark matter interactions is a promising avenue for learning more about dark matter, but is hampered by the frequent coincidence of high-energy astrophysical sources of such particles with putative high-density regions of dark matter. We calculate the boost factor and gamma-ray flux from dark matter associated with two shell-like caustics of luminous tidal debris recently discovered around the Andromeda galaxy, under the assumption that dark matter is its own supersymmetric antiparticle. These shell features could be a good candidate for indirect detection of dark matter via gamma rays because they are located far from the primary confusion sources at the galaxy's center, and because the shapes of the shells indicate that most of the mass has piled up near the apocenter. Using a numerical estimator specifically calibrated to estimate densities in N-body representations with sharp features and a previously determined N-body model of the shells, we find that the largest boost factors do occur in the shells but are only a few percent. We also find that the gamma-ray flux is an order of magnitude too low to be detected with Fermi for likely dark matter parameters, and about two orders of magnitude less than the signal that would have come from the dwarf galaxy that produces the shells in the N-body model. We further show that the radial density profiles and relative radial spacing of the shells, in either dark or luminous matter, is relatively insensitive to the details of the potential of the host galaxy but depends in a predictable way on the velocity dispersion of the progenitor galaxy.

  19. The distribution of alpha elements in Andromeda dwarf galaxies

    SciTech Connect

    Vargas, Luis C.; Geha, Marla C.; Tollerud, Erik J.

    2014-07-20

    We present alpha to iron abundance ratios for 226 individual red giant branch stars in nine dwarf galaxies of the Andromeda (M31) satellite system. The abundances are measured from the combined signal of Mg, Si, Ca, and Ti lines in Keck/DEIMOS medium-resolution spectra. This constitutes the first large sample of alpha abundance ratios measured in the M31 satellite system. The dwarf galaxies in our sample exhibit a variety of alpha abundance ratios, with the average values in each galaxy ranging from approximately solar ([α/Fe] ∼ + 0.0) to alpha-enhanced ([α/Fe] ∼ + 0.5). These variations do not show a correlation with internal kinematics, environment, or stellar density. We confirm radial gradients in the iron abundance of two galaxies out of the five with sufficient data (NGC 185 and And II). There is only tentative evidence for an alpha abundance radial gradient in NGC 185. We homogeneously compare our results to the Milky Way classical dwarf spheroidals, finding evidence for wider variation in average alpha abundance. In the absence of chemical abundances for the M31 stellar halo, we compare to the Milky Way stellar halo. A stellar halo comprised of disrupted M31 satellites is too metal-rich and inconsistent with the Milky Way halo alpha abundance distribution even if considering only satellites with predominantly old stellar populations. The M31 satellite population provides a second system in which to study chemical abundances of dwarf galaxies and reveals a wider variety of abundance patterns than the Milky Way.

  20. PAndAS' CUBS: DISCOVERY OF TWO NEW DWARF GALAXIES IN THE SURROUNDINGS OF THE ANDROMEDA AND TRIANGULUM GALAXIES

    SciTech Connect

    Martin, Nicolas F.; McConnachie, Alan W.; Irwin, Mike; Chapman, Scott; Widrow, Lawrence M.; Ferguson, Annette M. N.; Ibata, Rodrigo A.; Dubinski, John; Babul, Arif; Navarro, Julio; Fardal, Mark; Lewis, Geraint F.; Rich, R. Michael

    2009-11-01

    We present the discovery of two new dwarf galaxies, Andromeda XXI and Andromeda XXII, located in the surroundings of the Andromeda and Triangulum galaxies (M31 and M33). These discoveries stem from the first year data of the Pan-Andromeda Archaeological Survey, a photometric survey of the M31/M33 group conducted with the Megaprime/MegaCam Wide-Field Camera mounted on the Canada-France-Hawaii Telescope. Both satellites appear as spatial overdensities of stars which, when plotted in a color-magnitude diagram, follow metal-poor, [Fe/H] = -1.8, red giant branches at the distance of M31/M33. Andromeda XXI is a moderately bright dwarf galaxy (M{sub V} = -9.9 +- 0.6), albeit with low surface brightness, emphasizing again that many relatively luminous M31 satellites still remain to be discovered. It is also a large satellite, with a half-light radius close to 1 kpc, making it the fourth largest Local Group dwarf spheroidal galaxy after the recently discovered Andromeda XIX, Andromeda II, and Sagittarius around the Milky Way, and supports the trend that M31 satellites are larger than their Milky Way counterparts. Andromeda XXII is much fainter (M{sub V} = -6.5 +- 0.8) and lies a lot closer in projection to M33 than it does to M31 (42 versus 224 kpc), suggesting that it could be the first Triangulum satellite to be discovered. Although this is a very exciting possibility in the context of a past interaction of M33 with M31 and the fate of its satellite system, a confirmation will have to await a good distance estimate to confirm its physical proximity to M33. Along with the dwarf galaxies found in previous surveys of the M31 surroundings, these two new satellites bring the number of dwarf spheroidal galaxies in this region to 20.

  1. A vast, thin plane of corotating dwarf galaxies orbiting the Andromeda galaxy.

    PubMed

    Ibata, Rodrigo A; Lewis, Geraint F; Conn, Anthony R; Irwin, Michael J; McConnachie, Alan W; Chapman, Scott C; Collins, Michelle L; Fardal, Mark; Ferguson, Annette M N; Ibata, Neil G; Mackey, A Dougal; Martin, Nicolas F; Navarro, Julio; Rich, R Michael; Valls-Gabaud, David; Widrow, Lawrence M

    2013-01-01

    Dwarf satellite galaxies are thought to be the remnants of the population of primordial structures that coalesced to form giant galaxies like the Milky Way. It has previously been suspected that dwarf galaxies may not be isotropically distributed around our Galaxy, because several are correlated with streams of H I emission, and may form coplanar groups. These suspicions are supported by recent analyses. It has been claimed that the apparently planar distribution of satellites is not predicted within standard cosmology, and cannot simply represent a memory of past coherent accretion. However, other studies dispute this conclusion. Here we report the existence of a planar subgroup of satellites in the Andromeda galaxy (M 31), comprising about half of the population. The structure is at least 400 kiloparsecs in diameter, but also extremely thin, with a perpendicular scatter of less than 14.1 kiloparsecs. Radial velocity measurements reveal that the satellites in this structure have the same sense of rotation about their host. This shows conclusively that substantial numbers of dwarf satellite galaxies share the same dynamical orbital properties and direction of angular momentum. Intriguingly, the plane we identify is approximately aligned with the pole of the Milky Way's disk and with the vector between the Milky Way and Andromeda. PMID:23282362

  2. STELLAR KINEMATICS OF THE ANDROMEDA II DWARF SPHEROIDAL GALAXY

    SciTech Connect

    Ho, Nhung; Geha, M.; Tollerud, E.; Munoz, R. R.; Guhathakurta, P.; Gilbert, K. M.; Bullock, J.; Beaton, R. L.; Majewski, S. R. E-mail: marla.geha@yale.edu

    2012-10-20

    We present kinematical profiles and metallicity for the M31 dwarf spheroidal (dSph) satellite galaxy Andromeda II (And II) based on Keck DEIMOS spectroscopy of 531 red giant branch stars. Our kinematical sample is among the largest for any M31 satellite and extends out to two effective radii (r {sub eff} = 5.'3 = 1.1 kpc). We find a mean systemic velocity of -192.4 {+-} 0.5 km s{sup -1} and an average velocity dispersion of {sigma} {sub v} = 7.8 {+-} 1.1 km s{sup -1}. While the rotation velocity along the major axis of And II is nearly zero (<1 km s{sup -1}), the rotation along the minor axis is significant with a maximum rotational velocity of v {sub max} = 8.6 {+-} 1.8 km s{sup -1}. We find a kinematical major axis, with a maximum rotational velocity of v {sub max} = 10.9 {+-} 2.4 km s{sup -1}, misaligned by 67 Degree-Sign to the isophotal major axis. And II is thus the first dwarf galaxy with evidence for nearly prolate rotation with a v {sub max}/{sigma} {sub v} = 1.1, although given its ellipticity of {epsilon} = 0.10, this object may be triaxial. We measured metallicities for a subsample of our data, finding a mean metallicity of [Fe/H] = -1.39 {+-} 0.03 dex and an internal metallicity dispersion of 0.72 {+-} 0.03 dex. We find a radial metallicity gradient with metal-rich stars more centrally concentrated, but do not observe a significant difference in the dynamics of the two metallicity populations. And II is the only known dwarf galaxy to show minor axis rotation, making it a unique system whose existence offers important clues on the processes responsible for the formation of dSphs.

  3. An almost head-on collision as the origin of two off-centre rings in the Andromeda galaxy.

    PubMed

    Block, D L; Bournaud, F; Combes, F; Groess, R; Barmby, P; Ashby, M L N; Fazio, G G; Pahre, M A; Willner, S P

    2006-10-19

    The unusual morphology of the Andromeda galaxy (Messier 31, the closest spiral galaxy to the Milky Way) has long been an enigma. Although regarded for decades as showing little evidence of a violent history, M31 has a well-known outer ring of star formation at a radius of ten kiloparsecs whose centre is offset from the galaxy nucleus. In addition, the outer galaxy disk is warped, as seen at both optical and radio wavelengths. The halo contains numerous loops and ripples. Here we report the presence of a second, inner dust ring with projected dimensions of 1.5 x 1 kiloparsecs and offset by about half a kiloparsec from the centre of the galaxy (based upon an analysis of previously-obtained data). The two rings appear to be density waves propagating in the disk. Numerical simulations indicate that both rings result from a companion galaxy plunging through the centre of the disk of M31. The most likely interloper is M32. Head-on collisions between galaxies are rare, but it appears nonetheless that one took place 210 million years ago in our Local Group of galaxies. PMID:17051212

  4. Ultraviolet Spectra of Normal Spiral Galaxies

    NASA Technical Reports Server (NTRS)

    Kinney, Anne

    1997-01-01

    The data related to this grant on the Ultraviolet Spectra of Normal Spiral Galaxies have been entirely reduced and analyzed. It is incorporated into templates of Spiral galaxies used in the calculation of K corrections towards the understanding of high redshift galaxies. The main paper was published in the Astrophysical Journal, August 1996, Volume 467, page 38. The data was also used in another publication, The Spectral Energy Distribution of Normal Starburst and Active Galaxies, June 1997, preprint series No. 1158. Copies of both have been attached.

  5. THE HERSCHEL EXPLOITATION OF LOCAL GALAXY ANDROMEDA (HELGA). VI. THE DISTRIBUTION AND PROPERTIES OF MOLECULAR CLOUD ASSOCIATIONS IN M31

    SciTech Connect

    Kirk, J. M.; Gear, W. K.; Smith, M. W. L.; Ford, G.; Eales, S. A.; Gomez, H. L.; Fritz, J.; Baes, M.; De Looze, I.; Gentile, G.; Gordon, K.; Verstappen, J.; Viaene, S.; Bendo, G. J.; O'Halloran, B.; Madden, S. C.; Lebouteiller, V.; Boselli, A.; Cooray, A.; and others

    2015-01-01

    In this paper we present a catalog of giant molecular clouds (GMCs) in the Andromeda (M31) galaxy extracted from the Herschel Exploitation of Local Galaxy Andromeda (HELGA) data set. GMCs are identified from the Herschel maps using a hierarchical source extraction algorithm. We present the results of this new catalog and characterize the spatial distribution and spectral energy properties of its clouds based on the radial dust/gas properties found by Smith et al. A total of 326 GMCs in the mass range 10{sup 4}-10{sup 7} M {sub ☉} are identified; their cumulative mass distribution is found to be proportional to M {sup –2.34}, in agreement with earlier studies. The GMCs appear to follow the same correlation of cloud mass to L {sub CO} observed in the Milky Way. However, comparison between this catalog and interferometry studies also shows that the GMCs are substructured below the Herschel resolution limit, suggesting that we are observing associations of GMCs. Following Gordon et al., we study the spatial structure of M31 by splitting the observed structure into a set of spiral arms and offset rings. We fit radii of 10.3 and 15.5 kpc to the two most prominent rings. We then fit a logarithmic spiral with a pitch angle of 8.°9 to the GMCs not associated with either ring. Last, we comment on the effects of deprojection on our results and investigate the effect different models for M31's inclination will have on the projection of an unperturbed spiral arm system.

  6. The Herschel Exploitation of Local Galaxy Andromeda (HELGA). VI. The Distribution and Properties of Molecular Cloud Associations in M31

    NASA Astrophysics Data System (ADS)

    Kirk, J. M.; Gear, W. K.; Fritz, J.; Smith, M. W. L.; Ford, G.; Baes, M.; Bendo, G. J.; De Looze, I.; Eales, S. A.; Gentile, G.; Gomez, H. L.; Gordon, K.; O'Halloran, B.; Madden, S. C.; Roman-Duval, J.; Verstappen, J.; Viaene, S.; Boselli, A.; Cooray, A.; Lebouteiller, V.; Spinoglio, L.

    2015-01-01

    In this paper we present a catalog of giant molecular clouds (GMCs) in the Andromeda (M31) galaxy extracted from the Herschel Exploitation of Local Galaxy Andromeda (HELGA) data set. GMCs are identified from the Herschel maps using a hierarchical source extraction algorithm. We present the results of this new catalog and characterize the spatial distribution and spectral energy properties of its clouds based on the radial dust/gas properties found by Smith et al. A total of 326 GMCs in the mass range 104-107 M ⊙ are identified; their cumulative mass distribution is found to be proportional to M -2.34, in agreement with earlier studies. The GMCs appear to follow the same correlation of cloud mass to L CO observed in the Milky Way. However, comparison between this catalog and interferometry studies also shows that the GMCs are substructured below the Herschel resolution limit, suggesting that we are observing associations of GMCs. Following Gordon et al., we study the spatial structure of M31 by splitting the observed structure into a set of spiral arms and offset rings. We fit radii of 10.3 and 15.5 kpc to the two most prominent rings. We then fit a logarithmic spiral with a pitch angle of 8.°9 to the GMCs not associated with either ring. Last, we comment on the effects of deprojection on our results and investigate the effect different models for M31's inclination will have on the projection of an unperturbed spiral arm system. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  7. Disk dwarf galaxy as the progenitor of the Andromeda giant stream

    NASA Astrophysics Data System (ADS)

    Kirihara, Takanobu; Miki, Yohei; Mori, Masao; Kawaguchi, Toshihiro

    2016-08-01

    We present a study of the morphology of a progenitor galaxy that has been disrupted and formed a giant southern stellar stream in the halo of Andromeda galaxy(M31). N-body simulations of a minor merger of M31 with a dwarf galaxy suggest that the progenitor's rotation plays an important role in the formation of an asymmetric surface brightness distribution of the stream.

  8. The distance to the Andromeda galaxy from eclipsing binaries

    NASA Astrophysics Data System (ADS)

    Vilardell, F.; Ribas, I.; Jordi, C.; Fitzpatrick, E. L.; Guinan, E. F.

    2010-01-01

    The cosmic distance scale largely depends on distance determinations to galaxies of the Local Group. In this sense, the Andromeda galaxy (M 31) is a key rung to better constrain the cosmic distance ladder. A project was started in 1999 to firmly establish a direct and accurate distance to M 31 using eclipsing binaries (EBs). After the determination of the first direct distance to M 31 from EBs, the second direct distance to an EB system is presented: M31V J00443610+4129194. Light and radial velocity curves were obtained and fitted to derive the masses and radii of the components. The acquired spectra were combined and disentangled to determine the temperature of the components. The analysis of the studied EB resulted in a distance determination to M 31 of (m-M)0 = 24.30 ± 0.11 mag. This result, when combined with the previous distance determination to M 31, results in a distance modulus of (m-M)0 = 24.36 ± 0.08 mag (744 ± 33 kpc), fully compatible with other distance determinations to M 31. With an error of only 4%, the obtained value firmly establishes the distance to this important galaxy and represents the fulfillment of the main goal of our project. Based on observations made with the Isaac Newton Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina)Original data are only available in

  9. Unidentified line in x-ray spectra of the Andromeda galaxy and Perseus galaxy cluster.

    PubMed

    Boyarsky, A; Ruchayskiy, O; Iakubovskyi, D; Franse, J

    2014-12-19

    We report a weak line at 3.52±0.02  keV in x-ray spectra of the Andromeda galaxy and the Perseus galaxy cluster observed by the metal-oxide-silicon (MOS) and p-n (PN) CCD cameras of the XMM-Newton telescope. This line is not known as an atomic line in the spectra of galaxies or clusters. It becomes stronger towards the centers of the objects; is stronger for Perseus than for M31; is absent in the spectrum of a deep "blank sky" data set. Although for each object it is hard to exclude that the feature is due to an instrumental effect or an atomic line, it is consistent with the behavior of a dark matter decay line. Future (non-)detections of this line in multiple objects may help to reveal its nature. PMID:25554871

  10. Cinematique et dynamique des galaxies spirales barrees

    NASA Astrophysics Data System (ADS)

    Hernandez, Olivier

    The total mass (luminous and dark) of galaxies is derived from their circular velocities. Spectroscopic Fabry-Perot observations of the ionized gas component of spiral galaxies allow one to derive their kinematics. In the case of purely axisymmetric velocity fields--as in non-active and unbarred spirals galaxies-- the circular velocities can be derived directly. However, the velocity fields of barred galaxies (which constitute two thirds of the spirals) exhibit strong non-circular motions and need a careful analysis to retrieve the circular component. This thesis proposes the necessary steps to recover the axisymmetric component of barred spiral galaxies. The first step was to develop the best instrumentation possible for this work. [Special characters omitted.] , which is the most sensitive photon counting camera ever developed, was coupled to a Fabry-Perot interferometer. The observations of a sample of barred spiral galaxies--the BH a BAR sample--was assembled in order to obtain the most rigourous velocity fields. Then, the Tremaine-Weinberg method, which can determine the bar pattern speed and is usually used with the observations of stellar component, has been tested on the ionised gas and gave satisfactory results. Finally, all the above techniques have been applied to the BH a BAR sample in order to study the key parameters of the galaxies' evolution--bar pattern speeds, multiple stationary waves, resonances etc.--which will allow one to use N-body+SPH simulations to model properly the non-circular motions and determine the true total mass of barred spiral galaxies.

  11. ON THE FRACTION OF BARRED SPIRAL GALAXIES

    SciTech Connect

    Nair, Preethi B.; Abraham, Roberto G. E-mail: abraham@astro.utoronto.c

    2010-05-10

    We investigate the stellar masses of strongly barred spiral galaxies. Our analysis is based on a sample of {approx}14,000 visually classified nearby galaxies given by Nair and Abraham. The fraction of barred spiral galaxies is found to be a strong function of stellar mass and star formation history, with a minimum near the characteristic mass at which bimodality is seen in the stellar populations of galaxies. We also find that bar fractions are very sensitive to the central concentration of galaxies below the transition mass but not above it. This suggests that whatever process is causing the creation of the red and blue sequences is either influencing, or being influenced by, structural changes which manifest themselves in the absence of bars. As a consequence of strong bar fractions being sensitive to the mass range probed, our analysis helps resolve discrepant results on the reported evolution of bar fractions with redshift.

  12. PAndAS' CUBS: Discovery of Two New Dwarf Galaxies in the Surroundings of the Andromeda and Triangulum Galaxies

    NASA Astrophysics Data System (ADS)

    Martin, Nicolas F.; McConnachie, Alan W.; Irwin, Mike; Widrow, Lawrence M.; Ferguson, Annette M. N.; Ibata, Rodrigo A.; Dubinski, John; Babul, Arif; Chapman, Scott; Fardal, Mark; Lewis, Geraint F.; Navarro, Julio; Rich, R. Michael

    2009-11-01

    We present the discovery of two new dwarf galaxies, Andromeda XXI and Andromeda XXII, located in the surroundings of the Andromeda and Triangulum galaxies (M31 and M33). These discoveries stem from the first year data of the Pan-Andromeda Archaeological Survey, a photometric survey of the M31/M33 group conducted with the Megaprime/MegaCam Wide-Field Camera mounted on the Canada-France-Hawaii Telescope. Both satellites appear as spatial overdensities of stars which, when plotted in a color-magnitude diagram, follow metal-poor, [Fe/H] = -1.8, red giant branches at the distance of M31/M33. Andromeda XXI is a moderately bright dwarf galaxy (MV = -9.9 ± 0.6), albeit with low surface brightness, emphasizing again that many relatively luminous M31 satellites still remain to be discovered. It is also a large satellite, with a half-light radius close to 1 kpc, making it the fourth largest Local Group dwarf spheroidal galaxy after the recently discovered Andromeda XIX, Andromeda II, and Sagittarius around the Milky Way, and supports the trend that M31 satellites are larger than their Milky Way counterparts. Andromeda XXII is much fainter (MV = -6.5 ± 0.8) and lies a lot closer in projection to M33 than it does to M31 (42 versus 224 kpc), suggesting that it could be the first Triangulum satellite to be discovered. Although this is a very exciting possibility in the context of a past interaction of M33 with M31 and the fate of its satellite system, a confirmation will have to await a good distance estimate to confirm its physical proximity to M33. Along with the dwarf galaxies found in previous surveys of the M31 surroundings, these two new satellites bring the number of dwarf spheroidal galaxies in this region to 20. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l'Univers of

  13. Smoothing Rotation Curves in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Berrier, Joel C.; Sellwood, Jerry

    2014-05-01

    We present evidence that spiral activity is responsible for the creation of featureless rotation curves. We examine a variety of simulations of disk galaxies beginning in equilibrium and allow them to evolve while adding particles in annuli to the hot disk using a variety of rules. Two unstable spiral modes develop when this new material forms a ridge-like feature in the surface density profile of the disk. The extra material is redistributed radially by the spiral activity, and the associated angular momentum changes remove more particles from the ridge than are added to it. This process eventually removes the density feature from the galaxy and creates a locally flat rotation curve. We argue that the lack of a feature when transitioning from disk to halo dominance in the rotation curves of disk galaxies, the so called ``disk-halo conspiracy'', could also be accounted for by this mechanism.

  14. Planck intermediate results. XXV. The Andromeda galaxy as seen by Planck

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Battye, R.; Benabed, K.; Bendo, G. J.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chary, R.-R.; Chen, X.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Israel, F. P.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Madden, S.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Mendes, L.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Partridge, B.; Pasian, F.; Pearson, T. J.; Peel, M.; Perdereau, O.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Sudiwala, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Watson, R.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

    2015-10-01

    The Andromeda galaxy (M 31) is one of a few galaxies that has sufficient angular size on the sky to be resolved by the Planck satellite. Planck has detected M 31 in all of its frequency bands, and has mapped out the dust emission with the High Frequency Instrument, clearly resolving multiple spiralarms and sub-features. We examine the morphology of this long-wavelength dust emission as seen by Planck, including a study of its outermost spiral arms, and investigate the dust heating mechanism across M 31. We find that dust dominating the longer wavelength emission (≳0.3 mm) is heated by the diffuse stellar population (as traced by 3.6 μm emission), with the dust dominating the shorter wavelength emission heated by a mix of the old stellar population and star-forming regions (as traced by 24 μm emission). We also fit spectral energy distributions for individual 5' pixels and quantify the dust properties across the galaxy, taking into account these different heating mechanisms, finding that there is a linear decrease in temperature with galactocentric distance for dust heated by the old stellar population, as would be expected, with temperatures ranging from around 22 K in the nucleus to 14 K outside of the 10 kpc ring. Finally, we measure the integrated spectrum of the whole galaxy, which we find to be well-fitted with a global dust temperature of (18.2 ± 1.0) K with a spectral index of 1.62 ± 0.11 (assuming a single modified blackbody), and a significant amount of free-free emission at intermediate frequencies of 20-60 GHz, which corresponds to a star formation rate of around 0.12 M⊙ yr-1. We find a 2.3σ detection of the presence of spinning dust emission, with a 30 GHz amplitude of 0.7 ± 0.3 Jy, which is in line with expectations from our Galaxy.

  15. STAR CLUSTERS IN PSEUDOBULGES OF SPIRAL GALAXIES

    SciTech Connect

    Di Nino, Daiana; Trenti, Michele; Stiavelli, Massimo; Carollo, C. Marcella; Scarlata, Claudia; Wyse, Rosemary F. G.

    2009-11-15

    We present a study of the properties of the star-cluster systems around pseudobulges of late-type spiral galaxies using a sample of 11 galaxies with distances from 17 Mpc to 37 Mpc. Star clusters are identified from multiband Hubble Space Telescope ACS and WFPC2 imaging data by combining detections in three bands (F435W and F814W with ACS and F606W with WFPC2). The photometric data are then compared to population synthesis models to infer the masses and ages of the star clusters. Photometric errors and completeness are estimated by means of artificial source Monte Carlo simulations. Dust extinction is estimated by considering F160W NICMOS observations of the central regions of the galaxies, augmenting our wavelength coverage. In all galaxies we identify star clusters with a wide range of ages, from young (age {approx}< 8 Myr) blue clusters, with typical mass of 10{sup 3} M {sub sun} to older (age >100-250 Myr), more massive, red clusters. Some of the latter might likely evolve into objects similar to the Milky Way's globular clusters. We compute the specific frequencies for the older clusters with respect to the galaxy and bulge luminosities. Specific frequencies relative to the galaxy light appear consistent with the globular cluster specific frequencies of early-type spirals. We compare the specific frequencies relative to the bulge light with the globular cluster specific frequencies of dwarf galaxies, which have a surface brightness profile that is similar to that of the pseudobulges in our sample. The specific frequencies we derive for our sample galaxies are higher than those of the dwarf galaxies, supporting an evolutionary scenario in which some of the dwarf galaxies might be the remnants of harassed late-type spiral galaxies that hosted a pseudobulge.

  16. CCD photometry of Andromeda IV - Dwarf irregular galaxy or M31 open cluster?

    NASA Technical Reports Server (NTRS)

    Jones, Joseph H.

    1993-01-01

    CCD photometry of Andromeda IV was obtained during discretionary time in August of 1989 at the Canada-France-Hawaii Telescope on Mauna Kea and the data were reduced at CFHT during the summer of 1991. And IV has been catalogued both as a dwarf galaxy and as an open star cluster in M31. The color-magnitude diagrams presented indicate that this object has a young population of stars with a narrow age range, consistent with the characteristics of an open star cluster or stellar association. A radial velocity measurement taken from the literature and analyzed with respect to the rotation curve of M31 indicates this object resides in the disk of the Andromeda Galaxy, strengthening the conclusion that it is indeed a very large open star cluster or a densely populated stellar association rather than a dwarf irregular galaxy.

  17. Stable State Simulations of Andromeda Dwarf Spheroidal Satellite Galaxies Using MOND

    NASA Astrophysics Data System (ADS)

    Walentosky, Matthew; Blankartz, Benjamin; Alexander, Stephen; Messinger, Justin; Staron, Alex

    2016-01-01

    We present the results of numerical simulations of the stable state condition of several dwarf spheroidal galaxies orbiting the Andromeda galaxy. Using Modified Newtonian Dynamics, we calculate the motion of ten thousand stars in a spherically symmetric Hernquist potential to obtain both the line of sight bulk velocity dispersion and the dispersion profile, i.e. the velocity dispersion as a function of distance from the galactic center. Our results for the bulk dispersion show excellent agreement with observed values and previously published theoretical results and provide reliable estimates of the mass to luminosity ratio. We predict relatively flat radial dispersion profiles for several of the Andromeda dwarf spheroidal galaxies that are similar to those measured for the Milky Way dwarf spheroidals .

  18. THE LUMINOSITY PROFILE AND STRUCTURAL PARAMETERS OF THE ANDROMEDA GALAXY

    SciTech Connect

    Courteau, Stephane; Widrow, Lawrence M.; McDonald, Michael; Guhathakurta, Puragra; Zhu Yucong

    2011-09-20

    We have constructed an extended composite luminosity profile for the Andromeda galaxy, M31, and have decomposed it into three basic luminous structural components: a bulge, a disk, and a halo. The dust-free Spitzer/Infrared Array Camera (IRAC) imaging and extended spatial coverage of ground-based optical imaging and deep star counts allow us to map M31's structure from its center to 22 kpc along the major axis. We apply, and address the limitations of, different decomposition methods for the one-dimensional luminosity profiles and two-dimensional images. These methods include nonlinear least-squares and Bayesian Monte Carlo Markov chain analyses. The basic photometric model for M31 has a Sersic bulge with shape index n {approx_equal} 2.2 {+-} .3 and effective radius R{sub e} = 1.0 {+-} 0.2 kpc, and a dust-free exponential disk of scale length R{sub d} = 5.3 {+-} .5 kpc; the parameter errors reflect the range between different decomposition methods. Despite model covariances, the convergence of solutions based on different methods and current data suggests a stable set of structural parameters. The ellipticities ({epsilon} = 1 - b/a) of the bulge and the disk from the IRAC image are 0.37 {+-} 0.03 and 0.73 {+-} 0.03, respectively. The bulge parameter n is rather insensitive to bandpass effects and its value (2.2) suggests a first rapid formation via mergers followed by secular growth from the disk. The M31 halo has a two-dimensional power-law index {approx_equal} - 2.5 {+-} 0.2 (or -3.5 in three-dimensional), comparable to that of the Milky Way. We find that the M31 bulge light is mostly dominant over the range R{sub min} {approx}< 1.2 kpc. The disk takes over in the range 1.2 kpc {approx}< R{sub min} {approx}< 9 kpc, whereas the halo dominates at R{sub min} {approx}> 9 kpc. The stellar nucleus, bulge, disk, and halo components each contribute roughly 0.05%, 23%, 73%, and 4% of the total light of M31 out to 200 kpc along the minor axis. Nominal errors for the

  19. COMPARING THE OBSERVABLE PROPERTIES OF DWARF GALAXIES ON AND OFF THE ANDROMEDA PLANE

    SciTech Connect

    Collins, Michelle L. M.; Martin, Nicolas F.; Rich, R. M.; Ibata, Rodrigo A.; Chapman, Scott C.; McConnachie, Alan W.; Ferguson, Annette M.; Irwin, Michael J.; Lewis, Geraint F.

    2015-01-20

    The thin, extended planes of satellite galaxies detected around both the Milky Way and Andromeda are not a natural prediction of the Λ-cold dark matter paradigm. Galaxies in these distinct planes may have formed and evolved in a different way (e.g., tidally) from their off-plane neighbors. If this were the case, one would expect the on- and off-plane dwarf galaxies in Andromeda to have experienced different evolutionary histories, which should be reflected by the chemistries, dynamics, and star formation histories of the two populations. In this work, we present new, robust kinematic observations for two on-plane M31 dwarf spheroidal galaxies (And XVI and XVII) and compile and compare all available observational metrics for the on- and off-plane dwarfs to search for a signal that would corroborate such a hypothesis. We find that, barring their spatial alignment, the on- and off-plane Andromeda dwarf galaxies are indistinguishable from one another, arguing against vastly different formative and evolutionary histories for these two populations.

  20. Comparing the Observable Properties of Dwarf Galaxies on and off the Andromeda Plane

    NASA Astrophysics Data System (ADS)

    Collins, Michelle L. M.; Martin, Nicolas F.; Rich, R. M.; Ibata, Rodrigo A.; Chapman, Scott C.; McConnachie, Alan W.; Ferguson, Annette M.; Irwin, Michael J.; Lewis, Geraint F.

    2015-01-01

    The thin, extended planes of satellite galaxies detected around both the Milky Way and Andromeda are not a natural prediction of the Λ-cold dark matter paradigm. Galaxies in these distinct planes may have formed and evolved in a different way (e.g., tidally) from their off-plane neighbors. If this were the case, one would expect the on- and off-plane dwarf galaxies in Andromeda to have experienced different evolutionary histories, which should be reflected by the chemistries, dynamics, and star formation histories of the two populations. In this work, we present new, robust kinematic observations for two on-plane M31 dwarf spheroidal galaxies (And XVI and XVII) and compile and compare all available observational metrics for the on- and off-plane dwarfs to search for a signal that would corroborate such a hypothesis. We find that, barring their spatial alignment, the on- and off-plane Andromeda dwarf galaxies are indistinguishable from one another, arguing against vastly different formative and evolutionary histories for these two populations.

  1. RR Lyrae variables in the Andromeda group galaxies

    NASA Astrophysics Data System (ADS)

    Yang, Soung-Chul

    2011-08-01

    We present the results of an extensive survey of RR Lyrae stars in the companion galaxies (M33, NGC 147, And XI and And XIII) around the Andromeda galaxy (M31). From images taken with the Advanced Camera for Surveys (ACS) Wide Field Channel (WFC) on-board the Hubble Space Telescope (HST) through two passbands (F606W and F814W), we have identified and characterized a total of 119 RR Lyrae variables (96 RRab (RR0) and 23 RRc(RR1)) in M33. Using the properties of 83 RR Lyrae stars (65 RRab and 18 RRc) in the innermost ACS field (hereafter DISK2), we find mean periods of < Pab > = 0.553 +/- 0.008 (error1) +/- 0.05 (error2) and < Pc > = 0.325 +/- 0.008 (error1) +/- 0.05 (error2), where the 'error1' value represents the standard error of the mean and the 'error2' value is based on the error of an individual RRL period calculated from our synthetic light curve simulations. The distribution of RRab periods and the frequency of RRc stars (Nc = nc/nabc = 0.22) strongly suggest that these RR Lyraes follow the general characteristics of those in Oosterhoff type I Galactic globular clusters. The metallicities of 65 individual RRab stars are calculated from the period-amplitude-metallicity relationship, yielding a mean metallicity of < [Fe/H] > = -1.48 +/- 0.05 dex, where the uncertainty is the standard error of the mean. The VI minimum-light colors of the RRab stars are used to calculate a mean line-of-sight reddening toward the DISK2 field of < E(V -- I) > = 0.175. By adopting this line-of-sight reddening and using a relation between RR Lyrae luminosity and metallicity (MV = 0.23[ Fe/H] + 0.93), we estimate a mean distance modulus of < ( m -- M)0 > = 24.52 +/- 0.11 for M33, where the error is the quadratic sum of the uncertainties in the absolute and dereddened V magnitudes of the RRLs. We used both Thuan-Gunn g-band ground-based photometry from the literature and HST Wide Field Planetary Camera 2 (WFPC2) archival data in the F555W and F814W passbands to investigate the

  2. Dark and visible matter in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Persic, M.; Salucci, P.

    1988-01-01

    Rotation-curve profiles are used to determine the dark-to-luminous mass ratio within the disk size for 43 spiral galaxies. It is noted that faint galaxies are halo-dominated and that bright galaxies are disk-dominated in the disk regions. The luminosity sequence is shown to be a dark-to-luminous sequence. By removing the dark-matter contribution from the velocity at the disk edge, the dispersion affecting the luminosity-kinematics relation is found to decrease in comparison with the conventional Tully-Fisher correlation.

  3. Spiral Galaxies in MKW/AWM Clusters

    NASA Astrophysics Data System (ADS)

    Williams, Barbara A.

    1997-03-01

    Observations have been made of the neutral hydrogen content of more than 170 galaxies within MKW 4, MKW 7, MKW 8, MKW 9, MKW 11, AWM 1, AWM 3, AWM 4, and AWM 5. This sample of nine clusters is representative of the general class of poor clusters identified by MKW and AWM in that they all contain D-- or cD--like dominant galaxies at their dynamical centers. We examine the neutral hydrogen (HI) content of the spiral members in these systems as a function of the local and global properties of the cluster, i.e., galaxy density, x-ray intra cluster gas pressure, x-ray and optical luminosities, and compare our findings with the HI properties of similar galaxies in rich clusters and loose groups of galaxies.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  5. MAGNIFICENT DETAILS IN A DUSTY SPIRAL GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In 1995, the majestic spiral galaxy NGC 4414 was imaged by the Hubble Space Telescope as part of the HST Key Project on the Extragalactic Distance Scale. An international team of astronomers, led by Dr. Wendy Freedman of the Observatories of the Carnegie Institution of Washington, observed this galaxy on 13 different occasions over the course of two months. Images were obtained with Hubble's Wide Field Planetary Camera 2 (WFPC2) through three different color filters. Based on their discovery and careful brightness measurements of variable stars in NGC 4414, the Key Project astronomers were able to make an accurate determination of the distance to the galaxy. The resulting distance to NGC 4414, 19.1 megaparsecs or about 60 million light-years, along with similarly determined distances to other nearby galaxies, contributes to astronomers' overall knowledge of the rate of expansion of the universe. The Hubble constant (H0) is the ratio of how fast galaxies are moving away from us to their distance from us. This astronomical value is used to determine distances, sizes, and the intrinsic luminosities for many objects in our universe, and the age of the universe itself. Due to the large size of the galaxy compared to the WFPC2 detectors, only half of the galaxy observed was visible in the datasets collected by the Key Project astronomers in 1995. In 1999, the Hubble Heritage Team revisited NGC 4414 and completed its portrait by observing the other half with the same filters as were used in 1995. The end result is a stunning full-color look at the entire dusty spiral galaxy. The new Hubble picture shows that the central regions of this galaxy, as is typical of most spirals, contain primarily older, yellow and red stars. The outer spiral arms are considerably bluer due to ongoing formation of young, blue stars, the brightest of which can be seen individually at the high resolution provided by the Hubble camera. The arms are also very rich in clouds of interstellar dust

  6. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Krause, Marita

    2015-03-01

    The magnetic field structure in edge-on galaxies observed so far shows a plane-parallel magnetic field component in the disk of the galaxy and an X-shaped field in its halo. The plane-parallel field is thought to be the projected axisymmetric (ASS) disk field as observed in face-on galaxies. Some galaxies addionionally exhibit strong vertical magnetic fields in the halo right above and below the central region of the disk. The mean-field dynamo theory in the disk cannot explain these observed fields without the action of a wind, which also probably plays an important role to keep the vertical scale heights constant in galaxies of different Hubble types and star formation activities, as has been observed in the radio continuum: At λ6 cm the vertical scale heights of the thin disk and the thick disk/halo in a sample of five edge-on galaxies are similar with a mean value of 300 +/- 50 pc for the thin disk and 1.8 +/- 0.2 kpc for the thick disk (a table and references are given in Krause 2011) with our sample including the brightest halo observed so far, NGC 253, with strong star formation, as well as one of the weakest halos, NGC 4565, with weak star formation. If synchrotron emission is the dominant loss process of the relativistic electrons the outer shape of the radio emission should be dumbbell-like as has been observed in several edge-on galaxies like e.g. NGC 253 (Heesen et al. 2009) and NGC 4565. As the synchrotron lifetime t syn at a single frequency is proportional to the total magnetic field strength B t -1.5, a cosmic ray bulk speed (velocity of a galactic wind) can be defined as v CR = h CR /t syn = 2 h z /t syn , where h CR and h z are the scale heights of the cosmic rays and the observed radio emission at this freqnency. Similar observed radio scale heights imply a self regulation mechanism between the galactic wind velocity, the total magnetic field strength and the star formation rate SFR in the disk: v CR ~ B t 1.5 ~ SFR ~ 0.5 (Niklas & Beck 1997).

  7. Exploring spiral galaxy potentials with hydrodynamical simulations

    NASA Astrophysics Data System (ADS)

    Slyz, Adrianne D.; Kranz, Thilo; Rix, Hans-Walter

    2003-12-01

    We study how well the complex gas velocity fields induced by massive spiral arms are modelled by the hydrodynamical simulations that we used recently to constrain the dark matter fraction in nearby spiral galaxies. More specifically, we explore the dependence of the positions and amplitudes of features in the gas flow on the temperature of the interstellar medium (assumed to behave as a one-component isothermal fluid), the non-axisymmetric disc contribution to the galactic potential, the pattern speed Ωp, and finally the numerical resolution of the simulation. We argue that, after constraining the pattern speed reasonably well by matching the simulations to the observed spiral arm morphology, the amplitude of the non-axisymmetric perturbation (the disc fraction) is left as the primary parameter determining the gas dynamics. However, owing to the sensitivity of the positions of the shocks to modelling parameters, one has to be cautious when quantitatively comparing the simulations to observations. In particular, we show that a global least-squares analysis is not the optimal method for distinguishing different models, as it tends to slightly favour low disc fraction models. Nevertheless, we conclude that, given observational data of reasonably high spatial resolution and an accurate shock-resolving hydro-code, this method tightly constrains the dark matter content within spiral galaxies. We further argue that, even if the perturbations induced by spiral arms are weaker than those of strong bars, they are better suited for this kind of analysis because the spiral arms extend to larger radii where effects like inflows due to numerical viscosity and morphological dependence on gas sound speed are less of a concern than they are in the centres of discs.

  8. Variable Stars in a Distant Spiral Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    A NASA Hubble Space Telescope (HST) view of the magnificent spiral galaxy NGC 4603, the most distant galaxy in which a special class of pulsating stars called Cepheid variables have been found. It is associated with the Centaurus cluster, one of the most massive assemblages of galaxies in the nearby universe. The Local Group of galaxies, of which the Milky Way is a member, is moving in the direction of Centaurus at a speed of more than a million miles an hour under the influence of the gravitational pull of the matter in that direction. Clusters of young bright blue stars highlight the galaxy's spiral arms. In contrast, red giant stars in the process of dying are also found. Only the very brightest stars in NGC 4603 can be seen individually, even with the unmatched ability of the Hubble Space Telescope to obtain detailed images of distant objects. Much of the diffuse glow comes from fainter stars that cannot be individually distinguished by Hubble. The reddish filaments are regions where clouds of dust obscure blue light from the stars behind them. This galaxy was observed by a team affiliated with the HST Key Project on the Extragalactic Distance Scale. Because NGC 4603 is much farther away than the other galaxies studied with Hubble by the Key Project team, 108 million light-years, its stars appear very faint from the Earth, and so accurately measuring their brightness, as is required for distinguishing the characteristic variations of Cepheids, is extremely difficult. Determining the distance to the galaxy required an unprecedented statistical analysis based on extensive computer simulations.

  9. STAR FORMATION IN TWO LUMINOUS SPIRAL GALAXIES

    SciTech Connect

    Hunter, Deidre A.; Ashburn, Allison; Wright, Teresa; Elmegreen, Bruce G.; Rubin, Vera C.; Józsa, Gyula I. G.; Struve, Christian

    2013-10-01

    We examined star formation in two very luminous (M{sub V} = –22 to –23) Sc-type spiral galaxies, NGC 801 and UGC 2885, using ultra-deep Hα images. We combine these Hα images with UBV and Two-Micron All-Sky Survey JHK images and H I maps to explore the star formation characteristics of disk galaxies at high luminosity. Hα traces star formation in these galaxies to 4-6 disk scale lengths, but the lack of detection of Hα further out is likely due to the loss of Lyman continuum photons. Considering gravitational instabilities alone, we find that the gas and stars in the outer regions are marginally stable in an average sense, but considering dissipative gas and radial and azimuthal forcing, the outer regions are marginally unstable to forming spiral arms. Star formation is taking place in spiral arms, which are regions of locally higher gas densities. Furthermore, we have traced smooth exponential stellar disks over four magnitudes in V-band surface brightness and 4-6 disk scale lengths, in spite of a highly variable gravitational instability parameter. Thus, gravitational instability thresholds do not seem relevant to the stellar disk. One possibility for creating an exponential disk is that the molecular cloud densities and star formation rates have exponential profiles and this fact forces the stellar disk to build up such a profile. Another possibility is that the stellar disk is continuously adjusted to an exponential shape regardless of the star formation profile, for example, through global dynamical processes that scatter stars. However, such scattering processes are only known to operate in spiral systems, in which case they cannot explain the same dilemma of smooth exponential disks observed in dwarf irregular galaxies.

  10. Interferometric observations of molecular clouds in the Andromeda galaxy (M31)

    NASA Astrophysics Data System (ADS)

    Muller, S.

    The study of the molecular component of the ISM in galaxies is crucial to our understanding of their structure and dynamics. Carbon monoxyde remains the best tracer of this cold molecular matter. A complete survey of the Andromeda galaxy in CO(1-0) at 115 GHz has now been completed with the IRAM 30m telescope. In addition, high--angular resolution, high--sensitivity interferometric observations of selected fields have been obtained with the Plateau de Bure Interferometer. The dynamical mass of molecular complexes can then be estimated with the virial theorem, and compared to the mass derived from the CO luminosity using the magic conversion factor X = NH2 / WCO.

  11. Galactic Building Blocks Seen Swarming Around Andromeda

    NASA Astrophysics Data System (ADS)

    2004-02-01

    Green Bank, WV - A team of astronomers using the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) has made the first conclusive detection of what appear to be the leftover building blocks of galaxy formation -- neutral hydrogen clouds -- swarming around the Andromeda Galaxy, the nearest large spiral galaxy to the Milky Way. This discovery may help scientists understand the structure and evolution of the Milky Way and all spiral galaxies. It also may help explain why certain young stars in mature galaxies are surprisingly bereft of the heavy elements that their contemporaries contain. Andromeda Galaxy This image depicts several long-sought galactic "building blocks" in orbit of the Andromeda Galaxy (M31). The newfound hydrogen clouds are depicted in a shade of orange (GBT), while gas that comprises the massive hydrogen disk of Andromeda is shown at high-resolution in blue (Westerbork Sythesis Radio Telescope). CREDIT: NRAO/AUI/NSF, WSRT (Click on Image for Larger Version) "Giant galaxies, like Andromeda and our own Milky Way, are thought to form through repeated mergers with smaller galaxies and through the accretion of vast numbers of even lower mass 'clouds' -- dark objects that lack stars and even are too small to call galaxies," said David A. Thilker of the Johns Hopkins University in Baltimore, Maryland. "Theoretical studies predict that this process of galactic growth continues today, but astronomers have been unable to detect the expected low mass 'building blocks' falling into nearby galaxies, until now." Thilker's research is published in the Astrophysical Journal Letters. Other contributors include: Robert Braun of the Netherlands Foundation for Research in Astronomy; Rene A.M. Walterbos of New Mexico State University; Edvige Corbelli of the Osservatorio Astrofisico di Arcetri in Italy; Felix J. Lockman and Ronald Maddalena of the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia; and Edward Murphy of the

  12. Internal Extinction in Spiral Galaxies. Inclination Dependence

    NASA Astrophysics Data System (ADS)

    Magris, G. C.; Bruzual, G. A.

    1987-05-01

    . Kent (1986) finds that the surface brightness profiles (r) of spiral galaxies have a weak dependence, if any, on the inclination e with respect to the line of sight. This author also finds a correlation between the MIL ratio and the inclination of a galaxy. The lack of dependence of (r) in , = cos 8 indicates that the disk of these galaxies is optically thick ( .>l), due to the presence of dust grains. For an optically thick system o(r) a + 2.5 log . The cosecant law : 1.086 (Holmberg, 1975) does not explain the observed behaviour of a(r) with . 8ru'ual, Magris and Calvet (1986) solved the radiative transfer equation for a mixture of stars and dispersive dust grains distributed homogeneously in a plane parallel configuration, taking into account the wavelenght dependence of the albedo and , as well as the redistribution in angle of photons scattered by dust grains. The transfer equation is solved for the dimensionless intensity ?( , ) I( , )/I*, where 1* is the intensity emerging from the dust free configuration. The solution, CA -2.5 log (r..=0, ) , includes the correction to the galaxy magnitude due to the excess number 0+ stellar sources along the line o+ sigth (cc -i) with respect to the =I case (face on galaxy). For optically thick systems, does not depend on . The luminosity of a disk galaxy observed with inclination ,q 1 given in our model by L cc , from which log(M/L) = const + (.4 8.N( )'. with G.N . ) = -2.5 log( ). The constant is determined from the mass- luminosity. ratio of a dust free system. In terms of the correction (3(N) we can explain Kent's observations with values of between .3 and 4. These values are consistent with the observation of . -independent surface brightness profiles mentioned above. From this analysis we conclude that the correction terms of Bruzual, Magris and Calvet (1986), which take into account the dispersive properties of interstellar dust, can explain the behaviour of ar) and MIL with galaxy inclination. These correction

  13. Mesoscale Magnetic Structures in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Shukurov, Anvar

    Virtually all spiral galaxies host magnetic fields ordered at scales comparable to the galactic size (Beck et al., 1996; Beck, 2000, 2001). Observations of polarized radio emission at improved resolution and sensitivity have revealed details of the global magnetic structures that can shed new light on the problem of their origin. Reversals of the regular magnetic field along radius and/or azimuth and magnetic arms are such features, whose scale exceeds significantly the correlation scale of interstellar turbulence but remains smaller than the overall galactic dimension. Despite a few decades of debate, there remains doubt as to what features of the observed field could have been inherited from the pre-galactic past, and which have been formed and maintained more recently in a relatively mature galaxy. In what follows, we briefly review the current understanding of the origin of the mesoscale magnetic structures and their implications for the origin of galactic magnetic fields.

  14. Chemical evolution in spiral and irregular galaxies

    NASA Technical Reports Server (NTRS)

    Torres-Peimbert, S.

    1986-01-01

    A brief review of models of chemical evolution of the interstellar medium in our galaxy and other galaxies is presented. These models predict the time variation and radial dependence of chemical composition in the gas as function of the input parameters; initial mass function, stellar birth rate, chemical composition of mass lost by stars during their evolution (yields), and the existence of large scale mass flows, like infall from the halo, outflow to the intergalactic medium or radial flows within a galaxy. At present there is a considerable wealth of observational data on the composition of HII regions in spiral and irregular galaxies to constrain the models. Comparisons are made between theory and the observed physical conditions. In particular, studies of helium, carbon, nitrogen and oxygen abundances are reviewed. In many molecular clouds the information we have on the amount of H2 is derived from the observed CO column density, and a standard CO/H2 ratio derived for the solar neighborhood. Chemical evolution models and the observed variations in O/H and N/O values, point out the need to include these results in a CO/H2 relation that should be, at least, a function of the O/H ratio. This aspect is also discussed.

  15. Studying the Structure and Dynamics of the Subcomponents of the Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Lin, Jimmy; Mukherjee, Arin; Wang, Margaret; Guhathakurta, Puragra; Fardal, Mark A.; Sohn, S. Tony; Cunningham, Emily; Deason, Alis J.; Toloba, Elisa; Keoliya, Shruti; Van Der Marel, Roeland P.; Rockosi, Constance M.; HSTPROMO, HALO7D, SPLASH

    2016-01-01

    The Andromeda (M31) galaxy is the only large galaxy besides the Milky Way (MW) that is nearby enough to be dissected star by star, making it an excellent candidate for studying galaxy formation and evolution. A galaxy's evolutionary path is determined by factors such as its dark matter distribution, gas content, energy injection by supernovae and active nucleus, merger history, etc.. To constrain these physical processes, we studied the structure and dynamics M31 using very accurate proper motion (PM) measurements and exquisite photometry from three Hubble Space Telescope fields in the direction of the M31 galaxy. In order to exclude the MW contaminants from our data set, we used PM and photometric data to cuts define our M31 sample. We used this sample to analyze the motion of the subcomponents of M31 in the context of the state-of-the-art M31 model presented in van der Marel et al. 2012. We observed the relative PMs of three M31 subcomponents to gain unprecedented insight into the internal kinematics of M31. The PM differences we found were compared to a M31 model and provide input for refining the model. Our results serve as constraints for any dynamical formation model of the subcomponents of M31 and for any other large galaxy, allowing for better study and understanding of the dark matter contents and formation of the M31 galaxy.

  16. Andromeda IV, a solitary gas-rich dwarf galaxy

    NASA Astrophysics Data System (ADS)

    Karachentsev, I. D.; Chengalur, J. N.; Tully, R. B.; Makarova, L. N.; Sharina, M. E.; Begum, A.; Rizzi, L.

    2016-03-01

    Observations are presented of the isolated dwarf irregular galaxy And IV made with the Hubble Space Telescope Advanced Camera for Surveys and the Giant Metrewave Radio Telescope in the 21 cm H I line. We determine the galaxy distance of 7.17{±}0.31 Mpc using the Tip of Red Giant Branch method. The galaxy has a total blue absolute magnitude of -12.81 mag, linear Holmberg diameter of 1.88 kpc, and an H I-disk extending to 8.4 times the optical Holmberg radius. The H I mass-to-blue luminosity ratio for And IV amounts 12.9M⊙/L⊙. From the GMRT data we derive the rotation curve for the H I and fit it with different mass models. We find that the data are significantly better fit with an iso-thermal dark matter halo, than by an NFW halo. We also find that MOND rotation curve provides a very poor fit to the data. The fact that the iso-thermal dark matter halo provides the best fit to the data supports models in which star formation feedback results in the formation of a dark matter core in dwarf galaxies. The total mass-to-blue luminosity ratio of 162M⊙/L⊙ makes And IV among the darkest dIrr galaxies known. However, its baryonic-to-dark mass ratio (M_gas+M*)/M_T = 0.11 is close to the average cosmic baryon fraction of 0.15.

  17. Puzzling outer-density profile of the dark matter halo in the Andromeda galaxy

    NASA Astrophysics Data System (ADS)

    Kirihara, Takanobu; Miki, Yohei; Mori, Masao

    2014-12-01

    The cold dark matter (CDM) cosmology, which is the standard theory of the structure formation in the universe, predicts that the outer density profile of dark matter halos decreases with the cube of distance from the center. However, so far not much effort has been expended in examining this hypothesis. In the halo of the Andromeda galaxy (M 31), large-scale stellar structures detected by the recent observations provide a potentially suitable window to investigate the mass-density distribution of the dark matter halo. We explore the density structure of the dark matter halo in M 31 using an N-body simulation of the interaction between an accreting satellite galaxy and M 31. To reproduce the Andromeda Giant Southern Stream and the stellar shells at the east and west sides of M 31, we find the sufficient condition for the power-law index α of the outer density distribution of the dark matter halo. The best-fitting parameter is α = -3.7, which is steeper than the CDM prediction.

  18. Wolf-Rayet stars in the Andromeda Galaxy

    SciTech Connect

    Moffat, A.F.J.; Shara, M.M.

    1987-09-01

    A survey of M31 for strong-line Wolf-Rayet (W-R) stars has been completed, confirming the trends found previously, that (1) M31 is at present about an order of magnitude less active in star formation than the Galaxy, as reflected in the total number of W-R stars, assumed to have evolved from massive progenitors; (2) the number ratio of late to early WC stars, WCL/WCE, varies systematically with galactocentric radius as in the Galaxy, possibly a consequence of the metallicity gradient in the disk; and (3) most W-R stars lie in the prominent ring of active star formation at R = 7-12 kpc from the center of M31. 19 references.

  19. A Grazing Encounter Between Two Spiral Galaxies

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The larger and more massive galaxy is cataloged as NGC 2207 (on the left in the Hubble Heritage image), and the smaller one on the right is IC 2163. Strong tidal forces from NGC 2207 have distorted the shape of IC 2163, flinging out stars and gas into long streamers stretching out a hundred thousand light-years toward the right-hand edge of the image. Computer simulations, carried out by a team led by Bruce and Debra Elmegreen, demonstrate the leisurely timescale over which galactic collisions occur. In addition to the Hubble images, measurements made with the National Science Foundation's Very Large Array Radio Telescope in New Mexico reveal the motions of the galaxies and aid the reconstruction of the collision. The calculations indicate that IC 2163 is swinging past NGC 2207 in a counterclockwise direction, having made its closest approach 40 million years ago. However, IC 2163 does not have sufficient energy to escape from the gravitational pull of NGC 2207, and is destined to be pulled back and swing past the larger galaxy again in the future. The high resolution of the Hubble telescope image reveals dust lanes in the spiral arms of NGC 2207, clearly silhouetted against IC 2163, which is in the background. Hubble also reveals a series of parallel dust filaments extending like fine brush strokes along the tidally stretched material on the right-hand side. The large concentrations of gas and dust in both galaxies may well erupt into regions of active star formation in the near future. Trapped in their mutual orbit around each other, these two galaxies will continue to distort and disrupt each other. Eventually, billions of years from now, they will merge into a single, more massive galaxy. It is believed that many present-day galaxies, including the Milky Way, were assembled from a similar process of coalescence of smaller galaxies occurring over billions of years. This image was created from 3 separate pointings of Hubble. The Wide Field Planetary Camera 2 data

  20. Constraining sterile neutrino warm dark matter with Chandra observations of the Andromeda galaxy

    SciTech Connect

    Watson, Casey R.; Polley, Nicholas K.; Li, Zhiyuan E-mail: zyli@astro.ucla.edu

    2012-03-01

    We use the Chandra unresolved X-ray emission spectrum from a 12'–28' (2.8–6.4 kpc) annular region of the Andromeda galaxy to constrain the radiative decay of sterile neutrino warm dark matter. By excising the most baryon-dominated, central 2.8 kpc of the galaxy, we reduce the uncertainties in our estimate of the dark matter mass within the field of view and improve the signal-to-noise ratio of prospective sterile neutrino decay signatures relative to hot gas and unresolved stellar emission. Our findings impose the most stringent limit on the sterile neutrino mass to date in the context of the Dodelson-Widrow model, m{sub s} < 2.2 keV (95% C.L.). Our results also constrain alternative sterile neutrino production scenarios at very small active-sterile neutrino mixing angles.

  1. A comparison of the distribution of satellite galaxies around Andromeda and the results of ΛCDM simulations

    NASA Astrophysics Data System (ADS)

    Bahl, H.; Baumgardt, H.

    2014-03-01

    Ibata et al. recently reported the existence of a vast thin plane of dwarf galaxies (VTPD) orbiting around Andromeda. We investigate whether such a configuration can be reproduced within the standard cosmological framework and search for similar planes of corotating satellite galaxies around Andromeda-like host haloes in the data from the Millennium II simulation combined with a semi-analytic galaxy formation model. We apply a baryonic mass cut of 2.8 × 104 M⊙ for the satellite haloes and restrict the data to a Pan-Andromeda Archaeological Survey-like field. If we include the so-called orphan galaxies in our analysis, we find that planes with an rms lower than the VTPD are common in Millennium II. This is partially due to the strong radially concentrated distribution of orphan galaxies. Excluding part of the orphan galaxies brings the radial distributions of Millennium II satellites into better agreement with the satellite distribution of Andromeda while still producing a significant fraction of planes with a lower rms than the VTPD. We also find haloes in Millennium II with an equal or higher number of corotating satellites than the VTPD. This demonstrates that the VTPD is not in conflict with the standard cosmological framework, although a definite answer of this question might require higher resolution cosmological simulations that do not have to consider orphan galaxies. Our results finally show that satellite planes in Millennium II are not stable structures; hence, the VTPD might only be a statistical fluctuation of an underlying more spherical galaxy distribution.

  2. Stellar kinematics using a third integral of motion: method and application on the Andromeda galaxy

    NASA Astrophysics Data System (ADS)

    Kipper, R.; Tenjes, P.; Tihhonova, O.; Tamm, A.; Tempel, E.

    2016-08-01

    We probe the feasibility of describing the structure of a multi-component axisymmetric galaxy with a dynamical model based on the Jeans equations while taking into account a third integral of motion. We demonstrate that using the third integral in the form derived by G. Kuzmin, it is possible to calculate the stellar kinematics of a galaxy from the Jeans equations by integrating the equations along certain characteristic curves. In cases where the third integral of motion does not describe the system exactly, the derived kinematics would describe the galaxy only approximately. We apply our method to the Andromeda galaxy, for which the mass distribution is relatively firmly known. We are able to reproduce the observed stellar kinematics of the galaxy rather well. The calculated model suggests that the velocity dispersion ratios ${\\sigma}_z^2/{\\sigma}_R^2$ of M31 decrease with increasing R. Moving away from the galactic plane, ${\\sigma}_z^2/{\\sigma}_R^2$ remains the same. The velocity dispersions ${\\sigma}_{\\theta}^2$ and ${\\sigma}_R^2$ are roughly equal in the galactic plane.

  3. Stellar kinematics using a third integral of motion: method and application on the Andromeda galaxy

    NASA Astrophysics Data System (ADS)

    Kipper, R.; Tenjes, P.; Tihhonova, O.; Tamm, A.; Tempel, E.

    2016-08-01

    We probe the feasibility of describing the structure of a multicomponent axisymmetric galaxy with a dynamical model based on the Jeans equations while taking into account a third integral of motion. We demonstrate that using the third integral in the form derived by G. Kuzmin, it is possible to calculate the stellar kinematics of a galaxy from the Jeans equations by integrating the equations along certain characteristic curves. In the cases where the third integral of motion does not describe the system exactly, the derived kinematics would describe the galaxy only approximately. We apply our method to the Andromeda galaxy, for which the mass distribution is relatively firmly known. We are able to reproduce the observed stellar kinematics of the galaxy rather well. The calculated model suggests that the velocity dispersion ratios σ ^2_z/σ ^2_R of M31 decrease with increasing R. Moving away from the galactic plane, σ ^2_z/σ ^2_R remains the same. The velocity dispersions σ ^2_θ and σ ^2_R are roughly equal in the galactic plane.

  4. RED SUPERGIANTS IN THE ANDROMEDA GALAXY (M31)

    SciTech Connect

    Massey, Philip; Silva, David R.; Olsen, Knut A. G.; Levesque, Emily M.; Plez, Bertrand; Clayton, Geoffrey C.; Meynet, Georges; Maeder, Andre E-mail: dsilva@noao.ed E-mail: emsque@ifa.hawaii.ed E-mail: gclayton@fenway.phys.lsu.ed E-mail: andre.maeder@unige.c

    2009-09-20

    Red supergiants (RSGs) are a short-lived stage in the evolution of moderately massive stars (10-25 M{sub sun}), and as such their location in the H-R diagram provides an exacting test of stellar evolutionary models. Since massive star evolution is strongly affected by the amount of mass loss a star suffers, and since the mass-loss rates depend upon metallicity, it is highly desirable to study the physical properties of these stars in galaxies of various metallicities. Here we identify a sample of RSGs in M31, the most metal-rich of the Local Group galaxies. We determine the physical properties of these stars using both moderate resolution spectroscopy and broadband V - K photometry. We find that on average the RSGs of our sample are variable in V by 0.5 mag, smaller but comparable to the 0.9 mag found for Magellanic Cloud (MC) RSGs. No such variability is seen at K, also in accord with what we know of Galactic and MC RSGs. We find that there is a saturation effect in the model TiO band strengths with metallicities higher than solar. The physical properties we derive for the RSGs from our analysis with stellar atmosphere models agree well with the current evolutionary tracks, a truly remarkable achievement given the complex physics involved in each. We do not confirm an earlier result that the upper luminosities of RSGs depend upon metallicity; instead, the most luminous RSGs have log L/L{sub sun}{approx}5.2-5.3, broadly consistent but slightly larger than that recently observed by Smartt et al. as the upper luminosity limit to Type II-P supernovae, believed to have come from RSGs. We find that, on average, the RSGs are considerably more reddened than O and B stars, suggesting that circumstellar dust is adding a significant amount of extra extinction, {approx}0.5 mag, on average. This is in accord with our earlier findings on Milky Way and Magellanic Cloud stars. Finally, we call attention to a peculiar star whose spectrum appears to be heavily veiled, possibly due

  5. The Primordial Origin Model of Magnetic Fields in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Sofue, Yoshiaki; Machida, Mami; Kudoh, Takahiro

    2010-10-01

    We propose a primordial-origin model for composite configurations of global magnetic fields in spiral galaxies. We show that a uniform tilted magnetic field wound up into a rotating disk galaxy can evolve into composite magnetic configurations comprising bisymmetric spiral (S = BSS), axisymmetric spiral (A = ASS), plane-reversed spiral (PR), and/or ring (R) fields in the disk, and vertical (V) fields in the center. By MHD simulations we show that these composite galactic fields are indeed created from a weak primordial uniform field, and that different configurations can co-exist in the same galaxy. We show that spiral fields trigger the growth of two-armed gaseous arms. The centrally accumulated vertical fields are twisted and produce a jet toward the halo. We found that the more vertical was the initial uniform field, the stronger was the formed magnetic field in the galactic disk.

  6. YELLOW SUPERGIANTS IN THE ANDROMEDA GALAXY (M31)

    SciTech Connect

    Drout, Maria R.; Massey, Philip; Meynet, Georges; Tokarz, Susan; Caldwell, Nelson E-mail: Phil.Massey@lowell.ed E-mail: tokarz@cfa.harvard.ed

    2009-09-20

    The yellow supergiant content of nearby galaxies can provide a critical test of stellar evolution theory, bridging the gap between the hot, massive stars and the cool red supergiants. But, this region of the color-magnitude diagram is dominated by foreground contamination, requiring membership to somehow be determined. Fortunately, the large negative systemic velocity of M31, coupled to its high rotation rate, provides the means for separating the contaminating foreground dwarfs from the bona fide yellow supergiants within M31. We obtained radial velocities of {approx}2900 individual targets within the correct color-magnitude range corresponding to masses of 12 M{sub sun} and higher. A comparison of these velocities to those expected from M31's rotation curve reveals 54 rank-1 (near certain) and 66 rank-2 (probable) yellow supergiant members, indicating a foreground contamination >= 96%. We expect some modest contamination from Milky Way halo giants among the remainder, particularly for the rank-2 candidates, and indeed follow-up spectroscopy of a small sample eliminates four rank 2's while confirming five others. We find excellent agreement between the location of yellow supergiants in the H-R diagram and that predicted by the latest Geneva evolutionary tracks that include rotation. However, the relative number of yellow supergiants seen as a function of mass varies from that predicted by the models by a factor of >10, in the sense that more high-mass yellow supergiants are predicted than those are actually observed. Comparing the total number (16) of >20 M{sub sun} yellow supergiants with the estimated number (24,800) of unevolved O stars indicates that the duration of the yellow supergiant phase is {approx}3000 years. This is consistent with what the 12 M{sub sun} and 15 M{sub sun} evolutionary tracks predict, but disagrees with the 20,000-80,000 year timescales predicted by the models for higher masses.

  7. Strengthening the Connection Between Space and Society: A Comparative Analysis of Supernovae Distribution in the Andromeda Galaxy for Secondary School Students

    NASA Astrophysics Data System (ADS)

    Borders, Kareen; Mendez, B.; Borders, K.; Thaller, M.; Plecki, M.; Usuda, K.

    2011-05-01

    In order to prepare students in grades 4-12 for a global workforce, NASA supports science, technology, engineering, and math (STEM) immersion education for secondary students. Secondary schools, through the NASA Explorer School program, the Spitzer Space Telescope, the National Optical Astronomy Observatory, and the WISE (Wide Field Infrared Survey Explorer) Telescope Teacher Ambassador program, offer authentic research opportunities for students. Spitzer and WISE studied the sky in infrared light. Among the objects WISE studied are asteroids, the coolest and dimmest stars, and the most luminous galaxies. The lessons learned from the NASA Explorer School program and Spitzer and WISE teacher and student programs can be applied to other programs, engaging students in authentic research experiences by using data from space-borne and earth-based observatories such Kitt Peak Observatory. Several ground based telescopes at Kitt Peak Observatory study visible light from objects such as supernovae. Utilizing a student research immersion philosophy along with data analysis skills learned from the Spitzer and WISE student research programs, an analysis of supernovae distribution with respect to location in the Andromeda galaxy was conducted using images of the Andromeda galaxy taken from the WIYN 0.9 meter telescope on Kitt Peak. A comparison was made between the 12 outer fields (spiral arms) and the 4 inner fields (central bulge). Novae were found by "blinking” images of each field throughout 100 epochs of data. Blinking is a technique used to compare images of fields and noting brightness (via x,y coordinates) in one field that is not visible in the same field during a different epoch. Although the central bulge was expected to contain more supernovae due to stellar density and proximity of stars to each other, analysis of data indicates that the there is also a concentration of supernovae that appeared in outer regions. WISE Telescope funding is gratefully acknowledged.

  8. The Globular Cluster System of the Spiral Galaxy NGC 7814

    NASA Astrophysics Data System (ADS)

    Rhode, Katherine L.; Zepf, Stephen E.

    2003-11-01

    We present the results of a wide-field photometric study of the globular cluster (GC) system of the edge-on Sab spiral NGC 7814. This is the first spiral to be fully analyzed from our survey of the GC systems of a large sample of galaxies beyond the Local Group. NGC 7814 is of particular interest because a previous study estimated that it has 500-1000 GCs, giving it the largest specific frequency (SN) known for a spiral. Understanding this galaxy's GC system is important in terms of our understanding of the GC populations of spirals in general and has implications for the formation of massive galaxies. We observed the galaxy in BVR filters with the WIYN 3.5 m telescope and used image classification and three-color photometry to select GC candidates. We also analyzed archival Hubble Space Telescope (HST) Wide Field Planetary Camera 2 images of NGC 7814, both to help quantify the contamination level of the WIYN GC candidate list and to detect GCs in the inner part of the galaxy halo. Combining HST data with high-quality ground-based images allows us to trace the entire radial extent of this galaxy's GC system and determine the total number of GCs directly through observation. We find that rather than being an especially high-SN spiral, NGC 7814 has <~200 GCs and SN~1, making it comparable to the two most well-studied spiral galaxies, the Milky Way and M31. We explore the implications of these results for models of the formation of galaxies and their GC systems. The initial results from our survey suggest that the GC systems of typical elliptical galaxies can be accounted for by the merger of two or more spirals, but that for highly luminous elliptical galaxies, additional physical processes may be needed.

  9. Substructure and Tidal Streams in the Andromeda Galaxy and its Satellites

    NASA Astrophysics Data System (ADS)

    Ferguson, Annette M. N.; Mackey, A. D.

    Tidal streams from existing and destroyed satellite galaxies populate the outer regions of the Andromeda galaxy (M31). This inhomogeneous debris can be studied without of many of the obstacles that plague Milky Way research. We review the history of tidal stream research in M31, and in its main satellite galaxies. We highlight the numerous tidal streams observed around M31, some of which reside at projected distances of up to ˜ 120 kpc from the center of this galaxy. Most notable is the Giant Stellar Stream, a signature of the most recent significant accretion event in the M31 system. This event involved an early-type progenitor of mass ˜ 109 M _{odot } that came within a few kpc of M31's center roughly a gigayear ago; almost all of the inner halo (R ≤ 50 kpc) debris in M31 can be tied either directly or indirectly to this event. We draw attention to the fact that most of M31's outer halo globular clusters lie preferentially on tidal streams and discuss the potential this offers to use these systems as probes of the accretion history. Tidal features observed around M33, M32, NGC 205 and NGC 147 are also reviewed. We conclude by discussing future prospects for this field.

  10. Face on Barred and Ringed Spiral Galaxy NGC 3351

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Ultraviolet image (left) and visual image (right) of the face on barred and ringed spiral galaxy NGC 3351 (M95). The morphological appearance of a galaxy can change dramatically between visual and ultraviolet wavelengths. In the case of M95, the nucleus and bar dominate the visual image. In the ultraviolet, the bar is not even visible and the ring and spiral arms dominate.

  11. Predicting the Velocity Dispersions of the Dwarf Satellite Galaxies of Andromeda

    NASA Astrophysics Data System (ADS)

    McGaugh, Stacy S.

    2016-05-01

    Dwarf Spheroidal galaxies in the Local Group are the faintest and most diffuse stellar systems known. They exhibit large mass discrepancies, making them popular laboratories for studying the missing mass problem. The PANDAS survey of M31 revealed dozens of new examples of such dwarfs. As these systems were discovered, it was possible to use the observed photometric properties to predict their stellar velocity dispersions with the modified gravity theory MOND. These predictions, made in advance of the observations, have since been largely confirmed. A unique feature of MOND is that a structurally identical dwarf will behave differently when it is or is not subject to the external field of a massive host like Andromeda. The role of this "external field effect" is critical in correctly predicting the velocity dispersions of dwarfs that deviate from empirical scaling relations. With continued improvement in the observational data, these systems could provide a test of the strong equivalence principle.

  12. Stellar Orbital Studies in Normal Spiral Galaxies: Effect of Spiral Arms on Disk Dynamics

    NASA Astrophysics Data System (ADS)

    Pérez-Villegas, A.; Pichardo, B.; Moreno, E.

    2015-10-01

    We have built a family of non-axisymmetric potential models for normal non-barred spiral galaxies. For this purpose, a three-dimensional self-gravitating model of spiral arms (PERLAS) is used. We analyze the stellar dynamics on the disk plane, varying structural and dynamical parameters such as pitch angle, strength of spiral arms and angular speed. For the pitch angle, we found two limits. The first limit, based on ordered behavior, periodic orbit studies show that for pitch angles up to approximately 15{(°) }, 18{(°) }, and 20{(°) } for Sa, Sb and Sc galaxies, respectively, the spiral arms could be long-lasting structures. Beyond those limits, spiral arms may be explained as transient features rather than long-lasting large-scale structures. In a second limit, from a phase space orbital study based on chaotic behavior, we found that for pitch angles larger than ˜ 30{(°) }, ˜ 40{(°) } and ˜ 50{(°) } for Sa, Sb, and Sc galaxies, respectively, chaotic orbits dominate all the prograde phase space region that surrounds the periodic orbits sculpting the spiral arms, and can even destroy them. Finally, we studied orbital dynamics varying other parameters such as the pattern speed and the spiral arm mass; also we looked for restrictions for these parameters in different morphological types. In these studies we noticed that the effect of spiral arms on the disk dynamics, when we vary the pattern speed and mass, is strongly linked to the pitch angle.

  13. The Hot Gaseous Halos of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Bregman, J.

    2016-06-01

    In the Milky Way, absorption and emission line measurements of O VII and O VIII show that the halo environment is dominated by a nearly spherical halo of temperature 2 × 10^6 K, metallicity of 0.3-0.5 solar, and with a density decreasing as r^{-3/2}. The mass of the hot gas, estimated through extrapolation to the virial radius, is comparable to the stellar mass, but does not account for the missing mass. The Milky Way hot halo appears to be rotating at about 180 km/s, which is consistent with model expectations, depending on the time of infall. Around massive spiral galaxies, hot halos are seen in emission out to about 70 kpc in the best cases. These show similar gas density laws and metallicities in the range 0.1-0.5 solar. The gas mass is comparable to the stellar mass, but does not account for the missing baryons within the virial radius. If the density law can be extrapolated to about three virial radii, the missing baryons would be accounted for.

  14. Variable Stars and Stellar Populations in Andromeda XXI. II. Another Merged Galaxy Satellite of M31?

    NASA Astrophysics Data System (ADS)

    Cusano, Felice; Garofalo, Alessia; Clementini, Gisella; Cignoni, Michele; Federici, Luciana; Marconi, Marcella; Musella, Ilaria; Ripepi, Vincenzo; Speziali, Roberto; Sani, Eleonora; Merighi, Roberto

    2015-06-01

    B and V time-series photometry of the M31 dwarf spheroidal satellite Andromeda XXI (And XXI) was obtained with the Large Binocular Cameras at the Large Binocular Telescope. We have identified 50 variables in And XXI, of which 41 are RR Lyrae stars (37 fundamental-mode—RRab, and 4 first-overtone-RRc, pulsators) and 9 are Anomalous Cepheids (ACs). The average period of the RRab stars (< {P}{ab}> =0.64 days) and the period-amplitude diagram place And XXI in the class of Oosterhoff II—Oosterhoff-Intermediate objects. From the average luminosity of the RR Lyrae stars we derived the galaxy distance modulus of (m - M)0 = 24.40 ± 0.17 mag, which is smaller than previous literature estimates, although still consistent with them within 1σ. The galaxy color-magnitude diagram shows evidence for the presence of three different stellar generations in And XXI: (1) an old (˜12 Gyr) and metal-poor ([Fe/H] = -1.7 dex) component traced by the RR Lyrae stars; (2) a slightly younger (10-6 Gyr) and more metal-rich ([Fe/H] = -1.5 dex) component populating the red horizontal branch, and (3) an intermediate age (˜1 Gyr) component with the same metallicity that produced the ACs. Finally, we provide hints that And XXI could be the result of a minor merging event between two dwarf galaxies. Based on data collected with the LBC at the LBT.

  15. CHARACTERISTICS OF SPIRAL ARMS IN LATE-TYPE GALAXIES

    SciTech Connect

    Honig, Z. N.; Reid, M. J.

    2015-02-10

    We have measured the positions of large numbers of H II regions in four nearly face-on, late-type, spiral galaxies: NGC 628 (M74), NGC 1232, NGC 3184, and NGC 5194 (M51). Fitting log-periodic spiral models to segments of each arm yields local estimates of spiral pitch angle and arm width. While pitch angles vary considerably along individual arms, among arms within a galaxy, and among galaxies, we find no systematic trend with galactocentric distance. We estimate the widths of the arm segments from the scatter in the distances of the H II regions from the spiral model. All major arms in these galaxies show spiral arm width increasing with distance from the galactic center, similar to the trend seen in the Milky Way. However, in the outermost parts of the galaxies, where massive star formation declines, some arms reverse this trend and narrow. We find that spiral arms often appear to be composed of segments of ∼5 kpc length, which join to form kinks and abrupt changes in pitch angle and arm width; these characteristics are consistent with properties seen in the large N-body simulations of D'Onghia et al. and others.

  16. Hot Gaseous Coronae around Spiral Galaxies: Probing the Illustris Simulation

    NASA Astrophysics Data System (ADS)

    Bogdán, Ákos; Vogelsberger, Mark; Kraft, Ralph P.; Hernquist, Lars; Gilfanov, Marat; Torrey, Paul; Churazov, Eugene; Genel, Shy; Forman, William R.; Murray, Stephen S.; Vikhlinin, Alexey; Jones, Christine; Böhringer, Hans

    2015-05-01

    The presence of hot gaseous coronae around present-day massive spiral galaxies is a fundamental prediction of galaxy formation models. However, our observational knowledge remains scarce, since to date only four gaseous coronae have been detected around spirals with massive stellar bodies (≳ 2× {{10}11} {{M}⊙ }). To explore the hot coronae around lower mass spiral galaxies, we utilized Chandra X-ray observations of a sample of eight normal spiral galaxies with stellar masses of (0.7-2.0)× {{10}11} {{M}⊙ }. Although statistically significant diffuse X-ray emission is not detected beyond the optical radii (˜20 kpc) of the galaxies, we derive 3σ limits on the characteristics of the coronae. These limits, complemented with previous detections of NGC 1961 and NGC 6753, are used to probe the Illustris Simulation. The observed 3σ upper limits on the X-ray luminosities and gas masses exceed or are at the upper end of the model predictions. For NGC 1961 and NGC 6753 the observed gas temperatures, metal abundances, and electron density profiles broadly agree with those predicted by Illustris. These results hint that the physics modules of Illustris are broadly consistent with the observed properties of hot coronae around spiral galaxies. However, one shortcoming of Illustris is that massive black holes, mostly residing in giant ellipticals, give rise to powerful radio-mode active galactic nucleus feedback, which results in under-luminous coronae for ellipticals.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Dwarf spheroidal galaxies are among the most numerous galaxy population in the Universe, but their main formation and evolution channels are still not well understood. The three dwarf spheroidal satellites (NGC 147, NGC 185, and NGC 205) of the Andromeda galaxy are characterised by very different interstellar medium (ISM) properties, which might suggest them being at different galaxy evolutionary stages. While the dust content of NGC 205 has been studied in detail by De Looze et al. (2012), we present new Herschel dust continuum observations of NGC 147 and NGC 185. The non-detection of NGC 147 in Herschel SPIRE maps puts a strong constraint on its dust mass (≤ 128^{+124}_{-68} M⊙). For NGC 185, we derive a total dust mass Md = 5.1±1.0 × 103 M⊙, which is a factor of ˜ 2-3 higher than that derived from ISO and Spitzer observations and confirms the need for longer wavelength observations to trace more massive cold dust reservoirs. We, furthermore, estimate the dust production by asymptotic giant branch (AGB) stars and supernovae (SNe). For NGC 147, the upper limit on the dust mass is consistent with expectations of the material injected by the evolved stellar population. In NGC 185 and NGC 205, the observed dust content is one order of magnitude higher compared to the estimated dust production by AGBs and SNe. Efficient grain growth, and potentially longer dust survival times (3-6 Gyr) are required to account for their current dust content. Our study confirms the importance of grain growth in the gas phase to account for the current dust reservoir in galaxies.

  19. 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.

  20. 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.

  1. Can cluster environment modify the dynamical evolution of spiral galaxies?

    NASA Technical Reports Server (NTRS)

    Amram, P.; Balkowski, C.; Cayatte, V.; Marcelin, M.; Sullivan, W. T., III

    1993-01-01

    Over the past decade many effects of the cluster environment on member galaxies have been established. These effects are manifest in the amount and distribution of gas in cluster spirals, the luminosity and light distributions within galaxies, and the segregation of morphological types. All these effects could indicate a specific dynamical evolution for galaxies in clusters. Nevertheless, a more direct evidence, such as a different mass distribution for spiral galaxies in clusters and in the field, is not yet clearly established. Indeed, Rubin, Whitmore, and Ford (1988) and Whitmore, Forbes, and Rubin (1988) (referred to as RWF) presented evidence that inner cluster spirals have falling rotation curves, unlike those of outer cluster spirals or the great majority of field spirals. If falling rotation curves exist in centers of clusters, as argued by RWF, it would suggest that dark matter halos were absent from cluster spirals, either because the halos had become stripped by interactions with other galaxies or with an intracluster medium, or because the halos had never formed in the first place. Even if they didn't disagree with RWF, other researchers pointed out that the behaviour of the slope of the rotation curves of spiral galaxies (in Virgo) is not so clear. Amram, using a different sample of spiral galaxies in clusters, found only 10% of declining rotation curves (2 declining vs 17 flat or rising) in opposition to RWF who find about 40% of declining rotation curves in their sample (6 declining vs 10 flat or rising), we will hereafter briefly discuss the Amram data paper and compare it to the results of RWF. We have measured the rotation curves for a sample of 21 spiral galaxies in 5 nearby clusters. These rotation curves have been constructed from detailed two-dimensional maps of each galaxy's velocity field as traced by emission from the Ha line. This complete mapping, combined with the sensitivity of our CFHT 3.60 m. + Perot-Fabry + CCD observations, allows

  2. Dynamics of Non-steady Spiral Arms in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Baba, Junichi; Saitoh, Takayuki R.; Wada, Keiichi

    2013-01-01

    In order to understand the physical mechanisms underlying non-steady stellar spiral arms in disk galaxies, we analyzed the growing and damping phases of their spiral arms using three-dimensional N-body simulations. We confirmed that the spiral arms are formed due to a swing amplification mechanism that reinforces density enhancement as a seeded wake. In the damping phase, the Coriolis force exerted on a portion of the arm surpasses the gravitational force that acts to shrink the portion. Consequently, the stars in the portion escape from the arm, and subsequently they form a new arm at a different location. The time-dependent nature of the spiral arms originates in the continual repetition of this nonlinear phenomenon. Since a spiral arm does not rigidly rotate, but follows the galactic differential rotation, the stars in the arm rotate at almost the same rate as the arm. In other words, every single position in the arm can be regarded as the corotation point. Due to interaction with their host arms, the energy and angular momentum of the stars change, thereby causing radial migration of the stars. During this process, the kinetic energy of random motion (random energy) of the stars does not significantly increase, and the disk remains dynamically cold. Owing to this low degree of disk heating, short-lived spiral arms can recurrently develop over many rotational periods. The resultant structure of the spiral arms in the N-body simulations is consistent with the observational nature of spiral galaxies. We conclude that the formation and structure of spiral arms in isolated disk galaxies can be reasonably understood by nonlinear interactions between a spiral arm and its constituent stars.

  3. DYNAMICS OF NON-STEADY SPIRAL ARMS IN DISK GALAXIES

    SciTech Connect

    Baba, Junichi; Saitoh, Takayuki R.; Wada, Keiichi

    2013-01-20

    In order to understand the physical mechanisms underlying non-steady stellar spiral arms in disk galaxies, we analyzed the growing and damping phases of their spiral arms using three-dimensional N-body simulations. We confirmed that the spiral arms are formed due to a swing amplification mechanism that reinforces density enhancement as a seeded wake. In the damping phase, the Coriolis force exerted on a portion of the arm surpasses the gravitational force that acts to shrink the portion. Consequently, the stars in the portion escape from the arm, and subsequently they form a new arm at a different location. The time-dependent nature of the spiral arms originates in the continual repetition of this nonlinear phenomenon. Since a spiral arm does not rigidly rotate, but follows the galactic differential rotation, the stars in the arm rotate at almost the same rate as the arm. In other words, every single position in the arm can be regarded as the corotation point. Due to interaction with their host arms, the energy and angular momentum of the stars change, thereby causing radial migration of the stars. During this process, the kinetic energy of random motion (random energy) of the stars does not significantly increase, and the disk remains dynamically cold. Owing to this low degree of disk heating, short-lived spiral arms can recurrently develop over many rotational periods. The resultant structure of the spiral arms in the N-body simulations is consistent with the observational nature of spiral galaxies. We conclude that the formation and structure of spiral arms in isolated disk galaxies can be reasonably understood by nonlinear interactions between a spiral arm and its constituent stars.

  4. The extended disc and halo of the Andromeda galaxy observed with Spitzer-IRAC

    NASA Astrophysics Data System (ADS)

    Rafiei Ravandi, Masoud; Barmby, Pauline; Ashby, Matthew L. N.; Laine, Seppo; Davidge, T. J.; Zhang, Jenna; Bianchi, Luciana; Babul, Arif; Chapman, S. C.

    2016-06-01

    We present the first results from an extended survey of the Andromeda galaxy (M31) using 41.1 h of observations by Spitzer-IRAC at 3.6 and 4.5 µm. This survey extends previous observations to the outer disc and halo, covering total lengths of 4.4° and 6.6° along the minor and major axes, respectively. We have produced surface brightness profiles by combining the integrated light from background-corrected maps with stellar counts from a new catalogue of point sources. Using auxiliary catalogues, we have carried out a statistical analysis in colour-magnitude space to discriminate M31 objects from foreground Milky Way stars and background galaxies. The catalogue includes 426 529 sources, of which 66 per cent have been assigned probability values to identify M31 objects with magnitude depths of [3.6] = 19.0 ± 0.2, [4.5] = 18.7 ± 0.2. We discuss applications of our data for constraining the stellar mass and characterizing point sources in the outer radii.

  5. Collision Tomography: Physical Properties of Possible Progenitors of the Andromeda Stellar Stream

    NASA Astrophysics Data System (ADS)

    Miki, Yohei; Mori, Masao; Rich, R. Michael

    2016-08-01

    To unveil a progenitor of the Andromeda Giant Stellar Stream, we investigate the interaction between an accreting satellite galaxy and the Andromeda Galaxy using an N-body simulation. We perform a comprehensive exploration of the properties of the progenitor dwarf galaxy, using 247 models of varying mass, mass distribution, and size. We show that the binding energy of the progenitor is the crucial parameter in reproducing the Andromeda Giant Stellar Stream and the shell-like structures surrounding the Andromeda Galaxy. As a result of the simulations, the progenitor must satisfy a simple scaling relation between the core radius, the total mass and the tidal radius. Using this relation, we successfully constrain the physical properties of the progenitors to have masses ranging from 5× {10}8{M}ȯ to 5× {10}9{M}ȯ and central surface densities around {10}3 {M}ȯ {{pc}}-2. A detailed comparison between our result and the nearby observed galaxies indicates that possible progenitors of the Andromeda Giant Stellar Stream include a dwarf elliptical galaxy, a dwarf irregular galaxy, and a small spiral galaxy.

  6. The gas/dust ratio in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Devereux, Nicholas A.

    1990-01-01

    IRAS data are used here to calculate warm dust masses, which are then compared with the molecular and atomic gas masses for 58 spiral galaxies in order to constrain the fraction and the phase of the interstellar medium in spiral galaxies that contributes to the emission measured by IRAS. The dispersion in the ratio of dust mass to total gas mass is larger than expected on the basis of measurement errors. The dispersion in the ratio of dust mass to inner disk gas mass is less than the dispersion in the ratio of IR to radio emission. The inner gas to warm dust mass ratio for spiral galaxies is 1080 + or - 70, indicating that 80-90 percent of the dust mass in spiral galaxies is radiating at over 100 microns and has a temperature less than about 30 K. However, the bulk of the dust in spiral galaxies is less than about 15 K regardless of the phase of the ISM. Both H I and H2-associated dust contributes to the warm 30 K emission.

  7. SELF-PERPETUATING SPIRAL ARMS IN DISK GALAXIES

    SciTech Connect

    D'Onghia, Elena; Vogelsberger, Mark; Hernquist, Lars

    2013-03-20

    The causes of spiral structure in galaxies remain uncertain. Leaving aside the grand bisymmetric spirals with their own well-known complications, here we consider the possibility that multi-armed spiral features originate from density inhomogeneities orbiting within disks. Using high-resolution N-body simulations, we follow the motions of stars under the influence of gravity, and show that mass concentrations with properties similar to those of giant molecular clouds can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, we demonstrate that the eventual response of the disk can be highly non-linear, significantly modifying the formation and longevity of the resulting patterns. Contrary to expectations, ragged spiral structures can thus survive at least in a statistical sense long after the original perturbing influence has been removed.

  8. Turbulence and Star Formation in a Sample of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Maier, Erin R.; Hunter, Deidre Ann; Chien, Li-Hsin

    2016-01-01

    We investigate turbulent gas motions in spiral galaxies and their importance to star formation in far outer disks, where the column density is typically far below the critical value for spontaneous gravitational collapse. Following the methods of Burkhart et al. (2010) as applied to the Small Magellanic Cloud, we use the third and fourth statistical moments, skewness and kurtosis, which are indicators of structures caused by turbulence, to examine the integrated neutral hydrogen (Hι) column density of a sample of spiral galaxies selected from The Hι Nearby Galaxy Survey (THINGS, Walter et al. 2008). We examine the kurtosis and skewness values of each galaxy as a whole, as well as their variation as a function of radius and in discrete sub-regions defined by a square, moving 'kernel,' essentially splitting each galaxy into a grid. We then create individual grid maps of kurtosis and skewness for each galaxy. To investigate the relation between these moments and star formation, we compare these maps with maps of each galaxy's far-ultraviolet (FUV) image, taken by the Galaxy Evolution Explorer (GALEX) satellite. We find that the moments are largely uniform across the galaxies: the variation does not appear to trace any star forming regions. This may, however, be due to the spatial resolution of our analysis, which could potentially limit the scale of turbulent motions to at most ~700 pc. From our analysis of the comparison between the two moments themselves, we find that the gas motions in our sample galaxies are largely supersonic. This analysis shows that Burkhart et al. (2010)'s methods may be applied not just to dwarf galaxies but normal spiral galaxies as well.We acknowledge the NSF for their funding of this work through their Research Experience for Undergraduates (REU) program (Grant No. AST-1461200).

  9. WATER MASERS IN THE ANDROMEDA GALAXY: THE FIRST STEP TOWARD PROPER MOTION

    SciTech Connect

    Darling, Jeremy

    2011-05-01

    We have detected and confirmed five water maser complexes in the Andromeda Galaxy (M31) using the Green Bank Telescope. These masers will provide the high brightness temperature point sources needed for proper motion studies of M31, enabling measurement of its full three-dimensional velocity vector and its geometric distance via proper rotation. The motion of M31 is the keystone of Local Group dynamics and a gateway to the dark matter profiles of galaxies in general. Our survey for water masers selected 206 luminous compact 24 {mu}m emitting regions in M31 and was sensitive enough to detect any maser useful for {approx}10 {mu}as yr{sup -1} astrometry. The newly discovered masers span the isotropic luminosity range (0.3-1.9) x 10{sup -3} L{sub sun} in single spectral components and are analogous to luminous Galactic masers. The masers are distributed around the molecular ring, including locations close to the major and minor axes, which is nearly ideal for proper motion studies. We find no correlation between 24 {mu}m luminosity and water maser luminosity, suggesting that while water masers arise in star-forming regions, the nonlinear amplification pathways and beamed nature of the water masers means that they are not predictable based on IR luminosity alone. This suggests that there are additional bright masers to be found in M31. We predict that the geometric distance and systemic proper motion of M31 can be measured in 2-3 years with current facilities. A 'moving cluster' observation of diverging masers as M31 approaches the Galaxy may be possible in the long term.

  10. Getting to Know the Neighbors: Deep Imaging of the Andromeda Satellite Dwarf Galaxy Cassiopeia III with WIYN pODI

    NASA Astrophysics Data System (ADS)

    Smith, Madison; Rhode, Katherine L.; Janowiecki, Steven

    2016-01-01

    We present results from WIYN pODI imaging of Cassiopeia III/Andromeda XXXII (Cas III/And XXXII), an Andromeda satellite dwarf galaxy recently discovered by Martin et al. (2013) in Pan-STARRS1 survey data. Detailed studies of satellite dwarf galaxies in the Local Group and its environs provide important insight into how low-mass galaxies form and evolve as well as how more massive galaxies are assembled in a hierarchical universe. The goal of this project is to obtain deep, wide-field photometry of Cas III in order to study its stellar population in more detail. The images used for this analysis were taken in October 2013 with the 24' x 24' pODI camera on the WIYN 3.5-m telescope in the SDSS g and i filters. Calibrated photometry was performed on all point sources in the g and i images and then used to quantify the radial distribution of stars in Cas III and to construct a color-magnitude diagram (CMD). We present this CMD along with a map of the resolved stellar population and measurements of the galaxy magnitude and structural properties. This research was supported by the NSF Research Experiences for Undergraduates program (grant number AST-1358980).

  11. On the origin and history of stars in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Hernández, David M.; Macció, Andrea V.; van den Bosch, Frank C.

    2010-10-01

    The formation of spiral galaxies is an important topic of debate in astrophysics. We use smooth-particle hydrodynamic (SPH) simulations to follow the formation, in a fully ΛCDM cosmological context, of two disk galaxies similar, in mass, to our Milky Way. Using the dynamics of the star particles we are able to identify three distinct components in the stellar budget of our galaxies: a thin disk, a thick disk and a spheroid. We make a detailed analysis of where and when stars in the three different components come about. Our study can help create a more consistent picture of how galaxies similar to our own form.

  12. The relation between infrared and radio emission in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Helou, George

    1991-01-01

    A remarkable correlation between the far infrared and the radio continuum emission of star forming galaxies was one of the early results based on IRAS data, and has remained one of the most intriguing. Recent work has extended the correlation to early type galaxies, revealing a slightly different ratio in lenticulars. When radio and infrared maps of disk galaxies are compared, the radio disks appear systematically more diffuse. This has been interpreted as a manifestation of the diffusion of cosmic-ray electrons, and has allowed a fresh look at the behavior of magnetic fields and cosmic rays in spiral galaxies, and at their relation to the rest of the interstellar medium.

  13. Star formation rates of spiral galaxies in the Cosmic Web

    NASA Astrophysics Data System (ADS)

    Alpaslan, Mehmet; Marcum, Pamela M.; Galaxy And Mass Assembly (GAMA)

    2016-01-01

    We look for shifts in stellar mass and star formation rate along filaments in the cosmic web by examining the stellar masses and UV-derived star formation rates of 1,799 ungrouped and unpaired spiral galaxies from the Galaxy And Mass Assembly (GAMA) survey that reside in filaments. We devise multiple distance metrics to characterise the complex geometry of filaments, and find that galaxies closer to the orthogonal core of a filament have higher stellar masses than their counterparts near the periphery of filaments, on the edges of voids. We also find that these peripheral galaxies have higher specific star formations at a given mass. Our results suggest a model in which gas accretion from voids onto filaments is primarily in an orthogonal direction. While the star formation rates of spiral galaxies in filaments are susceptible to their locations, we find that the global star formation rates of galaxies in different large scale environments are similar to each other. The primary discriminant in star formation rates is therefore the stellar mass of each spiral galaxy, as opposed to its large scale environment.

  14. Star Formation in Partially Gas-Depleted Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Rose, James A.; Robertson, Paul; Miner, Jesse; Levy, Lorenza

    2010-02-01

    Broadband B and R and Hα images have been obtained with the 4.1 m SOAR telescope atop Cerro Pachon, Chile, for 29 spiral galaxies in the Pegasus I galaxy cluster and for 18 spirals in non-cluster environments. Pegasus I is a spiral-rich cluster with a low-density intracluster medium and a low galaxy velocity dispersion. When combined with neutral hydrogen (H I) data obtained with the Arecibo 305 m radio telescope, acquired by Levy et al. (2007) and by Springob et al. (2005b), we study the star formation rates in disk galaxies as a function of their H I deficiency. To quantify H I deficiency, we use the usual logarithmic deficiency parameter, DEF. The specific star formation rate (SSFR) is quantified by the logarithmic flux ratio of Hα flux to R-band flux, and thus roughly characterizes the logarithmic SFR per unit stellar mass. We find a clear correlation between the global SFR per unit stellar mass and DEF, such that the SFR is lower in more H I-deficient galaxies. This correlation appears to extend from the most gas-rich to the most gas-poor galaxies. We also find a correlation between the central SFR per unit mass relative to the global values, in the sense that the more H I-deficient galaxies have a higher central SFR per unit mass relative to their global SFR values than do gas-rich galaxies. In fact, approximately half of the H I-depleted galaxies have highly elevated SSFRs in their central regions, indicative of a transient evolutionary state. In addition, we find a correlation between gas depletion and the size of the Hα disk (relative to the R-band disk); H I-poor galaxies have truncated disks. Moreover, aside from the elevated central SSFR in many gas-poor spirals, the SSFR is otherwise lower in the Hα disks of gas-poor galaxies than in gas-rich spirals. Thus, both disk truncation and lowered SSFR levels within the star-forming part of the disks (aside from the enhanced nuclear SSFR) correlate with H I deficiency, and both phenomena are found to

  15. STAR FORMATION IN PARTIALLY GAS-DEPLETED SPIRAL GALAXIES

    SciTech Connect

    Rose, James A.; Miner, Jesse; Levy, Lorenza; Robertson, Paul E-mail: paul@astr.as.utexas.edu E-mail: lorenza.levy@yahoo.com

    2010-02-15

    Broadband B and R and H{alpha} images have been obtained with the 4.1 m SOAR telescope atop Cerro Pachon, Chile, for 29 spiral galaxies in the Pegasus I galaxy cluster and for 18 spirals in non-cluster environments. Pegasus I is a spiral-rich cluster with a low-density intracluster medium and a low galaxy velocity dispersion. When combined with neutral hydrogen (H I) data obtained with the Arecibo 305 m radio telescope, acquired by Levy et al. (2007) and by Springob et al. (2005b), we study the star formation rates in disk galaxies as a function of their H I deficiency. To quantify H I deficiency, we use the usual logarithmic deficiency parameter, DEF. The specific star formation rate (SSFR) is quantified by the logarithmic flux ratio of H{alpha} flux to R-band flux, and thus roughly characterizes the logarithmic SFR per unit stellar mass. We find a clear correlation between the global SFR per unit stellar mass and DEF, such that the SFR is lower in more H I-deficient galaxies. This correlation appears to extend from the most gas-rich to the most gas-poor galaxies. We also find a correlation between the central SFR per unit mass relative to the global values, in the sense that the more H I-deficient galaxies have a higher central SFR per unit mass relative to their global SFR values than do gas-rich galaxies. In fact, approximately half of the H I-depleted galaxies have highly elevated SSFRs in their central regions, indicative of a transient evolutionary state. In addition, we find a correlation between gas depletion and the size of the H{alpha} disk (relative to the R-band disk); H I-poor galaxies have truncated disks. Moreover, aside from the elevated central SSFR in many gas-poor spirals, the SSFR is otherwise lower in the H{alpha} disks of gas-poor galaxies than in gas-rich spirals. Thus, both disk truncation and lowered SSFR levels within the star-forming part of the disks (aside from the enhanced nuclear SSFR) correlate with H I deficiency, and both

  16. Enhanced Abundances in Spiral Galaxies of the Pegasus I Cluster

    NASA Astrophysics Data System (ADS)

    Robertson, Paul; Shields, Gregory A.; Blanc, Guillermo A.

    2012-03-01

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and velocity dispersion, also display gas loss due to interstellar-medium-intracluster-medium interaction, albeit to a lesser degree. Based on the abundances of three H I deficient spirals and two H I normal spirals, we observe a heavy element abundance offset of +0.13 ± 0.07 dex for the H I deficient galaxies. This abundance differential is consistent with the differential observed in Virgo for galaxies with a similar H I deficiency, and we observe a correlation between log (O/H) and the H I deficiency parameter DEF for the two clusters analyzed together. Our results suggest that similar environmental mechanisms are driving the heavy element enhancement in both clusters.

  17. ENHANCED ABUNDANCES IN SPIRAL GALAXIES OF THE PEGASUS I CLUSTER

    SciTech Connect

    Robertson, Paul; Shields, Gregory A.; Blanc, Guillermo A. E-mail: shields@astro.as.utexas.edu

    2012-03-20

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and velocity dispersion, also display gas loss due to interstellar-medium-intracluster-medium interaction, albeit to a lesser degree. Based on the abundances of three H I deficient spirals and two H I normal spirals, we observe a heavy element abundance offset of +0.13 {+-} 0.07 dex for the H I deficient galaxies. This abundance differential is consistent with the differential observed in Virgo for galaxies with a similar H I deficiency, and we observe a correlation between log (O/H) and the H I deficiency parameter DEF for the two clusters analyzed together. Our results suggest that similar environmental mechanisms are driving the heavy element enhancement in both clusters.

  18. Spiral galaxies in clusters. III. Gas-rich galaxies in the Pegasus I cluster of galaxies

    SciTech Connect

    Bothun, G.D.; Schommer, R.A.; Sullivan, W.T. III

    1982-05-01

    We report the results of a 21-cm and optical survey of disk galaxies in the vicinity of the Pegasus I cluster of galaxies. The color--gas content relation (log(M/sub H//L/sub B/) vs (B-V)/sup T//sub 0/ ) for this particular cluster reveals the presence of a substantial number of blue, gas-rich galaxies. With few exceptions, the disk systems in Pegasus I retain large amounts of neutral hydrogen despite their presence in a cluster. This directly shows that environmental processes have not yet removed substantial amounts of gas from these disk galaxies. We conclude that the environment has had little or no observable effect upon the evolution of disk galaxies in Pegasus I. The overall properties of the Pegasus I spirals are consistent with the suggestion that this cluster is now at an early stage in its evolution.

  19. Photometric scaling relations of lenticular and spiral galaxies

    NASA Astrophysics Data System (ADS)

    Laurikainen, E.; Salo, H.; Buta, R.; Knapen, J. H.; Comerón, S.

    2010-06-01

    Photometric scaling relations are studied for S0 galaxies and compared with those obtained for spirals. New two-dimensional multi-component decompositions are presented for 122 early-type disc galaxies, using deep Ks-band images. Combining them with our previous decompositions, the final sample consists of 175 galaxies (Near-Infrared Survey of S0s, NIRS0S: 117 S0s + 22 S0/a and 36 Sa galaxies). As a comparison sample we use the Ohio State University Bright Spiral Galaxy Survey (OSUBSGS) of nearly 200 spirals, for which similar multi-component decompositions have previously been made by us. The improved statistics, deep images and the homogeneous decomposition method used allow us to re-evaluate the parameters of the bulges and discs. For spirals we largely confirm previous results, which are compared with those obtained for S0s. Our main results are as follows. (1) Important scaling relations are present, indicating that the formative processes of bulges and discs in S0s are coupled [e.g. M0K(disc) = 0.63 M0K(bulge) -9.3], as has been found previously for spirals [for OSUBSGS spirals M0K (disc) = 0.38 M0K(bulge) -15.5 the rms deviation from these relations is 0.5 mag for S0s and spirals]. (2) We obtain median reff/h0r ~ 0.20, 0.15 and 0.10 for S0, S0/a-Sa and Sab-Sc galaxies, respectively: these values are smaller than predicted by simulation models in which bulges are formed by galaxy mergers. (3) The properties of bulges of S0s are different from the elliptical galaxies, which are manifested in the versus reff relation, in the photometric plane (μ0, n, reff), and to some extent also in the Kormendy relation (< μ >eff versus reff). The bulges of S0s are similar to bulges of spirals with M0K(bulge) < -20 mag. Some S0s have small bulges, but their properties are not compatible with the idea that they could evolve to dwarfs by galaxy harassment. (4) The relative bulge flux (B/T) for S0s covers the full range found in the Hubble sequence, even with 13 per cent

  20. Water Masers in the Andromeda Galaxy. II. Where Do Masers Arise?

    NASA Astrophysics Data System (ADS)

    Amiri, Nikta; Darling, Jeremy

    2016-08-01

    We present a comparative multiwavelength analysis of water-maser-emitting regions and non-maser-emitting luminous 24 μm star-forming regions in the Andromeda Galaxy (M31) to identify the sites most likely to produce luminous water masers useful for astrometry and proper motion studies. Included in the analysis are Spitzer 24 μm photometry, Herschel 70 and 160 μm photometry, Hα emission, dust temperature, and star-formation rate. We find significant differences between the maser-emitting and non-maser-emitting regions: water-maser-emitting regions tend to be more infrared-luminous and show higher star-formation rates. The five water masers in M31 are consistent with being analogs of water masers in Galactic star-forming regions and represent the high-luminosity tail of a larger (and as yet undetected) population. Most regions likely to produce water masers bright enough for proper motion measurements using current facilities have already been surveyed, but we suggest three ways to detect additional water masers in M31: (1) reobserve the most luminous mid- or far-infrared sources with higher sensitivity than was used in the Green Bank Telescope survey; (2) observe early-stage star-forming regions selected by millimeter continuum that have not already been selected by their 24 μm emission, and (3) reobserve the most luminous mid- or far-infrared sources and rely on maser variability for new detections.

  1. Gamma rays from dark matter minispikes in the Andromeda Galaxy M31

    SciTech Connect

    Fornasa, Mattia; Taoso, Marco; Bertone, Gianfranco

    2007-08-15

    The existence of a population of wandering intermediate mass black holes (IMBHs) is a generic prediction of scenarios that seek to explain the formation of supermassive black holes in terms of growth from massive seeds. The growth of IMBHs may lead to the formation of DM overdensities called ''mini-spikes,'' recently proposed as ideal targets for indirect DM searches. Current ground-based gamma-ray experiments, however, cannot search for these objects due to their limited field of view, and it might be challenging to discriminate mini-spikes in the Milky Way from the many astrophysical sources that GLAST is expected to observe. We show here that gamma-ray experiments can effectively search for IMBHs in the nearby Andromeda Galaxy (also known as M31), where mini-spikes would appear as a distribution of point-sources, isotropically distributed in a {approx_equal}3 deg. circle around the galactic center. For a neutralinolike DM candidate with a mass m{sub {chi}}=150 GeV, up to 20 sources would be detected with GLAST (at 5{sigma}, in 2 months). With air Cherenkov telescopes such as MAGIC and VERITAS, up to 10 sources might be detected, provided that the mass of neutralino is in the TeV range or above.

  2. DOES THE OOSTERHOFF DICHOTOMY EXIST IN THE ANDROMEDA GALAXY? I. THE CASE OF G11

    SciTech Connect

    Contreras Ramos, Rodrigo; Clementini, Gisella; Federici, Luciana E-mail: gisella.clementini@oabo.inaf.it; and others

    2013-03-01

    We present the first evidence that Oosterhoff type II globular clusters exist in the Andromeda galaxy (M31). On the basis of time-series photometry of the moderately metal-poor ([Fe/H] {approx}-1.6 dex) M31 globular cluster G11, obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope, we detected and derived periods for 14 RR Lyrae stars, of which five are found to lie inside the cluster tidal radius. They include three fundamental-mode (RRab) and two first-overtone (RRc) pulsators, with average periods (P{sub ab} ) = 0.70 days, and (P{sub c} ) = 0.40 days, respectively. These mean periods and the position of the cluster variable stars in the period-amplitude and period-metallicity diagrams all suggest that G11 is likely to be an Oosterhoff type II globular cluster. This appears to be in agreement with the general behavior of Milky Way globular clusters with similar metallicity and horizontal branch morphology.

  3. THE PAndAS VIEW OF THE ANDROMEDA SATELLITE SYSTEM. I. A BAYESIAN SEARCH FOR DWARF GALAXIES USING SPATIAL AND COLOR-MAGNITUDE INFORMATION

    SciTech Connect

    Martin, Nicolas F.; Ibata, Rodrigo A.; McConnachie, Alan W.; Mackey, A. Dougal; Ferguson, Annette M. N.; Irwin, Michael J.; Lewis, Geraint F.; Fardal, Mark A.

    2013-10-20

    We present a generic algorithm to search for dwarf galaxies in photometric catalogs and apply it to the Pan-Andromeda Archaeological Survey (PAndAS). The algorithm is developed in a Bayesian framework and, contrary to most dwarf galaxy search codes, makes use of both the spatial and color-magnitude information of sources in a probabilistic approach. Accounting for the significant contamination from the Milky Way foreground and from the structured stellar halo of the Andromeda galaxy, we recover all known dwarf galaxies in the PAndAS footprint with high significance, even for the least luminous ones. Some Andromeda globular clusters are also recovered and, in one case, discovered. We publish a list of the 143 most significant detections yielded by the algorithm. The combined properties of the 39 most significant isolated detections show hints that at least some of these trace genuine dwarf galaxies, too faint to be individually detected. Follow-up observations by the community are mandatory to establish which are real members of the Andromeda satellite system. The search technique presented here will be used in an upcoming contribution to determine the PAndAS completeness limits for dwarf galaxies. Although here tuned to the search of dwarf galaxies in the PAndAS data, the algorithm can easily be adapted to the search for any localized overdensity whose properties can be modeled reliably in the parameter space of any catalog.

  4. The PAndAS View of the Andromeda Satellite System. I. A Bayesian Search for Dwarf Galaxies Using Spatial and Color-Magnitude Information

    NASA Astrophysics Data System (ADS)

    Martin, Nicolas F.; Ibata, Rodrigo A.; McConnachie, Alan W.; Mackey, A. Dougal; Ferguson, Annette M. N.; Irwin, Michael J.; Lewis, Geraint F.; Fardal, Mark A.

    2013-10-01

    We present a generic algorithm to search for dwarf galaxies in photometric catalogs and apply it to the Pan-Andromeda Archaeological Survey (PAndAS). The algorithm is developed in a Bayesian framework and, contrary to most dwarf galaxy search codes, makes use of both the spatial and color-magnitude information of sources in a probabilistic approach. Accounting for the significant contamination from the Milky Way foreground and from the structured stellar halo of the Andromeda galaxy, we recover all known dwarf galaxies in the PAndAS footprint with high significance, even for the least luminous ones. Some Andromeda globular clusters are also recovered and, in one case, discovered. We publish a list of the 143 most significant detections yielded by the algorithm. The combined properties of the 39 most significant isolated detections show hints that at least some of these trace genuine dwarf galaxies, too faint to be individually detected. Follow-up observations by the community are mandatory to establish which are real members of the Andromeda satellite system. The search technique presented here will be used in an upcoming contribution to determine the PAndAS completeness limits for dwarf galaxies. Although here tuned to the search of dwarf galaxies in the PAndAS data, the algorithm can easily be adapted to the search for any localized overdensity whose properties can be modeled reliably in the parameter space of any catalog.

  5. Rings and spirals in barred galaxies - II. Ring and spiral morphology

    NASA Astrophysics Data System (ADS)

    Athanassoula, E.; Romero-Gómez, M.; Bosma, A.; Masdemont, J. J.

    2009-12-01

    In this series of papers, we propose a theory to explain the formation and properties of rings and spirals in barred galaxies. The building blocks of these structures are orbits guided by the manifolds emanating from the unstable Lagrangian points located near the ends of the bar. In this paper, we focus on a comparison of the morphology of observed and of theoretical spirals and rings and we also give some predictions for further comparisons. Our theory can account for spirals as well as both inner and outer rings. The model outer rings have the observed R1, R'1, R2, R'2 and R1R2 morphologies, including the dimples near the direction of the bar major axis. We explain why the vast majority of spirals in barred galaxies are two armed and trailing, and discuss what it would take for higher multiplicity arms to form. We show that the shapes of observed and theoretical spirals agree and we predict that stronger non-axisymmetric forcings at and somewhat beyond corotation will drive more open spirals. We compare the ratio of ring diameters in theory and in observations and predict that more elliptical rings will correspond to stronger forcings. We find that the model potential may influence strongly the numerical values of these ratios.

  6. On wave dark matter in spiral and barred galaxies

    NASA Astrophysics Data System (ADS)

    Martinez-Medina, Luis A.; Bray, Hubert L.; Matos, Tonatiuh

    2015-12-01

    We recover spiral and barred spiral patterns in disk galaxy simulations with a Wave Dark Matter (WDM) background (also known as Scalar Field Dark Matter (SFDM), Ultra-Light Axion (ULA) dark matter, and Bose-Einstein Condensate (BEC) dark matter). Here we show how the interaction between a baryonic disk and its Dark Matter Halo triggers the formation of spiral structures when the halo is allowed to have a triaxial shape and angular momentum. This is a more realistic picture within the WDM model since a non-spherical rotating halo seems to be more natural. By performing hydrodynamic simulations, along with earlier test particles simulations, we demonstrate another important way in which wave dark matter is consistent with observations. The common existence of bars in these simulations is particularly noteworthy. This may have consequences when trying to obtain information about the dark matter distribution in a galaxy, the mere presence of spiral arms or a bar usually indicates that baryonic matter dominates the central region and therefore observations, like rotation curves, may not tell us what the DM distribution is at the halo center. But here we show that spiral arms and bars can develop in DM dominated galaxies with a central density core without supposing its origin on mechanisms intrinsic to the baryonic matter.

  7. Diffuse X-Ray Emission in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Tyler, Krystal; Quillen, A. C.; LaPage, Amanda; Rieke, George H.

    2004-07-01

    We compare the soft diffuse X-ray emission from Chandra images of 12 nearby intermediate-inclination spiral galaxies to the morphology seen in Hα, molecular gas, and mid-infrared emission. We find that diffuse X-ray emission is often located along spiral arms in the outer parts of spiral galaxies but tends to be distributed in a more nearly radially symmetric morphology in the center. The X-ray morphology in the spiral arms matches that seen in the mid-infrared or Hα and thus implies that the X-ray emission is associated with recent active star formation. In the spiral arms there is a good correlation between the level of diffuse X-ray emission and that in the mid-infrared in different regions. The correlation between X-ray and mid-IR flux in the galaxy centers is less strong. We also find that the central X-ray emission tends to be more luminous in galaxies with brighter bulges, suggesting that more than one process is contributing to the level of central diffuse X-ray emission. We see no strong evidence for X-ray emission trailing the location of high-mass star formation in spiral arms. However, population synthesis models predict a high mechanical energy output rate from supernovae for a time period that is about 10 times longer than the lifetime of massive ionizing stars, conflicting with the narrow appearance of the arms in X-rays. The fraction of supernova energy that goes into heating the interstellar medium must depend on environment and is probably higher near sites of active star formation. The X-ray estimated emission measures suggest that the volume filling factors and scale heights are low in the outer parts of these galaxies but higher in the galaxy centers. The differences between the X-ray properties and morphology in the centers and outer parts of these galaxies suggest that galactic fountains operate in outer galaxy disks but that winds are primarily driven from galaxy centers.

  8. Star formation in bulgeless late type spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Das, M.; Ramya, S.; Sengupta, C.; Mishra, K.

    We present radio and follow-up optical observations of a sample of bulgeless late type spiral galaxies. We searched for signs of nuclear activity and disk star formation in the sample galaxies. Interaction induced star formation can often trigger bulge formation. We found significant radio emission associated with star formation in two sample galaxies, NGC3445 and NGC4027, both of which are tidally interacting with nearby companions. For the others, the star formation was either absent or limited to only localized regions in the disk. Both galaxies also have oval bars that are possibly pseudobulges that may later evolve into bulges. We did follow up optical Hα imaging and nuclear spectroscopy of NGC3445 and NGC4027 using the Himalayan Chandra Telescope (HCT). The Hα emission is mainly associated with strong spiral arms that have been triggered by the tidal interact1ions. The nuclear spectra of both galaxies indicate ongoing nuclear star formation but do not show signs of AGN activity. We thus conclude that star formation in bulgeless galaxies is generally low but is enhanced when the galaxies interact with nearby companions; this activity may ultimately lead to the formation of bulges in these galaxies.

  9. Far-infrared emission and star formation in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Trinchieri, G.; Fabbiano, G.; Bandiera, R.

    1989-01-01

    The correlations between the emission in the far-IR, H-alpha, and blue in a sample of normal spiral galaxies are investigated. It is found that the luminosities in these three bands are all tightly correlated, although both the strength of the correlations and their functional dependencies are a function of the galaxies' morphological types. The best-fit power laws to these correlations are different for the comparison of different quantities and deviate significantly from linearity in some cases, implying the presence of additional emission mechanisms not related to the general increase of luminosity with galactic mass. Clear evidence is found of two independent effects in the incidence of warm far-IR emission in late-type spirals. One is a luminosity effect shown by the presence of excess far-IR relative to H-alpha or optical emission in the more luminous galaxies. The other is a dependence on widespread star-formation activity.

  10. Gas and stellar spiral structures in tidally perturbed disc galaxies

    NASA Astrophysics Data System (ADS)

    Pettitt, Alex R.; Tasker, Elizabeth J.; Wadsley, James W.

    2016-06-01

    Tidal interactions between disc galaxies and low-mass companions are an established method for generating galactic spiral features. In this work, we present a study of the structure and dynamics of spiral arms driven in interactions between disc galaxies and perturbing companions in 3D N-body/smoothed hydrodynamical numerical simulations. Our specific aims are to characterize any differences between structures formed in the gas and stars from a purely hydrodynamical and gravitational perspective, and to find a limiting case for spiral structure generation. Through analysis of a number of different interacting cases, we find that there is very little difference between arm morphology, pitch angles and pattern speeds between the two media. The main differences are a minor offset between gas and stellar arms, clear spurring features in gaseous arms, and different radial migration of material in the stronger interacting cases. We investigate the minimum mass of a companion required to drive spiral structure in a galactic disc, finding the limiting spiral generation cases with companion masses of the order of 1 × 109 M⊙, equivalent to only 4 per cent of the stellar disc mass, or 0.5 per cent of the total galactic mass of a Milky Way analogue.

  11. On galaxy spiral arms' nature as revealed by rotation frequencies

    NASA Astrophysics Data System (ADS)

    Roca-Fàbrega, Santi; Valenzuela, Octavio; Figueras, Francesca; Romero-Gómez, Mercè; Velázquez, Héctor; Antoja, Teresa; Pichardo, Bárbara

    2013-07-01

    High-resolution N-body simulations using different codes and initial condition techniques reveal two different behaviours for the rotation frequency of transient spiral arms like structures. Whereas unbarred discs present spiral arms nearly corotating with disc particles, strong barred models (bulged or bulgeless) quickly develop a bar-spiral structure dominant in density, with a pattern speed almost constant in radius. As the bar strength decreases the arm departs from bar rigid rotation and behaves similar to the unbarred case. In strong barred models, we detect in the frequency space other subdominant and slower modes at large radii, in agreement with previous studies, however, we also detect them in the configuration space. We propose that the distinctive behaviour of the dominant spiral modes can be exploited in order to constraint the nature of Galactic spiral arms by the astrometric survey Gaia and by 2D spectroscopic surveys like Calar Alto Legacy Integral Field Area Survey (CALIFA) and Mapping Nearby Galaxies at APO (MANGA) in external galaxies.

  12. 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.

  13. Dynamical effect of gas on spiral pattern speed in galaxies

    NASA Astrophysics Data System (ADS)

    Ghosh, Soumavo; Jog, Chanda J.

    2016-07-01

    In the density wave theory of spiral structure, the grand-design two-armed spiral pattern is taken to rotate rigidly in a galactic disc with a constant, definite pattern speed. The observational measurement of the pattern speed of the spiral arms, though difficult, has been achieved in a few galaxies such as NGC 6946, NGC 2997, and M 51 which we consider here. We examine whether the theoretical dispersion relation permits a real solution for wavenumber corresponding to a stable wave, for the observed rotation curve and the pattern speed values. We find that the disc when modelled as a stars-alone case, as is usually done in literature, does not generally give a stable density wave solution for the observed pattern speed. Instead the inclusion of the low velocity dispersion component, namely, gas, is essential to obtain a stable density wave. Further, we obtain a theoretical range of allowed pattern speeds that correspond to a stable density wave at a certain radius, and check that for the three galaxies considered, the observed pattern speeds fall in the respective prescribed range. The inclusion of even a small amount (˜15 per cent) of gas by mass fraction in the galactic disc is shown to have a significant dynamical effect on the dispersion relation and hence on the pattern speed that is likely to be seen in a real, gas-rich spiral galaxy.

  14. Star formation and evolution in spiral galaxies.

    NASA Technical Reports Server (NTRS)

    Quirk, W. J.; Tinsley, B. M.

    1973-01-01

    Evolutionary models for regions of M31 and M33 and the solar neighborhood are based on a stellar birthrate suggested by the dynamics of spiral structure: we assume that stars are formed very efficiently until the gas content reaches equilibrium at its present value, which takes about 1 b.y.; thereafter, the birthrate just equals the rate at which gas enters the system from stellar mass-loss or infall of intergalactic matter. Each model represents an average around a cylindrical-shell-shaped region, which is homogeneous and closed except for possible infall. The disk and spiral-arm populations only are considered. Each star is followed in the H-R diagram from the main sequence to death as an invisible remnant. Integrated magnitudes, colors, mass-to-light ratio (M/L), gas content, helium and metal abundance (Z), are computed in steps of 1 b.y.

  15. Two views of the Andromeda Galaxy H-alpha and far infrared

    NASA Technical Reports Server (NTRS)

    Devereux, Nicholas A.; Price, Rob; Wells, Lisa A.; Duric, Neb

    1994-01-01

    A complete H-alpha image of the Andromeda Galaxy (M31) is presented allowing the first direct measurement of the total H-alpha luminosity which is (7.3 +/- 2.4) x 10(exp 6) solar luminosity. The H-alpha emission is associated with three morphologically distinct components; a large scale star-forming ring, approximately 1.65 deg in diameter, contributing 66% of the total H-alpha emission, a bright nucleus contributing 6% of the total H-alpha emission with the remaining 28% contributed by a previously unidentified component of extended and filamentary H-alpha emission interior to the star forming ring. The correspondence between the H-alpha image and the Infrared Astronomy Satellite (IRAS) far-infrared high resolution image is striking when both are convolved to a common resolution of 105 arcsec. The close correspondence between the far-infrared and H-alpha images suggests a common origin for the two emissions. The star-forming ring contributes 70% of the far-infrared luminosity of M31. Evidence that the ring emission is energized by high mass stars includes the fact that peaks in the far-infrared emission coincide identically with H II regions in the H-alpha image. In addition, the far-infrared to H-alpha luminosity ratio within the star-forming ring is similar to what one would expect for H II regions powered by stars of spectral types ranging between O9 and B0. The origin of the filamentary H-alpha and far-infrared luminosity interior to the star-forming ring is less clear, but it is almost certainly not produced by high mass stars.

  16. THE VARIABLE STAR POPULATION OF THE GLOBULAR CLUSTER B514 IN THE ANDROMEDA GALAXY

    SciTech Connect

    Clementini, Gisella; Contreras, Rodrigo; Federici, Luciana; Cacciari, Carla; Merighi, Roberto; Fusi Pecci, Flavio; Smith, Horace A.; Catelan, Marcio; Marconi, Marcella; Kinemuchi, Karen; Pritzl, Barton J. E-mail: kuehncha@msu.ed E-mail: beers@pa.msu.ed E-mail: marcella@na.astro.i E-mail: kinemuchi@astro.ufl.ed

    2009-10-20

    A rich harvest of RR Lyrae stars has been identified for the first time in B514, a metal-poor ([Fe/H] approx- 1.95 +- 0.10 dex) globular cluster (GC) of the Andromeda galaxy (M31), based on Hubble Space Telescope Wide Field Planetary Camera 2 and Advanced Camera for Surveys time-series observations. We have detected and derived periods for 89 RR Lyrae stars (82 fundamental-mode, RRab, and 7 first-overtone, RRc, pulsators, respectively) among 161 candidate variables identified in the cluster. The average period of the RR Lyrae variables ((Pab) = 0.58 days and (Pc) = 0.35 days, for RRab and RRc pulsators, respectively) and the position in the period-amplitude diagram both suggest that B514 is likely an Oosterhoff type I cluster. This appears to be in disagreement with the general behavior of the metal-poor GCs in the Milky Way, which show instead Oosterhoff type II pulsation properties. The average apparent magnitude of the RR Lyrae stars sets the mean level of the cluster horizontal branch at (V(RR)) = 25.18 +- 0.02 (sigma = 0.16 mag, on 81 stars). By adopting a reddening E(B - V) = 0.07 +- 0.02 mag, the above metallicity and M {sub V} = 0.44 +- 0.05 mag for the RR Lyrae variables of this metallicity, we derive a distance modulus of mu{sub 0} = 24.52 +- 0.08 mag, corresponding to a distance of about 800 +- 30 kpc, based on a value of M {sub V} that sets mu{sub 0}(LMC)=18.52 mag.

  17. The ISLANDS Project. I. Andromeda XVI, An Extremely Low Mass Galaxy Not Quenched by Reionization

    NASA Astrophysics Data System (ADS)

    Monelli, Matteo; Martínez-Vázquez, Clara E.; Bernard, Edouard J.; Gallart, Carme; Skillman, Evan D.; Weisz, Daniel R.; Dolphin, Andrew E.; Hidalgo, Sebastian L.; Cole, Andrew A.; Martin, Nicolas F.; Aparicio, Antonio; Cassisi, Santi; Boylan-Kolchin, Michael; Mayer, Lucio; McConnachie, Alan; McQuinn, Kristen B. W.; Navarro, Julio F.

    2016-03-01

    Based on data aquired in 13 orbits of Hubble Space Telescope time, we present a detailed evolutionary history of the M31 dSph satellite Andromeda XVI, including its lifetime star formation history (SFH), the spatial distribution of its stellar populations, and the properties of its variable stars. And XVI is characterized by prolonged star formation activity from the oldest epochs until star formation was quenched ˜6 Gyr ago, and, notably, only half of the mass in stars of And XVI was in place 10 Gyr ago. And XVI appears to be a low-mass galaxy for which the early quenching by either reionization or starburst feedback seems highly unlikely, and thus it is most likely due to an environmental effect (e.g., an interaction), possibly connected to a late infall in the densest regions of the Local Group. Studying the SFH as a function of galactocentric radius, we detect a mild gradient in the SFH: the star formation activity between 6 and 8 Gyr ago is significantly stronger in the central regions than in the external regions, although the quenching age appears to be the same, within 1 Gyr. We also report the discovery of nine RR Lyrae (RRL) stars, eight of which belong to And XVI. The RRL stars allow a new estimate of the distance, (m - M)0 = 23.72 ± 0.09 mag, which is marginally larger than previous estimates based on the tip of the red giant branch. 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 #13028.

  18. Testing the dark matter origin of the WMAP-Planck haze with radio observations of spiral galaxies

    SciTech Connect

    Carlson, Eric; Linden, Tim; Profumo, Stefano; Hooper, Dan E-mail: dhooper@fnal.gov E-mail: profumo@ucsc.edu

    2013-07-01

    If the Galactic WMAP radio haze, as recently confirmed by Planck, is produced by dark matter annihilation or decay, similar diffuse radio halos should exist around other galaxies with physical properties comparable to the Milky Way. If instead the haze is due to an astrophysical mechanism peculiar to the Milky Way or to a transient event, a similar halo need not exist around all Milky Way ''twins''. We use radio observations of 66 spiral galaxies to test the dark matter origin of the haze. We select galaxies based on morphological type and maximal rotational velocity, and obtain their luminosities from a 1.49 GHz catalog and additional radio observations at other frequencies. We find many instances of galaxies with radio emission that is less than 5% as bright as naively expected from dark matter models that could produce the Milky Way haze, and at least 3 galaxies that are less than 1% as bright as expected, assuming dark matter distributions, magnetic fields, and cosmic ray propagation parameters equal to those of the Milky Way. For reasonable ranges for the variation of these parameters, we estimate the fraction of galaxies that should be expected to be significantly less bright in radio, and argue that this is marginally compatible with the observed distribution. While our findings therefore cannot rule out a dark matter origin for the radio haze at this time, we find numerous examples (including the Andromeda Galaxy) where, if dark matter is indeed the origin of the Milky Way haze, some mechanism must be in place to suppress the corresponding haze of the external galaxy. We point out that Planck data will offer opportunities to improve this type of constraint in a highly relevant frequency range and for a potentially larger set of candidate galaxies.

  19. Computer experiments on the structure and dynamics of spiral galaxies

    NASA Technical Reports Server (NTRS)

    Hohl, F.

    1972-01-01

    The evolution of an initially balanced rotating disk of stars with an initial velocity dispersion given by Toomre's local criterion was investigated by means of a computer model for isolated disks of stars. It was found that the disk is unstable against very large scale modes. A stable axisymmetric disk with a velocity dispersion much larger than that given by Toomre's criterion was generated. The final mass distribution for the disk gives a high density central core and a disk population of stars that is closely approximated by an exponential variation. Various methods and rates of cooling the hot axisymmetric disks were investigated. It was found that the cooling resulted in the development of two-arm spiral structures which persisted as long as cooling continued. An experiment was performed to induce spiral structure in a galaxy by means of the close passage of a companion galaxy. Parameters similar to those expected for M51 and its companion were used. It was found that because of the high velocity dispersion of the disturbed disk galaxy, only a weak two-arm spiral structure appeared. The evolution of a uniformly rotating disk galaxy which is a stationary solution of the collisionless Boltzmann equation was investigated for various values of the initial rms velocity dispersion. It was found that the disk becomes stable at a value of the velocity dispersion predicted by theory.

  20. Infrared emission and tidal interactions of spiral galaxies

    NASA Technical Reports Server (NTRS)

    Byrd, Gene G.

    1987-01-01

    Computer simulations of tidal interactions of spiral galaxies are used to attempt to understand recent discoveries about infrared (IR) emitting galaxies. It is found that the stronger tidal perturbation by a companion the more disk gas clouds are thrown into nucleus crossing orbits and the greater the velocity jumps crossing spiral arms. Both these tidally created characteristics would create more IR emission by high speed cloud collisions and more IR via effects of recently formed stars. This expectation at greater tidal perturbation matches the observation of greater IR emission for spiral galaxies with closer and/or more massive companions. The greater collision velocities found at stronger perturbations on the models will also result in higher dust temperature in the colliding clouds. In the IR pairs examined, most have only one member, the larger, detected and when both are detected, the larger is always the more luminous. In simulations and in a simple analytic description of the strong distance dependence of the tidal force, it is found that the big galaxy of a pair is more strongly affected than the small.

  1. Simulated ΛCDM analogues of the thin Plane of Satellites around the Andromeda galaxy are not kinematically coherent structures

    NASA Astrophysics Data System (ADS)

    Buck, Tobias; Dutton, Aaron A.; Macciò, Andrea V.

    2016-05-01

    A large fraction of the dwarf satellites orbiting the Andromeda galaxy are surprisingly aligned in a thin, extended and apparently kinematically coherent planar structure. Such a structure is not easily found in simulations based on the Cold Dark Matter model (ΛCDM). Using 21 high resolution cosmological simulations we analyse the kinematics of planes of satellites similar to the one around Andromeda. We find good agreement when co-rotation is characterized by the line-of-sight velocity. At the same time, when co-rotation is inferred by the angular momenta of the satellites, the planes are in agreement with the plane around our Galaxy. We find such planes to be common in our high concentration haloes. The number of co-rotating satellites obtained from the sign of the line-of-sight velocity shows large variations depending on the viewing angle and is consistent with that obtained from a sample with random velocities. We find that the clustering of angular momentum vectors of the satellites in the plane is a better measure of the kinematic coherence. Thus we conclude that the line-of-sight velocity is not well suited as a proxy for the kinematical coherence of the plane. Analysis of the kinematics of our planes shows a fraction of ˜30% chance aligned satellites. Tracking the satellites in the plane back in time reveals that these planes are a transient feature and not kinematically coherent as would appear at first sight. Thus we expect some of the satellites in the plane around Andromeda to have high velocities perpendicular to the plane.

  2. Simulated ΛCDM analogues of the thin plane of satellites around the Andromeda galaxy are not kinematically coherent structures

    NASA Astrophysics Data System (ADS)

    Buck, Tobias; Dutton, Aaron A.; Macciò, Andrea V.

    2016-08-01

    A large fraction of the dwarf satellites orbiting the Andromeda galaxy are surprisingly aligned in a thin, extended and apparently kinematically coherent planar structure. Such a structure is not easily found in simulations based on the cold dark matter model (ΛCDM). Using 21 high-resolution cosmological simulations, we analyse the kinematics of planes of satellites similar to the one around Andromeda. We find good agreement when co-rotation is characterized by the line-of-sight velocity. At the same time, when co-rotation is inferred by the angular momenta of the satellites, the planes are in agreement with the plane around our Galaxy. We find such planes to be common in our high-concentration haloes. The number of co-rotating satellites obtained from the sign of the line-of-sight velocity shows large variations depending on the viewing angle and is consistent with that obtained from a sample with random velocities. We find that the clustering of angular momentum vectors of the satellites in the plane is a better measure of the kinematic coherence. Thus we conclude that the line-of-sight velocity is not well suited as a proxy for the kinematical coherence of the plane. Analysis of the kinematics of our planes shows a fraction of ˜30 per cent chance-aligned satellites. Tracking the satellites in the plane back in time reveals that these planes are a transient feature and not kinematically coherent as would appear at first sight. Thus we expect some of the satellites in the plane around Andromeda to have high velocities perpendicular to the plane.

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

    NASA Astrophysics Data System (ADS)

    Gusev, A. S.

    2006-03-01

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

  4. Multicolor CCD photometry of six lenticular and spiral galaxies. Structure of the galaxies

    NASA Astrophysics Data System (ADS)

    Gusev, A. S.

    2006-03-01

    The results of multicolor surface photometry of the S0 galaxies NGC 524, NGC 1138, and NGC 7280 and the spiral galaxies NGC 532, NGC 783, and NGC 1589 are reported. U BV RI observations were acquired with the 1.5-m telescope of the Maidanak Observatory (Uzbekistan), while JHK data were taken from the 2MASS catalog. The overall structure of the galaxies is analyzed and the galaxy images decomposed into bulge and disk components. The parameters of the galaxy components—rings, bars, spiral arms, and dust lanes—are determined. The bulge/disk decompositions based on averaged one-dimensional photometric profiles yield incorrect parameters for the bulges of the S0-Sa galaxies with bars and/or rings, whose inner regions are dominated by the radiation of the bulge.

  5. Discovery of rare double-lobe radio galaxies hosted in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Singh, Veeresh; Ishwara-Chandra, C. H.; Sievers, Jonathan; Wadadekar, Yogesh; Hilton, Matt; Beelen, Alexandre

    2015-12-01

    Double-lobe radio galaxies in the local Universe have traditionally been found to be hosted in elliptical or lenticular galaxies. We report the discovery of four spiral-host double-lobe radio galaxies (J0836+0532, J1159+5820, J1352+3126, and J1649+2635) that are discovered by cross-matching a large sample of 187 005 spiral galaxies from SDSS DR7 (Sloan Digital Sky Survey Data Release 7) to the full catalogues of FIRST (Faint Images of the Radio Sky at Twenty-cm) and NVSS (NRAO VLA Sky Survey). J0836+0532 is reported for the first time. The host galaxies are forming stars at an average rate of 1.7-10 M⊙ yr-1 and possess supermassive black holes (SMBHs) with masses of a few times 108 M⊙. Their radio morphologies are similar to Fanaroff-Riley type II radio galaxies with total projected linear sizes ranging from 86 to 420 kpc, but their total 1.4-GHz radio luminosities are only in the range 1024-1025 W Hz-1. We propose that the formation of spiral-host double-lobe radio galaxies can be attributed to more than one factor, such as the occurrence of strong interactions, mergers, and the presence of unusually massive SMBHs, such that the spiral structures are not destroyed. Only one of our sources (J1649+2635) is found in a cluster environment, indicating that processes other than accretion through cooling flows e.g. galaxy-galaxy mergers or interactions could be plausible scenarios for triggering radio-loud active galactic nuclei activity in spiral galaxies.

  6. The black hole mass function derived from local spiral galaxies

    SciTech Connect

    Davis, Benjamin L.; Berrier, Joel C.; Shields, Douglas W.; Kennefick, Daniel; Kennefick, Julia; Seigar, Marc S.; Lacy, Claud H. S.; Hartley, Matthew T.

    2014-07-10

    We present our determination of the nuclear supermassive black hole (SMBH) mass function for spiral galaxies in the local universe, established from a volume-limited sample consisting of a statistically complete collection of the brightest spiral galaxies in the southern (δ < 0°) hemisphere. Our SMBH mass function agrees well at the high-mass end with previous values given in the literature. At the low-mass end, inconsistencies exist in previous works that still need to be resolved, but our work is more in line with expectations based on modeling of black hole evolution. This low-mass end of the spectrum is critical to our understanding of the mass function and evolution of black holes since the epoch of maximum quasar activity. The sample is defined by a limiting luminosity (redshift-independent) distance, D{sub L} = 25.4 Mpc (z = 0.00572) and a limiting absolute B-band magnitude, M{sub B}=−19.12. These limits define a sample of 140 spiral galaxies, with 128 measurable pitch angles to establish the pitch angle distribution for this sample. This pitch-angle distribution function may be useful in the study of the morphology of late-type galaxies. We then use an established relationship between the logarithmic spiral arm pitch angle and the mass of the central SMBH in a host galaxy in order to estimate the mass of the 128 respective SMBHs in this volume-limited sample. This result effectively gives us the distribution of mass for SMBHs residing in spiral galaxies over a lookback time, t{sub L} ≤ 82.1 h{sub 67.77}{sup −1} Myr and contained within a comoving volume, V{sub C} = 3.37 × 10{sup 4} h{sub 67.77}{sup −3} Mpc{sup 3}. We estimate that the density of SMBHs residing in spiral galaxies in the local universe is ρ=5.54{sub −2.73}{sup +6.55} × 10{sup 4} h{sub 67.77}{sup 3} M{sub ☉} Mpc{sup –3}. Thus, our derived cosmological SMBH mass density for spiral galaxies is Ω{sub BH}=4.35{sub −2.15}{sup +5.14} × 10{sup –7} h{sub 67.77}. Assuming that

  7. Evolution of Gas Across Spiral Arms in the Whirlpool Galaxy

    NASA Astrophysics Data System (ADS)

    Louie, Melissa Nicole

    To investigate the dynamic evolution of gas across spiral arms, we conducted a detailed study of the gas and star formation along the spiral arms in the Whirlpool Galaxy, M51. This nearby, face-on spiral galaxy provides a unique laboratory to study the relationship between gas dynamics and star formation. The textbook picture of interstellar medium (ISM) evolution is rapidly changing. Molecular gas was once believed to form along spiral arms from the diffuse atomic gas in the inter-arm regions. Star formation occurs within giant molecular clouds during spiral arm passage. Lastly, the molecular gas is photo-dissociated back into atomic gas by massive stars on the downstream side of the spiral arm. Recent evidence, however, is revealing a new picture of the interstellar medium and the process of star formation. We seek development of a new picture by studying the development and evolution of molecular gas and the role of large scale galactic dynamics in organizing the interstellar medium. This thesis begins by presenting work measuring the geometrical offsets between interstellar gas and recent star formation. Interstellar gas is traced by atomic hydrogen and carbon monoxide (CO). Star formation is traced by ionized hydrogen recombination lines and infrared emission from dust warmed by young bright stars. Measuring these offsets can help determine the underlying large scale galactic dynamics. Along the spiral arms in M51, offsets between CO and the star formation tracers suggest that gas is flowing through the spiral arms, but the offsets do not show the expected signature of a single pattern speed and imply a more complicated pattern. This thesis also examines the intermediate stages of gas evolution, by studying a denser component of the ISM closer to which stars will form. Only a small percent of the bulk molecular gas will become dense enough to form stars. HCN and HCO+ probe densities ˜104 cm-3, where as the bulk gas is 500 cm-3. This thesis looks at HCN and

  8. Photometry of the MASTER OT J004207.99+405501.1 = M31N 2015-01a Bright Nova in Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Shumkov, V.; Pruzhinskaya, M.; Tiurina, N.; Lipunov, V.; Gorbovskoy, E.; Balanutsa, P.; Denisenko, D.; Vladimirov, V.; Rufanov, A.; Kuznetsov, A.; Buckley, D.; Potter, S.; Kniazev, A.; Kotze, M.; Ivanov, K.; Gres, O.; Yazev, S.; Budnev, N.; Poleshchuk, V.; Konstantinov, E.; Tlatov, A.; Dormidontov, D.; Senik, V.; Parkhomenko, A.; Yurkov, V.; Sergienko, Y.; Varda, D.; Sinyakov, E.; Gabovich, A.; Krushinsky, V.; Zalozhnih, I.; Popov, A.; Bourdanov, A.; Shurpakov, S.

    2015-01-01

    MASTER OT J004207.99+405501.1 = M31N 2015-01a - Bright Nova in Andromeda Galaxy MASTER-Kislovodsk auto-detection system discovered PSN source at (RA, Dec) = 00h 42m 07.99s +40d 55m 01.1s on 2015-01-13.63235 UT (Shumkov et al., #6911.) .

  9. Metastudy of the Spiral Structure of Our Home Galaxy

    NASA Astrophysics Data System (ADS)

    Vallée, Jacques P.

    2002-02-01

    The current maps of the Milky Way disk still have large differences, much like early maps of the Earth's continents made in the 16th century had sizeable differences in the locations of continents and many areas labeled ``terra incognita.'' Exactly where are the spiral arms in our home Galaxy (in radius and longitude)? Here a meta-analysis is made of the recent (1995-2001) observational data on the pitch angle (p) and the number (m) of spiral arms in our home Galaxy. In order to clarify our image of the structure of the Milky Way, logarithmic model arms of the form ln(r/r0)=k(θ-θ0) are fitted to the observed tangents to the spiral arms and to the observed position angle (P.A.) of the Galaxy's central bar. The main results are that p=12deg inward and m=4, with logarithmic spiral arm parameters r0=2.3 kpc and θ0=0deg for the Norma arm. The value of θ0 for the other three arms is modeled by rotating the Norma arm in steps of 90°. These values are similar to those found by Ortiz & Lépine using earlier observational data, with some differences. The best model predicts an interarm distance near the Sun of S=2.5 kpc (from the Sagittarius to the Perseus arm) and a distance from the Sun to the Sagittarius arm of 0.9 kpc. These values are compared to our limited and uncertain data from the observed nearby spiral arms. These predicted values near the Sun differ substantially from the predictions of Ortiz & Lépine, as discussed in the text.

  10. Spitzer Observations of Extraplanar PAH Emission from Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Lehner, N.; Howk, J.

    We present Spitzer/IRAC observations of polycylic aromatic hydrocarbon (PAH) emission from interstellar material in the thick disks of normal spiral galaxies. These data show PAHs to be a common constituent of extraplanar material in spirals. The processes that displace this material from the interstellar disks of these systems do not destroy these very small grains. The dust emission features are present far above the galactic planes, extended up to about 2-4 kpc above the midplanes of the galaxies presented in this work. The total extent for which dust can be traced is about half the extent of the DIG. If it is not a sensitivity effect, this suggests that PAHs may be associated with a cold neutral medium that can not be supported at high z.

  11. Unstable spiral modes in disk-shaped galaxies

    PubMed Central

    Lau, Y. Y.; Lin, C. C.; Mark, James W.-K.

    1976-01-01

    The mechanisms for the maintenance and the excitation of trailing spiral modes of density waves in diskshaped galaxies, as proposed by Lin in 1969 and by Mark recently, are substantiated by an analysis of the gas-dynamical model of the galaxy. The self-excitation of the unstable mode in caused by waves propagating outwards from the corotation circle, which carry away angular momentum of a sign opposite to that contained in the wave system inside that circle. Specifically, a simple dispersion relationship is given as a definite integral, which allows the immediate determination of the pattern frequency and the amplification rate, once the basic galactic model is known. PMID:16592313

  12. Stellar populations in spiral galaxies: broadband versus spectroscopic viewpoints

    NASA Astrophysics Data System (ADS)

    MacArthur, Lauren Anne

    2006-06-01

    This thesis addresses the stellar population content in the bulges and disks of spiral galaxies using broad-band and spectroscopic data. The results can be used to constrain models of galaxy formation in addition to establishing a comprehensive, model-independent, picture of colour and line-index gradients in spiral galaxies. Building upon my Masters study of structural parameters in spiral galaxies, I use the largest collection of multi-band (optical and IR) surface brightness profiles for face-on and moderately-tilted galaxies to extract radial colour profiles. The colour gradients are then translated into age and metallicity gradients by comparison with stellar population synthesis (SPS) models considering a range of star formation histories, including recent bursts. Based on their integrated light, we find that high surface brightness (SB) regions of galaxies formed their stars earlier than lower SB ones, or at a similar epoch but on shorter timescale. At a given SB level, the star formation histories are modulated by the overall potential of the galaxy such that brighter/higher rotational velocity galaxies formed earlier. This formation "down-sizing" implied by our results is inconsistent with current implementations of semi-analytic structure formation models. In order to alleviate concerns that our colour gradients could be affected by dust reddening, we designed a similar spectroscopic investigation and explored the dust sensitivity of absorption-line indices. The latter test makes use of the latest SPS, models incorporating a multi-component model for the line and continuum attenuation due to dust. For quiescent stellar populations (e.g. spheroids and globular clusters), dust extinction effects are small for most indices with the exception of the 4000 Å break. For models with current star formation, many indices may suffer from dust reddening and any departures depend on age, dust distribution, and the effective optical depth. However, a number of useful

  13. Stellar populations in spiral galaxies: Broadband versus spectroscopic viewpoints

    NASA Astrophysics Data System (ADS)

    MacArthur, Lauren Anne

    This thesis addresses the stellar population content in the bulges and disks of spiral galaxies using broad-band and spectroscopic data. The results can be used to constrain models of galaxy formation in addition to establishing a comprehensive, model-independent, picture of colour and line-index gradients in spiral galaxies. Building upon my Masters study of structural parameters in spiral galaxies, I use the largest collection of multi-band (optical and IR) surface brightness profiles for face-on and moderately-tilted galaxies to extract radial colour profiles. The colour gradients are then translated into age and metallicity gradients by comparison with stellar population synthesis (SPS) models considering a range of star formation histories, including recent bursts. Based on their integrated light, we find that high surface brightness (SB) regions of galaxies formed their stars earlier than lower SB ones, or at a similar epoch but on shorter timescale. At a given SB level, the star formation histories are modulated by the overall potential of the galaxy such that brighter/higher rotational velocity galaxies formed earlier. This formation "down-sizing" implied by our results is inconsistent with current implementations of semi-analytic structure formation models. In order to alleviate concerns that our colour gradients could be affected by dust reddening, we designed a similar spectroscopic investigation and explored the dust sensitivity of absorption-line indices. The latter test makes use of the latest SPS, models incorporating a multi-component model for the line and continuum attenuation due to dust. For quiescent stellar populations (e.g. spheroids and globular clusters), dust extinction effects are small for most indices with the exception of the 4000 Å break. For models with current star formation, many indices may suffer from dust reddening and any departures depend on age, dust distribution, and the effective optical depth. However, a number of useful

  14. Tidally Induced Offset Disks in Magellanic Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Pardy, Stephen A.; D’Onghia, Elena; Athanassoula, E.; Wilcots, Eric M.; Sheth, Kartik

    2016-08-01

    Magellanic spiral galaxies are a class of one-armed systems that often exhibit an offset stellar bar and are rarely found around massive spiral galaxies. Using a set of N-body and hydrodynamic simulations, we consider a dwarf–dwarf galaxy interaction as the driving mechanism for the formation of this peculiar class of systems. We investigate here the relation between the dynamical, stellar, and gaseous disk center and the bar. In all our simulations the bar center always coincides with the dynamical center, while the stellar disk becomes highly asymmetric during the encounter, causing the photometric center of the Magellanic galaxy disk to become mismatched with both the bar and the dynamical center. The disk asymmetries persist for almost 2 Gyr, the time that it takes for the disk to be recentered with the bar, and well after the companion has passed. This explains the nature of the offset bar found in many Magellanic-type galaxies, including the Large Magellanic Cloud (LMC) and NGC 3906. In particular, these results, once applied to the LMC, suggest that the dynamical center should reside in the bar center instead of the H i center as previously assumed, pointing to a variation in the current estimate of the north component of the LMC proper motion.

  15. DISCOVERY OF THE FIRST METHANOL (CH{sub 3}OH) MASER IN THE ANDROMEDA GALAXY (M31)

    SciTech Connect

    Sjouwerman, Lorant O.; Murray, Claire E.; Pihlstroem, Ylva M.; Fish, Vincent L.; Araya, Esteban D.

    2010-12-01

    We present the first detection of a 6.7 GHz Class II methanol (CH{sub 3}OH) maser in the Andromeda galaxy (M31). The CH{sub 3}OH maser was found in a VLA survey during the fall of 2009. We have confirmed the methanol maser with the new EVLA, in operation since 2010 March, but were unsuccessful in detecting a water maser at this location. A direct application for this methanol maser is the determination of the proper motion of M31, such as was previously obtained with water masers in M33 and IC10. Unraveling the three-dimensional velocity of M31 would solve for the biggest unknown in the modeling of the dynamics and evolution of the Local Group of galaxies.

  16. An optical study of stars and dust in the Andromeda galaxy

    NASA Technical Reports Server (NTRS)

    Walterbos, R. A. M.; Kennicutt, R. C., Jr.

    1988-01-01

    The distribution of light in M 31 is characterized on the basis of the UBVR surface photometry reported by Walterbos and Kennicutt (1987). The results of the data analysis are presented in extensive graphs, maps, and tables and discussed in detail, considering the outer disk regions, the decomposition into bulge and disk, the global disk and bulge colors, and dust and gas in two spiral arms. Principal findings examined include: (1) position-angle changes at radial distances beyond about 18 kpc (consistent with SW disk warping); (2) a bulge profile well described by an r exp 1/4 power law; (3) a bulge contribution to total light of about 40 percent; (4) increasing blueness in the outer disk (color gradient 0.02 mag/kpc in B-R); (5) an extinction law similar to that for the Galaxy; and (6) a significant correlation between dust and H I distributions.

  17. Origin of cosmic rays in the spiral galaxy NGC 3310

    SciTech Connect

    Duric, N.

    1984-01-01

    The problem of cosmic ray production in the spiral galaxy NGC 3310 is addressed by analyzing and comparing optical and radio continuum data. Tentative results indicate that on global scales relativistic electrons may be produced in the shock front associated with the density wave while on local scales extreme population I objects may be producing them. It is inferred that the same conclusions apply to all cosmic rays produced in the disk. 9 references.

  18. Fundamental Mass-Spin-Morphology Relation Of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Obreschkow, D.; Glazebrook, K.

    2014-03-01

    This work presents high-precision measurements of the specific baryon angular momentum j b contained in stars, atomic gas, and molecular gas, out to >~ 10 scale radii, in 16 nearby spiral galaxies of the THINGS sample. The accuracy of these measurements improves on existing studies by an order of magnitude, leading to the discovery of a strong correlation between the baryon mass M b, j b, and the bulge mass fraction β, fitted by \\beta =-(0.34+/- 0.03)\\,lg\\,(j_bM_b^{-1}/[10^{-7}\\, kpc\\,km\\,s^{-1}\\,{M}_{\\odot }^{-1}])-(0.04+/- 0.01) on the full sample range of 0 <= β <~ 0.3 and 109 M ⊙ < M b < 1011 M ⊙. The corresponding relation for the stellar quantities M * and j * is identical within the uncertainties. These M-j-β relations likely originate from the proportionality between jM -1 and the surface density of the disk that dictates its stability against (pseudo-)bulge formation. Using a cold dark matter model, we can approximately explain classical scaling relations, such as the fundamental plane of spiral galaxies, the Tully-Fisher relation, and the mass-size relation, in terms of the M-j(-β) relation. These results advocate the use of mass and angular momentum as the most fundamental quantities of spiral galaxies.

  19. Formation and destruction of clouds and spurs in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Shetty, Rahul; Ostriker, E. C.

    We investigate the formation of clouds and substructure in spiral galaxies using high resolution global MHD simulations, including gas self gravity. Previously, local modeling by Kim and Ostriker (2002) has shown that self gravity and magnetic fields cause the growth of high density clumps in the spiral arms rather rapidly; subsequently, these clumps result in the formation of sheared, feather like structures in the interarms, known as spurs. Recently, Shetty and Ostriker (2006) performed global simulations and found that gas self gravity can cause the growth of sheared features regardless of the strength of the external spiral potential. However, a sufficiently strong spiral potential is required to produce arm clouds, as well as spurs, which are the filamentary structures distinctly associated with the spiral arms, having near-perpendicular intersections with the main dust lane. Here, we use higher resolution modeling to study the detailed properties of the clouds and spurs. We analyze the resulting masses, angular momenta, and magnetic fields of the clouds, and their relation to the background dynamics. We also include a feedback mechanism, representing turbulent forcing via supernovae, to destroy the clouds. We thus assess the role of turbulence on the clump properties. Further, we also follow how subsequent spur morphology evolves under quasi-steady conditions. This research is supported by the National Science Foundation under grant AST-0507315.

  20. Galaxy Zoo: spiral galaxy morphologies and their relation to the star-forming main sequence

    NASA Astrophysics Data System (ADS)

    Willett, Kyle; Schawinski, Kevin; Masters, Karen; Melvin, Tom; Skibba, Ramin A.; Nichol, Robert; Cheung, Edmond; Lintott, Chris; Simmons, Brooke D.; Kaviraj, Sugata; Keel, William C.; Fortson, Lucy; Galaxy Zoo volunteers

    2015-01-01

    We examine the relationship between stellar mass and star formation rate in disk galaxies at z<0.085, measuring different populations of spirals as classified by their kiloparsec-scale structure. The morphologies of disk galaxies are obtained from the Galaxy Zoo 2 project, which includes the number of spiral arms, the arm pitch angle, and the presence of strong galactic bars. We show that both the slope and dispersion of the star-forming main sequence (SFMS) is constant no matter what the morphology of the spiral disk. We also show that mergers (both major and minor), which represent the strongest conditions for increases in star formation at a constant mass, only boost the SFR above the main relation by 0.3 dex; this is a significant reduction over the increase seen in merging systems at higher redshifts (z > 1). Of the galaxies that do lie significantly above the SFMS in the local Universe, more than 50% are mergers, with a large contribution from the compact green pea galaxies. We interpret our results as evidence that the number and pitch angle of spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms for star formation or are completely overwhelmed by the combination of outflows and feedback.

  1. Galaxy And Mass Assembly (GAMA): stellar mass growth of spiral galaxies in the cosmic web

    NASA Astrophysics Data System (ADS)

    Alpaslan, Mehmet; Grootes, Meiert; Marcum, Pamela M.; Popescu, Cristina; Tuffs, Richard; Bland-Hawthorn, Joss; Brough, Sarah; Brown, Michael J. I.; Davies, Luke J. M.; Driver, Simon P.; Holwerda, Benne W.; Kelvin, Lee S.; Lara-López, Maritza A.; López-Sánchez, Ángel R.; Loveday, Jon; Moffett, Amanda; Taylor, Edward N.; Owers, Matt; Robotham, Aaron S. G.

    2016-04-01

    We look for correlated changes in stellar mass and star formation rate (SFR) along filaments in the cosmic web by examining the stellar masses and UV-derived SFRs of 1799 ungrouped and unpaired spiral galaxies that reside in filaments. We devise multiple distance metrics to characterize the complex geometry of filaments, and find that galaxies closer to the cylindrical centre of a filament have higher stellar masses than their counterparts near the periphery of filaments, on the edges of voids. In addition, these peripheral spiral galaxies have higher SFRs at a given mass. Complementing our sample of filament spiral galaxies with spiral galaxies in tendrils and voids, we find that the average SFR of these objects in different large-scale environments are similar to each other with the primary discriminant in SFR being stellar mass, in line with previous works. However, the distributions of SFRs are found to vary with large-scale environment. Our results thus suggest a model in which in addition to stellar mass as the primary discriminant, the large-scale environment is imprinted in the SFR as a second-order effect. Furthermore, our detailed results for filament galaxies suggest a model in which gas accretion from voids on to filaments is primarily in an orthogonal direction. Overall, we find our results to be in line with theoretical expectations of the thermodynamic properties of the intergalactic medium in different large-scale environments.

  2. The opacity of spiral disks from counts of distant galaxies.

    NASA Astrophysics Data System (ADS)

    Holwerda, B. W.; Gonzalez, R. A.; Allen, R. J.; van der Kruit, P. C.

    2004-12-01

    The numbers of distant galaxies seen in an HST image of a spiral galaxy is an indication of the average extinction by dust in the disk. This number of distant galaxies has to be calibrated for crowding effects and for this the ``Synthetic Field Method'' (SFM, Gonzalez et al. 1998) was developed. Synthetic fields are the science field with a dimmed Hubble Deep Field added. From the relation between the dimming and the number of synthetic galaxies, the average extinction in the science field can be derived. 32 HST/WFPC2 fields were analysed and from the numbers of distant galaxies an average radial extinction profile for spiral disks was constructed, for the whole sample, arm and disk regions and different Hubble types. When the average radial extinction profile is compared to the HI surface density profile, an estimate of the average gas-to-dust ratio as a function of radius can be obtained. The effects of the phase of the hydrogen and metallicity gradient in disks are discussed. The average radial extinction profile is compared to the light distribution of spiral disks. The relation between typical radii of light and dust and the relation between surface brightness and extinction is also explored. Combining the detailed images of dust emission from the Spitzer space telescope with the extinction measurements from counts in HST images could offer insight into the relative prominence of cold dust and possibly the dust geometry in the disk. Future work on dust extinction using the wealth of new imaging in the HST archive is briefly discussed. This research was supported by funding from STSCI, the Director's Discretionary Research Fund and the Kapteyn Institute.

  3. Photometric Properties of Face-on Isolated Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Bahr, Alexander; Epstein, P.; Durbala, A.

    2011-05-01

    We want to quantify the relative role of nature versus nurture in defining the observed properties of galaxies. In simpler terms we would like to disentangle the ``genetic'’ and the environmental influences in shaping the morphology of galaxies. In order to do that one needs to firstly define a zero-order baseline, i.e., a sample of galaxies that have been minimally perturbed by neighbors in the last few billion years of their existence. Such a sample has been produced and refined in different stages in the context of the AMIGA international project (www.iaa.es/AMIGA.html). The recent catalogue ``The All-Sky Catalog of Isolated Galaxies Selected from 2MASS'’ (Karachentseva, V. E. et al. 2010) allows us to complete and enrich the initial sample constructed within AMIGA with new objects, thus enhancing the statistical relevance of our study. Our focus is to define a subset of isolated disk spiral galaxies. We constrain the sample selection by: 1) orientation, restricting to almost face-on galaxies and 2) availability of good photometric images in SDSS. The goal is to ``dissect'’ (decompose) these galaxies in major components (disk, bulge, bars, etc.) and to study the properties of the components in a statistical context. Having a reasonable representation of all morphological types, we aim to test the bimodality of bulges and bars. We present a progress report of our work.

  4. An Accreting White Dwarf near the Chandrasekhar Limit in the Andromeda Galaxy

    NASA Technical Reports Server (NTRS)

    Tang, Sumin; Bildsten, Lars; Wolf, William M.; Li, K. L.; Kong, Albert K. H.; Cao, Yi; Cenko, S. Bradley; De Cia, Annalisa; Kasliwal, Mansi M.; Kulkarni, Shrinivas R.; Laher, Russ R.; Masci, Frank; Nugent, Peter E.; Perley, Daniel A.; Prince, Thomas A.; Surace, Jason

    2014-01-01

    The iPTF (Intermediate Palomar Transient Factory) detection of the most recent outburst of the recurrent nova system RX J0045.4+4154 in the Andromeda Galaxy has enabled the unprecedented study of a massive (mass is greater than 1.3 solar masses) accreting white dwarf (WD). We detected this nova as part of the near daily iPTF monitoring of M31 to a depth of R (red band-pass filter) approximately equal to magnitude 21 and triggered optical photometry, spectroscopy and soft X-ray monitoring of the outburst. Peaking at an absolute magnitude of MR (red, mid-infrared band-pass filter) equals magnitude -6.6, and with a decay time of 1 magnitude per day, it is a faint and very fast nova. It shows optical emission lines of He/N and expansion velocities of 1900 to 2600 kilometers per second 1-4 days after the optical peak. The Swift monitoring of the X-ray evolution revealed a supersoft source (SSS) with kT (energy: Boltzmann constant times temperature) (sub eff (effective)) approximately equal to 90-110 electronvolts that appeared within 5 days after the optical peak, and lasted only 12 days. Most remarkably, this is not the first event from this system, rather it is a recurrent nova with a time between outbursts of approximately 1 year, the shortest known. Recurrent X-ray emission from this binary was detected by ROSAT in 1992 and 1993, and the source was well characterized as a mass greater than 1.3 solar masses WD SSS. Based on the observed recurrence time between different outbursts, the duration and effective temperature of the SS phase, MESA models of accreting WDs allow us to constrain the accretion rate to mass greater than 1.7x10 (sup -7) solar masses per year and WD mass greater than 1.30 solar masses. If the WD keeps 30 percent of the accreted material, it will take less than a million years to reach core densities high enough for carbon ignition (if made of C/O) or electron capture (if made of O/Ne) to end the binary evolution.

  5. An accreting white dwarf near the Chandrasekhar limit in the Andromeda galaxy

    SciTech Connect

    Tang, Sumin; Bildsten, Lars; Wolf, William M.; Li, K. L.; Kong, Albert K. H.; Cao, Yi; Kulkarni, Shrinivas R.; Perley, Daniel A.; Prince, Thomas A.; Cenko, S. Bradley; De Cia, Annalisa; Kasliwal, Mansi M.; Laher, Russ R.; Surace, Jason; Nugent, Peter E.

    2014-05-01

    The intermediate Palomar Transient Factory (iPTF) detection of the most recent outburst of the recurrent nova (RN) system RX J0045.4+4154 in the Andromeda galaxy has enabled the unprecedented study of a massive (M > 1.3 M {sub ☉}) accreting white dwarf (WD). We detected this nova as part of the near-daily iPTF monitoring of M31 to a depth of R ≈ 21 mag and triggered optical photometry, spectroscopy and soft X-ray monitoring of the outburst. Peaking at an absolute magnitude of M{sub R} = –6.6 mag, and with a decay time of 1 mag per day, it is a faint and very fast nova. It shows optical emission lines of He/N and expansion velocities of 1900-2600 km s{sup –1} 1-4 days after the optical peak. The Swift monitoring of the X-ray evolution revealed a supersoft source (SSS) with kT {sub eff} ≈ 90-110 eV that appeared within 5 days after the optical peak, and lasted only 12 days. Most remarkably, this is not the first event from this system, rather it is an RN with a time between outbursts of approximately 1 yr, the shortest known. Recurrent X-ray emission from this binary was detected by ROSAT in 1992 and 1993, and the source was well characterized as a M > 1.3 M {sub ☉} WD SSS. Based on the observed recurrence time between different outbursts, the duration and effective temperature of the SS phase, MESA models of accreting WDs allow us to constrain the accretion rate to M-dot >1.7×10{sup −7} M{sub ⊙} yr{sup −1} and WD mass >1.30 M {sub ☉}. If the WD keeps 30% of the accreted material, it will take less than a Myr to reach core densities high enough for carbon ignition (if made of C/O) or electron capture (if made of O/Ne) to end the binary evolution.

  6. An Accreting White Dwarf near the Chandrasekhar Limit in the Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Tang, Sumin; Bildsten, Lars; Wolf, William M.; Li, K. L.; Kong, Albert K. H.; Cao, Yi; Cenko, S. Bradley; De Cia, Annalisa; Kasliwal, Mansi M.; Kulkarni, Shrinivas R.; Laher, Russ R.; Masci, Frank; Nugent, Peter E.; Perley, Daniel A.; Prince, Thomas A.; Surace, Jason

    2014-05-01

    The intermediate Palomar Transient Factory (iPTF) detection of the most recent outburst of the recurrent nova (RN) system RX J0045.4+4154 in the Andromeda galaxy has enabled the unprecedented study of a massive (M > 1.3 M ⊙) accreting white dwarf (WD). We detected this nova as part of the near-daily iPTF monitoring of M31 to a depth of R ≈ 21 mag and triggered optical photometry, spectroscopy and soft X-ray monitoring of the outburst. Peaking at an absolute magnitude of MR = -6.6 mag, and with a decay time of 1 mag per day, it is a faint and very fast nova. It shows optical emission lines of He/N and expansion velocities of 1900-2600 km s-1 1-4 days after the optical peak. The Swift monitoring of the X-ray evolution revealed a supersoft source (SSS) with kT eff ≈ 90-110 eV that appeared within 5 days after the optical peak, and lasted only 12 days. Most remarkably, this is not the first event from this system, rather it is an RN with a time between outbursts of approximately 1 yr, the shortest known. Recurrent X-ray emission from this binary was detected by ROSAT in 1992 and 1993, and the source was well characterized as a M > 1.3 M ⊙ WD SSS. Based on the observed recurrence time between different outbursts, the duration and effective temperature of the SS phase, MESA models of accreting WDs allow us to constrain the accretion rate to \\dot{M} \\gt 1.7\\times 10^{-7}\\ {M_{\\odot }\\ yr}^{-1} and WD mass >1.30 M ⊙. If the WD keeps 30% of the accreted material, it will take less than a Myr to reach core densities high enough for carbon ignition (if made of C/O) or electron capture (if made of O/Ne) to end the binary evolution.

  7. IN-SPIRALING CLUMPS IN BLUE COMPACT DWARF GALAXIES

    SciTech Connect

    Elmegreen, Bruce G.; Zhang Hongxin; Hunter, Deidre A.

    2012-03-10

    Giant star formation clumps in dwarf irregular galaxies can have masses exceeding a few percent of the galaxy mass enclosed inside their orbital radii. They can produce sufficient torques on dark matter halo particles, halo stars, and the surrounding disk to lose their angular momentum and spiral into the central region in 1 Gyr. Pairs of giant clumps with similarly large relative masses can interact and exchange angular momentum to the same degree. The result of this angular momentum loss is a growing central concentration of old stars, gas, and star formation that can produce a long-lived starburst in the inner region, identified with the blue compact dwarf (BCD) phase. This central concentration is proposed to be analogous to the bulge in a young spiral galaxy. Observations of star complexes in five local BCDs confirm the relatively large clump masses that are expected for this process. The observed clumps also seem to contain old field stars, even after background light subtraction, in which case the clumps may be long-lived. The two examples with clumps closest to the center have the largest relative clump masses and the greatest contributions from old stars. An additional indication that the dense central regions of BCDs are like bulges is the high ratio of the inner disk scale height to the scale length, which is comparable to 1 for four of the galaxies.

  8. Most Massive Spiral Galaxy Known in the Universe

    NASA Astrophysics Data System (ADS)

    2000-12-01

    The VLT Observes Rapid Motion in Distant Object Summary The most massive spiral galaxy known so far in the Universe has been discovered by a team of astronomers from Garching, Padova, Leiden, ESO and London [1]. They base their conclusion on recent observations with ISAAC , an infrared-sensitive, multi-mode instrument on ESO's Very Large Telescope at the Paranal Observatory. This galaxy has been designated ISOHDFS 27 and is located at a distance of approx. 6 billion light-years (the redshift is 0.58). Its measured mass is more than 1000 billion times that of the Sun [2]. It is thus about four times more massive than our own galaxy, the Milky Way, and twice as heavy as the heaviest spiral galaxy known so far. The determination of the mass of ISOHDFS 27 is based on a unique measurement of the motions of its stars and nebulae around the center. The faster the motion is, the greater is the mass. It is, in essence, the same method that allows determining the mass of the Earth from the orbital speed and distance of the Moon. This is the first time a "rotation curve" has been observed in such a distant galaxy by means of infrared observations, allowing a very detailed dynamical study. Other observations by the team concern a pair of distant, interacting galaxies that were also found to possess comparably high masses. They also have observations of a third galaxy at a distance of about 10 billion light-years, with a mass that approaches that of ISOHDFS 27 . The new result has important cosmological implications, as it demonstrates that very heavy structures had already been formed in the Universe at a comparatively early epoch . PR Photo 33a/00 : ISOHDFS 27 , the heaviest spiral galaxy known. PR Photo 33b/00 : The "raw" ISAAC spectrum of ISOHDFS 27 . PR Photo 33c/00 : H-alpha profile of ISOHDFS 27 . Star formation in young galaxies It is of fundamental importance to current cosmological studies to understand how stars evolve within galaxies and how the galaxies themselves

  9. The ultraviolet attenuation law in backlit spiral galaxies

    SciTech Connect

    Keel, William C.; Manning, Anna M.; Holwerda, Benne W.; Lintott, Chris J.; Schawinski, Kevin E-mail: ammanning@bama.ua.edu E-mail: Twitter@BenneHolwerda E-mail: Twitter@chrislintott E-mail: Twitter@kevinschawinski

    2014-02-01

    The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet (UV) regime is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use Galaxy Evolution Explorer, XMM Optical Monitor, and Hubble Space Telescope (HST) data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with the candidate list of pairs provided by Galaxy Zoo participants. New optical images help to constrain the geometry and structure of the target galaxies. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. The entire sample has an attenuation law across the optical and UV that is close to the Calzetti et al. form; the UV slope for the overall sample is substantially shallower than found by Wild et al., which is a reasonable match to the more distant galaxies in our sample but not to the weighted combination including NGC 2207. The nearby, bright spiral NGC 2207 alone gives an accuracy almost equal to the rest of our sample, and its outer arms have a very low level of foreground starlight. Thus, this widespread, fairly 'gray' law can be produced from the distribution of dust alone, without a necessary contribution from differential escape of stars from dense clouds. Our results indicate that the extrapolation needed to compare attenuation between backlit galaxies at moderate redshifts from HST data, and local systems from Sloan Digital Sky Survey and similar data, is mild enough to allow the use of galaxy overlaps to trace the cosmic history of dust in galaxies. For NGC 2207, HST data in the near-UV F336W band show that the covering factor of clouds with small optical attenuation becomes a dominant factor farther into the UV, which opens the possibility that widespread

  10. Automated Quantification of Arbitrary Arm-Segment Structure in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Davis, Darren Robert

    This thesis describes a system that, given approximately-centered images of spiral galaxies, produces quantitative descriptions of spiral galaxy structure without the need for per-image human input. This structure information consists of a list of spiral arm segments, each associated with a fitted logarithmic spiral arc and a pixel region. This list-of-arcs representation allows description of arbitrary spiral galaxy structure: the arms do not need to be symmetric, may have forks or bends, and, more generally, may be arranged in any manner with a consistent spiral-pattern center (non-merging galaxies have a sufficiently well-defined center). Such flexibility is important in order to accommodate the myriad structure variations observed in spiral galaxies. From the arcs produced from our method it is possible to calculate measures of spiral galaxy structure such as winding direction, winding tightness, arm counts, asymmetry, or other values of interest (including user-defined measures). In addition to providing information about the spiral arm "skeleton" of each galaxy, our method can enable analyses of brightness within individual spiral arms, since we provide the pixel regions associated with each spiral arm segment. For winding direction, arm tightness, and arm count, comparable information is available (to various extents) from previous efforts; to the extent that such information is available, we find strong correspondence with our output. We also characterize the changes to (and invariances in) our output as a function of modifications to important algorithm parameters. By enabling generation of extensive data about spiral galaxy structure from large-scale sky surveys, our method will enable new discoveries and tests regarding the nature of galaxies and the universe, and will facilitate subsequent work to automatically fit detailed brightness models of spiral galaxies.

  11. 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.

  12. Energetic constraints to chemo-photometric evolution of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Buzzoni, Alberto

    2011-08-01

    galaxies; (iii) although lower-mass galaxies tend more likely to take the look of later-type spirals, it is mass, not morphology, that drives galaxy chemical properties. Facing the relatively flat trend of ? versus galaxy type, the increasingly poorer gas metallicity, as traced by the [O/H] abundance of H II regions along the Sa → Im Hubble sequence, seems to be mainly the result of the softening process, that dilute enriched stellar mass within a larger fraction of residual gas. The problem of the residual lifetime for spiral galaxies as active star-forming systems has been investigated. If returned mass is left as the main (or unique) gas supplier to the ISM, as implied by the Roberts time-scale, then star formation might continue only at a maximum birthrate bmax≪f/(1 -f) ≲ 0.45, for a Salpeter IMF. As a result, only massive (Mgal≳ 1011 M⊙) Sa/Sb spirals may have some chance to survive ˜30 per cent or more beyond a Hubble time. Things may be worse, on the contrary, for dwarf systems, that seem currently on the verge of ceasing their star formation activity unless to drastically reduce their apparent birthrate below the bmax threshold.

  13. Galaxy NGC 55

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This image of the nearby edge-on spiral galaxy NGC 55 was taken by Galaxy Evolution Explorer on September 14, 2003, during 2 orbits. This galaxy lies 5.4 million light years from our Milky Way galaxy and is a member of the 'local group' of galaxies that also includes the Andromeda galaxy (M31), the Magellanic clouds, and 40 other galaxies. The spiral disk of NGC 55 is inclined to our line of sight by approximately 80 degrees and so this galaxy looks cigar-shaped. This picture is a combination of Galaxy Evolution Explorer images taken with the far ultraviolet (colored blue) and near ultraviolet detectors, (colored red). The bright blue regions in this image are areas of active star formation detected in the ultraviolet by Galaxy Evolution Explorer. The red stars in this image are foreground stars in our own Milky Way galaxy.

  14. Short-term dynamical evolution of grand-design spirals in barred galaxies

    NASA Astrophysics Data System (ADS)

    Baba, Junichi

    2015-12-01

    We investigate the short-term dynamical evolution of stellar grand-design spiral arms in barred spiral galaxiesusing a three-dimensional (3D) N-body/hydrodynamic simulation. Similar to previous numerical simulations of unbarred, multiple-arm spirals, we find that grand-design spiral arms in barred galaxies are not stationary, but rather dynamic. This means that the amplitudes, pitch angles, and rotational frequencies of the spiral arms are not constant, but change within a few hundred million years (i.e. the typical rotational period of a galaxy). We also find that the clear grand-design spirals in barred galaxies appear only when the spirals connect with the ends of the bar. Furthermore, we find that the short-term behaviour of spiral arms in the outer regions (R > 1.5-2 bar radius) can be explained by the swing amplification theory and that the effects of the bar are not negligible in the inner regions (R < 1.5-2 bar radius). These results suggest that although grand-design spiral arms in barred galaxies are affected by the stellar bar, the grand-design spiral arms essentially originate not as bar-driven stationary density waves, but rather as self-excited dynamic patterns. We imply that a rigidly rotating grand-design spiral could not be a reasonable dynamical model for investigating gas flows and cloud formation even in barred spiral galaxies.

  15. Analysis of the Spiral Properties in Prototype Galaxies

    NASA Astrophysics Data System (ADS)

    Russell, William Stuart

    Numerical methods and algorithms are developed for analyzing the distribution of pitch angles of global and local spiral structure in disk-shaped galaxies. From the distribution of gas clouds and young stellar associations, "partitioning" methods based on nearest neighbor and Voronoi polyhedra calculations are applied to capture regions of high population density associated with local arm segments, spurs, feathers and secondary features. The pitch angle and length of each of these features are determined using least squares procedures applied in logarithmic spiral coordinates. The spectrum of pitch angles for both prototype and observed galaxies is analyzed and discussed. The evolution of prominent secondary features is examined over a 40 Myr period and characteristic behavior is interpreted in terms of competing mechanisms such as differential rotation and the gravitational force field induced by nearby features. A refined numerical method is also presented for modeling the self-gravity force field arising in prototype galaxy simulations. The loss of resolution from previous methods is compared to results obtained using high order finite differencing and modified bicubic interpolation. ftn*This work was supported in part under W. W. Roberts' grants from the National Science Foundation (Grant AST-87-12084) and NASA (Grant NAGW-929). The computational work was carried out on the CDC 855 and the AMSUN 3/260 cluster at the University of Virginia and the CRAY Y-MP at the Pittsburgh Superconducting Center (Grant AST880019P: W. W. Roberts, P.I.).

  16. Kinematic and Structural Evolution of Field and Cluster Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Ziegler, B. L.; Kutdemir, E.; Da Rocha, C.; Böhm, A.; Peletier, R. F.; Verdugo, M.

    2010-10-01

    To understand the processes that build up galaxies we investigate the stellar structure and gas kinematics of spiral and irregular galaxies out to redshift 1. We target 92 galaxies in four cluster ( z = 0.3 & 0.5 ) fields to study the environmental influence. Their stellar masses derived from multiband VLT/FORS photometry are distributed around but mostly below the characteristic Schechter-fit mass. From HST/ACS images we determine morphologies and structural parameters like disk length, position angle and ellipticity. Combining the spectra of three slit positions per galaxy using the MXU mode of VLT/FORS2 we construct the two-dimensional velocity field from gas emission lines for 16 cluster members and 33 field galaxies. The kinematic position angle and flatness are derived by a Fourier expansion of elliptical velocity profiles. To trace possible interaction processes, we define three irregularity indicators based on an identical analysis of local galaxies from the SINGS project. Our distant sample displays a higher fraction of disturbed velocity fields with varying percentages (10%, 30% and 70%) because they trace different features. While we find far fewer candidates for major mergers than the SINS sample at z ˜ 2, our data are sensitive enough to trace less violent processes. Most irregular signatures are related to star formation events and less massive disks are affected more than Milky-Way type objects. We detect similarly high fractions of irregular objects both for the distant field and cluster galaxies with similar distributions. We conclude that we may witness the building-up of disk galaxies still at redshifts z ˜ 0.5 via minor mergers and gas accretion, while some cluster members may additionally experience stripping, evaporation or harassment interactions.

  17. The interstellar halo of spiral galaxies: NGC 891

    NASA Technical Reports Server (NTRS)

    Kulkarni, Shrinivas R.; Rand, R. J.; Hester, J. Jeff

    1990-01-01

    Researchers have detected the Warm Ionized Medium (WIM) phase in the galaxy NGC 891. They found that the radial distribution of the WIM follows the molecular or young star distribution - an expected dependence. The amount of the WIM in this galaxy exceeds that in our Galaxy. The major surprize is the large thickness of the WIM phase - about 9 kpc instead 3 kpc as in our Galaxy. Clearly, this is the most significant result of the observations. The presence of low ionization gas at high z as well as at large galactocentric radii (where young stars are rare) is an important clue to the origin of the halo and observations such as the one reported here provide important data on this crucial question. In particular, the ionization of gas at high absolute z implies that either the UV photons manage to escape from the disk of the galaxy or that the extragalactic UV background plays an important role. The bulk of the WIM in spiral galaxies is a result of star-formation activity and thus these results can be understood by invoking a high star formation rate in NGC 891. Only the concerted action of supernovae can get the gas to the large z-heights as is observed in this galaxy. Support for this view comes from our detection of many worms i.e., bits and pieces of supershells in the form of kilo-parsec long vertical filaments. Researchers also saw a 600-pc size supershell located nearly one kpc above the plane of the galaxy.

  18. An Optical Search For Supernova Remnants in Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Matonick, D. M.; Fesen, R. A.; Blair, W. P.; Long, K. S.

    1994-12-01

    Imaging with narrow-band Hα , [S II], and red continuum filters has been used to distinguish supernova remnant (SNR) candidates from photoionized nebulae in seven nearby spiral galaxies: NGC 2403, NGC 3031 (M81), NGC 5194 (M51), NGC 5204, NGC 5457 (M101), NGC 5585, and NGC 6946. Nebulae which show [S II]/Hα > 0.45, indicating shock-heated emission, are identified as SNR candidates. The number of SNRs found in each galaxy using this technique is 3 in NGC 5204, 5 in NGC 5585, 30 in NGC 2403, 32 in M81, 35 in NGC 6946, and 112 in M101. Spectra of some of the emission nebulae have also been obtained, and were used to confirm SNR identifications. Because of its comparatively high radial velocity, M51 could not be examined adequately with our filter set; however, one bright SNR was found and spectroscopically confirmed. In NGC 2403, we obtained spectra on remnant candidates 1 and 2 of D'Odorico et al. (1980, A&AS, 40, 67), and confirmed them to be SNRs. We also detect the optical SNR identified by Blair & Fesen (1994, ApJ, 424, L103) in NGC 6946, and find an optical SNR counterpart to the X-ray source S2 identified by Schlegel (1994, ApJ, 424, L99). Sizes of observed SNRs range from unresolved (< 50 pc) to over 300x150 pc for one object in NGC 5585. Although our search technique limits our detection of SNRs embedded in bright H II regions, in the galaxies with clearly defined spiral arms (i.e NGC 6946, M81, M101), most SNRs appear to trace the spiral arms. Analysis of luminosity functions, diameters, abundances, and distributions of the samples of SNRs will also be discussed.

  19. Fundamental mass-spin-morphology relation of spiral galaxies

    SciTech Connect

    Obreschkow, D.; Glazebrook, K.

    2014-03-20

    This work presents high-precision measurements of the specific baryon angular momentum j {sub b} contained in stars, atomic gas, and molecular gas, out to ≳ 10 scale radii, in 16 nearby spiral galaxies of the THINGS sample. The accuracy of these measurements improves on existing studies by an order of magnitude, leading to the discovery of a strong correlation between the baryon mass M {sub b}, j {sub b}, and the bulge mass fraction β, fitted by β=−(0.34±0.03) lg (j{sub b}M{sub b}{sup −1}/[10{sup −7} kpc km s{sup −1} M{sub ⊙}{sup −1}])−(0.04±0.01) on the full sample range of 0 ≤ β ≲ 0.3 and 10{sup 9} M {sub ☉} < M {sub b} < 10{sup 11} M {sub ☉}. The corresponding relation for the stellar quantities M {sub *} and j {sub *} is identical within the uncertainties. These M-j-β relations likely originate from the proportionality between jM {sup –1} and the surface density of the disk that dictates its stability against (pseudo-)bulge formation. Using a cold dark matter model, we can approximately explain classical scaling relations, such as the fundamental plane of spiral galaxies, the Tully-Fisher relation, and the mass-size relation, in terms of the M-j(-β) relation. These results advocate the use of mass and angular momentum as the most fundamental quantities of spiral galaxies.

  20. Iron emission line from the spiral galaxy M 101

    NASA Astrophysics Data System (ADS)

    Yamauchi, Shigeo

    2016-06-01

    Archival Suzaku data of the face-on spiral galaxy M 101 were analyzed. An intense emission line at 6.72^{+0.10}_{-0.12}keV was detected in the central region. This line is identified with a K-line from He-like iron, which indicates the existence of a thin thermal plasma with a temperature of several keV. The iron line luminosity within the central 5'-radius region is estimated to be (2-12) × 1037 erg s-1. The origin of the iron emission line is discussed.

  1. The Spiral Wave of Our Galaxy Near Inner Lindblad Resonance

    PubMed Central

    Mark, James W-K.

    1971-01-01

    The dispersion relationship for short-wavelength spiral density waves in our Galaxy has been refined to remove the divergences that occurred in wave number and in amplitude as inner Lindblad resonance is approached. The wave is found to be evanescent in an annular region near 4 kpc. By 3 kpc, the inward propagating trailing wave is completely absorbed. The outgoing leading wave is suppressed compared to the trailing one because it begins in the evanescent state. Throughout this region of inner Lindblad resonance, a smooth wave amplitude has been obtained, and it has a sharp peak correlating well with the observed density of ionized hydrogen. PMID:16591941

  2. Evolution of Field Spiral Galaxies up to Redshifts z = 1

    NASA Astrophysics Data System (ADS)

    Böhm, Asmus; Ziegler, Bodo L.

    2007-10-01

    We have gained intermediate-resolution spectroscopy with the FORS instruments of the Very Large Telescope (VLT) and high-resolution imaging with the Advanced Camera for Surveys aboard HST for a sample of 220 distant field spiral galaxies within the FORS Deep Field and William Herschel Deep Field. Spatially resolved rotation curves were extracted and fitted with synthetic velocity fields that take into account all geometric and observational effects, such as blurring due to the slit width and seeing influence. Using these fits, the maximum rotation velocity Vmax could be determined for 124 galaxies that cover the redshift range 0.1spirals to very late types and irregulars. The luminosity-rotation velocity distribution of this sample, which represents an average look-back time of ~5 Gyr, is offset from the Tully-Fisher relation (TFR) of local low-mass spirals, whereas the distant high-mass spirals are compatible with the local TFR. Taking the magnitude-limited character of our sample into account, we show that the slope of the local and the intermediate- z TFR would be in compliance if its scatter decreased by more than a factor of 3 between z~0.5 and 0. Accepting this large evolution of the TFR scatter, we hence find no strong evidence for a mass- or luminosity-dependent evolution of disk galaxies. On the other hand, we derive stellar mass-to-luminosity ratios (M/L) that indicate a luminosity-dependent evolution in the sense that distant low-luminosity disks have much lower M/L than their local counterparts, while high-luminosity disks barely evolved in M/L over the covered redshift range. This could be the manifestation of the ``downsizing'' effect, i.e., the successive shift of the peak of star formation from high-mass to low-mass galaxies toward lower redshifts. This trend might be canceled out in the TF diagram due to the simultaneous evolution of multiple parameters. We also estimate the ratios

  3. Kinematic classification of non-interacting spiral galaxies

    NASA Astrophysics Data System (ADS)

    Wiegert, Theresa; English, Jayanne

    2014-01-01

    Using neutral hydrogen (HI) rotation curves of 79 galaxies, culled from the literature, as well as measured from HI data, we present a method for classifying disk galaxies by their kinematics. In order to investigate fundamental kinematic properties we concentrate on non-interacting spiral galaxies. We employ a simple parameterized form for the rotation curve in order to derive the three parameters: the maximum rotational velocity, the turnover radius and a measure of the slope of the rotation curve beyond the turnover radius. Our approach uses the statistical Hierarchical Clustering method to guide our division of the resultant 3D distribution of galaxies into five classes. Comparing the kinematic classes in this preliminary classification scheme to a number of galaxy properties, we find that our class containing galaxies with the largest rotational velocities has a mean morphological type of Sb/Sbc while the other classes tend to later types. Other trends also generally agree with those described by previous researchers. In particular we confirm correlations between increasing maximum rotational velocity and the following observed properties: increasing brightness in B-band, increasing size of the optical disk (D25) and increasing star formation rate (as derived using radio continuum data). Our analysis also suggests that lower velocities are associated with a higher ratio of the HI mass over the dynamical mass. Additionally, three galaxies exhibit a drop in rotational velocity amplitude of ≳20% after the turnover radius. However recent investigations suggest that they have interacted with minor companions which is a common cause for declining rotation curves.

  4. Spiral galaxy HI models, rotation curves and kinematic classifications

    NASA Astrophysics Data System (ADS)

    Wiegert, Theresa B. V.

    Although galaxy interactions cause dramatic changes, galaxies also continue to form stars and evolve when they are isolated. The dark matter (DM) halo may influence this evolution since it generates the rotational behaviour of galactic disks which could affect local conditions in the gas. Therefore we study neutral hydrogen kinematics of non-interacting, nearby spiral galaxies, characterising their rotation curves (RC) which probe the DM halo; delineating kinematic classes of galaxies; and investigating relations between these classes and galaxy properties such as disk size and star formation rate (SFR). To generate the RCs, we use GalAPAGOS (by J. Fiege). My role was to test and help drive the development of this software, which employs a powerful genetic algorithm, constraining 23 parameters while using the full 3D data cube as input. The RC is here simply described by a tanh-based function which adequately traces the global RC behaviour. Extensive testing on artificial galaxies show that the kinematic properties of galaxies with inclination >40 degrees, including edge-on galaxies, are found reliably. Using a hierarchical clustering algorithm on parametrised RCs from 79 galaxies culled from literature generates a preliminary scheme consisting of five classes. These are based on three parameters: maximum rotational velocity, turnover radius and outer slope of the RC. To assess the relationship between DM content and the kinematic classes, we generate mass models for 10 galaxies from the THINGS and WHISP surveys, and J. Irwin's sample. In most cases mass models using GalAPAGOS RCs were similar to those using traditional "tilted-ring'' method RCs. The kinematic classes are mainly distinguished by their rotational velocity. We confirm correlations between increasing velocity and B-magnitude, optical disk size, and find earlier type galaxies among the strong rotators. SFR also increases with maximum rotational velocity. Given our limited subsample, we cannot discern a

  5. The environmental dependence of neutral hydrogen content in spiral galaxies

    SciTech Connect

    Miner, Jesse; Rose, Jim; Kannappan, Sheila

    2008-08-01

    We present a study of the relationship between the deficiency of neutral hydrogen and the local three-dimensional number density of spiral galaxies in the Arecibo catalog [1] of global HI measurements. We find that the dependence on density of the HI content is weak at low densities, but increases sharply at high densities where interactions between galaxies and the intra-cluster medium become important. This behavior is reminiscent of the morphology-density relation [2] in that the effect manifests itself only at cluster-type densities, and indeed when we plot both the HI deficiency-density and morphology-density relations, we see that the densities at which they 'turn up' are similar. This suggests that the physical mechanisms responsible for the increase in early types in clusters are also responsible for the decrease in HI content.

  6. H II Regions in the Disks of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Rozas, M.

    1997-06-01

    The objective of the research presented in the thesis is to use photometrically calibrated high quality images in \\ha\\ of the disks of spiral galaxies to study their global star forming properties. In the first part of the study we catalog and study statistically the \\hii\\ regions in a set of spirals, imaged in \\ha\\ . The observed parameters of each region are its fluxes and diameters, from which we can also derive the mean surface brightness and its internal radial gradient (the latter for the largest most luminous regions). Plotting the luminosity function (LF) for a given galaxy (the number of regions versus \\ha\\ flux) we find a characteristic discontinuity: a peak accompanied by a change in gradient of the function, at a luminosity of 10$^{38.6}$ erg s$^{-1}$ per region. We attribute this to the change from ionization-bounded \\hii\\ regions, at luminosities below the transition, to density-bounded regions above the transition, and explain with a quantitative model based on this assumption why the transition takes place at a well-defined luminosity, and one which varies very little from galaxy to galaxy. In the six galaxies observed and analyzed in this way, the variance is 0.07 mag., making the transition a good prima facie candidate to be a powerful standard candle for accurate extragalactic distance measurements. Confirmation of the nature of the transition is provided by measurements of the internal brightness gradients, which show a jump from a constant value (predicted for ionization bounded regions) below the transition to a larger and increasing value above the transition. The theoretical model which can account for the transition was used to show how the gradients of the LF in the ionization bounded and the density bounded regimes can be used to derive the mass function of the ionizing stars in regions close to the transition luminosity, yielding a mean value for the slope of the MF in the galaxies observed of -2.4; the brightest stars in these

  7. Hot coronae around spiral galaxies: Probing the first principles of galaxy formation

    NASA Astrophysics Data System (ADS)

    Bogdán, Ákos; Forman, William; Volgelsberger, Mark; Mazzotta, Pasquale; Kraft, Ralph; Joes, Christine; Churazov, Eugene; Bourdin, Hervé

    2015-10-01

    The presence of hot gaseous coronae in the dark matter halos of massive spiral galaxies is a fundamental prediction of all structure formation models. Yet these coronae remained unexplored for several decades, thereby posing a serious challenge to observers and theorists. Although several X-ray coronae have been detected around nearby massive spiral galaxies in the past few years, we still lack a comprehensive picture. X-ray Surveyor will provide the much needed breakthrough. Specifically, X-ray Surveyor will characterize the hot coronae in unprecedented details, explore their evolution as a function of redshift, which in turn will constrain the physical processes that play an essential role in galaxy formation from the early Universe to the present epoch.

  8. Effects of spiral arms on star formation in nuclear rings of barred-spiral galaxies

    SciTech Connect

    Seo, Woo-Young; Kim, Woong-Tae E-mail: wkim@astro.snu.ac.kr

    2014-09-01

    We use hydrodynamic simulations to study the effect of spiral arms on the star formation rate (SFR) in nuclear rings of barred-spiral galaxies. We find that spiral arms can be an efficient means of gas transport from the outskirts to the central parts, provided that the arms are rotating slower than the bar. While the ring star formation in models with no arms or corotating arms is active only during around the bar growth phase, arm-driven gas accretion both significantly enhances and prolongs the ring star formation in models with slow-rotating arms. The arm-enhanced SFR is larger by a factor of ∼3-20 than in the no-arm model, with larger values corresponding to stronger and slower arms. Arm-induced mass inflows also make dust lanes stronger. Nuclear rings in slow-arm models are ∼45% larger than in the no-arm counterparts. Star clusters that form in a nuclear ring exhibit an age gradient in the azimuthal direction only when the SFR is small, whereas no notable age gradient is found in the radial direction for models with arm-induced star formation.

  9. Warp Characteristics of Spiral Galaxies in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Bae, Hyun-Jin; Chung, A.; Kim, S. S.; Jozsa, G. I. G.; Yoon, S.

    2012-01-01

    We present the warp characteristics of 22 spiral galaxies in the Virgo cluster based on their VLA HI datacubes with unprecedented precision. The tilted-ring modeling method is used to examine kinematic properties of the HI disks including the inclination and position angle. The main results are as follows. First, 17 out of the 19 (89.5 %) successfully-modeled galaxies exhibit either weak or strong warps, indicating that the warps are very common not only galaxies in isolation but ones in dense environments. Second, the warp strength decreases with increasing dynamical mass, supporting the notion that the warps are primarily controlled by dark matter halos. Last, the warp characteristics in our sample are distinct from those of isolated galaxies, in that the warps in our sample varies a great deal in inclination, but little in position angle. This implies that in dense environments, the main driver of the disk warps is most likely the galactic tidal interaction, rather than other explanations such as the cosmic infall scenario.

  10. HYDRODYNAMICAL SIMULATIONS OF THE BARRED SPIRAL GALAXY NGC 1097

    SciTech Connect

    Lin, Lien-Hsuan; Wang, Hsiang-Hsu; Hsieh, Pei-Ying; Taam, Ronald E.; Yang, Chao-Chin; Yen, David C. C.

    2013-07-01

    NGC 1097 is a nearby barred spiral galaxy believed to be interacting with the elliptical galaxy NGC 1097A located to its northwest. It hosts a Seyfert 1 nucleus surrounded by a circumnuclear starburst ring. Two straight dust lanes connected to the ring extend almost continuously out to the bar. The other ends of the dust lanes attach to two main spiral arms. To provide a physical understanding of its structural and kinematical properties, two-dimensional hydrodynamical simulations have been carried out. Numerical calculations reveal that many features of the gas morphology and kinematics can be reproduced provided that the gas flow is governed by a gravitational potential associated with a slowly rotating strong bar. By including the self-gravity of the gas disk in our calculation, we have found the starburst ring to be gravitationally unstable, which is consistent with the observation in Hsieh et al. Our simulations show that the gas inflow rate is 0.17 M{sub Sun} yr{sup -1} into the region within the starburst ring even after its formation, leading to the coexistence of both a nuclear ring and a circumnuclear disk.

  11. LACERTA I AND CASSIOPEIA III. TWO LUMINOUS AND DISTANT ANDROMEDA SATELLITE DWARF GALAXIES FOUND IN THE 3{pi} PAN-STARRS1 SURVEY

    SciTech Connect

    Martin, Nicolas F.; Laevens, Benjamin P. M.; Slater, Colin T.; Bell, Eric F.; Schlafly, Edward F.; Morganson, Eric; Rix, Hans-Walter; Bernard, Edouard J.; Ferguson, Annette M. N.; Finkbeiner, Douglas P.; Burgett, William S.; Chambers, Kenneth C.; Hodapp, Klaus W.; Kaiser, Nicholas; Kudritzki, Rolf-Peter; Magnier, Eugene A.; Morgan, Jeffrey S.; Tonry, John L.; Wainscoat, Richard J.; Price, Paul A.

    2013-07-20

    We report the discovery of two new dwarf galaxies, Lacerta I/Andromeda XXXI (Lac I/And XXXI) and Cassiopeia III/Andromeda XXXII (Cas III/And XXXII), in stacked Pan-STARRS1 r{sub P1}- and i{sub P1}-band imaging data. Both are luminous systems (M{sub V} {approx} -12) located at projected distances of 20. Degree-Sign 3 and 10. Degree-Sign 5 from M31. Lac I and Cas III are likely satellites of the Andromeda galaxy with heliocentric distances of 756{sup +44}{sub -28} kpc and 772{sup +61}{sub -56} kpc, respectively, and corresponding M31-centric distances of 275 {+-} 7 kpc and 144{sup +6}{sub -4} kpc. The brightest of recent Local Group member discoveries, these two new dwarf galaxies owe their late discovery to their large sizes (r{sub h} = 4.2{sup +0.4}{sub -0.5} arcmin or 912{sup +124}{sub -93} pc for Lac I; r{sub h} = 6.5{sup +1.2}{sub -1.0} arcmin or 1456 {+-} 267 pc for Cas III) and consequently low surface brightness ({mu}{sub 0} {approx} 26.0 mag arcsec{sup -2}), as well as to the lack of a systematic survey of regions at large radii from M31, close to the Galactic plane. This latter limitation is now alleviated by the 3{pi} Pan-STARRS1 survey, which could lead to the discovery of other distant Andromeda satellite dwarf galaxies.

  12. Distribution of Spiral Galaxies in the Virgo and Fornax Clusters and Their Dynamic Features

    NASA Astrophysics Data System (ADS)

    Kogoshvili, N. G.; Borchkhadze, T. M.; Kalloghlian, A. T.

    2014-12-01

    The dynamic characteristics of spiral galaxies with absolute magnitudes M ≥ -20m.6 in the Virgo and Fornax clusters are studied using data from the Merged Catalog of Galaxies MERCG. The galactic diameters from MERCG are used to determine the radius RD that defines the region of possible concentration of dark matter, and the dynamic parameters Mdyn and Mdyn/LB of the spiral galaxies are calculated based on the centrifugal equilibrium condition. Results from the theory of angular momentum transfer are used to estimate the central surface density m0 and angular momentum K of stars in these galaxies. A comparison of the dynamic parameters of the spiral galaxies with M ≥ -20.6 and M ≤ -20.6 reveals a statistically significant higher fraction of dark matter in the spiral galaxies with M ≤ -20.6, at 26.3% in Virgo and 27% in Fornax.

  13. Star formation in the outer disks of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Barnes, Kate Lynn

    I present results from a multi-wavelength study of star formation and the gaseous content in the outer disks of a sample of eight nearby spiral galaxies. In particular, the study focuses on galaxies with typical HI-to-optical sizes of ˜1--2, to provide a comparison to studies of galaxies with star formation occurring in extended gas disks. The study features new, ultra-deep ground-based H-alpha imaging and deep ultraviolet (UV) imaging from the GALEX space telescope to trace the recent star formation. I find that star formation typically extends through most (>85%) of the gas disk, with an outermost star forming regime characterized by low covering fractions and low star formation rate surface densities. The result that star formation extends through most of the gas disk regardless of the HI-to-optical size implies that it is important to further our understanding of the formation of extended gas disks to fully understand the implications of extended star forming disks. I find that the outer gaseous disks are gravitationally stable, which is in agreement with the lower level of star formation. I use ultraviolet and H-alpha colors to probe the recent star formation in the outer disks and find significant variations between colors of young stellar clusters. I run stellar population synthesis models to show how episodic star formation histories (SFHs) with periods of 100--250 Myr could cause similar color variations as are seen in outer disks. An episodic SFH would have implications for the gas depletion time and chemical evolution of spiral galaxies. In addition to an episodic SFH, the observed ultraviolet and H-alpha colors of young stellar clusters in the outer disks of galaxies in our sample are also in agreement with recently published models of a stochastically sampled initial mass function (IMF). Therefore, there remains some uncertainty for the possible cause of this observational result. Finally, we present a pilot study of deep, near infrared (NIR) imaging

  14. The nuclear region of the spiral galaxy M81.

    PubMed Central

    Bartel, N; Bietenholz, M F; Rupen, M P

    1995-01-01

    Very-long-baseline radio interferometry images of the nuclear region of the nearby spiral galaxy M81 reveal the most compact galactic core outside the Galaxy of which the size has been determined: 700 x 300 astronomical units (AU). The observations exclude a starburst or supernova interpretation for the core. Instead they favor an active galactic nucleus. There is evidence for a northeastern jet bent by approximately 35 degrees over a length scale from 700 to 4000 AU. The jet is, on average, directed toward an extended emission region, probably a radio lobe, about 1 kiloparsec (kpc) away from the core. A corresponding emission region was found in the southwest at a distance of only 30 pc from the core. The observed jet is extremely stable and likely to be associated with a steady-state channel. There is no detectable motion along the jet beyond the nominal value of -60 +/- 60 km.s-1. The level of activities in the core region of M81 is intermediate between that of SgrA* and that of powerful radio galaxies and quasars. Images Fig. 1 PMID:11607601

  15. STAR FORMATION IN THE OUTER DISK OF SPIRAL GALAXIES

    SciTech Connect

    Barnes, Kate L.; Van Zee, Liese; Cote, Stephanie; Schade, David E-mail: vanzee@astro.indiana.edu E-mail: David.Schade@nrc-cnrc.gc.ca

    2012-09-20

    We combine new deep and wide field of view H{alpha} imaging of a sample of eight nearby (d Almost-Equal-To 17 Mpc) spiral galaxies with new and archival H I and CO imaging to study the star formation and the star formation regulation in the outer disk. We find that, in agreement with previous studies, star formation in the outer disk has low covering fractions, and star formation is typically organized into spiral arms. The star formation in the outer disk is at extremely low levels, with typical star formation rate surface densities of {approx}10{sup -5} to 10{sup -6} M{sub Sun} yr{sup -1} kpc{sup -2}. We find that the ratio of the radial extent of detected H II regions to the radius of the H I disk is typically {approx}>85%. This implies that in order to further our understanding of the implications of extended star formation, we must further our understanding of the formation of extended H I disks. We measure the gravitational stability of the gas disk, and find that the outer gaseous disk is typically a factor of {approx}2 times more stable than the inner star-forming disk. We measure the surface density of outer disk H I arms, and find that the disk is closer to gravitational instability along these arms. Therefore, it seems that spiral arms are a necessary, but not sufficient, requirement for star formation in the outer disk. We use an estimation of the flaring of the outer gas disk to illustrate the effect of flaring on the Schmidt power-law index; we find that including flaring increases the agreement between the power-law indices of the inner and outer disks.

  16. The large-scale structure of the halo of the Andromeda galaxy. I. Global stellar density, morphology and metallicity properties

    SciTech Connect

    Ibata, Rodrigo A.; Martin, Nicolas F.; Lewis, Geraint F.; McConnachie, Alan W.; Irwin, Michael J.; Ferguson, Annette M. N.; Bernard, Edouard J.; Peñarrubia, Jorge; Babul, Arif; Navarro, Julio; Chapman, Scott C.; Collins, Michelle; Fardal, Mark; Mackey, A. D.; Rich, R. Michael; Tanvir, Nial; Widrow, Lawrence

    2014-01-10

    We present an analysis of the large-scale structure of the halo of the Andromeda galaxy, based on the Pan-Andromeda Archeological Survey (PAndAS), currently the most complete map of resolved stellar populations in any galactic halo. Despite the presence of copious substructures, the global halo populations follow closely power-law profiles that become steeper with increasing metallicity. We divide the sample into stream-like populations and a smooth halo component (defined as the population that cannot be resolved into spatially distinct substructures with PAndAS). Fitting a three-dimensional halo model reveals that the most metal-poor populations ([Fe/H]<−1.7) are distributed approximately spherically (slightly prolate with ellipticity c/a = 1.09 ± 0.03), with only a relatively small fraction residing in discernible stream-like structures (f {sub stream} = 42%). The sphericity of the ancient smooth component strongly hints that the dark matter halo is also approximately spherical. More metal-rich populations contain higher fractions of stars in streams, with f {sub stream} becoming as high as 86% for [Fe/H]>−0.6. The space density of the smooth metal-poor component has a global power-law slope of γ = –3.08 ± 0.07, and a non-parametric fit shows that the slope remains nearly constant from 30 kpc to ∼300 kpc. The total stellar mass in the halo at distances beyond 2° is ∼1.1 × 10{sup 10} M {sub ☉}, while that of the smooth component is ∼3 × 10{sup 9} M {sub ☉}. Extrapolating into the inner galaxy, the total stellar mass of the smooth halo is plausibly ∼8 × 10{sup 9} M {sub ☉}. We detect a substantial metallicity gradient, which declines from ([Fe/H]) = –0.7 at R = 30 kpc to ([Fe/H]) = –1.5 at R = 150 kpc for the full sample, with the smooth halo being ∼0.2 dex more metal poor than the full sample at each radius. While qualitatively in line with expectations from cosmological simulations, these observations are of great importance as

  17. Gas velocity patterns in simulated galaxies: Observational diagnostics of spiral structure theories

    NASA Astrophysics Data System (ADS)

    Baba, J.; Morokuma-Matsui, K.; Miyamoto, Y.; Egusa, F.; Kuno, N.

    2016-04-01

    There are two theories of stellar spiral arms in isolated disc galaxies that model stellar spiral arms with different longevities: quasi-stationary density wave theory, which characterises spirals as rigidly rotating, long-lived patterns (i.e. steady spirals), and dynamic spiral theory, which characterises spirals as differentially rotating, transient, recurrent patterns (i.e. dynamic spirals). In order to discriminate between these two spiral models observationally, we investigated the differences between the gas velocity patterns predicted by these two spiral models in hydrodynamic simulations. We found that the azimuthal phases of the velocity patterns relative to the gas density peaks (i.e. gaseous arms) differ between the two models, as do the gas flows; nevertheless, the velocity patterns themselves are similar for both models. Such similarity suggests that the mere existence of streaming motions does not conclusively confirm the steady spiral model. However, we found that the steady spiral model shows that the gaseous arms have radial streaming motions well inside the co-rotation radius, whereas the dynamic spiral model predicts that the gaseous arms tend to have tangential streaming motions. These differences suggest that the gas velocity patterns around spiral arms will enable distinction between the spiral theories.

  18. Gas velocity patterns in simulated galaxies: observational diagnostics of spiral structure theories

    NASA Astrophysics Data System (ADS)

    Baba, J.; Morokuma-Matsui, K.; Miyamoto, Y.; Egusa, F.; Kuno, N.

    2016-08-01

    There are two theories of stellar spiral arms in isolated disc galaxies that model stellar spiral arms with different longevities: quasi-stationary density wave theory, which characterizes spirals as rigidly rotating, long-lived patterns (i.e. steady spirals), and dynamic spiral theory, which characterizes spirals as differentially rotating, transient, recurrent patterns (i.e. dynamic spirals). In order to discriminate between these two spiral models observationally, we investigated the differences between the gas velocity patterns predicted by these two spiral models in hydrodynamic simulations. We found that the azimuthal phases of the velocity patterns relative to the gas density peaks (i.e. gaseous arms) differ between the two models, as do the gas flows; nevertheless, the velocity patterns themselves are similar for both models. Such similarity suggests that the mere existence of streaming motions does not conclusively confirm the steady spiral model. However, we found that the steady spiral model shows that the gaseous arms have radial streaming motions well inside the co-rotation radius, whereas the dynamic spiral model predicts that the gaseous arms tend to have tangential streaming motions. These differences suggest that the gas velocity patterns around spiral arms will enable distinction between the spiral theories.

  19. Star formation laws in the Andromeda galaxy: gas, stars, metals and the surface density of star formation

    NASA Astrophysics Data System (ADS)

    Rahmani, S.; Lianou, S.; Barmby, P.

    2016-03-01

    We use hierarchical Bayesian regression analysis to investigate star formation laws in the Andromeda galaxy (M31) in both local (30, 155 and 750 pc) and global cases. We study and compare the well-known Kennicutt-Schmidt law, the extended Schmidt law and the metallicity/star formation correlation. Using a combination of Hα and 24 μm emission, a combination of far-ultraviolet and 24 μm, and the total infrared emission, we estimate the total star formation rate (SFR) in M31 to be between 0.35 ± 0.04 and 0.4 ± 0.04 M⊙ yr-1. We produce a stellar mass surface density map using IRAC 3.6 μm emission and measured the total stellar mass to be 6.9 × 1010 M⊙. For the Kennicutt-Schmidt law in M31, we find the power-law index N to be between 0.49 and 1.18; for all the laws, the power-law index varies more with changing gas tracer than with SFR tracer. The power-law index also changes with distance from the centre of the galaxy. We also applied the commonly used ordinary least-squares fitting method and showed that using different fitting methods leads to different power-law indices. There is a correlation between the surface density of SFR and the stellar mass surface density, which confirms that the Kennicutt-Schmidt law needs to be extended to consider the other physical properties of galaxies. We found a weak correlation between metallicity, the SFR and the stellar mass surface density.

  20. The co-evolution of spiral structure and mass distribution in disk galaxies

    NASA Astrophysics Data System (ADS)

    Seigar, Marc

    2005-07-01

    We propose to use a new diagnostic tool to study the mass buildup in disk galaxies as a function of look-back time out to z 1. The tight correlation between spiral arm pitch angle and rotation curve shear rate {Seigar et al. 2005} demonstrates that the tightness of spiral structure in disk galaxies depends on the central mass concentration {including dark matter}, as this determines the shear rate. Galaxies with high central mass concentration have a higher shear rate and more tightly wound spiral structure than those with low mass concentration. As a result, the evolution of spiral structure over time can be used to search for evolution in the mass distribution in spiral galaxies. The main goal of this project is to determine evolution in the mass distribution of disk galaxies, using spiral arm pitch angles as a quanitative indicator. In order to do this we will use nearly face-on disk galaxies with measurable spiral structure, observed in the GOODS fields.

  1. A statistical analysis of the Einstein normal galaxy sample. I - Spiral and irregular galaxies

    NASA Technical Reports Server (NTRS)

    Fabbiano, G.; Trinchieri, G.

    1985-01-01

    The results of a statistical analysis of 48 spiral and irregular galaxies observed with the Einstein Observatory are reported. It is found that the X-ray luminosity is not directly correlated with the mass of the galaxies, but is strongly correlated with the blue luminosity. This suggests that most X-ray sources, including low-mass binaries, are binary systems belonging to both old disk and young arm Population I components. A real bulge population of X-ray sources exists that can contribute significantly to the X-ray luminosity of early-type spirals. The X-ray emission from a sample of 29 relatively isolated, normal elliptical and S0 galaxies is also studied, and the results are compared to those for the above sample to investigate the origin of the X-ray emission in early-type galaxies and the possible emission mechanisms. The influence of a powerful radio source and the onset of nuclear activity are also examined.

  2. Compact radio sources in the spiral galaxy M83

    NASA Astrophysics Data System (ADS)

    Soria, Roberto; Long, Knox S.; Winkler, P. Frank; Kuntz, Kip; Blair, William

    2011-04-01

    We are doing a multiband study of the stellar life cycle in the grand-design spiral galaxy M83, one of the most actively star-forming systems in the local Universe. We have already obtained exceptional optical coverage with HST and Magellan, and we have been awarded 750 ks of Chandra time this year. Now we propose an ATCA radio study, crucial for integrating the optical and X-ray studies. The radio study will allow us to achieve three main objectives: a) monitor the long-term evolution of three historical supernovae observed in M83 over the last 100 years, and hence constrain the late stages of evolution of their stellar progenitors; b) determine the distribution, radio spectral index and other physical properties of different types of young supernova remnants; c) resolve the morphology and search for variability of the nuclear sources: in particular, we will investigate the radio evidence for a double nucleus. In addition, we will study the aligned triple source just outside the nucleus: the traditional interpretation is that it is a background radio galaxy, but it has recently been suggested that it could be a recoiling nuclear black hole in M83.

  3. Numerical simulations of spiral galaxy formation and recoiling black holes

    NASA Astrophysics Data System (ADS)

    Guedes, Javiera M.

    expected to be common. Part 2 is dedicated to the formation of massive disk galaxies through N-body + SPH simulations. There, I describe the properties of Eris, the highest resolution cosmological simulation to date of the formation of a Milky Way-like galaxy from z = 90 to z = 0. Eris appears to solve the long-standing problems of mass concentration, which traditionally lead to the formation galaxies with large spheroidal components and small disks. A combination of high-resolution and high star formation threshold was the key to the success of Eris, because stars are only allowed to form at the highest density peaks and therefore feedback is more efficient in removing preferentially low angular momentum gas. Previous simulations tended to over-produce stars in low-density regions, where feedback is ineffective. Eris is in agreement with the Tully-Fischer, and M* - Mhalo relations, matches the observed surface brightness breaks in nearby spirals, is consistent with Sigma SFR - SigmaHI observations in spirals, and agrees with constraints on the hot gas mass abundance in the Galaxy. In addition, Eris' baryon fraction is 30% lower than the universal value, due to star formation driven outflows.

  4. Water Masers in the Andromeda Galaxy. I. A Survey for Water Masers, Ammonia, and Hydrogen Recombination Lines

    NASA Astrophysics Data System (ADS)

    Darling, Jeremy; Gerard, Benjamin; Amiri, Nikta; Lawrence, Kelsey

    2016-07-01

    We report the results of a Green Bank Telescope survey for water masers, ammonia (1, 1) and (2, 2), and the H66α recombination line toward 506 luminous compact 24 μm emitting regions in the Andromeda Galaxy (M31). We include the 206 sources observed in the Darling water maser survey for completeness. The survey was sensitive enough to detect any maser useful for ˜10 μas yr‑1 astrometry. No new water masers, ammonia lines, or H66α recombination lines were detected individually or in spectral stacks reaching rms noise levels of ˜3 mJy and ˜0.2 mJy, respectively, in 3.1–3.3 km s‑1 channels. The lack of detections in individual spectra and in the spectral stacks is consistent with Galactic extrapolations. Contrary to previous assertions, there do not seem to be any additional bright water masers to be found in M31. The strong variability of water masers may enable new maser detections in the future, but variability may also limit the astrometric utility of known (or future) masers because flaring masers must also fade.

  5. Water Masers in the Andromeda Galaxy. I. A Survey for Water Masers, Ammonia, and Hydrogen Recombination Lines

    NASA Astrophysics Data System (ADS)

    Darling, Jeremy; Gerard, Benjamin; Amiri, Nikta; Lawrence, Kelsey

    2016-07-01

    We report the results of a Green Bank Telescope survey for water masers, ammonia (1, 1) and (2, 2), and the H66α recombination line toward 506 luminous compact 24 μm emitting regions in the Andromeda Galaxy (M31). We include the 206 sources observed in the Darling water maser survey for completeness. The survey was sensitive enough to detect any maser useful for ∼10 μas yr‑1 astrometry. No new water masers, ammonia lines, or H66α recombination lines were detected individually or in spectral stacks reaching rms noise levels of ∼3 mJy and ∼0.2 mJy, respectively, in 3.1–3.3 km s‑1 channels. The lack of detections in individual spectra and in the spectral stacks is consistent with Galactic extrapolations. Contrary to previous assertions, there do not seem to be any additional bright water masers to be found in M31. The strong variability of water masers may enable new maser detections in the future, but variability may also limit the astrometric utility of known (or future) masers because flaring masers must also fade.

  6. On the Continuing Formation of the Andromeda Galaxy: Detection of H I Clouds in the M31 Halo

    NASA Astrophysics Data System (ADS)

    Thilker, David A.; Braun, Robert; Walterbos, René A. M.; Corbelli, Edvige; Lockman, Felix J.; Murphy, Edward; Maddalena, Ronald

    2004-01-01

    Green Bank Telescope 21 cm observations have revealed a faint, yet extensive H I cloud population surrounding the Andromeda galaxy (M31). The newfound objects are likely analogs to the high-velocity H I clouds seen around the Milky Way. At least 20 discrete features are detected within 50 kpc of the M31 disk, with radial velocities that are comparable to those of outer disk rotation. In addition, a filamentary ``halo'' component of at least 30 kpc extent is concentrated at the M31 systemic velocity. Some of the discrete features are organized into elongated systems with velocity continuity, suggestive of tidal streams. The discrete population can be characterized by a steep power-law distribution of number versus H I mass in the range between 105 and 107 Msolar. The velocity line width of discrete clouds is correlated with the cloud H I mass such that if the clouds are gravitationally bound this implies a dark matter to H I mass ratio of ~100:1. Possible origins for the discrete and halo M31 features include a LoGroup ``cooling flow,'' tidal debris from recent mergers or interactions, and the gaseous counterparts of low-mass dark matter halos.

  7. Spiral Galaxy Mass Models and the Distance Scale

    NASA Astrophysics Data System (ADS)

    Palunas, P.; Williams, T. B.

    1993-12-01

    We present mass models for a sample of Freeman Type I spiral galaxies taken from the southern sky Fabry-Perot Tully-Fisher survey(Schommer \\etal 1993, Bothun \\etal 1992). We fit two component, bulge and disk, photometric models directly to I- and R-band images. The bulge model is a series expansion of Gaussians (a Gabor expansion): each Gaussian in the series has a common center, ellipticity and position angle. The position angle is fixed to be the same as that of the disk. We have found that a deVaucouleurs law does not give a good fit to the bulges of many disk galaxies. The disk model is an exponential with the same center as the bulge. Small-scale radial structure is included in the disk mass model by azimuthally averaging the residuals of the analytic fit in annuli with the same ellipticity and position angle of the disk. Fitting to the full 2-d images helps constrain the disk-bulge deconvolution by using the information in the different ellipticities well as the different radial profiles of the disk and bulge. The photometric model is fitted to the rotation curve assuming a maximum disk and constant mass-to-light ratios for disk and bulge components. The small scale structure in the photometric models is found to reproduce the structure in the rotation curve in many galaxies. We find approximately 15 percent rms scatter in the I-band mass-to-light ratios, as well as correlations to the detailed properties of the kinematics indicating that mass-to-light ratios may be useful in reducing the scatter in the Tully-Fisher relation. Bothun, G.D., Schommer, R.A., Williams, T.B., Mould J.R., Huchra, J.P. 1992, Ap.J., 388, 253. Schommer, R.A., Bothun, G.D., Williams, T.B., Mould J.R. 1993, A.J., 105, 97.

  8. Gravitational torques in spiral galaxies: Gas accretion as a driving mechanism of galactic evolution

    NASA Astrophysics Data System (ADS)

    Block, D. L.; Bournaud, F.; Combes, F.; Puerari, I.; Buta, R.

    2002-11-01

    The distribution of gravitational torques and bar strengths in the local Universe is derived from a detailed study of 163 galaxies observed in the near-infrared. The results are compared with numerical models for spiral galaxy evolution. It is found that the observed distribution of torques can be accounted for only with external accretion of gas onto spiral disks. Accretion is responsible for bar renewal - after the dissolution of primordial bars - as well as the maintenance of spiral structures. Models of isolated, non-accreting galaxies are ruled out. Moderate accretion rates do not explain the observational results: it is shown that galactic disks should double their mass in less than the Hubble time. The best fit is obtained if spiral galaxies are open systems, still forming today by continuous gas accretion, doubling their mass every 10 billion years.

  9. Spectrophotometry of H II regions in the spiral galaxy M101

    PubMed Central

    Sedwick, K. E.; Aller, L. H.

    1981-01-01

    Spectral line intensity data are presented for ionized hydrogen regions in the giant spiral galaxy M101. The influence of interstellar extinction is assessed and electron temperatures of the gas clouds are derived. Images PMID:16592999

  10. Stellar Orbital Studies in Normal Spiral Galaxies. I. Restrictions to the Pitch Angle

    NASA Astrophysics Data System (ADS)

    Pérez-Villegas, A.; Pichardo, B.; Moreno, E.

    2013-08-01

    We built a family of non-axisymmetric potential models for normal non-barred or weakly barred spiral galaxies as defined in the simplest classification of galaxies: the Hubble sequence. For this purpose, a three-dimensional self-gravitating model for the spiral arm PERLAS is superimposed on the galactic axisymmetric potentials. We analyze the stellar dynamics varying only the pitch angle of the spiral arms, from 4° to 40° for an Sa galaxy, from 8° to 45° for an Sb galaxy, and from 10° to 60° for an Sc galaxy. Self-consistency is indirectly tested through periodic orbital analysis and through density response studies for each morphological type. Based on ordered behavior, periodic orbit studies show that, for pitch angles up to approximately 15°, 18°, and 20° for Sa, Sb, and Sc galaxies, respectively, the density response supports the spiral arms' potential, a requisite for the existence of a long-lasting large-scale spiral structure. Beyond those limits, the density response tends to "avoid" the potential imposed by maintaining lower pitch angles in the density response; in that case, the spiral arms may be explained as transient features rather than long-lasting large-scale structures. In a second limit, from a phase-space orbital study based on chaotic behavior, we found that for pitch angles larger than ~30°, ~40°, and ~50° for Sa, Sb, and Sc galaxies, respectively, chaotic orbits dominate the all phase-space prograde region that surrounds the periodic orbits sculpting the spiral arms and even destroying them. This result seems to be in good agreement with observations of pitch angles in typical isolated normal spiral galaxies.

  11. STELLAR ORBITAL STUDIES IN NORMAL SPIRAL GALAXIES. I. RESTRICTIONS TO THE PITCH ANGLE

    SciTech Connect

    Perez-Villegas, A.; Pichardo, B.; Moreno, E.

    2013-08-01

    We built a family of non-axisymmetric potential models for normal non-barred or weakly barred spiral galaxies as defined in the simplest classification of galaxies: the Hubble sequence. For this purpose, a three-dimensional self-gravitating model for the spiral arm PERLAS is superimposed on the galactic axisymmetric potentials. We analyze the stellar dynamics varying only the pitch angle of the spiral arms, from 4 Degree-Sign to 40 Degree-Sign for an Sa galaxy, from 8 Degree-Sign to 45 Degree-Sign for an Sb galaxy, and from 10 Degree-Sign to 60 Degree-Sign for an Sc galaxy. Self-consistency is indirectly tested through periodic orbital analysis and through density response studies for each morphological type. Based on ordered behavior, periodic orbit studies show that, for pitch angles up to approximately 15 Degree-Sign , 18 Degree-Sign , and 20 Degree-Sign for Sa, Sb, and Sc galaxies, respectively, the density response supports the spiral arms' potential, a requisite for the existence of a long-lasting large-scale spiral structure. Beyond those limits, the density response tends to ''avoid'' the potential imposed by maintaining lower pitch angles in the density response; in that case, the spiral arms may be explained as transient features rather than long-lasting large-scale structures. In a second limit, from a phase-space orbital study based on chaotic behavior, we found that for pitch angles larger than {approx}30 Degree-Sign , {approx}40 Degree-Sign , and {approx}50 Degree-Sign for Sa, Sb, and Sc galaxies, respectively, chaotic orbits dominate the all phase-space prograde region that surrounds the periodic orbits sculpting the spiral arms and even destroying them. This result seems to be in good agreement with observations of pitch angles in typical isolated normal spiral galaxies.

  12. SpArcFiRe: Scalable automated detection of spiral galaxy arm segments

    SciTech Connect

    Davis, Darren R.; Hayes, Wayne B. E-mail: whayes@uci.edu

    2014-08-01

    Given an approximately centered image of a spiral galaxy, we describe an entirely automated method that finds, centers, and sizes the galaxy (possibly masking nearby stars and other objects if necessary in order to isolate the galaxy itself) and then automatically extracts structural information about the spiral arms. For each arm segment found, we list the pixels in that segment, allowing image analysis on a per-arm-segment basis. We also perform a least-squares fit of a logarithmic spiral arc to the pixels in that segment, giving per-arc parameters, such as the pitch angle, arm segment length, location, etc. The algorithm takes about one minute per galaxies, and can easily be scaled using parallelism. We have run it on all ∼644,000 Sloan objects that are larger than 40 pixels across and classified as 'galaxies'. We find a very good correlation between our quantitative description of a spiral structure and the qualitative description provided by Galaxy Zoo humans. Our objective, quantitative measures of structure demonstrate the difficulty in defining exactly what constitutes a spiral 'arm', leading us to prefer the term 'arm segment'. We find that pitch angle often varies significantly segment-to-segment in a single spiral galaxy, making it difficult to define the pitch angle for a single galaxy. We demonstrate how our new database of arm segments can be queried to find galaxies satisfying specific quantitative visual criteria. For example, even though our code does not explicitly find rings, a good surrogate is to look for galaxies having one long, low-pitch-angle arm—which is how our code views ring galaxies. SpArcFiRe is available at http://sparcfire.ics.uci.edu.

  13. SpArcFiRe: Scalable Automated Detection of Spiral Galaxy Arm Segments

    NASA Astrophysics Data System (ADS)

    Davis, Darren R.; Hayes, Wayne B.

    2014-08-01

    Given an approximately centered image of a spiral galaxy, we describe an entirely automated method that finds, centers, and sizes the galaxy (possibly masking nearby stars and other objects if necessary in order to isolate the galaxy itself) and then automatically extracts structural information about the spiral arms. For each arm segment found, we list the pixels in that segment, allowing image analysis on a per-arm-segment basis. We also perform a least-squares fit of a logarithmic spiral arc to the pixels in that segment, giving per-arc parameters, such as the pitch angle, arm segment length, location, etc. The algorithm takes about one minute per galaxies, and can easily be scaled using parallelism. We have run it on all ~644,000 Sloan objects that are larger than 40 pixels across and classified as "galaxies." We find a very good correlation between our quantitative description of a spiral structure and the qualitative description provided by Galaxy Zoo humans. Our objective, quantitative measures of structure demonstrate the difficulty in defining exactly what constitutes a spiral "arm," leading us to prefer the term "arm segment." We find that pitch angle often varies significantly segment-to-segment in a single spiral galaxy, making it difficult to define the pitch angle for a single galaxy. We demonstrate how our new database of arm segments can be queried to find galaxies satisfying specific quantitative visual criteria. For example, even though our code does not explicitly find rings, a good surrogate is to look for galaxies having one long, low-pitch-angle arm—which is how our code views ring galaxies. SpArcFiRe is available at http://sparcfire.ics.uci.edu.

  14. A MOLECULAR SPIRAL ARM IN THE FAR OUTER GALAXY

    SciTech Connect

    Dame, T. M.; Thaddeus, P. E-mail: pthaddeus@cfa.harvard.edu

    2011-06-10

    We have identified a spiral arm lying beyond the Outer Arm in the first Galactic quadrant {approx}15 kpc from the Galactic center. After tracing the arm in existing 21 cm surveys, we searched for molecular gas using the CfA 1.2 m telescope and detected CO at 10 of 220 positions. The detections are distributed along the arm from l = 13{sup 0}, v = -21 km s{sup -1} to l = 55{sup 0}, v = -84 km s{sup -1} and coincide with most of the main H I concentrations. One of the detections was fully mapped to reveal a large molecular cloud with a radius of 47 pc and a molecular mass of {approx}50,000 M{sub sun}. At a mean distance of 21 kpc, the molecular gas in this arm is the most distant yet detected in the Milky Way. The new arm appears to be the continuation of the Scutum-Centaurus Arm in the outer Galaxy, as a symmetric counterpart of the nearby Perseus Arm.

  15. Spiral Galaxy Central Bulge Tangential Speed of Revolution Curves

    NASA Astrophysics Data System (ADS)

    Taff, Laurence

    2013-03-01

    The objective was to, for the first time in a century, scientifically analyze the ``rotation curves'' (sic) of the central bulges of scores of spiral galaxies. I commenced with a methodological, rational, geometrical, arithmetic, and statistical examination--none of them carried through before--of the radial velocity data. The requirement for such a thorough treatment is the paucity of data typically available for the central bulge: fewer than 10 observations and frequently only five. The most must be made of these. A consequence of this logical handling is the discovery of a unique model for the central bulge volume mass density resting on the positive slope, linear, rise of its tangential speed of revolution curve and hence--for the first time--a reliable mass estimate. The deduction comes from a known physics-based, mathematically valid, derivation (not assertion). It rests on the full (not partial) equations of motion plus Poisson's equation. Following that is a prediction for the gravitational potential energy and thence the gravitational force. From this comes a forecast for the tangential speed of revolution curve. It was analyzed in a fashion identical to that of the data thereby closing the circle and demonstrating internal self-consistency. This is a hallmark of a scientific method-informed approach to an experimental problem. Multiple plots of the relevant quantities and measures of goodness of fit will be shown. Astronomy related

  16. Scaling Relations in Dissipationless Spiral-Like Galaxy Mergers

    NASA Astrophysics Data System (ADS)

    Aceves, H.; Velázquez, H.; Cruz, F.

    2009-06-01

    We determine both representations of the Fundamental Plane [FP; R e vprop σ a 0langIrang-b e and R e vprop (σ2 0langIrang-1 e)λ] and the luminosity-effective phase-space density (L vprop f -γ e ) scaling relation for N-body remnants of binary mergers of spiral-like galaxies. The main set of merger simulations involves a mass ratio of the progenitors in the range of about 1:1 to 1:5, harboring or not a bulge-like component, and are constructed using a cosmological motivated model. Equal-mass mergers are also considered. Remnants lead to average values for the scaling indices of langarang ≈ 1.6, langbrang ≈ 0.6, langλrang ≈ 0.7, and langγrang ≈ 0.65. These values are consistent with those of K-band observations of ellipticals: langarang ≈ 1.5, langbrang ≈ 0.8, langλrang ≈ 0.7, and langγrang ≈ 0.60. The b index is, however, not well reproduced. This study does not allow us to establish a conclusive preference for models with or without a bulge as progenitors. Our results indicate that the L-f e and FP scalings might be determined to a large extent by dissipationless processes, a result that appears to be in contradiction to other dissipationless results.

  17. Near-infrared mapping of spiral barred galaxies

    NASA Technical Reports Server (NTRS)

    Gallais, P.; Rouan, D.; Lacombe, F.

    1990-01-01

    In external galaxies, near-infrared emission originates from stellar populations, hot dust, free-free emission from H+ regions, gaseous emission, non-thermal nucleus if any. Because of the low extinction compared to the visible, infrared wavelengths are useful to probe regions obscured by dust such as central parts where starburst phenomena can occur because of the large quantity of matter. The results presented were obtained with a 32 x 32 InSb charge injection device (CID) array cooled at 4K, at the f/36 cassegrain focus of the 3m60 Canada-France-Hawaii telescope with a spatial resolution of 0.5 inches per pixel. The objects presented are spiral barred galaxies mapped at J(1.25 microns), H(1.65 microns) and K(2.2 microns). The non-axisymetric potential due to the presence of a bar induces dynamical processes leading to the confinement of matter and peculiar morphologies. Infrared imaging is used to study the link between various components. Correlations with other wavelengths ranges and 2-colors diagrams ((J-H), (H-K)) lead to the identification of star forming regions, nucleus. Maps show structures connected to the central core. The question is, are they flowing away or toward the nucleus. Observations of M83 lead to several conclusions. The star forming region, detected in the visible and the infrared cannot be very compact and must extend to the edge of the matter concentration. The general shape of the near-infrared emission and the location of radio and 10 micron peaks suggest the confinement of matter between the inner Linblad resonances localized from CO measurements about 100 and 400 pc. The distribution of color indices in the arc from southern part to the star forming region suggests an increasing amount of gas and a time evolution eventually triggered by supernova explosions. Close to the direction of the bar, a bridge-like structure connects the arc to the nucleus with peculiar color indices. Perhaps, this structure can be linked to a height velocity

  18. The Effect of the Transformation of Spiral Galaxies in the Virgo Cluster on Broadband Color Evolution

    NASA Astrophysics Data System (ADS)

    Crowl, Hugh H.; Chung, A.; Blanton, M. R.; Kenney, J. D. P.; van Gorkom, J. H.; Schiminovich, D.

    2009-01-01

    Galaxy evolution and the effect of environment on that evolution is one of the central questions of modern extragalactic astronomy. The nearby Virgo Cluster provides us with an ideal laboratory to study galaxy-galaxy and galaxy-cluster interactions at a level of detail impossible at higher redshift. In detailed, pan-chromatic surveys of Virgo, we have seen galaxies transformed by their interaction with the intra-cluster medium, with star-forming gas stripped from spiral galaxies. Using data from the Sloan Digital Sky Survey, we present the results of a study of the global broadband optical properties of 44 Virgo Cluster spiral galaxies from the VIVA galaxy survey. These results show that spiral galaxies actively being stripped maintain blue colors while stripping is ongoing. However, a comparison between the colors of stripped spirals and their HI content suggests that more completely stripped galaxies are, indeed, redder than those that are only modestly HI deficient. This suggests that, as galaxies become more completely stripped, their global colors become redder and that in a cluster more massive than Virgo, such stripping could effectively transform galaxies from blue to red. By comparing broadband colors to the stripping timescales derived from optical spectroscopy and stellar population synthesis, we determine that the broadband color evolution is complex, with dust and the age of the stellar population both playing a role. By comparing detailed studies of a nearby cluster with statistical results from the much larger SDSS sample, we are able to gain insights into the details of how environmentally-driven galaxy evolution affects global broadband colors.

  19. Spirality: Spiral arm pitch angle measurement

    NASA Astrophysics Data System (ADS)

    Shields, Douglas W.; Boe, Benjamin; Pfountz, Casey; Davis, Benjamin L.; Hartley, Matthew; Pour Imani, Hamed; Slade, Zac; Kennefick, Daniel; Kennefick, Julia

    2015-12-01

    Spirality measures spiral arm pitch angles by fitting galaxy images to spiral templates of known pitch. Written in MATLAB, the code package also includes GenSpiral, which produces FITS images of synthetic spirals, and SpiralArmCount, which uses a one-dimensional Fast Fourier Transform to count the spiral arms of a galaxy after its pitch is determined.

  20. Dependence of Nebular Heavy-element Abundance on H I Content for Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Robertson, Paul; Shields, Gregory A.; Davé, Romeel; Blanc, Guillermo A.; Wright, Audrey

    2013-08-01

    We analyze the galactic H I content and nebular log (O/H) for 60 spiral galaxies in the Moustakas et al. (2006a) spectral catalog. After correcting for the mass-metallicity relationship, we show that the spirals in cluster environments show a positive correlation for log (O/H) on DEF, the galactic H I deficiency parameter, extending the results of previous analyses of the Virgo and Pegasus I clusters. Additionally, we show for the first time that galaxies in the field obey a similar dependence. The observed relationship between H I deficiency and galactic metallicity resembles similar trends shown by cosmological simulations of galaxy formation including inflows and outflows. These results indicate the previously observed metallicity-DEF correlation has a more universal interpretation than simply a cluster's effects on its member galaxies. Rather, we observe in all environments the stochastic effects of metal-poor infall as minor mergers and accretion help to build giant spirals.

  1. DEPENDENCE OF NEBULAR HEAVY-ELEMENT ABUNDANCE ON H I CONTENT FOR SPIRAL GALAXIES

    SciTech Connect

    Robertson, Paul; Shields, Gregory A.; Wright, Audrey; Dave, Romeel; Blanc, Guillermo A.

    2013-08-10

    We analyze the galactic H I content and nebular log (O/H) for 60 spiral galaxies in the Moustakas et al. (2006a) spectral catalog. After correcting for the mass-metallicity relationship, we show that the spirals in cluster environments show a positive correlation for log (O/H) on DEF, the galactic H I deficiency parameter, extending the results of previous analyses of the Virgo and Pegasus I clusters. Additionally, we show for the first time that galaxies in the field obey a similar dependence. The observed relationship between H I deficiency and galactic metallicity resembles similar trends shown by cosmological simulations of galaxy formation including inflows and outflows. These results indicate the previously observed metallicity-DEF correlation has a more universal interpretation than simply a cluster's effects on its member galaxies. Rather, we observe in all environments the stochastic effects of metal-poor infall as minor mergers and accretion help to build giant spirals.

  2. Galactic Scale Flows and the Triggering of Star Formation in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Ramón-Fox, F. G.; Bonnell, I. A.

    2016-06-01

    Galactic scale gas flows feed the growth of molecular clouds where stars form in high-density cores. Large scale flows also play a role in injecting the energy that drives the internal dynamics of these clouds, which affects their overall stability and star formation activity. The triggering of star formation involves a connection between large and small-scale dynamical processes in galaxies, which can be explored using high-resolution hydrodynamical simulations. We present results of current work in high-resolution N-body and Smoothed Particle Hydrodynamics simulations of a model spiral galaxy with a realistic spiral arm morphology. These simulations allow to study gas flows in a self-consistent galaxy and their role on molecular cloud formation and growth. They also provide a ground for studying molecular cloud properties in different environments of a galaxy, the effects of spiral arms on large scale flows and for understanding global star formation relations.

  3. Statistics of young starforming complexes in spiral galaxies using NIR photometry

    NASA Astrophysics Data System (ADS)

    Grosbøl, P.; Dottori, H.

    2008-10-01

    Aims: Very young stellar clusters and cluster complexes may be embedded in dust lanes along spiral arms in disk galaxies and escape detection in visual bands. Observations in the near-infrared K-band offer an almost unbiased view of such clusters or complexes due to the small attenuation by dust at this wavelength. The objective is to determine their population size, absolute K-band magnitude distribution above the limiting magnitude imposed by the data, and location relative to the spiral pattern in disk galaxies. Methods: All slightly extended sources were identified on deep K-band maps of 46 spiral galaxies reaching at least K=20.3 mag arcsec-2 at a signal-to-noise level of 3. The galaxies had inclination angles <65° and linear resolutions <100 pc with seeing better than 1 arcsec. The sample includes both barred and normal spirals with a wide spread in types. We also analyzed J- and H-band colors for 4 galaxies for which such images were available. An apparent magnitude limit of K = 19 mag was used for the sources analyzed in order to avoid marginal detections. Furthermore, we derived the source distributions of magnitudes and relative locations with respect to the spiral patterns. Results: Almost 70% (15/22) of the grand-design spiral galaxies show significant concentration of bright K-band knots in their arm regions corresponding to 30% (15/46) of the full sample. Color-color diagrams for the 4 spirals with JHK photometry suggest that a significant fraction of the diffuse sources found in the arms are complexes of young stellar clusters with ages <10 Myr and reddened with several magnitudes of visual extinction. The brightest knots reach an absolute K-band magnitude MK of -15.5 mag corresponding to stellar clusters or complexes with total masses up to at least 105 M⊙. Brightest magnitude and number of knots correlate with the total absolute magnitude of the host galaxy. More knots are seen in galaxies with high far-infrared flux and strong two-armed spiral

  4. Structure and Dynamics of Normal Spiral Galaxies: Stellar Orbital Order and Chaos

    NASA Astrophysics Data System (ADS)

    Perez Villegas, Maria de Los Angeles; Pichardo, B.

    2013-01-01

    We built a family of non-axisymmetric potential models for normal spiral galaxies as defined in the simplest classification of galaxies: the Hubble sequence. For this purpose a three-dimensional self-gravitating model for spiral arms (PERLAS) is superimposed to galactic axisymmetric potentials. We analyze the orbital dynamics as a function of pitch angle, ranging from 4° to 40°, for an Sa galaxy, from 8° to 45°, for an Sb galaxy, and from 10° to 60°, for an Sc galaxy. Self-consistency is indirectly tested through periodic orbital analysis, and through density response studies for each morphological type. Based on ordered behavior, periodic orbits studies show that for pitch angles up to approximately 15°, 18°, and 20° for Sa, Sb and Sc galaxies, respectively, the density response closely supports the imposed potential likely allowing the existence of a long-lasting spiral structure. Beyond those limits, the density response tends to ``avoid'' the potential imposed by keeping smaller pitch angles in the density response, in these cases the spiral arms could not be explained as long-lasting structures, but they would rather be explained as transient features. On the other hand, from an extensive orbital study in phase space based on chaotic behavior, we also find that for Sa galaxies with pitch angles lager than ˜30°, for Sb galaxies with pitch angles lager than ˜40°, and for Sc galaxies with pitch angles larger than ˜50°, chaos becomes pervasive, destroying the ordered phase space prograde region surrounding the main periodic orbits and even destroying them. This result seems to be in good agreement with observations of pitch angles in typical isolated normal spiral galaxies.

  5. Andromeda IV: A new local volume very metal-poor galaxy

    NASA Astrophysics Data System (ADS)

    Pustilnik, S. A.; Tepliakova, A. L.; Kniazev, A. Y.; Burenkov, A. N.

    2008-06-01

    And IV is a low surface brightness (LSB) dwarf galaxy at a distance of 6.1 Mpc, projecting close to M 31. In this paper the results of spectroscopy of the And IV two brightest HII regions with the SAO 6-m telescope (BTA) are presented. In spectra of both of them the faint line [OIII] λ4363 Å was detected and this allowed us to determine their O/H by the classical Te method. Their values for 12+log(O/H) are equal to 7.49±0.06 and 7.55±0.23, respectively. The comparison of the direct O/H calculations with the two most reliable semi-empirical and empirical methods shows the good consistency between these methods. For And IV absolute blue magnitude, MB = -12.6, our value for O/H corresponds to the ‘standard’ relation between O/H and LB for dwarf irregular galaxies (DIGs). And IV appears to be a new representative of the extremely metal-deficient gas-rich galaxies in the Local Volume. The very large range of M(HI) for LSB galaxies with close metallicities and luminosities indicates that simple models of LSBG chemical evolution are too limited to predict such striking diversity.

  6. Herschel-ATLAS/GAMA: dusty early-type galaxies and passive spirals

    NASA Astrophysics Data System (ADS)

    Rowlands, K.; Dunne, L.; Maddox, S.; Bourne, N.; Gomez, H. L.; Kaviraj, S.; Bamford, S. P.; Brough, S.; Charlot, S.; da Cunha, E.; Driver, S. P.; Eales, S. A.; Hopkins, A. M.; Kelvin, L.; Nichol, R. C.; Sansom, A. E.; Sharp, R.; Smith, D. J. B.; Temi, P.; van der Werf, P.; Baes, M.; Cava, A.; Cooray, A.; Croom, S. M.; Dariush, A.; de Zotti, G.; Dye, S.; Fritz, J.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Liske, J.; Loveday, J.; Madore, B.; Norberg, P.; Popescu, C. C.; Rigby, E. E.; Robotham, A.; Rodighiero, G.; Seibert, M.; Tuffs, R. J.

    2012-01-01

    We present the dust properties and star formation histories of local submillimetre-selected galaxies, classified by optical morphology. Most of the galaxies are late types and very few are early types. The early-type galaxies (ETGs) that are detected contain as much dust as typical spirals, and form a unique sample that has been blindly selected at submillimetre wavelengths. Additionally, we investigate the properties of the most passive, dusty spirals. We morphologically classify 1087 galaxies detected in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) Science Demonstration Phase data. Comparing to a control sample of optically selected galaxies, we find 5.5 per cent of luminous ETGs are detected in H-ATLAS. The H-ATLAS ETGs contain a significant mass of cold dust: the mean dust mass is 5.5 × 107 M⊙, with individual galaxies ranging from 9 × 105 to 4 × 108 M⊙. This is comparable to that of spiral galaxies in our sample, and is an order of magnitude more dust than that found for the control early-types, which have a median dust mass inferred from stacking of (0.8-4.0) × 106 M⊙ for a cold dust temperature of 25-15 K. The early-types detected in H-ATLAS tend to have bluer NUV - r colours, higher specific star formation rates and younger stellar populations than early-types which are optically selected, and may be transitioning from the blue cloud to the red sequence. We also find that H-ATLAS and control early-types inhabit similar low-density environments. We investigate whether the observed dust in H-ATLAS early-types is from evolved stars, or has been acquired from external sources through interactions and mergers. We conclude that the dust in H-ATLAS and control ETGs cannot be solely from stellar sources, and a large contribution from dust formed in the interstellar medium or external sources is required. Alternatively, dust destruction may not be as efficient as predicted. We also explore the properties of the most passive spiral

  7. A spiral galaxy's mass distribution uncovered through lensing and dynamics

    NASA Astrophysics Data System (ADS)

    Trick, Wilma H.; van de Ven, Glenn; Dutton, Aaron A.

    2016-09-01

    We investigate the matter distribution of a spiral galaxy with a counter-rotating stellar core, SDSS J1331+3628 (J1331), independently with gravitational lensing and stellar dynamical modelling. By fitting a gravitational potential model to a quadruplet of lensing images around J1331's bulge, we tightly constrain the mass inside the Einstein radius Rein = (0.91 ± 0.02)″( ≃ 1.83 ± 0.04~kpc) to within 4%: Mein = (7.8 ± 0.3) × 1010M⊙. We model observed long-slit major axis stellar kinematics in J1331's central regions by finding Multi-Gaussian Expansion (MGE) models for the stellar and dark matter distribution that solve the axisymmetric Jeans equations. The lens and dynamical model are independently derived, but in very good agreement with each other around ˜Rein. We find that J1331's center requires a steep total mass-to-light ratio gradient. A dynamical model including a NFW halo (with virial velocity v200 ≃ 240 ± 40~kms-1 and concentration c200 ≃ 8 ± 2) and moderate tangential velocity anisotropy (βz ≃ -0.4 ± 0.1) can reproduce the signatures of J1331's counter-rotating core and predict the stellar and gas rotation curve at larger radii. However, our models do not agree with the observed velocity dispersion at large radii. We speculate that the reason could be a non-trivial change in structure and kinematics due to a possible merger event in J1331's recent past.

  8. Supernovae and their host galaxies - IV. The distribution of supernovae relative to spiral arms

    NASA Astrophysics Data System (ADS)

    Aramyan, L. S.; Hakobyan, A. A.; Petrosian, A. R.; de Lapparent, V.; Bertin, E.; Mamon, G. A.; Kunth, D.; Nazaryan, T. A.; Adibekyan, V.; Turatto, M.

    2016-07-01

    Using a sample of 215 supernovae (SNe), we analyse their positions relative to the spiral arms of their host galaxies, distinguishing grand-design (GD) spirals from non-GD (NGD) galaxies. We find that: (1) in GD galaxies, an offset exists between the positions of Ia and core-collapse (CC) SNe relative to the peaks of arms, while in NGD galaxies the positions show no such shifts; (2) in GD galaxies, the positions of CC SNe relative to the peaks of arms are correlated with the radial distance from the galaxy nucleus. Inside (outside) the corotation radius, CC SNe are found closer to the inner (outer) edge. No such correlation is observed for SNe in NGD galaxies nor for SNe Ia in either galaxy class; (3) in GD galaxies, SNe Ibc occur closer to the leading edges of the arms than do SNe II, while in NGD galaxies they are more concentrated towards the peaks of arms. In both samples of hosts, the distributions of SNe Ia relative to the arms have broader wings. These observations suggest that shocks in spiral arms of GD galaxies trigger star formation in the leading edges of arms affecting the distributions of CC SNe (known to have short-lived progenitors). The closer locations of SNe Ibc versus SNe II relative to the leading edges of the arms supports the belief that SNe Ibc have more massive progenitors. SNe Ia having less massive and older progenitors, have more time to drift away from the leading edge of the spiral arms.

  9. Synthetic HI observations of spiral structure in the outer disk in galaxies

    NASA Astrophysics Data System (ADS)

    Khoperskov, Sergey A.; Bertin, Giuseppe

    2015-12-01

    > By means of 3D hydrodynamical simulations, in a separate paper we have discussed the properties of non-axisymmetric density wave trains in the outermost regions of galaxy disks, based on the picture that self-excited global spiral modes in the bright optical stellar disk are accompanied by low-amplitude short trailing wave signals outside corotation; in the gas, such wave trains can penetrate through the outer Lindblad resonance and propagate outwards, forming prominent spiral patterns. In this paper we present the synthetic 21 cm velocity maps expected from simulated models of the outer gaseous disk, focusing on the case when the disk is dominated by a two-armed spiral pattern, but considering also other more complex situations. We discuss some aspects of the spiral pattern in the gaseous periphery of galaxy disks noted in our simulations that might be interesting to compare with specific observed cases.

  10. Variations in Metallicity and Gas Content in Spiral Galaxies: Accidents of Infall

    NASA Astrophysics Data System (ADS)

    Shields, Gregory A.; Robertson, P.; Dave, R.; Blanc, G. A.; Wright, A.

    2013-01-01

    Oxygen abundances are elevated in hydrogen deficient spirals in the Virgo and Pegasus clusters (Robertson et al. 2012, ApJ 748:48, and references therein). We confirm the relationship between O/H and H I deficiency "DEF" for an additional set of cluster spirals. In addition, we find that field spirals show a similar increase in O/H with DEF. Thus, the relationship is not uniquely the result of environmental processes in clusters. Cosmological simulations of galaxy formation predict a qualitatively similar trend of O/H with DEF for field spirals. This reflects excursions of gas content and metallicity above and below the mean mass-metallicity relationship as galaxies evolve. These excursions result from the stochastic effects of mergers and merger-free periods during the evolution.

  11. Deep UV Imaging of Stripped Spiral Galaxies in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Crowl, Hugh

    We propose moderately deep GALEX observations (6 ksec) of eighteen gas-stripped Virgo Cluster spiral galaxies. These observations will give a complete sample of strongly stripped, highly inclined (i>70 degrees) Virgo spirals brighter than magnitude 16. Optical imaging and HI mapping show that these spirals all lack dust and gas in their outer disks, presumably due to ICM-ISM interactions. GALEX UV observations will provide critical information on how these interactions have affected recent star formation in the galaxies. The GALEX FUV and NUV data, particularly when combined with our existing multi-wavelength data set including broadband optical, H-alpha, and Spitzer IR imaging, and optical spectroscopy, will strongly constrain when a galaxy was stripped, how rapidly it was stripped, and the strength of any starburst at the time of stripping. The UV light changes dramatically over timescales of 0-500 Myr, which are the same timescales over which ICM-ISM interactions take place, making it possible to constrain the most recent effects of the cluster environment on galaxy evolution and if these effects can effectively drive the transformation of spirals into S0s. The deep imaging we propose will enable us to detect age gradients in the stellar populations of the outer disks, which will tell us how rapidly the galaxies are stripped. The cluster locations of recently stripped galaxies and the timescales over which the galaxies are stripped will allow us to constrain the relative importance of stripping that occurs during cluster core passages and stripping which occurs when galaxies encounter an ICM shock outside the core. Ten of these galaxies have already been imaged with GALEX, and we are requesting deep observations of these galaxies, in addition to time to image the remaining eight to the same depth.

  12. A new model for gravitational potential perturbations in disks of spiral galaxies. An application to our Galaxy

    NASA Astrophysics Data System (ADS)

    Junqueira, T. C.; Lépine, J. R. D.; Braga, C. A. S.; Barros, D. A.

    2013-02-01

    Aims: We propose a new, more realistic description of the perturbed gravitational potential of spiral galaxies, with spiral arms having Gaussian-shaped groove profiles. The aim is to reach a self-consistent description of the spiral structure, that is, one in which an initial potential perturbation generates, by means of the stellar orbits, spiral arms with a profile similar to that of the imposed perturbation. Self-consistency is a condition for having long-lived structures. Methods: Using the new perturbed potential, we investigate the stable stellar orbits in galactic disks for galaxies with no bar or with only a weak bar. The model is applied to our Galaxy by making use of the axisymmetric component of the potential computed from the Galactic rotation curve, in addition to other input parameters similar to those of our Galaxy. The influence of the bulge mass on the stellar orbits in the inner regions of a disk is also investigated. Results: The new description offers the advantage of easy control of the parameters of the Gaussian profile of its potential. We compute the density contrast between arm and inter-arm regions. We find a range of values for the perturbation amplitude from 400 to 800 km2 s-2 kpc-1, which implies an approximate maximum ratio of the tangential force to the axisymmetric force between 3% and 6%. Good self-consistency of arm shapes is obtained between the Inner Lindblad resonance (ILR) and the 4:1 resonance. Near the 4:1 resonance the response density starts to deviate from the imposed logarithmic spiral form. This creates bifurcations that appear as short arms. Therefore the deviation from a perfect logarithmic spiral in galaxies can be understood as a natural effect of the 4:1 resonance. Beyond the 4:1 resonance we find closed orbits that have similarities with the arms observed in our Galaxy. In regions near the center, elongated stellar orbits appear naturally, in the presence of a massive bulge, without imposing any bar

  13. Axial Ratio of Edge-On Spiral Galaxies as a Test for Bright Radio Halos

    NASA Astrophysics Data System (ADS)

    Singal, J.; Kogut, A.; Jones, E.; Dunlap, H.

    2015-01-01

    We use surface brightness contour maps of nearby edge-on spiral galaxies to determine whether extended bright radio halos are common. In particular, we test a recent model of the spatial structure of the diffuse radio continuum by Subrahmanyan & Cowsik which posits that a substantial fraction of the observed high-latitude surface brightness originates from an extended Galactic halo of uniform emissivity. Measurements of the axial ratio of emission contours within a sample of normal spiral galaxies at 1500 MHz and below show no evidence for such a bright, extended radio halo. Either the Galaxy is atypical compared to nearby quiescent spirals or the bulk of the observed high-latitude emission does not originate from this type of extended halo.

  14. AXIAL RATIO OF EDGE-ON SPIRAL GALAXIES AS A TEST FOR BRIGHT RADIO HALOS

    SciTech Connect

    Singal, J.; Jones, E.; Dunlap, H.; Kogut, A.

    2015-01-20

    We use surface brightness contour maps of nearby edge-on spiral galaxies to determine whether extended bright radio halos are common. In particular, we test a recent model of the spatial structure of the diffuse radio continuum by Subrahmanyan and Cowsik which posits that a substantial fraction of the observed high-latitude surface brightness originates from an extended Galactic halo of uniform emissivity. Measurements of the axial ratio of emission contours within a sample of normal spiral galaxies at 1500 MHz and below show no evidence for such a bright, extended radio halo. Either the Galaxy is atypical compared to nearby quiescent spirals or the bulk of the observed high-latitude emission does not originate from this type of extended halo. (letters)

  15. Does the dwarf galaxy system of the Milky Way originate from Andromeda?

    NASA Astrophysics Data System (ADS)

    Fouquet, Sylvain; Hammer, François; Yang, Yanbin; Puech, Mathieu; Flores, Hector

    2012-12-01

    The Local Group is often seen to be a quiescent environment without significant merger events. However, an ancient major merger may have occurred in the most massive galaxy as suggested by the M31 classical bulge and its halo haunted by numerous stellar streams. Numerical simulations have shown that tidal tails formed during gas-rich major mergers are long-lived and could be responsible for old stellar streams and likely induce the formation of tidal dwarf galaxies (TDGs). Using several hydrodynamical simulations we have investigated the most prominent tidal tail formed during the first passage, which is gas rich and contains old and metal-poor stars. We discovered several striking coincidences after comparing its location and motion to those of the Milky Way (MW) and of the Magellanic Clouds (MCs). First, the tidal tail is sweeping a relatively small volume in which the MW precisely lies. Because the geometry of the merger is somehow fixed by the anisotropic properties of the giant stream (GS), we evaluate the chance of the MW to be at such a rendezvous with this gigantic tidal tail to be 5 per cent. Secondly, the velocity of the tidal tail matches the Large Magellanic Cloud (LMC) proper motion, and reproduces quite well the geometrical and angular momentum properties of the MW dwarfs, that is, the so-called disc of satellites, also known as the vast polar structure (VPOS). Thirdly, the simulation of the tidal tail reveals one of the formed TDGs with the mass and location almost comparable to those of the LMC. Our present modelling is, however, too limited to study the detailed interaction of gas-rich TDGs with the potential of the MW, and a complementary study is required to test whether the dwarf intrinsic properties can be accounted for by our scenario. Nevertheless this study suggests a causal link between an expected event, an ancient, gas-rich major merger at the M31 location, and several enigmas in the Local Group, namely the GS in the M31 outskirts, the

  16. Is the cluster environment quenching the Seyfert activity in elliptical and spiral galaxies?

    NASA Astrophysics Data System (ADS)

    de Souza, R. S.; Dantas, M. L. L.; Krone-Martins, A.; Cameron, E.; Coelho, P.; Hattab, M. W.; de Val-Borro, M.; Hilbe, J. M.; Elliott, J.; Hagen, A.; COIN Collaboration

    2016-09-01

    We developed a hierarchical Bayesian model (HBM) to investigate how the presence of Seyfert activity relates to their environment, herein represented by the galaxy cluster mass, M200, and the normalized cluster centric distance, r/r200. We achieved this by constructing an unbiased sample of galaxies from the Sloan Digital Sky Survey, with morphological classifications provided by the Galaxy Zoo Project. A propensity score matching approach is introduced to control the effects of confounding variables: stellar mass, galaxy colour, and star formation rate. The connection between Seyfert-activity and environmental properties in the de-biased sample is modelled within an HBM framework using the so-called logistic regression technique, suitable for the analysis of binary data (e.g. whether or not a galaxy hosts an AGN). Unlike standard ordinary least square fitting methods, our methodology naturally allows modelling the probability of Seyfert-AGN activity in galaxies on their natural scale, i.e. as a binary variable. Furthermore, we demonstrate how an HBM can incorporate information of each particular galaxy morphological type in an unified framework. In elliptical galaxies our analysis indicates a strong correlation of Seyfert-AGN activity with r/r200, and a weaker correlation with the mass of the host cluster. In spiral galaxies these trends do not appear, suggesting that the link between Seyfert activity and the properties of spiral galaxies are independent of the environment.

  17. A new approach to detailed structural decomposition from the splash and phat surveys: Kicked-up disk stars in the Andromeda galaxy?

    SciTech Connect

    Dorman, Claire E.; Guhathakurta, Puragra; and others

    2013-12-20

    We characterize the bulge, disk, and halo subcomponents in the Andromeda galaxy (M31) over the radial range 4 kpc < R {sub proj} < 225 kpc. The cospatial nature of these subcomponents renders them difficult to disentangle using surface brightness (SB) information alone, especially interior to ∼20 kpc. Our new decomposition technique combines information from the luminosity function (LF) of over 1.5 million bright (20 < m {sub 814W} < 22) stars from the Panchromatic Hubble Andromeda Treasury survey, radial velocities of over 5000 red giant branch stars in the same magnitude range from the Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo survey, and integrated I-band SB profiles from various sources. We use an affine-invariant Markov chain Monte Carlo algorithm to fit an appropriate toy model to these three data sets. The bulge, disk, and halo SB profiles are modeled as a Sérsic, exponential, and cored power law, respectively, and the LFs are modeled as broken power laws. We present probability distributions for each of 32 parameters describing the SB profiles and LFs of the three subcomponents. We find that the number of stars with a disk-like LF is 5.2% ± 2.1% larger than the number with disk-like (dynamically cold) kinematics, suggesting that some stars born in the disk have been dynamically heated to the point that they are kinematically indistinguishable from halo members. This is the first kinematical evidence for a 'kicked-up disk' halo population in M31. The fraction of kicked-up disk stars is consistent with that found in simulations. We also find evidence for a radially varying disk LF, consistent with a negative metallicity gradient in the stellar disk.

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

    NASA Astrophysics Data System (ADS)

    Allaert, Flor

    2015-02-01

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

  19. Origin of cosmic rays. I. Observations of the spiral galaxy NGC 3310

    SciTech Connect

    Duric, N.; Seaquist, E.R.; Crane, P.C.; Davis, L.E.

    1986-05-01

    An observational technique is presented for addressing the problem of the origin of cosmic rays in galaxies by determining and comparing the distributions of cosmic rays, stars, and thermal gas. It is argued that optical continuum, emission line, and radio continuum imaging can be used to determine the distributions of the major stellar populations, the ionized gas, and the cosmic rays in galactic disks. An application of the technique is demonstrated by presenting and discussing observations of the spiral galaxy, NGC 3310. A preliminary analysis points to a possible spiral arm origin but argues against conventional models of cosmic-ray production such as supernova remnants. 38 references.

  20. Low-mass spiral galaxies with little molecular gas and prodigious star formation

    NASA Technical Reports Server (NTRS)

    Kenney, Jeffrey D.; Young, Judith S.

    1988-01-01

    A comparison of CO and H I properties is used here to demonstrate that many CO-poor low-mass Virgo spiral galaxies are rich in atomic gas, which implies that the lack of CO emission from them is due, at least partly, to a lack of molecular gas. Despite the paucity of molecular gas, these H I-rich, CO-poor, low-mass spiral galaxies are undergoing extensive massive star formation. A column density of 10 to the 21st nuclei/sq cm is a necessary but insufficient condition for the creation of an H2-dominated interstellar medium.

  1. A Comparative Study of Knots of Star Formation in Interacting versus Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Smith, Beverly J.; Zaragoza-Cardiel, Javier; Struck, Curtis; Olmsted, Susan; Jones, Keith

    2016-03-01

    Interacting galaxies are known to have higher global rates of star formation on average than normal galaxies, relative to their stellar masses. Using UV and IR photometry combined with new and published Hα images, we have compared the star formation rates (SFRs) of ∼700 star forming complexes in 46 nearby interacting galaxy pairs with those of regions in 39 normal spiral galaxies. The interacting galaxies have proportionally more regions with high SFRs than the spirals. The most extreme regions in the interacting systems lie at the intersections of spiral/tidal structures, where gas is expected to pile up and trigger star formation. Published Hubble Space Telescope images show unusually large and luminous star clusters in the highest luminosity regions. The SFRs of the clumps correlate with measures of the dust attenuation, consistent with the idea that regions with more interstellar gas have more star formation. For the clumps with the highest SFRs, the apparent dust attenuation is consistent with the Calzetti starburst dust attenuation law. This suggests that the high luminosity regions are dominated by a central group of young stars surrounded by a shell of clumpy interstellar gas. In contrast, the lower luminosity clumps are bright in the UV relative to Hα, suggesting either a high differential attenuation between the ionized gas and the stars, or a post-starburst population bright in the UV but faded in Hα. The fraction of the global light of the galaxies in the clumps is higher on average for the interacting galaxies than for the spirals. Thus either star formation in interacting galaxies is “clumpier” on average, or the star forming regions in interacting galaxies are more luminous, dustier, or younger on average.

  2. Ultraviolet photometry from the Orbiting Astronomical Observatory. XL - The energy distributions of spiral and irregular galaxies

    NASA Technical Reports Server (NTRS)

    Code, A. D.; Welch, G. A.

    1982-01-01

    Measurements of the total light of 40 spiral and irregular galaxies are presented. The photometry covers the wavelength range 1550-4250 A and is calibrated on an absolute basis. On the average later-type galaxies are not only bluer at short wavelengths than ellipticals but significantly bluer than visual colors would imply. This reflects a recent history of more vigorous formation of massive stars. The shape of the upper part of the initial mass function apparently varies more among early-type galaxies, producing a wide scatter in their energy distributions. In at least some galaxies interstellar dust appears to have little influence upon the emerging radiation. The local volume luminosity spectrum due to galaxies turns up steeply at short wavelengths, and is shaped largely by contributions from late-type galaxies. The observed ultraviolet background cannot be produced by normal galaxies, although the large corrections implied by theoretical evolutionary models may account for the measurements.

  3. Supernovae and their host galaxies - II. The relative frequencies of supernovae types in spirals

    NASA Astrophysics Data System (ADS)

    Hakobyan, A. A.; Nazaryan, T. A.; Adibekyan, V. Zh.; Petrosian, A. R.; Aramyan, L. S.; Kunth, D.; Mamon, G. A.; de Lapparent, V.; Bertin, E.; Gomes, J. M.; Turatto, M.

    2014-11-01

    We present an analysis of the relative frequencies of different supernova (SN) types in spirals with various morphologies and in barred or unbarred galaxies. We use a well-defined and homogeneous sample of spiral host galaxies of 692 SNe from the Sloan Digital Sky Survey in different stages of galaxy-galaxy interaction and activity classes of nucleus. We propose that the underlying mechanisms shaping the number ratios of SNe types can be interpreted within the framework of interaction-induced star formation, in addition to the known relations between morphologies and stellar populations. We find a strong trend in behaviour of the NIa/NCC ratio depending on host morphology, such that early spirals include more Type Ia SNe. The NIbc/NII ratio is higher in a broad bin of early-type hosts. The NIa/NCC ratio is nearly constant when changing from normal, perturbed to interacting galaxies, then declines in merging galaxies, whereas it jumps to the highest value in post-merging/remnant galaxies. In contrast, the NIbc/NII ratio jumps to the highest value in merging galaxies and slightly declines in post-merging/remnant subsample. The interpretation is that the star formation rates and morphologies of galaxies, which are strongly affected in the final stages of interaction, have an impact on the number ratios of SNe types. The NIa/NCC (NIbc/NII) ratio increases (decreases) from star-forming to active galactic nuclei (AGN) classes of galaxies. These variations are consistent with the scenario of an interaction-triggered starburst evolving into AGN during the later stages of interaction, accompanied with the change of star formation and transformation of the galaxy morphology into an earlier type.

  4. Non-circular motion estimation of the grand-design spiral galaxy NGC 628

    NASA Astrophysics Data System (ADS)

    Colombo, D.

    2013-09-01

    I present a harmonic decomposition analysis of the grand-design spiral galaxy NGC 628 using the H I data from The H I Nearby Galaxy Survey (THINGS), Walter et al., Astron. J. 136, 2563 (2008). The harmonic decomposition analysis allows the estimation of the peculiar motion magnitude of the galaxy not counted in the rotation of the disk. The rotation curve is obtained through a tilted ring analysis and reaches a maximum velocity not higher than 200 km s-1. The residual from the velocity field shows a morphology shift from a m = 1 to a m = 3 feature at R = 120", typical of two spiral arms perturbation of the potential. The non-circular motion have a magnitude of ~10 km s-1, in agreement with previous studies of similar Hubble type galaxies.

  5. Spin Alignments of Spiral Galaxies within the Large-scale Structure from SDSS DR7

    NASA Astrophysics Data System (ADS)

    Zhang, Youcai; Yang, Xiaohu; Wang, Huiyuan; Wang, Lei; Luo, Wentao; Mo, H. J.; van den Bosch, Frank C.

    2015-01-01

    Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 and Galaxy Zoo 2, we investigate the alignment of spin axes of spiral galaxies with their surrounding large-scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certain mass threshold. We find that the spin axes only have weak tendencies to be aligned with (or perpendicular to) the intermediate (or minor) axis of the local tidal tensor. The signal is the strongest in a cluster environment where all three eigenvalues of the local tidal tensor are positive. Compared to the alignments between halo spins and the local tidal field obtained in N-body simulations, the above observational results are in best agreement with those for the spins of inner regions of halos, suggesting that the disk material traces the angular momentum of dark matter halos in the inner regions.

  6. SPIN ALIGNMENTS OF SPIRAL GALAXIES WITHIN THE LARGE-SCALE STRUCTURE FROM SDSS DR7

    SciTech Connect

    Zhang, Youcai; Yang, Xiaohu; Luo, Wentao; Wang, Huiyuan; Wang, Lei; Mo, H. J.; Van den Bosch, Frank C. E-mail: xyang@sjtu.edu.cn

    2015-01-01

    Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 and Galaxy Zoo 2, we investigate the alignment of spin axes of spiral galaxies with their surrounding large-scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certain mass threshold. We find that the spin axes only have weak tendencies to be aligned with (or perpendicular to) the intermediate (or minor) axis of the local tidal tensor. The signal is the strongest in a cluster environment where all three eigenvalues of the local tidal tensor are positive. Compared to the alignments between halo spins and the local tidal field obtained in N-body simulations, the above observational results are in best agreement with those for the spins of inner regions of halos, suggesting that the disk material traces the angular momentum of dark matter halos in the inner regions.

  7. The role of interactions in triggering bars, spiral arms and AGN in disk galaxies

    NASA Astrophysics Data System (ADS)

    Nair, Preethi; Ellison, Sara L.; Patton, David R.

    2016-01-01

    The role of secular structures like bars, rings and spiral arms in triggering star formation and AGN activity in disk galaxies are not well understood. In addition, the mechanisms which create and destroy these structures are not well characterized. Mergers are considered to be one of the main mechanisms which can trigger bars in massive disk galaxies. Using a sample of ~8000 close pair galaxies at 0.02 < z < 0.06 from the Sloan Digital Sky Survey, I will present results illustrating the role of mergers in triggering bars, rings, spiral arms and AGN as a function of close pair separation and merger ratios as well as their dependence on morphology and other physical properties of the galaxies. Time permitting, I will show how resolved IFU observations from SDSS MaNGA will help to place stronger constraints on the role of these structures in triggering star formation and AGN.

  8. 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.

  9. HERSCHEL EXPLOITATION OF LOCAL GALAXY ANDROMEDA (HELGA). III. THE STAR FORMATION LAW IN M31

    SciTech Connect

    Ford, George P.; Gear, Walter K.; Smith, Matthew W. L.; Eales, Steve A.; Gomez, Haley L.; Kirk, Jason; Baes, Maarten; De Looze, Ilse; Fritz, Jacopo; Gentile, Gianfranco; Gordon, Karl D.; Verstappen, Joris; Bendo, George J.; Boquien, Mederic; Boselli, Alessandro; Cooray, Asantha R.; Lebouteiller, Vianney; O'Halloran, Brian; Spinoglio, Luigi; Wilson, Christine D.

    2013-05-20

    We present a detailed study of how the star formation rate (SFR) relates to the interstellar medium (ISM) of M31 at {approx}140 pc scales. The SFR is calculated using the far-ultraviolet and 24 {mu}m emission, corrected for the old stellar population in M31. We find a global value for the SFR of 0.25{sup +0.06}{sub -0.04} M{sub sun} yr{sup -1} and compare this with the SFR found using the total far-infrared luminosity. There is general agreement in regions where young stars dominate the dust heating. Atomic hydrogen (H I) and molecular gas (traced by carbon monoxide, CO) or the dust mass is used to trace the total gas in the ISM. We show that the global surface densities of SFR and gas mass place M31 among a set of low-SFR galaxies in the plot of Kennicutt. The relationship between SFR and gas surface density is tested in six radial annuli across M31, assuming a power law relationship with index, N. The star formation (SF) law using total gas traced by H I and CO gives a global index of N = 2.03 {+-} 0.04, with a significant variation with radius; the highest values are observed in the 10 kpc ring. We suggest that this slope is due to H I turning molecular at {Sigma}{sub Gas} {approx} 10 M{sub Sun} pc{sup -2}. When looking at H{sub 2} regions, we measure a higher mean SFR suggesting a better spatial correlation between H{sub 2} and SF. We find N {approx} 0.6 with consistent results throughout the disk-this is at the low end of values found in previous work and argues against a superlinear SF law on small scales.

  10. XMM-NEWTON DETECTS A HOT GASEOUS HALO IN THE FASTEST ROTATING SPIRAL GALAXY UGC 12591

    SciTech Connect

    Dai Xinyu; Anderson, Michael E.; Bregman, Joel N.; Miller, Jon M.

    2012-08-20

    We present our XMM-Newton observation of the fastest rotating spiral galaxy UGC 12591. We detect hot gas halo emission out to 80 kpc from the galaxy center, and constrain the halo gas mass to be smaller than 4.5 Multiplication-Sign 10{sup 11} M{sub Sun }. We also measure the temperature of the hot gas as T = 0.64 {+-} 0.03 keV. Combining our x-ray constraints and the near-infrared and radio measurements in the literature, we find a baryon mass fraction of 0.03-0.05 in UGC 12591, suggesting a missing baryon mass of 70% compared with the cosmological mean value. Combined with another recent measurement in NGC 1961, the result strongly argues that the majority of missing baryons in spiral galaxies do not reside in their hot halos. We also find that UGC 12591 lies significantly below the baryonic Tully-Fisher relationship. Finally, we find that the baryon fractions of massive spiral galaxies are similar to those of galaxy groups with similar masses, indicating that the baryon loss is ultimately controlled by the gravitational potential well. The cooling radius of this gas halo is small, similar to NGC 1961, which argues that the majority of the stellar mass of this galaxy is not assembled as a result of cooling of this gas halo.

  11. Circumnuclear Regions In Barred Spiral Galaxies. 1; Near-Infrared Imaging

    NASA Technical Reports Server (NTRS)

    Perez-Ramirez, D.; Knapen, J. H.; Peletier, R. F.; Laine, S.; Doyon, R.; Nadeau, D.

    2000-01-01

    We present sub-arcsecond resolution ground-based near-infrared images of the central regions of a sample of twelve barred galaxies with circumnuclear star formation activity, which is organized in ring-like regions typically one kiloparsec in diameter. We also present Hubble Space Telescope near-infrared images of ten of our sample galaxies, and compare them with our ground-based data. Although our sample galaxies were selected for the presence of circumnuclear star formation activity, our broad-band near-infrared images are heterogeneous, showing a substantial amount of small-scale structure in some galaxies, and practically none in others. We argue that, where it exists, this structure is caused by young stars, which also cause the characteristic bumps or changes in slope in the radial profiles of ellipticity, major axis position angle, surface brightness and colour at the radius of the circumnuclear ring in most of our sample galaxies. In 7 out of 10 HST images, star formation in the nuclear ring is clearly visible as a large number of small emitting regions, organised into spiral arm fragments, which are accompanied by dust lanes. NIR colour index maps show much more clearly the location of dust lanes and, in certain cases, regions of star formation than single broad-band images. Circumnuclear spiral structure thus outlined appears to be common in barred spiral galaxies with circumnuclear star formation.

  12. Evidence for a Massive, Extended Circumgalactic Medium Around the Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Lehner, Nicolas; Howk, J. Christopher; Wakker, Bart P.

    2015-05-01

    We demonstrate the presence of an extended and massive circumgalactic medium (CGM) around Messier 31 using archival HST Cosmic Origins Spectrograph ultraviolet spectroscopy of 18 QSOs projected within two virial radii of M31 ({{R}vir}=300 kpc). We detect absorption from Si iii at -300≲ {{v}LSR}≲ -150 km s-1 toward all three sightlines at R≲ 0.2{{R}vir}, 3 of 4 sightlines at 0.8≲ R/{{R}vir}≲ 1.1, and possibly 1 of 11 at 1.1\\lt R/{{R}vir}≲ 1.8. We present several arguments that the gas at these velocities observed in these directions originates from the M31 CGM rather than the Local Group or Milky Way CGM or Magellanic Stream. We show that the dwarf galaxies located in the CGM of M31 have very similar velocities over similar projected distances from M31. We find a non-trivial relationship only at these velocities between the column densities (N) of all the ions and R, whereby N decreases with increasing R. At R\\lt 0.8{{R}vir}, the covering fraction is close to unity for Si iii and C iv ({{f}c}˜ 60%-97% at the 90% confidence level), but drops to {{f}c}≲ 10%-20% at R≳ {{R}vir}. We show that the M31 CGM gas is bound, multiphase, predominantly ionized, and is more highly ionized gas at larger R. We estimate using Si ii, Si iii, and Si iv, a CGM metal mass of ≳ 2× {{10}6} M⊙ and gas mass of ≳ 3× {{10}9}({{Z}⊙ }/Z) M⊙ within 0.2{{R}vir}, and possibly a factor of ˜10 larger within {{R}vir}, implying substantial metal and gas masses in the CGM of M31. 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 No. NAS5-26555.

  13. The LAMOST Survey of Globular Clusters in the Andromeda and Triangulum Galaxies

    NASA Astrophysics Data System (ADS)

    Chen, Bingqiu; Liu, Xiaowei

    2015-08-01

    of cluster-bearing satellite galaxies, similar as in the MW. Chemical abundances as well as the ages are also presented and discussed for the M31 GCs observed by LAMOST.

  14. ARM AND INTERARM STAR FORMATION IN SPIRAL GALAXIES

    SciTech Connect

    Foyle, K.; Rix, H.-W.; Walter, F.; Leroy, A. K.

    2010-12-10

    We investigate the relationship between spiral arms and star formation in the grand-design spirals NGC 5194 and NGC 628 and in the flocculent spiral NGC 6946. Filtered maps of near-IR (3.6 {mu}m) emission allow us to identify 'arm regions' that should correspond to regions of stellar mass density enhancements. The two grand-design spirals show a clear two-armed structure, while NGC 6946 is more complex. We examine these arm and interarm regions, looking at maps that trace recent star formation-far-ultraviolet (GALEX NGS) and 24 {mu}m emission (Spitzer SINGS)-and cold gas-CO (HERACLES) and H I (THINGS). We find the star formation tracers and CO more concentrated in the spiral arms than the stellar 3.6 {mu}m flux. If we define the spiral arms as the 25% highest pixels in the filtered 3.6 {mu}m images, we find that the majority (60%) of star formation tracers occur in the interarm regions; this result persists qualitatively even when considering the potential impact of finite data resolution and diffuse interarm 24 {mu}m emission. Even with a generous definition of the arms (45% highest pixels), interarm regions still contribute at least 30% to the integrated star formation rate (SFR) tracers. We look for evidence that spiral arms trigger star or cloud formation using the ratios of SFR (traced by a combination of FUV and 24 {mu}m emission) to H{sub 2} (traced by CO) and H{sub 2} to H I. Any enhancement of SFR/M(H{sub 2}) in the arm region is very small (less than 10%) and the grand-design spirals show no enhancement compared to the flocculent target. Arm regions do show a weak enhancement in H{sub 2}/H I compared to the interarm regions, but at a fixed gas surface density there is little clear enhancement in the H{sub 2}/H I ratio in the arm regions. Thus, it seems that spiral arms may only act to concentrate the gas to higher densities in the arms.

  15. The impact of dark matter cusps and cores on the satellite galaxy population around spiral galaxies

    NASA Astrophysics Data System (ADS)

    Peñarrubia, Jorge; Benson, Andrew J.; Walker, Matthew G.; Gilmore, Gerard; McConnachie, Alan W.; Mayer, Lucio

    2010-08-01

    We use N-body simulations to study the effects that a divergent (i.e. `cuspy') dark matter profile introduces on the tidal evolution of dwarf spheroidal galaxies (dSphs). Our models assume cosmologically motivated initial conditions where dSphs are dark-matter-dominated systems on eccentric orbits about a host galaxy composed of a dark halo and a baryonic disc. We find that the resilience of dSphs to tidal stripping is extremely sensitive to the cuspiness of the inner halo profile; whereas dwarfs with a cored profile can be easily destroyed by the disc component, those with cusps always retain a bound remnant, even after losing more than 99.99 per cent of the original mass. For a given halo profile, the evolution of the structural parameters as driven by tides is controlled solely by the total amount of mass lost. This information is used to construct a semi-analytic code that follows the tidal evolution of individual satellites as they fall into a more massive host, which allows us to simulate the hierarchical build-up of spiral galaxies assuming different halo profiles and disc masses. We find that tidal encounters with discs tend to decrease the average mass of satellite galaxies at all galactocentric radii. Of all satellites, those accreted before re-ionization (z >~ 6), which may be singled out by anomalous metallicity patterns, provide the strongest constraints on the inner profile of dark haloes. These galaxies move on orbits that penetrate the disc repeatedly and survive to the present day only if haloes have an inner density cusp. We show that the size-mass relationship established from Milky Way (MW) dwarfs strongly supports the presence of cusps in the majority of these systems, as cored models systematically underestimate the masses of the known ultra-faint dSphs. Our models also indicate that a massive M31 disc may explain why many of its dSphs with suitable kinematic data fall below the size-mass relationship derived from MW dSphs. We also examine

  16. Magnetic Fields in Barred Spiral Galaxies: NGC 2442 & NGC 7552

    NASA Astrophysics Data System (ADS)

    Ehle, M.; Harnett, J. I.; Beck, R.; Haynes, R. F.; Gray, A.

    2002-12-01

    We report on the total and polarised radio continuum emission of the southern barred galaxies NGC 2442 and NGC 7552 observed with the ATCA at λ6 cm (cf. Harnett et al. 2002). These galaxies form part of a sample of 20 barred galaxies mapped at several wavelengths with the ATCA and VLA (Beck et al. 2002) to study the role of magnetic fields in the bar with respect to the gas flow and star formation.

  17. Hα kinematics of S4G spiral galaxies - II. Data description and non-circular motions

    NASA Astrophysics Data System (ADS)

    Erroz-Ferrer, Santiago; Knapen, Johan H.; Leaman, Ryan; Cisternas, Mauricio; Font, Joan; Beckman, John E.; Sheth, Kartik; Muñoz-Mateos, Juan Carlos; Díaz-García, Simón; Bosma, Albert; Athanassoula, E.; Elmegreen, Bruce G.; Ho, Luis C.; Kim, Taehyun; Laurikainen, Eija; Martinez-Valpuesta, Inma; Meidt, Sharon E.; Salo, Heikki

    2015-07-01

    We present a kinematical study of 29 spiral galaxies included in the Spitzer Survey of Stellar Structure in Galaxies, using Hα Fabry-Perot (FP) data obtained with the Galaxy Hα Fabry-Perot System instrument at the William Herschel Telescope in La Palma, complemented with images in the R band and in Hα. The primary goal is to study the evolution and properties of the main structural components of galaxies through the kinematical analysis of the FP data, complemented with studies of morphology, star formation and mass distribution. In this paper we describe how the FP data have been obtained, processed and analysed. We present the resulting moment maps, rotation curves, velocity model maps and residual maps. Images are available in FITS format through the NASA/IPAC Extragalactic Database and the Centre de Données Stellaires. With these data products we study the non-circular motions, in particular those found along the bars and spiral arms. The data indicate that the amplitude of the non-circular motions created by the bar does not correlate with the bar strength indicators. The amplitude of those non-circular motions in the spiral arms does not correlate with either arm class or star formation rate along the spiral arms. This implies that the presence and the magnitude of the streaming motions in the arms is a local phenomenon.

  18. What is the number of spiral galaxies in compact groups

    NASA Technical Reports Server (NTRS)

    Tikhonov, N. A.

    1990-01-01

    The distribution of morphological types of galaxies in compact groups is studied on plates from the 6 m telescope. In compact groups there are 57 percent galaxies of late morphological types (S + Irr), 23 percent lenticulars (SO) and 20 percent elliptical galaxies. The morphological content of compact groups is very nearly the same as in loose groups. There is no dependence of galaxy morphology on density in all compact groups (and possibly in loose groups). Genuine compact groups form only 60 percent of Hickson's list.

  19. Long-lived Spiral Structure for Galaxies with Intermediate-size Bulges

    NASA Astrophysics Data System (ADS)

    Saha, Kanak; Elmegreen, Bruce

    2016-08-01

    Spiral structure in disk galaxies is modeled with nine collisionless N-body simulations including live disks, halos, and bulges with a range of masses. Two of these simulations make long-lasting and strong two-arm spiral wave modes that last for ∼5 Gyr with constant pattern speed. These two had a light stellar disk and the largest values of the Toomre Q parameter in the inner region at the time the spirals formed, suggesting the presence of a Q-barrier to wave propagation resulting from the bulge. The relative bulge mass in these cases is about 10%. Models with weak two-arm spirals had pattern speeds that followed the radial dependence of the Inner Lindblad Resonance.

  20. Long-lived Spiral Structure for Galaxies with Intermediate-size Bulges

    NASA Astrophysics Data System (ADS)

    Saha, Kanak; Elmegreen, Bruce

    2016-08-01

    Spiral structure in disk galaxies is modeled with nine collisionless N-body simulations including live disks, halos, and bulges with a range of masses. Two of these simulations make long-lasting and strong two-arm spiral wave modes that last for ˜5 Gyr with constant pattern speed. These two had a light stellar disk and the largest values of the Toomre Q parameter in the inner region at the time the spirals formed, suggesting the presence of a Q-barrier to wave propagation resulting from the bulge. The relative bulge mass in these cases is about 10%. Models with weak two-arm spirals had pattern speeds that followed the radial dependence of the Inner Lindblad Resonance.

  1. A close nuclear black-hole pair in the spiral galaxy NGC 3393.

    PubMed

    Fabbiano, G; Wang, Junfeng; Elvis, M; Risaliti, G

    2011-09-22

    The current picture of galaxy evolution advocates co-evolution of galaxies and their nuclear massive black holes, through accretion and galactic merging. Pairs of quasars, each with a massive black hole at the centre of its galaxy, have separations of 6,000 to 300,000 light years (refs 2 and 3; 1 parsec = 3.26 light years) and exemplify the first stages of this gravitational interaction. The final stages of the black-hole merging process, through binary black holes and final collapse into a single black hole with gravitational wave emission, are consistent with the sub-light-year separation inferred from the optical spectra and light-variability of two such quasars. The double active nuclei of a few nearby galaxies with disrupted morphology and intense star formation (such as NGC 6240 with a separation of about 2,600 light years and Mrk 463 with a separation of about 13,000 light years between the nuclei) demonstrate the importance of major mergers of equal-mass spiral galaxies in this evolution; such mergers lead to an elliptical galaxy, as in the case of the double-radio-nucleus elliptical galaxy 0402+379 (with a separation of about 24 light years between the nuclei). Minor mergers of a spiral galaxy with a smaller companion should be a more common occurrence, evolving into spiral galaxies with active massive black-hole pairs, but have hitherto not been seen. Here we report the presence of two active massive black holes, separated by about 490 light years, in the Seyfert galaxy NGC 3393 (50 Mpc, about 160 million light years). The regular spiral morphology and predominantly old circum-nuclear stellar population of this galaxy, and the closeness of the black holes embedded in the bulge, provide a hitherto missing observational point to the study of galaxy/black hole evolution. Comparison of our observations with current theoretical models of mergers suggests that they are the result of minor merger evolution. PMID:21881560

  2. New Portraits of Spiral Galaxies NGC 613, NGC 1792 and NGC 3627

    NASA Astrophysics Data System (ADS)

    2003-12-01

    Not so long ago, the real nature of the "spiral nebulae", spiral-shaped objects observed in the sky through telescopes, was still unknown. This long-standing issue was finally settled in 1924 when the famous American astronomer Edwin Hubble provided conclusive evidence that they are located outside our own galaxy and are in fact "island universes" of their own. Nowadays, we know that the Milky Way is just one of billions of galaxies in the Universe. They come in vastly different shapes - spiral, elliptical, irregular - and many of them are simply beautiful, especially the spiral ones. Astronomers Mark Neeser from the Universitäts-Sternwarte München (Germany) and Peter Barthel from the Kapteyn Institute in Groningen (The Netherlands) were clearly not insensitive to this when they obtained images of three beautiful spiral galaxies with ESO's Very Large Telescope (VLT). They did this in twilight during the early morning when they had to stop their normal observing programme, searching for very distant and faint quasars. The resulting colour images ( ESO PR Photos 33a-c/03 ) were produced by combining several CCD images in three different wavebands from the FORS multi-mode instruments. The three galaxies are known as NGC 613, NGC 1792 and NGC 3627 . They are characterized by strong far-infrared, as well as radio emission, indicative of substantial ongoing star-formation activity. Indeed, these images all display prominent dust as well as features related to young stars, clear signs of intensive star-formation. NGC 613 ESO PR Photo 33a/03 ESO PR Photo 33a/03 [Preview - JPEG: 470 x 400 pix - 25k] [Normal - JPEG: 939 x 800 pix - 416k] [Full Res - JPEG: 2702 x 2301 pix - 3.4M] PR Photo 33a/03 of the barred spiral galaxy NGC 613 was obtained with the FORS1 and FORS2 multi-mode instruments (at VLT MELIPAL and YEPUN, respectively) on December 16-18, 2001. It is a composite of three exposures in different wavebands, cf. the technical note below. The full-resolution version

  3. Gravitationally induced spurs in spiral galaxies - An example in M31

    NASA Technical Reports Server (NTRS)

    Byrd, G. G.

    1983-01-01

    Radio and optical morphological data are consistent with a gravitational mechanism for the anomalous structure between the S4 and SS arms of M31, with the large complex of H I and H II in and around NGC 206 being implicated in the creation of the anomalous spur. Computer models of the gravitational effects of the spur show that its gravitational induction explains the observed velocity distortions. It is speculated that spurs in more distant galaxies, for which high resolution data as complete as that presented are not yet available, are also gravitational. This implicitly applies not only to spurs in galaxies with well defined spiral structure, but also for galaxies with more chaotic spiral arm patterns.

  4. The Near-Infrared Ca II Triplet-σ Relation for Bulges of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Falcón-Barroso, Jesús; Peletier, Reynier F.; Vazdekis, Alexandre; Balcells, Marc

    2003-05-01

    We present measurements of the near-infrared Ca II triplet (CaT, CaT*), Paschen (PaT), and magnesium (Mg I) indices for a well-studied sample of 19 bulges of early to intermediate spiral galaxies. We find that both the CaT* and CaT indices decrease with central velocity dispersion σ with small scatter. This dependence is similar to that recently found by Cenarro for elliptical galaxies, implying a uniform CaT*-σ relation that applies to galaxies from ellipticals to intermediate-type spirals. The decrease of CaT and CaT* with σ contrasts with the well-known increase of another α-element index, Mg2, with σ. We discuss the role of Ca underabundance ([Ca/Fe]<0) and initial mass function variations in the onset of the observed relations.

  5. Megamaser Disks Reveal a Broad Distribution of Black Hole Mass in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Greene, J. E.; Seth, A.; Kim, M.; Läsker, R.; Goulding, A.; Gao, F.; Braatz, J. A.; Henkel, C.; Condon, J.; Lo, K. Y.; Zhao, W.

    2016-08-01

    We use new precision measurements of black hole (BH) masses from water megamaser disks to investigate scaling relations between macroscopic galaxy properties and supermassive BH mass. The megamaser-derived BH masses span 106–108 {M}ȯ , while all the galaxy properties that we examine (including total stellar mass, central mass density, and central velocity dispersion) lie within a narrower range. Thus, no galaxy property correlates tightly with {M}{BH} in ∼L* spiral galaxies as traced by megamaser disks. Of them all, stellar velocity dispersion provides the tightest relation, but at fixed {σ }* the mean megamaser {M}{BH} are offset by ‑0.6 ± 0.1 dex relative to early-type galaxies. Spiral galaxies with non-maser dynamical BH masses do not appear to show this offset. At low mass, we do not yet know the full distribution of BH mass at fixed galaxy property; the non-maser dynamical measurements may miss the low-mass end of the BH distribution due to an inability to resolve their spheres of influence and/or megamasers may preferentially occur in lower-mass BHs.

  6. The Discovery of Seven Extremely Low Surface Brightness Galaxies in the Field of the Nearby Spiral Galaxy M101

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    Dwarf satellite galaxies are a key probe of dark matter and of galaxy formation on small scales and of the dark matter halo masses of their central galaxies. They have very low surface brightness, which makes it difficult to identify and study them outside of the Local Group. We used a low surface brightness-optimized telescope, the Dragonfly Telephoto Array, to search for dwarf galaxies in the field of the massive spiral galaxy M101. We identify seven large, low surface brightness objects in this field, with effective radii of 10-30 arcseconds and central surface brightnesses of μ g ~ 25.5-27.5 mag arcsec-2. Given their large apparent sizes and low surface brightnesses, these objects would likely be missed by standard galaxy searches in deep fields. Assuming the galaxies are dwarf satellites of M101, their absolute magnitudes are in the range -11.6 <~ MV <~ -9.3 and their effective radii are 350 pc-1.3 kpc. Their radial surface brightness profiles are well fit by Sersic profiles with a very low Sersic index (n ~ 0.3-0.7). The properties of the sample are similar to those of well-studied dwarf galaxies in the Local Group, such as Sextans I and Phoenix. Distance measurements are required to determine whether these galaxies are in fact associated with M101 or are in its foreground or background.

  7. THE DISCOVERY OF SEVEN EXTREMELY LOW SURFACE BRIGHTNESS GALAXIES IN THE FIELD OF THE NEARBY SPIRAL GALAXY M101

    SciTech Connect

    Merritt, Allison; Van Dokkum, Pieter; Abraham, Roberto

    2014-06-01

    Dwarf satellite galaxies are a key probe of dark matter and of galaxy formation on small scales and of the dark matter halo masses of their central galaxies. They have very low surface brightness, which makes it difficult to identify and study them outside of the Local Group. We used a low surface brightness-optimized telescope, the Dragonfly Telephoto Array, to search for dwarf galaxies in the field of the massive spiral galaxy M101. We identify seven large, low surface brightness objects in this field, with effective radii of 10-30 arcseconds and central surface brightnesses of μ {sub g} ∼ 25.5-27.5 mag arcsec{sup –2}. Given their large apparent sizes and low surface brightnesses, these objects would likely be missed by standard galaxy searches in deep fields. Assuming the galaxies are dwarf satellites of M101, their absolute magnitudes are in the range –11.6 ≲ M{sub V} ≲ –9.3 and their effective radii are 350 pc-1.3 kpc. Their radial surface brightness profiles are well fit by Sersic profiles with a very low Sersic index (n ∼ 0.3-0.7). The properties of the sample are similar to those of well-studied dwarf galaxies in the Local Group, such as Sextans I and Phoenix. Distance measurements are required to determine whether these galaxies are in fact associated with M101 or are in its foreground or background.

  8. LIFTING THE VEIL OF DUST TO REVEAL THE SECRETS OF SPIRAL GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have combined information from the NASA Hubble Space Telescope's visible- and infrared-light cameras to show the hearts of four spiral galaxies peppered with ancient populations of stars. The top row of pictures, taken by a ground-based telescope, represents complete views of each galaxy. The blue boxes outline the regions observed by the Hubble telescope. The bottom row represents composite pictures from Hubble's visible- and infrared-light cameras, the Wide Field and Planetary Camera 2 (WFPC2) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). Astronomers combined views from both cameras to obtain the true ages of the stars surrounding each galaxy's bulge. The Hubble telescope's sharper resolution allows astronomers to study the intricate structure of a galaxy's core. The galaxies are ordered by the size of their bulges. NGC 5838, an 'S0' galaxy, is dominated by a large bulge and has no visible spiral arms; NGC 7537, an 'Sbc' galaxy, has a small bulge and loosely wound spiral arms. Astronomers think that the structure of NGC 7537 is very similar to our Milky Way. The galaxy images are composites made from WFPC2 images taken with blue (4445 Angstroms) and red (8269 Angstroms) filters, and NICMOS images taken in the infrared (16,000 Angstroms). They were taken in June, July, and August of 1997. Credits for the ground-based images: Allan Sandage (The Observatories of the Carnegie Institution of Washington) and John Bedke (Computer Sciences Corporation and the Space Telescope Science Institute) Credits for WFPC2 and NICMOS composites: NASA, ESA, and Reynier Peletier (University of Nottingham, United Kingdom)

  9. AN H{alpha} NUCLEAR SPIRAL STRUCTURE IN THE E0 ACTIVE GALAXY Arp 102B

    SciTech Connect

    Fathi, Kambiz; Axon, David J.; Kharb, Preeti; Robinson, Andrew; Storchi-Bergmann, Thaisa; Marconi, Alessandro; Maciejewski, Witold; Capetti, Alessandro E-mail: djasps@rit.edu E-mail: pxksps@cis.rit.edu E-mail: marconi@arcetri.astro.it E-mail: capetti@to.astro.it

    2011-08-01

    We report the discovery of a two-armed mini-spiral structure within the inner kiloparsec of the E0 LINER/Seyfert 1 galaxy Arp 102B. The arms are observed in H{alpha} emission and located east and west of the nucleus, extending up to {approx}1 kpc from it. We use narrow-band imaging from the Hubble Space Telescope Advanced Camera for Surveys, in combination with archival Very Large Array radio images at 3.6 and 6 cm to investigate the origin of the nuclear spiral. From the H{alpha} luminosity of the spiral, we obtain an ionized gas mass of the order of 10{sup 6} solar masses. One possibility is that the nuclear spiral represents a gas inflow triggered by a recent accretion event which has replenished the accretion disk, giving rise to the double-peaked emission-line profiles characteristic of Arp 102B. However, the radio images show a one-sided curved jet which correlates with the eastern spiral arm observed in the H{alpha} image. A published milliarcsecond radio image also shows a one-sided structure at position angle {approx}40{sup 0}, approximately aligned with the inner part of the eastern spiral arm. The absence of a radio counterpart to the western spiral arm is tentatively interpreted as indicating that the jet is relativistic, with an estimated speed of 0.45c. Estimates of the jet kinetic energy and the ionizing luminosity of the active nucleus indicate that both are capable of ionizing the gas along the spiral arms. We conclude that, although the gas in the nuclear region may have originated in an accretion event, the mini spiral is most likely the result of a jet-cloud interaction rather than an inflowing stream.

  10. The Soft X-Ray Emission Component of Spiral Galaxies

    NASA Technical Reports Server (NTRS)

    Fabbiano, Giuseppina

    1998-01-01

    Work included the analysis of the HRJ observations of the Sombrero galaxy (Fabbiano and Juda) published in Ap.J. This paper discussed the discovery of a point-like x-ray source at the nucleus of the galaxy, which is suspected to host a massive black hole. More work was done on the analysis of the Observation of M94 in support of an AXAF proposal. We have also analyzed the M81 data by adding to our observation the entire set of the archival ROSAT data. We plan to write up the results for publication. Both galaxies have nuclei optically similar to that of the Sombrero galaxy. The nucleus of M81 is a known x-ray source. The M94 data has revealed a point-like nuclear source superposed on more diffuse emission.

  11. Spiral eigenmodes triggered by grooves in the phase space of disc galaxies

    NASA Astrophysics Data System (ADS)

    De Rijcke, S.; Voulis, I.

    2016-02-01

    We use linear perturbation theory to investigate how a groove in the phase space of a disc galaxy changes the stellar disc's stability properties. Such a groove is a narrow trough around a fixed angular momentum from which most stars have been removed, rendering part of the disc unresponsive to spiral waves. We find that a groove can dramatically alter a disc's eigenmode spectrum by giving rise to a set of vigorously growing eigenmodes. These eigenmodes are particular to the grooved disc and are absent from the original ungrooved disc's mode spectrum. We discuss the properties and possible origin of the different families of new modes. By the very nature of our technique, we prove that a narrow phase-space groove can be a source of rapidly growing spiral patterns that are true eigenmodes of the grooved disc and that no non-linear processes need to be invoked to explain their presence in N-body simulations of disc galaxies. Our results lend support to the idea that spiral structure can be a recurrent phenomenon, in which one generation of spiral modes alters a disc galaxy's phase space in such a way that a following generation of modes is destabilized.

  12. Gas Clouds in Whirlpool Galaxy Yield Important Clues Supporting Theory on Spiral Arms

    NASA Astrophysics Data System (ADS)

    2004-06-01

    Astronomers studying gas clouds in the famous Whirlpool Galaxy have found important clues supporting a theory that seeks to explain how the spectacular spiral arms of galaxies can persist for billions of years. The astronomers applied techniques used to study similar gas clouds in our own Milky Way to those in the spiral arms of a neighbor galaxy for the first time, and their results bolster a theory first proposed in 1964. M51 The spiral galaxy M51: Left, as seen with the Hubble Space Telescope; Right, radio image showing location of Carbon Monoxide gas. CREDIT: STScI, OVRO, IRAM (Click on image for larger version) Image Files Optical and Radio (CO) Views (above image) HST Optical Image with CO Contours Overlaid Radio/Optical Composite Image of M51 VLA/Effelsberg Radio Image of M51, With Panel Showing Magnetic Field Lines The Whirlpool Galaxy, about 31 million light-years distant, is a beautiful spiral in the constellation Canes Venatici. Also known as M51, it is seen nearly face-on from Earth and is familiar to amateur astronomers and has been featured in countless posters, books and magazine articles. "This galaxy made a great target for our study of spiral arms and how star formation works along them," said Eva Schinnerer, of the National Radio Astronomy Observatory in Socorro, NM. "It was ideal for us because it's one of the closest face-on spirals in the sky," she added. Schinnerer worked with Axel Weiss of the Institute for Millimeter Radio Astronomy (IRAM) in Spain, Susanne Aalto of the Onsala Space Observatory in Sweden, and Nick Scoville of Caltech. The astronomers presented their findings to the American Astronomical Society's meeting in Denver, Colorado. The scientists analyzed radio emission from Carbon Monoxide (CO) molecules in giant gas clouds along M51's spiral arms. Using telescopes at Caltech's Owens Valley Radio Observatory and the 30-meter radio telescope of IRAM, they were able to determine the temperatures and amounts of turbulence within the

  13. 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.

  14. The relationship between the carbon monoxide intensity and the radio continuum emission in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Adler, David S.; Lo, K. Y.; Allen, Ronald J.

    1991-01-01

    The relationship between the velocity-integrated CO emission and the nonthermal radio continuum brightness in the disks of normal spiral galaxies is examined on a variety of length scales. On a global scale, the total CO intensity correlates strongly with the total radio continuum flux density for a sample of 31 galaxies. On scales of about 2 kpc or more in the disk of individual galaxies, it is found that the ratio I(CO)/T(20) remains fairly constant over the entire disk as well as from galaxy to galaxy. For the eight spirals in the sample, the disk-averaged values of I(CO)/T(20) range from 0.6-2.4, with the average over all eight galaxies being 1.3 +/- 0.6. It is concluded that what these various length scales actually trace are differences in the primary heating mechanism of the gas in the beam. The observed relationship between CO and nonthermal radio continuum emission can be explained by assuming that molecular gas in galactic disks is heated primarily by cosmic rays. The observed relationship is used to show that the brightness of synchrotron emission is proportional to n(cr) exp 0.4 - 0.9 in galactic disks.

  15. Galaxy Zoo: the dependence of the star formation-stellar mass relation on spiral disc morphology

    NASA Astrophysics Data System (ADS)

    Willett, Kyle W.; Schawinski, Kevin; Simmons, Brooke D.; Masters, Karen L.; Skibba, Ramin A.; Kaviraj, Sugata; Melvin, Thomas; Wong, O. Ivy; Nichol, Robert C.; Cheung, Edmond; Lintott, Chris J.; Fortson, Lucy

    2015-05-01

    We measure the stellar mass-star formation rate (SFR) relation in star-forming disc galaxies at z ≤ 0.085, using Galaxy Zoo morphologies to examine different populations of spirals as classified by their kiloparsec-scale structure. We examine the number of spiral arms, their relative pitch angle, and the presence of a galactic bar in the disc, and show that both the slope and dispersion of the M⋆-SFR relation is constant when varying all the above parameters. We also show that mergers (both major and minor), which represent the strongest conditions for increases in star formation at a constant mass, only boost the SFR above the main relation by ˜0.3 dex; this is significantly smaller than the increase seen in merging systems at z > 1. Of the galaxies lying significantly above the M⋆-SFR relation in the local Universe, more than 50 per cent are mergers. We interpret this as evidence that the spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms or are completely overwhelmed by the combination of outflows and feedback. The arrangement of the star formation can be changed, but the system as a whole regulates itself even in the presence of strong dynamical forcing.

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

    SciTech Connect

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

    2013-03-20

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

  17. 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.

  18. Reconstructing magnetic fields of spiral galaxies from radiopolarimetric observations

    NASA Astrophysics Data System (ADS)

    Shneider, C.

    2015-12-01

    We live in a magnetic universe with magnetic fields spanning an enormous range of spatial and temporal scales. In particular, magnetic fields at the scale of a galaxy are known as galactic magnetic fields and are the focus of this PhD thesis. These galactic magnetic fields are very important since they affect the dynamics of the interstellar gas as well as the gas distribution. The presence of these magnetic fields induces a certain type of radiation to occur at radio frequencies known as synchrotron radiation. The observed polarization properties of this synchrotron radiation then serves to record the imprint of these magnetic fields. The goal of this thesis has been to infer the structure of the magnetic field across various spatial scales in our own Galaxy as well as the strength and structure of the magnetic field in other galaxies using radiopolarimetric observations.

  19. New detections of CO emission from four spiral galaxies

    NASA Technical Reports Server (NTRS)

    Adler, David S.; Liszt, Harvey S.

    1989-01-01

    A CO survey of external galaxies was conducted to compare observations with computational models of the evolution of the neutral interstellar medium. The paper presents preliminary results of CO detections and mapping in the following systems: NGC 628, 1637, 4258, and 5055. The variation of the velocity dispersion along the major axis versus the radius for NGC 628 is described.

  20. On the local standard of rest. [comoving with young objects in gravitational field of spiral galaxies

    NASA Technical Reports Server (NTRS)

    Yuan, C.

    1983-01-01

    Under the influence of a spiral gravitational field, there should be differences among the mean motions of different types of objects with different dispersion velocities in a spiral galaxy. The old stars with high dispersion velocity should have essentially no mean motion normal to the galactic rotation. On the other hand, young objects and interstellar gas may be moving relative to the old stars at a velocity of a few kilometer per second in both the radial (galacto-centric), and circular directions, depending on the spiral model adopted. Such a velocity is usually referred as the systematic motion or the streaming motion. The conventionally adopted local standard of rest is indeed co-moving with the young objects of the solar vicinity. Therefore, it has a net systematic motion with respect to the circular motion of an equilibrium galactic model, defined by the old stars. Previously announced in STAR as N83-24443

  1. Generation and maintenance of bisymmetric spiral magnetic fields in disk galaxies in differential rotation

    NASA Astrophysics Data System (ADS)

    Sawa, Takeyasu; Fujimoto, M.

    1993-05-01

    The approximate dynamo equation, which yields asymptotic solutions for the large scale bisymmetric spiral (BSS) magnetic fields rotating rigidly over a large area of the galactic disk, is derived. The vertical thickness and the dynamo strength of the gaseous disk which are necessary to generate and sustain the BSS magnetic fields is determined. The globally BSS magnetic fields which propagate over the disk as a wave without being twisted more tightly are reproduced. A poloidal field configuration is theoretically predicted in the halo around the disk, and is observed in the edge-on galaxy NGC4631. Mathematical methods for the galactic dynamo are shown to be equivalent. Those methods give different growth rates between the BSS and the axisymmetric spiral (ASS) magnetic fields in the disk. Magnetohydrodynamical excitation is discussed between the BSS magnetic fields and the two armed spiral density waves.

  2. The JCMT nearby galaxies legacy survey - X. Environmental effects on the molecular gas and star formation properties of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Mok, Angus; Wilson, C. D.; Golding, J.; Warren, B. E.; Israel, F. P.; Serjeant, S.; Knapen, J. H.; Sánchez-Gallego, J. R.; Barmby, P.; Bendo, G. J.; Rosolowsky, E.; van der Werf, P.

    2016-03-01

    We present a study of the molecular gas properties in a sample of 98 H I - flux selected spiral galaxies within ˜25 Mpc, using the CO J = 3 - 2 line observed with the James Clerk Maxwell Telescope. We use the technique of survival analysis to incorporate galaxies with CO upper limits into our results. Comparing the group and Virgo samples, we find a larger mean H2 mass in the Virgo galaxies, despite their lower mean H I mass. This leads to a significantly higher H2 to H I ratio for Virgo galaxies. Combining our data with complementary Hα star formation rate measurements, Virgo galaxies have longer molecular gas depletion times compared to group galaxies, due to their higher H2 masses and lower star formation rates. We suggest that the longer depletion times may be a result of heating processes in the cluster environment or differences in the turbulent pressure. From the full sample, we find that the molecular gas depletion time has a positive correlation with the stellar mass, indicative of differences in the star formation process between low- and high-mass galaxies, and a negative correlation between the molecular gas depletion time and the specific star formation rate.

  3. Megaparsec relativistic jets launched from an accreting supermassive black hole in an extreme spiral galaxy

    SciTech Connect

    Bagchi, Joydeep; Vivek, M.; Srianand, Raghunathan; Gopal-Krishna; Vikram, Vinu; Hota, Ananda; Biju, K. G.; Sirothia, S. K.; Jacob, Joe

    2014-06-20

    The radio galaxy phenomenon is directly connected to mass-accreting, spinning supermassive black holes found in the active galactic nuclei. It is still unclear how the collimated jets of relativistic plasma on hundreds to thousands of kiloparsec scales form and why they are nearly always launched from the nuclei of bulge-dominated elliptical galaxies and not flat spirals. Here we present the discovery of the giant radio source J2345–0449 (z = 0.0755), a clear and extremely rare counterexample where relativistic jets are ejected from a luminous and massive spiral galaxy on a scale of ∼1.6 Mpc, the largest known so far. Extreme physical properties observed for this bulgeless spiral host, such as its high optical and infrared luminosity, large dynamical mass, rapid disk rotation, and episodic jet activity, are possibly the results of its unusual formation history, which has also assembled, via gas accretion from a disk, its central black hole of mass >2 × 10{sup 8} M {sub ☉}. The very high mid-IR luminosity of the galaxy suggests that it is actively forming stars and still building a massive disk. We argue that the launch of these powerful jets is facilitated by an advection-dominated, magnetized accretion flow at a low Eddington rate onto this unusually massive (for a bulgeless disk galaxy) and possibly fast spinning central black hole. Therefore, J2345–0449 is an extremely rare, unusual galactic system whose properties challenge the standard paradigms for black hole growth and the formation of relativistic jets in disk galaxies. Thus, it provides fundamental insight into accretion disk-relativistic jet coupling processes.

  4. VizieR Online Data Catalog: Parameters of Spiral galaxies from SDSS 7 (Hall+, 2012)

    NASA Astrophysics Data System (ADS)

    Hall, M.; Courteau, S.; Dutton, A. A.; McDonald, M.; Zhu, Y.

    2013-08-01

    We have compiled a sample of 3041 spiral galaxies with multiband gri imaging from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7; Abazajian et al., 2009ApJS..182..543A) and available galaxy rotational velocities, V, derived from HI linewidths. We compare the data products provided through the SDSS imaging pipeline with our own photometry of the SDSS images, and use the velocities, V, as an independent metric to determine ideal galaxy sizes (R) and luminosities (L). Our radial and luminosity parameters improve upon the SDSS DR7 Petrosian radii and luminosities through the use of isophotal fits to the galaxy images. This improvement is gauged via VL (Vmag-Luminosity) and RV relations whose respective scatters are reduced by ~8 and ~30% with our parameters compared to similar relations built with SDSS parameters. (1 data file).

  5. Old Star Clusters in Spiral Galaxies: M101 as a Case Study

    NASA Astrophysics Data System (ADS)

    Simanton, Lesley Ann

    2015-01-01

    Most stars form in groups and clusters, at least a small fraction of which can be extremely long-lived. However, many details of how star clusters form and how they disrupt are still unclear. We present and examine a catalog of old star clusters in the nearby spiral galaxy M101, and compare with the known properties of old star clusters in other spiral galaxies. Data include multi-band Hubble Space Telescope images and Gemini-GMOS spectra. Among the properties examined are luminosity distributions, colors, sizes, spatial distributions, and velocities. We highlight the somewhat surprising result of a population of old, disk clusters in M101, which are unlike populations found in the Milky Way and M31.

  6. NGC 7217: A Spheroid-dominated, Early-Type Resonance Ring Spiral Galaxy

    NASA Astrophysics Data System (ADS)

    Buta, R.; van Driel, W.; Braine, J.; Combes, F.; Wakamatsu, K.; Sofue, Y.; Tomita, A.

    1995-09-01

    NGC 7217 is a well-known northern spiral galaxy which is characterized by flocculent spiral structure and a series of three optical ringlike zones: a nuclear ring 21" in diameter, a weak inner ring 63" in diameter, and a striking outer ring 2'.6 in diameter. The rings all have nearly the same shape and position angle in projection. The appearance of the galaxy suggests that it may be more axisymmetric than the typical spiral galaxy, since there is little evidence for the presence of a bar, oval, or stellar density wave. This makes the origin of the ring features uncertain. In an effort to understand this kind of ringed galaxy, which is by no means typical, we have obtained multicolor CCD BVRI images, accurate surface photometry, mappings of the CO and H I gas distributions, and rotational velocities from Hα and H I spectral line data. Our deep surface photometry has revealed an important feature of NGC 7217 that was missed in previous studies: The region occupied by the rings of the galaxy is surrounded by an extensive, nearly circular luminous halo. This halo cannot be merely an extension of the disk component because it is much rounder than the inner regions. Instead, we believe the light represents either the outer regions of the bulge or a separate stellar halo component. We are able to successfully model the luminosity profile in terms of an r114 "spheroid" and an exponential disk with a spheroid-to-total disk (including rings) luminosity ratio of 2.3-2.4. This makes NGC 7217 one of the most spheroid-dominated spirals known, and the finding has important implications for the recent discovery by Merrifield and Kuijken of a significant population of counter-rotating stars in the galaxy. Although the spiral structure of NGC 7217 is flocculent in blue light, there is a definite two-armed stellar spiral in the region of the outer ring. This ring includes about 4.4% of the total blue luminosity and is the locus of most of the recent star formation in the galaxy

  7. Satellites as probes of the masses of spiral galaxies.

    PubMed

    Erickson, L K; Gottesman, S T; Hunter, J H

    1998-12-30

    We present atomic hydrogen (HI) observations and analyses of the kinematics of satellite-primary galaxy pairs. Two estimates for the masses of the primaries are available, one from their rotation curves and one from the orbital properties of the satellites. Defining chi as the ratio of these two mass estimates, it is a measure of the presence, or absence, of a significant halo. The chi distribution is presented and the selection effects are discussed. We show that our data, compared with the more numerous pairs identified by Zaritsky et al., have similar distributions for projected separations of less than 200 kpc, even though the selection criteria employed were quite different. Observational biases have a negligible effect; the biased and unbiased distributions are essentially identical. N-body calculations were executed to simulate the dynamical behavior of relatively low mass satellites orbiting primary disk galaxies with and without extended halos. In addition, we made a partially analytical analysis of the behavior of orbits in a logarithmic potential. We find that a "generic" model, characterized by a single disk-halo combination, cannot reproduce the observed P(chi) distribution. However, a simple two-component population of galaxies, composed of not more than 60% with halos and 40% without halos, is successful, if galaxies have dimensions of order 200 kpc. If galaxies are considerably larger with sizes extending to 400 kpc or more, no generic model can describe the full range of the observed P(chi), particularly if the distribution for r(p) < 200 kpc is compared with that for r(p) > 200 kpc. Regardless of the mix of orbital eccentricities, neither pure halo, nor canonical models (disk and halo masses are comparable within the disk radius) will work. A multicomponent approximation can be constructed; the canonical model must be mixed with a small fraction of systems essentially devoid of a massive dark halo. Only by including these complexities can the full

  8. The Importance of Radial Migration to the Evolution of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Daniel, Kathryne J.; Wyse, Rosemary F. G.

    2016-01-01

    Spiral galaxy evolution is frequently considered in the context of environment, but internal processes may also play an important role. Radial migration is one such internal process, wherein a transient spiral arm rearranges the angular momentum distribution of the disk around corotation without causing kinematic heating. The efficiency of radial migration depends on both the duty cycle for transient patterns and the RMS change in orbital angular momentum induced by each pattern. Should radial migration be efficient, it could cause a substantial fraction of disk stars to move large radial distances over the lifetime of the disk, thus having significant impact on its kinematic, structural and chemical evolution.In this talk, I will summarize a subset of work focusing on the physics that determines the magnitude of the RMS change in orbital angular momentum from each spiral pattern. I have derived an analytic "capture criterion" that predicts whether or not a disk star with finite random orbital energy is in a "trapped orbit" (i.e. the orbital family induced by the spiral pattern that can lead to radial migration). I will present this criterion and show that it is primarily a star's orbital angular momentum that determines whether or not it is in a trapped orbit. The capture criterion could be used to better understand the role of radial migration in N-body simulations as well as applied to models of galaxy evolution. I will describe an example study wherein I applied the capture criterion, in a series of disk galaxy models, to find the fraction of an ensemble of stars that is in trapped orbits. I found that this fraction decreases linearly with increasing radial velocity dispersion and conclude that radial migration may play a role in the evolution of disk galaxies, but it is insignificant to the evolution of high velocity dispersion populations.

  9. Radio continuum and far-infrared emission of spiral galaxies: Implications of correlations

    NASA Technical Reports Server (NTRS)

    Rengarajan, T. N.; Iyengar, K. V. K.

    1990-01-01

    Researchers present a study extending the correlation seen between radio continuum and far-infrared emissions from spiral galaxies to a lower frequency of 408 MHz and also as a function of radio spectral index. The tight correlation seen between the two luminosities is then used to constrain several parameters governing the emissions such as the changes in star formation rate and mass function, frequency of supernovae that are parents of the interstellar electrons and factors governing synchrotron radio emission.

  10. The influence of the cluster environment on the star formation efficiency of 12 Virgo spiral galaxies

    NASA Astrophysics Data System (ADS)

    Vollmer, B.; Wong, O. I.; Braine, J.; Chung, A.; Kenney, J. D. P.

    2012-07-01

    The influence of the environment on gas surface density and star formation efficiency of cluster spiral galaxies is investigated. We extend previous work on radial profiles by a pixel-to pixel analysis looking for asymmetries due to environmental interactions. The star formation rate is derived from GALEX UV and Spitzer total infrared data based on the 8, 24, 70, and 160 μm data. As in field galaxies, the star formation rate for most Virgo galaxies is approximately proportional to the molecular gas mass. Except for NGC 4438, the cluster environment does not affect the star formation efficiency with respect to the molecular gas. Gas truncation is not associated with major changes in the total gas surface density distribution of the inner disk of Virgo spiral galaxies. In three galaxies (NGC 4430, NGC 4501, and NGC 4522), possible increases in the molecular fraction and the star formation efficiency with respect to the total gas, of factors of 1.5 to 2, are observed on the windward side of the galactic disk. A significant increase of the star formation efficiency with respect to the molecular gas content on the windward side of ram pressure-stripped galaxies is not observed. The ram-pressure stripped extraplanar gas of 3 highly inclined spiral galaxies (NGC 4330, NGC 4438, and NGC 4522) shows a depressed star formation efficiency with respect to the total gas, and one of them (NGC 4438) shows a depressed rate even with respect to the molecular gas. The interpretation is that stripped gas loses the gravitational confinement and associated pressure of the galactic disk, and the gas flow is diverging, so the gas density decreases and the star formation rate drops. We found two such regions of low star formation efficiency in the more face-on galaxies NGC 4501 and NGC 4654 which are both undergoing ram pressure stripping. These regions show low radio continuum emission or unusually steep radio spectral index. However, the stripped extraplanar gas in one highly inclined

  11. Global-, local-, and intermediate-scale structures in prototype spiral galaxies

    NASA Technical Reports Server (NTRS)

    Roberts, William W., Jr.

    1993-01-01

    The relationship between galactic spiral structure and the matter in the underlying disk constitutes one of the central problems in galactic dynamics. In Bertin et al. (1989), disk matter characterized by a low-dispersive speed is shown to be capable of playing a key role in the generation of large-scale spiral structure. In Roberts et al. (1992), this self-gravitating, low-dispersion disk matter is shown to be capable of playing an essential role in the formation of structure on local and intermediate scales. Both in computed cases where large-scale spiral structure is present and in those where it is not, the same dominant physical processes and fundamental dynamical mechanisms are active on local scales. The new perception, in which large-scale and small-scale phenomena operate somewhat independently as evidenced in the computational studies, permits a range of flocculent, multiarmed, and grand design spiral types to be simulated. In particular, grand design galaxies with ragged appearances exhibiting spurs, arm branchings, and interarm bridges in addition to the major spiral arms, similar to those often observed, can be generated.

  12. SUSTAINING STAR FORMATION RATES IN SPIRAL GALAXIES: SUPERNOVA-DRIVEN TURBULENT ACCRETION DISK MODELS APPLIED TO THINGS GALAXIES

    SciTech Connect

    Vollmer, Bernd; Leroy, Adam K.

    2011-01-15

    Gas disks of spiral galaxies can be described as clumpy accretion disks without a coupling of viscosity to the actual thermal state of the gas. The model description of a turbulent disk consisting of emerging and spreading clumps contains free parameters, which can be constrained by observations of molecular gas, atomic gas, and the star formation rate for individual galaxies. Radial profiles of 18 nearby spiral galaxies from THINGS, HERACLES, SINGS, and GALEX data are used to compare the observed star formation efficiency, molecular fraction, and velocity dispersion to the model. The observed radially decreasing velocity dispersion can be reproduced by the model. In the framework of this model, the decrease in the inner disk is due to the stellar mass distribution which dominates the gravitational potential. Introducing a radial break in the star formation efficiency into the model improves the fits significantly. This change in the star formation regime is realized by replacing the free-fall time in the prescription of the star formation rate with the molecule formation timescale. Depending on the star formation prescription, the break radius is located near the transition region between the molecular-gas-dominated and atomic-gas-dominated parts of the galactic disk or closer to the optical radius. It is found that only less massive galaxies (log M(M{sub sun}) {approx}< 10) can balance gas loss via star formation by radial gas accretion within the disk. These galaxies can thus access their gas reservoirs with large angular momentum. On the other hand, the star formation of massive galaxies is determined by the external gas mass accretion rate from a putative spherical halo of ionized gas or from satellite accretion. In the absence of this external accretion, star formation slowly exhausts the gas within the optical disk within the star formation timescale.

  13. Giant Molecular Clouds and Star Formation in the Non-Grand Design Spiral Galaxy NGC 6946

    NASA Astrophysics Data System (ADS)

    Rebolledo, David; Wong, Tony; Leroy, Adam

    2011-10-01

    Although the internal physical properties of molecular clouds have been extensively studied (Solomon et al. 1987), a more detailed understanding of their origin and evolution in different types of galaxies is needed. In order to disentangle the details of this process, we performed CO(1→0) CARMA observations of the eastern part of the multi-armed galaxy NGC 6946. Our goal was to determine if azimuthal segregation of various gas and star formation tracers occurs in this kind of spiral galaxy (Tamburro et al. 2008). Although we found no evidence of an angular offset between molecular gas, atomic gas and star formation regions in our observations, we observe a clear radial progression from regions where molecular gas dominates over atomic gas (for r ≤ 2.8 kpc) to regions where the gas becomes mainly atomic (5.6 kpc ≤ r ≤ 7.6 kpc) when azimuthally averaged. In addition, we found that the densest concentrations of molecular gas are located on arms, particularly where they appear to intersect. This result is in concordance with the behavior predicted by simulations of the spiral galaxies with an active potential (Clarke & Gittins 2006; Dobbs & Bonnell 2008). Since NGC 6946 is located at a distance of 5.5 Mpc, the linear resolution of the map corresponds to 140 pc. At such resolution, we were able to find CO emitting complexes with masses greater than those of typical Giant Molecular Clouds (105-106 M⊙). To identify GMCs individually and make a more detailed study of their physical properties, we made D array observations of CO(2→1) toward the densest concentrations of gas located in the prominent spiral arms. We achieved a linear resolution of 50 pc at 1 mm in D array, similar to GMCs sizes found in other galaxies (Bolatto et al. 2008). We present first results about possible differences in the properties of the on-arm clouds and the inter-arm clouds. While inter-arm GMAs in grand-design galaxies are thought to be formed by fragmentation of more massive on

  14. The role of the corotation resonance in the secular evolution of disks of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Lépine, J. R. D.; Scarano, S., Jr.; Barros, D. A.; Junqueira, T. C.; Dias, W. S.; Andrievsky, S.

    2014-10-01

    The corotation resonance plays an important role in the evolution of the disks of spiral galaxies, and in particular, of our Galaxy. Its effect on the chemical abundance gradients is even a tool to estimate the age of the present spiral arm structure, which we find to be long-lived, contrary to a recent common belief. The metallicity gradients usually decrease in the inner regions and become flat or rising at larger radii. In several galaxies, including the Milky Way, one observes not only a change in the slope of the abundance gradient, but also an abrupt step in metallicity at corotation. This step is because the corotation resonance separates the disk of a galaxy in two regions (inside corotation and outside corotation) which are isolated one from the other, so that the two sides evolve in an independent way. The barrier between the two regions is the result of the flow of gas in opposite directions on the two sides and by the ring-shaped void of gas observed at corotation. We investigated a sample of galaxies, which have a known corotation radius, and for which there are measurements of abundance gradients of Oxygen available in the literature. A very good correlation is found between corotation radii and the radii at which there is a break in the slope of the gradients. Besides this, an independent effect of corotation is a minimum of star formation associated with the minimum velocity at which the interstellar gas feeds the spiral arms (seen as potential wells and star-formation machines). Still another effect is the scattering of stars by the resonance, which causes their migration to different galactic radii.

  15. METALLICITY GRADIENT OF A LENSED FACE-ON SPIRAL GALAXY AT REDSHIFT 1.49

    SciTech Connect

    Yuan, T.-T.; Kewley, L. J.; Swinbank, A. M.; Richard, J.; Livermore, R. C.

    2011-05-01

    We present the first metallicity gradient measurement for a grand-design face-on spiral galaxy at z {approx} 1.5. This galaxy has been magnified by a factor of 22x by a massive, X-ray luminous galaxy cluster MACS J1149.5+2223 at z = 0.544. Using the Laser Guide Star Adaptive Optics aided integral field spectrograph OSIRIS on KECK II, we target the H{alpha} emission and achieve a spatial resolution of 0.''1, corresponding to a source-plane resolution of 170 pc. The galaxy has well-developed spiral arms and the nebular emission line dynamics clearly indicate a rotationally supported disk with V{sub rot}/{sigma} {approx} 4. The best-fit disk velocity field model yields a maximum rotation of V{sub rot}sin i = 150 {+-} 15 km s{sup -1}, and a dynamical mass of M{sub dyn} = (1.3 {+-} 0.2) x 10{sup 10} cosec{sup 2}(i) M{sub sun} (within 2.5 kpc), where the inclination angle i = 45{sup 0} {+-} 10{sup 0}. Based on the [N II] and H{alpha} ratios, we measured the radial chemical abundance gradient from the inner hundreds of parsecs out to {approx}5 kpc. The slope of the gradient is -0.16 {+-} 0.02 dex kpc{sup -1}, significantly steeper than the gradient of late-type or early-type galaxies in the local universe. If representative of disk galaxies at z {approx} 1.5, our results support an 'inside-out' disk formation scenario in which early infall/collapse in the galaxy center builds a chemically enriched nucleus, followed by slow enrichment of the disk over the next 9 Gyr.

  16. Bulge-disc decompositions and structural bimodality of Ursa Major cluster spiral galaxies

    NASA Astrophysics Data System (ADS)

    McDonald, Michael; Courteau, Stéphane; Tully, R. Brent

    2009-02-01

    We present bulge and disc (B/D) decompositions of existing K' surface brightness profiles for 65 Ursa Major (UMa) cluster spiral galaxies. This improves upon the disc-only fits of Tully et al. The 1996 disc fits were used by Tully & Verheijen for their discovery of the bimodality of structural parameters in the UMa cluster galaxies. It is shown that our new one-dimensional B/D decompositions yield disc structural parameters that differ only slightly from the basic fits of Tully et al. and evidence for structural bimodality of UMa galaxies is maintained. Our B/D software for the decomposition of one-dimensional surface brightness profiles of galaxies uses a non-linear minimization scheme to recover the best-fitting Sérsic bulge and the exponential disc while accounting for the possible presence of a compact nucleus and spiral arms and for the effects of seeing and disc truncations. In agreement with Tully & Verheijen, we find that the distribution of near-infrared disc central surface brightnesses is bimodal with an F-test confidence of 80 per cent. There is also strong evidence for a local minimum in the luminosity function at . A connection between the brightness bimodality and a dynamical bimodality, based on new HI linewidths, is identified. The B/D parameters are presented in Table 1.

  17. Unveiling the sources of disk heating in spiral galaxies with the CALIFA survey

    NASA Astrophysics Data System (ADS)

    Pinna, F.; Falcón-Barroso, J.; Martig, M.; van de Ven, G.; Lyubenova, M.; Leaman, R.

    2016-06-01

    The stellar velocity ellipsoid (SVE) quantifies the amount of velocity dispersion in the vertical, radial and azimuthal directions. Since different disk heating mechanisms (e.g. spiral arms, giant molecular clouds, mergers, etc) affect these components differently, the SVE can constrain the sources of heating in disk galaxies. At present the 3D nature of the SVE can only be directly measured in the Milky Way but, thanks to integral-field surveys like CALIFA, we are now in position to carry out the same kind of analysis in external galaxies. For this purpose, we have gathered a sample of ~30 intermediate inclined spiral galaxies along the Hubble sequence (S0 to Scd types) with high quality stellar kinematic maps. This allows us to probe the SVE for each galaxy from different line-of-sights in different regions, and thus provide strong constraints on its shape. In this presentation we relate our preliminary findings to realistic numerical simulations of disks with different formation histories (quiescent vs mergers), and to results of previous works.

  18. Are passive red spirals truly passive?. The current star formation activity of optically red disc galaxies

    NASA Astrophysics Data System (ADS)

    Cortese, L.

    2012-07-01

    We used GALEX ultraviolet and WISE 22 μm observations to investigate the current star formation activity of the optically red spirals recently identified as part of the Galaxy Zoo project. These galaxies were accurately selected from the Sloan Digital Sky Survey as pure discs with low or no current star formation activity, representing one of the best optically selected samples of candidate passive spirals. However, we show that these galaxies are not only still forming stars at a significant rate (≳1 M⊙ yr-1) but, more importantly, their star formation activity is not different from that of normal star-forming discs of the same stellar mass (M∗ ≳ 1010.2 M⊙). Indeed, these systems lie on the UV-optical blue sequence, even without any corrections for internal dust attenuation, and they follow the same specific star formation rate vs. stellar mass relation of star-forming galaxies. Our findings clearly show that at high stellar masses, optical colours do not allow to distinguish between actively star-forming and truly quiescent systems.

  19. THE SPLASH SURVEY: INTERNAL KINEMATICS, CHEMICAL ABUNDANCES, AND MASSES OF THE ANDROMEDA I, II, III, VII, X, AND XIV DWARF SPHEROIDAL GALAXIES {sup ,}

    SciTech Connect

    Kalirai, Jason S.; Beaton, Rachael L.; Majewski, Steven R.; Ostheimer, James C.; Patterson, Richard J.; Geha, Marla C.; Gilbert, Karoline M.; Guhathakurta, Puragra; Kirby, Evan N.

    2010-03-10

    We present new Keck/DEIMOS spectroscopic observations of hundreds of individual stars along the sightline to the first three of the Andromeda (M31) dwarf spheroidal (dSph) galaxies to be discovered, And I, II, and III, and combine them with recent spectroscopic studies by our team of three additional M31 dSphs, And VII, X, and XIV, as a part of the SPLASH Survey (Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo). Member stars of each dSph are isolated from foreground Milky Way dwarf stars and M31 field contamination using a variety of photometric and spectroscopic diagnostics. Our final spectroscopic sample of member stars in each dSph, for which we measure accurate radial velocities with a median uncertainty (random plus systematic errors) of 4-5 km s{sup -1}, includes 80 red giants in And I, 95 in And II, 43 in And III, 18 in And VII, 22 in And X, and 38 in And XIV. The sample of confirmed members in the six dSphs is used to derive each system's mean radial velocity, intrinsic central velocity dispersion, mean abundance, abundance spread, and dynamical mass. This combined data set presents us with a unique opportunity to perform the first systematic comparison of the global properties (e.g., metallicities, sizes, and dark matter masses) of one-third of Andromeda's total known dSph population with Milky Way counterparts of the same luminosity. Our overall comparisons indicate that the family of dSphs in these two hosts have both similarities and differences. For example, we find that the luminosity-metallicity relation is very similar between L {approx} 10{sup 5} and 10{sup 7} L{sub sun}, suggesting that the chemical evolution histories of each group of dSphs are similar. The lowest luminosity M31 dSphs appear to deviate from the relation, possibly suggesting tidal stripping. Previous observations have noted that the sizes of M31's brightest dSphs are systematically larger than Milky Way satellites of similar luminosity. At lower luminosities

  20. A New Method to Estimate Local Pitch Angles in Spiral Galaxies: Application to Spiral Arms and Feathers in M81 and M51

    NASA Astrophysics Data System (ADS)

    Puerari, Ivânio; Elmegreen, Bruce G.; Block, David L.

    2014-12-01

    We examine 8 μ m IRAC images of the grand design two-arm spiral galaxies M81 and M51 using a new method whereby pitch angles are locally determined as a function of scale and position, in contrast to traditional Fourier transform spectral analyses which fit to average pitch angles for whole galaxies. The new analysis is based on a correlation between pieces of a galaxy in circular windows of (ln R,θ ) space and logarithmic spirals with various pitch angles. The diameter of the windows is varied to study different scales. The result is a best-fit pitch angle to the spiral structure as a function of position and scale, or a distribution function of pitch angles as a function of scale for a given galactic region or area. We apply the method to determine the distribution of pitch angles in the arm and interarm regions of these two galaxies. In the arms, the method reproduces the known pitch angles for the main spirals on a large scale, but also shows higher pitch angles on smaller scales resulting from dust feathers. For the interarms, there is a broad distribution of pitch angles representing the continuation and evolution of the spiral arm feathers as the flow moves into the interarm regions. Our method shows a multiplicity of spiral structures on different scales, as expected from gas flow processes in a gravitating, turbulent and shearing interstellar medium. We also present results for M81 using classical 1D and 2D Fourier transforms, together with a new correlation method, which shows good agreement with conventional 2D Fourier transforms.

  1. A new method to estimate local pitch angles in spiral galaxies: Application to spiral arms and feathers in M81 and M51

    SciTech Connect

    Puerari, Ivânio; Elmegreen, Bruce G.; Block, David L.

    2014-12-01

    We examine 8 μm IRAC images of the grand design two-arm spiral galaxies M81 and M51 using a new method whereby pitch angles are locally determined as a function of scale and position, in contrast to traditional Fourier transform spectral analyses which fit to average pitch angles for whole galaxies. The new analysis is based on a correlation between pieces of a galaxy in circular windows of (lnR,θ) space and logarithmic spirals with various pitch angles. The diameter of the windows is varied to study different scales. The result is a best-fit pitch angle to the spiral structure as a function of position and scale, or a distribution function of pitch angles as a function of scale for a given galactic region or area. We apply the method to determine the distribution of pitch angles in the arm and interarm regions of these two galaxies. In the arms, the method reproduces the known pitch angles for the main spirals on a large scale, but also shows higher pitch angles on smaller scales resulting from dust feathers. For the interarms, there is a broad distribution of pitch angles representing the continuation and evolution of the spiral arm feathers as the flow moves into the interarm regions. Our method shows a multiplicity of spiral structures on different scales, as expected from gas flow processes in a gravitating, turbulent and shearing interstellar medium. We also present results for M81 using classical 1D and 2D Fourier transforms, together with a new correlation method, which shows good agreement with conventional 2D Fourier transforms.

  2. Magnetic fields in the nearby spiral galaxy IC 342: A multi-frequency radio polarization study

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    2015-06-01

    Context. Magnetic fields play an important role in the formation and stabilization of spiral structures in galaxies, but the interaction between interstellar gas and magnetic fields has not yet been understood. In particular, the phenomenon of "magnetic arms" located between material arms is a mystery. Aims: The strength and structure of interstellar magnetic fields and their relation to spiral arms in gas and dust are investigated in the nearby and almost face-on spiral galaxy IC 342. Methods: The total and polarized radio continuum emission of IC 342 was observed with high spatial resolution in four wavelength bands with the Effelsberg and VLA telescopes. At λ6.2 cm the data from both telescopes were combined. I separated thermal and nonthermal (synchrotron) emission components with the help of the spectral index distribution and derived maps of the magnetic field strength, degree of magnetic field order, magnetic pitch angle, Faraday rotation measure, and Faraday depolarization. Results: IC 342 hosts a diffuse radio disk with an intensity that decreases exponentially with increasing radius. The frequency dependence of the scalelength of synchrotron emission indicates energy-dependent propagation of the cosmic-ray electrons, probably via the streaming instability. The equipartition strength of the total field in the main spiral arms is typically 15 μG, that of the ordered field about 5 μG. The total radio emission, observed with the VLA's high resolution, closely follows the dust emission in the infrared at 8 μm (Spitzer telescope) and 22 μm (WISE telescope). The polarized emission is not diffuse, but concentrated in spiral arms of various types: (1) a narrow arm of about 300 pc width, displaced inwards with respect to the eastern arm by about 200 pc, indicating magnetic fields compressed by a density wave; (2) a broad arm of 300-500 pc width around the northern arm with systematic variations in polarized emission, polarization angles, and Faraday rotation

  3. The Globular Cluster Systems of Five Nearby Spiral Galaxies: New Insights from Hubble Space Telescope Imaging

    NASA Astrophysics Data System (ADS)

    Chandar, Rupali; Whitmore, Bradley; Lee, Myung Gyoon

    2004-08-01

    We use available multifilter Hubble Space Telescope (HST) WFPC2 imaging of five (M81, M83, NGC 6946, M101, and M51, in order of distance) low-inclination, nearby spiral galaxies to study ancient star cluster populations. Combining rigorous selection criteria to reject contaminants (individual stars, background galaxies, and blends) with optical photometry including the U bandpass, we unambiguously detect ancient globular cluster (GC) systems in each galaxy. We present luminosities, colors, and size (effective radius) measurements for our candidate GCs. These are used to estimate specific frequencies, to assess whether intrinsic color distributions are consistent with the presence of both metal-poor and metal-rich GCs, and to compare relative sizes of ancient clusters between different galaxy systems. M81 globulars have intrinsic color distributions that are very similar to those in the Milky Way and M31, with ~40% of sample clusters having colors expected for a metal-rich population. The GC system in M51 meanwhile, appears almost exclusively blue and metal-poor. This lack of metal-rich GCs associated with the M51 bulge indicates that the bulge formation history of this Sbc galaxy may have differed significantly from that of our own. Ancient clusters in M101 and possibly in NGC 6946, two of the three later type spirals in our sample, appear to have luminosity distributions that continue to rise to our detection limit (MV~-6.0), well beyond the expected turnover (MV~-7.4) in the luminosity function. This is reminiscent of the situation in M33, a Local Group galaxy of similar Hubble type. The faint ancient cluster candidates in M101 and NGC 6946 have properties (colors and reff) similar to their more luminous counterparts, and we suggest that these are either intermediate-age (3-9 Gyr) disk clusters or the low-mass end of the original GC population. Potentially, these lower mass clusters were not destroyed because of different dynamical conditions relative to those

  4. 2MASS photometry of edge-on spiral galaxies - I. Sample and general results

    NASA Astrophysics Data System (ADS)

    Mosenkov, A. V.; Sotnikova, N. Ya.; Reshetnikov, V. P.

    2010-01-01

    A sample of edge-on spiral galaxies aimed at a thorough study of the main structural and photometric parameters of edge-on galaxies, both of early- and late-types, is presented. The data were taken from the Two Micron All Sky Survey (2MASS) in the J, H and Ks filters. The sources were selected according to their angular size mainly on the basis of the 2MASS-selected Flat Galaxy Catalog (2MFGC). The sample consists of 175 galaxies in the Ks filter, 169 galaxies in the H filter and 165 galaxies in the J filter. We present bulge and disc decompositions of each galaxy image. All galaxies have been modelled with a Sérsic bulge and exponential disc with the BUDDA v2.1 package. Bulge and disc sizes, profile shapes, surface brightnesses are provided. Our sample is the biggest up-to-date sample of edge-on galaxies with derived structural parameters for discs and bulges. In this paper, we present the general results of the study of this sample. We determine several scaling relations for bulges and discs which indicate a tight link between their formation and evolution. We show that galaxies with bulges fitted by the Sérsic index n <~ 2 have quite different distributions of their structural parameters than galaxies with n >~ 2 bulges. At a first approximation the Sérsic index threshold n ~= 2 can be used to identify pseudobulges and classical bulges. Thus, the difference in parameter distributions and scaling relations for these subsamples suggests that two or more processes are responsible for disc galaxy formation. The main conclusions of our general statistical analysis of the sample are as follows. (i) The distribution of the apparent bulge axis ratio qb for the subsample with n <~ 2 can be attributed to triaxial, nearly prolate bulges that are seen from different projections, while n >~ 2 bulges seem to be oblate spheroids with moderate flattening. Triaxiality of late-type bulges may be due to the presence of a bar that thickened in the vertical direction during its

  5. Properties of the giant H II regions and bar in the nearby spiral galaxy NGC 5430

    NASA Astrophysics Data System (ADS)

    Brière, É.; Cantin, S.; Spekkens, K.

    2012-09-01

    In order to better understand the impact of the bar on the evolution of spiral galaxies, we measure the properties of giant H II regions and the bar in the SB(s)b galaxy NGC 5430. We use two complementary data sets, both obtained at the Observatoire du Mont-Mégantic: a hyperspectral data cube from the imaging Fourier transform spectrograph SpIOMM (Spectromètre-Imageur à transformée de Fourier de l-Observatoire du Mont-Mégantic) and high-resolution spectra across the bar from a long-slit spectrograph. We flux-calibrate SpIOMM spectra for the first time, and produce Hα and [N II]λ6584 Å intensity maps from which we identify 51 giant H II regions in the spiral arms and bar. We evaluate the type of activity, the oxygen abundance and the age of the young populations contained in these giant H II regions and in the bar. Thus, we confirm that NGC 5430 does not harbour a strong active galactic nucleus, and that its Wolf-Rayet knot shows a pure H II region nature. We find no variation in abundance or age between the bar and spiral arms, nor as a function of galactocentric radius. These results are consistent with the hypothesis that a chemical mixing mechanism is at work in the galaxy's disc to flatten the oxygen abundance gradient. Using the STARBURST99 model, we estimate the ages of the young populations, and again find no variations in age between the bar and the arms or as a function of radius. Instead, we find evidence for two galaxy-wide waves of star formation, about 7.1 and 10.5 Myr ago. While the bar in NGC 5430 is an obvious candidate to trigger these two episodes, it is not clear how the bar could induce widespread star formation on such a short time-scale.

  6. Investigating the Nuclear Activity of Barred Spiral Galaxies: The Case of NGC 1672

    NASA Technical Reports Server (NTRS)

    Jenkins, L. P.; Brandt, W. N.; Colbert, E. J.; Koribalski, B.; Kuntz, K. D.; Levan, A. J.; Ojha, R.; Roberts, T. P.; Ward, M. J.; Zezas, A.

    2011-01-01

    We have performed an X-ray study of the nearby barred spiral galaxy NGC 1672, primarily to ascertain the effect of the bar on its nuclear activity. We use both Chandra and XMM-Newton observations to investigate its X-ray properties, together with supporting high-resolution optical imaging data from the Hubble Space Telescope (HST) infrared imaging from the Spitzer Space Telescope, and Australia Telescope Compact Array ground-based radio data. We detect 28 X-ray sources within the D25 area of the galaxy; many are spatially correlated with star formation in the bar and spiral arms, and two are identified as background galaxies in the HST images. Nine of the X-ray sources are ultraluminous X-ray sources, with the three brightest (LX 5 * 10(exp 39) erg s(exp -1)) located at the ends of the bar. With the spatial resolution of Chandra, we are able to show for the first time that NGC 1672 possesses a hard (1.5) nuclear X-ray source with a 2-10 keV luminosity of 4 * 10(exp 38) erg s(exp -1). This is surrounded by an X-ray-bright circumnuclear star-forming ring, comprised of point sources and hot gas, which dominates the 2-10 keV emission in the central region of the galaxy. The spatially resolved multiwavelength photometry indicates that the nuclear source is a low-luminosity active galactic nucleus (LLAGN), but with star formation activity close to the central black hole. A high-resolution multiwavelength survey is required to fully assess the impact of both large-scale bars and smaller-scale phenomena such as nuclear bars, rings, and nuclear spirals on the fueling of LLAGN.

  7. Star formation histories across the interacting galaxy NGC 6872, the largest-known spiral

    SciTech Connect

    Eufrasio, Rafael T.; De Mello, Duilia F.; Dwek, Eli; Arendt, Richard G.; Benford, Dominic J.; Gadotti, Dimitri A.; Urrutia-Viscarra, Fernanda; De Oliveira, Claudia Mendes

    2014-11-01

    NGC 6872, hereafter the Condor, is a large spiral galaxy that is interacting with its closest companion, the S0 galaxy IC 4970. The extent of the Condor provides an opportunity for detailed investigation of the impact of the interaction on the current star formation rate and its history across the galaxy, on the age and spatial distribution of its stellar population, and on the mechanism that drives the star formation activity. To address these issues we analyzed the far-ultraviolet (FUV) to near-infrared (near-IR) spectral energy distribution of seventeen 10 kpc diameter regions across the galaxy, and derived their star formation history, current star formation rate, and stellar population and mass. We find that most of the star formation takes place in the extended arms, with very little star formation in the central 5 kpc of the galaxy, in contrast to what was predicted from previous numerical simulations. There is a trend of increasing star formation activity with distance from the nucleus of the galaxy, and no evidence for a recent increase in the current star formation rate due to the interaction. The nucleus itself shows no significant current star formation activity. The extent of the Condor also provides an opportunity to test the applicability of a single standard prescription for conversion of the FUV + IR (22 μm) intensities to a star formation rate for all regions. We find that the conversion factor differs from region to region, arising from regional differences in the stellar populations.

  8. STAR Formation Histories Across the Interacting Galaxy NGC 6872, the Largest-Known Spiral

    NASA Technical Reports Server (NTRS)

    Eufrasio, Rafael T.; Dwek, E.; Arendt, RIchard G.; deMello, Duilia F.; Gadotti, DImitri A.; Urrutia-Viscarra, Fernanda; deOliveira, CLaudia Mendes; Benford, Dominic J.

    2014-01-01

    NGC6872, hereafter the Condor, is a large spiral galaxy that is interacting with its closest companion, the S0 galaxy IC 4970. The extent of the Condor provides an opportunity for detailed investigation of the impact of the interaction on the current star formation rate and its history across the galaxy, on the age and spatial distribution of its stellar population, and on the mechanism that drives the star formation activity. To address these issues we analyzed the far-ultraviolet (FUV) to near-infrared (near-IR) spectral energy distribution of seventeen 10 kpc diameter regions across the galaxy, and derived their star formation history, current star formation rate, and stellar population and mass. We find that most of the star formation takes place in the extended arms, with very little star formation in the central 5 kpc of the galaxy, in contrast to what was predicted from previous numerical simulations. There is a trend of increasing star formation activity with distance from the nucleus of the galaxy, and no evidence for a recent increase in the current star formation rate due to the interaction. The nucleus itself shows no significant current star formation activity. The extent of the Condor also provides an opportunity to test the applicability of a single standard prescription for conversion of the FUV + IR (22 micrometer) intensities to a star formation rate for all regions. We find that the conversion factor differs from region to region, arising from regional differences in the stellar populations.

  9. Star Formation Driven Outflows In Edge-On Spiral Galaxies Based on HST/ACS Observations

    NASA Astrophysics Data System (ADS)

    Rossa, Joern; Dahlem, M.; Dettmar, R.; van der Marel, R. P.

    2007-12-01

    We present new results on extraplanar diffuse ionized gas (eDIG) in four late-type, actively star-forming edge-on spirals. The high spatial resolution narrowband imaging observations were obtained with ACS on-board HST. Our H-alpha observations reveal a multitude of structures on both small and large scales. Whereas all four galaxies have been studied with ground-based telescopes before, here the small scale structure of the extended emission line gas is presented for the very first time at a spatial resolution of 0.05", corresponding to 5 pc at the mean distance to our galaxies. The eDIG morphology is very different for all four targets, as a result of their different star formation activity and galaxy mass. There is a very smooth DIG morphology observed in two of the galaxies (NGC4634 and NGC5775), whereas the other two (NGC4700 and NGC7090) show a much more complex morphology with intricate filaments, bubbles and supershells. We discuss how the morphology of the eDIG, in particular the break-up of diffuse emission into filaments in galaxy halos, depends on physical parameters such as galaxy mass and SF activity and other tracers as well as the galactic environment. Support for proposal 10416 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  10. The Red Spiral Galaxy UGC11680: Clues for the Inside-Out Quenching.

    NASA Astrophysics Data System (ADS)

    Bárcenas, J.; Sanchez, S. F.

    2016-06-01

    Broadly, galaxies can be divided in two groups, thanks to the Color-Magnitude Diagram: the lively star formation ones, ``The blue Cloud'' and galaxies which halted their star formation, ``The Red Sequence''. It is a currently accepted that the galaxies start their lifespan as a blue objects, turning red when they stop to assembly more mass and thus more stars. Nevertheless, This change need to be quick (˜ 1 Gyr), due to the dearth of galaxies between this two populations (the so called ``green valley'').Previous works have found two distinct stellar mass assembly modes, they are termed as ``the inside-out'' and ``the outside-in'' growth scenarios in the literature. In the ``inside-out'' scenario, mass assembly is finished in the galactic central region. In some cases, the inflow gas can fuel the central SuperMassive BlackHole. The subsequent AGN feedback will then shut-off the central star formation. One possible case of this scenario is the galaxy UGC11680, an unusual face-on red spiral galaxy with an AGN type 2, at the red sequence belonging to the CALIFA survey. We used the so called fossil method to study its star formation history and try to understand what happened to its stellar populations.

  11. OT2_bsmith_3: Spirals, Bridges, and Tails: The Herschel View of Dust in Interacting Galaxies

    NASA Astrophysics Data System (ADS)

    Smith, B.

    2011-09-01

    The tidal features produced by gravitational interactions between galaxies may contribute significantly to the enrichment of the intergalactic medium in dust and heavy elements. However, at the present time little is known about the dust content and properties of tidal structures. To address this lack, we propose to use the PACS and SPIRE instruments on Herschel to image a sample of nine nearby interacting galaxies in six far-infrared/submm broadband filters. We will map the dust column density and temperature in the main bodies and tidal features of these galaxies, and compare the far-infrared/submm properties of these features with those of normal spirals and dwarf galaxies. We will compare the Herschel maps with already acquired GALEX UV, Spitzer IR, and ground-based optical data, and with population synthesis and radiative transfer codes, to investigate dust heating mechanisms and extinction in these galaxies. We will compare with available radio maps to investigate dust/gas ratios and star formation triggering mechanisms, and compare with numerical simulations of the interactions. Our sample includes the closest and best-studied examples of tidal dwarf galaxies and accretion-driven star formation. These will provide a good testbed for interpreting high redshift systems.

  12. Strong Evidence for the Density-wave Theory of Spiral Structure in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Pour-Imani, Hamed; Kennefick, Daniel; Kennefick, Julia; Davis, Benjamin L.; Shields, Douglas W.; Shameer Abdeen, Mohamed

    2016-08-01

    The density-wave theory of galactic spiral-arm structure makes a striking prediction that the pitch angle of spiral arms should vary with the wavelength of the galaxy’s image. The reason is that stars are born in the density wave but move out of it as they age. They move ahead of the density wave inside the co-rotation radius, and fall behind outside of it, resulting in a tighter pitch angle at wavelengths that image stars (optical and near-infrared) than those that are associated with star formation (far-infrared and ultraviolet). In this study we combined large sample size with wide range of wavelengths, from the ultraviolet to the infrared to investigate this issue. For each galaxy we used an optical wavelength image (B-band: 445 nm) and images from the Spitzer Space Telescope at two infrared wavelengths (infrared: 3.6 and 8.0 μm) and we measured the pitch angle with the 2DFFT and Spirality codes. We find that the B-band and 3.6 μm images have smaller pitch angles than the infrared 8.0 μm image in all cases, in agreement with the prediction of density-wave theory. We also used images in the ultraviolet from Galaxy Evolution Explorer, whose pitch angles agreed with the measurements made at 8 μm.

  13. Gaseous Structures and Mass Drift in Spiral Galaxies: Effects of Arm Strength

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Kim, W.-T.

    2015-10-01

    Stellar spiral arms in disk galaxies play an important role in the formation of gaseous substructures such as gaseous feathers as well as mass inflows/outflows in the radial direction. We study nonlinear responses of self-gravitating gas to an imposed stellar spiral potential in galactic disks with differing arm strength and pattern speed. We find that the extent and shapes of gaseous arms as well as the radial mass drift rate depend rather sensitively on the arm pattern speed. Quasi-steady spiral shocks can exist only when the normal Mach number is small. The pitch angle of gaseous arms is usually smaller than that of stellar arms. The mass drift rate to the central region is in the range of ˜0.05-3.0M⊙yr-1 , with larger values corresponding to stronger and/or slower-rotating arms. Using a normal-mode linear stability analysis together with nonlinear simulations, we show that wiggle instability of spiral shocks is due to the accumulation of potential vorticity at a perturbed shock front, rather than Kelvin-Helmholtz instability as previously suggested.

  14. PLANETARY NEBULAE IN FACE-ON SPIRAL GALAXIES. III. PLANETARY NEBULA KINEMATICS AND DISK MASS

    SciTech Connect

    Herrmann, Kimberly A.; Ciardullo, Robin E-mail: rbc@astro.psu.ed

    2009-11-10

    Much of our understanding of dark matter halos comes from the assumption that the mass-to-light ratio (Y) of spiral disks is constant. The best way to test this hypothesis is to measure the disk surface mass density directly via the kinematics of old disk stars. To this end, we have used planetary nebulae (PNe) as test particles and have measured the vertical velocity dispersion (sigma{sub z}) throughout the disks of five nearby, low-inclination spiral galaxies: IC 342, M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), and M101 (NGC 5457). By using H I to map galactic rotation and the epicyclic approximation to extract sigma{sub z} from the line-of-sight dispersion, we find that, with the lone exception of M101, our disks do have a constant Y out to approx3 optical scale lengths (h{sub R} ). However, once outside this radius, sigma{sub z} stops declining and becomes flat with radius. Possible explanations for this behavior include an increase in the disk mass-to-light ratio, an increase in the importance of the thick disk, and heating of the thin disk by halo substructure. We also find that the disks of early type spirals have higher values of Y and are closer to maximal than the disks of later-type spirals, and that the unseen inner halos of these systems are better fit by pseudo-isothermal laws than by NFW models.

  15. Hubble Space Telescope Imaging of the Circumnuclear Environments of the CfA Seyfert Galaxies: Nuclear Spirals and Fueling

    NASA Technical Reports Server (NTRS)

    Pogge, Richard W.; Martini, Paul

    2002-01-01

    We present archival Hubble Space Telescope (HST) images of the nuclear regions of 43 of the 46 Seyfert galaxies found in the volume limited,spectroscopically complete CfA Redshift Survey sample. Using an improved method of image contrast enhancement, we created detailed high-quality " structure maps " that allow us to study the distributions of dust, star clusters, and emission-line gas in the circumnuclear regions (100-1000 pc scales) and in the associated host galaxy. Essentially all of these Seyfert galaxies have circumnuclear dust structures with morphologies ranging from grand-design two-armed spirals to chaotic dusty disks. In most Seyfert galaxies there is a clear physical connection between the nuclear dust spirals on hundreds of parsec scales and large-scale bars and spiral arms in the host galaxies proper. These connections are particularly striking in the interacting and barred galaxies. Such structures are predicted by numerical simulations of gas flows in barred and interacting galaxies and may be related to the fueling of active galactic nuclei by matter inflow from the host galaxy disks. We see no significant differences in the circumnuclear dust morphologies of Seyfert 1s and 2s, and very few Seyfert 2 nuclei are obscured by large-scale dust structures in the host galaxies. If Sevfert 2s are obscured Sevfert Is, then the obscuration must occur on smaller scales than those probed by HST.

  16. The ratio of molecular to atomic gas in spiral galaxies as a function of morphological type

    NASA Technical Reports Server (NTRS)

    Knezek, Patricia M.; Young, Judith S.

    1990-01-01

    In order to gain an understanding of the global processes which influence cloud and star formation in disk galaxies, it is necessary to determine the relative amounts of atomic, molecular, and ionized gas both as a function of position in galaxies and from galaxy to galaxy. With observations of the CO distributions in over 200 galaxies now completed as part of the Five College Radio Astronomy Observatory (FCRAO) Extragalactic CO Survey (Young et al. 1989), researchers are finally in a position to determine the type dependence of the molecular content of spiral galaxies, along with the ratio of molecular to atomic gas as a function of type. Do late type spirals really have more gas than early types when the molecular gas content is included. Researchers conclude that there is more than an order of magnitude decrease in the ratio of molecular to atomic gas mass as a function of morphological type from Sa-Sd; an average Sa galaxy has more molecular than atomic gas, and an average Sc has less. Therefore, the total interstellar gas mass to blue luminosity ratio, M sub gas/L sub B, increases by less than a factor of two as a function of type from Sa-Sd. The dominant effect found is that the phase of the gas in the cool interstellar medium (ISM) varies along the Hubble sequence. Researchers suggest that the more massive and centrally concentrated galaxies are able to achieve a molecular-dominated ISM through the collection of more gas in the potential. That gas may then form molecular clouds when a critical density is exceeded. The picture which these observations support is one in which the conversion of atomic gas to molecular gas is a global process which depends on large scale dynamics (cf Wyse 1986). Among interacting and merging systems, researchers find considerable scatter in the M(H2)/M(HI) ratio, with the mean ratio similar to that in the early type galaxies. The high global ratio of molecular to atomic gas could result from the removal of HI gas, the enhanced

  17. Two-dimensional maps of the infrared-to-radio ratio in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Marsh, Kenneth A.; Helou, George

    1994-01-01

    We have produced two-dimensional maps of the intensity ratio Q(sub 60) of 60 micron infrared to 20 cm radio continuum emission, for a set of 25 nearby galaxies, mostly spirals. The ratio maps were obtained from infrared images made using Infrared Astronomical Satellite (IRAS) data with the Maximum Correlation Method, and radio images made using VLA data. Before taking the ratio, the radio images were processed so as to have the same resolution properties as the infrared images; the final spatial resolution in all cases is approximately 1 min, corresponding to 1-2 kpc for most galaxies. These images allow us to study the variations for the Q(sub 60) ratio with unprecedented spatial resolution, and thus represents a major improvement over earlier work. Our new high-resolution maps confirm the slow decrease of Q(sub 60) with increasing radial distance from the nucleus, but show additional structure which is probably associated with separate sites of active star formation in the spiral arms. The maps show Q(sub 60) to be more closely related to infrared surface brightness than to the radial distance in the galaxy disk. We expect that the results will provide improved constraints on the evolution (diffusion, decay and escape) of cosmic-ray electrons in the magnetic field of the disks.

  18. The Structure of Nearby Nuclear Star Clusters in Late-Type Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Carson, Daniel; Barth, A. J.; Ho, L. C.; Greene, J. E.; Seth, A.; Cappellari, M.; Neumayer, N.

    2013-01-01

    Hubble Space Telescope imaging surveys have shown that most late-type, bulgeless spiral galaxies contain compact nuclear star clusters. To examine the structure and stellar content of these objects in detail, we have obtained HST WFC3 images of a sample of 10 spiral galaxies containing bright nuclear star clusters, most at distances of less than 5 Mpc. Each galaxy was observed in seven filters spanning the near-UV to near-IR. GALFIT was used to fit parametric models to the surface brightness distribution of each cluster. In most cases, a single Sersic model provides an adequate description of the cluster structure, although some clusters required 2 Sersic components, and one object (NGC 4395) requires an additional pointlike component to represent the active nucleus. This poster will present the measured cluster properties including magnitudes, Sersic indices, effective radii, and surface brightness profiles. The structural parameters measured from these HST images will be used as input to future dynamical models in order to determine cluster masses and to constrain the possible presence of intermediate-mass black holes within the clusters.

  19. THE INFLUENCE OF RED SPIRAL GALAXIES ON THE SHAPE OF THE LOCAL K-BAND LUMINOSITY FUNCTION

    SciTech Connect

    Bonne, Nicolas J.; Brown, Michael J. I.; Jones, Heath; Pimbblet, Kevin A.

    2015-02-01

    We have determined K-band luminosity functions for 13,325 local universe galaxies as a function of morphology and color (for K {sub tot} ≤ 10.75). Our sample is drawn from the Two Micron All Sky Survey Extended Source Catalog, with all sample galaxies having measured morphologies and distances (including 4219 archival redshift-independent distances). The luminosity function for our total sample is in good agreement with previous works, but is relatively smooth at faint magnitudes (due to bulk flow distance corrections). We investigated the differences due to morphological and color selection using 5417 sample galaxies with NASA Sloan Atlas optical colors and find that red spirals comprise 20%-50% of all spirals with –25 ≤ M{sub K}  < –20. Fainter than M{sub K} = –24, red spirals are as common as early types, explaining the different faint end slopes (α = –0.87 and –1.00 for red and early-types, respectively). While we find red spirals comprise more than 50% of all M{sub K}  < –25 spiral galaxies, they do not dominate the bright end of the overall red galaxy luminosity function, which is dominated by early-type galaxies. The brightest red spirals have ongoing star formation and those without are frequently misclassified as early-types. The faintest ones have an appearance and Sérsic indices consistent with faded disks, rather than true bulge-dominated galaxies.

  20. Corrugated velocity pattern in spiral galaxies: NGC 278, NGC 1058, NGC 2500 and UGC 3574

    NASA Astrophysics Data System (ADS)

    Sánchez Gil, M. C.; Alfaro, E. J.; Pérez, E.

    2011-11-01

    We report the detection in Hα emission of a radial corrugation pattern in the vertical velocity field of a sample of nearby face-on, spiral galaxies. We obtain long-slit spectra with the double arm ISIS spectrograph, attached to the 4.2 m William Herschel Telescope. The existence of corrugations has been already reported, e.g. Alfaro et al. (2001), Matthews & Uson (2008). Corrugations are closely link, as cause/effect, to the large scale star formation processes: density waves, tidal interactions, galactic bores, collisions of high velocity clouds with disk, etc. Which mechanism is the origin of disk corrugations is still an open problem. In this work not only the existence of radial and azimuthal corrugations are clearly observed, we report a first systematic study on the velocity corrugations in a sample of nearly face-on spiral galaxies. NGC 278 and NGC 1058 show a similar behavior to NGC 5427 (Alfaro et al. 2001), with a clear displacement between the velocities and emission line peaks. Where the approaching velocity peaks occur in the convex border of the arms, and the receding maxima are located behind the Hα emission maxima, in the concave side. This kinematical behavior is similar to the one expected in a galactic bore generated by the interaction of a spiral density wave with a thick gaseous disk. NGC 2500 and UGC 3574 do not show so clear this last relation between the velocity and emission line peaks, a possible cause should a fainter and discontinuous Hα emission. Oddly, these two pairs of galaxies also differ between them in their ionization mechanism features obtained from diagnostic diagrams.

  1. TWO-DIMENSIONAL KINEMATICS OF THE EDGE-ON SPIRAL GALAXY ESO 379-006

    SciTech Connect

    Rosado, M.; Gabbasov, R. F.; Repetto, P.; Martos, M.; Fuentes-Carrera, I.; Amram, P.; Hernandez, O.

    2013-05-15

    We present a kinematical study of the nearly edge-on galaxy ESO 379-006 that shows the existence of extraplanar ionized gas. With Fabry-Perot spectroscopy at H{alpha}, we study the kinematics of ESO 379-006 using velocity maps and position-velocity diagrams parallel to the major and to the minor axis of the galaxy. We build the rotation curve of the disk and discuss the role of projection effects due to the fact of viewing this galaxy nearly edge-on. The twisting of the isovelocities in the radial velocity field of the disk of ESO 379-006 as well as the kinematical asymmetries found in some position-velocity diagrams parallel to the minor axis of the galaxy suggest the existence of deviations to circular motions in the disk that can be modeled and explained with the inclusion of a radial inflow probably generated by a bar or by spiral arms. We succeeded in detecting extraplanar diffuse ionized gas in this galaxy. At the same time, from the analysis of position-velocity diagrams, we found some evidence that the extraplanar gas could lag in rotation velocity with respect to the midplane rotation.

  2. WFPC2 Imaging of the Multiphase Halos of Two Spiral Galaxies: Dust and Ionized Gas

    NASA Astrophysics Data System (ADS)

    Rueff, Katherine; Pitterle, M.; Hirschauer, A.; Lehner, N.; Howk, C.

    2006-12-01

    We present high-resolution optical images of the interstellar medium (ISM) in the thick disks of the spiral galaxies NGC 4013 and NGC 4302. Our broadband (BVI) images acquired with the Hubble Space Telescope’s WFPC2 show extensive extraplanar dust clouds seen in absorption against the background stellar light, while our narrow-band H-alpha images taken with the WIYN 3.5-m telescope show the diffuse ionized gas (DIG) in these galaxies. The dusty, thick disk clouds visible in our WFPC2 images, which can be found to heights approaching 2 kpc from the midplanes of these galaxies, trace a phase of the ISM that shows significant structure on quite small scales. In general this material is seen to be highly filamentary. By contrast, the thick disk DIG in these galaxies has significantly smoother distribution. We note several unresolved knots of H-alpha emission which may represent thick disk H II regions. We discuss the relationship of the dust-bearing clouds and the DIG in these galaxies.

  3. Spiral Arm Pitch Angle Measurements of Galaxies in Different Wavelengths of Light to Investigate a Prediction of Density Wave Theory

    NASA Astrophysics Data System (ADS)

    Pour Imani, Hamed; Davis, Benjamin L.; Shields, Douglas W.; Kennefick, Julia; Kennefick, Daniel

    2015-08-01

    Spiral structure in disk galaxies has been an important study of astronomy for decades. In understanding this structure one of the major parameters is the pitch angle of spiral arms. The density wave theory was proposed by C.Lin and F.Shu in the mid-1960s to explain the spiral arm structure of spiral galaxies [1]. A prediction of this theory is that the pitch angle of spiral arms for galaxies with blue-light wavelength images should be smaller than for infrared-light, so we have tighter spiral arms in blue band images. Young (blue) stars in arms of the galaxies move head of the old (red) stellar populations, clouds and dust. This implies that blue stars should exhibit tighter arms. In ref [2], E.M Garcia et al (2014) investigate the behavior of the pitch angle of spiral arms depending on optical wavelength. They worked on five galaxies and their images band-pass wavelength are in the optical range and their results show that just three of those five galaxies are consistent with density wave theory.In this research, we worked with a bigger samples and for each galaxy we used an optical wavelength image (B-Band: 445 nm) and another image from the Spitzer Space Telescope in a deep infrared range (Infrared: 8.0 μm) and we measured the pitch angle with the 2DFFT code [3]. Our results show that for optical range images we have smaller pitch angle compared to the infrared range and all of our measurements support with the density wave theory. Our results for 42 NGC galaxies show that spiral arms for images with optical range wavelength are clearly tighter typically by a few degrees than spiral arms in infrared range wavelength.Reference:[1]. Bertin, G. and Lin, C. (1996), MIT Press[2]. E.M Garcia et al, 2014 ApJ 793 L19[3]. Benjamin L. Davis et al. 2012 ApJS 199 33

  4. CATALOG OF OBSERVED TANGENTS TO THE SPIRAL ARMS IN THE MILKY WAY GALAXY

    SciTech Connect

    Vallée, Jacques P.

    2014-11-01

    From the Sun's location in the Galactic disk, one can use different arm tracers (CO, H I, thermal or ionized or relativistic electrons, masers, cold and hot dust, etc.) to locate a tangent to each spiral arm in the disk of the Milky Way. We present a master catalog of the astronomically observed tangents to the Galaxy's spiral arms, using different arm tracers from the literature. Some arm tracers can have slightly divergent results from several papers, so a mean value is taken—see the Appendix for CO, H II, and masers. The catalog of means currently consists of 63 mean tracer entries, spread over many arms (Carina, Crux-Centaurus, Norma, Perseus origin, near 3 kpc, Scutum, Sagittarius), stemming from 107 original arm tracer entries. Additionally, we updated and revised a previous statistical analysis of the angular offset and linear separation from the mid-arm for each different mean arm tracer. Given enough arm tracers, and summing and averaging over all four spiral arms, one could determine if arm tracers have separate and parallel lanes in the Milky Way. This statistical analysis allows a cross-cut of a Galactic spiral arm to be made, confirming a recent discovery of a linear separation between arm tracers. Here, from the mid-arm's CO to the inner edge's hot dust, the arm halfwidth is about 340 pc; doubling would yield a full arm width of 680 pc. We briefly compare these observations with the predictions of many spiral arm theories, notably the density wave theory.

  5. A Green Bank Telescope Search for Highly Extended HI Disks Around Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Ford, H. Alyson; Bregman, Joel

    2015-08-01

    Recent UV absorption line studies suggest that a large fraction of missing baryons are in the warm ionized and neutral phases, with about half of Milky Way-mass galaxies containing absorption systems with HI column densities of 10^18 cm^-2 or greater. This HI gas, which would have been difficult to detect with previous instruments, could have enough mass to account for the missing baryons. The Green Bank Telescope (GBT) presents a unique opportunity to detect this emission. We present GBT results from a sample of ten nearby optically luminous spirals in search of these extended disks of low column density HI.

  6. A Comparison of the Detailed Chemical Abundances of Globular Clusters in the Milky Way, Andromeda, and Centaurus A Galaxies

    NASA Astrophysics Data System (ADS)

    Colucci, Janet E.; Bernstein, Rebecca

    2016-01-01

    We present a homogeneous analysis of high resolution spectra of globular clusters in three massive galaxies: the Milky Way, M31, and NGC 5128. We measure detailed abundance ratios for alpha, light, Fe-peak, and neutron capture elements using our technique for analyzing the integrated light spectra of globular clusters. For many of the heavy elements we provide a first look at the detailed chemistry of old populations in an early type galaxy. We discuss similarities and differences between the galaxies and the potential implications for their star formation histories.

  7. HUBBLE SPIES GLOBULAR CLUSTER IN NEIGHBORING GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Hubble Space Telescope has captured a view of a globular cluster called G1, a large, bright ball of light in the center of the photograph consisting of at least 300,000 old stars. G1, also known as Mayall II, orbits the Andromeda galaxy (M31), the nearest major spiral galaxy to our Milky Way. Located 130,000 light-years from Andromeda's nucleus, G1 is the brightest globular cluster in the Local Group of galaxies. The Local Group consists of about 20 nearby galaxies, including the Milky Way. The crisp image is comparable to ground-based telescope views of similar clusters orbiting the Milky Way. The Andromeda cluster, however, is nearly 100 times farther away. A glimpse into the cluster's finer details allow astronomers to see its fainter helium-burning stars whose temperatures and brightnesses show that this cluster in Andromeda and the oldest Milky Way clusters have approximately the same age. These clusters probably were formed shortly after the beginning of the universe, providing astronomers with a record of the earliest era of galaxy formation. During the next two years, astronomers will use Hubble to study about 20 more globular clusters in Andromeda. The color picture was assembled from separate images taken in visible and near-infrared wavelengths taken in July of 1994. CREDIT: Michael Rich, Kenneth Mighell, and James D. Neill (Columbia University), and Wendy Freedman (Carnegie Observatories), and NASA Image files in GIF and JPEG format and captions may be accessed on Internet via anonymous ftp from oposite.stsci.edu in /pubinfo.

  8. Shape of the oxygen abundance profiles in CALIFA face-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Sánchez-Menguiano, L.; Sánchez, S. F.; Pérez, I.; García-Benito, R.; Husemann, B.; Mast, D.; Mendoza, A.; Ruiz-Lara, T.; Ascasibar, Y.; Bland-Hawthorn, J.; Cavichia, O.; Díaz, A. I.; Florido, E.; Galbany, L.; Gónzalez Delgado, R. M.; Kehrig, C.; Marino, R. A.; Márquez, I.; Masegosa, J.; Méndez-Abreu, J.; Mollá, M.; Del Olmo, A.; Pérez, E.; Sánchez-Blázquez, P.; Stanishev, V.; Walcher, C. J.; López-Sánchez, Á. R.; Califa Collaboration

    2016-03-01

    We measured the gas abundance profiles in a sample of 122 face-on spiral galaxies observed by the CALIFA survey and included all spaxels whose line emission was consistent with star formation. This type of analysis allowed us to improve the statistics with respect to previous studies, and to properly estimate the oxygen distribution across the entire disc to a distance of up to 3-4 disc effective radii (re). We confirm the results obtained from classical H ii region analysis. In addition to the general negative gradient, an outer flattening can be observed in the oxygen abundance radial profile. An inner drop is also found in some cases. There is a common abundance gradient between 0.5 and 2.0 re of αO / H = - 0.075 dex /re with a scatter of σ = 0.016 dex /re when normalising the distances to the disc effective radius. By performing a set of Kolmogorov-Smirnov tests, we determined that this slope is independent of other galaxy properties, such as morphology, absolute magnitude, and the presence or absence of bars. In particular, barred galaxies do not seem to display shallower gradients, as predicted by numerical simulations. Interestingly, we find that most of thegalaxies in the sample with reliable oxygen abundance values beyond ~2 effective radii (57 galaxies) present a flattening of the abundance gradient in these outer regions. This flattening is not associated with any morphological feature, which suggests that it is a common property of disc galaxies. Finally, we detect a drop or truncation of the abundance in the inner regions of 27 galaxies in the sample; this is only visible for the most massive galaxies.

  9. Hα kinematics of S4G spiral galaxies - III. Inner rotation curves

    NASA Astrophysics Data System (ADS)

    Erroz-Ferrer, Santiago; Knapen, Johan H.; Leaman, Ryan; Díaz-García, Simón; Salo, Heikki; Laurikainen, Eija; Querejeta, Miguel; Muñoz-Mateos, Juan Carlos; Athanassoula, E.; Bosma, Albert; Comerón, Sebastien; Elmegreen, Bruce G.; Martínez-Valpuesta, Inma

    2016-05-01

    We present a detailed study of the shape of the innermost part of the rotation curves of a sample of 29 nearby spiral galaxies, based on high angular and spectral resolution kinematic Hα Fabry-Perot observations. In particular, we quantify the steepness of the rotation curve by measuring its slope dRvc(0). We explore the relationship between the inner slope and several galaxy parameters, such as stellar mass, maximum rotational velocity, central surface brightness (μ0), bar strength and bulge-to-total ratio. Even with our limited dynamical range, we find a trend for low-mass galaxies to exhibit shallower rotation curve inner slopes than high-mass galaxies, whereas steep inner slopes are found exclusively in high-mass galaxies. This trend may arise from the relationship between the total stellar mass and the mass of the bulge, which are correlated among them. We find a correlation between the inner slope of the rotation curve and the morphological T-type, complementary to the scaling relation between dRvc(0) and μ0 previously reported in the literature. Although we find that the inner slope increases with the Fourier amplitude A2 and decreases with the bar torque Qb, this may arise from the presence of the bulge implicit in both A2 and Qb. As previously noted in the literature, the more compact the mass in the central parts of a galaxy (more concretely, the presence of a bulge), the steeper the inner slopes. We conclude that the baryonic matter dominates the dynamics in the central parts of our sample galaxies.

  10. Globular Clusters and Spur Clusters in NGC 4921, the Brightest Spiral Galaxy in the Coma Cluster

    NASA Astrophysics Data System (ADS)

    Lee, Myung Gyoon; Jang, In Sung

    2016-03-01

    We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in the Coma cluster. We also find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3 × 105 M⊙. The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions of the blue (metal-poor) GCs (0.70 < (V - I) ≤ 1.05) in the halo are estimated V(max) = 27.11 ± 0.09 mag and I(max) = 26.21 ± 0.11 mag. We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max) = 26.25 ± 0.03 mag. Adopting MI (max) = -8.56 ± 0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies to be 91 ± 4 Mpc. Combining this with the Coma radial velocity, we derive a value of the Hubble constant, H0 = 77.9 ± 3.6 km s-1 Mpc-1. We estimate the GC specific frequency of NGC 4921 to be SN = 1.29 ± 0.25, close to the values for early-type galaxies. This indicates that NGC 4921 is in the transition phase to S0s.

  11. VizieR Online Data Catalog: 1.49GHz Atlas of Spiral Galaxies (Condon, 1987)

    NASA Astrophysics Data System (ADS)

    Condon, J. J.

    2003-11-01

    The VLA has been used in its most compact D- and C/D-configurations to make low-resolution (θ~0.9FWHM) 1.49GHz maps of the spiral galaxies north of DE=-45° and brighter than BT=+12, the completeness limit of the Revised Shapley-Ames Catalog (Cat. VII/51). Most of these maps are confusion-limited at σ>=0.1mJy per beam, and at least 94% of the galaxies were detected with S>=1mJy. The maps have sufficient sensitivity to low-brightness emission that accurate radio "photometry" is possible. An atlas of contour maps, a table of total flux densities plus other radio source parameters, and references to published radio maps are given. (3 data files).

  12. Carbon abundances and radial gradients in NGC 300 and other nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Toribio San Cipriano, L.; García-Rojas, J.; Esteban, C.

    2015-05-01

    We present preliminary results of deep echelle spectrophotometry of a sample of HII regions along the disk of the Scd galaxy NGC 300 obtained with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the Very Large Telescope (VLT) with the aim of detect and measure very faint oii\\ and χ permitted lines. We focus this study on the C and O abundances obtained from faint optical recombination lines (ORLs) instead of the most commonly used collisionally excited lines (CELs). We have derived the ionic abundances of C^{2+} from the χ 4267Å RL and O^{2+} from the multiplet 1 of oii\\ around 4649Å in several objects. Finally, we have computed the radial gradients of C/H, O/H and C/O ratios in NGC 300 from RLs, which has allowed the comparison with similar data obtained by our group in other nearby spiral galaxies.

  13. Detailed Decomposition of Galaxy Images II: Fitting Spiral Arms, Bars, and Non-axisymmetric Structures in GALFIT 3.0

    NASA Astrophysics Data System (ADS)

    Peng, Chien Y.; Ho, L. C.; Impey, C. D.; Rix, H. W.

    2007-12-01

    The technique of fitting galaxy light profiles with analytic functions (e.g. de Vaucouleurs, exponential), also known as parametric fitting, has been a useful tool for studying galaxy structure and evolution. It is often used to quantify global properties of galaxies such as luminosity, size, ellipticity, and profile shape in a self-consistent manner. It also allows one to deblend multiple components of a galaxy, e.g. bulge/disk/bar/AGN, or to separate overlapping galaxies in a rigorous and robust way. However, the traditional method of fitting galaxies relies on using ellipsoid models, which is sometimes criticized to argue in favor of non-parametric techniques. In this study, we show that two dimensional image fitting is not fundamentally restricted to using axisymmetric ellipsoid shapes. By breaking from axisymmetry parametrically through the use of Fourier modes, one can better quantify the degree of galaxy irregularity in an intuitive and well-motivated manner. We also introduce a technique that allows one to fit spiral structures in late-type galaxies through the use of coordinate rotation. By comparing with more realistic models now possible, we find that the traditional use of simple ellipsoid models is robust even on irregular and spiral galaxies, because single component fits are by nature large scale averages. However, when it comes to quantifying sub-components of a galaxy, sometimes it is necessary to model structures in detail, such as when performing bulge-to-disk decomposition of galaxies with strong spiral arms, or quantifying the symmetry due to bright (e.g. bulge) and faint (e.g. disk) galaxy sub-components separately. These new techniques are implemented in GALFIT 3.0 (http://www.ociw.edu/ peng/work/galfit/galfit.html ). CYP gratefully acknowledges support from the Plaskett Fellowship (NRC-HIA) and the Institute/Giacconi Fellowship (STScI) programs.

  14. Identification of an Extensive Luminous Halo Around the Ringed Spiral Galaxy NGC 7217

    NASA Astrophysics Data System (ADS)

    Buta, R.; van Driel, W.; Braine, J.; Combes, F.

    1993-12-01

    The isolated spiral galaxy NGC 7217 is characterized by flocculent spiral structure and three optical ring-like zones: a stellar nuclear ring, a weak inner pseudoring, and a bright patchy outer ring. The rings all have nearly the same shape and position angle in projection. To understand this kind of ringed galaxy, we have obtained deep CCD BVRI surface photometry and mapping of the CO and HI gas distributions and kinematics. Our images reveal something that was missed in previous studies: a large, nearly round halo of light extending far beyond the outer ring. We interpret this as bulge light which comes back to dominate the luminosity distribution at large radii. Ellipse fits to isophotes out to 240('') radius reveal a minimum axis ratio of 0.83 just outside the outer ring at 90('') , and then a rise to 0.96 at about 140('') . The luminosity profiles are well-fitted by a combined r({1/) 4} bulge and exponential disk model. In all filters, the bulge dominates at all radii, and the bulge-to-total disk ratio is about 2.3 (B). If the minimum axis ratio of 0.83 approximates the apparent flattening of the disk, then NGC 7217 is remarkably axisymmetric. Nevertheless, the I-band image reveals a tightly-wrapped, two-armed spiral pattern in the outer ring region. The outer ring includes 4.5% of the total B luminosity and is the locus of most of the recent star formation in the galaxy; it is also where the HI gas is concentrated. An additional noteworthy feature is a circumnuclear dust ring 1.2 kpc in diameter. Other dust lanes are seen only on the near side of the galaxy. The rings of NGC 7217 could be resonances with a very weak internal perturbation. We are attempting to simulate the structure using the I-band light distribution to help define the potential. But most interesting is the recent discovery of a substantial population of counter-rotating stars in the galaxy (Kuijken 1993, PASP, 105, 1016). One possible explanation for these stars is that the bulge is more

  15. STAR FORMATION IN THE OUTER DISKS OF SPIRAL GALAXIES: ULTRAVIOLET AND H{alpha} PHOTOMETRY

    SciTech Connect

    Barnes, Kate L.; Van Zee, Liese; Skillman, Evan D. E-mail: vanzee@astro.indiana.edu

    2011-12-20

    We present an analysis of ultradeep UV and H{alpha} imaging of five nearby spiral galaxies to study the recent star formation in the outer disk. Using azimuthally averaged ellipse photometry as well as aperture photometry of individual young stellar complexes, we measure how star formation rates (SFRs) and UV and H{alpha} colors vary with radius. We detect azimuthally averaged UV flux to {approx}1.2-1.4 R{sub 25} in most galaxies; at the edge of the detected UV disk, the surface brightnesses are 28-29 mag arcsec{sup -2}, corresponding to SFR surface densities of {approx}3 Multiplication-Sign 10{sup -4} M{sub Sun} yr{sup -1} kpc{sup -2}. Additionally, we detect between 120 and 410 young stellar complexes per galaxy, with a significant number of detections out to {approx}1.5 R{sub 25}. We measure radial FUV-NUV profiles, and find that the dispersion in the UV colors of individual young stellar complexes increases with radius. We investigate how radial variations in the frequency of star formation episodes can create color gradients and increasing dispersion in the UV colors of star-forming regions, like those observed in our study. Specifically, we use recently published, high spatial and temporal resolution measurements of {Sigma}{sub SFR} throughout the disk of M33 to estimate the frequency of star formation episodes throughout the disk of a typical spiral galaxy. We use stellar synthesis models of these star formation histories (SFHs) to measure the variations in UV colors and find that we can replicate large dispersions in UV colors based on episodic SFHs.

  16. THE LUMINOSITY FUNCTION OF X-RAY SOURCES IN SPIRAL GALAXIES

    SciTech Connect

    Prestwich, A. H.; Primini, F.; McDowell, J. C.; Zezas, A.; Kilgard, R. E.

    2009-11-10

    X-ray sources in spiral galaxies can be approximately classified into bulge and disk populations. The bulge (or hard) sources have X-ray colors which are consistent with low-mass X-ray binaries (LMXBs) but the disk sources have softer colors suggesting a different type of source. In this paper, we further study the properties of hard and soft sources by constructing color-segregated X-ray luminosity functions (XLFs) for these two populations. Since the number of sources in any given galaxy is small, we co-added sources from a sample of nearby, face-on spiral galaxies observed by Chandra as a Large Project in Cycle 2. We use simulations to carefully correct the XLF for completeness. The composite hard source XLF is not consistent with a single-power-law fit. At luminosities L{sub x} > 3 x 10{sup 38} erg s{sup -1}, it is well fitted by a power law with a slope that is consistent with that found for sources in elliptical galaxies by Kim and Fabbiano. This supports the suggestion that the hard sources are dominated by LMXBs. In contrast, the high-luminosity XLF of soft sources has a slope similar to the 'universal' high-mass X-ray binary XLF. Some of these sources are stellar-mass black hole binaries accreting at high rates in a thermal/steep power-law state. The softest sources have inferred disk temperatures that are considerably lower than found in galactic black holes binaries. These sources are not well understood, but some may be super-soft ultra-luminous X-ray sources in a quiescent state as suggested by Soria and Ghosh.

  17. The LAMOST survey of background quasars in the vicinity of the Andromeda and Triangulum galaxies. II. Results from the commissioning observations and the pilot surveys

    SciTech Connect

    Huo, Zhi-Ying; Bai, Zhong-Rui; Chen, Jian-Jun; Chen, Xiao-Yan; Du, Bing; Jia, Lei; Lei, Ya-Juan; Liu, Xiao-Wei; Yuan, Hai-Bo; Xiang, Mao-Sheng; Huang, Yang; Zhang, Hui-Hua; Yan, Lin; Chu, Jia-Ru; Chu, Yao-Quan; Hu, Hong-Zhuan; Cui, Xiang-Qun; Hou, Yong-Hui; Hu, Zhong-Wen; Jiang, Fang-Hua; and others

    2013-06-01

    We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, also named the Guoshoujing Telescope, during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available Sloan Digital Sky Survey, Kitt Peak National Observatory 4 m telescope, Xuyi Schmidt Telescope Photometric Survey optical, and Wide-field Infrared Survey Explorer near-infrared photometric data. We present 509 new quasars discovered in a stripe of ∼135 deg{sup 2} from M31 to M33 along the Giant Stellar Stream in the 2011 pilot survey data sets, and also 17 new quasars discovered in an area of ∼100 deg{sup 2} that covers the central region and the southeastern halo of M31 in the 2010 commissioning data sets. These 526 new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to 3.2. They represent a significant increase of the number of identified quasars in the vicinity of M31 and M33. There are now 26, 62, and 139 known quasars in this region of the sky with i magnitudes brighter than 17.0, 17.5, and 18.0, respectively, of which 5, 20, and 75 are newly discovered. These bright quasars provide an invaluable collection with which to probe the kinematics and chemistry of the interstellar/intergalactic medium in the Local Group of galaxies. A total of 93 quasars are now known with locations within 2.°5 of M31, of which 73 are newly discovered. Tens of quasars are now known to be located behind the Giant Stellar Stream, and hundreds are behind the extended halo and its associated substructures of M31. The much enlarged sample of known quasars in the vicinity of M31 and M33 can potentially be utilized to construct a perfect astrometric reference frame to measure the minute proper motions (PMs) of M31 and M33, along with the PMs of substructures associated with the Local Group of galaxies. Those PMs are some of the most fundamental properties of the Local

  18. 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.

  19. Corrugated velocity patterns in the spiral galaxies: NGC 278, NGC 1058, NGC 2500 & UGC 3574

    NASA Astrophysics Data System (ADS)

    Sánchez-Gil, M. Carmen; Alfaro, Emilio J.; Pérez, Enrique

    2015-12-01

    We address the study of the H α vertical velocity field in a sample of four nearly face-on galaxies using long-slit spectroscopy taken with the Intermediate dispersion Spectrograph and Imaging System (ISIS), attached to the William Herschel Telescope (WHT) at the Roque de los Muchachos Observatory (Spain). The spatial structure of the velocity vertical component shows a radial corrugated pattern with spatial scales higher or within the order of 1 kpc. The gas is mainly ionized by high-energy photons: only in some locations of NGC 278 and NGC 1058 is there some evidence of ionization by low-velocity shocks, which, in the case of NGC 278, could be due to minor mergers. The behaviour of the gas in the neighbourhood of the spiral arms fits, in the majority of the observed cases, with that predicted by the so-called hydraulic bore mechanism, where a thick magnetized disc encounters a spiral density perturbation. The results obtained show that it is difficult to explain the H α large-scale velocity field without the presence of a magnetized, thick galactic disc. Larger samples and spatial covering of the galaxy discs are needed to provide further insight into this problem.

  20. PLANETARY NEBULAE IN FACE-ON SPIRAL GALAXIES. II. PLANETARY NEBULA SPECTROSCOPY

    SciTech Connect

    Herrmann, Kimberly A.; Ciardullo, Robin E-mail: rbc@astro.psu.ed

    2009-09-20

    As the second step in our investigation of the mass-to-light ratio of spiral disks, we present the results of a spectroscopic survey of planetary nebulae (PNe) in five nearby, low-inclination galaxies: IC 342, M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), and M101 (NGC 5457). Using 50 setups of the WIYN/Hydra and Blanco/Hydra spectrographs, and 25 observations with the Hobby-Eberly Telescope's Medium Resolution Spectrograph, we determine the radial velocities of 99, 102, 162, 127, and 48 PNe, respectively, to a precision better than 15 km s{sup -1}. Although the main purpose of this data set is to facilitate dynamical mass measurements throughout the inner and outer disks of large spiral galaxies, our spectroscopy has other uses as well. Here, we co-add these spectra to show that, to first order, the [O III] and Balmer line ratios of PNe vary little over the top {approx}1.5 mag of the PN luminosity function. The only obvious spectral change occurs with [N II], which increases in strength as one proceeds down the luminosity function. We also show that typical [O III]-bright planetaries have E(B - V) {approx} 0.2 of circumstellar extinction, and that this value is virtually independent of [O III] luminosity. We discuss the implications this has for understanding the population of PN progenitors.

  1. Radial metallicity gradients in spiral galaxies from H II regions and planetary nebulae: probing galactic chemical evolution

    NASA Astrophysics Data System (ADS)

    Stanghellini, Letizia

    2015-08-01

    Radial metallicity gradients, typically observed in spiral galaxies, are excellent constraints for chemical evolution models. The contemporary studies of the two stellar populations, whose progenitors have formed at different times, yield to the chemical and time constraining of the models. In this context, planetary nebula and HII region analysis proved to be ideal two-epochs test populations. We present an assortment of galaxies whose oxygen abundances have been determined both with weak- and strong-line methods, and whose radial metallicity gradients and their evolution in time have disclosed very interesting correlations with the galaxy characteristics. New results from our Gemini/GMOS observations, and a review of the best literature data, set the stage for a better understanding of spiral galaxy evolution.

  2. W.W. Morgan and the Discovery of the Spiral Arm Structure of our Galaxy

    NASA Astrophysics Data System (ADS)

    Sheehan, William

    2008-03-01

    William Wilson Morgan was one of the great astronomers of the twentieth century. He considered himself a morphologist, and was preoccupied throughout his career with matters of classification. Though, his early life was difficult, and his pursuit of astronomy as a career was opposed by his father, he took a position at Yerkes Observatory in 1926 and remained there for the rest of his working life. Thematically, his work was also a unified whole. Beginning with spectroscopic studies under Otto Struve at Yerkes Observatory, by the late 1930s he concentrated particularly on the young O and B stars. His work an stellar classification led to the Morgan-Keenan-Kellman [MKK] system of classification of stars, and later - as he grappled with the question of the intrinsic color and brightness of stars at great distances - to the Johnson-Morgan UBV system for measuring stellar colors. Eventually these concerns with classification and method led to his greatest single achievement - the recognition of the nearby spiral arms of our Galaxy by tracing the OB associations and HII regions that outline them. After years of intensive work on the problem of galactic structure, the discovery came in a blinding flash of Archimedean insight as he walked under the night sky between his office and his house in the autumn of 1951. His optical discovery of the spiral arms preceded the radio-mapping of the spiral arms by more than a year. Morgan suffered a nervous breakdown soon after he announced his discovery, however, and so was prevented from publishing a complete account of his work. As a result of that, and the announcement soon afterward of the first radio maps of the spiral arms, the uniqueness of his achievement was not fully appreciated at the time.

  3. Spiral Galaxies with a Larger Fraction of Dark Matter in the Region of 3-10 Mpc Around the Virgo and Fornax Clusters

    NASA Astrophysics Data System (ADS)

    Kogoshvili, N. G.; Borchkhadze, T. M.; Kalloghlian, A. T.

    2015-09-01

    This is a study of the dynamic characteristics of spiral galaxies with absolute magnitudes M ≥ -20m.6 at distances of 3 to 10 Mpc from the Virgo and Fornax clusters based on data from the Merged Catalog of Galaxies MERCG. The diameters of the galaxies are used to determine the radius RD corresponding to the region with the greatest concentration of dark matter. Based on the condition of centrifugal equilibrium, the dynamic parameters of the spiral galaxies with M ≥ -20m.6 are calculated and compared with the dynamic characteristics of spiral galaxies with M ≥ -20m.6. It is found that there are many fewer spiral galaxies with M ≥ -20m.6 and a larger fraction of dark matter in the regions surrounding these clusters, estimated at 12.7% in the vicinity of the Virgo cluster and 15.3% in the vicinity of the Fornax cluster.

  4. Dark matter and MOND dynamical models of the massive spiral galaxy NGC 2841

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    We study dynamical models of the massive spiral galaxy NGC 2841 using both the Newtonian models with Navarro-Frenk-White (NFW) and isothermal dark haloes, as well as various MOND (MOdified Newtonian Dynamics) models. We use the observations coming from several publicly available data bases: we use radio data, near-infrared photometry as well as spectroscopic observations. In our models, we find that both tested Newtonian dark matter approaches can successfully fit the observed rotational curve of NGC 2841. The three tested MOND models (standard, simple and, for the first time applied to another spiral galaxy than the Milky Way, Bekenstein's toy model) provide fits of the observed rotational curve with various degrees of success: the best result was obtained with the standard MOND model. For both approaches, Newtonian and MOND, the values of the mass-to-light ratios of the bulge are consistent with the predictions from the stellar population synthesis (SPS) based on the Salpeter initial mass function (IMF). Also, for Newtonian and simple and standard MOND models, the estimated stellar mass-to-light ratios of the disc agree with the predictions from the SPS models based on the Kroupa IMF, whereas the toy MOND model provides too low a value of the stellar mass-to-light ratio, incompatible with the predictions of the tested SPS models. In all our MOND models, we vary the distance to NGC 2841, and our best-fitting standard and toy models use the values higher than the Cepheid-based distance to the galaxy NGC 2841, and the best-fitting simple MOND model is based on the lower value of the distance. The best-fitting NFW model is inconsistent with the predictions of the Λ cold dark matter cosmology, because the inferred concentration index is too high for the established virial mass.

  5. Nearby Spiral Galaxy Globular Cluster Systems. II. Globular Cluster Metallicities in NGC 300

    NASA Astrophysics Data System (ADS)

    Nantais, Julie B.; Huchra, John P.; Barmby, Pauline; Olsen, Knut A. G.

    2010-03-01

    We present new metallicity estimates for globular cluster (GC) candidates in the Sd spiral NGC 300, one of the nearest spiral galaxies outside the Local Group. We have obtained optical spectroscopy for 44 Sculptor Group GC candidates with the Boller and Chivens (B&C) spectrograph on the Baade Telescope at Las Campanas Observatory. There are two GCs in NGC 253 and 12 objects in NGC 300 with globular-cluster-like spectral features, nine of which have radial velocities above 0 km s-1. The remaining three, due to their radial velocities being below the expected 95% confidence limit for velocities of NGC 300 halo objects, are flagged as possible foreground stars. The non-cluster-like candidates included 13 stars, 15 galaxies, and an H II region. One GC, four galaxies, two stars, and the H II region from our sample were identified in archival Hubble Space Telescope images. For the GCs, we measure spectral indices and estimate metallicities using an empirical calibration based on Milky Way GCs. The GCs of NGC 300 appear similar to those of the Milky Way. Excluding possible stars and including clusters from the literature, the GC system (GCS) has a velocity dispersion of 68 km s-1 and has no clear evidence of rotation. The mean metallicity for our full cluster sample plus one literature object is [Fe/H] = -0.94, lying above the relationship between mean GC metallicity and overall galaxy luminosity. Excluding the three low-velocity candidates, we obtain a mean [Fe/H] = -0.98, still higher than expected, raising the possibility of significant foreground star contamination even in this sample. Visual confirmation of genuine GCs using high-resolution space-based imagery could greatly reduce the potential problem of interlopers in small samples of GCSs in low-radial-velocity galaxies. Data for this project were obtained at the Baade 6.5 m telescope, Las Campanas Observatory, Chile. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint

  6. The Herschel exploitation of local galaxy Andromeda (HELGA) - V. Strengthening the case for substantial interstellar grain growth

    NASA Astrophysics Data System (ADS)

    Mattsson, L.; Gomez, H. L.; Andersen, A. C.; Smith, M. W. L.; De Looze, I.; Baes, M.; Viaene, S.; Gentile, G.; Fritz, J.; Spinoglio, L.

    2014-10-01

    In this paper, we consider the implications of the distributions of dust and metals in the disc of M31. We derive mean radial dust distributions using a dust map created from Herschel images of M31 sampling the entire far-infrared peak. Modified blackbodies are fit to approximately 4000 pixels with a varying, as well as a fixed, dust emissivity index (β). An overall metal distribution is also derived using data collected from the literature. We use a simple analytical model of the evolution of the dust in a galaxy with dust contributed by stellar sources and interstellar grain growth, and fit this model to the radial dust-to-metals distribution across the galaxy. Our analysis shows that the dust-to-gas gradient in M31 is steeper than the metallicity gradient, suggesting interstellar dust growth is (or has been) important in M31. We argue that M31 helps build a case for cosmic dust in galaxies being the result of substantial interstellar grain growth, while the net dust production from stars may be limited. We note, however, that the efficiency of dust production in stars, e.g. in supernovae ejecta and/or stellar atmospheres, and grain destruction in the interstellar medium may be degenerate in our simple model. We can conclude that interstellar grain growth by accretion is likely at least as important as stellar dust production channels in building the cosmic dust component in M31.

  7. UIT: Ultraviolet surface photometry of the spiral galaxy M74 (NGC 628)

    NASA Technical Reports Server (NTRS)

    Cornett, Robert H.; O'Connell, Robert W.; Greason, Michael R.; Offenberg, Joel D.; Angione, Ronald J.; Bohlin, Ralph C.; Cheng, K. P.; Roberts, Morton S.; Smith, Andrew M.; Smith, Eric P.

    1994-01-01

    Ultraviolet photometry, obtained from Ultraviolet Imaging Telescope (UIT) images at 1520 A (far-UV; magnitudes m(152)) and 2490 A (near-UV; magnitudes m(249)), of the spiral galaxy M74 (NGC 628) is compared with H-alpha, R, V, and B surface photometry and with models. M74's surface brightness profiles have a central peak with an exponential falloff; the exponential scale lengths of the profiles increase with decreasing wavelength for the broad-band images. The slope of the continuum-subtracted H-alpha profile is intermediate between those of far-UV and near-UV profiles, consistent with the related origins of H-alpha and UV emission in extreme Population I material. M74's color profiles all become bluer with increasing radius. The (m(152) - m(249)) color as measured by UIT averages near 0.0 (the color of an A0 star) over the central 20 sec radius and decreases from approximately -0.2 to approximately -0.4 from 20 sec to 200 sec. The spiral arms are the dominant component of the surface photometry colors; interarm regions are slightly redder. In the UV, M74's nuclear region resembles its disk/spiral arm material in colors and morphology, unlike galaxies such as M81. No UV 'bulge' is apparent. The m(152) - m(249) colors and models of M74's central region clearly demonstrate that there is no significant population of O or B stars present in the central 10 sec. M74's UV morphology and (m(152) - m(249)) color profiles are similar to those of M33, although M74 is approximately 0.5 mag redder. M81 has a smooth UV bulge which is much redder than the nuclear regions of M74 and M33. M74 is approximately 0.4 mag bluer than M81 in its outer disk, although M81 has bright UV sources only in spiral arms more than 5 kpc from its center. We investigate possible explanations for the color profiles of the galaxies and the differences among the galaxies: abundances; reddening due to internal dust; interplanetary magnetic field (IMF) variations, and the history of formation of the

  8. A spectral and photometric study of 102 star-forming regions in seven spiral galaxies

    NASA Astrophysics Data System (ADS)

    Gusev, A. S.; Sakhibov, F.; Piskunov, A. E.; Kharchenko, N. V.; Bruevich, V. V.; Ezhkova, O. V.; Guslyakova, S. A.; Lang, V.; Shimanovskaya, E. V.; Efremov, Y. N.

    2016-04-01

    We present a study of complexes of young massive star clusters (YMCs), embedded in extragalactic giant H II regions, based on the coupling of spectroscopic with photometric and spectrophotometric observations of about 100 star-forming regions in seven spiral galaxies (NGC 628, NGC 783, NGC 2336, NGC 6217, NGC 6946, NGC 7331, and NGC 7678). The complete observational data base has been observed and accumulated within the framework of our comprehensive study of extragalactic star-forming regions. This paper presents the last part of either unpublished or refreshed photometric and spectrophotometric observations of the galaxies NGC 6217, NGC 6946, NGC 7331, and NGC 7678. We derive extinctions, chemical abundances, continuum, and line emissions of ionized gas, ages, and masses for cluster complexes. We find the YMC complexes to have ages no greater than 10 Myr and masses between 104 M⊙ and 107 M⊙, and the extinctions AV vary between ˜0 and 3 mag, while the impact of the nebular emission on integrated broad-band photometry mainly is not greater than 40 per cent of the total flux and is comparable with accuracies of dereddened photometric quantities. We also find evidence of differential extinction of stellar and gas emissions in some clusters, which hinders the photometric determination of ages and masses in these cases. Finally, we show that young massive cluster complexes in the studied galaxies and open clusters in the Milky Way form a continuous sequence of luminosities/masses and colour/ages.

  9. The kinematics and spiral structure of the Galaxy from the neutral hydrogen

    NASA Astrophysics Data System (ADS)

    Petrovskaya, I. V.

    The kinematical and structural characteristics of the Galaxy are investigated using the whole 21-cm line profile of the neutral hydrogen emission. The concerted rotation curve and the spiral arms parameters are obtained. The Galaxy is found to have four armes with the pitch angle i = 14^circ in the region R >= 0.6R_0 and the gaseous ring when 0.4 < R / R_0 < 0.6. The Sun is between the arms. Comparing the rotation laws of the neutral and ionised gas subsystems we found the distance of the Sun to the Galactic centre R_0 = 7.5 plus or minus 1.0 kpk. The rotation velocity has a signature with the depression approximatedly 20 km/s near R = R_0. The velocity jump may be connected with giant vortices near corotation region. The parameters of the anticyclonic motion in that region are investigated. Our method of interpretation of the 21 cm profile gives the possibility to investigate z-dependance of the velocity field. To solve this problem for the inner region of the Galaxy (R

  10. The flaring Hi disk of the nearby spiral galaxy NGC 2683

    NASA Astrophysics Data System (ADS)

    Vollmer, B.; Nehlig, F.; Ibata, R.

    2016-02-01

    New deep VLA D array Hi observations of the highly inclined nearby spiral galaxy NGC 2683 are presented. Archival C array data were processed and added to the new observations. To investigate the 3D structure of the atomic gas disk, we made different 3D models for which we produced model Hi data cubes. The main ingredients of our best-fit model are (i) a thin disk inclined by 80°; (ii) a crude approximation of a spiral and/or bar structure by an elliptical surface density distribution of the gas disk; (iii) a slight warp in inclination between 10 kpc ≤ R ≤ 20 kpc (decreasing by 10°); (iv) an exponential flare that rises from 0.5 kpc at R = 9 kpc to 4 kpc at R = 15 kpc, stays constant until R = 22 kpc, and decreases its height for R> 22 kpc; and (v) a low surface-density gas ring with a vertical offset of 1.3 kpc. The slope of NGC 2683's flare is comparable, but somewhat steeper than those of other spiral galaxies. NGC 2683's maximum height of the flare is also comparable to those of other galaxies. On the other hand, a saturation of the flare is only observed in NGC 2683. Based on the comparison between the high resolution model and observations, we exclude the existence of an extended atomic gas halo around the optical and thin gas disk. Under the assumption of vertical hydrostatic equilibrium we derive the vertical velocity dispersion of the gas. The high turbulent velocity dispersion in the flare can be explained by energy injection by (i) supernovae; (ii) magneto-rotational instabilities; (iii) interstellar medium stirring by dark matter substructure; or (iv) external gas accretion. The existence of the complex large-scale warping and asymmetries favors external gas accretion as one of the major energy sources that drives turbulence in the outer gas disk. We propose a scenario where this external accretion leads to turbulent adiabatic compression that enhances the turbulent velocity dispersion and might quench star formation in the outer gas disk of NGC

  11. The spiral-compact galaxy pair AM 2208-251: Computer simulations versus observations

    NASA Technical Reports Server (NTRS)

    Klaric, Mario; Byrd, Gene G.

    1990-01-01

    The system AM2208-251 is a roughly edge-on spiral extending east-west with a smaller round compact E system about 60 arcsec east of the spiral nucleus along the major axis of the spiral. Bertola, Huchtmeier, and Zeilinger (1990) have presented optical spectroscopic as well as single dish 21 cm observations of this system. Their spectroscopic data show, via emission lines lambda lambda 3727-29A, a rising rotation curve near the nucleus. These spectroscopic observations may indicate a tidal interaction in the system. In order to learn more about such pairs, the authors simulated the interaction using the computer model developed by Miller (1976 a,b, 1978) and modified by the authors (Byrd 1986, 1987, 1988). To do the simulation they need an idea of the mutual orbits of the two galaxies. Their computer model is a two-dimensional polar N-body program. It consists of a self-gravitating disk of particles, within an inert axially symmetric stabilizing halo potential. The particles are distributed in a 24(radial) by 36(azimuthal) polar grid. Self consistent calculations can be done only within the grid area. The disk is modeled with a finite Mestel disk, where all the particles initially move in circular orbits with constant tangential velocities (Mestel 1963), resulting in a flat rotation curve. The gas particles in the spiral's disk, which make up 30 percent of its mass, collide in the following manner. The number of particles in each bin of the polar grid is counted every time step. If it is greater than a given critical density, all the particles in the bin collide, obtaining in the result the same velocities, equal to the average for the bin. This process produces clumps of gas particles-the star formation sites. The authors suppress the collision in the inner part of the disk (within the circle r = 6) to represent the hole seen in the gas in the nuclear bulge of spirals. They thus avoid spurious effects due to collisions in that region. They also varied the size of

  12. The spiral-compact galaxy pair AM 2208-251: Computer simulations versus observations

    NASA Astrophysics Data System (ADS)

    Klaric, Mario; Byrd, Gene G.

    1990-11-01

    The system AM2208-251 is a roughly edge-on spiral extending east-west with a smaller round compact E system about 60 arcsec east of the spiral nucleus along the major axis of the spiral. Bertola, Huchtmeier, and Zeilinger (1990) have presented optical spectroscopic as well as single dish 21 cm observations of this system. Their spectroscopic data show, via emission lines lambda lambda 3727-29A, a rising rotation curve near the nucleus. These spectroscopic observations may indicate a tidal interaction in the system. In order to learn more about such pairs, the authors simulated the interaction using the computer model developed by Miller (1976 a,b, 1978) and modified by the authors (Byrd 1986, 1987, 1988). To do the simulation they need an idea of the mutual orbits of the two galaxies. Their computer model is a two-dimensional polar N-body program. It consists of a self-gravitating disk of particles, within an inert axially symmetric stabilizing halo potential. The particles are distributed in a 24(radial) by 36(azimuthal) polar grid. Self consistent calculations can be done only within the grid area. The disk is modeled with a finite Mestel disk, where all the particles initially move in circular orbits with constant tangential velocities (Mestel 1963), resulting in a flat rotation curve. The gas particles in the spiral's disk, which make up 30 percent of its mass, collide in the following manner. The number of particles in each bin of the polar grid is counted every time step. If it is greater than a given critical density, all the particles in the bin collide, obtaining in the result the same velocities, equal to the average for the bin. This process produces clumps of gas particles-the star formation sites. The authors suppress the collision in the inner part of the disk (within the circle r = 6) to represent the hole seen in the gas in the nuclear bulge of spirals. They thus avoid spurious effects due to collisions in that region. They also varied the size of

  13. What Can GLAST Say About the Origin of Cosmic Rays in Other Galaxies

    SciTech Connect

    Bloom, Elliott

    2000-10-10

    Gamma rays in the band from 20 MeV to 300 GeV, used in combination with data from radio and X-ray bands, provide a powerful tool for studying the origin of cosmic rays in our sister galaxies Andromeda and the Magellanic Clouds. Gamma-ray Large Area Space Telescope (GLAST) will spatially resolve these galaxies and measure the spectrum and intensity of diffuse gamma radiation from the collisions of cosmic rays with gas and dust in them. Observations of Andromeda will give an external perspective on a spiral galaxy like the Milky Way. Observations of the Magellanic Clouds will permit a study of cosmic rays in dwarf irregular galaxies, where the confinement is certainly different and the massive star formation rate is much greater.

  14. Modelling nova populations in galaxies

    NASA Astrophysics Data System (ADS)

    Chen, Hai-Liang; Woods, T. E.; Yungelson, L. R.; Gilfanov, M.; Han, Zhanwen

    2016-05-01

    Theoretical modelling of the evolution of classical and recurrent novae plays an important role in studies of binary evolution, nucleosynthesis and accretion physics. However, from a theoretical perspective the observed statistical properties of novae remain poorly understood. In this paper, we have produced model populations of novae using a hybrid binary population synthesis approach for differing star formation histories (SFHs): a starburst case (elliptical-like galaxies), a constant star formation rate case (spiral-like galaxies) and a composite case (in line with the inferred SFH for M31). We found that the nova rate at 10 Gyr in an elliptical-like galaxy is ˜10-20 times smaller than a spiral-like galaxy with the same mass. The majority of novae in elliptical-like galaxies at the present epoch are characterized by low-mass white dwarfs (WDs), long decay times, relatively faint absolute magnitudes and long recurrence periods. In contrast, the majority of novae in spiral-like galaxies at 10 Gyr have massive WDs, short decay times, are relatively bright and have short recurrence periods. The mass-loss time distribution for novae in our M31-like galaxy is in agreement with observational data for Andromeda. However, it is possible that we underestimate the number of bright novae in our model. This may arise in part due to the present uncertainties in the appropriate bolometric correction for novae.

  15. Andromeda and the Seven Dwarfs

    NASA Astrophysics Data System (ADS)

    Brasseur, C.; Rix, H.-W.; Martin, N.

    2011-07-01

    With the new generation of wide-field surveys, our understanding of the Andromeda satellite system has dramatically improved in recent years. Since 2004, 12 new dwarf galaxies have been discovered around Andromeda, doubling the number of previously known companions. What are the properties of these newly discovered dwarfs and what do they tell us about galaxy formation? Are these systems bound? Do they show evidence of multiple star formation epochs? To better understand the stellar populations of the faintest dwarfs around M 31, we have used the Large Binocular Camera (LBT) and Suprime-Cam (Subaru) to obtain photometric observations of And X, And XVII, And XVIII, And XIX, And XX, And XXI and And XXII. Reaching below the horizontal branch, these observations have allowed for accurate distance determinations to be made, together with metallicity estimates based on the red giant branch stars. Our analysis shows our 7 dwarfs to be metal poor and with large spreads in [Fe/H], it strongly suggests multiple generations of stars are present in And X, And XVII, And XVIII, and And XIX, And XXI.

  16. Kinematics of the ionized gas around ultra-luminous X-ray sources in nearby spiral galaxies.

    NASA Astrophysics Data System (ADS)

    Fuentes-Carrera, Isaura L.; Sánchez Cruces, Mónica; Rosado, Margarita; Benitez-Benitez, Claudia; Salinas-Martínez, Alfredo; Aguilera, Verónica; Cruz-Reyes, Mariana

    2016-07-01

    We present scanning Fabry-Perot observations of the ionized gas surrounding ultra-luminous X-ray sources in four nearby spiral galaxies. We identify non-circular motions that may be associated with either isotropically or beamed expanding gas. Most of the sources observed show asymmetrical distribution of the ionized emission as well as asymmetrical distribution of gas motions. We also study the location of these sources in the context of the whole galaxy in different wavelengths. This work is part of an analysis to determine the nature of these sources and their correlation (if any) with the kinematics of host galaxy.

  17. The angular momentum of hot coronae around spiral galaxies and its impact on the evolution of star forming discs

    NASA Astrophysics Data System (ADS)

    Pezzulli, G.; Fraternali, F.; Binney, J.

    2016-06-01

    Galaxy formation theory and recent observations indicate that spiral galaxies are surrounded by massive and hot coronae, which potentially constitute a huge source of mass and angular momentum for the star forming discs embedded within them. Accretion from these reservoirs is likely a key ingredient for the evolution of spiral galaxies, but our understanding of the involved processes requires more observational and theoretical investigation, both at global and local scales. In this talk, I focus on some theoretical aspects of the angular momentum distribution of hot coronae. I address, in particular, whether these structures can sustain the inside-out growth of spiral galaxies and what are the dynamical consequences of the accretion of hot coronal gas onto the disc. These processes can have a big impact on observable quantities, most notably gas-phase abundance gradients, which can be used to put constraints on theory. I finally mention ongoing work to understand whether a cosmologically motivated angular momentum distribution for the hot gas is compatible with the constraints from galaxy evolution.

  18. GRAND DESIGN AND FLOCCULENT SPIRALS IN THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S{sup 4}G)

    SciTech Connect

    Elmegreen, Debra Meloy; Yau, Andrew; Elmegreen, Bruce G.; Athanassoula, E.; Bosma, Albert; Helou, George; Sheth, Kartik; Ho, Luis C.; Madore, Barry F.; Menendez-Delmestre, KarIn; Gadotti, Dimitri A.; Knapen, Johan H.; Laurikainen, Eija; Salo, Heikki; Meidt, Sharon E.; Regan, Michael W.; Zaritsky, Dennis; Aravena, Manuel

    2011-08-10

    Spiral arm properties of 46 galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S{sup 4}G) were measured at 3.6 {mu}m, where extinction is small and the old stars dominate. The sample includes flocculent, multiple arm, and grand design types with a wide range of Hubble and bar types. We find that most optically flocculent galaxies are also flocculent in the mid-IR because of star formation uncorrelated with stellar density waves, whereas multiple arm and grand design galaxies have underlying stellar waves. Arm-interarm contrasts increase from flocculent to multiple arm to grand design galaxies and with later Hubble types. Structure can be traced further out in the disk than in previous surveys. Some spirals peak at mid-radius while others continuously rise or fall, depending on Hubble and bar type. We find evidence for regular and symmetric modulations of the arm strength in NGC 4321. Bars tend to be long, high amplitude, and flat-profiled in early-type spirals, with arm contrasts that decrease with radius beyond the end of the bar, and they tend to be short, low amplitude, and exponential-profiled in late Hubble types, with arm contrasts that are constant or increase with radius. Longer bars tend to have larger amplitudes and stronger arms.

  19. The role of stellar mass-loss in dynamics of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Jungwiert, B.; Combes, F.; Palous, J.

    A new N-body sticky-particles computer code for spiral galaxies is presented. The substantial improvement over existing models, either sticky-particles or SPH, is the scheme for the bi-directional mass exchange between gas and stars: the consumption of the former by star formation is taken into account by locking a fraction of gas in newly created stars while the mass-loss from stars via stellar winds and supernova explosions is implemented as time dependent over the Hubble time. A comparison with models not including gas recycling or treating it as immediate shows important differences as to star formation rate, gas consumption time, and the rate at which gas is fuelled towards galactic centers, all having potentially deep consequences for galactic evolution.

  20. A SINFONI view of circum-nuclear star-forming rings in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Falcón-Barroso, Jesús; Böker, Torsten; Schinnerer, Eva; Knapen, Johan H.; Ryder, Stuart

    2008-07-01

    We present near-infrared (H- and K-band) SINFONI integral-field observations of the circumnuclear star formation rings in five nearby spiral galaxies. We made use of the relative intensities of different emission lines (i.e. [FeII], HeI, Brγ) to age date the stellar clusters present along the rings. This qualitative, yet robust, method allows us to discriminate between two distinct scenarios that describe how star formation progresses along the rings. Our findings favour a model where star formation is triggered predominantly at the intersection between the bar major axis and the inner Lindblad resonance and then passively evolves as the clusters rotate around the ring (‘Pearls on a string’ scenario), although models of stochastically distributed star formation (‘Popcorn’ model) cannot be completely ruled out.

  1. Spiral-like structure in the core of nearby galaxy clusters

    SciTech Connect

    Lagana, Tatiana F.; Andrade-Santos, Felipe; Lima Neto, Gastao B.

    2010-07-15

    Not surprisingly, with the very high angular resolution of the Chandra telescope, results revealed fairly complex structures in cluster cores to be more common than expected. In particular, understanding the nature of spiral-like features at the center of some clusters is the major motivation of this work. We present results from Chandra deep observations of 15 nearby galaxy clusters (0.01

  2. Spiral-like star-forming patterns in CALIFA early-type galaxies

    NASA Astrophysics Data System (ADS)

    Gomes, J. M.; Papaderos, P.; Vílchez, J. M.; Kehrig, C.; Iglesias-Páramo, J.; Breda, I.; Lehnert, M. D.; Sánchez, S. F.; Ziegler, B.; Dos Reis, S. N.; Bland-Hawthorn, J.; Galbany, L.; Bomans, D. J.; Rosales-Ortega, F. F.; Walcher, C. J.; García-Benito, R.; Márquez, I.; Del Olmo, A.; Mollá, M.; Marino, R. A.; Catalán-Torrecilla, C.; González Delgado, R. M.; López-Sánchez, Á. R.; Califa Collaboration

    2016-01-01

    Based on a combined analysis of SDSS imaging and CALIFA integral field spectroscopy data, we report on the detection of faint (24 <μr mag/□″< 26) star-forming spiral-arm-like features in the periphery of three nearby early-type galaxies (ETGs). These features are of considerable interest because they document the still ongoing inside-out growth of some local ETGs and may add valuable observational insight into the origin and evolution of spiral structure in triaxial stellar systems. A characteristic property of the nebular component in the studied ETGs, classified i+, is a two-radial-zone structure, with the inner zone that displays faint (EW(Hα) ≃ 1 Å) low-ionization nuclear emission-line region (LINER) properties, and the outer one (3 Å

  3. Disc colours in field and cluster spiral galaxies at 0.5 ≲z ≲ 0.8

    NASA Astrophysics Data System (ADS)

    Cantale, Nicolas; Jablonka, Pascale; Courbin, Frédéric; Rudnick, Gregory; Zaritsky, Dennis; Meylan, Georges; Desai, Vandana; De Lucia, Gabriella; Aragón-Salamanca, Alfonso; Poggianti, Bianca M.; Finn, Rose; Simard, Luc

    2016-04-01

    We present a detailed study of the colours of late-type galaxy discs for ten of the EDisCS galaxy clusters with 0.5 ≲ z ≲ 0.8. Our cluster sample contains 172 spiral galaxies, and our control sample is composed of 96 field disc galaxies. We deconvolved their ground-based V and I images obtained with FORS2 at the VLT with initial spatial resolutions between 0.4 and 0.8 arcsec to achieve a final resolution of 0.1 arcsec with 0.05 arcsec pixels, which is close to the resolution of the ACS at the HST. After removing the central region of each galaxy to avoid pollution by the bulges, we measured the V-I colours of the discs. We find that 50% of cluster spiral galaxies have disc V-I colours redder by more than 1σ of the mean colours of their field counterparts. This is well above the 16% expected for a normal distribution centred on the field disc properties. The prominence of galaxies with red discs depends neither on the mass of their parent cluster nor on the distance of the galaxies to the cluster cores. Passive spiral galaxies constitute 20% of our sample. These systems are not abnormally dusty. They are are made of old stars and are located on the cluster red sequences. Another 24% of our sample is composed of galaxies that are still active and star forming, but less so than galaxies with similar morphologies in the field. These galaxies are naturally located in the blue sequence of their parent cluster colour-magnitude diagrams. The reddest of the discs in clusters must have stopped forming stars more than ~5 Gyr ago. Some of them are found among infalling galaxies, suggesting preprocessing. Our results confirm that galaxies are able to continue forming stars for some significant period of time after being accreted into clusters, and suggest that star formation can decline on seemingly long (1 to 5 Gyr) timescales.

  4. Disc colours in field and cluster spiral galaxies at 0.5 ≲z ≲ 0.8

    NASA Astrophysics Data System (ADS)

    Cantale, Nicolas; Jablonka, Pascale; Courbin, Frédéric; Rudnick, Gregory; Zaritsky, Dennis; Meylan, Georges; Desai, Vandana; De Lucia, Gabriella; Aragón-Salamanca, Alfonso; Poggianti, Bianca M.; Finn, Rose; Simard, Luc

    2016-05-01

    We present a detailed study of the colours of late-type galaxy discs for ten of the EDisCS galaxy clusters with 0.5 ≲ z ≲ 0.8. Our cluster sample contains 172 spiral galaxies, and our control sample is composed of 96 field disc galaxies. We deconvolved their ground-based V and I images obtained with FORS2 at the VLT with initial spatial resolutions between 0.4 and 0.8 arcsec to achieve a final resolution of 0.1 arcsec with 0.05 arcsec pixels, which is close to the resolution of the ACS at the HST. After removing the central region of each galaxy to avoid pollution by the bulges, we measured the V-I colours of the discs. We find that 50% of cluster spiral galaxies have disc V-I colours redder by more than 1σ of the mean colours of their field counterparts. This is well above the 16% expected for a normal distribution centred on the field disc properties. The prominence of galaxies with red discs depends neither on the mass of their parent cluster nor on the distance of the galaxies to the cluster cores. Passive spiral galaxies constitute 20% of our sample. These systems are not abnormally dusty. They are are made of old stars and are located on the cluster red sequences. Another 24% of our sample is composed of galaxies that are still active and star forming, but less so than galaxies with similar morphologies in the field. These galaxies are naturally located in the blue sequence of their parent cluster colour-magnitude diagrams. The reddest of the discs in clusters must have stopped forming stars more than ~5 Gyr ago. Some of them are found among infalling galaxies, suggesting preprocessing. Our results confirm that galaxies are able to continue forming stars for some significant period of time after being accreted into clusters, and suggest that star formation can decline on seemingly long (1 to 5 Gyr) timescales.

  5. Giant Molecular Clouds and Star Formation in the Non-Grand Design Spiral Galaxy NGC 6946

    NASA Astrophysics Data System (ADS)

    Rebolledo, David; Wong, T.; Leroy, A.

    2012-01-01

    Although the internal physical properties of molecular clouds have been extensively studied (Solomon et al. 1987), a more detailed understanding of their origin and evolution in different types of galaxies is needed. In order to disentangle the details of this process, we performed CO(1-0) CARMA observations of the eastern part of the multi-armed galaxy NGC 6946. Although we found no evidence of an angular offset between molecular gas, atomic gas and star formation regions in our observations (Tamburro et al. 2008), we observe a clear radial progression from regions where molecular gas dominates over atomic gas (for r ≤ 2.8 kpc) to regions where the gas becomes mainly atomic (5.6 kpc ≤ r ≤ 7.6 kpc) when azimuthally averaged. In addition, we found that the densest concentrations of molecular gas are located on arms, particularly where they appear to intersect, which is in concordance with the predictions by simulations of the spiral galaxies with an active potential (Clarke & Gittins 2006; Dobbs & Bonnell 2008). At CO(1-0) resolution (140 pc), we were able to find CO emitting complexes with masses greater than those of typical Giant Molecular Clouds (105-106 M⊙). To identify GMCs individually and make a more detailed study of their physical properties, we made D array observations of CO(2-1) toward the densest concentrations of gas, achieving a resolution similar to GMCs sizes found in other galaxies (Bolatto et al. 2008). We present first results about differences in properties of the on-arm clouds and inter-arm clouds. We found that, in general, on-arm clouds present broader line widths, are more massive and more active in star formation than inter-arm clouds. We investigated if the velocity dispersion observed in CO(1-0) emitting complexes reflects velocity differences between unresolved smaller clouds, or if it corresponds to actual internal turbulence of the gas observed.

  6. The nature of the UV halo around the spiral galaxy NGC 3628

    NASA Astrophysics Data System (ADS)

    Baes, Maarten; Viaene, Sébastien

    2016-03-01

    Thanks to deep UV observations with GALEX and Swift, diffuse UV haloes have recently been discovered around galaxies. Based on UV-optical colours, it has been advocated that the UV haloes around spiral galaxies are due to UV radiation emitted from the disc and scattered off dust grains at high latitudes. Detailed UV radiative transfer models that take into account scattering and absorption can explain the morphology of the UV haloes, and they require the presence of an additional thick dust disc next the to traditional thin disc for half of the galaxies in their sample. We test whether such an additional thick dust disc agrees with the observed infrared emission in NGC 3628, an edge-on galaxy with a clear signature of a thick dust disc. We extend the far-ultraviolet radiative transfer models to full-scale panchromatic models. Our model, which contains no fine-tuning, can almost perfectly reproduce the observed spectral energy distribution from UV to mm wavelengths. These results corroborate the interpretation of the extended UV emission in NGC 3628 as scattering off dust grains, and hence of the presence of a substantial amount of diffuse extra-planar dust. A significant caveat, however, is the geometrical simplicity and non-uniqueness of our model: other models with a different geometrical setting could lead to a similar spectral energy distribution. More detailed radiative transfer simulations that compare the model results to images from UV to submm wavelengths are a way to break this degeneracy, as are UV polarisation measurements.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  8. Kinematical evidence for secular evolution in Spitzer Survey of Stellar Structure in Galaxies (S4G) spirals

    NASA Astrophysics Data System (ADS)

    Erroz-Ferrer, Santiago; Knapen, Johan H.; Font, Joan; Beckman, John E.

    2015-03-01

    We present a study of the kinematics of a sample of isolated spiral galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S4G). We use Hα Fabry-Perot data from the GHαFaS instrument at the William Herschel Telescope (WHT) in La Palma, complemented with images at 3.6 microns, in the R band and in the Hα filter. The resulting data cubes and velocity field maps allow a complete study of the kinematics of a galaxy, including in-depth investigations of the rotation curve, velocity moment maps, velocity residual maps, gradient maps and position-velocity (PV) diagrams. We find clear evidence of the secular evolution processes going on in these galaxies, such as asymmetries in the velocity field in the bar zone, and non-circular motions, probably in response to the potential of the structural components of the galaxies, or to past or present interactions.

  9. FORMATION OF LATE-TYPE SPIRAL GALAXIES: GAS RETURN FROM STELLAR POPULATIONS REGULATES DISK DESTRUCTION AND BULGE GROWTH

    SciTech Connect

    Martig, Marie; Bournaud, Frederic

    2010-05-10

    Spiral galaxies have most of their stellar mass in a large rotating disk, and only a modest fraction in a central spheroidal bulge. This challenges present models of galaxy formation: galaxies form at the center of dark matter halos through a combination of hierarchical merging and gas accretion along cold streams. Cosmological simulations thus predict that galaxies rapidly grow their bulge through mergers and instabilities and end up with most of their mass in the bulge and an angular momentum much below the observed level, except in dwarf galaxies. We propose that the continuous return of gas by stellar populations over cosmic times could help to solve this issue. A population of stars formed at a given instant typically returns half of its initial mass in the form of gas over 10 billion years, and the process is not dominated by supernovae explosions but by the long-term mass-loss from low- and intermediate-mass stars. Using simulations of galaxy formation, we show that this gas recycling can strongly affect the structural evolution of massive galaxies, potentially solving the bulge fraction issue, as the bulge-to-disk ratio of a massive galaxy can be divided by a factor of 3. The continuous recycling of baryons through star formation and stellar mass loss helps the growth of disks and their survival to interactions and mergers. Instead of forming only early-type, spheroid-dominated galaxies (S0 and ellipticals), the standard cosmological model can successfully account for massive late-type, disk-dominated spiral galaxies (Sb-Sc).

  10. The bolometric and UV attenuation in normal spiral galaxies of the Herschel Reference Survey

    NASA Astrophysics Data System (ADS)

    Viaene, S.; Baes, M.; Bendo, G.; Boquien, M.; Boselli, A.; Ciesla, L.; Cortese, L.; De Looze, I.; Eales, S.; Fritz, J.; Karczewski, O. Ł.; Madden, S.; Smith, M. W. L.; Spinoglio, L.

    2016-02-01

    The dust in nearby galaxies absorbs a fraction of the UV-optical-near-infrared radiation produced by stars. This energy is consequently re-emitted in the infrared. We investigate the portion of the stellar radiation absorbed by spiral galaxies from the Herschel Reference Survey (HRS) by modelling their UV-to-submillimetre spectral energy distributions. Our models provide an attenuated and intrinsic spectral energy distribution (SED), from which we find that on average 32% of all starlight is absorbed by dust. We define the UV heating fraction as the percentage of dust luminosity that comes from absorbed UV photons and find this to be 56%, on average. This percentage varies with morphological type, with later types having significantly higher UV heating fractions. We find a strong correlation between the UV heating fraction and specific star formation rate and provide a power-law fit. Our models allow us to revisit the IRX - AFUV relations, and derive these quantities directly within a self-consistent framework. We calibrate this relation for different bins of NUV - r colour and provide simple relations to relate these parameters. We investigated the robustness of our method and conclude that the derived parameters are reliable within the uncertainties that are inherent to the adopted SED model. This calls for a deeper investigation of how well extinction and attenuation can be determined through panchromatic SED modelling. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  11. BUILDING LATE-TYPE SPIRAL GALAXIES BY IN-SITU AND EX-SITU STAR FORMATION

    SciTech Connect

    Pillepich, Annalisa; Madau, Piero; Mayer, Lucio

    2015-02-01

    We analyze the formation and evolution of the stellar components in ''Eris'', a 120 pc resolution cosmological hydrodynamic simulation of a late-type spiral galaxy. The simulation includes the effects of a uniform UV background, a delayed-radiative-cooling scheme for supernova feedback, and a star formation recipe based on a high gas density threshold. It allows a detailed study of the relative contributions of ''in-situ'' (within the main host) and ''ex-situ'' (within satellite galaxies) star formation to each major Galactic component in a close Milky Way analog. We investigate these two star-formation channels as a function of galactocentric distance, along different lines of sight above and along the disk plane, and as a function of cosmic time. We find that: (1) approximately 70% of today's stars formed in-situ; (2) more than two thirds of the ex-situ stars formed within satellites after infall; (3) the majority of ex-situ stars are found today in the disk and in the bulge; (4) the stellar halo is dominated by ex-situ stars, whereas in-situ stars dominate the mass profile at distances ≲ 5 kpc from the center at high latitudes; and (5) approximately 25% of the inner, r ≲ 20 kpc, halo is composed of in-situ stars that have been displaced from their original birth sites during Eris' early assembly history.

  12. HOT X-RAY CORONAE AROUND MASSIVE SPIRAL GALAXIES: A UNIQUE PROBE OF STRUCTURE FORMATION MODELS

    SciTech Connect

    Bogdan, Akos; Forman, William R.; Vogelsberger, Mark; Sijacki, Debora; Mazzotta, Pasquale; Kraft, Ralph P.; Jones, Christine; David, Laurence P.; Bourdin, Herve; Gilfanov, Marat; Churazov, Eugene

    2013-08-01

    Luminous X-ray gas coronae in the dark matter halos of massive spiral galaxies are a fundamental prediction of structure formation models, yet only a few such coronae have been detected so far. In this paper, we study the hot X-ray coronae beyond the optical disks of two 'normal' massive spirals, NGC 1961 and NGC 6753. Based on XMM-Newton X-ray observations, hot gaseous emission is detected to {approx}60 kpc-well beyond their optical radii. The hot gas has a best-fit temperature of kT {approx} 0.6 keV and an abundance of {approx}0.1 Solar, and exhibits a fairly uniform distribution, suggesting that the quasi-static gas resides in hydrostatic equilibrium in the potential well of the galaxies. The bolometric luminosity of the gas in the (0.05-0.15)r{sub 200} region (r{sub 200} is the virial radius) is {approx}6 Multiplication-Sign 10{sup 40} erg s{sup -1} for both galaxies. The baryon mass fractions of NGC 1961 and NGC 6753 are f{sub b,NGC1961} {approx} 0.11 and f{sub b,NGC6753} {approx} 0.09, which values fall short of the cosmic baryon fraction. The hot coronae around NGC 1961 and NGC 6753 offer an excellent basis to probe structure formation simulations. To this end, the observations are confronted with the moving mesh code AREPO and the smoothed particle hydrodynamics code GADGET. Although neither model gives a perfect description, the observed luminosities, gas masses, and abundances favor the AREPO code. Moreover, the shape and the normalization of the observed density profiles are better reproduced by AREPO within {approx}0.5r{sub 200}. However, neither model incorporates efficient feedback from supermassive black holes or supernovae, which could alter the simulated properties of the X-ray coronae. With the further advance of numerical models, the present observations will be essential in constraining the feedback effects in structure formation simulations.

  13. Galaxy secular mass flow rate determination using the potential-density phase shift approach: Application to six nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaolei; Buta, Ronald J.

    2015-01-01

    Using the potential-density phase shift approach developed by the present authors in earlier publications, we estimate the magnitude of radial mass accretion/excretion rates across the disks of six nearby spiral galaxies (NGC 628, NGC 3351, NGC 3627, NGC 4321, NGC 4736, and NGC 5194) having a range of Hubble types. Our goal is to examine these rates in the context of bulge building and secular morphological evolution along the Hubble sequence. Stellar surface density maps of the sample galaxies are derived from SINGS 3.6 μm and SDSS i-band images using colors as an indicator of mass-to-light ratios. Corresponding molecular and atomic gas surface densities are derived from published CO (1-0) and HI interferometric observations of the BIMA SONG, THINGS, and VIVA surveys. The mass flow rate calculations utilize a volume-type torque integral to calculate the angular momentum exchange rate between the basic state disk matter and what we assume to be density wave modes in the observed galaxies. This volume-type integral contains the contributions from both the gravitational surface torque couple and the advective surface torque couple at the nonlinear, quasi-steady state of the wave modes, in sharp contrast to its behavior in the linear regime, where it contains only the contribution from the gravitational surface torque couple used by Lynden-Bell & Kalnajs in 1972. The potential-density phase shift approach yields angular momentum transport rates several times higher than those estimated using the Lynden-Bell and Kalnajs approach. And unlike Lynden-Bell and Kalnajs, whose approach predicts zero mass redistribution across the majority of the disk surface (apart from the isolated locations of wave-particle resonances) for quasi-steady waves, the current approach leads to predictions of significant mass redistribution induced by the quasi-steady density wave modes, enough for the morphological types of disks to evolve substantially within its lifetime. This difference

  14. The Andromeda Project: Final Results of Citizen Science Cluster Identification

    NASA Astrophysics Data System (ADS)

    Seth, Anil; Johnson, L. C.; Wallace, M.; Dalcanton, J.; Kapadia, A.; Lintott, C.; Simpson, R.; Skillman, E. D.; PHAT Team; Andromeda Project Team

    2014-01-01

    The Panchromatic Hubble Andromeda Treasury (PHAT) survey has completed data collection, having taken over 30 billion pixels of imaging data of the Andromeda galaxy over four years using the Hubble Space Telescope. These data contain the largest sample of star clusters observable in any galaxy, including our own Milky Way. The Andromeda Project is a citizen science project that recruited over 10,000 volunteers to identify thousands of star clusters in the PHAT imaging. We present results culminating from two rounds of cluster searching and the properties of the resulting sample. We discuss catalog completeness results derived from synthetic cluster data. This cluster sample represents a significant advance in our ability to study star and cluster formation on galaxy wide scales. We are using the resulting cluster sample to provide the best available constraints on the high-mass initial mass function and the fraction of star formation that results in bound star clusters.

  15. Recent Results from the SPLASH Survey: Chemical Abundances and Kinematics of Andromeda's Stellar Halo

    NASA Astrophysics Data System (ADS)

    Gilbert, Karoline

    2015-08-01

    Large scale surveys of Andromeda's resolved stellar populations have revolutionized our view of this galaxy over the past decade. The combination of large-scale, contiguous photometric surveys and pointed spectroscopic surveys has been particularly powerful for discovering and following up new substructures and disentangling the structural components of Andromeda. The SPLASH (Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo) survey consists of broad- and narrow-band imaging and spectroscopy of red giant branch stars in lines of sight throughout the M31 system, ranging in distance from 3 kpc to more than 200 kpc from Andromeda's center. I will present recent results from the SPLASH survey on the structure of Andromeda's stellar halo and the origin of tidal debris features, including measurements of the kinematics and chemical abundances of Andromeda's halo stars.

  16. Constraining Dark Matter Halo Profiles and Galaxy Formation Models Using Spiral Arm Morphology. II. Dark and Stellar Mass Concentrations for 13 Nearby Face-on Galaxies

    NASA Astrophysics Data System (ADS)

    Seigar, Marc S.; Davis, Benjamin L.; Berrier, Joel; Kennefick, Daniel

    2014-11-01

    We investigate the use of spiral arm pitch angles as a probe of disk galaxy mass profiles. We confirm our previous result that spiral arm pitch angles (P) are well correlated with the rate of shear (S) in disk galaxy rotation curves. We use this correlation to argue that imaging data alone can provide a powerful probe of galactic mass distributions out to large look-back times. We then use a sample of 13 galaxies, with Spitzer 3.6 μm imaging data and observed Hα rotation curves, to demonstrate how an inferred shear rate coupled with a bulge-disk decomposition model and a Tully-Fisher-derived velocity normalization can be used to place constraints on a galaxy's baryon fraction and dark matter halo profile. Finally, we show that there appears to be a trend (albeit a weak correlation) between spiral arm pitch angle and halo concentration. We discuss implications for the suggested link between supermassive black hole (SMBH) mass and dark halo concentration, using pitch angle as a proxy for SMBH mass.

  17. Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. II. Dark and stellar mass concentrations for 13 nearby face-on galaxies

    SciTech Connect

    Seigar, Marc S.; Davis, Benjamin L.; Berrier, Joel; Kennefick, Daniel

    2014-11-01

    We investigate the use of spiral arm pitch angles as a probe of disk galaxy mass profiles. We confirm our previous result that spiral arm pitch angles (P) are well correlated with the rate of shear (S) in disk galaxy rotation curves. We use this correlation to argue that imaging data alone can provide a powerful probe of galactic mass distributions out to large look-back times. We then use a sample of 13 galaxies, with Spitzer 3.6 μm imaging data and observed Hα rotation curves, to demonstrate how an inferred shear rate coupled with a bulge-disk decomposition model and a Tully-Fisher-derived velocity normalization can be used to place constraints on a galaxy's baryon fraction and dark matter halo profile. Finally, we show that there appears to be a trend (albeit a weak correlation) between spiral arm pitch angle and halo concentration. We discuss implications for the suggested link between supermassive black hole (SMBH) mass and dark halo concentration, using pitch angle as a proxy for SMBH mass.

  18. Galaxy interactions and star formation: Results of a survey of global H-alpha emission in spiral galaxies in 8 clusters

    NASA Technical Reports Server (NTRS)

    Moss, C.

    1990-01-01

    Kennicutt and Kent (1983) have shown that the global H alpha emission from a spiral galaxy is an indicator of the formation rate of massive stars. Moss, Whittle and Irwin (1988) have surveyed two clusters (Abell 347 and 1367) for galaxies with H alpha emission using a high dispersion objective prism technique. The purpose of the survey is to investigate environmental effects on star formation in spiral galaxies, and in particular to ascertain whether star formation is enhanced in cluster spirals. Approximately 20 percent of CGCG galaxies were detected in emission. Two plates of excellent quality were obtained for each of the two clusters, and galaxies were only identified to have emission if this was detected on both plates of a plate pair. In this way, plate flaws and other spurious identifications of emission could be rejected, and weak emission confirmed. The results of this survey have been discussed by Moss (1987). The detected galaxies are of types SO-a and later. The frequency with which galaxies are detected in emission increases towards later morphological type as expected (cf. Kennicutt and Kent 1983). There is no evidence of any dependence of the frequency of detected emission on the absolute magnitude of the galaxy (cf. Moss and Whittle 1990), but there is a strong correlation between a disturbed morphological appearance of the galaxy and the detection of emission. Furthermore it is found that the emission is more centrally concentrated in those galaxies which show a disturbed morphology. It may be noted that the objective prism plate gives a spectrum of a 400 A region around rest wavelength H alpha, but superposed on this is the H alpha emission from the galaxy which, because the light is essentially monochromatic, results in a true two-dimensional image of the H alpha distribution. The visual appearance of the emission on the prism plates was classified according to its diffuseness on a 5 point scale (very diffuse, diffuse, intermediate, compact, and

  19. Featured Image: Reddened Stars Reveal Andromeda's Dust

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-12-01

    As distant light travels on a path toward us, it can be absorbed by intervening, interstellar dust. Much work has been done to understand this dust extinction in the Milky Way, providing us with detailed information about the properties of the dust in our galaxy. Far less, however, is known about the dust extinction of other galaxies. The image above, taken with the ultraviolet space telescope GALEX, identifies the locations of four stars in the nearby Andromeda galaxy (click for a full view!) that are reddened due to extinction of their light by dust within Andromeda. In a recent study led by Geoffrey Clayton (Louisiana State University), new, high-signal-to-noise spectra were obtained for these four stars using Hubbles Space Telescope Imaging Spectrograph. These observations have allowed the authors to construct dust extinction curves to carefully study the nature of Andromedas interstellar dust. To learn about the results, see the paper below.CitationGeoffrey C. Clayton et al 2015 ApJ 815 14. doi:10.1088/0004-637X/815/1/14

  20. A SURVEY OF DIFFUSE INTERSTELLAR BANDS IN THE ANDROMEDA GALAXY: OPTICAL SPECTROSCOPY OF M31 OB STARS

    SciTech Connect

    Cordiner, Martin A.; Cox, Nick L. J.; Evans, Christopher J.; Trundle, Carrie; Smith, Keith T.; Sarre, Peter J.; Gordon, Karl D.

    2011-01-01

    We present the largest sample to date of intermediate-resolution blue-to-red optical spectra of B-type supergiants in M31 and undertake the first survey of diffuse interstellar bands (DIBs) in this galaxy. Spectral classifications, radial velocities, and interstellar reddenings are presented for 34 stars in three regions of M31. Based on a subset of these stars with foreground-corrected reddening E{sup M31}{sub B-V}{>=} 0.05, the strengths of the M31 DIBs are analyzed with respect to the amount of dust, ultraviolet radiation field strength, and polycyclic aromatic hydrocarbon emission flux. Radial velocities and equivalent widths are given for the {lambda}5780 and {lambda}6283 DIBs toward 11 stars. Equivalent widths are also presented for the following DIBs detected in three sightlines in M31: {lambda}{lambda}4428, 5705, 5780, 5797, 6203, 6269, 6283, 6379, 6613, 6660, and 6993. All of these M31 DIB carriers reside in clouds at radial velocities matching those of interstellar Na I and/or H I. The relationships between DIB equivalent widths and reddening (E{sup M31}{sub B-V}) are consistent with those observed in the local interstellar medium (ISM) of the Milky Way (MW). Many of the observed sightlines show DIB strengths (per unit reddening) which lie at the upper end of the range of Galactic values. DIB strengths per unit reddening are found (with 68% confidence) to correlate with the interstellar UV radiation field strength. The strongest DIBs are observed where the interstellar UV flux is lowest. The mean Spitzer 8/24 {mu}m emission ratio in our three fields is slightly lower than that measured in the MW, but we identify no correlation between this ratio and the DIB strengths in M31. Interstellar oxygen abundances derived from the spectra of three M31 H II regions in one of the fields indicate that the average metallicity of the ISM in that region is 12 + log [O/H] = 8.54 {+-} 0.18, which is approximately equal to the value in the solar neighborhood.

  1. Erratum: Precision Velocity Fields in Spiral Galaxies. I. Noncircular Motions and rms Noise in Disks

    NASA Astrophysics Data System (ADS)

    Beauvais, Charles; Bothun, G.

    2000-05-01

    In the paper ``Precision Velocity Fields in Spiral Galaxies. I. Noncircular Motions and rms Noise in Disks'' by Charles Beauvais and G. Bothun (ApJS, 125, 99) the abstract was incorrect. The corrected abstract is as follows: Imaging Fabry-Perot data have been acquired for a sample of spiral galaxies from which two-dimensional velocity fields have been constructed on a subkiloparsec resolution scale. These velocity fields are then examined for evidence of noncircular motions. Individual spectra are extracted and the resultant line profiles are fitted with Voigt, Gaussian, and Lorentzian functions. Gaussians are shown to provide a better model for simultaneously fitting a large number of line profiles, successfully fitting a higher fraction. The kinematic disk (i.e., tilted ring) modeling procedure is studied in detail and is shown to accurately recover the underlying rotational structure of galactic disks. The process of obtaining rotation curves from full two-dimensional velocity data is examined. Small-scale ``bumps and wiggles'' on the rotation curves are shown to be due to the inclusion of noncircular motions. Use of the rotation curve estimate returned by the modeling procedure rather than deprojection of the velocity field is recommended to avoid their inclusion. Investigation of the symmetry of the major- and minor-axis rotation curves reveal strong evidence of nonconcentric gas orbits with the maximum center shift of ~300 pc. Comparisons between kinematic and photometric structure (e.g., position angles, inclinations, centers) show considerable noise on small scales. Although large-scale averages are in agreement, this noise is a matter of some concern in the application of the Tully-Fisher method to disk galaxies. Moreover, cases of significant misalignment in position angle between the inner and outer disks are seen in two of the sample galaxies and may indicate the transition between luminous and dark-matter-dominated regions (i.e., where the maximum disk

  2. Near-infrared photometry of isolated spirals with and without an AGN --- II. Photometric properties of the host galaxies

    NASA Astrophysics Data System (ADS)

    Márquez, I.; Durret, F.; Masegosa, J.; Moles, M.; González Delgado, R. M.; Marrero, I.; Maza, J.; Pérez, E.; Roth, M.

    2000-08-01

    We present here the analysis of morphological and photometric properties of a sample of isolated spirals with (18) and without (11) an active nucleus, based on near-infrared imaging in the J and K' bands (Paper I). The aim of that comparative analysis is to find the differential properties that could be directly connected with the phenomenon of nuclear activity. We stress the importance of using isolated objects for that purpose. Our study shows that both sets of galaxies are similar in their global properties: they define the same Kormendy relation, their disk components share the same properties, the bulge and disk scale lengths are correlated in a similar way, bar strengths and lengths are similar for primary bars. Our results therefore indicate that hosts of isolated Seyfert galaxies have bulge and disk properties comparable to those of isolated non active spirals. Central colors (the innermost 200 pc) of active galaxies are redder than the centers of non active spirals, most probably due to AGN light being re-emitted by the hot dust and/or due to circumnuclear star formation, through the contribution of giants/supergiants. Central to our analysis is the study of the possible connection between bars and similar non axisymmetric structures with the nuclear fuelling. We note that only one of the Seyfert galaxies in our sample, namely ESO 139-12, does not present a primary bar. But bars are equally present in active and control objects. The same applies to secondary bars. Not all the active galaxies we have observed have them, and some control galaxies also present such central structures. Secondary central elongations (associated with secondary bars, lenses, rings or disks) may be somewhat different, but this result should be confirmed with larger samples. We note that numerical models indicate that such secondary bars are not strictly necessary to feed the central engine when a primary bar is present. Our results show that down to scales of 100-300 pc, there are

  3. The ALMA and HST Views of the Molecular Gas and Star Formation in the Prototypical Barred Spiral Galaxy NGC 1097

    NASA Astrophysics Data System (ADS)

    Sheth, Kartik; Regan, Michael W.; Kim, Taehyun; Kohno, Kotaro; Martin, Sergio; Villard, Eric; Onishi, Kyoko

    2016-01-01

    We mapped the entire inner disk of NGC 1097 (the circumnuclear ring, bar ends, the bar and inner spiral arms) using ALMA in the CO J=1-0 line at resolution of 1" (~65 pc). We also mapped the northern half of the bar in every other common molecular gas tracer at 3mm (HCN, HCO+, C18O, 13CO, C34S). Together these data provide the most detailed and highest resolution map of the molecular gas distribution and kinematics in a nearby barred spiral, rivalling the incredible maps seen for galaxies like M51 in the northern hemisphere. The data show the impact of the different environments in the galaxy as well as evidence for a multi-phased molecular medium. The data also evidence how the shear induced by the bar shock completely inhibits the star formation activity in the inner ends of the bar (clearly showing an anti-correlation between the strength of the CO line emission and Halpha emission). We will also present multiwavelength HST observations of the galaxy which are used to identify and map star clusters across the inner disk of the galaxy. We use these data to understand how star formation proceeds from one environment to the next across the galaxy.

  4. Spiral-induced velocity and metallicity patterns in a cosmological zoom simulation of a Milky Way-sized galaxy

    NASA Astrophysics Data System (ADS)

    Grand, Robert J. J.; Springel, Volker; Kawata, Daisuke; Minchev, Ivan; Sánchez-Blázquez, Patricia; Gómez, Facundo A.; Marinacci, Federico; Pakmor, Rüdiger; Campbell, David J. R.

    2016-07-01

    We use a high-resolution cosmological zoom simulation of a Milky Way-sized halo to study the observable features in velocity and metallicity space associated with the dynamical influence of spiral arms. For the first time, we demonstrate that spiral arms, that form in a disc in a fully cosmological environment with realistic galaxy formation physics, drive large-scale systematic streaming motions. In particular, on the trailing edge of the spiral arms the peculiar galactocentric radial and azimuthal velocity field is directed radially outward and azimuthally backward, whereas it is radially inward and azimuthally forward on the leading edge. Owing to the negative radial metallicity gradient, this systematic motion drives, at a given radius, an azimuthal variation in the residual metallicity that is characterized by a metal-rich trailing edge and a metal-poor leading edge. We show that these signatures are theoretically observable in external galaxies with integral field unit instruments such as VLT/MUSE, and if detected, would provide evidence for large-scale systematic radial migration driven by spiral arms.

  5. Star-forming complexes and the spiral structure of our Galaxy

    NASA Astrophysics Data System (ADS)

    Russeil, D.

    2003-01-01

    We have carried out a multiwavelength study of the plane of our Galaxy in order to establish a star-forming-complex catalogue which is as complete as possible. Features observed include Hα , H109alpha , CO, the radio continuum and absorption lines. For each complex we have determined the position, the systemic velocity, the kinematic distance and, when possible, the stellar distance and the corresponding uncertainties. All of these parameters were determined as homogeneously as possible, in particular all the stellar distances have been (re)calculated with the same calibration and the kinematic distances with the same mean Galactic rotation curve. Through the complexes with stellar distance determination, a rotation curve has been fitted. It is in good agreement with the one of Brand & Blitz (1993). We also investigated the residual velocities relative to the circular rotation model. We find that departures exist over large areas of the arms, with different values from one arm to another. From our data and in good agreement with previous studies, the Galactic warp is observed. It does not seem correlated with the departures from circular rotation. Finally, as segment-like features are noted from the complexes' distribution, we tried to find if they are indicative of a larger underlying structure. Then, we attempted to interpret the complexes' distribution in terms of spiral structure by fitting models with two, three and four logarithmic spiral arms. The four-arm model seems more appropriate to represent the grand design of our Galaxy. In this model the Norma arm and the external arm appear as being the two extremities of a single arm called the Norma-Cygnus arm. The new data and fitted model confirm the four-segment model of Georgelin & Georgelin (1976), clarifying the arms' design and extension and doubling their known length. Based on observations collected at the European Southern Observatory. Tables 1 and 3 (table1.ps and table3.txt) are available in

  6. High resolution infrared astronomy satellite observations of a selected spiral galaxy

    NASA Technical Reports Server (NTRS)

    Kulkarni, S. R.

    1991-01-01

    The H I, infrared, CO, H alpha and H beta band observations of M51, the prototypical grand-design spiral galaxy, are used to study the consequences of star formation for the distribution of H I and dust. Using the new Very Large Array (VLA) map of 21 cm emission, the Owens Valley Radio Observatory CO mosaic map, and an H alpha imate, new tests were performed with the idea of Tilanus and Allen that the H I is largely a photodissociation product in star-forming regions. It is confirmed that the H I spiral arms are generally coincident with the H II region arms, and offset downstream from the CO arms. The radial distributions of total gas, H alpha and H I surface density have a simple explanation in the dissociation picture. The distributions also demonstrate how the surface density of H I might be related to the star formation efficiency in molecule-rich galaxies. The large width of the H I regions along the arms compared to that of the giant H II regions can be understood in terms of a simple calculation of the expected size of an H I region associated with a typical giant H II region. The longer lifetime of the stars producing dissociating radiation vs. those producing ionizing radiation and the relatively long molecular formation timescale will also contribute to the greater width of the H I arms if stars are continuously forming on the arms. The lack of detailed coincidence of the H I and H II regions along the inner arms has a variety of possible explanations. Two simple tests were performed to probe the origins of the IRAS emission in M51. First, it was found that the infrared excess (IFE) of M51 is 24, suggesting that a substantial fraction of the infrared emission arises from dust heated by photons which do not originate in massive star-formaing regions. Second, radial cuts through the IRAS bands show that at 12, 25, and 60 microns, the arm-interarm contrast of the IRAS emission is substantially less than that of the H alpha emission, providing further

  7. 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.

  8. GMC evolution in a barred spiral galaxy with star formation and thermal feedback

    NASA Astrophysics Data System (ADS)

    Fujimoto, Yusuke; Bryan, Greg L.; Tasker, Elizabeth J.; Habe, Asao; Simpson, Christine M.

    2016-09-01

    We explore the impact of star formation and thermal stellar feedback on the giant molecular cloud population forming in a M83-type barred spiral galaxy. We compare three high-resolution simulations (1.5 pc cell size) with different star formation/feedback models: one with no star formation, one with star formation but no feedback, and one with star formation and thermal energy injection. We analyse the resulting population of clouds, finding that we can identify the same population of massive, virialized clouds and transient, low-surface density clouds found in our previous work (that did not include star formation or feedback). Star formation and feedback can affect the mix of clouds we identify. In particular, star formation alone simply converts dense cloud gas into stars with only a small change to the cloud populations, principally resulting in a slight decrease in the transient population. Feedback, however, has a stronger impact: while it is not generally sufficient to entirely destroy the clouds, it does eject gas out of them, increasing the gas density in the intercloud region. This decreases the number of massive clouds, but substantially increases the transient cloud population. We also find that feedback tends to drive a net radial inflow of massive clouds, leading to an increase in the star formation rate in the bar region. We examine a number of possible reasons for this and conclude that it is possible that the drag force from the enhanced intercloud density could be responsible.

  9. Phase transition between atomic and molecular hydrogen in nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Tanaka, Ayako; Nakanishi, Hiroyuki; Kuno, Nario; Hirota, Akihiko

    2014-06-01

    We compared theoretical and observational molecular mass fractions (fmol: ratio of molecular gas density to total gas density) using observational data of ten nearby spiral galaxies. For determination of fmol, the three parameters-interstellar pressure P, UV radiation U, and metallicity Z-were obtained from the spectral line data of 12CO(J = 1-0), H I, Hα, [O III], and [O II]. Interstellar pressure was calculated with the sum of the hydrogen gas densities and the stellar potential based on the Ks-band data. For most data other than metallicity, we used archived NRO CO Atlas, THINGS, SINGS, and 2MASS data. For comparison, we also investigated the dependence of the CO-to-H2 conversion factor XCO. It was found that the theoretical fmol agreed with the observational fmol only when the interstellar pressure is calculated with both the gas density and stellar disk potential. To fit observations more accurately, either the metallicity or the UV radiation needs to be adjusted. It was also found that, in UV radiation scaling, scaling factor γ has a correlation with the diffuse fraction of the Hα emission line data, fDIG. As for XCO, it was shown that the difference between both values of fmol becomes the least when XCO is 1.0 × 1020 cm-2 (K km s-1)-1.

  10. Stellar metallicity of the extended disk and distance of the spiral galaxy NGC 3621

    SciTech Connect

    Kudritzki, Rolf-Peter; Bresolin, Fabio; Hosek, Matthew W. Jr.; Urbaneja, Miguel A.; Przybilla, Norbert E-mail: bresolin@ifa.hawaii.edu E-mail: Miguel.Urbaneja-Perez@uibk.ac.at

    2014-06-10

    Low resolution (∼4.5 Å) ESO VLT/FORS spectra of blue supergiant stars are analyzed to determine stellar metallicities (based on elements such as iron, titanium, and magnesium) in the extended disk of the spiral galaxy, NGC 3621. Mildly subsolar metallicity (–0.30 dex) is found for the outer objects beyond 7 kpc, independent of galactocentric radius and compatible with the absence of a metallicity gradient, confirming the results of a recent investigation of interstellar medium H II region gas oxygen abundances. The stellar metallicities are slightly higher than those from the H II regions when based on measurements of the weak forbidden auroral oxygen line at 4363 Å but lower than the ones obtained with the R {sub 23} strong line method. It is shown that the present level of metallicity in the extended disk cannot be the result of chemical evolution over the age of the disk with the present rate of in situ star formation. Additional mechanisms must be involved. In addition to metallicity, stellar effective temperatures, gravities, interstellar reddening, and bolometric magnitudes are determined. After the application of individual reddening corrections for each target, the flux-weighted gravity-luminosity relationship of blue supergiant stars is used to obtain a distance modulus of 29.07 ± 0.09 mag (distance D = 6.52 ± 0.28 Mpc). This new distance is discussed in relation to Cepheid and the tip of the red giant branch distances.

  11. High-Resolution Imaging of the Multiphase Interstellar Thick Disk in Two Edge-On Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Howk, J. Christopher; Rueff, K.

    2009-01-01

    We present broadband and narrow-band images, acquired from Hubble Space Telescope WFPC2 and WIYN 3.5 m telescope respectively, of two edge-on spiral galaxies, NGC 4302 and NGC 4013. These high-resolution images (BVI + H-alpha) provide a detailed view of the thick disk interstellar medium (ISM) in these galaxies. Both galaxies show prominent extraplanar dust-bearing clouds viewed in absorption against the background stellar light. Individual clouds are found to z 2 kpc in each galaxy. These clouds each contain >10^4 to >10^5 solar masses of gas. Both galaxies have extraplanar diffuse ionized gas (DIG), as seen in our H-alpha images and earlier work. In addition to the DIG, discrete H II regions are found at heights up to 1 kpc from both galaxies. We compare the morphologies of the dusty clouds with the DIG in these galaxies and discuss the relationship between these components of the thick disk ISM.

  12. THE SPLASH SURVEY: KINEMATICS OF ANDROMEDA's INNER SPHEROID

    SciTech Connect

    Dorman, Claire E.; Guhathakurta, Puragra; and others

    2012-06-20

    The combination of large size, high stellar density, high metallicity, and Sersic surface brightness profile of the spheroidal component of the Andromeda galaxy (M31) within R{sub proj} {approx} 20 kpc suggests that it is unlike any subcomponent of the Milky Way. In this work we capitalize on our proximity to and external view of M31 to probe the kinematical properties of this 'inner spheroid'. We employ a Markov chain Monte Carlo (MCMC) analysis of resolved stellar kinematics from Keck/DEIMOS spectra of 5651 red giant branch stars to disentangle M31's inner spheroid from its stellar disk. We measure the mean velocity and dispersion of the spheroid in each of five spatial bins after accounting for a locally cold stellar disk as well as the Giant Southern Stream and associated tidal debris. For the first time, we detect significant spheroid rotation (v{sub rot} {approx} 50 km s{sup -1}) beyond R{sub proj} {approx} 5 kpc. The velocity dispersion decreases from about 140 km s{sup -1} at R{sub proj} = 7 kpc to 120 km s{sup -1} at R{sub proj} = 14 kpc, consistent to 2{sigma} with existing measurements and models. We calculate the probability that a given star is a member of the spheroid and find that the spheroid has a significant presence throughout the spatial extent of our sample. Lastly, we show that the flattening of the spheroid is due to velocity anisotropy in addition to rotation. Though this suggests that the inner spheroid of M31 more closely resembles an elliptical galaxy than a typical spiral galaxy bulge, it should be cautioned that our measurements are much farther out (2-14r{sub eff}) than for the comparison samples.

  13. The spiral structure of the Galaxy revealed by CS sources and evidence for the 4:1 resonance

    NASA Astrophysics Data System (ADS)

    Lépine, J. R. D.; Roman-Lopes, A.; Abraham, Zulema; Junqueira, T. C.; Mishurov, Yu. N.

    2011-06-01

    We present a map of the spiral structure of the Galaxy, as traced by molecular carbon monosulphide (CS) emission associated with IRAS sources which are believed to be compact H II regions. The CS line velocities are used to determine the kinematic distances of the sources in order to investigate their distribution in the galactic plane. This allows us to use 870 objects to trace the arms, a number larger than that of previous studies based on classical H II regions. The distance ambiguity of the kinematic distances, when it exists, is solved by different procedures, including the latitude distribution and an analysis of the longitude-velocity diagram. The study of the spiral structure is complemented with other tracers: open clusters, Cepheids, methanol masers and H II regions. The well-defined spiral arms are seen to be confined inside the corotation radius, as is often the case in spiral galaxies. We identify a square-shaped sub-structure in the CS map with that predicted by stellar orbits at the 4:1 resonance (four epicycle oscillations in one turn around the galactic centre). The sub-structure is found at the expected radius, based on the known pattern rotation speed and epicycle frequency curve. An inner arm presents an end with strong inwards curvature and intense star formation that we tentatively associate with the region where this arm surrounds the extremity of the bar, as seen in many barred galaxies. Finally, a new arm with concave curvature is found in the Sagitta to Cepheus region of the sky. The observed arms are interpreted in terms of perturbations similar to grooves in the gravitational potential of the disc, produced by crowding of stellar orbits.

  14. Stellar populations in the edge-on spiral galaxy NGC 4565. I - Surface brightness and color distributions

    NASA Technical Reports Server (NTRS)

    Jensen, E. B.; Thuan, T. X.

    1982-01-01

    Results are presented for photographic and photoelectric photometry of the edge-on Sb galaxy NGC 4565. Major-axis, minor-axis, and perpendicular surface brightness profiles are determined, along with color gradients parallel and perpendicular to the plane of the galaxy. It is found that the galaxy's light can be deconvolved naturally into five components: (1) a starlike nucleus located at the center of the bulge and the edge of the dust lane; (2) a thin disk containing the gas and dust, the young OB stars, and the spiral arms; (3) a thick disk that may be a locally isothermal sheet of old Population I metal-rich stars; (4) a bulge that merges smoothly into the thick disk at a radial distance of about 2.9 kpc; and (5) a corona whose light dominates the perpendicular profiles from about 2.9 to at least 8.2 kpc above the galactic plane.

  15. The spatially resolved Kennicutt-Schmidt relation in the H I-dominated regions of spiral and dwarf irregular galaxies

    NASA Astrophysics Data System (ADS)

    Roychowdhury, Sambit; Huang, Mei-Ling; Kauffmann, Guinevere; Wang, Jing; Chengalur, Jayaram N.

    2015-06-01

    We study the Kennicutt-Schmidt relation between average star formation rate (SFR) and average cold gas surface density in the H I-dominated ISM of nearby spiral and dwarf irregular galaxies. We divide galaxies into grid cells varying from sub-kpc to tens of kpc in size. Grid-cell measurements of low SFRs using Hα emission can be biased and scatter may be introduced because of non-uniform sampling of the IMF or because of stochastically varying star formation. In order to alleviate these issues, we use far-ultraviolet emission to trace SFR, and we sum up the fluxes from different bins with the same gas surface density to calculate the average ΣSFR at a given value of Σgas. We study the resulting Kennicutt-Schmidt relation in 400 pc, 1 kpc and 10 kpc scale grids in nearby massive spirals and in 400 pc scale grids in nearby faint dwarf irregulars. We find a relation with a power-law slope of 1.5 in the H I-dominated regions for both kinds of galaxies. The relation is offset towards longer gas consumption time-scales compared to the molecular-hydrogen-dominated centres of spirals, but the offset is an order of magnitude less than that quoted by earlier studies. Our results lead to the surprising conclusion that conversion of gas to stars is independent of metallicity in the H I-dominated regions of star-forming galaxies. Our observed relations are better fit by a model of star formation based on thermal and hydrostatic equilibrium in the ISM, in which stellar heating and supernova feedback set the thermal and turbulent pressure.

  16. Handedness asymmetry of spiral galaxies with z<0.3 shows cosmic parity violation and a dipole axis

    NASA Astrophysics Data System (ADS)

    Shamir, Lior

    2012-08-01

    A dataset of 126,501 spiral galaxies taken from Sloan Digital Sky Survey was used to analyze the large-scale galaxy handedness in different regions of the local universe. The analysis was automated by using a transformation of the galaxy images to their radial intensity plots, which allows automatic analysis of the galaxy spin and can therefore be used to analyze a large galaxy dataset. The results show that the local universe (z<0.3) is not isotropic in terms of galaxy spin, with probability P<˜5.8ṡ10-6 of such asymmetry to occur by chance. The handedness asymmetries exhibit an approximate cosine dependence, and the most likely dipole axis was found at RA=132°, DEC=32° with 1σ error range of 107°-179° for the RA. The probability of such axis to occur by chance is P<1.95ṡ10-5. The amplitude of the handedness asymmetry reported in this Letter is generally in agreement with Longo, but the statistical significance is improved by a factor of 40, and the direction of the axis disagrees somewhat.

  17. THE TWO-PHASE FORMATION HISTORY OF SPIRAL GALAXIES TRACED BY THE COSMIC EVOLUTION OF THE BAR FRACTION

    SciTech Connect

    Kraljic, Katarina; Bournaud, Frederic

    2012-09-20

    We study the evolution of galactic bars and the link with disk and spheroid formation in a sample of zoom-in cosmological simulations. Our simulation sample focuses on galaxies with present-day stellar masses in the 10{sup 10}-10{sup 11} M{sub Sun} range, in field and loose group environments, with a broad variety of mass growth histories. In our models, bars are almost absent from the progenitors of present-day spirals at z > 1.5, and they remain rare and generally too weak to be observable down to z Almost-Equal-To 1. After this characteristic epoch, the fractions of observable and strong bars rise rapidly, bars being present in 80% of spiral galaxies and easily observable in two thirds of these at z {<=} 0.5. This is quantitatively consistent with the redshift evolution of the observed bar fraction, although the latter is presently known up to z Almost-Equal-To 0.8 because of band-shifting and resolution effects. Our models hence predict that the decrease in the bar fraction with increasing redshift should continue with a fraction of observable bars not larger than 10%-15% in disk galaxies at z > 1. Our models also predict later bar formation in lower-mass galaxies, in agreement with existing data. We find that the characteristic epoch of bar formation, namely redshift z Almost-Equal-To 0.8-1 in the studied mass range, corresponds to the epoch at which today's spirals acquire their disk-dominated morphology. At higher redshift, disks tend to be rapidly destroyed by mergers and gravitational instabilities and rarely develop significant bars. We hence suggest that the bar formation epoch corresponds to the transition between an early 'violent' phase of spiral galaxy formation at z {>=} 1 and a late 'secular' phase at z {<=} 0.8. In the secular phase, the presence of bars substantially contributes to the growth of the (pseudo-)bulge, but the bulge mass budget remains statistically dominated by the contribution of mergers, interactions, and disk instabilities at

  18. ROSAT observations of nearby galaxies

    NASA Astrophysics Data System (ADS)

    Pietsch, W.; Truemper, J.

    1993-12-01

    First results of pointed and All Sky Survey observations of galaxies with the X-ray observatory satellite ROSAT are reported. During observations of the Magellanic Clouds and the Andromeda galaxy new super-soft X-ray sources have been detected. This new class of luminous X-ray sources may help to solve the millisecond pulsar progenitor problem. Due to the improved sensitivity and longer observation times of ROSAT new X-ray point sources have been resolved in several nearby galaxies. The diffuse emission of the Large Magellanic Cloud that was already reported by HEAO 2 (EINSTEIN) has been mapped in detail. It shows a lot of fine structure and temperatures around 5 x 106 K. The improved low energy response of ROSAT led to the discovery of 106 K gas from the spiral galaxy M101 and the halo of the starburst galaxy NGC 253. No diffuse emission was detected from the halo of the edge-on spiral galaxy NGC 5907.

  19. Populations of High-Luminosity Density-Bounded HII Regions in Spiral Galaxies? Evidence and Implications

    NASA Technical Reports Server (NTRS)

    Beckman, J. E.; Rozas, M.; Zurita, A.; Watson, R. A.; Knapen, J. H.

    2000-01-01

    In this paper we present evidence that the H II regions of high luminosity in disk galaxies may be density bounded, so that a significant fraction of the ionizing photons emitted by their exciting OB stars escape from the regions. The key piece of evidence is the presence, in the Ha luminosity functions (LFs) of the populations of H iI regions, of glitches, local sharp peaks at an apparently invariant luminosity, defined as the Stromgren luminosity Lstr), LH(sub alpha) = Lstr = 10(sup 38.6) (+/- 10(sup 0.1)) erg/ s (no other peaks are found in any of the LFs) accompanying a steepening of slope for LH(sub alpha) greater than Lstr This behavior is readily explicable via a physical model whose basic premises are: (a) the transition at LH(sub alpha) = Lstr marks a change from essentially ionization bounding at low luminosities to density bounding at higher values, (b) for this to occur the law relating stellar mass in massive star-forming clouds to the mass of the placental cloud must be such that the ionizing photon flux produced within the cloud is a function which rises more steeply than the mass of the cloud. Supporting evidence for the hypothesis of this transition is also presented: measurements of the central surface brightnesses of H II regions for LH(sub alpha) less than Lstr are proportional to L(sup 1/3, sub H(sub alpha)), expected for ionization bounding, but show a sharp trend to a steeper dependence for LH(sub alpha) greater than Lstr, and the observed relation between the internal turbulence velocity parameter, sigma, and the luminosity, L, at high luminosities, can be well explained if these regions are density bounded. If confirmed, the density-bounding hypothesis would have a number of interesting implications. It would imply that the density-bounded regions were the main sources of the photons which ionize the diffuse gas in disk galaxies. Our estimates, based on the hypothesis, indicate that these regions emit sufficient Lyman continuum not only to

  20. Kinematics and excitation of the nuclear spiral in the active galaxy Arp 102B

    NASA Astrophysics Data System (ADS)

    Couto, G. S.; Storchi-Bergmann, T.; Axon, D. J.; Robinson, A.; Kharb, P.; Riffel, R. A.

    2014-10-01

    We present a two-dimensional analysis of the gaseous excitation and kinematics of the inner 2.5 × 1.7 kpc^{2} of the LINER/Seyfert 1 galaxy Arp 102B, from optical spectra obtained with the GMOS integral field spectrograph on the Gemini North telescope at a spatial resolution of ≍ 250 pc. Emission-line flux maps show the same two-armed nuclear spiral we have discovered in previous observations with the HST-ACS camera. One arm reaches 1 kpc to the east and the other 500 pc to the west, with a 8.4 GHz VLA bent radio jet correlating with the former. Gas excitation along the arms is low, with line ratios typical of LINERs. The gas density is highest at the nucleus and in the northern border of the east arm, at a region where the radio jet seems to be deflected. Centroid velocity maps suggest that most gas is in rotation in an inclined disk with line of nodes along position angle ≍ 88°, redshifts to the west and blueshifts to the east, with lower blueshifts correlated with the eastern arm and radio jet. This correlation suggests that the jet is interacting with gas in the disk. Channel maps show blueshifts but also some redshifts at the eastern arm and jet location which can be interpreted as originated in the front and back walls of an outflow pushed by the radio jet, suggesting also that the outflow is launched close to the plane of the sky. We propose a scenario in which gas has been recently captured by Arp 102B in an interaction with Arp 102A, settling in a disk rotating around the nucleus of Arp 102B and triggering its nuclear activity. A nuclear jet is pushing the circumnuclear gas, giving origin to the nuclear arms.

  1. Ram-pressure stripped molecular gas in the Virgo spiral galaxy NGC 4522

    NASA Astrophysics Data System (ADS)

    Vollmer, B.; Braine, J.; Pappalardo, C.; Hily-Blant, P.

    2008-11-01

    IRAM 30 m 12CO(1-0) and 12CO(2-1) HERA observations are presented for the ram-pressure stripped Virgo spiral galaxy NGC 4522. The CO emission is detected in the galactic disk and the extraplanar gas. The extraplanar CO emission follows the morphology of the atomic gas closely but is less extended. The CO maxima do not appear to correspond to regions where there is peak massive star formation as probed by Hα emission. The presence of molecular gas is a necessary but not sufficient condition for star formation. Compared to the disk gas, the molecular fraction of the extraplanar gas is 30% lower and the star formation efficiency of the extraplanar gas is about 3 times lower. The comparison with an existing dynamical model extended by a recipe for distinguishing between atomic and molecular gas shows that a significant part of the gas is stripped in the form of overdense arm-like structures. It is argued that the molecular fraction depends on the square root of the total large-scale density. Based on the combination of the CO/Hα and an analytical model, the total gas density is estimated to be about 4 times lower than that of the galactic disk. Molecules and stars form within this dense gas according to the same laws as in the galactic disk, i.e. they mainly depend on the total large-scale gas density. Star formation proceeds where the local large-scale gas density is highest. Given the complex 3D morphology this does not correspond to the peaks in the surface density. In the absence of a confining gravitational potential, the stripped gas arms will most probably disperse; i.e. the density of the gas will decrease and star formation will cease. Based on IRAM 30 m HERA observations.

  2. M/L, Hα Rotation Curves, and H I Gas Measurements for 329 Nearby Cluster and Field Spirals. III. Evolution in Fundamental Galaxy Parameters

    NASA Astrophysics Data System (ADS)

    Vogt, Nicole P.; Haynes, Martha P.; Giovanelli, Riccardo; Herter, Terry

    2004-06-01

    We have conducted a study of optical and H I properties of spiral galaxies (size, luminosity, Hα flux distribution, circular velocity, H I gas mass) to investigate causes (e.g., nature vs. nurture) for variation within the cluster environment. We find H I-deficient cluster galaxies to be offset in fundamental plane space, with disk scale lengths decreased by a factor of 25%. This may be a relic of early galaxy formation, caused by the disk coalescing out of a smaller, denser halo (e.g., higher concentration index) or by truncation of the hot gas envelope due to the enhanced local density of neighbors, although we cannot completely rule out the effect of the gas stripping process. The spatial extent of Hα flux and the B-band radius also decreases, but only in early-type spirals, suggesting that gas removal is less efficient within steeper potential wells (or that stripped late-type spirals are quickly rendered unrecognizable). We find no significant trend in stellar mass-to-light ratios or circular velocities with H I gas content, morphological type, or clustercentric radius, for star-forming spiral galaxies throughout the clusters. These data support the findings of a companion paper that gas stripping promotes a rapid truncation of star formation across the disk and could be interpreted as weak support for dark matter domination over baryons in the inner regions of spiral galaxies.

  3. Correlation of far-infrared emission and radio continuum emission along the major axis of edge-on spiral galaxies

    NASA Technical Reports Server (NTRS)

    Heikkila, Bryant; Webber, William R.

    1994-01-01

    Using new High Resolution far-infrared (FIR) images we have determined FIR flux densities, the FIR luminosity, and intensity profiles along the major axis for eight nearby edge-on spiral galaxies. We present spatial comparisons between the FIR profiles in three of the four IRAS Bands (25, 60, 100 microns). We also present direct spatial comparisons between the 60 micron intensity profiles and intensity profiles from 20 cm radio continuum maps with identical resolution (approx. 60 sec) obtained from J. J. Condon. Using these profiles we have evaluated the 60 micron-to-20 cm ratio Q(sub 60) along the major axis for each galaxy and have compared the results to global Q(sub 60) values. This analysis reveals that a considerable amount of complicated structure exists within the disk of spiral galaxies. Closer examination of this disk structure will make it possible to place further constraints on the well known global far-infrared and radio continuum emission correlation.

  4. STELLAR TIDAL STREAMS IN SPIRAL GALAXIES OF THE LOCAL VOLUME: A PILOT SURVEY WITH MODEST APERTURE TELESCOPES

    SciTech Connect

    MartInez-Delgado, David; Zibetti, Stefano; Rix, Hans-Walter; Gabany, R. Jay; Crawford, Ken; Majewski, Steven R.; McDavid, David A.; Fliri, Juergen; Carballo-Bello, Julio A.; Bardalez-Gagliuffi, Daniella C.; Trujillo, Ignacio; Penarrubia, Jorge; Chonis, Taylor S.; Madore, Barry; Schirmer, Mischa

    2010-10-15

    Within the hierarchical framework for galaxy formation, minor merging and tidal interactions are expected to shape all large galaxies to the present day. As a consequence, most seemingly normal disk galaxies should be surrounded by spatially extended stellar 'tidal features' of low surface brightness. As part of a pilot survey for such interaction signatures, we have carried out ultra deep, wide field imaging of eight isolated spiral galaxies in the Local Volume, with data taken at small (D = 0.1-0.5 m) robotic telescopes that provide exquisite surface brightness sensitivity ({mu}{sub lim}(V) {approx} 28.5 mag arcsec{sup -2}). This initial observational effort has led to the discovery of six previously undetected extensive (to {approx}30 kpc) stellar structures in the halos surrounding these galaxies, likely debris from tidally disrupted satellites. In addition, we confirm and clarify several enormous stellar over-densities previously reported in the literature, but never before interpreted as tidal streams. Even this pilot sample of galaxies exhibits strikingly diverse morphological characteristics of these extended stellar features: great circle-like features that resemble the Sagittarius stream surrounding the Milky Way, remote shells and giant clouds of presumed tidal debris far beyond the main stellar body, as well as jet-like features emerging from galactic disks. Together with presumed remains of already disrupted companions, our observations also capture surviving satellites caught in the act of tidal disruption. A qualitative comparison with available simulations set in a {Lambda}Cold Dark Matter cosmology (that model the stellar halo as the result of satellite disruption evolution) shows that the extraordinary variety of stellar morphologies detected in this pilot survey matches that seen in those simulations. The common existence of these tidal features around 'normal' disk galaxies and the morphological match to the simulations constitutes new evidence

  5. Gas-phase Oxygen Abundances and Radial Metallicity Gradients in the Two nearby Spiral Galaxies NGC 7793 and NGC 4945

    NASA Astrophysics Data System (ADS)

    Stanghellini, Letizia; Magrini, Laura; Casasola, Viviana

    2015-10-01

    Gas-phase abundances in H ii regions of two spiral galaxies, NGC 7793 and NGC 4945, have been studied to determine their radial metallicity gradients. We used the strong-line method to derive oxygen abundances from spectra acquired with GMOS-S, the multi-object spectrograph on the 8 m Gemini South telescope. We found that NGC 7793 has a well-defined gas-phase radial oxygen gradient of -0.321 ± 0.112 dex {R}25-1 (or -0.054 ± 0.019 dex kpc-1) in the galactocentric range 0.17 < RG/R25 < 0.82, not dissimilar from gradients calculated with direct abundance methods in galaxies of similar mass and morphology. We also determined a shallow radial oxygen gradient in NGC 4945, -0.253 ± 0.149 dex {R}25-1 (or -0.019 ± 0.011 dex kpc-1) for 0.04 < RG/R25 < 0.51, where the larger relative uncertainty derives mostly from the larger inclination of this galaxy. NGC 7793 and NGC 4945 have been selected for this study because they are similar, in mass and morphology, to M33 and the Milky Way, respectively. Since at zeroth order we expect the radial metallicity gradients to depend on mass and galaxy type, we compared our galaxies in the framework of radial metallicity models best suited for M33 and the Galaxy. We found a good agreement between M33 and NGC 7793, pointing toward similar evolution for the two galaxies. We notice instead differences between NGC 4945 and the radial metallicity gradient model that best fits the Milky Way. We found that these differences are likely related to the presence of an active galactic nucleus combined with a bar in the central regions of NGC 4945, and to its interacting environment.

  6. Recent Results from SPLASH: Chemical Abundances and Kinematics of Andromeda's Stellar Halo

    NASA Astrophysics Data System (ADS)

    Gilbert, Karoline M.; Beaton, Rachael; Dorman, Claire

    2016-08-01

    Large scale surveys of Andromeda's resolved stellar populations have revolutionized our view of this galaxy over the past decade. The combination of large-scale, contiguous photometric surveys and pointed spectroscopic surveys has been particularly powerful for discovering substructure and disentangling the structural components of Andromeda. The SPLASH (Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo) survey consists of broad- and narrow-band imaging and spectroscopy of red giant branch stars in lines of sight ranging in distance from 2 kpc to more than 200 kpc from Andromeda's center. The SPLASH data reveal a power-law surface brightness profile extending to at least two-thirds of Andromeda's virial radius (Gilbert et al. 2012), a metallicity gradient extending to at least 100 kpc from Andromeda's center (Gilbert et al. 2014), and evidence of a significant population of heated disk stars in Andromeda's inner halo (Dorman et al. 2013). We are also using the velocity distribution of halo stars to measure the tangential motion of Andromeda (Beaton et al., in prep).

  7. Integral field spectroscopy and multi-wavelength imaging of the nearby spiral galaxy NGC 5668: a case for MEGARA

    NASA Astrophysics Data System (ADS)

    Marino, R. A.; Gil de Paz, A.; Castillo-Morales, A.; Muñoz-Mateos, J. C.; Sánchez, S. F.; Pérez-González, P. G.; Gallego, J.; Zamorano, J.; Alonso-Herrero, A.; Boissier, S.

    2013-05-01

    In order to improve our understanding of the mechanisms that drive the evolution of disk galaxies we analyze the full bi-dimensional spectral cube of the nearby spiral galaxy NGC 5668, which was obtained as a mosaic of 6 pointings, covering a total area of 2 × 3 arcmin^{2}, obtained with the PPAK Integral Field Unit at the Calar Alto (CAHA) observatory 3.5 m telescope. From these data we obtain the bidimensional spatial distribution maps of the attenuation of the ionized gas, and chemical abundances of oxygen. We find a mean ionized-gas attenuation of A_V˜1 mag, with the gas attenuation appearing larger than the continuum attenuation by a factor of 3. With respect to the oxygen abundance, we find that, while inwards of r ˜36''˜ 4.4kpc ˜ 0.36 ({D_{25}}/{2}) the derived O/H ratio follows the radial gradient typical of the disks of spiral galaxies, the abundance gradient beyond r˜36'' flattens out. The multi-wavelength surface brightness profiles of NGC 5668 are compared with those predicted by chemo-spectrophotometric evolutionary models of galaxy disks in the context of the inside-out scenario of disk formation. Both the deviations of the color profiles and the shape of the metallicity radial distribution indicate that a secondary mechanism, possibly gas transfer induced by the presence of a young bar, must have played a role in shaping the recent chemical and star formation histories of NGC5668 beyond what is predicted by the inside-out scenario. This study demonstrates the strength of the combination of IFU and multi-wavelength imaging data. With MEGARA, the future optical IFU & MOS for 10.4-m GTC we will fill the gap currently existing in astronomical instrumentation with high spectral resolution and large area coverage simultaneously addressing such fundamental issues in galactic structure and evolution.

  8. Herschel-SPIRE Fourier transform spectroscopy of the nearby spiral galaxy IC 342

    NASA Astrophysics Data System (ADS)

    Rigopoulou, D.; Hurley, P. D.; Swinyard, B. M.; Virdee, J.; Croxall, K. V.; Hopwood, R. H. B.; Lim, T.; Magdis, G. E.; Pearson, C. P.; Pellegrini, E.; Polehampton, E.; Smith, J.-D.

    2013-09-01

    We present observations of the nearby spiral galaxy IC 342 with the Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier transform spectrometer. The spectral range afforded by SPIRE, 196-671 μm, allows us to access a number of 12CO lines from J = 4-3 to J = 13-12 with the highest J transitions observed for the first time. In addition we present measurements of 13CO, [C I] and [N II]. We use a radiative transfer code coupled with Bayesian likelihood analysis to model and constrain the temperature, density and column density of the gas. We find two 12CO components, one at 35 K and one at 400 K with CO column densities of 6.3 × 1017 and 0.4 × 1017 cm-2 and CO gas masses of 1.26 × 107 and 0.15 × 107 M⊙ for the cold and warm components, respectively. The inclusion of the high-J 12CO line observations indicate the existence of a much warmer gas component (˜400 K) confirming earlier findings from H2 rotational line analysis from Infrared Space Observatory and Spitzer. The mass of the warm gas is 10 per cent of the cold gas, but it likely dominates the CO luminosity. In addition, we detect strong emission from [N II] 205 μm and the 3P1 → 3P0 and 3P2 → 3P1 [C I] lines at 370 and 608 μm, respectively. The measured 12CO line ratios can be explained by photon-dominated region (PDR) models although additional heating by e.g. cosmic rays cannot be excluded. The measured [C I] line ratio together with the derived [C] column density of 2.1 × 1017 cm-2 and the fact that [C I] is weaker than CO emission in IC 342 suggests that [C I] likely arises in a thin layer on the outside of the CO emitting molecular clouds consistent with PDRs playing an important role.

  9. THE THICK DISKS OF SPIRAL GALAXIES AS RELICS FROM GAS-RICH, TURBULENT, CLUMPY DISKS AT HIGH REDSHIFT

    SciTech Connect

    Bournaud, Frederic; Martig, Marie; Elmegreen, Bruce G.

    2009-12-10

    The formation of thick stellar disks in spiral galaxies is studied. Simulations of gas-rich young galaxies show formation of internal clumps by gravitational instabilities, clump coalescence into a bulge, and disk thickening by strong stellar scattering. The bulge and thick disks of modern galaxies may form this way. Simulations of minor mergers make thick disks too, but there is an important difference. Thick disks made by internal processes have a constant scale height with galactocentric radius, but thick disks made by mergers flare. The difference arises because in the first case, perpendicular forcing and disk-gravity resistance are both proportional to the disk column density, so the resulting scale height is independent of this density. In the case of mergers, perpendicular forcing is independent of the column density and the low-density regions get thicker; the resulting flaring is inconsistent with observations. Late-stage gas accretion and thin-disk growth are shown to preserve the constant scale heights of thick disks formed by internal evolution. These results reinforce the idea that disk galaxies accrete most of their mass smoothly and acquire their structure by internal processes, in particular through turbulent and clumpy phases at high redshift.

  10. 2MTF III. H I 21 cm observations of 1194 spiral galaxies with the Green Bank Telescope

    NASA Astrophysics Data System (ADS)

    Masters, Karen L.; Crook, Aidan; Hong, Tao; Jarrett, T. H.; Koribalski, Bärbel S.; Macri, Lucas; Springob, Christopher M.; Staveley-Smith, Lister

    2014-09-01

    We present H I 21 cm observations of 1194 galaxies out to a redshift of 10 000 km s-1 selected as inclined spirals (i ≳ 60°) from the 2MASS redshift survey. These observations were carried out at the National Radio Astronomy Observatory Robert C. Byrd Green Bank Telescope (GBT). This observing programme is part of the 2MASS Tully-Fisher (2MTF) survey. This project will combine H I widths from these GBT observations with those from further dedicated observing at the Parkes Telescope, from the Arecibo Legacy Fast Arecibo L-band Feed Array survey at Arecibo, and S/N > 10 and spectral resolution vres < 10 km s-1 published widths from a variety of telescopes. We will use these H I widths along with 2MASS photometry to estimate Tully-Fisher distances to nearby spirals and investigate the peculiar velocity field of the local Universe. In this paper, we report on detections of neutral hydrogen in emission in 727 galaxies, and measure good signal to noise and symmetric H I global profiles suitable for use in the Tully-Fisher relation in 484.

  11. INTEGRAL-FIELD STELLAR AND IONIZED GAS KINEMATICS OF PECULIAR VIRGO CLUSTER SPIRAL GALAXIES

    SciTech Connect

    Cortés, Juan R.; Hardy, Eduardo; Kenney, Jeffrey D. P. E-mail: ehardy@nrao.cl

    2015-01-01

    We present the stellar and ionized gas kinematics of 13 bright peculiar Virgo cluster galaxies observed with the DensePak Integral Field Unit at the WIYN 3.5 m telescope in order to look for kinematic evidence that these galaxies have experienced gravitational interactions or gas stripping. Two-dimensional maps of the stellar velocity V, stellar velocity dispersion σ, and the ionized gas velocity (Hβ and/or [O III]) are presented for the galaxies in the sample. The stellar rotation curves and velocity dispersion profiles are determined for 13 galaxies, and the ionized gas rotation curves are determined for 6 galaxies. Misalignments between the optical and kinematical major axes are found in several galaxies. While in some cases this is due to a bar, in other cases it seems to be associated with gravitational interaction or ongoing ram pressure stripping. Non-circular gas motions are found in nine galaxies, with various causes including bars, nuclear outflows, or gravitational disturbances. Several galaxies have signatures of kinematically distinct stellar components, which are likely signatures of accretion or mergers. For all of our galaxies, we compute the angular momentum parameter λ {sub R}. An evaluation of the galaxies in the λ {sub R} ellipticity plane shows that all but two of the galaxies have significant support from random stellar motions, and have likely experienced gravitational interactions. This includes some galaxies with very small bulges and truncated/compact Hα morphologies, indicating that such galaxies cannot be fully explained by simple ram pressure stripping, but must have had significant gravitational encounters. Most of the sample galaxies show evidence for ICM-ISM stripping as well as gravitational interactions, indicating that the evolution of a significant fraction of cluster galaxies is likely strongly impacted by both effects.

  12. The Mass Dependence of Star Formation Histories in Barred Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Carles, Christian; Martel, Hugo; Ellison, Sara L.; Kawata, Daisuke

    2016-08-01

    We performed a series of 29 gasdynamical simulations of disc galaxies, barred and unbarred, with various stellar masses, to study the impact of the bar on star formation history. Unbarred galaxies evolve very smoothly, with a star formation rate (SFR) that varies by at most a factor of three over a period of 2 Gyr. The evolution of barred galaxies is much more irregular, especially at high stellar masses. In these galaxies, the bar drives a substantial amount of gas toward the centre, resulting in a high SFR, and producing a starburst in the most massive galaxies. Most of the gas is converted into stars, and gas exhaustion leads to a rapid drop of star formation after the starburst. In massive barred galaxies (stellar mass M★ > 2 × 1010 M⊙) the large amount of gas funnelled toward the centre is completely consumed by the starburst, while in lower-mass barred galaxies it is only partially consumed. Gas concentration is thus higher in lower-mass barred galaxies than it is in higher-mass ones. Even though unbarred galaxies funnelled less gas toward their centre, the lower SFR allows this gas to accumulate. At late times, the star formation efficiency is higher in barred galaxies than unbarred ones, enabling these galaxies to maintain a higher SFR with a smaller gas supply. Several properties, such as the global SFR, central SFR, or central gas concentration, vary monotonically with time for unbarred galaxies, but not for barred galaxies. Therefore one must be careful when comparing barred and unbarred galaxies that share one observational property, since these galaxies might be at very different stages of their respective evolution.

  13. Development of a hot intergalactic medium in spiral-rich galaxy groups: the example of HCG 16

    NASA Astrophysics Data System (ADS)

    Vrtilek, Jan M.; O'Sullivan, Ewan; David, Laurence P.; Giacintucci, Simona; Zezas, Andreas; Mamon, Gary; Ponman, Trevor J; Raychaudhury, Somak

    2014-08-01

    Galaxy groups provide the environment in which the majority of galaxies evolve, with low velocity dispersions and small galaxy separations that are conducive to tidal interactions and mergers between group members. X-ray observations reveal the frequent presence of hot gas in groups, with larger quantities linked to early-type galaxies, whereas cold gas is common in spiral-dominated groups. Clarification of the origin and role of the hot medium is central to the understanding of the evolution of the galaxy population and of all phases of the IGM.We here report on the nuclear activity, star formation and the high luminosity X-ray binary populations of the spiral-dominated, likely not yet virialized, group HCG 16, as well as on its intra-group medium, based principally on deep (150 ks) Chandra X-ray observations of the group, as well as new Giant Metrewave Radio Telescope (GMRT) 610 MHz radio data. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify what may be a previously unrecognized nuclear source in NGC 838; all are variable. NGC 838 and NGC 839 are both starburst-dominated systems, with galactic superwinds that show X-ray and radio evidence of IGM interaction, but only weak nuclear activity; NGC 848 is also dominated by emission from its starburst.We confirm the existence of a faint, extended low-temperature (0.3 keV) intra-group medium, a subject of some uncertainty in earlier studies. The diffuse emission is strongest in a ridge linking the four principal galaxies, and is at least partly coincident with a large-scale HI tidal filament, indicating that the IGM in the inner part of the group is highly multi-phase. We conclude that starburst winds and shock-heating of stripped HI may play an important role in the early stages of IGM formation, with galactic winds contributing 20-40% of the observed hot gas in the system.

  14. Eclipsing Binaries as Accurate Extragalactic Distance Indicators: Refining the Distance to the Triangulum Spiral Galaxy M33

    NASA Astrophysics Data System (ADS)

    Guinan, Edward F.; Prsa, A.; Fitzpatrick, E. L.; Bonanos, A. Z.; Engle, S. G.; Devinney, E. J.; Recker, G.

    2013-06-01

    For over decade we have been using eclipsing binaries (EBs) to determine accurate distances to Local Group Galaxies such as the Magellanic Clouds & M31 (cf. Fitzpatrick et al. 2003; Vilardell et al. 2010). We (and others) have demonstrated that carefully selected EBs can serve as excellent "Standard Candles." Distances measured from EBs are basically geometric and are essentially free from assumptions and uncertainties that complicate other less direct methods. The radii of the stars are determined to better than a few percent from the time-tested analyses of their light and radial velocity curves. With accurate determinations of radii, Teff (or calibrated flux SEDs) and ISM absorption, it is possible to calculate reliable distances with uncertainties of < 5%. M33 is an important face-on spiral galaxy that still has a large range in its measured distance of ~750 - 960 kpc. We carried out HST/COS and STIS FUV-Near-IR (1150 - 8500A) spectrophotometry & WFPC-2 photometry of the19th mag (O7V +O7V) eclipsing binary D33 J013346.2+304439.9 in M33 to try to improve its distance.This EB was used previously by Bonanos et al. (2006) to determine a distance = 964 +/- 54 kpc. Analysis of the HST FUV-NIR data will yield more accurate Teff, Av, and [Fe/H] measures. These quantities, when combined with the results from existing light and radial velocity curves of Bonanos et al. permit the refined distance to be found with more certainty. We discuss the results and compare them with other recent M33 distances. When a reliable distance is found, M33 could replace the LMC as the primary exgalactic distance calibrator since this Sa spiral has chemical and physical properties more in common with the galaxies used to determine the Hubble Law and Ho. This research supported by HST NASA grants HST-GO-10919 & HST-GO-11725.

  15. Regularities in the distribution of star/gas complexes in the spiral arms of our galaxy and M31

    NASA Astrophysics Data System (ADS)

    Efremov, Yu. N.

    2009-08-01

    The fragmentation of gaseous spiral arms in the outer Galaxy into superclouds has been studied using recently published data on the HI distribution in the Galactic disk. Regular chains of superclouds have been found or confirmed in the Cygnus (Outer) and Carina arms, with the spacings between the superclouds being concentrated near 0.1 and 0.2 of the solar Galactocentric distance. The star complexes in the northwestern arm of the galaxy M31 are spaced, on average, 1.2 kpc apart, with the most distinct chain of complexes being located in the arm region where Beck et al. (1989) detected a strong and wavy (along the arm) magnetic field. Its wavelength turns out to be related to the spacing between the complexes. In this arm, the HII regions lie inside the star complexes, which, in turn, are located inside the gas-dust lane. In contrast, the southwestern arm of M31 is split into a gas-dust lane and a dense stellar arm, which is not fragmented into star complexes. Here, the HII regions are located along the boundary between the gas-dust and stellar components of the arm; other evidence for the presence of a spiral shock wave triggering star formation is also observed, which is probably attributable to the large pitch angle of this segment of the southwestern arm. It may be suggested that the shock wave rapidly leads to star formation everywhere in this arm, while in the northwestern arm, where the shock wave is absent, star formation begins in the superclouds formed along the arm by the magneto-gravitational instability. This is how the chains of star complexes in the northwestern arm of M31 and, obviously, the chains of superclouds in the Carina and Cygnus arms of our Galaxy have been formed. The detection of a regularmagnetic field in the corresponding segments of these arms can be predicted.

  16. GLOBULAR CLUSTER SYSTEMS OF SPIRAL AND S0 GALAXIES: RESULTS FROM WIYN IMAGING OF NGC 1023, NGC 1055, NGC 7332, AND NGC 7339

    SciTech Connect

    Young, Michael D.; Dowell, Jessica L.; Rhode, Katherine L. E-mail: jlwind@astro.indiana.edu

    2012-10-01

    We present results from a study of the globular cluster (GC) systems of four spiral and S0 galaxies imaged as part of an ongoing wide-field survey of the GC systems of giant galaxies. The target galaxies-the SB0 galaxy NGC 1023, the SBb galaxy NGC 1055, and an isolated pair comprised of the Sbc galaxy NGC 7339 and the S0 galaxy NGC 7332-were observed in BVR filters with the WIYN 3.5 m telescope and Minimosaic camera. For two of the galaxies, we combined the WIYN imaging with previously published data from the Hubble Space Telescope and the Keck Observatory to help characterize the GC distribution in the central few kiloparsecs. We determine the radial distribution (surface density of GCs versus projected radius) of each galaxy's GC system and use it to calculate the total number of GCs (N{sub GC}). We find N{sub GC} = 490 {+-} 30, 210 {+-} 40, 175 {+-} 15, and 75 {+-} 10 for NGC 1023, NGC 1055, NGC 7332, and NGC 7339, respectively. We also calculate the GC specific frequency (N{sub GC} normalized by host galaxy luminosity or mass) and find values typical of those of the other spiral and E/S0 galaxies in the survey. The two lenticular galaxies have sufficient numbers of GC candidates for us to perform statistical tests for bimodality in the GC color distributions. We find evidence at a high confidence level (>95%) for two populations in the B - R distribution of the GC system of NGC 1023. We find weaker evidence for bimodality (>81% confidence) in the GC color distribution of NGC 7332. Finally, we identify eight GC candidates that may be associated with the Magellanic dwarf galaxy NGC 1023A, which is a satellite of NGC 1023.

  17. RESOLVED GIANT MOLECULAR CLOUDS IN NEARBY SPIRAL GALAXIES: INSIGHTS FROM THE CANON CO (1-0) SURVEY

    SciTech Connect

    Donovan Meyer, Jennifer; Koda, Jin; Mooney, Thomas; Momose, Rieko; Egusa, Fumi; Carty, Misty; Kennicutt, Robert; Kuno, Nario; Rebolledo, David; Wong, Tony; Sawada, Tsuyoshi; Scoville, Nick

    2013-08-01

    We resolve 182 individual giant molecular clouds (GMCs) larger than 2.5 Multiplication-Sign 10{sup 5} M{sub Sun} in the inner disks of 5 large nearby spiral galaxies (NGC 2403, NGC 3031, NGC 4736, NGC 4826, and NGC 6946) to create the largest such sample of extragalactic GMCs within galaxies analogous to the Milky Way. Using a conservatively chosen sample of GMCs most likely to adhere to the virial assumption, we measure cloud sizes, velocity dispersions, and {sup 12}CO (J = 1-0) luminosities and calculate cloud virial masses. The average conversion factor from CO flux to H{sub 2} mass (or X{sub CO}) for each galaxy is 1-2 Multiplication-Sign 10{sup 20} cm{sup -2} (K km s{sup -1}){sup -1}, all within a factor of two of the Milky Way disk value ({approx}2 Multiplication-Sign 10{sup 20} cm{sup -2} (K km s{sup -1}){sup -1}). We find GMCs to be generally consistent within our errors between the galaxies and with Milky Way disk GMCs; the intrinsic scatter between clouds is of order a factor of two. Consistent with previous studies in the Local Group, we find a linear relationship between cloud virial mass and CO luminosity, supporting the assumption that the clouds in this GMC sample are gravitationally bound. We do not detect a significant population of GMCs with elevated velocity dispersions for their sizes, as has been detected in the Galactic center. Though the range of metallicities probed in this study is narrow, the average conversion factors of these galaxies will serve to anchor the high metallicity end of metallicity-X{sub CO} trends measured using conversion factors in resolved clouds; this has been previously possible primarily with Milky Way measurements.

  18. Kinematics and excitation of the nuclear spiral in the active galaxy Arp 102B

    NASA Astrophysics Data System (ADS)

    Couto, Guilherme S.; Storchi-Bergmann, Thaisa; Axon, David J.; Robinson, Andrew; Kharb, Preeti; Riffel, Rogemar A.

    2013-11-01

    We present a two-dimensional analysis of the gaseous excitation and kinematics of the inner 2.5 × 1.7 kpc2 of the low-ionization nuclear emission-line region (LINER)/Seyfert 1 galaxy Arp 102B, from optical spectra obtained with the Gemini Multi-Object Spectrograph Integral Field Unit on the Gemini North telescope at a spatial resolution of ≈250 pc. Emission-line flux maps show the same two-armed nuclear spiral we have discovered in previous observations with the Hubble Space Telescope Advanced Camera for Surveys. One arm reaches 1 kpc to the east and the other 500 pc to the west, with an 8.4 GHz Very Large Array bent radio jet correlating with the former. Gas excitation along the arms is low, with line ratios typical of LINERs, and which rule out gas ionization by stars. The gas density is highest (≈500-900 cm-3) at the nucleus and in the northern border of the east arm, at a region where the radio jet seems to be deflected. Centroid velocity maps suggest that most gas is in rotation in an inclined disc with line of nodes along position angle ≈88°, redshifts to the west and blueshifts to the east, with lower blueshifts correlated with the eastern arm and radio jet. This correlation suggests that the jet is interacting with gas in the disc. This interaction is supported by the gas excitation as a function of distance from the nucleus, which requires the contribution from shocks. Channel maps show blueshifts but also some redshifts at the eastern arm and jet location which can be interpreted as originated in the front and back walls of an outflow pushed by the radio jet, suggesting also that the outflow is launched close to the plane of the sky. Principal Component Analysis applied to our data supports this interpretation. We estimate a mass outflow rate along the east arm of 0.26-0.32 M⊙ yr- 1 (depending on the assumed outflow geometry), which is between one and two orders of magnitude higher than the mass accretion rate to the active nucleus, implying

  19. Perseo e Andromeda

    NASA Astrophysics Data System (ADS)

    Colona, Paolo

    2004-08-01

    The Perseus-Andromeda group of constellations is the largest in the sky, yet many other Greek myths have no dedicated star at all. The author interprets the importance given to this myth in terms of its role of providing ethnic identify for the Greeks who created it. An accurate analysis of the myth, also including the etymology of the characters' names, shows how it relates to the past encounter between different culture, which are also described. Archaeological research allows us to guess the celestial situation of the epoch when the myth was transposed to the sky. The cultural heritage of the Perseus myth from its origin to the present its outlined.

  20. A Deep Study of the Dwarf Satellites Andromeda XXVIII and Andromeda XXIX

    NASA Astrophysics Data System (ADS)

    Slater, Colin T.; Bell, Eric F.; Martin, Nicolas F.; Tollerud, Erik J.; Ho, Nhung

    2015-06-01

    We present the results of a deep study of the isolated dwarf galaxies Andromeda XXVIII and Andromeda XXIX with Gemini/GMOS and Keck/DEIMOS. Both galaxies are shown to host old, metal-poor stellar populations with no detectable recent star formation, conclusively identifying both of them as dwarf spheroidal galaxies (dSphs). And XXVIII exhibits a complex horizontal branch morphology, which is suggestive of metallicity enrichment and thus an extended period of star formation in the past. Decomposing the horizontal branch into blue (metal-poor, assumed to be older) and red (relatively more metal-rich, assumed to be younger) populations shows that the metal-rich are also more spatially concentrated in the center of the galaxy. We use spectroscopic measurements of the calcium triplet, combined with the improved precision of the Gemini photometry, to measure the metallicity of the galaxies, confirming the metallicity spread and showing that they both lie on the luminosity-metallicity relation for dwarf satellites. Taken together, the galaxies exhibit largely typical properties for dSphs despite their significant distances from M31. These dwarfs thus place particularly significant constraints on models of dSph formation involving environmental processes such as tidal or ram pressure stripping. Such models must be able to completely transform the two galaxies into dSphs in no more than two pericentric passages around M31, while maintaining a significant stellar population gradient. Reproducing these features is a prime requirement for models of dSph formation to demonstrate not just the plausibility of environmental transformation but the capability of accurately recreating real dSphs.

  1. Ionized gas characteristics in the cavities of the gas and dust disc of the spiral galaxy NGC 6946

    NASA Astrophysics Data System (ADS)

    Efremov, Yu. N.; Afanasiev, V. L.; Egorov, O. V.

    2011-07-01

    The parameters of the ionized gas in NGC 6946 (in the [NII] λλ6548, 6583, H α and [SII] λλ6717, 6731 lines) are investigated with the SAO RAS BTA telescope along three positions of the long slit of the SCORPIO focal reducer, passing through a number of large and small cavities of the gaseous disc of the galaxy. These cavities correspond exactly to the cavities in warm dust, visible at 5 - 8µm. We found that everywhere in the direction of NGC 6946 the lines of ionized gas are decomposed into two Gaussians, one of which shows almost constant [SII]/H α and [NII]/H α ratios, as well as an almost constant radial velocity within the measurement errors (about -35… - 50 km/s). This component is in fact the foreground radiation from the diffuse ionized gas of our Galaxy, which is not surprising, given the low (12°) latitude of NGC 6946; a similar component is also present in the emission of neutral hydrogen. The analysis of the component of ionized gas, occurring inNGC 6946, has revealed that it shows signs of shock excitation in the cavities of the gaseous disc of the galaxy. This shock excitation is as well typical for the extraplanar diffuse ionized gas (EDIG), observed in a number of spiral galaxies at their high Z-coordinates. This can most likely be explained by low density of the gas in the NGC 6946 disc (with the usual photoionization) inside the cavities, due to what we see the spectral features of the EDIG gas of NGC 6946, projected onto them, and located outside the plane of the galaxy. In the absence of separation of ionized gas into two components by radial velocities, there is an increasing contribution to the integral line parameters by the EDIG of our Galaxy when the gas density in NGC 6946 decreases, which explains some strange results, obtained in the previous studies. Themorphology of warmdust, visible in the infrared range and HI is almost the same (except for the peripheral parts of the galaxy, where there are no sources of dust heating

  2. Composite bulges: the coexistence of classical bulges and discy pseudo-bulges in S0 and spiral galaxies

    NASA Astrophysics Data System (ADS)

    Erwin, Peter; Saglia, Roberto P.; Fabricius, Maximilian; Thomas, Jens; Nowak, Nina; Rusli, Stephanie; Bender, Ralf; Vega Beltrán, Juan Carlos; Beckman, John E.

    2015-02-01

    We present an analysis of nine S0-Sb galaxies which have (photometric) bulges consisting of two distinct components. The outer component is a flattened, kinematically cool, disc-like structure: a `discy pseudo-bulge'. Embedded inside is a rounder, kinematically hot spheroidal structure: a `classical bulge'. This indicates that pseudo-bulges and classical bulges are not mutually exclusive phenomena: some galaxies have both. The discy pseudo-bulges almost always consist of an exponential disc (scalelengths = 125-870 pc, mean size ˜440 pc) with one or more disc-related subcomponents: nuclear rings, nuclear bars, and/or spiral arms. They constitute 11-59 per cent of the galaxy stellar mass (mean PB/T = 0.33), with stellar masses ˜7 × 109-9 × 1010 M⊙. The classical-bulge components have Sérsic indices of 0.9-2.2, effective radii of 25-430 pc and stellar masses of 5 × 108-3 × 1010 M⊙; they are usually <10 per cent of the galaxy's stellar mass (mean B/T = 0.06). The classical bulges do show rotation, but are clearly kinematically hotter than the discy pseudo-bulges. Dynamical modelling of three systems indicates that velocity dispersions are isotropic in the classical bulges and equatorially biased in the discy pseudo-bulges. In the mass-radius and mass-stellar mass density planes, classical-bulge components follow sequences defined by ellipticals and (larger) classical bulges. Discy pseudo-bulges also fall on this sequence; they are more compact than large-scale discs of similar mass. Although some classical bulges are quite compact, they are as a class clearly distinct from nuclear star clusters in both size and mass; in at least two galaxies they coexist with nuclear clusters. Since almost all the galaxies in this study are barred, they probably also host boxy/peanut-shaped bulges (vertically thickened inner parts of bars). NGC 3368 shows isophotal evidence for such a zone just outside its discy pseudo-bulge, making it a clear case of a galaxy with all three

  3. Using the H-β Emission Line as a Means of Mass Determination for Spiral Galaxy AGNs

    NASA Astrophysics Data System (ADS)

    Cameron, Thomas; Ratz, Lucus; Burris, Debra L.

    2016-01-01

    This study focuses on the AGN of spiral galaxies in hopes to use the H-β line to determine the mass of the central black hole. We are replicating the method of Vestergaard and Peterson by extinction correcting emission spectra from these black holes, both for cosmic redshift and for FeII emissions using IRAF. From there we can accurately measure the full width half max of the H-beta line in these spectrum as well as the lumosity and these paired with the OIII lines give us an estimate on the mass of the black hole. The purpose of this is to compare it to the values to pitch angle measurements and to explore the Mass-Pitch Angle relation as outlined by J. Kennefick from the University of Arkansas.

  4. A RECIPE TO PROBE ALTERNATIVE THEORIES OF GRAVITATION VIA N-BODY NUMERICAL SIMULATIONS. I. SPIRAL GALAXIES

    SciTech Connect

    Brandao, C. S. S.; De Araujo, J. C. N. E-mail: jcarlos.dearaujo@inpe.br

    2012-05-01

    A way to probe alternative theories of gravitation is to study if they could account for the structures of the universe. We therefore modified the well-known Gadget-2 code to probe alternative theories of gravitation through galactic dynamics. As an application, we simulate the evolution of spiral galaxies to probe alternative theories of gravitation whose weak field limits have a Yukawa-like gravitational potential. These simulations show that galactic dynamics can be used to constrain the parameters associated with alternative theories of gravitation. It is worth stressing that the recipe given in this study can be applied to any other alternative theory of gravitation in which the superposition principle is valid.

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

    SciTech Connect

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

    2010-10-15

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

  6. V405 Andromeda Revisited

    NASA Astrophysics Data System (ADS)

    Ribeiro, T.; Baptista, R.; Kafka, S.

    2011-10-01

    We present a multi-epoch time-resolved high-resolution optical spectroscopy study of the short-period (P orb = 11.2 hr) eclipsing M0V+M5V RS CVn binary V405 Andromeda. By means of indirect imaging techniques, namely Doppler imaging, we study the surface activity features of the M0V component of the system. A modified version of a Doppler imaging code, which takes into account the tidal distortion of the surface of the star, is applied to the multi-epoch data set in order to provide indirect images of the stellar surface. The multi-epoch surface brightness distributions show a low intensity "belt" of spots at latitudes ±40° and a noticeable absence of high latitude features or polar spots on the primary star of V405 Andromeda. They also reveal slow evolution of the spot distribution over ~4 yr. An entropy landscape procedure is used in order to find the set of binary parameters that lead to the smoothest surface brightness distributions. As a result, we find M 1 = 0.51 ± 0.03 M sun, M 2 = 0.21 ± 0.01 M sun, R 1 = 0.71 ± 0.01 R sun, and an inclination i = 65° ± 1°. The resulting systemic velocity is distinct for different epochs, raising the possibility of the existence of a third body in the system.

  7. The inner regions of the spiral galaxy NGC 3310 - Evidence for galactic cannibalism

    NASA Astrophysics Data System (ADS)

    Balick, B.; Heckman, T.

    1981-03-01

    High resolution optical and radio images of the inner regions of NGC 3310 are presented. Subtle but important differences exist in the distributions of the stellar continuum on the one hand and the ionized gas and high energy particles on the other. These data and others suggest that a galaxy-galaxy collision has lead to a major disruption in the inner regions which has not yet fully relaxed even at radii of 0.5-1 kpc where the relaxation time scales are only 10 to the power 7.8 yr. An encounter in which an Irr 1 galaxy is being cannibalized by NGC 3110 provides a scenario for the recent history of the galaxy which is in accord with published observations.

  8. High-Latitude Radio Emission in a Sample of Edge-on Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Irwin, Judith A.; English, Jayanne; Sorathia, Barkat

    1999-05-01

    We have mapped 16 edge-on galaxies at 20 cm using the Very Large Array in its C configuration, and a subset of these galaxies in the D configuration at 6 and/or 20 cm, in a search for extended (>~1 kpc) radio continuum emission above and below the plane. For five galaxies, we could form spectral index, energy, and magnetic field maps (assuming minimum energy). While the galaxies were partly chosen by radio flux density, they span a variety of star formation rates (SFRs), and only six might be considered ``starburst'' galaxies. A range of Hubble type and degree of isolation are also represented. The galaxies largely fall on the FIR-radio continuum correlation. They also display a correlation between IR surface brightness and warmth, extending the previously observed relation of Lehnert & Heckman to galaxies with lower star formation rates. We find that all but one galaxy show evidence for nonthermal high-latitude radio continuum emission, suggesting that cosmic-ray (CR) halos are common in star-forming galaxies. Of these, eight galaxies are new detections. The high-latitude emission is seen over a variety of spatial scales and in discrete and/or smooth features. In some cases, discrete features are seen on large scales, suggesting that smooth radio halos may consist, in part, of discrete features combined with low spatial resolution. In general, the discrete features emanate from the disk, but estimates of CR diffusion lengths suggest that diffusion alone is insufficient to transport the particles to the high latitudes seen (>15 kpc in one case). Thus CRs likely diffuse through low-density regions and/or are assisted by other mechanisms (e.g., winds). We searched for correlations between the prevalence of high-latitude radio emission and a number of other properties, including the global SFR, supernova input rate per unit star-forming area, E_A, and environment, and do not find clear correlations with any of these properties. A subset of the data allows, at best

  9. Spitzer Observations of Two Early-Type Spiral Galaxies with Dust Rings

    NASA Astrophysics Data System (ADS)

    Bendo, G. J.; Armus, L.; Calzetti, D.; Dale, D. A.; Draine, B. T.; Engelbracht, C. W.; Gordon, K. D.; Grauer, A.; Helou, G.; Hollenbach, D. J.; Jarrett, T. H.; Joseph, R. D.; Kennicutt, R. C.; Kewley, L. J.; Leitherer, C.; Li, A.; Malhotra, S.; Meyer, M.; Murphy, E. J.; Regan, M. W.; Rieke, G. H.; Rieke, M. J.; Roussel, H.; Sheth, K.; Smith, J. D. T.; Thornley, M. D.; Walter, F.

    2004-12-01

    We present Spitzer images of the SB0/a galaxy NGC 1291 and the SAa galaxy NGC 4594. Both galaxies contain dust rings that can be used for studying the relation between dust emission and star formation activity. At 24 microns, the nuclei of both galaxies are the brightest sources in the galaxies, and dust emission from the rings is relatively weak. At 160 microns, however, the dust rings are more prominent sources; in NGC 4594, the dust ring is the source of virtually all of the 160 micron emission. We discuss whether the 160 micron emission from the rings is related to star formation activity or to heating by older stellar populations, and we examine the relation between dust and PAH emission. For NGC 4594, we also present submillimeter data that show that the nucleus dominates the 850 micron emission. These results demonstate that the 850 micron emission cannot come from the same dust that dominates the 160 micron emission. We examine the possible mechanisms that could be generating the 850 micron emission as well as the implications for dust models and galaxy spectral energy distribution templates.

  10. The spiral density-wave structure of our own Galaxy as traced by open clusters: Least-squares analysis of line-of-sight velocities

    NASA Astrophysics Data System (ADS)

    Griv, Evgeny; Lin, Chien-Cheng; Ngeow, Chow-Choong; Jiang, Ing-Guey

    2014-05-01

    The rotation about the Galactic center of open clusters belonging to the thin component of the Milky Way Galaxy is studied on the basis of line-of-sight velocities and positions for 169 nearby objects taken from the literature. The minor second-order effects caused by the Lin-Shu-type density waves are taken into account by using the least-squares numerical method. Even preliminary, the physical interpretation of the results obtained in this manner shows that (i) among several Fourier modes of collective oscillations developing in the solar neighborhood the one-armed m=1 spiral mode is the main one; the Galaxy has thus significant lopsidedness in the stellar distribution at large radii, (ii) the Sun is located between the major trailing spiral-arm segments in Carina-Sagittarius and Perseus, closer to the outer Perseus one, (iii) the local Cygnus-Orion segment is not a part of the dominant spiral arm but is a minor one, which is due to a secondary Fourier harmonic of the Galaxy’s oscillations, (iv) the pitch angle of the dominant density-wave pattern in the solar vicinity seems to be relatively small, of the order of 7°, and the wavelength (the radial distance between spiral arms) of the m=1 pattern is about 6 kpc, (v) the Galactocentric distance where the velocities of disk rotation and of the spiral density wave (the corotation radius) coincide is located outside of the solar circle; thus, a pattern angular speed lower than the local angular rotation velocity, and finally (vi) the spiral arms of the Galaxy do not represent small deviations of the surface density and gravitational potential from a basic distribution that is axisymmetric in the mean.

  11. CHANG-ES - VI. Probing Supernova energy deposition in spiral galaxies through multiwavelength relationships

    NASA Astrophysics Data System (ADS)

    Li, Jiang-Tao; Beck, Rainer; Dettmar, Ralf-Jürgen; Heald, George; Irwin, Judith; Johnson, Megan; Kepley, Amanda A.; Krause, Marita; Murphy, E. J.; Orlando, Elena; Rand, Richard J.; Strong, A. W.; Vargas, Carlos J.; Walterbos, Rene; Wang, Q. Daniel; Wiegert, Theresa

    2016-02-01

    How a galaxy regulates its supernovae (SNe) energy into different interstellar/circumgalactic medium components strongly affects galaxy evolution. Based on the JVLA D-configuration C- (6 GHz) and L-band (1.6 GHz) continuum observations, we perform statistical analysis comparing multiwavelength properties of the Continuum Haloes in Nearby Galaxies - an EVLA Survey galaxies. The high-quality JVLA data and edge-on orientation enable us for the first time to include the halo into the energy budget for a complete radio-flux-limited sample. We find tight correlations of Lradio with the mid-IR-based star formation rate (SFR). The normalization of our I1.6 GHz/W Hz-1-SFR relation is ˜2-3times of those obtained for face-on galaxies, probably a result of enhanced IR extinction at high inclination. We also find tight correlations between Lradio and the SNe energy injection rate dot{E}_SN(Ia+CC), indicating the energy loss via synchrotron radio continuum accounts for ˜1 of dot{E}_SN, comparable to the energy contained in cosmic ray electrons. The integrated C-to-L-band spectral index is α ˜ 0.5-1.1 for non-active galactic nucleus galaxies, indicating a dominance by the diffuse synchrotron component. The low-scatter Lradio-SFR/L_radio-dot{E}_{SN (Ia+CC)} relationships have superlinear logarithmic slopes at ˜2σ in L band (1.132 ± 0.067/1.175 ± 0.102) while consistent with linear in C band (1.057 ± 0.075/1.100 ± 0.123). The superlinearity could be naturally reproduced with non-calorimeter models for galaxy discs. Using Chandra halo X-ray measurements, we find sublinear LX-Lradio relations. These results indicate that the observed radio halo of a starburst galaxy is close to electron calorimeter, and a galaxy with higher SFR tends to distribute an increased fraction of SNe energy into radio emission (than X-ray).

  12. Investigating the Clustering and Color of Galaxies in the COMBO-17 Chandra Deep Field South Survey and Possible Effects on Spiral Arm Pitch Angle

    NASA Astrophysics Data System (ADS)

    Davis, Benjamin L.; Berlanga Medina, J. E.; Shields, D. W.; Kennefick, J.; Kennefick, D.; Berrier, J.; Seigar, M. S.; Lacy, C. H. S.; AGES

    2010-01-01

    Recent studies by the Arkansas Galaxy Evolution Survey (AGES) collaboration have shown that there is a strong correlation between the pitch angles of field spiral galaxies and the mass of the galaxy's supermassive black holes (SMBHs). For this reason, we are interested in the consistency of measures of average pitch angle across galaxies in different environments. Since galaxies in clusters are more susceptible to galaxy harassment and other effects, we are particularly interested in whether environmental pressures in clusters may have an effect on pitch angle. We have measured the pitch angles of 125 galaxies lying in the Chandra Deep Field South (CDFS). Upon cross-referencing this set with the larger COMBO-17 Survey, we identified several over-dense regions which have been identified as possible clusters in recent literature. Initial results show that when comparing the pitch angle of galaxies in and out of over-dense regions, there seems to be little to no difference on average, suggesting environmental effect of clusters on pitch angle may be limited. Additionally, there appears to be no appreciable difference between the pitch angles of red and blue galaxies at this point in our study. We also plan to look for evidence of variation of pitch angle with cluster age. This work is funded in part by a grant from NASA EPSCoR.

  13. Revealing the Nature of the ULX and X-Ray Population of the Spiral Galaxy NGC 4088

    NASA Astrophysics Data System (ADS)

    Mezcua, M.; Fabbiano, G.; Gladstone, J. C.; Farrell, S. A.; Soria, R.

    2014-04-01

    We present the first Chandra and Swift X-ray study of the spiral galaxy NGC 4088 and its ultraluminous X-ray source (ULX N4088-X1). We also report very long baseline interferometry (VLBI) observations at 1.6 and 5 GHz performed quasi-simultaneously with the Swift and Chandra observations, respectively. Fifteen X-ray sources are detected by Chandra within the D25 ellipse of NGC 4088, from which we derive the X-ray luminosity function (XLF) of this galaxy. We find the XLF is very similar to those of star-forming galaxies and estimate a star-formation rate of 4.5 M ⊙ yr-1. The Chandra detection of the ULX yields its most accurate X-ray position, which is spatially coincident with compact radio emission at 1.6 GHz. The ULX Chandra X-ray luminosity, L 0.2-10.0 keV = 3.4 × 1039 erg s-1, indicates that N4088-X1 could be located at the high-luminosity end of the high-mass X-ray binary (HMXB) population of NGC 4088. The estimates of the black hole (BH) mass and ratio of radio to X-ray luminosity of N4088-X1 rule out a supermassive BH nature. The Swift X-ray spectrum of N4088-X1 is best described by a thermal Comptonization model and presents a statistically significant high-energy cutoff. We conclude that N4088-X1 is most likely a stellar remnant BH in an HMXB, probably fed by Roche lobe overflow, residing in a super-Eddington ultraluminous state. The 1.6 GHz VLBI source is consistent with radio emission from possible ballistic jet ejections in this state.

  14. Revealing the nature of the ULX and X-ray population of the spiral galaxy NGC 4088

    SciTech Connect

    Mezcua, M.; Fabbiano, G.; Gladstone, J. C.; Farrell, S. A.; Soria, R.

    2014-04-20

    We present the first Chandra and Swift X-ray study of the spiral galaxy NGC 4088 and its ultraluminous X-ray source (ULX N4088-X1). We also report very long baseline interferometry (VLBI) observations at 1.6 and 5 GHz performed quasi-simultaneously with the Swift and Chandra observations, respectively. Fifteen X-ray sources are detected by Chandra within the D25 ellipse of NGC 4088, from which we derive the X-ray luminosity function (XLF) of this galaxy. We find the XLF is very similar to those of star-forming galaxies and estimate a star-formation rate of 4.5 M {sub ☉} yr{sup –1}. The Chandra detection of the ULX yields its most accurate X-ray position, which is spatially coincident with compact radio emission at 1.6 GHz. The ULX Chandra X-ray luminosity, L {sub 0.2-10.0} {sub keV} = 3.4 × 10{sup 39} erg s{sup –1}, indicates that N4088-X1 could be located at the high-luminosity end of the high-mass X-ray binary (HMXB) population of NGC 4088. The estimates of the black hole (BH) mass and ratio of radio to X-ray luminosity of N4088-X1 rule out a supermassive BH nature. The Swift X-ray spectrum of N4088-X1 is best described by a thermal Comptonization model and presents a statistically significant high-energy cutoff. We conclude that N4088-X1 is most likely a stellar remnant BH in an HMXB, probably fed by Roche lobe overflow, residing in a super-Eddington ultraluminous state. The 1.6 GHz VLBI source is consistent with radio emission from possible ballistic jet ejections in this state.

  15. A Luminous X-Ray Flare from the Nucleus of the Dormant Bulgeless Spiral Galaxy NGC 247

    NASA Astrophysics Data System (ADS)

    Feng, Hua; Ho, Luis C.; Kaaret, Philip; Tao, Lian; Yamaoka, Kazutaka; Zhang, Shuo; Grisé, Fabien

    2015-07-01

    NGC 247 is a nearby late-type bulgeless spiral galaxy that contains an inactive nucleus. We report a serendipitous discovery of an X-ray flare from the galaxy center with a luminosity of up to 2× {10}39 erg s-1 in the 0.3-10 keV band with XMM-Newton. A Chandra observation confirms that the new X-ray source is spatially coincident with the galaxy nucleus. The XMM-Newton data revealed a hard power-law spectrum with a spectral break near 3-4 keV, no pulsations on timescales longer than 150 ms, and a flat power spectrum consistent with Poisson noise from 1 mHz to nearly 10 Hz. Follow-up observations with Swift detected a second flux peak followed by a luminosity drop by a factor of almost 20. The spectral and temporal behaviors of the nuclear source are consistent with the scenario that the flare was due to an outburst of a low-mass X-ray binary that contains a stellar-mass black hole emitting near its Eddington limit at the peak. However, it cannot be ruled out that the sudden brightening in the nucleus was due to accretion onto a possible low-mass nuclear black hole, fed by a tidally disrupted star or a gas cloud; the Monitor of All-sky X-ray Image observations limit the peak luminosity of the flare to less than ˜ {10}43 erg s-1, suggesting that it is either a low-mass black hole or an inefficient tidal disruption event.

  16. NEAR-INFRARED POLARIMETRY OF A NORMAL SPIRAL GALAXY VIEWED THROUGH THE TAURUS MOLECULAR CLOUD COMPLEX

    SciTech Connect

    Clemens, Dan P.; Cashman, L. R.; Pavel, M. D. E-mail: pavelmi@utexas.edu

    2013-03-15

    Few normal galaxies have been probed using near-infrared polarimetry, even though it reveals magnetic fields in the cool interstellar medium better than either optical or radio polarimetry. Deep H-band (1.6 {mu}m) linear imaging polarimetry toward Taurus serendipitously included the galaxy 2MASX J04412715+2433110 with adequate sensitivity and resolution to map polarization across nearly its full extent. The observations revealed the galaxy to be a steeply inclined ({approx}75 Degree-Sign ) disk type with a diameter, encompassing 90% of the Petrosian flux, of 4.2 kpc at a distance of 53 Mpc. Because the sight line passes through the Taurus Molecular Cloud complex, the foreground polarization needed to be measured and removed. The foreground extinction A{sub V} of 2.00 {+-} 0.10 mag and reddening E(H - K) of 0.125 {+-} 0.009 mag were also assessed and removed, based on analysis of Two Micron All Sky Survey, UKIRT Infrared Deep Sky Survey, Spitzer, and Wide-field Infrared Survey Explorer photometry using the Near-Infrared Color Excess, NICE-Revisited, and Rayleigh-Jeans Color Excess methods. Corrected for the polarized foreground, the galaxy polarization values range from 0% to 3%. The polarizations are dominated by a disk-parallel magnetic field geometry, especially to the northeast, while either a vertical field or single scattering of bulge light produces disk-normal polarizations to the southwest. The multi-kiloparsec coherence of the magnetic field revealed by the infrared polarimetry is in close agreement with short-wavelength radio synchrotron observations of edge-on galaxies, indicating that both cool and warm interstellar media of disk galaxies may be threaded by common magnetic fields.

  17. From star-forming spirals to passive spheroids: integral field spectroscopy of E+A galaxies

    NASA Astrophysics Data System (ADS)

    Swinbank, A. M.; Balogh, M. L.; Bower, R. G.; Zabludoff, A. I.; Lucey, J. R.; McGee, S. L.; Miller, C. J.; Nichol, R. C.

    2012-02-01

    We present three-dimensional spectroscopy of 11 E+A galaxies at z= 0.06-0.12. These galaxies were selected for their strong Hδ absorption but weak (or non-existent) [O II] λ3727 and Hα emission. This selection suggests that a recent burst of star formation was triggered but subsequently abruptly ended. We probe the spatial and spectral properties of both the young (≲1 Gyr) and old (≳few Gyr) stellar populations. Using the Hδ equivalent widths we estimate that the burst masses must have been at least 10 per cent by mass (Mburst≳ 1010 M⊙), which is also consistent with the star formation history inferred from the broad-band spectral energy distributions. On average the A stars cover ˜33 per cent of the galaxy image, extending over 2-15 kpc2, indicating that the characteristic E+A signature is a property of the galaxy as a whole and not due to a heterogeneous mixture of populations. In approximately half of the sample, we find that the A stars, nebular emission and continuum emission are not co-located, suggesting that the newest stars are forming in a different place than those that formed ≲1 Gyr ago, and that recent star formation has occurred in regions distinct from the oldest stellar populations. At least 10 of the galaxies (91 per cent) have dynamics that class them as 'fast rotators' with magnitudes, v/σ, λR and bulge-to-total (B/T) ratio comparable to local, representative ellipticals and S0s. We also find a correlation between the spatial extent of the A stars and the dynamical state of the galaxy such that the fastest rotators tend to have the most compact A star populations, providing new constraints on models that aim to explain the transformation of later type galaxies into early types. Finally, we show that there are no obvious differences between the line extents and kinematics of E+A galaxies detected in the radio (active galactic nucleus, AGN) compared to non-radio sources, suggesting that AGN feedback does not play a dramatic role in

  18. V405 ANDROMEDA REVISITED

    SciTech Connect

    Ribeiro, T.; Kafka, S.

    2011-10-15

    We present a multi-epoch time-resolved high-resolution optical spectroscopy study of the short-period (P{sub orb} = 11.2 hr) eclipsing M0V+M5V RS CVn binary V405 Andromeda. By means of indirect imaging techniques, namely Doppler imaging, we study the surface activity features of the M0V component of the system. A modified version of a Doppler imaging code, which takes into account the tidal distortion of the surface of the star, is applied to the multi-epoch data set in order to provide indirect images of the stellar surface. The multi-epoch surface brightness distributions show a low intensity 'belt' of spots at latitudes {+-}40{sup 0} and a noticeable absence of high latitude features or polar spots on the primary star of V405 Andromeda. They also reveal slow evolution of the spot distribution over {approx}4 yr. An entropy landscape procedure is used in order to find the set of binary parameters that lead to the smoothest surface brightness distributions. As a result, we find M{sub 1} = 0.51 {+-} 0.03 M{sub sun}, M{sub 2} = 0.21 {+-} 0.01 M{sub sun}, R{sub 1} = 0.71 {+-} 0.01 R{sub sun}, and an inclination i = 65{sup 0} {+-} 1{sup 0}. The resulting systemic velocity is distinct for different epochs, raising the possibility of the existence of a third body in the system.

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

    SciTech Connect

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

    2012-07-01

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

  20. In-N-Out: The Gas Cycle from Dwarfs to Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Christensen, Charlotte R.; Davé, Romeel; Governato, Fabio; Pontzen, Andrew; Brooks, Alyson; Munshi, Ferah; Quinn, Thomas; Wadsley, James

    2016-06-01

    We examine the scalings of galactic outflows with halo mass across a suite of 20 high-resolution cosmological zoom galaxy simulations covering halo masses in the range {10}9.5{--}{10}12 {M}ȯ . These simulations self-consistently generate outflows from the available supernova energy in a manner that successfully reproduces key galaxy observables, including the stellar mass–halo mass, Tully–Fisher, and mass–metallicity relations. We quantify the importance of ejective feedback to setting the stellar mass relative to the efficiency of gas accretion and star formation. Ejective feedback is increasingly important as galaxy mass decreases; we find an effective mass loading factor that scales as {v}{{circ}}-2.2, with an amplitude and shape that are invariant with redshift. These scalings are consistent with analytic models for energy-driven wind, based solely on the halo potential. Recycling is common: about half of the outflow mass across all galaxy masses is later reaccreted. The recycling timescale is typically ∼1 Gyr, virtually independent of halo mass. Recycled material is reaccreted farther out in the disk and with typically ∼2–3 times more angular momentum. These results elucidate and quantify how the baryon cycle plausibly regulates star formation and alters the angular momentum distribution of disk material across the halo mass range where most cosmic star formation occurs.

  1. ASASSN-16ek: Discovery of A Probable Supernova in a Bright, Uncatalogued Spiral Galaxy

    NASA Astrophysics Data System (ADS)

    Cruz, I.; Brown, J. S.; Holoien, T. W.-S.; Stanek, K. Z.; Kochanek, C. S.; Godoy-Rivera, D.; Basu, U.; Shappee, B. J.; Prieto, J. L.; Bersier, D.; Dong, Subo; Chen, Ping; Brimacombe, J.; Bock, G.; Conseil, E.; Kiyota, S.; Koff, R. A.; Masi, G.

    2016-04-01

    During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new transient source, most likely a supernova, in the galaxy GALEXASC J072024.60+325058.8.

  2. In-N-Out: The Gas Cycle from Dwarfs to Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Christensen, Charlotte R.; Davé, Romeel; Governato, Fabio; Pontzen, Andrew; Brooks, Alyson; Munshi, Ferah; Quinn, Thomas; Wadsley, James

    2016-06-01

    We examine the scalings of galactic outflows with halo mass across a suite of 20 high-resolution cosmological zoom galaxy simulations covering halo masses in the range {10}9.5{--}{10}12 {M}ȯ . These simulations self-consistently generate outflows from the available supernova energy in a manner that successfully reproduces key galaxy observables, including the stellar mass–halo mass, Tully–Fisher, and mass–metallicity relations. We quantify the importance of ejective feedback to setting the stellar mass relative to the efficiency of gas accretion and star formation. Ejective feedback is increasingly important as galaxy mass decreases; we find an effective mass loading factor that scales as {v}{{circ}}-2.2, with an amplitude and shape that are invariant with redshift. These scalings are consistent with analytic models for energy-driven wind, based solely on the halo potential. Recycling is common: about half of the outflow mass across all galaxy masses is later reaccreted. The recycling timescale is typically ˜1 Gyr, virtually independent of halo mass. Recycled material is reaccreted farther out in the disk and with typically ˜2–3 times more angular momentum. These results elucidate and quantify how the baryon cycle plausibly regulates star formation and alters the angular momentum distribution of disk material across the halo mass range where most cosmic star formation occurs.

  3. The vertical disk structure of the edge-on spiral galaxy NGC 3079

    NASA Technical Reports Server (NTRS)

    Veilleux, S.; Bland-Hawthorn, Jonathan; Cecil, G.; Tully, R. B.

    1993-01-01

    NGC 3079 is an edge-on SB(s)c galaxy at a redshift of 1225 km/s relative to the Local Group. Earlier researchers found a spectacular 'figure-eight' radio structure aligned along the minor axis of the galaxy, centered on the nucleus, and extending 3 kpc above and below the plane. The geometry of this structure and the evidence of unusually high nuclear gas velocities suggest that a wind-type outflow from the nucleus is taking place. The disk of NGC 3079 is also remarkable: it is extremely rich in H 2 regions and is the only unambiguous example of a galaxy outside M31 and our own Galaxy to exhibit 'Heiles-like' shells. Other researchers have also identified a nebulosity with a ragged X-shaped morphology formed by a system of lumpy filaments with individual lengths of 3 - 5 kpc. They suggest that this material is ambient halo gas entrained into the boundary layers of the nuclear outflow. The complex structure of the line emission in NGC 3079 makes this object an ideal target for an imaging spectroscopic study. The present paper reports the preliminary results of such a study.

  4. Evolution of spiral galaxies. 3: Application of the multiphase model to the galactic disk

    NASA Astrophysics Data System (ADS)

    Ferrini, Federico; Molla, Mercedes; Pardi, Maria Chiara; Diaz, Angeles I.

    1994-06-01

    We present an application of the multiphase model of Ferrini and coworkers, developed for the solar neighborhood, to other regions of the disk of the Galaxy in order to reproduce the observed element abundance gradients. The model describes the Galaxy as a two-zone system (halo and disk) sliced into nine cylindrical concentric regions and studies the time evolution of the five populations which inhabit the Milky Way: diffuse gas, molecular clouds, low-mass (m less than 4 M solar masses) and high-mass stars, and stellar remnants. Our final aim is to reproduce the metallicity gradients that are observed in the Milky Way and in other external galaxies. We analyze the evolution of these gradients in time in order to relate their behavior to other galactic quantities such as the star formation rate and the infall rate. The model describes the Galaxy by fitting a large number of observational constraints: abundance gradients, age-metallicity relations for disk and halo, both gas and mass distributions (including radial differences in the characteristic shapes of atomic and molecular gas), and radial distribution and history of star formation rate. The time evolution of abundance gradients is computed, revealing a flattening of gradients with time. In particular, the oxygen abundance was steeper at early times as a consequence of a larger infall. Since the disk is evolving and the gas is consumed, a saturation level is reached in every ring and the gradient will decrease to a minimum value.

  5. A Grand Design Spiral Galaxy with an Interacting Companion: N5194 and N5195

    NASA Technical Reports Server (NTRS)

    Jones, Christine; Petre, Robert (Technical Monitor)

    2000-01-01

    Under the grant we studied the X-ray emission from galaxies, clusters, and gravitational lenses as observed by ROSAT. In addition to several invited and contributed talks presented at conferences, the following papers (listed with their abstracts) that are published in refereed journals were completed as part of this activity.

  6. Andromeda Optical & Infrared Disk Survey: Stellar Populations and Mass Decomposition

    NASA Astrophysics Data System (ADS)

    Sick, Jonathan; Courteau, Stephane; Cuillandre, Jean-Charles; Dalcanton, Julianne; de Jong, Roelof S.; McDonald, Michael; Tully, R. Brent

    2015-01-01

    M31 is ideal for understanding the structure and stellar populations of spiral galaxies thanks to its proximity and our external vantage point. The Andromeda Optical & Infrared Disk Survey (ANDROIDS) has used MegaCam and WIRCam on the Canada-France Hawaii Telescope to map the M31 bulge and disk out to R=40 kpc in ugriJKs bands. Through careful sky monitoring and modelling, ANDROIDS is uniquely able to observe both the resolved stars and integrated spectral energy distributions (SEDs) over M31's entire disk (complimenting HST's PHAT program). By simultaneously fitting stellar populations with isochrones and SED models for M31, we can assess the systematic uncertainties of SED fits to more distant unresolved systems, and constrain the stellar populations that contribute to each bandpass. We pay close attention to the near-IR light of asymptotic giant branch (AGB) stars in stellar population models. ANDROIDS has also surveyed M31 in narrowband TiO and CN bands, enabling a clean classification of Carbon AGB stars, and a mapping the ratio of Carbon and M-type AGB stars (C/M) across the entire disk. The correlation between C/M and stellar metallicity is useful for constraining the NIR colors of more distant galaxies. We also present a hierarchical Bayesian model of pixel-by-pixel stellar populations, yielding the most detailed map of M31's stellar mass and star formation history to date. We find that a full six-band optical-NIR fit provides the best constraints to stellar mass, a triumph for modern NIR stellar population synthesis models, though the results are consistent with an optical-only fits. Fits based on the popular g-i color combination find M/L* ratios biased by 0.1 dex, while color-mass-to-light prescriptions in the literature may differ by 0.3 dex. This result affirms that panchromatic SED modelling is crucial even for stellar mass estimation, let alone age and metallicity. Overall, we estimate the stellar mass of M31, within R=30 kpc, to be 10.3 (+2.3, -1

  7. Midsummer's Dream Galaxies

    NASA Astrophysics Data System (ADS)

    2005-08-01

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

  8. The correlation between far-IR and radio continuum emission from spiral galaxies

    NASA Technical Reports Server (NTRS)

    Dickey, John M.; Garwood, Robert W.; Helou, George

    1987-01-01

    A sample of 30 galaxies selected for their intense IRAS flux at 60 and 100 micron using the Arecibo telescope at 21 cm to measure the continuum and HI line luminosities were observed. The centimeter wave continuum correlates very well with the far-infrared flux, with a correlation coefficient as high as that found for other samples, and the same ratio between FIR and radio luminosities. Weaker correlations are seen between the FIR and optical luminosity and between the FIR and radio continuum. There is very little correlation between the FIR and the HI mass deduced from the integral of the 21 cm line. The strength of the radio continuum correlation suggests that there is little contribution to either the radio and FIR from physical processes not affecting both. If they each reflect time integrals of the star formation rate then the time constants must be similar, or the star formation rate must change slowly in these galaxies.

  9. The DiskMass Survey. VI. Gas and stellar kinematics in spiral galaxies from PPak integral-field spectroscopy

    NASA Astrophysics Data System (ADS)

    Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Bershady, Matthew A.; Schechtman-Rook, Andrew; Andersen, David R.; Swaters, Rob A.

    2013-09-01

    We present ionized-gas ([Oiii]λ5007 Å) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as many as three K-band disk scale lengths (hR). These data have been derived from PPak integral-field-unit spectroscopy from 4980-5370 Å observed at a mean resolution of λ/Δλ = 7700 (σinst = 17 km s-1). These data are a fundamental product of our survey and will be used in companion papers to, e.g., derive the detailed (baryonic+dark) mass budget of each galaxy in our sample. Our presentation provides a comprehensive description of the observing strategy and data reduction, including a robust measurement and removal of shift, scale, and rotation effects in the data due to instrumental flexure. Using an in-plane coordinate system determined by fitting circular-speed curves to our velocity fields, we derive azimuthally averaged rotation curves and line-of-sight velocity dispersion (σLOS) and luminosity profiles for both the stars and [Oiii]-emitting gas. Along with a clear presentation of the data, we demonstrate: (1) The [Oiii] and stellar rotation curves exhibit a clear signature of asymmetric drift with a rotation difference that is 11% of the maximum rotation speed of the galaxy disk, comparable to measurements in the solar neighborhood in the Milky Way. (2) The e-folding length of the stellar velocity dispersion (hσ) is 2hR on average, as expected for a disk with a constant scale height and mass-to-light ratio, with a scatter that is notably smaller for massive, high-surface-brightness disks in the most luminous galaxies. (3) At radii larger than 1.5hR, σLOS tends to decline slower than the best-fitting exponential function, which may be due to an increase in the disk mass-to-light ratio, disk flaring, or disk heating by the dark-matter halo. (4) A strong correlation exists between the central vertical stellar velocity dispersion of the disks (σz,0) and their circular rotational speed at 2.2hR (V2.2h

  10. Gravitational spurs and resonances - Effects of small mass disturbers in spiral galaxy disks

    NASA Technical Reports Server (NTRS)

    Byrd, G. G.; Smith, B. F.; Miller, R. H.

    1984-01-01

    In the present simulations of a disturber in a complete stellar disk without the restrictive assumption, the disturber parameters of the NGC 206 cloud in M 31 were assumed as a realistic example. The resulting spur around the disturber was comparable in shape, size, and strength to Julian and Toomre's (1966) results. In addition, a complicated evolving pattern of strong density peaks appeared well inside and outside the disturber's orbit. Simulation with a ten-times-more-massive disturber showed a more clearly defined version of the same initial pattern, two spiral arms of density peaks rotating with the disturber in the stronger arm. The orbital radii of the density peaks correspond to those of epicyclic resonances with the orbiting disturber potential.

  11. An alternative classical force of gravitation in order to explain the velocity curve of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Guiot, E.

    2015-03-01

    The purpose of this work is to investigate an alternative to modified Newtonian dynamics (MOND), in order to explain the rotation curve of galaxies without dark matter hypothesis, and with respect for classical physics. Our hypothesis is that the force of gravitation, in the case of large distances and under certain conditions, possesses a tangential component. We show that the force of gravitation we obtain is compatible with observational data, such as "flat" curve of rotation and the conic trajectories of the stars.

  12. Spatially extended and high-velocity dispersion molecular component in spiral galaxies: Single-dish versus interferometric observations

    SciTech Connect

    Caldú-Primo, Anahi; Walter, Fabian; Schruba, Andreas; Leroy, Adam; Bolatto, Alberto D.; Vogel, Stuart

    2015-02-01

    Recent studies of the molecular medium in nearby galaxies have provided mounting evidence that the molecular gas can exist in two phases: one that is clumpy and organized as molecular clouds and another one that is more diffuse. This last component has a higher velocity dispersion than the clumpy one. In order to investigate these two molecular components further, we compare the fluxes and line widths of CO in NGC 4736 and NGC 5055, two nearby spiral galaxies for which high-quality interferometric as well as single-dish data sets are available. Our analysis leads to two main results: (1) employing three different methods, we determine the flux recovery of the interferometer as compared to the single-dish to be within a range of 35%–74% for NGC 4736 and 81%–92% for NGC 5055, and (2) when focusing on high (S/N ≥ 5) lines of sight (LOSs), the single-dish line widths are larger by ∼(40 ± 20)% than the ones derived from interferometric data, which is in agreement with stacking all LOSs. These results point to a molecular gas component that is distributed over spatial scales larger than 30″(∼1 kpc), and is therefore filtered out by the interferometer. The available observations do not allow us to distinguish between a truly diffuse gas morphology and a uniform distribution of small clouds that are separated by less than the synthesized beam size (∼3″ or ∼100 pc), as they would both be invisible for the interferometer. This high velocity dispersion component has a dispersion similar to what is found in the atomic medium, as traced through observations of the H i line.

  13. ROSAT HRI and ASCA Observations of the Spiral Galaxy NGC 6946 and its Northeast Complex of Luminous Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Schlegel, E.; Swank, Jean (Technical Monitor)

    2001-01-01

    Analysis of 80 ks ASCA (Advanced Satellite for Cosmology and Astrophysics) and 60 ks ROSAT HRI (High Resolution Image) observations of the face-on spiral galaxy NGC 6946 are presented. The ASCA image is the first observation of this galaxy above approximately 2 keV. Diffuse emission may be present in the inner approximately 4' extending to energies above approximately 2-3 keV. In the HRI data, 14 pointlike sources are detected, the brightest two being a source very close to the nucleus and a source to the northeast that corresponds to a luminous complex of interacting supernova remnants (SNRs). We detect a point source that lies approximately 30" west of the SNR complex but with a luminosity -1115 of the SNR complex. None of the point sources show evidence of strong variability; weak variability would escape our detection. The ASCA spectrum of the SNR complex shows evidence for an emission line at approximately 0.9 keV that could be either Ne IX at approximately 0.915 keV or a blend of ion stages of Fe L-shell emission if the continuum is fitted with a power law. However, a two-component, Raymond-Smith thermal spectrum with no lines gives an equally valid continuum fit and may be more physically plausible given the observed spectrum below 3 keV. Adopting this latter model, we derive a density for the SNR complex of 10-35 cm(exp -3), consistent with estimates inferred from optical emission-line ratios. The complex's extraordinary X-ray luminosity may be related more to the high density of the surrounding medium than to a small but intense interaction region where two of the complex's SNRs are apparently colliding.

  14. First Results from the MADCASH Survey: A Faint Dwarf Galaxy Companion to the Low-mass Spiral Galaxy NGC 2403 at 3.2 Mpc

    NASA Astrophysics Data System (ADS)

    Carlin, Jeffrey L.; Sand, David J.; Price, Paul; Willman, Beth; Karunakaran, Ananthan; Spekkens, Kristine; Bell, Eric F.; Brodie, Jean P.; Crnojević, Denija; Forbes, Duncan A.; Hargis, Jonathan; Kirby, Evan; Lupton, Robert; Peter, Annika H. G.; Romanowsky, Aaron J.; Strader, Jay

    2016-09-01

    We report the discovery of the faintest known dwarf galaxy satellite of a Large Magellanic Cloud (LMC) stellar-mass host beyond the Local Group (LG), based on deep imaging with Subaru/Hyper Suprime-Cam. Magellanic Analog Dwarf Companions And Stellar Halos (MADCASH) J074238+652501-dw lies ∼35 kpc in projection from NGC 2403, a dwarf spiral galaxy at D ≈ 3.2 Mpc. This new dwarf has {M}g=-7.4+/- 0.4 and a half-light radius of 168 ± 70 pc, at the calculated distance of 3.39 ± 0.41 Mpc. The color–magnitude diagram reveals no evidence of young stellar populations, suggesting that MADCASH J074238+652501-dw is an old, metal-poor dwarf similar to low-luminosity dwarfs in the LG. The lack of either detected HI gas ({M}{HI}/{L}V\\lt 0.69 {M}ȯ /{L}ȯ , based on Green Bank Telescope observations) or GALEX NUV/FUV flux enhancement is consistent with a lack of young stars. This is the first result from the MADCASH survey, which is conducting a census of the stellar substructure and faint satellites in the halos of Local Volume LMC analogs via resolved stellar populations. Models predict a total of ∼4–10 satellites at least as massive as MADCASH J074238+652501-dw around a host with the mass of NGC 2403, with 2–3 within our field of view, slightly more than the one such satellite observed in our footprint. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  15. First Results from the MADCASH Survey: A Faint Dwarf Galaxy Companion to the Low-mass Spiral Galaxy NGC 2403 at 3.2 Mpc

    NASA Astrophysics Data System (ADS)

    Carlin, Jeffrey L.; Sand, David J.; Price, Paul; Willman, Beth; Karunakaran, Ananthan; Spekkens, Kristine; Bell, Eric F.; Brodie, Jean P.; Crnojević, Denija; Forbes, Duncan A.; Hargis, Jonathan; Kirby, Evan; Lupton, Robert; Peter, Annika H. G.; Romanowsky, Aaron J.; Strader, Jay

    2016-09-01

    We report the discovery of the faintest known dwarf galaxy satellite of a Large Magellanic Cloud (LMC) stellar-mass host beyond the Local Group (LG), based on deep imaging with Subaru/Hyper Suprime-Cam. Magellanic Analog Dwarf Companions And Stellar Halos (MADCASH) J074238+652501-dw lies ˜35 kpc in projection from NGC 2403, a dwarf spiral galaxy at D ≈ 3.2 Mpc. This new dwarf has {M}g=-7.4+/- 0.4 and a half-light radius of 168 ± 70 pc, at the calculated distance of 3.39 ± 0.41 Mpc. The color–magnitude diagram reveals no evidence of young stellar populations, suggesting that MADCASH J074238+652501-dw is an old, metal-poor dwarf similar to low-luminosity dwarfs in the LG. The lack of either detected HI gas ({M}{HI}/{L}V\\lt 0.69 {M}ȯ /{L}ȯ , based on Green Bank Telescope observations) or GALEX NUV/FUV flux enhancement is consistent with a lack of young stars. This is the first result from the MADCASH survey, which is conducting a census of the stellar substructure and faint satellites in the halos of Local Volume LMC analogs via resolved stellar populations. Models predict a total of ˜4–10 satellites at least as massive as MADCASH J074238+652501-dw around a host with the mass of NGC 2403, with 2–3 within our field of view, slightly more than the one such satellite observed in our footprint. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  16. OUTFLOW VERSUS INFALL IN SPIRAL GALAXIES: METAL ABSORPTION IN THE HALO OF NGC 891

    SciTech Connect

    Bregman, Joel N.; Seitzer, Patrick; Cowley, C. R.; Miller, Matthew J.; Miller, Eric D.

    2013-03-20

    Gas accreting onto a galaxy will be of low metallicity while halo gas due to a galactic fountain will be of near-solar metallicity. We test these predictions by measuring the metal absorption line properties of halo gas 5 kpc above the plane of the edge-on galaxy NGC 891, using observations taken with HST/STIS toward a bright background quasar. Metal absorption lines of Fe II, Mg II, and Mg I in the halo of NGC 891 are clearly seen, and when combined with recent deep H I observations, we are able to place constraints on the metallicity of the halo gas for the first time. The H I line width defines the line broadening, from which we model opacity effects in these metal lines, assuming that the absorbing gas is continuously distributed in the halo. The gas-phase metallicities are [Fe/H] = -1.18 {+-} 0.07 and [Mg/H] = -0.23 + 0.36/ - 0.27 (statistical errors) and this difference is probably due to differential depletion onto grains. When corrected for such depletion using Galactic gas as a guide, both elements have approximately solar or even supersolar abundances. This suggests that the gas is from the galaxy disk, probably expelled into the halo by a galactic fountain, rather than from accretion of intergalactic gas, which would have a low metallicity. The abundances would be raised by significant amounts if the absorbing gas lies in a few clouds with thermal widths smaller than the rotational velocity of the halo. If this is the case, both the abundances and [Mg/Fe] would be supersolar.

  17. THE LINK BETWEEN LIGHT AND MASS IN LATE-TYPE SPIRAL GALAXY DISKS

    SciTech Connect

    Swaters, Robert A.; Bershady, Matthew A.; Martinsson, Thomas P. K.; Westfall, Kyle B.; Andersen, David R.; Verheijen, Marc A. W.

    2014-12-20

    We present the correlation between the extrapolated central disk surface brightness (μ) and extrapolated central surface mass density (Σ) for galaxies in the DiskMass sample. This μ-Σ relation has a small scatter of 30% at the high surface brightness (HSB) end. At the low surface brightness (LSB) end, galaxies fall above the μ-Σ relation, which we attribute to their higher dark matter content. After correcting for the dark matter as well as for the contribution of gas and the effects of radial gradients in the disk, the LSB end falls back on the linear μ-Σ relation. The resulting scatter around the corrected μ-Σ relation is 25% at the HSB end and about 50% at the LSB end. The intrinsic scatter in the μ-Σ relation is estimated to be 10%-20%. Thus, if μ {sub K,} {sub 0} is known, the stellar surface mass density is known to within 10%-20% (random error). Assuming disks have an exponential vertical distribution of mass, the average Υ{sub ∗}{sup K} is 0.24 M {sub ☉}/L {sub ☉}, with an intrinsic scatter around the mean of at most 0.05 M {sub ☉}/L {sub ☉}. This value for Υ{sub ∗}{sup K} is 20% smaller than we found in Martinsson et al., mainly due to the correction for dark matter applied here. This small scatter means that among the galaxies in our sample, variations in scale height, vertical density profile shape, and/or the ratio of vertical over radial velocity dispersion must be small.

  18. Precision Velocity Fields in Spiral Galaxies. I. Noncircular Motions and rms Noise in Disks

    NASA Astrophysics Data System (ADS)

    Beauvais, Charles; Bothun, G.

    1999-11-01

    Investigation of the symmetry of the major- and minor-axis rotation curves reveals strong evidence of nonconcentric gas orbits with the maximum center shift of ~300 pc. Comparisons between kinematic and photometric structure (e.g., position angles, inclinations, centers) show considerable noise on small scales. Although large-scale averages are in agreement, this noise is a matter of some concern in the application of the Tully-Fisher method to disk galaxies. Moreover, cases of significant misalignment in position angle between the inner and outer disks are seen in two of the sample galaxies and may indicate the transition between luminous and dark-matter-dominated regions (i.e., where the maximum-disk hypothesis begins to fail). The kinematic disk models are used to find the residual velocity fields, and typical residuals are found to be 10-15 km s-1 over regions 0.5-1.5 kpc in diameter. Correlations are shown to exist between the residual velocity fields and both the Hα intensity and the velocity dispersion images. This suggests that kinematic feedback to the gas from star formation is an important source of noncircular motion. However, the relative quiescence of the large-scale velocity field indicates that the effect does not cause a significant deviation from circular symmetry, kinematically indicating that star formation is not a hidden parameter in the Tully-Fisher relation. Finally, the residual velocity fields are examined for signs of noncircular orbits by looking for azimuthal angular harmonics that would be present if disk galaxies are embedded in a triaxial dark matter potential. For our sample we find the ellipticity of the gas orbits to be <~0.08, which implies the potential is relatively round. This is consistent with disks being maximal.