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Sample records for spiral galaxy m83

  1. spiral galaxy M83

    NASA Image and Video Library

    2017-09-27

    JANUARY 9, 2014: The vibrant magentas and blues in this Hubble image of the barred spiral galaxy M83 reveal that the galaxy is ablaze with star formation. The galactic panorama unveils a tapestry of the drama of stellar birth and death. The galaxy, also known as the Southern Pinwheel, lies 15 million light-years away in the constellation Hydra. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) Acknowledgement: W. Blair (STScI/Johns Hopkins University) and R. O'Connell (University of Virginia) NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  2. Southern Pinwheel Galaxy M83

    NASA Image and Video Library

    2005-05-05

    Ultraviolet images such as this one from NASA's Galaxy Evolution Explorer suggest the M83 has unusual pockets of star formation separated by large distances from the spiral arms in the main disk of the galaxy. http://photojournal.jpl.nasa.gov/catalog/PIA07903

  3. High-Velocity Clouds in the Nearby Spiral Galaxy M 83

    NASA Astrophysics Data System (ADS)

    Miller, Eric D.; Bregman, Joel N.; Wakker, Bart P.

    2009-02-01

    We present deep H I 21 cm and optical observations of the face-on spiral galaxy M 83 obtained as part of a project to search for high-velocity clouds (HVCs) in nearby galaxies. Anomalous-velocity neutral gas is detected toward M 83, with 5.6 × 107 M sun of H I contained in a disk rotating 40-50 km s-1 more slowly in projection than the bulk of the gas. We interpret this as a vertically extended thick disk of neutral material, containing 5.5% of the total H I within the central 8 kpc. Using an automated source detection algorithm to search for small-scale H I emission features, we find eight distinct, anomalous-velocity H I clouds with masses ranging from 7 × 105 to 1.5 × 107 M sun and velocities differing by up to 200 km s-1 compared to the H I disk. Large on-disk structures are coincident with the optical spiral arms, while unresolved off-disk clouds contain no diffuse optical emission down to a limit of 27 r' mag per square arcsec. The diversity of the thick H I disk and larger clouds suggests the influence of multiple formation mechanisms, with a galactic fountain responsible for the slowly rotating disk and on-disk discrete clouds, and tidal effects responsible for off-disk cloud production. The mass and kinetic energy of the H I clouds are consistent with the mass exchange rate predicted by the galactic fountain model. If the HVC population in M 83 is similar to that in our own Galaxy, then the Galactic HVCs must be distributed within a radius of less than 25 kpc.

  4. Magnetic and gaseous spiral arms in M83

    NASA Astrophysics Data System (ADS)

    Frick, P.; Stepanov, R.; Beck, R.; Sokoloff, D.; Shukurov, A.; Ehle, M.; Lundgren, A.

    2016-01-01

    Context. The magnetic field configurations in several nearby spiral galaxies contain magnetic arms that are sometimes located between the material arms. The nearby barred galaxy M83 provides an outstanding example of a spiral pattern seen in tracers of gas and magnetic field. Aims: We analyse the spatial distribution of magnetic fields in M83 and their relation to the material spiral arms. Methods: Isotropic and anisotropic wavelet transforms are used to decompose the images of M83 in various tracers to quantify structures in a range of scales from 0.2 to 10 kpc. We used radio polarization observations at λ6.2 cm and λ13 cm obtained with the VLA, Effelsberg and ATCA telescopes and APEX sub-mm observations at 870 μm, which are first published here, together with maps of the emission of warm dust, ionized gas, molecular gas, and atomic gas. Results: The spatial power spectra are similar for the tracers of dust, gas, and total magnetic field, while the spectra of the ordered magnetic field are significantly different. As a consequence, the wavelet cross-correlation between all material tracers and total magnetic field is high, while the structures of the ordered magnetic field are poorly correlated with those of other tracers. The magnetic field configuration in M83 contains pronounced magnetic arms. Some of them are displaced from the corresponding material arms, while others overlap with the material arms. The pitch angles of the magnetic and material spiral structures are generally similar. The magnetic field vectors at λ6.2 cm are aligned with the outer material arms, while significant deviations occur in the inner arms and, in particular, in the bar region, possibly due to non-axisymmetric gas flows. Outside the bar region, the typical pitch angles of the material and magnetic spiral arms are very close to each other at about 10°. The typical pitch angle of the magnetic field vectors is about 20° larger than that of the material spiral arms. Conclusions

  5. A Deep Chandra Legacy Observation of the Nearby Grand Design Spiral M83

    NASA Astrophysics Data System (ADS)

    Long, Knox S.; Bianchi, L.; Blair, W. P.; Ghavamian, P.; Kuntz, K. D.; Plucinsky, P. P.; Soria, R.; Winkler, P. F.

    2011-05-01

    With a high supernova rate, a starburst nucleus, and large numbers of high mass star clusters in the disk of the galaxy, M83 is a superb laboratory for understanding how the life cycle of stars and the interstellar medium interact to produce X-ray emission in normal galaxies. Here we report initial results of a set of ongoing deep Chandra ACIS observations of M83 that will ultimately have a total exposure of 750 ks. Our preliminary catalog, based on the first 160 ks of data, includes more than 180 sources, a number that will likely grow by a factor of 2 when the observations are complete. New sources include a new ultraluminous X-ray source that has appeared in an interarm region since the earlier Chandra observations in 2001, as well as the X-ray counterpart to the SN 1957D. Many of the sources are coincident with supernova remnant candidates identified from new interference filter images of M83 from Magellan/IMACS. We will discuss how we intend to relate the X-ray properties of the supernova remnants, X-ray binaries, and diffuse X-ray emission to the local environment, using the underlying stellar populations and/or distance from features like the spiral arms to constrain the progenitors of the sources. We gratefully acknowledge support for this project by NASA through grant GO1-12115A.

  6. Velocity fields in late-type galaxies from H-alpha Fabry-Perot interferometry. IV - Kinematics and dynamics of the SAB(s) spiral NGC 5236 (M83)

    NASA Astrophysics Data System (ADS)

    de Vaucouleurs, G.; Pence, W. D.; Davoust, E.

    1983-09-01

    The velocity field in the weakly barred spiral NGC 5236=M83, type SAB(s)c, MOT(B) = - 20.00, at a distance δ = 3.7 Mpc in the Centaurus group, is derived from 2770 velocities measured on 16 Hα Fabry-Perot interferograms taken with the Galaxymeter attached to the 205 cm reflector of McDonald Observatory. A contour map of Ha emission intensity and a catalog of 60 bright H II regions derived from the photometry of Talbot, Jensen, and Dufour are also presented. Isovelocity maps at 12", 15", and 21" resolution are used to analyze the velocity field within 3'.6 = 3.8 kpc from the center. With an assumed inclination i = 24° (from the axis ratio), the position angle of the line of nodes is θ0 = 43°, in approximate agreement with available photometry. There is little or no indication of a warping of the disk within 3.8 kpc from the center. The systemic velocity is VS = 509±2 km s-1. The mean maximum rotational velocity VM = 205 km s-1s probably reached near RM ≍ 5' =5.4 kpc. The masses estimated by fitting the observed mean rotation curve to various conventional axisymmetric mass distribution models-neglecting velocity dispersion-are in the range 5.8 ≤ sunT ≤ 14.6 × 1010 solar units. A more satisfactory fit in better agreement with the photometry is obtained with a two-component generalized Toomre model with a "hot" bulge. The best-fit model has a total mass sunT = (1.00±0.05) × 1011 solar masses of which 4% is in the spheroid. The calculated velocity dispersion at the center σr = 78 ± 10: km s-1 in fair agreement with the value (103) predicted by a revised version of the Faber-Jackson (L ∝ σ4) relation for the absolute magnitude (-17.50) of the bulge. The mass-luminosity ratio, corrected for galactic and internal extinction, is f0(B) ≍ 7; it is 2.7 for the bulge component and ˜7 for the disk component. A map of the ()- C velocity residuals discloses systematic departures attributable to streaming motions of the gas around the bar and perturbations

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  8. Dark vs. luminous matter in the CenA/M83 galaxy complex

    NASA Astrophysics Data System (ADS)

    Karachentsev, Igor

    2004-07-01

    The distribution of dark vs. luminous matter on scales of 0.1-1.0 Mpc remains poorly understood. For a nearby group, the total mass can be determined from the radius of "the zero-velocity surface", which separates the group from the general Hubble flow. This new method requires the measurement of accurate distances and radial velocities of galaxies around the group, but gives total mass estimates independent of assumptions about the state of relaxation or orbital characteristics. The mass pertains to the group at the full scale to which it is bound. Upon application in several nearest groups, the method yields mass estimates in agreement with the sum of the virial masses of subcomponents. However, the typical total M/L ratio for the nearby groups of ~30 Mo/Lo implies a local mean density of matter which is only 1/7 the canonical global density . The nearby complex of galaxies around Cen A and M83 resembles our Local Group by the dumb-bell concentration of objects around a pair of dominant galaxies. Accurate distances have been acquired recently for ~20 group members by the TRGB method using HST. We will measure TRGB distances to the 17 remaining galaxies in the region. These observations will constrain the dynamical state of the halo surrounding the nearest giant E-galaxy Cen A, providing a comparison with the halos of the nearest spirals.

  9. VizieR Online Data Catalog: M83 magnetic and gaseous spiral arms images (Frick+, 2016)

    NASA Astrophysics Data System (ADS)

    Frick, P.; Stepanov, R.; Beck, R.; Sokoloff, D.; Shukurov, A.; Ehle, M.; Lundgren, A.

    2016-02-01

    We performed radio continuum observations of M83 with the Australia Telescope Compact Array (ATCA), consisting of six parabolic dishes, each of 22m in diameter, forming an east-west radio interferometer. We observed M83 with different baseline configurations, each observation session lasting 12h to achieve maximum uv coverage. (2 data files).

  10. 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.

  11. Outskirts of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Bresolin, Fabio

    2017-03-01

    I present an overview of the recent star formation activity in the outer disks of spiral galaxies, from the observational standpoint, with emphasis on the gas content, the star formation law, the metallicity and the stellar populations.

  12. SUPERLUMINOUS SPIRAL GALAXIES

    SciTech Connect

    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 L{sub r} = 8–14L* (4.3–7.5 × 10{sup 44} erg s{sup −1}). These super spiral galaxies are also giant and massive, with diameter D = 57–134 kpc and stellar mass M{sub stars} = 0.3–3.4 × 10{sup 11}M{sub ⊙}. We find 53 super spirals out of a complete sample of 1616 SDSS galaxies with redshift z < 0.3 and L{sub r} > 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{sub ⊙} yr{sup −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.

  13. 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

  14. 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.

  15. Chandra Observatory Reveals Spiral Galaxy's Boisterous Activity

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This Chandra X-ray observatory image of M83 shows numerous point-like neutron stars and black hole x-ray sources scattered throughout the disk of this spiral galaxy. The bright nuclear region of the galaxy glows prominently due to a burst of star formation that is estimated to have begun about 20 million years ago in the galaxy's time frame. The nuclear region, enveloped by a 7 million degree Celsius gas cloud of carbon, neon, magnesium, silicon, and sulfur atoms, contains a much higher concentration of neutron stars and black holes than the rest of the galaxy. Hot gas with a slightly lower temperature of 4 million degrees observed along the spiral arms of the galaxy suggests that star formation in this region may be occurring at a more sedate rate.

  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. 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

  18. Barred Spiral Galaxy

    NASA Image and Video Library

    2017-09-27

    Barred Spiral Galaxy NGC 1300 Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA) Acknowledgment: P. Knezek (WIYN) The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute conducts Hubble science operations. Goddard is responsible for HST project management, including mission and science operations, servicing missions, and all associated development activities. To learn more about the Hubble Space Telescope go here: www.nasa.gov/mission_pages/hubble/main/index.html

  19. Satellites of spiral galaxies

    NASA Technical Reports Server (NTRS)

    Zaritsky, Dennis; Smith, Rodney; Frenk, Carlos; White, Simon D. M.

    1993-01-01

    We present a survey of satellites around a homogeneous set of late-type spirals with luminosity similar to that of the Milky Way. On average, we find fewer than 1.5 satellites per primary, but we argue that we can treat the survey as an ensemble and so derive the properties of the halo of a 'typical' isolated spiral. The projected density profile of the ensemble falls off approximately as 1/r. Within 50 kpc the azimuthal distribution of satellites shows some evidence for the 'Holmberg effect', an excess near the minor axis of the primary; however, at larger projected distances, the distribution appears isotropic. There is a weak but significant correlation between the size of a satellite and its distance from its primary, as expected if satellites are tidally truncated. Neither Hubble type nor spectral characteristics correlate with apparent separation. The ensemble of satellites appears to be rotating at about 30 km/s in the same direction as the galactic disk. Satellites on prograde orbits tend to be brighter than those on retrograde orbits. The typical velocity difference between a satellite and its primary shows no clear dependence either on apparent separation, or on the rotation speed of the primary. Thus our survey demonstrates that isolated spiral galaxies have massive halos that extend to many optical radii.

  20. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    2015-12-01

    Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 \\upmu G) and in central starburst regions (50-100 \\upmu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 \\upmu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.—Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edge-on galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young galaxies and their dynamical importance during galaxy evolution, will be studied with

  1. Collision Between Two Spiral Galaxies

    NASA Image and Video Library

    2008-04-24

    NGC 6050/IC 1179 Arp 272 is a remarkable collision between two spiral galaxies, NGC 6050 and IC 1179, and is part of the Hercules Galaxy Cluster, located in the constellation of Hercules. This image is from NASA Hubble Space Telescope.

  2. 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

  3. How Opaque Are Spiral Galaxies?

    NASA Astrophysics Data System (ADS)

    Allen, Ronald

    1999-07-01

    Using HST Archival images in a previous modest AR program, we have developed a new method to calibrate the effects of crowding and confusion from foreground structure on the counts of background galaxies seen through a foreground system. This new method, the Synthetic Field Method, permits us to establish the area-averaged amount of extinction through the entire thickness of the foreground galaxy. No assumptions about the spatial distribution of the obscuring material in the foreground system or about its reddening law are required. We now propose to exploit this method by applying it to deep Archival images of all 17 nearby spiral galaxies obtained earlier with the HST/WFPC2 in the Cepheid distance scale programs. Applying the method to this large sample of spirals will permit us: {1} to decrease the fundamental uncertainty in our results owing to field-to-field variations in the surface number density of the background galaxies, and {2} to begin quantifying the differences in extinction between arms and inter-arm regions, and between the inner and outer parts of spiral galaxy disks. The results of this project will provide the largest study to date of TOTAL extinction in spiral galaxies using background illuminating objects.

  4. 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

  5. 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

  6. More Satellites of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Zaritsky, Dennis; Smith, Rodney; Frenk, Carlos; White, Simon D. M.

    1997-03-01

    We present a revised and expanded catalog of satellite galaxies of a set of isolated spiral galaxies similar in luminosity to the Milky Way. This sample of 115 satellites, 69 of which were discovered in our multifiber redshift survey, is used to probe the results obtained from the original sample further (Zaritsky et al.). The satellites are, by definition, at projected separations <~500 kpc, have absolute recessional velocity differences with respect to the parent spiral of less than 500 km s-1, and are at least 2.2 mag fainter than their associated primary galaxy. A key characteristic of this survey is the strict isolation of these systems, which simplifies any dynamical analysis. We find no evidence for a decrease in the velocity dispersion of the satellite system as a function of radius out to galactocentric radii of 400 kpc, which suggests that the halo extends well beyond 200 kpc. Furthermore, the new sample affirms our previous conclusions (Zaritsky et al.) that (1) the velocity difference between a satellite and its primary is not strongly correlated with the rotation speed of the primary, (2) the system of satellites has a slight net rotation (34 +/- 14 km s-1) in the same sense as the primary's disk, and (3) that the halo mass of an ~L* spiral galaxy is in excess of 2 × 1012 M⊙. Lick Observatory Bulletin B1346.

  7. The (C II) 158 micron line mapping of spiral galaxies

    NASA Technical Reports Server (NTRS)

    Stacey, Gordon J.; Geis, N.; Genzel, Reinhard; Jackson, J. M.; Poglitsch, Albrecht; Townes, Charles H.

    1990-01-01

    Large scale maps of the face of spiral galaxies M51, M83, and NGC 6946 in the 158 micron (C II) fine structure line. The maps are obtained from the Far-infrared Imaging Fabry-Perot Interferometer (FIFI) during its first series of flights on board the Kuiper Airborne Observatory. The (C II) line emission is ubiquitous and easily traced over the mapped regions of each of the galaxies. The (C II) maps are compared with those obtained with similar sized beams in the CO line. The data available from these maps is interpreted.

  8. Molecular gas temperature and density in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Wall, W. F.; Jaffe, D. T.; Bash, F. N.; Israel, F. P.; Maloney, P. R.; Baas, F.

    1993-01-01

    We combine beam-matched CO-13, CO-12 J = 3 yields 2 and J = 2 yields 1 line data to infer the molecular gas excitation conditions in the central 500 to 1600 pc diameters of a small sample of infrared-bright external galaxies: NGC253, IC342, M 83, Maffei 2, and NGC6946. Additional observations of the J = 1 yields 0 lines of C-18O and CO-13 set limits on the opacity of the CO-13 J = 1 yields 0 line averaged over the central kiloparsec of these spiral galaxies.

  9. NGC 6090 - a Pair of Spiral Galaxies

    NASA Image and Video Library

    2008-04-24

    NGC 6090 is a beautiful pair of spiral galaxies with an overlapping central region and two long tidal tails formed from material ripped out of the galaxies by gravitational interaction. This image is from NASA Hubble Space Telescope.

  10. 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

  11. 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

  12. Large Face on Spiral Galaxy NGC 3344

    NASA Image and Video Library

    2005-05-05

    This ultraviolet image from NASA Galaxy Evolution Explorer is of the large face on spiral galaxy NGC 3344. The inner spiral arms are wrapped so tightly that they are difficult to distinguish. http://photojournal.jpl.nasa.gov/catalog/PIA07904

  13. 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.

  14. Outer spiral structure in disk galaxies

    NASA Astrophysics Data System (ADS)

    Patsis, P. A.

    2017-03-01

    In several grand design barred-spiral galaxies it is observed a second, fainter, outer set of spiral arms. Typical examples of objects of this morphology can be considered NGC 1566 and NGC 5248. I suggest that such an overall structure can be the result of two dynamical mechanisms acting in the disc. The bar and both spiral systems rotate with the same pattern speed. The inner spiral is reinforced by regular orbits trapped around the stable, elliptical, periodic orbits of the central family, while the outer system of spiral arms is supported by chaotic orbits. Chaotic orbits are also responsible for a rhomboidal area surrounding the inner barred-spiral region. In general there is a discontinuity between the two spiral structures at the corotation region.

  15. Nonresonance Spiral Responses in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Polyachenko, V. L.; Polyachenko, E. V.

    2002-01-01

    The behavior of the gravitational potential outside the region where the main spiral arms of galaxies are located is investigated. The characteristic features of this behavior include nearly circular extensions of the main arms, which typically have an angular extent of 90°. It is natural to interpret these quarter-turn spirals as the response of the galactic disk to the gravitational potential of the main spiral arms. The theoretical models are supported by observational data for the brightness distributions in both normal (NGC 3631) and barred (NGC 1365) galaxies.

  16. Identifying Hidden Supernova Remnants in M83 with the VLA

    NASA Astrophysics Data System (ADS)

    Cole, Bradley; Stockdale, Christopher; Blair, William P.; Cowan, John J.; Godfrey, Leith; Kuntz, K. D.; Long, Knox S.; Maddox, Larry A.; Plucinsky, Paul P.; Pritchard, Tyler A.; Soria, Roberto; Whitmore, Bradley C.; Winkler, P. Frank

    2017-01-01

    We present results of our analysis of C and L band observations of the grand design spiral galaxy, M83 made with the Karl G. Jansky Very Large Array (VLA). With recent optical (HST) and X-ray (Chandra) observations and utilizing the newly expanded bandwidth of the VLA, we are exploring the radio spectral properties of the historical radio point sources in M83 and have discovered more than 250 discrete radio sources. These observations allow us to probe the evolution of supernova remnants (SNRs) and to find previously undiscovered SNRs. These observations represent the fourth epoch of deep VLA observations of M83. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities.

  17. Kiloparsec-scale molecular gas excitation in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Wall, W. F.; Jaffe, D. T.; Bash, F. N.; Israel, F. P.; Maloney, P. R.; Baas, F.

    1993-09-01

    We combine beam-matched (C-13)O, (C-12)O J = 3 - 2 and J = 2 - 1 line data to infer the molecular gas excitation conditions in the central 500 to 1600 pc diameters of a small sample of IR-bright external galaxies: NGC 253, IC 342, M83, Maffei 2, and NGC 6946. We find that the central 170 to 530 pc diameter regions have typical molecular gas densities ranging from approximately less than 10,000/cu cm (in M83) to approximately greater than 100,000/cu cm (in NGC 253) and that, outside of these regions, the densities are likely to be approximately less than 10,000/cu cm. The molecular clouds outside the inner 170-530 pc are at least as warm as the molecular clouds in our Galaxy. Column densities derived from integrated (C-13)O line strengths and H-alpha surface brightnesses suggest that the star formation rate is enhanced in the central 170-530 pc diameters by an order of magnitude over that inferred for the outer star-forming disks in spiral galaxies.

  18. Kiloparsec-scale molecular gas excitation in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Wall, W. F.; Jaffe, D. T.; Bash, F. N.; Israel, F. P.; Maloney, P. R.; Baas, F.

    1993-01-01

    We combine beam-matched (C-13)O, (C-12)O J = 3 - 2 and J = 2 - 1 line data to infer the molecular gas excitation conditions in the central 500 to 1600 pc diameters of a small sample of IR-bright external galaxies: NGC 253, IC 342, M83, Maffei 2, and NGC 6946. We find that the central 170 to 530 pc diameter regions have typical molecular gas densities ranging from approximately less than 10,000/cu cm (in M83) to approximately greater than 100,000/cu cm (in NGC 253) and that, outside of these regions, the densities are likely to be approximately less than 10,000/cu cm. The molecular clouds outside the inner 170-530 pc are at least as warm as the molecular clouds in our Galaxy. Column densities derived from integrated (C-13)O line strengths and H-alpha surface brightnesses suggest that the star formation rate is enhanced in the central 170-530 pc diameters by an order of magnitude over that inferred for the outer star-forming disks in spiral galaxies.

  19. The Spiral Structure of AGN Host Galaxies

    NASA Astrophysics Data System (ADS)

    Kennefick, J.; Barrows, R. S.; Hughes, J. A.; Schilling, A.; Davis, B.; Shields, D.; Madey, A.; Kennefick, D.; Lacy, C.; Seigar, M.

    2014-03-01

    Recent work has uncovered a correlation between the black hole mass, M, in the centers of local spiral galaxies and the pitch angles, P, of their spiral arms. We propose to test this M-P correlation at moderate to high redshifts, using a sample of active galaxies selected from the Great Observatories Origins Survey and the Sloan Digital Sky Survey showing evidence for spiral structure in their host galaxies. The mass of the central black holes are estimated using the Hβ or Mg II lines in existing spectra using luminosity-radius scaling relations. Pitch angles are measured using an iterative 2D FFT algorithm. The aim is to establish this M-P relation beyond our local epoch, test for evolution in its form, and eventually to compute a BH mass function for late-type galaxies out to moderate redshifts.

  20. 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.

  1. Red Supergiants as Cosmic Abundance Probes: Massive Star Clusters in M83 and the Mass–Metallicity Relation of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Davies, Ben; Kudritzki, Rolf-Peter; Lardo, Carmela; Bergemann, Maria; Beasor, Emma; Plez, Bertrand; Evans, Chris; Bastian, Nate; Patrick, Lee R.

    2017-10-01

    We present an abundance analysis of seven super star clusters in the disk of M83. The near-infrared spectra of these clusters are dominated by red supergiants, and the spectral similarity in the J-band of such stars at uniform metallicity means that the integrated light from the clusters may be analyzed using the same tools as those applied to single stars. Using data from VLT/KMOS, we estimate metallicities for each cluster in the sample. We find that the abundance gradient in the inner regions of M83 is flat, with a central metallicity of [Z]=0.21+/- 0.11 relative to a solar value of Z ⊙ = 0.014, which is in excellent agreement with the results from an analysis of luminous hot stars in the same regions. Compiling this latest study with our other recent work, we construct a mass–metallicity relation for nearby galaxies based entirely on the analysis of RSGs. We find excellent agreement with the other stellar-based technique—that of blue supergiants—as well as with temperature-sensitive (“auroral” or “direct”) H ii-region studies. Of all the H ii-region strong-line calibrations, those that are empirically calibrated to direct-method studies (N2 and O3N2) provide the most consistent results.

  2. Pitch angle variations in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Savchenko, S. S.; Reshetnikov, V. P.

    2013-12-01

    We present a detailed photometric study and measurements of spiral arm pitch angles for a sample of 50 non-barred or weakly barred grand-design spiral galaxies selected from Sloan Digital Sky Survey. In order to find pitch angles, we used a new method based on the window Fourier analysis of their images. This method allows us not only to infer the average pitch angle, but to obtain its value as a function of galactocentric radius as well. Our main results are as follows: (1) Spiral arms of most galaxies cannot be described by a single value of the pitch angle. About 2/3 of galaxies demonstrate pitch angle variations exceeding 20 per cent. In most galaxies in the sample their pitch angle decreases by increasing the distance from the centre. (2) Pitch angle variations correlate with the properties of galaxies - with the shape of the surface brightness distribution (envelope-type or truncated disc), and with the sign of stellar disc colour gradient. (3) More luminous and bright bulges produce more tightly wound spiral arms, that is in agreement with current models for spiral arms formation.

  3. Pitch Angle Survey of GOODS Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Boe, Benjamin; Kennefick, Daniel; Arkansas Galaxy Evolution Survey, Arkansas CenterSpace; Planetary Sciences

    2015-01-01

    This research looks at how the pitch angles of galaxies change over scales of cosmic time. We measure the pitch angle, or tightness of spiral winding, using a new code, Spirality. We then compare the results to those obtained from established software, 2DFFT (2 Dimensional Fast Fourier Transform). We investigate any correlation between pitch angle and redshift, or distance from Earth. Previous research indicates that the pitch angle of a galaxy correlates with its central bulge mass and the mass of its central black hole. Thus any evolution in the distribution of pitch angles could ultimately prove to be indicative of evolution in the supermassive black hole mass function. Galaxies from the Hubble GOODS (Great Observatories Origins Deep Survey) North and South were measured. We found that there was strong agreement between Spirality and 2DFFT measurements. Spirality measured the pitch angle of the GOODS galaxies with a lower error than 2DFFT on average. With both software a correlation between pitch angle and redshift was found. Spirality observed a 6.150 increase in pitch per unit redshift. The increase in pitch angle with redshift suggests that in the past galaxies had higher pitch angles, which could be indicative of lower central black hole masses (or, more directly, central bulge masses).

  4. Hubble Sees Galaxies Spiraling around Leo

    NASA Image and Video Library

    2017-09-27

    Shown here is a spiral galaxy known as NGC 3455, which lies some 65 million light-years away from us in the constellation of Leo (the Lion). Galaxies are classified into different types according to their structure and appearance. This classification system is known as the Hubble Sequence, named after its creator Edwin Hubble. In this image released 14, April, 2014, NGC 3455 is known as a type SB galaxy — a barred spiral. Barred spiral galaxies account for approximately two thirds of all spirals. Galaxies of this type appear to have a bar of stars slicing through the bulge of stars at their center. The SB classification is further sub-divided by the appearance of a galaxy's pinwheeling spiral arms; SBa types have more tightly wound arms, whereas SBc types have looser ones. SBb types, such as NGC 3455, lie in between. NGC 3455 is part of a pair of galaxies — its partner, NGC 3454, lies out of frame. This cosmic duo belong to a group known as the NGC 3370 group, which is in turn one of the Leo II groups, a large collection of galaxies scattered some 30 million light-years to the right of the Virgo cluster. This image is from Hubble's Advanced Camera for Surveys. Credit: ESA/Hubble & NASA, Acknowledgement: Nick Rose NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  5. Thickness determination of three-dimensional spiral galaxies.

    NASA Astrophysics Data System (ADS)

    Zhao, Shanghui; Bao, Mengxian; Zhang, Wenyuan; Peng, Qiuhe

    1992-12-01

    CCD images of some spiral galaxies were obtained with the 1-m telescope of Yunnan Observatory. After processing and measuring the images, the authors get the morphological parameters, thickness and their relative errors of seven spiral galaxies (NGC 2608, NGC 2713, NGC 2776, NGC 3631, NGC 5669, NGC 5985 and NGC 7156) by fitting their spiral arms with logarithmic spirals.

  6. Precision distances with spiral galaxy apparent diameters

    NASA Astrophysics Data System (ADS)

    Steer, Ian

    2016-01-01

    Spiral galaxy diameters offer the oldest extragalactic distance indicator known. Although outdated and hitherto imprecise, two spiral diameter-based distance indicators applied in the 1980s can be tested, calibrated, and re-established for precision era use, based on abundant redshift-independent distances data available in NED-D. Indicator one employs the largest Giant Spiral Galaxies, which have an absolute isophotal major diameter of ~70 +/- 10 kpc, offering standard ruler-based distances with <10% precision. Indicator two employs the diameter-magnitude relation for spirals in general, as a secondary indicator, offering ~20% precision. The ruler-based indicator is the only indicator with <10% precision able to independently calibrate type Ia supernovae-based distances at cosmological distances. The secondary-based indicator is the only indicator with 20% precision applicable to more galaxies than in current Tully-Fisher surveys. The primary indicator gives researchers a new tool to confirm or refute if, as currently believed, universal expansion is accelerating. The secondary indicator gives researchers a new path toward acquiring a more complete 3D picture of the local universe and potentially, because the majority of galaxies in the universe are spirals, the distant universe.

  7. Far infrared structure of spiral galaxies from the IRAS CPC images

    NASA Technical Reports Server (NTRS)

    Wainscoat, Richard J.; Chokshi, Arati; Doyle, Laurance R.

    1989-01-01

    Significant extended far infrared (50 micron and 100 micron) structure was found for five face-on spiral galaxies (NGC2403, M51, M83, NGC6946, and IC342) from fourteen galaxies searched in the Infrared Astronomy Satellite (IRAS) chopped photometric channel (CPC) catalogue. Images were initially processed to remove instrumental and background artifacts, the isophotal centroids of each image determined, and multiple images of each galaxy (for each wavelength) superimposed and averaged to improve signal-to-noise. Calibration of these images was performed using IRAS survey array data. Infrared isophotes were then superimposed on optical (blue) images so that direct structural comparisons could be made.

  8. 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.

  9. The basic dynamical mechanism in spiral galaxies.

    PubMed

    Pfenniger, Daniel; Revaz, Yves

    2005-06-01

    This paper explicates the most fundamental mechanism that rules spiral galaxies. Although spiral galaxies are complex systems for which we do not yet have a complete understanding, the dark matter being the most severe unknown, it is possible to pinpoint the few physical factors that determine their most important properties, such as bars and spiral arms. Dynamics linked to the dissipative nature of gas and its transformation into stars provides clues that spiral galaxies are driven by dissipation close to a state of marginal stability with respect to the dynamics in the galaxy plane. Here, we present numerical evidence suggesting that warps play a similar role but in the transverse direction. N-body simulations show that typical galactic disks are also marginally stable with respect to a bending instability, leading to typical observed warps. The frequent occurrence of warps and asymmetries in the outer galactic disks, like bars in the inner disks, give new constraints on the dark matter, but this time in the outer disks.

  10. Magnetic spiral arms in galaxy haloes

    NASA Astrophysics Data System (ADS)

    Henriksen, R. N.

    2017-08-01

    We seek the conditions for a steady mean field galactic dynamo. The parameter set is reduced to those appearing in the α2 and α/ω dynamo, namely velocity amplitudes, and the ratio of sub-scale helicity to diffusivity. The parameters can be allowed to vary on conical spirals. We analyse the mean field dynamo equations in terms of scale invariant logarithmic spiral modes and special exact solutions. Compatible scale invariant gravitational spiral arms are introduced and illustrated in an appendix, but the detailed dynamical interaction with the magnetic field is left for another work. As a result of planar magnetic spirals `lifting' into the halo, multiple sign changes in average rotation measures forming a regular pattern on each side of the galactic minor axis, are predicted. Such changes have recently been detected in the Continuum Halos in Nearby Galaxies-an EVLA Survey (CHANG-ES) survey.

  11. An Infrared Portrait of the Barred Spiral Galaxy Messier 83

    NASA Astrophysics Data System (ADS)

    2001-11-01

    Messier 83 (M83) is a relatively nearby spiral galaxy with a pronounced bar-like structure. It is located in the southern constellation Hydra (The Water-Snake) and is also known as NGC 5236 ; the distance is approximately 12 million light-years. Images of M83 obtained in visible light - like the VLT photo published exactly two years ago ( ESO PR 18/99 ) - show clumpy, well-defined spiral arms that are rich in young stars while the disk reveals a complex system of intricate dust lanes. This galaxy is known to be a site of vigorous star formation and no less than six supernovae (exploding stars) have been observed in M83 during the past century. It is a fairly symmetrical object and possesses no nearby companions. Gas dynamics and galaxy bars Investigations of gas motions in the nucleus and in the main disk play a key role in understanding the structure and evolution of barred spiral galaxies like M83. Inflow of gas towards the center caused by a mass distribution that is not circularly symmetric is often invoked to explain certain observed phenomena, e.g., the feeding of Active Galactic Nuclei (AGNs, see also the report about recent observations in three such galaxies in ESO PR 18/01 ), and the fueling of bursts of star formation in the nuclear region. Some astronomers think that this process may cause a change of a galaxy's (morphological) type, for instance from barred to normal spiral galaxy. It has also been suggested that the development of spiral structures in galactic disks may be due to central stellar bars. Interstellar gas that is subject to periodical perturbations by the non-circularly symmetrical gravitational field in a barred system will develop a "density wave" that attracts neighbouring stars and gas. The local density increases and once a certain ("critical") value is reached, star formation is "ignited" in this area. The mass distribution In order to better understand phenomena like these, it is essential to know in detail the distribution of

  12. Magnificant Details in a Dusty Spiral Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    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. 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, seen as dark patches and streaks silhouetted against the starlight.

  13. 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

  14. 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

  15. 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).

  16. A Chandra survey of nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Kilgard, R. E.; Krauss, M. I.; Kaaret, P.; Prestwich, A. H.; Ward, M. J.

    We present results from a Chandra survey of 11 nearby, face-on spiral galaxies. 24 observations totalling 900 ks of new and archival Chandra data reveal more than 1000 X-ray point sources associated with the galaxies, diffuse emission, and hundreds of serendipitous sources. We discuss source populations and luminosity functions and show that the slope of the X-ray luminosity function is correlated with the star formation rate in the galaxies. We also discuss ultraluminous X-ray sources in comparison with sources within the Milky Way. Finally, we discuss ongoing work on source classification based upon X-ray colors and spectra, position within the host galaxies, and multiwavelenth counterparts.

  17. 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.

  18. A photometrically and spectroscopically confirmed population of passive spiral galaxies

    NASA Astrophysics Data System (ADS)

    Fraser-McKelvie, Amelia; Brown, Michael J. I.; Pimbblet, Kevin A.; Dolley, Tim; Crossett, Jacob P.; Bonne, Nicolas J.

    2016-10-01

    We have identified a population of passive spiral galaxies from photometry and integral field spectroscopy. We selected z < 0.035 spiral galaxies that have WISE colours consistent with little mid-infrared emission from warm dust. Matched aperture photometry of 51 spiral galaxies in ultraviolet, optical and mid-infrared show these galaxies have colours consistent with passive galaxies. Six galaxies form a spectroscopic pilot study and were observed using the Wide-Field Spectrograph to check for signs of nebular emission from star formation. We see no evidence of substantial nebular emission found in previous red spiral samples. These six galaxies possess absorption-line spectra with 4000 Å breaks consistent with an average luminosity-weighted age of 2.3 Gyr. Our photometric and integral field spectroscopic observations confirm the existence of a population of local passive spiral galaxies, implying that transformation into early-type morphologies is not required for the quenching of star formation.

  19. 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.

  20. 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.

  1. Secular Evolution of Spiral Galaxies

    DTIC Science & Technology

    2003-01-01

    observationthat dwarf, irregular, and L galaxies share quite sim-ilar distributions; and the prediction of cusp -like darkmatter cores in low surface...which is too clumpy (or can easilybecome too clumpy) on small scales, yet too smoothon large scales. For example, the cusp problem andthe satellite...and dwarfgalaxies are found not to possess such cuspy cores(de Blok, McGaugh, & Rubin 2001). Even invok-ing maximum feedback does not solve the cusp

  2. Gargantuan Super Spiral Galaxies Loom Large in the Cosmos

    NASA Image and Video Library

    2016-03-17

    In archived NASA data, researchers have discovered "super spiral" galaxies that dwarf our own spiral galaxy, the Milky Way, and compete in size and brightness with the largest galaxies in the universe. The unprecedented galaxies have long hidden in plain sight by mimicking the appearance of typical spirals. Three examples of super spirals are presented here in images taken by the Sloan Digital Sky Survey. The super spiral on the left (Figure 1), catalogued as 2MASX J08542169+0449308, contains two galactic nuclei, instead of just the usual one, and thus looks like two eggs frying in a pan. The central image (Figure 2) shows a super spiral designated 2MASX J16014061+2718161, and it also contains the double nuclei. On the right (Figure 3), a huge galaxy with the moniker SDSS J094700.08+254045.7 stands as one of the biggest and brightest super spirals. The mega-galaxy's starry disk and spiral arms stretch about 320,000 light-years across, or more than three times the breadth of the Milky Way. These double nuclei, which are known to result from the recent merger of two galaxies, could offer a vital hint about the potential origin of super spirals. Researchers speculate that a special merger involving two, gas-rich spiral galaxies could see their pooled gases settle down into a new, larger stellar disk -- presto, a super spiral. The super spirals were discovered using the NASA/IPAC Extragalactic Database, or NED, an online repository containing information on over 100 million galaxies. NED brings together a wealth of data from many different projects, including ultraviolet light observations from the Galaxy Evolution Explorer, visible light from Sloan Digital Sky Survey, infrared light from the 2-Micron All-Sky Survey, and links to data from other missions such as NASA's Spitzer Space Telescope and Wide-Field Infrared Survey Explorer, or WISE. http://photojournal.jpl.nasa.gov/catalog/PIA20064

  3. The age distribution of stellar clusters in M83

    NASA Astrophysics Data System (ADS)

    Silva-Villa, E.; Adamo, A.; Bastian, N.; Fouesneau, M.; Zackrisson, E.

    2014-05-01

    In order to empirically determine the time-scale and environmental dependence of stellar cluster disruption, we have undertaken an analysis of the unprecedented multipointing (seven), multiwavelength (U, B, V, Hα, and I) Hubble Space Telescope imaging survey of the nearby, face-on spiral galaxy M83. The images are used to locate stellar clusters and stellar associations throughout the galaxy. Estimation of cluster properties (age, mass, and extinction) was done through a comparison of their spectral energy distributions with simple stellar population models. We constructed the largest catalogue of stellar clusters and associations in this galaxy to-date, with ˜1800 sources with masses above ˜5000 M⊙ and ages younger than ˜300 Myr. In this Letter, we focus on the age distribution of the resulting clusters and associations. In particular, we explicitly test whether the age distributions are related with the ambient environment. Our results are in excellent agreement with previous studies of age distributions in the centre of the galaxy, which gives us confidence to expand out to search for similarities or differences in the other fields which sample different environments. We find that the age distribution of the clusters inside M83 varies strongly as a function of position within the galaxy, indicating a strong correlation with the galactic environment. If the age distributions are approximated as a power law of the form {d N/dt}∝ t^{ζ }, we find ζ values between 0 and -0.62 (ζ ˜ -0.40 for the whole galaxy), in good agreement with previous results and theoretical predictions. L101

  4. Giant cyclones in gaseous discs of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Fridman, A. M.; Khoruzhii, O. V.; Polyachenko, E.; Zasov, A. V.; Sil'chenko, O. K.; Afanas'ev, V. L.; Dodonov, S. N.; Moiseev, A. V.

    1999-12-01

    We report the detection of giant cyclonic vortices in the gaseous disc of the spiral galaxy NGC 3631 in the reference frame rotating with the spiral pattern. A presence of such structures was predicted by the authors for galaxies, where the radial gradient of the perturbed velocity exceeds that of the rotational velocity. This situation really takes place in NGC 3631.

  5. Chemical abundances in nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Richer, Michael Gerard

    2015-08-01

    The chemical abundances observed in planetary nebulae in the discs of spiral galaxies are revealing a rich variety of information about their progenitor stars as well as the structure and evolution of the galaxies they inhabit. As concerns galaxy structure and evolution, most of the attention has been on whether gradients in chemical abundances have changed with time, but there is also the issue of the formation and origin of the stellar progenitors of planetary nebulae. The gradients in oxygen abundances for planetary nebulae in M81 and NGC 300 are shallower than the corresponding gradients for H II regions in these galaxies. On the other hand, the gradients for H II regions and planetary nebulae are similar in M33. In the case of M31, there is mounting evidence whose simplest explanation may not be related to internal processes, but instead may lay in the gravitational interaction between it and its neighbours, past and present. As concerns the nucleosynthesis of the stellar progenitors of these planetary nebulae, some results for both nitrogen and oxygen may indicate the production of these elements during the previous evolutionary stages of their progenitor stars. Nominally, this may not be surprising for nitrogen, but the results do not agree quantitatively with canonical theory. At this point, though, there are still too few studies to draw very firm conclusions regrading any of these topics. Even so, the surprises among the results found so far make clear that interpreting the chemical abundances in the planetary nebulae in nearby spirals will require considering the processes affecting both stellar and galactic evolution.

  6. The Nature of Red-Sequence Cluster Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Kashur, Lane; Barkhouse, Wayne; Sultanova, Madina; Kalawila Vithanage, Sandanuwa; Archer, Haylee; Foote, Gregory; Mathew, Elijah; Rude, Cody; Lopez-Cruz, Omar

    2017-01-01

    Preliminary analysis of the red-sequence galaxy population from a sample of 57 low-redshift galaxy clusters observed using the KPNO 0.9m telescope and 74 clusters from the WINGS dataset, indicates that a small fraction of red-sequence galaxies have a morphology consistent with spiral systems. For spiral galaxies to acquire the color of elliptical/S0s at a similar luminosity, they must either have been stripped of their star-forming gas at an earlier epoch, or contain a larger than normal fraction of dust. To test these ideas we have compiled a sample of red-sequence spiral galaxies and examined their infrared properties as measured by 2MASS, WISE, Spitzer, and Herschel. These IR data allows us to estimate the amount of dust in each of our red-sequence spiral galaxies. We compare the estimated dust mass in each of these red-sequence late-type galaxies with spiral galaxies located in the same cluster field but having colors inconsistent with the red-sequence. We thus provide a statistical measure to discriminate between purely passive spiral galaxy evolution and dusty spirals to explain the presence of these late-type systems in cluster red-sequences.

  7. A FUNDAMENTAL PLANE OF SPIRAL STRUCTURE IN DISK GALAXIES

    SciTech Connect

    Davis, Benjamin L.; Kennefick, Daniel; Kennefick, Julia; Shields, Douglas W.; Flatman, Russell; Hartley, Matthew T.; Berrier, Joel C.; Martinsson, Thomas P. K.; Swaters, Rob A.

    2015-03-20

    Spiral structure is the most distinctive feature of disk galaxies and yet debate persists about which theory of spiral structure is correct. Many versions of the density wave theory demand that the pitch angle be uniquely determined by the distribution of mass in the bulge and disk of the galaxy. We present evidence that the tangent of the pitch angle of logarithmic spiral arms in disk galaxies correlates strongly with the density of neutral atomic hydrogen in the disk and with the central stellar bulge mass of the galaxy. These three quantities, when plotted against each other, form a planar relationship that we argue should be fundamental to our understanding of spiral structure in disk galaxies. We further argue that any successful theory of spiral structure must be able to explain this relationship.

  8. The Young Outer Disk of M83

    NASA Astrophysics Data System (ADS)

    Davidge, T. J.

    2010-08-01

    Deep near-infrared images recorded with NICI on Gemini South are used to investigate the evolved stellar content in the outer southeast quadrant of the spiral galaxy M83. A diffuse population of asymptotic giant branch (AGB) stars is detected, indicating that there are stars outside of the previously identified young and intermediate age star clusters in the outer disk. The brightest AGB stars have M K >= -8, and the AGB luminosity function (LF) is well matched by model LFs that assume ages <=1 Gyr. The specific star formation rate (SFR) during the past few Gyr estimated from AGB star counts is consistent with that computed from mid-infrared observations of star clusters at similar radii, and it is concluded that the disruption timescale for star clusters in the outer disk is Lt1 Gyr. The LF and specific frequency of AGB stars vary with galactocentric radius, in a manner that is indicative of lower luminosity-weighted ages at larger radii. Modest numbers of red supergiants are also found, indicating that there has been star formation during the past 100 Myr, while the ratio of C stars to M giants is consistent with that expected for a solar metallicity system that has experienced a constant SFR for the past few Gyr. The results drawn from the properties of resolved AGB stars are broadly consistent with those deduced from integrated light observations in the UV. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a co-operative 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 of Canada (Canada), CONICYT (Chile), the Australian Research Council (Australia), the Ministerio da Ciencia e Technologia (Brazil), and the Ministerio de Ciencia, Tecnologia e Innovacion Productiva (Argentina).

  9. Globular cluster systems in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Nantais, Julie Beth

    We have performed a comprehensive spectroscopic and photometric analysis of the M81 globular cluster system, using Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging in the B, V, and I bands and 74 globular cluster spectra from Hectospec at the MMT. We have also performed a small spectroscopic study of the NGC 300 globular cluster system using the Boller & Chivens (B&C) Spectrograph on the Baade Telescope in Chile. We confirm 9 probable globular clusters in NGC 300 and 3 possible clusters with very low radial velocities. For our full NGC 300 cluster sample, plus one cluster from the literature, we find a mean [Fe/H] = --0.94 +/- 0.15; without the 3 "possible" clusters we find a mean [Fe/H] = --0.98 +/- 0.12. We identify over 200 globular cluster candidates in HST I-band imaging, and spectroscopically confirm 62 new globular clusters in M81. The M81 globular cluster system shows marginal evidence for a bimodal metallicity distribution. The mean metallicity of 107 confirmed M81 globular clusters is [Fe/H] = 1.06 +/- 0.07. The M81 globular cluster system shows significant rotation, at 108 +/- 22 km s-1. There is evidence for a metallicity gradient among the metal-poor clusters. We perform HST ACS BV I photometry and radial profile fitting on 85 spectroscopically confirmed globular clusters, 136 "good" globular cluster candidates, and 198 other star cluster candidates. The globular cluster luminosity function peaks at V0 ˜20.26. The properties of the M81 globular cluster system are very similar to those of the Milky Way and M31, suggesting a similar origin for all three galaxies. Our understanding of the origins of spiral galaxy globular cluster systems would be vastly improved by comprehensive studies of low-mass and late-type spiral galaxies, including HST I-band imaging to identify globular cluster candidates for spectroscopic confirmation.

  10. 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

  11. The 2X-Hi disks of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Koribalski, Bärbel S.

    2017-03-01

    The outskirts of galaxies - especially the very extended Hi disks of galaxies - are strongly affected by their local environment. I highlight the giant 2X-Hi disks of nearby galaxies (M 83, NGC 3621, and NGC 1512), studied as part of the Local Volume Hi Survey (LVHIS), their kinematics and relation to XUV disks, signatures of tidal interactions and accretion events, the M HI - D HI relation as well as the formation of tidal dwarf galaxies. - Using multi-wavelength data, I create 3D visualisations of the gas and stars in galaxies, with the shape of their warped disks obtained through kinematic modelling of their Hi velocity fields.

  12. The Ying and Yang of the M 83 Nucleus

    NASA Astrophysics Data System (ADS)

    Mast, Damián; Díaz, Rubén J.; Dottori, Horacio A.; Agüero, María P.; Rodrigues, Irapuán; Albacete-Colombo, Juan F.

    2010-05-01

    The spiral galaxy M 83, an SB(rs)b at only 4.5 Mpc, is a privileged case for study of the detailed physics on spatial scales of a tenth of a parsec. With 3-D spectroscopic observations using CIRPASS on Gemini-S, we studied the ionized gas properties in J-band with spatial resolution of 0.″5 (Figure 1). The Paβ velocity field shows two dynamical centers, neither of them coincident with the bulge center, identified with the optical nucleus (ON) and the hidden nucleus (HN), with masses, within a radius of 10 pc, of MON = (1.8±0.4)× 107 M⊙ and MHN = (1.0±0.4)× 107 M⊙. Using the Paβ equivalent width together with population synthesis models, we are able to estimate the ages of both mass concentrations, TON = 8 Myr and THN =6-7 Myr. Adding complexity to this puzzling scenario, we used GMOS+Gemini imaging and spectroscopy to study the radio source J133658.3-295105 (Dottori et al. 2008) and find that Hα emission at the position of this source is redshifted by ~130 km s-1 with respect to an M 83 H II region, leading us to face the possibility of that we are witnessing the ejection of an object by gravitational recoil from the M 83 nucleus. A fit to the X-ray spectrum obtained Chandra supports the association between this source and the disk of M 83 by the presence of the Fe Kα line at 6.7 keV.

  13. High chemical abundances in stripped Virgo spiral galaxies

    NASA Astrophysics Data System (ADS)

    Skillman, E. D.; Kennicutt, R. C.; Shields, G. A.

    1993-01-01

    Based on a comparison of the oxygen abundances in H 2 regions in field and Virgo cluster late type spiral galaxies, Shields, Skillman, & Kennicutt (1991) suggested that the highly stripped spiral galaxies in the Virgo cluster have systematically higher abundances than comparable field galaxies. In April 1991 and May 1992 we used the blue channel spectrograph on the MMT to obtain new observations of 30 H 2 regions in Virgo spiral galaxies. These spectra cover the wavelength range from (O II) lambda 3727 to (S II) lambda 6731. We now have observed at least 4 H II regions in 9 spiral galaxies in the Virgo cluster. Combining (O II) and (O III) line strengths, we calculate the H II region oxygen abundances based on the empirical calibration of Edmunds & Pagel (1984). These observations show: (1) The stripped, low luminosity Virgo spirals (N4689, N4571) truly have abundances characteristic of much more luminous field spirals; (2) Virgo spirals which show no evidence of stripping (N4651, N4713) have abundances comparable to field galaxies; and (3) Evidence for transition galaxies (e.g., N4254, N4321), with marginally stripped disks and marginal abundance enhancements. The new observations presented here confirm the validity of the oxygen over-abundances in the stripped Virgo spirals. Shields et al. (1991) discussed two different mechanisms for producing the higher abundances in the disks of stripped galaxies in Virgo. The first is the supression of infall of near-primordial material, the second is the suppression of radial inflow of metal-poor gas. Distinguishing between the two cases will require more observations of the Virgo cluster spirals and a better understanding of which parameters determine the variation of abundance with radius in field spirals (cf., Garnett & Shields 1987).

  14. High chemical abundances in stripped Virgo spiral galaxies

    NASA Technical Reports Server (NTRS)

    Skillman, E. D.; Kennicutt, R. C.; Shields, G. A.

    1993-01-01

    Based on a comparison of the oxygen abundances in H 2 regions in field and Virgo cluster late type spiral galaxies, Shields, Skillman, & Kennicutt (1991) suggested that the highly stripped spiral galaxies in the Virgo cluster have systematically higher abundances than comparable field galaxies. In April 1991 and May 1992 we used the blue channel spectrograph on the MMT to obtain new observations of 30 H 2 regions in Virgo spiral galaxies. These spectra cover the wavelength range from (O II) lambda 3727 to (S II) lambda 6731. We now have observed at least 4 H II regions in 9 spiral galaxies in the Virgo cluster. Combining (O II) and (O III) line strengths, we calculate the H II region oxygen abundances based on the empirical calibration of Edmunds & Pagel (1984). These observations show: (1) The stripped, low luminosity Virgo spirals (N4689, N4571) truly have abundances characteristic of much more luminous field spirals; (2) Virgo spirals which show no evidence of stripping (N4651, N4713) have abundances comparable to field galaxies; and (3) Evidence for transition galaxies (e.g., N4254, N4321), with marginally stripped disks and marginal abundance enhancements. The new observations presented here confirm the validity of the oxygen over-abundances in the stripped Virgo spirals. Shields et al. (1991) discussed two different mechanisms for producing the higher abundances in the disks of stripped galaxies in Virgo. The first is the supression of infall of near-primordial material, the second is the suppression of radial inflow of metal-poor gas. Distinguishing between the two cases will require more observations of the Virgo cluster spirals and a better understanding of which parameters determine the variation of abundance with radius in field spirals (cf., Garnett & Shields 1987).

  15. ROSAT observations of Several Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Cui, Wei

    1994-01-01

    We have made observations of several nearby face-on normal spiral galaxies with the ROSAT PSPC to study their 01-2 0 keV diffuse X-ray emission. The cleaned X-ray images of NGC3184, M101, NGC4395, NGC4736 and NGC5055 in the 1/4, 3/4 and 1.5 keV energy bands are presented along with a detailed discussion of how to identify and model known types of non-cosmic X-ray background. Unresolved X-ray emission in the 0.1-2.0 keV range is detected in all the observed galaxies, bright at the center and getting fainter toward the outer edges. It is a combination of diffuse emission and contribution from un-resolved point sources in these galaxies, so represents an upper limit to the diffuse X-ray emission. The derived upper limits on the diffuse emission can be interpreted in terms of upper limits to average emission measure for a putative unabsorbed halo emission, or alternatively as limits on the filling factors of 106 K hot bubbles, similar to the one surrounding the Sun, in the disks of these galaxies. They can also be used to derive limits to the total energy radiated by hot gas as a function of its temperature for various assumed absorbing geometries. Another exciting possibility is to measure shadows of the 1/4 keV extragalactic X-ray background cast by the external galaxies, which then allow us to determine useful limits on it The absorption features observed at the outer edges of some of the galaxies are direct evidence for absorption of this background by matter in there galaxies, and we have derived a 96% confidence lower limit of 32 keV cm-2 s-l sr-l keV-l. This lower limit can be compared directly with the best 95% confidence upper limit derived from observations of the Small Magellanic Cloud, which is 45 keV cm-2 s-l , sr-l keV-l The e lower and upper limits are less than a factor of two apart, and bend to provide a reasonable measurement of the actual value of the 1/4 keV extragalactic X-ray intensity

  16. Arm and interarm abundance gradients in CALIFA spiral galaxies

    NASA Astrophysics Data System (ADS)

    Sánchez-Menguiano, L.; Sánchez, S. F.; Pérez, I.; Debattista, V. P.; Ruiz-Lara, T.; Florido, E.; Cavichia, O.; Galbany, L.; Marino, R. A.; Mast, D.; Sánchez-Blázquez, P.; Méndez-Abreu, J.; de Lorenzo-Cáceres, A.; Catalán-Torrecilla, C.; Cano-Díaz, M.; Márquez, I.; McIntosh, D. H.; Ascasibar, Y.; García-Benito, R.; Gónzalez Delgado, R. M.; Kehrig, C.; López-Sánchez, Á. R.; Mollá, M.; Bland-Hawthorn, J.; Walcher, C. J.; Costantin, L.

    2017-07-01

    Spiral arms are the most singular features in disc galaxies. These structures can exhibit different patterns, namely grand design and flocculent arms, with easily distinguishable characteristics. However, their origin and the mechanisms shaping them are unclear. The overall role of spirals in the chemical evolution of disc galaxies is another unsolved question. In particular, it has not been fully explored if the H ii regions of spiral arms present different properties from those located in the interarm regions. Here we analyse the radial oxygen abundance gradient of the arm and interarm star forming regions of 63 face-on spiral galaxies using CALIFA Integral Field Spectroscopy data. We focus the analysis on three characteristic parameters of the profile: slope, zero-point, and scatter. The sample is morphologically separated into flocculent versus grand design spirals and barred versus unbarred galaxies. We find subtle but statistically significant differences betweenthe arm and interarm distributions for flocculent galaxies, suggesting that the mechanisms generating the spiral structure in these galaxies may be different to those producing grand design systems, for which no significant differences are found. We also find small differences in barred galaxies, not observed in unbarred systems, hinting that bars may affect the chemical distribution of these galaxies but not strongly enough as to be reflected in the overall abundance distribution. In light of these results, we propose bars and flocculent structure as two distinct mechanisms inducing differences in the abundance distribution between arm and interarm star forming regions.

  17. Galaxy Zoo: star formation versus spiral arm number

    NASA Astrophysics Data System (ADS)

    Hart, Ross E.; Bamford, Steven P.; Casteels, Kevin R. V.; Kruk, Sandor J.; Lintott, Chris J.; Masters, Karen L.

    2017-06-01

    Spiral arms are common features in low-redshift disc galaxies, and are prominent sites of star formation and dust obscuration. However, spiral structure can take many forms: from galaxies displaying two strong 'grand design' arms to those with many 'flocculent' arms. We investigate how these different arm types are related to a galaxy's star formation and gas properties by making use of visual spiral arm number measurements from Galaxy Zoo 2. We combine ultraviolet and mid-infrared (MIR) photometry from GALEX and WISE to measure the rates and relative fractions of obscured and unobscured star formation in a sample of low-redshift SDSS spirals. Total star formation rate has little dependence on spiral arm multiplicity, but two-armed spirals convert their gas to stars more efficiently. We find significant differences in the fraction of obscured star formation: an additional ˜10 per cent of star formation in two-armed galaxies is identified via MIR dust emission, compared to that in many-armed galaxies. The latter are also significantly offset below the IRX-β relation for low-redshift star-forming galaxies. We present several explanations for these differences versus arm number: variations in the spatial distribution, sizes or clearing time-scales of star-forming regions (i.e. molecular clouds), or contrasting recent star formation histories.

  18. Efficient star formation in the bright bar of M83

    NASA Technical Reports Server (NTRS)

    Lord, S. D.; Strom, S. E.; Young, J. S.

    1987-01-01

    The bright molecular bar in M83 was detected standing out as a 100% enhancement of molecular emission with respect to the off-bar emission at the same radii. The spatial variations in the star formation efficiency, as traced by H alpha emission and the surface density of the interstellar gas, in M83 and M51 were compared. Both the central bar of M83 and the spiral arms of M51 are regions characterized by high massive star formation rates. For M83, it is ascribed that both the gas surface density and the star formation efficiency are high to the hydrodynamics of the central region.

  19. Pitch Angle Restriction in late Type Spiral Galaxies.

    NASA Astrophysics Data System (ADS)

    Perez Villegas, Maria de Los Angeles; Pichardo, B.; Moreno, E.; Peimbert, A.; Velazquez, H. M.

    2012-01-01

    With a set of models for low bulge mass spiral galaxies (late type as defined by Hubble classification), that include a novel 3-D self-gravitating potential based on density distribution for spiral arms (PERLAS), instead of the usual 2D approximations (cosine potentials), we have analyzed the galactic orbital dynamics as a function of the pitch angle (going from 10 to 60 degrees). We found, from an extensive orbital study in phase space, that for late spiral galaxies, with angles lager than 50 deg, chaos may become pervasive, having the effects of destroying the order phase space surrounding the main stable periodic orbits that sculpt spiral arms and even destroying them. This result is in good agreement with observations of late spiral galaxies, where the maximum observed pitch angle is about 50 degrees.

  20. 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.

  1. Hα Imaging of Early-type(Sa-Sab) Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Hameed, S.; Devereux, N.

    1997-12-01

    Hα imaging of Early-type (Sa-Sab) Spirals A recent analysis of the IRAS database indicates that the massive star formation rates in early-type(Sa-Sab) spirals are comparable to the massive star formation rates in late-type spirals. We are conducting an Hα imaging survey of a complete sample of nearby (D <= 40Mpc), bright (m(B) <= 12.1), early-type spirals to confirm the results obtained by IRAS. Our preliminary results indicate that a majority of these galaxies show either signs of interaction, and/or host nuclear starbursts. The occurence of nuclear starbursts in early-type spirals may be related to the propensity for such galaxies to also host Seyfert nuclei. The evidence for interactions suggests that early-type spirals are evolving in the current epoch.

  2. Smooth dark spiral arms in the flocculent galaxy NGC2841

    NASA Astrophysics Data System (ADS)

    Block, David L.; Elmegreen, B. G.; Wainscoat, R. J.

    1996-06-01

    OPTICAL images of the arms of spiral galaxies invariably show massive blue stars forming in ridges of interstellar gas and dust1. These are particularly striking in 'grand-design' galaxies, in which the stellar positions are influenced by spiral density waves1. By contrast, many galaxies have a 'flocculent' appearance, with no obvious evidence of spiral structure at visible wavelengths. Here we report infrared observations of the prototype flocculent galaxy NGC2841, which reveal a remarkable system of long, dark spiral arms. These arms arise from concentrations of dust; they are hidden at optical wavelengths by light scattered from the dust. The mechanism that has organized the gas and dust into these dark arms is at present unclear; the arms might be highly sheared dense clouds, or they might correspond to density waves in the interstellar medium driven by an elongated central bulge, which would not affect the stable stellar disk.

  3. The Supermassive Black Hole Mass Function in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Kennefick, Julia D.; Berrier, J. C.; Kennefick, D.; Davis, B. L.; Seigar, M.; Shields, D.; Barrows, R. S.; Lacy, C. H.; Hughes, J. A.; Galaxy Evolution Survey, Arkansas

    2013-01-01

    The AGES group is exploring a number of techniques to study the relationship between central SMBH black hole mass and spiral arm morphology in disk galaxies. We have developed a new technique which permits us to reliably and accurately measure pitch angle based upon a 2DFFT algorithm. We have then compared pitch angles to directly measured black hole masses in local galaxies and demonstrated a strong correlation between them. Using the relation thus established we have developed a pitch angle distribution function of a statistically complete volume limited sample of nearby galaxies and developed a central black hole mass function for nearby spiral galaxies.

  4. 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.

  5. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Maier, Erin; Chien, Li-Hsin; Hunter, Deidre A.

    2016-11-01

    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. on the Small Magellanic Cloud, we use the third and fourth statistical moments, as indicators of structures caused by turbulence, to examine the neutral hydrogen (H i) column density of a sample of spiral galaxies selected from The H i Nearby Galaxy Survey. We apply the statistical moments in three different methods—the galaxy as a whole, divided into a function of radii and then into grids. We create individual grid maps of kurtosis for each galaxy. To investigate the relation between these moments and star formation, we compare these maps with their far-ultraviolet images taken by the Galaxy Evolution Explorer satellite.We find that the moments are largely uniform across the galaxies, in which 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 that we are sensitive to greater than ∼700 pc. From comparison between the moments themselves, we find that the gas motions in our sampled galaxies are largely supersonic. This analysis also shows that the Burkhart et al. methods may be applied not just to dwarf galaxies but also to normal spiral galaxies.

  8. Environment Dependence of Disk Morphology of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Ann, Hong Bae

    2014-02-01

    We analyze the dependence of disk morphology (arm class, Hubble type, bar type) of nearby spiral galaxies on the galaxy environment by using local background density (Σ_{n}), project distance (r_{p}), and tidal index (TI) as measures of the environment. There is a strong dependence of arm class and Hubble type on the galaxy environment, while the bar type exhibits a weak dependence with a high frequency of SB galaxies in high density regions. Grand design fractions and early-type fractions increase with increasing Σ_{n}, 1/r_{p}, and TI, while fractions of flocculent spirals and late-type spirals decrease. Multiple-arm and intermediate-type spirals exhibit nearly constant fractions with weak trends similar to grand design and early-type spirals. While bar types show only a marginal dependence on Σ_{n}, they show a fairly clear dependence on r_{p} with a high frequency of SB galaxies at small r_{p}. The arm class also exhibits a stronger correlation with r_{p} than Σ_{n} and TI, whereas the Hubble type exhibits similar correlations with Σ_{n} and r_{p}. This suggests that the arm class is mostly affected by the nearest neighbor while the Hubble type is affected by the local densities contributed by neighboring galaxies as well as the nearest neighbor.

  9. 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.

  10. 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.

  11. Gas Ejection from Spiral Galaxy Disks

    NASA Astrophysics Data System (ADS)

    Durelle, Jeremy

    We present the results of three proposed mechanisms for ejection of gas from a spiral arm into the halo. The mechanisms were modelled using magnetohydrodynamics (MHD) as a theoretical template. Each mechanism was run through simulations using a Fortran code: ZEUS-3D, an MHD equation solver. The first mechanism modelled the gas dynamics with a modified Hartmann flow which describes the fluid flow between two parallel plates. We initialized the problem based on observation of lagging halos; that is, that the rotational velocity falls to a zero at some height above the plane of the disk. When adopting a density profile which takes into account the various warm and cold H I and HII molecular clouds, the system evolves very strangely and does not reproduce the steady velocity gradient observed in edge-on galaxies. This density profile, adopted from Martos and Cox (1998), was used in the remaining models. However, when treating a system with a uniform density profile, a stable simulation can result. Next we considered supernova (SN) blasts as a possible mechanism for gas ejection. While a single SN was shown to be insufficient to promote vertical gas structures from the disk, multiple SN explosions proved to be enough to promote gas ejection from the disk. In these simulations, gas ejected to a height of 0.5 kpc at a velocity of 130 km s--1 from 500 supernovae, extending to an approximate maximum height of 1 kpc at a velocity of 6.7 x 103 km s--1 from 1500 supernovae after 0.15 Myr, the approximate time of propagation of a supernova shock wave. Finally, we simulated gas flowing into the spiral arm at such a speed to promote a jump in the disk gas, termed a hydraulic jump. The height of the jump was found to be slightly less than a kiloparsec with a flow velocity of 41 km s--1 into the halo after 167 Myr. The latter models proved to be effective mechanisms through which gas is ejected from the disk whereas the Hartmann flow (or toy model) mechanism remains unclear as the

  12. OBSERVATIONAL EVIDENCE AGAINST LONG-LIVED SPIRAL ARMS IN GALAXIES

    SciTech Connect

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

    2011-07-10

    We test whether the spiral patterns apparent in many large disk galaxies should be thought of as dynamical features that are stationary in a corotating frame for {approx}> t{sub dyn}, as implied by the density wave approach for explaining spiral arms. If such spiral arms have enhanced star formation (SF), observational tracers for different stages of the SF sequence should show a spatial ordering, from upstream to downstream in the corotating frame: dense H I, CO, tracing molecular hydrogen gas, 24 {mu}m emission tracing enshrouded SF, and UV emission tracing unobscured young stars. We argue that such a spatial ordering should be reflected in the angular cross-correlation (CC, in polar coordinates) using all azimuthal positions among pairs of these tracers; the peak of the CC should be offset from zero, in different directions inside and outside the corotation radius. Recent spiral SF simulations by Dobbs and Pringle show explicitly that for the case of a stationary spiral arm potential such angular offsets between gas and young stars of differing ages should be observable as cross-correlation offsets. We calculate the angular cross-correlations for different observational SF sequence tracers in 12 nearby spiral galaxies, drawing on a data set with high-quality maps of the neutral gas (H I, THINGS) and molecular gas (CO, HERACLES), along with 24 {mu}m emission (Spitzer, SINGS); we include FUV images (GALEX) and 3.6 {mu}m emission (Spitzer, IRAC) for some galaxies, tracing aging stars and longer timescales. In none of the resulting tracer cross-correlations for this sample do we find systematic angular offsets, which would be expected for a stationary dynamical spiral pattern of well-defined pattern speed. This result indicates that spiral density waves in their simplest form are not an important aspect of explaining spirals in large disk galaxies.

  13. 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

  14. The similar stellar populations of quiescent spiral and elliptical galaxies

    NASA Astrophysics Data System (ADS)

    Robaina, Aday R.; Hoyle, Ben; Gallazzi, Anna; Jiménez, Raul; van der Wel, Arjen; Verde, Licia

    2012-12-01

    We compare the stellar population properties in the central regions of visually classified non-star-forming spiral and elliptical galaxies from Galaxy Zoo and Sloan Digital Sky Survey (SDSS) Data Release 7. The galaxies lie in the redshift range 0.04 < z < 0.1 and have stellar masses larger than log M* = 10.4. We select only face-on spiral galaxies in order to avoid contamination by light from the disc in the SDSS fibre and enabling the robust visual identification of spiral structure. Overall, we find that galaxies with larger central stellar velocity dispersions, regardless of morphological type, have older ages, higher metallicities and an increased overabundance of α-elements. Age and α-enhancement, at fixed velocity dispersion, do not depend on morphological type. The only parameter that, at a given velocity dispersion, correlates with morphological type is metallicity, where the metallicity of the bulges of spiral galaxies is 0.07 dex higher than that of the ellipticals. However, for galaxies with a given total stellar mass, this dependence on morphology disappears. Under the assumption that, for our sample, the velocity dispersion traces the mass of the bulge alone, as opposed to the total mass (bulge+disc) of the galaxy, our results imply that the formation epoch of galaxy and the duration of its star-forming period are linked to the mass of the bulge. The extent to which metals are retained within the galaxy, and not removed as a result of outflows, is determined by the total mass of the galaxy.

  15. Tidal Origin of Spiral Arms in Galaxies Orbiting a Cluster

    NASA Astrophysics Data System (ADS)

    Semczuk, Marcin; Łokas, Ewa L.; del Pino, Andrés

    2017-01-01

    One of the scenarios for the formation of grand-design spiral arms in disky galaxies involves their interactions with a satellite or another galaxy. Here we consider another possibility, where the perturbation is instead due to the potential of a galaxy cluster. Using N-body simulations we investigate the formation and evolution of spiral arms in a Milky-Way-like galaxy orbiting a Virgo-like cluster. The galaxy is placed on a few orbits of different size but similar eccentricity and its evolution are followed for 10 Gyr. The tidally induced, two-armed, approximately logarithmic spiral structure forms on each of them during the pericenter passages. The spiral arms dissipate and wind up with time, to be triggered again at the next pericenter passage. We confirm this transient and recurrent nature of the arms by analyzing the time evolution of the pitch angle and the arm strength. We find that the strongest arms are formed on the tightest orbit; however, they wind up rather quickly and are disturbed by another pericenter passage. The arms on the most extended orbit, which we analyze in more detail, wind up slowly and survive for the longest time. Measurements of the pattern speed of the arms indicate that they are kinematic density waves. We attempt a comparison with observations by selecting grand-design spiral galaxies in the Virgo cluster. Among those, we find nine examples bearing no sign of recent interactions or the presence of companions. For three of them we present close structural analogues among our simulated spiral galaxies.

  16. Star Formation Activity of Barred Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Kim, Eunbin; Hwang, Ho Seong; Chung, Haeun; Lee, Gwang-Ho; Park, Changbom; Cervantes Sodi, Bernardo; Kim, Sungsoo S.

    2017-08-01

    We study the star formation activity of nearby galaxies with bars using a sample of late-type galaxies at 0.02≤slant z≤slant 0.05489 and {M}r< -19.5 from the Sloan Digital Sky Survey. We compare the physical properties of strongly and weakly barred galaxies with those of non-barred galaxies that have stellar mass and redshift distributions similar to barred galaxies. We find that the star formation activity of strongly barred galaxies probed by starburstiness, g-r, {NUV}-r, and mid-infrared [3.4]-[12] colors is, on average, lower than that of non-barred galaxies. However, weakly barred galaxies do not show such a difference between barred and non-barred galaxies. The amounts of atomic and molecular gas in strongly barred galaxies are smaller than those in non-barred galaxies, and the gas metallicity is higher in strongly barred galaxies than in non-barred galaxies. The gas properties of weakly barred galaxies again show no difference from those of non-barred galaxies. We stack the optical spectra of barred and non-barred galaxies in several mass bins and fit to the stacked spectra with a spectral fitting code, STARLIGHT. We find no significant difference in stellar populations between barred and non-barred galaxies for both strongly and weakly barred galaxies. Our results are consistent with the idea that the star formation activity of barred galaxies was enhanced in the past along with significant gas consumption, and is currently lower than or similar to that of non-barred galaxies. The past star formation enhancement depends on the strength of bars.

  17. 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).

  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. Halo Mass Concentration and the Morphology of Simulated Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Berlanga Medina, Jazmin; Berrier, Joel C.; Kennefick, Daniel; Arkansas Galaxy Evolution Survey

    2015-01-01

    Using a model based on the Milky Way, we vary the central concentration of the dark matter halo component of simulated spiral galaxies. We evolve 11 galaxies in isolation under the effects of gravity for a time of 3 Gyr and look for differences in the disk structure. We primarily quantify morphological differences with measurements of the spiral arms'pitch angle by using a two-dimensional fast Fourier transform code (2DFFT). Preliminary results indicate that while overall spiral arm structure is dynamic throughout the duration of the time range given, pitch angle values tend to restabilize during periods of reemerging spiral structure. This suggests that pitch angle may be fairly stable on timescales of a few Gyr, even if it tends to change at timescales of Myr. While concentration does seem to determine both the relative age at which simulated galaxies develop clearly visible spiral structure and the specific expression of spiral arms, a clear relationship between concentration vs pitch angle cannot be confirmed at this time.

  20. 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.

  1. Self-perpetuating Spiral Arms in Disk Galaxies

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  2. Rotation and mass in the Milky Way and spiral galaxies

    NASA Astrophysics Data System (ADS)

    Sofue, Yoshiaki

    2017-02-01

    Rotation curves are the basic tool for deriving the distribution of mass in spiral galaxies. In this review, we describe various methods to measure rotation curves in the Milky Way and spiral galaxies. We then describe two major methods to calculate the mass distribution using the rotation curve. By the direct method, the mass is calculated from rotation velocities without employing mass models. By the decomposition method, the rotation curve is deconvolved into multiple mass components by model fitting assuming a black hole, bulge, exponential disk, and dark halo. The decomposition is useful for statistical correlation analyses among the dynamical parameters of the mass components. We also review recent observations and derived results.

  3. Dark and luminous properties of low-luminosity spiral galaxies

    NASA Astrophysics Data System (ADS)

    Kogoshvili, N.; Borchkhadze, T.

    2012-08-01

    On the basis of data in our Merged Catalogue of Galaxies (MERCG), for which an online version is now available, we have analysed some properties of spiral galaxies that are members of pairs or small groups of galaxies. Our sample consists of a total of approximately 300 pairs and groups, distributed over the entire sky. In this context, low-luminosity spirals (LLS), here defined as those with an absolute magnitude of MB ≥ -20.6, are of particular interest, since they are thought to harbour dark matter. We find that the mean distance between the two components in LLS/LLS pairs of galaxies is significantly smaller than in LLS/elliptical (E), LLS/high-luminosity spiral (HLS) and HLS/HLS pairs, as well as in groups with at least one LLS. Moreover, LLS from this sample in the mean have larger central surface densities μo and smaller values of the full angular momentum K than HLS. In the second part, we investigate the relative frequencies of LLS galaxies, single as well as in pairs/groups. We find that they are 4-5 times more frequent inside and around three major clusters of galaxies (Virgo, Pegasus I and Perseus) than in the general field. Our findings all support the assumption that LLS galaxies are indeed carriers of dark matter.

  4. 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

  5. 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.

  6. The IRAS galaxy 0421+040P06: An active spiral (?) galaxy with extended radio lobes

    NASA Technical Reports Server (NTRS)

    Beichman, C. A.; Wynn-Williams, C. G.; Lonsdale, C. J.; Persson, S. E.; Heasley, J. N.; Miley, G. K.; Soifer, B. T.; Neugebauer, G.; Becklin, E. E.; Houck, J. R.

    1984-01-01

    The infrared bright galaxy 0421+040P06 detected by IRAS at 25 and 60 microns was studied at optical, infrared, and radio wavelength. It is a luminous galaxy with apparent spiral structure emitting 4 x 10 to the 37th power from far-infrared to optical wavelengths. Optical spectroscopy reveals a Seyfert 2 emission line spectrum, making 0421+040P06 the first active galaxy selected from an unbiased infrared survey of galaxies. The fact that this galaxy shows a flatter energy distribution with more 25 micron emission than other galaxies in the infrared sample may be related to the presence of an intense active nucleus. The radio observations reveal the presence of a non-thermal source that, at 6 cm, shows a prominent double lobed structure 20 to 30 kpc in size extending beyond the optical confines of the galaxy. The radio source is three to ten times larger than structures previously seen in spiral galaxies.

  7. Environmental Dependence of Warps in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Ann, Hong Bae; Bae, Hyun Jeong

    2016-12-01

    We determined the warp parameters of 192 warped galaxies which are selected from 340 edge-on galaxies using color images as well as r-band isophotal maps. We derive the local background density (Σ_{n}) to examine the dependence of the warp amplitudes on the galaxy environment. We find a clear trend that strongly warped galaxies are likely to be found in high density regions where tidal interactions are supposed to be frequent. However, the correlation between α_{w} and Σ_{n} is too weak for weakly warped galaxies (α_{w} < 4°) and the cumulative distributions of weakly warped galaxies are not significantly different from those of galaxies with no detectable warps. This suggests that tidal interactions do not play a decisive role in the formation of weak warps.}

  8. Nonlinear density wave theory for the spiral structure of galaxies.

    PubMed

    Kondoh, S; Teramoto, R; Yoshida, Z

    2000-05-01

    The theory of nonlinear waves for plasmas has been applied to the analysis of the density wave theory of galaxies which are many-body systems of gravity. A nonlinear Schrödinger equation has been derived by applying the reductive perturbation method on the fluid equations that describe the behavior of infinitesimally thin disk galaxies. Their spiral arms are characterized by a soliton and explained as a pattern of a propagating nonlinear density wave.

  9. Accretion, radial flows and abundance gradients in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Pezzulli, Gabriele; Fraternali, Filippo

    2016-01-01

    The metal-poor gas continuously accreting on to the discs of spiral galaxies is unlikely to arrive from the intergalactic medium (IGM) with exactly the same rotation velocity as the galaxy itself and even a small angular momentum mismatch inevitably drives radial gas flows within the disc, with significant consequences to galaxy evolution. Here, we provide some general analytic tools to compute accretion profiles, radial gas flows and abundance gradients in spiral galaxies as a function of the angular momentum of the accreting material. We generalize existing solutions for the decomposition of the gas flows, required to reproduce the structural properties of galaxy discs, into direct accretion from the IGM and a radial mass flux within the disc. We then solve the equation of metallicity evolution in the presence of radial gas flows with a novel method, based on characteristic lines, which greatly reduces the numerical demand on the computation and sheds light on the crucial role of boundary conditions on the abundance profiles predicted by theoretical models. We also discuss how structural and chemical constraints can be combined to disentangle the contributions of inside-out growth and radial flows in the development of abundance gradients in spiral galaxies. Illustrative examples are provided throughout with parameters plausible for the Milky Way. We find that the material accreting on the Milky Way should rotate at 70-80 per cent of the rotational velocity of the disc, in agreement with previous estimates.

  10. On wave dark matter in spiral and barred galaxies

    SciTech Connect

    Martinez-Medina, Luis A.; Matos, Tonatiuh; Bray, Hubert L. E-mail: bray@math.duke.edu

    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.

  11. The emission line sequence of normal spiral galaxies

    NASA Astrophysics Data System (ADS)

    Sodré, L., Jr.; Stasińska, G.

    1999-05-01

    We have analyzed the emission line properties in the integrated spectra of 15 normal spiral galaxies. We show that very clear trends appear when plotting relevant emission line ratios or equivalent widths as a function of galaxy spectral types, obtained with a Principal Component Analysis of the continua and absorption features of spectra. The equivalent widths of all the lines analyzed correlate extremely well with spectral types, implying that each of them can be considered a good indicator of the spectral type in normal galaxies. The position of most galaxies of our sample in classical emission line diagnostic diagrams follows that of individual giant HII regions in spiral galaxies, but for the earliest type galaxies, the emission line pattern resembles more that of LINERs. Therefore, the direct interpretation of equivalent widths in terms of star formation rates would be misleading in such cases. The observed trends in the emission line ratios as a function of galaxy spectral type suggest a decrease of O/H, a decrease of N/O, an increase of the average effective temperature or ionization parameter, and a decrease of the effective internal extinction of galaxies with increasing (early to late) spectral type.

  12. 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.

  13. Ultraviolet Halos around Spiral Galaxies. I. Morphology

    NASA Astrophysics Data System (ADS)

    Hodges-Kluck, Edmund; Cafmeyer, Julian; Bregman, Joel N.

    2016-12-01

    We examine ultraviolet halos around a sample of highly inclined galaxies within 25 Mpc to measure their morphology and luminosity. Despite contamination from galactic light scattered into the wings of the point-spread function, we find that ultraviolet (UV) halos occur around each galaxy in our sample. Around most galaxies the halos form a thick, diffuse disk-like structure, but starburst galaxies with galactic superwinds have qualitatively different halos that are more extensive and have filamentary structure. The spatial coincidence of the UV halos above star-forming regions, the lack of consistent association with outflows or extraplanar ionized gas, and the strong correlation between the halo and galaxy UV luminosity suggest that the UV light is an extragalactic reflection nebula. UV halos may thus represent 106-107 M ⊙ of dust within 2-10 kpc of the disk, whose properties may change with height in starburst galaxies.

  14. Magnetic field evolution and reversals in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Dobbs, C. L.; Price, D. J.; Pettitt, A. R.; Bate, M. R.; Tricco, T. S.

    2016-10-01

    We study the evolution of galactic magnetic fields using 3D smoothed particle magnetohydrodynamics (SPMHD) simulations of galaxies with an imposed spiral potential. We consider the appearance of reversals of the field, and amplification of the field. We find that magnetic field reversals occur when the velocity jump across the spiral shock is above ≈20 km s-1, occurring where the velocity change is highest, typically at the inner Lindblad resonance in our models. Reversals also occur at corotation, where the direction of the velocity field reverses in the corotating frame of a spiral arm. They occur earlier with a stronger amplitude spiral potential, and later or not at all with weaker or no spiral arms. The presence of a reversal at radii of around 4-6 kpc in our fiducial model is consistent with a reversal identified in the Milky Way, though we caution that alternative Galaxy models could give a similar reversal. We find that relatively high resolution, a few million particles in SPMHD, is required to produce consistent behaviour of the magnetic field. Amplification of the magnetic field occurs in the models, and while some may be genuinely attributable to differential rotation or spiral arms, some may be a numerical artefact. We check our results using ATHENA, finding reversals but less amplification of the field, suggesting that some of the amplification of the field with SPMHD is numerical.

  15. Determining the Co-Rotation Radius of Nearby Spiral Galaxies Using Spiral Arm Overlays

    NASA Astrophysics Data System (ADS)

    Shameer Abdeen, Mohamed; Kennefick, Daniel; Kennefick, Julia D.; Pour Imani, Hamed; Shields, Douglas W.; Eufrasio, Rafael; Berlanga Medina, Jazmin; Monson, Erik

    2017-01-01

    Density wave theory, originally proposed by C.C. Lin and Frank Shu (Lin & Shu 1964), views the spiral arm structures in spiral galaxies as density waves that propagates through the galactic disk. Resonances within orbits create standing wave patterns of density waves that we observe as spiral arms. The theory predicts the existence of a radius known as the co-rotation radius in which the spiral arm pattern speed matches the velocities of the stars within the disk. We introduce a novel way of determining the co-rotation radius, based on an image overlaying technique, which involves tracing the arms of spiral galaxies on images observed from different wavelengths. For the purpose of this study, 12 nearby galaxies were analyzed from four different wavelengths using pitch angle measurements from a previous study (Hamed et al. 2016). We used optical wavelength images (B-Band,440 nm), two infrared wavelength (Infrared; 3.6 µm and 8 µm) Spitzer Space Telescope images and ultraviolet images from GALEX. The results were verified by checking against results compiled from the literature.

  16. Quintessence-like dark matter in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Guzman, F. S.; Matos, T.; Nunez, D.; Ramirez, E.

    2003-06-01

    Through the geodesic analysis of a static and axially symmetric space time, we present conditions on the state equation of an isotropic perfect fluid p = omegad, when it is considered as the dark matter in spiral galaxies. The main conclusion is that it can be an exotic fluid (-1 < omega < -1/3) as it is found for Quintessence at cosmological scale.

  17. The Abundance and Chemical Evolution of Nitrogen in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Thurston, Tad Ralph

    1998-09-01

    The character of nitrogen processing in spiral galaxies is studied in this dissertation. Of particular interest are questions of how the (N/O) ratio changes over time as a result of perturbations of environmental parameters, as well as the importance of primary vs. secondary nitrogen generation and the regimes where one may be the preferred method. A robust numerical chemical evolution code (NICE) was written to model the change in elemental ratios during galactic chemical processing. This code is consistent with standard observational constraints. A new method is developed for the calculation of (N/O) abundances in the absence of observed temperature-diagnostic emission lines. New (N/O) abundances are derived for previously observed HII regions in spiral and dwarf galaxies, and the trends noted in the observations are modeled with the numeric code NICE. I conclude it is likely that early-type spirals once had a higher rate of infalling material relative to late-type galaxies, resulting in both a higher (N/O) ratio as well as a lower gas fraction during later epochs. NICE models also suggest that the star formation rate was suppressed in the extremely metal-poor stages of galaxy chemical processing, as shown by the model fits to the I Zw 18 regions as well as a highly redshifted primeval galaxy. Primary nitrogen production is only realized in stars of 4-8 solar masses, so that this is the first source of nitrogen after an episode of star formation. This is seen in both the observations and the models of low-metallicity dwarf galaxies. At later times, secondary nitrogen is released by stars in the lower mass range (1-4 solar masses), contributing to the steeper slope seen in (N/O) vs. OH for the more chemically advanced spiral galaxies.

  18. Logarithmic Spiral Arm Pitch Angle of Spiral Galaxies: Measurement and Relationship to Galactic Structure and Nuclear Supermassive Black Hole Mass

    NASA Astrophysics Data System (ADS)

    Davis, Benjamin

    In this dissertation, I explore the geometric structure of spiral galaxies and how the visible structure can provide information about the central mass of a galaxy, the density of its galactic disk, and the hidden mass of the supermassive black hole in its nucleus. In order to quantitatively measure the logarithmic spiral pitch angle (a measurement of tightness of the winding) of galactic spiral arms, I led an effort in our research group (the Arkansas Galaxy Evolution Survey) to modify existing two-dimensional fast Fourier transform software to increase its efficacy and accuracy. Using this software, I was able to lead an effort to calculate a black hole mass function (BHMF) for spiral galaxies in our local Universe. This work effectively provides us with a census of local black holes and establishes an endpoint on the evolutionary history of the BHMF for spiral galaxies. Furthermore, my work has indicated a novel fundamental relationship between the pitch angle of a galaxy's spiral arms, the maximum density of neutral atomic hydrogen in its disk, and the stellar mass of its bulge. This result provides strong support for the density wave theory of spiral structure in disk galaxies and poses a critical question of the validity of rival theories for the genesis of spiral structure in disk galaxies.

  19. Dynamics of stars around spiral arms in an N-body/SPH simulated barred spiral galaxy

    NASA Astrophysics Data System (ADS)

    Grand, Robert J. J.; Kawata, Daisuke; Cropper, Mark

    2012-10-01

    We run N-body smoothed particle hydrodynamics (SPH) simulations of a Milky Way-sized galaxy. The code takes into account hydrodynamics, self-gravity, star formation, supernova and stellar wind feedback, radiative cooling and metal enrichment. The simulated galaxy is a barred spiral galaxy consisting of a stellar and gas disc, enveloped in a static dark matter halo. Similar to what is found in our pure N-body simulation of a non-barred galaxy in Grand et al., we find that the spiral arms are transient features whose pattern speeds decrease with radius, in such a way that the pattern speed is similar to the rotation of star particles. Compared to the non-barred case, we find that the spiral arm pattern speed is slightly faster than the rotation speed of star particles: the bar appears to boost the pattern speed ahead of the rotational velocity. We trace particle motion around the spiral arms at different radii, and demonstrate that there are star particles that are drawn towards and join the arm from behind (in front of) the arm and migrate towards the outer (inner) regions of the disc until the arm disappears as a result of their transient nature. We see this migration over the entire radial range analysed, which is a consequence of the spiral arm rotating at similar speeds to star particles at all radii, which is inconsistent with the prediction of classical density wave theory. The bar does not prevent this systematic radial migration, which is shown to largely preserve circular orbits. We also demonstrate that there is no significant offset of different star-forming tracers across the spiral arm, which is also inconsistent with the prediction of classical density wave theory.

  20. Continuum observations of M 51 and M 83 at 1.1 mm with AzTEC

    NASA Astrophysics Data System (ADS)

    Wall, W. F.; Puerari, I.; Tilanus, R.; Israel, F. P.; Austermann, J. E.; Aretxaga, I.; Wilson, G.; Yun, M.; Scott, K. S.; Perera, T. A.; Roberts, C. M.; Hughes, D. H.

    2016-06-01

    We observed the spiral galaxies M 51 and M 83 at 20 arscec spatial resolution with the bolometer array Aztronomical Thermal Emission Camera (AzTEC) on the JCMT in the 1.1 mm continuum, recovering the extended emission out to galactocentric radii of more than 12 kpc in both galaxies. The 1.1 mm-continuum fluxes are 5.6 ± 0.7 and 9.9 ± 1.4 Jy, with associated gas masses estimated at 9.4 × 109 M⊙ and 7.2 × 109 M⊙ for M 51 and M 83, respectively. In the interarm regions of both galaxies, the N(H2)/I(CO) (or X-factor) ratios exceed those in the arms by factors of ˜1.5-2. In the inner discs of both galaxies, the X-factor is about 1 × 1020 cm- 2 (K km s- 1)- 1. In the outer parts, the CO-dark molecular gas becomes more important. While the spiral density wave in M 51 appears to influence the interstellar medium and stars in a similar way, the bar potential in M 83 influences the interstellar medium and the stars differently. We confirm the result of Foyle et al. that the arms merely heighten the star formation rate (SFR) and the gas surface density in the same proportion. Our maps reveal a threshold gas surface density for an SFR increase by two or more orders of magnitude. In both galaxy centres, the molecular gas depletion time is about 1 Gyr climbing to 10-20 Gyr at radii of 6-8 kpc. This is consistent with an inside-out depletion of the molecular gas in the discs of spiral galaxies.

  1. 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.

  2. THE MISSING GOLIATH'S SLINGSHOT: MASSIVE BLACK HOLE RECOIL AT M83

    SciTech Connect

    Dottori, Horacio; Diaz, Ruben J.; Facundo Albacete-Colombo, Juan

    2010-07-01

    The Fanaroff-Riley II radio source J133658.3-295105, which is also an X-ray source, appears to be projected onto the disk of the barred-spiral galaxy M83 at about 60'' from the galaxy's optical nucleus. J133658.3-295105 and its radio lobes are aligned with the optical nucleus of M 83 and two other radio sources, neither of which are supernova remnants or H II regions. Due to this peculiar on-the-sky projection, J133658.3-295105 was previously studied by Gemini+GMOS optical spectroscopy, which marginally revealed the presence of H{alpha} in emission receding at 130 km s{sup -1} with respect to the optical nucleus. In this Letter, we reanalyze the Chandra spectroscopy carried out in 2000. We show that J133658.3-295105 presents an Fe K{alpha} emission line at a redshift of z = 0.018. This redshift is compatible with a black hole at the distance of M 83. We discuss similarities to the recently reported micro-quasar in NGC 5408. This finding reinforces the kicked-off black hole scenario for J133658.3-295105.

  3. Neutral hydrogen and magnetic fields in M83 observed with the SKA Pathfinder KAT-7

    NASA Astrophysics Data System (ADS)

    Heald, G.; de Blok, W. J. G.; Lucero, D.; Carignan, C.; Jarrett, T.; Elson, E.; Oozeer, N.; Randriamampandry, T. H.; van Zee, L.

    2016-10-01

    We present new KAT-7 observations of the neutral hydrogen (H I) spectral line, and polarized radio continuum emission, in the grand-design spiral M83. These observations provide a sensitive probe of the outer-disc structure and kinematics, revealing a vast and massive neutral gas distribution that appears to be tightly coupled to the interaction of the galaxy with the environment. We present a new rotation curve extending out to a radius of 50 kpc. Based on our new H I data set and comparison with multiwavelength data from the literature, we consider the impact of mergers on the outer disc and discuss the evolution of M83. We also study the periphery of the H I distribution and reveal a sharp edge to the gaseous disc that is consistent with photoionization or ram pressure from the intergalactic medium. The radio continuum emission is not nearly as extended as the H I and is restricted to the main optical disc. Despite the relatively low angular resolution, we are able to draw broad conclusions about the large-scale magnetic field topology. We show that the magnetic field of M83 is similar in form to other nearby star-forming galaxies, and suggest that the disc-halo interface may host a large-scale regular magnetic field.

  4. 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.

  5. 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.

  6. 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.

  7. Photometric Asymmetry Between Clockwise and Counterclockwise Spiral Galaxies in SDSS

    NASA Astrophysics Data System (ADS)

    Shamir, Lior

    2017-02-01

    While galaxies with clockwise and counterclockwise handedness are visually different, they are expected to be symmetric in all of their other characteristics. Previous experiments using both manual analysis and machine vision have shown that the handedness of Sloan Digital Sky Survey galaxies can be predicted with accuracy significantly higher than mere chance using its photometric data alone. However, some of these previous experiments were based on manually classified galaxies, and the results may therefore be subjected to bias originated from the human perception. This paper describes an experiment based on a set of 162,514 galaxies classified automatically to clockwise and counterclockwise spiral galaxies, showing that the source of the asymmetry in Sloan Digital Sky Survey (SDSS) database is not the human perception bias. The results are compared to two smaller datasets, and confirm the observation that the handedness of SDSS galaxies can be predicted by their photometry. The experiment also shows statistically significant differences in the measured magnitude of SDSS galaxies, according which galaxies with clockwise patterns are brighter than galaxies with counterclockwise patterns. The magnitude of that difference changes across RA ranges, and exhibits a strong correlation with the cosine of the right ascension.

  8. 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.

  9. 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.

  10. Formation and evolution of spiral arms in galaxies orbiting a Virgo-like cluster

    NASA Astrophysics Data System (ADS)

    Semczuk, Marcin; Łokas, Ewa L.

    2017-03-01

    The origin of spiral structure in disks of galaxies remains an open question. One of the theories predicts that two-armed, grand design spiral arms originate from tidal interactions with another body. Using N-body simulations we find that a Milky Way-like galaxy can develop spiral arms due to tidal force from a cluster-size dark matter halo.

  11. SPIRAL FLOWS IN COOL-CORE GALAXY CLUSTERS

    SciTech Connect

    Keshet, Uri

    2012-07-10

    We argue that bulk spiral flows are ubiquitous in the cool cores (CCs) of clusters and groups of galaxies. Such flows are gauged by spiral features in the thermal and chemical properties of the intracluster medium, by the multiphase properties of CCs, and by X-ray edges known as cold fronts. We analytically show that observations of piecewise-spiral fronts impose strong constraints on the CC, implying the presence of a cold, fast flow, which propagates below a hot, slow inflow, separated by a slowly rotating, trailing, quasi-spiral, tangential discontinuity surface. This leads to the nearly logarithmic spiral pattern, two-phase plasma, {rho} {approx} r{sup -1} density (or T {approx} r{sup 0.4} temperature) radial profile, and {approx}100 kpc size, characteristic of CCs. By advecting heat and mixing the gas, such flows can eliminate the cooling problem, provided that a feedback mechanism regulates the flow. In particular, we present a quasi-steady-state model for an accretion-quenched, composite flow, in which the fast phase is an outflow, regulated by active galactic nucleus bubbles, reproducing the observed low star formation rates and explaining some features of bubbles such as their R{sub b} {proportional_to}r size. The simplest two-component model reproduces several key properties of CCs, so we propose that all such cores harbor a spiral flow. Our results can be tested directly in the next few years, for example by ASTRO-H.

  12. 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

  13. Global Modeling of Spur Formation in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Shetty, Rahul; Ostriker, Eve C.

    2006-08-01

    We investigate the formation of substructure in spiral galaxies using global MHD simulations, including gas self-gravity. Local modeling by Kim & Ostriker previously showed that self-gravity and magnetic fields cause rapid growth of overdensities in spiral arms; differential compression of gas flowing through the arms then results in the formation of sheared structures in the interarms. These sheared structures resemble features described as spurs or feathers in optical and IR observations of many spiral galaxies. Global modeling extends previous local models by including the full effects of curvilinear coordinates, a realistic log-spiral perturbation, self-gravitational contribution from five radial wavelengths of the spiral shock, and variation of density and epicyclic frequency with radius. We show that with realistic Toomre Q-values self-gravity and galactic differential rotation produce filamentary gaseous structures with kiloparsec-scale separations, regardless of the strength-or even presence-of a stellar spiral potential. However, a sufficiently strong spiral potential is required to produce true spurs, consisting of interarm structures emerging from gas concentrations in the main spiral arms. In models where Q is initially constant, filaments due to interarm self-gravity grow mainly in the outer regions, whereas true arm spurs grow only in the inner regions. For models with Q~R, outer regions are intrinsically more stable, so background interarm filaments do not grow, but arm spurs can develop if the spiral potential is strong. Unlike independently growing background filaments, the orientation of arm spurs depends on galactic location. Inside corotation, spurs emanate outward, on the convex side of the arm; outside corotation, spurs grow inward, on the concave side of the arm. Based on orientation and the relation to arm clumps, it is possible to distinguish true spurs that originate as instabilities in the arms from independently growing background

  14. Extended HI disks in nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Bosma, Albert

    2017-03-01

    In this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a ``tilted ring model'' allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both the MgI region and the CaII region.

  15. The varying mass distribution of molecular clouds across M83

    NASA Astrophysics Data System (ADS)

    Freeman, Pamela; Rosolowsky, Erik; Kruijssen, J. M. Diederik; Bastian, Nate; Adamo, Angela

    2017-06-01

    The work of Adamo et al. showed that the mass distributions of young massive stellar clusters were truncated above a maximum-mass scale in the nearby galaxy M83 and that this truncation mass varies with the galactocentric radius. Here, we present a cloud-based analysis of Atacama Large Millimeter/submillimeter Array CO(1 → 0) observations of M83 to search for such a truncation mass in the molecular cloud population. We identify a population of 873 molecular clouds in M83 that is largely similar to those found in the Milky Way and Local Group galaxies, though clouds in the centre of the galaxy show high surface densities and enhanced turbulence, as is common for clouds in high-density nuclear environments. Like the young massive clusters, we find a maximum-mass scale for the molecular clouds which decreases radially in the galaxy. We find that the most young massive cluster tracks the most massive molecular cloud with the cluster mass being 10-2 times that of the most massive molecular cloud. Outside the nuclear region of M83 (Rg > 0.5 kpc), there is no evidence for changing internal conditions in the population of molecular clouds, with the average internal pressures, densities and free-fall times remaining constant for the cloud population over the galaxy. This result is consistent with the bound cluster formation efficiency depending only on the large-scale properties of the interstellar medium rather than the internal conditions of individual clouds.

  16. 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

  17. Effects of Spiral Arms on Gaseous Structures and Mass Drift in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Kim, Yonghwi; Kim, Woong-Tae

    2015-01-01

    Stellar spiral arms play a key role in the formation and evolution of gaseous structures in disk galaxies as well as mass drift in the radial direction. Using hydrodynamic simulations, we investigate nonlinear responses of self-gravitating gas to an imposed stellar spiral potential in galactic disks. By considering various models with different arm strength and pattern speed, we find that the physical properties of imposed spiral potential have profound influences on the shapes and extent of gaseous arms as well as the related mass drift rate. To produce quasi-steady spiral shocks, the gas has to not only move faster than the local sound speed relative to the perturbing potential, but also have sufficient time to respond to one arm before encountering the next arm. From our numerical results, we provide a simple expression for the existence of quasi-steady spiral shocks depending on the pitch angle and pattern speed of stellar spiral arms, which appears consistent to the previous study. We also measure the mass drift rates which are in the range of ~0.5-3.0 M⊙/yr inside the corotation radius, and further quantify the relative contribution of shock dissipation (~50%), external torque (~40%), and self-gravitational torque (~10%) to them. The offset between the pitch angles of stellar and gaseous arms is larger for smaller arm strength and larger pattern speed, since a deeper potential tends to form shocks closer to the potential minima of the arms. We demonstrate that the distributions of line-of-sight velocities and spiral shock densities can be a diagnostic tool in distinguishing whether the spiral pattern rotates fast or not.

  18. An observational study of arm structure in normal spiral galaxies

    NASA Astrophysics Data System (ADS)

    Magri, Christopher

    Multivariate data were obtained and analyzed in an effort to develop a new classification system for spiral galaxies, one which is not necessarily based on morphological properties. By comparing morphological measures with the intrinsic parameters on which the new system is based, it can be seen just how fundamentally important a galactic property arm structure truly is. A sample of 492 moderately bright northern Sa, SBa, Sc, and SBc spirals was chosen for statistical analysis. The literature was searched for redshifts, optical and near-infrared photometric data, 20 cm fluxes, and H I 21 cm line parameters. New observations were made at 20 and 21 cm; in addition, IRAS fluxes were obtained from archival data. These data were subjected to principal component analysis, modified in that non-detections were explicitly acknowledged. Spiral galaxies have two fundamental properties, confirming previous work done with fewer data. While scale (bulk) is most important, galaxies of given scale can vary in form (color, bulge/disk ratio, H I surface density). Arm strength is unrelated to other properties. Forty-five spatially isolated spirals were chosen for two-color optical CCD imaging, for 20 cm continuum imaging, and for CO 2.6 mm spectroscopy. Isolated Sa's are often found to be misclassified; they are either armless SO's or else peculiar victims of collisions. Isolated Sc's are surprising in that all but the most isolated examples have symmetric arms over at least part of the disk, contrary to the predictions of stochastic models for arm formation. Given the extreme isolation of all highly chaotic disks, the presence of tidal companions (or at least candidates) for the other normal isolated spirals, the apparent prevalence of violent processes in isolated Sa's, and recent N-body simulations of tidal encounters, it is likely that arm structure in most spirals is produced by tidal encounters with small companions. Arm structure is not an intrinsic property of a given galaxy

  19. Spiral arms and disc stability in the Andromeda galaxy

    NASA Astrophysics Data System (ADS)

    Tenjes, P.; Tuvikene, T.; Tamm, A.; Kipper, R.; Tempel, E.

    2017-03-01

    Aims: Density waves are often considered as the triggering mechanism of star formation in spiral galaxies. Our aim is to study relations between different star formation tracers (stellar UV and near-IR radiation and emission from H i, CO, and cold dust) in the spiral arms of M 31, to calculate stability conditions in the galaxy disc, and to draw conclusions about possible star formation triggering mechanisms. Methods: We selected fourteen spiral arm segments from the de-projected data maps and compared emission distributions along the cross sections of the segments in different datasets to each other, in order to detect spatial offsets between young stellar populations and the star-forming medium. By using the disc stability condition as a function of perturbation wavelength and distance from the galaxy centre, we calculated the effective disc stability parameters and the least stable wavelengths at different distances. For this we used a mass distribution model of M 31 with four disc components (old and young stellar discs, cold and warm gaseous discs) embedded within the external potential of the bulge, the stellar halo, and the dark matter halo. Each component is considered to have a realistic finite thickness. Results: No systematic offsets between the observed UV and CO/far-IR emission across the spiral segments are detected. The calculated effective stability parameter has a lowest value of Qeff ≃ 1.8 at galactocentric distances of 12-13 kpc. The least stable wavelengths are rather long, with the lowest values starting from ≃ 3 kpc at distances R > 11 kpc. Conclusions: The classical density wave theory is not a realistic explanation for the spiral structure of M 31. Instead, external causes should be considered, such as interactions with massive gas clouds or dwarf companions of M 31.

  20. 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.

  1. Diffuse hot gas in nearby face-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Doane, Nathaniel

    2007-08-01

    We present a study of the diffuse thermal emission in three nearby, face-on spiral galaxies, NGC 3631, NGC 628 and NGC 3184, using X-ray data from the Chandra X-ray Observatory and optical data from the WIYN observatory. We are able to separate out the X-ray emission from unresolved point sources from the total unresolved emission in order to study the truly diffuse X-ray emission. We find that in all cases, the spectrum of the hot gas is well fit using a two thermal-component model. In the three galaxies, we find a strong correlation between the X-ray surface brightness and regions of star formation. We also estimate the electron density, pressure and cooling time of the hot gas, finding that the pressure of the hot gas in these three galaxies is higher than the ambient Milky Way pressure. In addition to the standard two temperature spectral model of the hot-gas emission from spiral galaxies, we show a model with the hot gas at a continuum of temperatures provides an equally good fit and a more physical description of the gas. Finally, we discuss the Chandra ACIS background and our method of spectrally modeling it. We also present plots of all our spectral fits to each galaxy and its sub-regions using our background model.

  2. Feeding IC 342: The nuclear spiral of a starburst galaxy

    NASA Technical Reports Server (NTRS)

    Levine, D.; Turner, J. L.; Hurt, Robert L.

    1993-01-01

    IC 342 is a large nearby (1.8 Mpc, Turner and Hurt, 1991, hereafter T&H) spiral galaxy undergoing a moderate nuclear starburst. T&H have previously mapped the inner arcminute in CO-13(1-0) using the Owens Valley Millimeter Interferometer and found evidence that the nuclear molecular gas takes the form of spiral arms in a density wave pattern. They suggest that radial streaming along the arms may channel gas from the exterior of the galaxy into the nucleus, feeding the starburst. We have mapped the CO-12(1-0) emission of the inner 2 kpc of IC 342 at 2.8 inch resolution using the Owens Valley Radio Observatory (OVRO) Millimeter Interferometer. The greater sensitivity of CO-12 observations has allowed us to trace the spiral pattern out to a total extent of greater than 1 kpc. The CO-12 observations extend considerably the structure observed at CO-13 and offer further evidence that a spiral density wave may extend from the disk into the nucleus of IC 342.

  3. Feeding IC 342: The nuclear spiral of a starburst galaxy

    NASA Astrophysics Data System (ADS)

    Levine, D.; Turner, J. L.; Hurt, Robert L.

    1993-01-01

    IC 342 is a large nearby (1.8 Mpc, Turner and Hurt, 1991, hereafter T&H) spiral galaxy undergoing a moderate nuclear starburst. T&H have previously mapped the inner arcminute in CO-13(1-0) using the Owens Valley Millimeter Interferometer and found evidence that the nuclear molecular gas takes the form of spiral arms in a density wave pattern. They suggest that radial streaming along the arms may channel gas from the exterior of the galaxy into the nucleus, feeding the starburst. We have mapped the CO-12(1-0) emission of the inner 2 kpc of IC 342 at 2.8 inch resolution using the Owens Valley Radio Observatory (OVRO) Millimeter Interferometer. The greater sensitivity of CO-12 observations has allowed us to trace the spiral pattern out to a total extent of greater than 1 kpc. The CO-12 observations extend considerably the structure observed at CO-13 and offer further evidence that a spiral density wave may extend from the disk into the nucleus of IC 342.

  4. Enhanced star formation: The importance of bars in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Puxley, P. J.; Hawarden, T. G.; Mountain, C. M.; Leggett, S. K.

    1987-01-01

    It was found that among an IR luminous subset of nearby spiral galaxies, nearly all of the systems with IRAS colors and luminosities indicative of enhanced star formation are barred. Radio continuum and IR spectroscopic results support the hypothesis that this emission originates within the central 2 kpc; possibly in a circumnuclear ring. It was also found that outer rings are over represented among these barred systems and suggest possible reasons for this phenomena.

  5. The relationship between polycyclic aromatic hydrocarbon emission and far-infrared dust emission from NGC 2403 and M83

    NASA Astrophysics Data System (ADS)

    Jones, A. G.; Bendo, G. J.; Baes, M.; Boquien, M.; Boselli, A.; De Looze, I.; Fritz, J.; Galliano, F.; Hughes, T. M.; Lebouteiller, V.; Lu, N.; Madden, S. C.; Rémy-Ruyer, A.; Smith, M. W. L.; Spinoglio, L.; Zijlstra, A. A.

    2015-03-01

    We examine the relation between polycyclic aromatic hydrocarbon (PAH) emission at 8 μm and far-infrared emission from hot dust grains at 24 μm and from large dust grains at 160 and 250 μm in the nearby spiral galaxies NGC 2403 and M83 using data from the Spitzer Space Telescope and Herschel Space Observatory. We find that the PAH emission in NGC 2403 is better correlated with emission at 250 μm from dust heated by the diffuse interstellar radiation field (ISRF) and that the 8/250-μm surface brightness ratio is well correlated with the stellar surface brightness as measured at 3.6 μm. This implies that the PAHs in NGC 2403 are intermixed with cold large dust grains in the diffuse interstellar medium (ISM) and that the PAHs are excited by the diffuse ISRF. In M83, the PAH emission appears more strongly correlated with 160 μm emission originating from large dust grains heated by star-forming regions. However, the PAH emission in M83 is low where the 24-μm emission peaks within star-forming regions, and enhancements in the 8/160-μm surface brightness ratios appear offset relative to the dust and the star-forming regions within the spiral arms. This suggests that the PAHs observed in the 8 μm band are not excited locally within star-forming regions but either by light escaping non-axisymmetrically from star-forming regions or locally by young, non-photoionizing stars that have migrated downstream from the spiral density waves. The results from just these two galaxies show that PAHs may be excited by different stellar populations in different spiral galaxies.

  6. 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.

  7. Relaxation and Thermalization in Spiral Galaxies Mediated by Spiral Wave Scattering

    NASA Astrophysics Data System (ADS)

    Hohlfeld, R. G.; Shalit, D.; Comins, N. F.; Sandri, G. V. H.

    1993-12-01

    We have constructed N-body particle-mesh simulations of disk galaxies in which the relaxation times of the simulated disks (as measured by thermalization of the disk, i.e. increase in Toomre's Q parameter) is comparable to the actual relaxation time scale in actual disk galaxies (several tens of rotation periods). These simulations require 1M to 4M particles (1M = 2(20) ), consistent with the work of White and of Comins and Schroeder on the dependence of relaxation time on N. We observe that during the interval when Q is increasing, that the Fourier power associated with spiral modes is large. When Q has risen to its asymptotic value in the simulation, the Fourier power diminishes to a low level. This suggests a scenario in which stars (simulation particles) scatter off the time-varying spiral potential, as suggested by Carlberg and Sellwood. Eventually random velocities of stars increase to a value which quenches the spiral instability. We compare the heating rates in our simulations at observed spiral wave amplitudes to the expected growth rates as given by Carlberg and Sellwood.

  8. STAR FORMATION EFFICIENCY IN THE BARRED SPIRAL GALAXY NGC 4303

    SciTech Connect

    Momose, Rieko; Okumura, Sachiko K.; Sawada, Tsuyoshi; Koda, Jin E-mail: sokumura@nro.nao.ac.j E-mail: Jin.Koda@stonybrook.ed

    2010-09-20

    We present new {sup 12}CO (J = 1 - 0) observations of the barred galaxy NGC 4303 using the Nobeyama 45 m telescope (NRO45) and the Combined Array for Research in Millimeter-wave Astronomy (CARMA). The H{alpha} images of barred spiral galaxies often show active star formation in spiral arms, but less so in bars. We quantify the difference by measuring star formation rate (SFR) and star formation efficiency (SFE) at a scale where local star formation is spatially resolved. Our CO map covers the central 2.'3 region of the galaxy; the combination of NRO45 and CARMA provides a high fidelity image, enabling accurate measurements of molecular gas surface density. We find that SFR and SFE are twice as high in the spiral arms as in the bar. We discuss this difference in the context of the Kennicutt-Schmidt (KS) law, which indicates a constant SFR at a given gas surface density. The KS law breaks down at our native resolution ({approx}250 pc), and substantial smoothing (to 500 pc) is necessary to reproduce the KS law, although with greater scatter.

  9. The Ultraviolet Attenuation Law in Backlit Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Keel, William C.; Manning, Anna M.; Holwerda, Benne W.; Lintott, Chris J.; Schawinski, Kevin

    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. Atomic hydrogen in the spiral galaxy NGC 3631

    NASA Astrophysics Data System (ADS)

    Knapen, J. H.

    1997-04-01

    New high-resolution, high-sensitivity Westerbork Synthesis Radio Telescope Hi synthesis observations of the spiral galaxy NGC 3631 are presented. In the total atomic hydrogen map, the spiral arms are well distinguished from the interarm regions, while the sensitivity allows detection of Hi in all but a few isolated regions of the areas between the spiral arms. Most of the atomic hydrogen is located within the optical disc, but the Hi extends to some 1.5R_opt. The Hi follows the spiral arms, and streaming motions of up to ~15 km s^-1 (projected) can be identified from the velocity field. Assuming a constant inclination angle of 17 deg, a rotation curve is derived which is declining slightly in the outer parts of the disc. An analysis of a residual velocity field, obtained after the subtraction of an axisymmetric model based on the rotation curve, confirms the existence of streaming motions near the spiral arms in an otherwise undisturbed disc.

  11. Flocculent and grand design spiral structure in field, binary and group galaxies

    NASA Astrophysics Data System (ADS)

    Elmegreen, D. M.; Elmegreen, B. G.

    1982-12-01

    A 12-division morphological system emphasizing arm continuity, length and symmetry has been developed for the classification of all spiral galaxies according to the regularity of their spiral arm structure. Arm classifications were tabulated for 305 barred and nonbarred spiral galaxies; of these, 79 are isolated, 52 are binary and 174 are in groups. Among the isolated SA galaxies, 68 + or - 10% have irregular and fragmented, or 'flocculent', spiral structures. Only 32 + or - 10% have symmetric spiral arms in the classic grand design pattern. Flocculent spirals are the most common structures of galaxies without companions or bars. Since flocculent galaxies may have bars and companions, and grand design galaxies may have neither bars nor companions, such perturbations are neither perfectly effective nor always necessary in the driving of grand design patterns.

  12. 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.

  13. Hubble Peers at the Heart of a Spiral Galaxy

    NASA Image and Video Library

    2017-09-27

    This new Hubble image is centered on NGC 5793, a spiral galaxy over 150 million light-years away in the constellation of Libra. This galaxy has two particularly striking features: a beautiful dust lane and an intensely bright center — much brighter than that of our own galaxy, or indeed those of most spiral galaxies we observe. NGC 5793 is a Seyfert galaxy. These galaxies have incredibly luminous centers that are thought to be caused by hungry supermassive black holes — black holes that can be billions of times the size of the sun — that pull in and devour gas and dust from their surroundings. This galaxy is of great interest to astronomers for many reasons. For one, it appears to house objects known as masers. Whereas lasers emit visible light, masers emit microwave radiation. The term "masers" comes from the acronym Microwave Amplification by Stimulated Emission of Radiation. Maser emission is caused by particles that absorb energy from their surroundings and then re-emit this in the microwave part of the spectrum. Naturally occurring masers, like those observed in NGC 5793, can tell us a lot about their environment; we see these kinds of masers in areas where stars are forming. In NGC 5793 there are also intense mega-masers, which are thousands of times more luminous than the sun. Credit: NASA, ESA, and E. Perlman (Florida Institute of Technology) NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  14. 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

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Photometric and kinematic DISKFIT models of four nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Peters, Wesley; Kuzio de Naray, Rachel

    2017-08-01

    We present optical BVRI photometry, H α integrated field unit velocity fields and H α long-slit rotation curves for a sample of four nearby spiral galaxies having a range of morphologies and inclinations. We show that the DISKFIT code can be used to model the photometric and kinematic data of these four galaxies and explore how well the photometric data can be decomposed into structures like bars and bulges and to look for non-circular motions in the kinematic data. In general, we find good agreement between our photometric and kinematic models for most parameters. We find the best consistency between our photometric and kinematic models for NGC 6674, a relatively face-on spiral with clear and distinct bulge and bar components. We also find excellent consistency for NGC 2841, and find a bar ∼10° south of the disc major axis in the inner 20 arcsec. Due to geometric effects caused by its high inclination, we find the kinematic model for NGC 2654 to be less accurate than its photometry. We find the bar in NGC 2654 to be roughly parallel to the major axis of the galaxy. We are unable to photometrically model our most highly inclined galaxy, NGC 5746, with DISKFIT and instead use the galaxy isophotes to determine that the system contains a bar ∼5° to ∼10° east of the disc major axis. The high inclination and extinction in this galaxy also prevent our kinematic model from accurately determining parameters about the bar, though the data are better modelled when a bar is included.

  1. 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.

  2. Hot X-ray Coronae around Spiral Galaxies: A Unique Probe of Galaxy Formation Models

    NASA Astrophysics Data System (ADS)

    Bogdan, Akos; Concepcion Mairey, Florence; Bourdin, Herve; Forman, William R.; Kraft, Ralph P.; Vogelsberger, Mark; Hernquist, Lars E.; Jones, Christine

    2017-08-01

    The presence of hot gaseous coronae in the dark matter halos of massive spiral galaxies is a fundamental prediction of all galaxy formation models. Yet these coronae remained unexplored for several decades, thereby posing a serious challenge to observers and theorists. Recently, a major breakthrough has been made, and several X-ray coronae have been detected around massive spiral galaxies. We have studied the properties of these luminous X-ray coronae in detail and confronted their observed properties with results of the hydrodynamical galaxy formation simulation, Illustris. This comparison pointed out that the properties of these coronae are extremely sensitive to the incorporated physics in the simulations, and hence observations of X-ray coronae provide a powerful method to constrain the physical processes (e.g. stellar and AGN feedback and metal enrichment) that play an essential role in forming galaxies from the early Universe to the present epoch. I will overview the key observational results, discuss the comparison between observations and simulations, and highlight the future prospects of further exploring hot coronae around spiral galaxies.

  3. Radio continuum and H I emission from the spiral galaxies in the Virgo cluster area

    NASA Astrophysics Data System (ADS)

    Gavazzi, G.

    The statistical method used by Hummel (1981) to derive the radioluminosity functions of galaxies is applied to the H I data obtained on a sample of 101 spiral galaxies in the Virgo cluster. The analysis permits a quantitative demonstration of H I deficiency among the Virgo spiral galaxies without invoking the deficiency parameter. In addition, evidence is presented that Virgo spiral galaxies might show a correlation between H I content and radio continuum luminosity, which is more marked among the unperturbed sample. The results are discussed from the viewpoint of stellar and galaxy evolution and its relation with the intergalactic environment.

  4. 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.

  5. Constraining corotation from shocks in tightly wound spiral galaxies

    NASA Astrophysics Data System (ADS)

    Gittins, D. M.; Clarke, C. J.

    2004-04-01

    We present a new method for estimating the corotation radius in tightly wound spiral galaxies, through analysis of the radial variation of the offset between arms traced by the potential (P-arms) and those traced by dust (D-arms). We have verified the predictions of semi-analytical theory through hydrodynamical simulations and have examined the uniqueness of the galactic parameters that can be deduced by this method. We find that if the range of angular offsets measured at different radii in a galaxy is greater than around π/4, it is possible to locate the radius of corotation to within ~25 per cent. We argue that the relative location of the P- and D-arms provides more robust constraints on the galactic parameters than can be inferred from regions of enhanced star formation (SF-arms), as interpretation of the latter involves uncertainties due to reddening and the assumed star formation law. We thus stress the importance of K-band studies of spiral galaxies.

  6. Does the Milky Way Obey Spiral Galaxy Scaling Relations?

    NASA Astrophysics Data System (ADS)

    Licquia, Timothy C.; Newman, Jeffrey A.; Bershady, Matthew A.

    2016-12-01

    It is crucial to understand how the Milky Way (MW), the galaxy we can study in the most intimate detail, fits in among other galaxies. Key considerations include the Tully-Fisher relation (TFR)—i.e., the tight correlation between luminosity (L) and rotational velocity (V rot)—and the three-dimensional luminosity-velocity-radius (LVR) scaling relation. Several past studies have characterized the MW as a 1-1.5σ outlier to the TFR. This study re-examines such comparisons using new estimates of MW properties that are robust to many of the systematic uncertainties that have been a problem in the past and are based on assumptions consistent with those used for other spiral galaxies. Comparing to scaling relations derived from modern extragalactic data, we find that our Galaxy’s properties are in excellent agreement with TFRs defined using any Sloan Digital Sky Survey-filter absolute magnitude, stellar mass, or baryonic mass as the L proxy. We next utilize disk scale length (R d) measurements to extend this investigation to the LVR relation. Here we find that our Galaxy lies farther from the relation than ˜90% of other spiral galaxies, yielding ˜9.5σ evidence that it is unusually compact for its L and V rot (based on MW errors alone), a result that holds for all of the L proxies considered. The expected R d for the MW from the LVR relation is ˜5 kpc, nearly twice as large as the observed value, with error estimates placing the two in tension at the ˜1.4σ level. The compact scale length of the Galactic disk could be related to other ways in which the MW has been found to be anomalous.

  7. 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

  8. 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.

  9. The radio luminosity function of spiral galaxies - Correlations with aggregation and Hubble type

    NASA Astrophysics Data System (ADS)

    Gavazzi, G.; Trinchieri, G.

    1981-04-01

    The Radio Luminosity Function of spiral galaxies is derived from the Arecibo observations of UGC galaxies at 2380 MHz. It is found that the average radio power and the optical luminosity are linearly correlated (αL1) and that, at any given radio power, the probability for a spiral galaxy to become a radio source scales with the optical luminosity as L1.3. Both results confirm the analysis of Hummel (1980, b) who studied with the Westerbork radio telescope (WSRT) the 1415 MHz continuum emission from nearby spiral galaxies. It is also attempted to correlate the radio emission from spiral galaxies with their detailed Hubble type and cluster membership. A weak evidence is found that early type galaxies and cluster members are slightly deficient in radio emission with respect to late type or isolated galaxies, particularly among the optically brightest objects.

  10. On the Extraction of Optical Rotation Curves for Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Sohn, Young-Jong; Rhee, Myung-Hyun; Chun, Mun-Suk

    1998-06-01

    We discussed four different methods - the single, double and triple Gaussian fits, and the intensity weighted centroid fit - which extract rotation curves from several emission lines ([OII], H_beta, [OIII], and H_alpha) of spiral galaxies. Spatial extents and the shapes of rotation curves derived through various methods applying to each emission lines of a sample galaxy UGC 11635 are all in a good agreement with one another. Linewidths of H_beta and H_alpha measured from rotation profiles are in a good agreement with H_alpha linewidth of Courteau (1992). However, linewidths of [OII] seems to be much broader than H_alpha, and the profile of [OIII] does not follow the profile of H_alpha.

  11. 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.

  12. Arm structure in normal spiral galaxies, 1: Multivariate data for 492 galaxies

    NASA Technical Reports Server (NTRS)

    Magri, Christopher

    1994-01-01

    Multivariate data have been collected as part of an effort to develop a new classification system for spiral galaxies, one which is not necessarily based on subjective morphological properties. A sample of 492 moderately bright northern Sa and Sc spirals was chosen for future statistical analysis. New observations were made at 20 and 21 cm; the latter data are described in detail here. Infrared Astronomy Satellite (IRAS) fluxes were obtained from archival data. Finally, new estimates of arm pattern radomness and of local environmental harshness were compiled for most sample objects.

  13. Arm structure in normal spiral galaxies, 1: Multivariate data for 492 galaxies

    NASA Technical Reports Server (NTRS)

    Magri, Christopher

    1994-01-01

    Multivariate data have been collected as part of an effort to develop a new classification system for spiral galaxies, one which is not necessarily based on subjective morphological properties. A sample of 492 moderately bright northern Sa and Sc spirals was chosen for future statistical analysis. New observations were made at 20 and 21 cm; the latter data are described in detail here. Infrared Astronomy Satellite (IRAS) fluxes were obtained from archival data. Finally, new estimates of arm pattern radomness and of local environmental harshness were compiled for most sample objects.

  14. Broad-band BVRI photometry of isolated spiral galaxies

    NASA Astrophysics Data System (ADS)

    Hernández-Toledo, H. M.; Ortega-Esbrí, S.

    2008-08-01

    Context: Uniform and high resolution observations in samples of isolated galaxies are required to estimate fundamental morphological and structural parameters for comparative studies of environmental effects and for confronting model predictions of galaxy evolution. A subsample of The Catalog of Isolated Galaxies (CIG), Karachentseva (1973), has been uniformly observed at San Pedro Mártir National Observatory in México and a photometric and morphological study of these galaxies has been carried out. Aims: We report multicolor broad band (BVRI) photometry for a subsample of 40 isolated spirals drawn from the CIG. Total magnitudes and colors at various circular apertures as well as a detailed morphological analysis that is extended into the NIR bands are presented. Some structural parameters are estimated from the global light distribution in the optical and NIR bands to complement our morphological analysis and several correlations between the photometric and structural parameters are explored. Emphasis was given to the detection of morphological distortions at high/low intensity levels. Methods: The observations, data reduction, and analysis are described. Morphology is reevaluated from a combination of optical logarithmically scaled R band images, filter-enhanced R band images, (B-I) color index maps, archived near IR {JHK} images from the TwoMicron Survey and optical-NIR ɛ and PA radial profiles after an isophotal analysis. {RGB} images from the SDSS database were retrieved when available to complement our analysis. The {CAS} structural parameters (Concentration, Asymmetry, and Clumpiness) were calculated from the images in each band. Results: The fraction of galaxies with well-identified optical/near-IR bars (SB) is 40%, while another 25% shows evidence of weak or suspected bars (SAB). The sample average value of the maximum bar ellipticity is ɛ_max≈ 0.35. 57.5% of the galaxies in the sample show rings. The {CAS} parameters change with the observed band

  15. THE LARSON-TINSLEY EFFECT IN THE ULTRAVIOLET: INTERACTING VERSUS 'NORMAL' SPIRAL GALAXIES

    SciTech Connect

    Smith, Beverly J.; Struck, Curtis E-mail: curt@iastate.ed

    2010-12-15

    We compare the UV-optical colors of a well-defined set of optically selected pre-merger interacting galaxy pairs with those of normal spirals. The shorter wavelength colors show a larger dispersion for the interacting galaxies than for the spirals. This result can best be explained by higher star formation rates on average in the interacting galaxies, combined with higher extinctions on average. This is consistent with earlier studies which found that the star formation in interacting galaxies tends to be more centrally concentrated than in normal spirals, perhaps due to gas being driven into the center by the interaction. As noted in earlier studies, there is a large variation from galaxy to galaxy in the implied star formation rates of the interacting galaxies, with some galaxies having enhanced rates but others being fairly quiescent.

  16. Galaxy Zoo: comparing the demographics of spiral arm number and a new method for correcting redshift bias

    NASA Astrophysics Data System (ADS)

    Hart, Ross E.; Bamford, Steven P.; Willett, Kyle W.; Masters, Karen L.; Cardamone, Carolin; Lintott, Chris J.; Mackay, Robert J.; Nichol, Robert C.; Rosslowe, Christopher K.; Simmons, Brooke D.; Smethurst, Rebecca J.

    2016-10-01

    The majority of galaxies in the local Universe exhibit spiral structure with a variety of forms. Many galaxies possess two prominent spiral arms, some have more, while others display a many-armed flocculent appearance. Spiral arms are associated with enhanced gas content and star formation in the discs of low-redshift galaxies, so are important in the understanding of star formation in the local universe. As both the visual appearance of spiral structure, and the mechanisms responsible for it vary from galaxy to galaxy, a reliable method for defining spiral samples with different visual morphologies is required. In this paper, we develop a new debiasing method to reliably correct for redshift-dependent bias in Galaxy Zoo 2, and release the new set of debiased classifications. Using these, a luminosity-limited sample of ˜18 000 Sloan Digital Sky Survey spiral galaxies is defined, which are then further sub-categorized by spiral arm number. In order to explore how different spiral galaxies form, the demographics of spiral galaxies with different spiral arm numbers are compared. It is found that whilst all spiral galaxies occupy similar ranges of stellar mass and environment, many-armed galaxies display much bluer colours than their two-armed counterparts. We conclude that two-armed structure is ubiquitous in star-forming discs, whereas many-armed spiral structure appears to be a short-lived phase, associated with more recent, stochastic star-formation activity.

  17. NIR surface photometry of a sample of nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Castro-Rodríguez, N.; Garzón, F.

    2003-11-01

    The first results of an observational programme aimed at mapping a sample of face-on spiral galaxies in the NIR are presented. This paper shows the surface photometry of the first ten galaxies in the sample. The data were taken in the broad band J (1.2 mu m) and Ks (2.2 mu m) filters. The sources were selected mainly according to their size and brightness in order to suit the characteristics of the CAIN 2D NIR camera on the 1.5-m Carlos Sánchez Telescope (Tenerife, Spain). The primary scientific goal is to provide a comprehensive and uniform database of the main structural and photometric parameters of the sample members from NIR surface photometry. To this end, elliptical isophotal fitting was performed on each galaxy image to extract information about the size and location of its morphological components and provide the azimuthally averaged radial brightness profile. Analytical functions for each component's brightness distribution were then used to match that profile, and their functional parameters obtained from the global fitting. This first report includes data for NGC 3344, NGC 3686, NGC 3938, NGC 3953, NGC 4254, NGC 4303, NGC 4314, NGC 5248, NGC 6384 and NGC 7479.

  18. ON THE STAR FORMATION LAW FOR SPIRAL AND IRREGULAR GALAXIES

    SciTech Connect

    Elmegreen, Bruce G.

    2015-12-01

    A dynamical model for star formation on a galactic scale is proposed in which the interstellar medium is constantly condensing to star-forming clouds on the dynamical time of the average midplane density, and the clouds are constantly being disrupted on the dynamical timescale appropriate for their higher density. In this model, the areal star formation rate scales with the 1.5 power of the total gas column density throughout the main regions of spiral galaxies, and with a steeper power, 2, in the far outer regions and in dwarf irregular galaxies because of the flaring disks. At the same time, there is a molecular star formation law that is linear in the main and outer parts of disks and in dIrrs because the duration of individual structures in the molecular phase is also the dynamical timescale, canceling the additional 0.5 power of surface density. The total gas consumption time scales directly with the midplane dynamical time, quenching star formation in the inner regions if there is no accretion, and sustaining star formation for ∼100 Gyr or more in the outer regions with no qualitative change in gas stability or molecular cloud properties. The ULIRG track follows from high densities in galaxy collisions.

  19. BCD Galaxies from In-spiraling Giant Clumps

    NASA Astrophysics Data System (ADS)

    Elmegreen, Bruce; Zhang, H.; Hunter, D. A.

    2012-01-01

    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 center in less than 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 analogous to a bulge in an earlier-type galaxy. A long history of inward migration will also produce a long-lived starburst in the inner regions as the gas column density remains above a threshold for star formation. Such a burst may be identified with the BCD phase in some dwarfs. Observations of giant star formation clumps in five local dwarf irregulars illustrate the relatively large clump masses that are suggested by this process. The observed clumps also seem to contain old field stars, even after background light subtraction, in which case they may be gravitationally bound and long-lived. The two examples with clumps closest to the center have the largest relative clump masses and the greatest contributions from old stars. This work was funded in part by the National Science Foundation through grants AST-0707563 and AST-0707426 to DAH and BGE. HZ was partly supported by NSF of China through grants #10425313, #10833006 and #10621303 to Professor Yu Gao.

  20. The Arkansas Galaxy Evolution Survey: SMBH Mass and Spiral Arm Morphology

    NASA Astrophysics Data System (ADS)

    Seigar, M. S.; Berrier, J. C.; Davis, B. L.; Kennefick, D.; Kennefick, J.; Barrows, R. S.; Hartley, M. T.; Shields, D. W.; Bentz, M. C.; Lacy, C. H. S.

    2014-03-01

    We confirm the existence of a previously reported relationship between spiral arm pitch angle P (a measure of the tightness of spiral structure) and the mass MBH of a disk galaxy's central supermassive black hole (SMBH). We use an improved method to determine spiral arm pitch angles and generate quantitative data on this morphological feature for 34 galaxies with directly measured black hole masses, and a further 20 galaxies with measured core velocity dispersions. Such a relationship is predicted by leading theories of spiral structure (density wave theory, swing amplification, and manifold theory). We propose that this relationship be used as a method for estimating SMBH masses in disk galaxies. Spiral arm pitch angle can be measured from imaging data alone, and with the scatter in the presented relationship (0.45 dex), this tool is potentially superior when compared to other SMBH scaling relationship.

  1. Satellites as Probes of the Masses of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Gottesman, S. T.

    1998-11-01

    We discuss HI observations and analyses of the kinematics of 25 satellite-primary galaxy pairs with projected separations between 4.9 and 240 kpc. The satellites have masses less than 3% of their primary spirals. Two estimates for their mass are available, one from their rotation curves and one from the orbital properties of the satellites. Defining \\chi as the ratio of these two estimates, it is a measure of the presence or absence of a significant halo. The \\chi distribution of these 24 pairs is presented and selection effects are considered. In addition, we show that the \\chi distribution of more numerous pairs, with projected separations of less thn 200 kpc, identified by Zartisky and colleagues (employing selection criteria quite different than ours) is similar to ours. We show that the observational biases have a negligible effect; the biased and unbiased distributions are essentially identical. In order to understand this distribution, N-body calculations were executed to simulate the dynamical behavior of relatively low mass satellites orbiting primary disk galaxies with and without extended halos. The models and the real galaxies were 'obseved' in the same fasion. In adition, we made a partially analytical analysis of the behavior of orbits in a logarithmic potential. We find that a 'generic' model, characterizd by a single disk/halo combination, cannot reproduce the observed distribution, P(\\chi). 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 200kpc. If galaxies are considerably larger with sizes extending 400 kpc or more, the constraints become more onerous. 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, nether pure halo, nor cannonical models (disk and halo masses are

  2. Statistical study of warps in a sample of spiral and lenticular galaxies

    NASA Astrophysics Data System (ADS)

    Hendy, Y. H. M.; Samir, R. M.; Shaker, A. A.; Ibrahim, Alhassan I.

    2016-12-01

    A sample of edge-on (or nearly edge-on) spiral and lenticular galaxies is selected to study the warp phenomenon in their disks. This sample contains 36 disk galaxies selected from Watanabe's catalogue (Watanabe, 1983). We investigate the existence of physical relations between photometric and spectroscopic parameters and the warp degree of galaxies.

  3. Effects of interaction on the properties of spiral galaxies. II. Isolated galaxies: The zero point

    NASA Astrophysics Data System (ADS)

    Márquez, I.; Moles, M.

    1999-04-01

    We analyse the properties of a sample of 22 bright isolated spiral galaxies on the basis of Johnson B,V,I images and optical rotation curves. The fraction of early morphological types in our sample of isolated galaxies (or in other samples of non-interacting spiral galaxies) appears to be smaller than in samples including interacting systems. The overall morphological aspect is regular and symmetric, but all the galaxies present non-axisymmetric components in the form of bars or rings. We find that the color indices become bluer towards the outer parts and that their central values are well correlated with the total colors. The properties of the bulges span a larger range than those of the disks, that thus are more alike between them. None of the galaxies shows a truncated, type II disk profile. It is found that the relation between surface brightness and size for the bulges, the Kormendy relation, is tighter when only isolated galaxies are considered. We find a similar relation for the disk parameters with an unprecedented low scatter. A Principal Component Analysis of the measured parameters shows that 2 eigenvectors suffice to explain more than 95 % of the total variance. These are, as found for other samples including spiral galaxies in different environmental situations, a scale parameter given by the mass or, equivalently, the luminosity or the size; and a form parameter given by the bulge to disk luminosity ratio, B/D, or, equivalently, by the gradient of the solid-body rotation region of the rotation curve, the G-parameter. We report here a tight correlation between G and B/D for our sample of isolated spirals that could be used as a new distance indicator. Based on data obtained at the 1.5m telescope of the Estacion de Observacion de Calar Alto, Instituto Geografico Nacional, which is jointly operated by the Instituto Geografico Nacional and the Consejo Superior de Investigaciones Cientificas through the Instituto de Astrofisica de Andalucia

  4. Velocity dispersions in the bulges of spiral and S0 galaxies. II Further observations and a simple three-component model for spiral galaxies

    NASA Astrophysics Data System (ADS)

    Whitmore, B. C.; Kirshner, R. P.

    1981-11-01

    We have obtained velocity dispersions for 24 galaxies in the Virgo cluster to supplement our earlier results. A 2000 channel intensified Reticon scanner has again been used on the 1.3 m telescope of McGraw-Hill Observatory, and a Fourier quotient technique has been employed to yield dispersions. We have confirmed our earlier result that spiral bulges exhibit a relation between total luminosity and velocity dispersion with the form L ∝ σ4, but with velocity dispersions that are 17 ± 8% smaller than elliptical galaxies at the same absolute magnitude. However, possible systematic errors may still affect the reality of this gap. The scatter in the L ∝ σ4 relationship is substantially larger for the spiral bulges than for the elliptical galaxies. This larger scatter probably indicates that spiral bulges comprise a more heterogeneous sample than do elliptical galaxies. We also find that the bulge components of SO galaxies follow a L ∝ σ4 relation with no gap with the ellipticals. The similarity in this relation for the spheroidal components of spiral, SO, and elliptical galaxies indicates that the systems are dynamically similar. We have compared our velocity dispersions with rotational velocities determined from neutral hydrogen widths. For a totally bulge dominated spiral the ratio of the asymptotic rotational velocity to the velocity dispersion is about 1.4. This suggests that the mass responsible for producing the flat rotation curves (presumably the "halo") resides in a spheroidal component rather than in the disk. Our study also substantiates our earlier result that the massive halo is not merely an extension of the bulge, but is a separate dynamical component for most of our galaxies. A simple three-component model has been constructed to aid in the interpretation of this data. These models provide an independent indication of the existence of massive halos in spiral galaxies.

  5. Observational Manifestation of Chaos in Grand Design Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Fridman, Alexei M.; Sagdeev, Roald Z.; Khoruzii, Oleg V.; et al.

    To study dynamic properties of the gaseous disk of the grand design spiral galaxy NGC 3631 we calculate the Lyapunov characteristic numbers (LCN) for different families of streamlines in the disk. For the trajectories near separatrices of the giant vortices and near saddle points presenting in the velocity field, the LCN turned out to be positive. The result is insensitive to the method of the calculation. Both methods -- using two trajectories and based on linearized equations -- give the identical results. The values of the LCN in the gaseous disk of NGC 3631 are independent on the Riemannian metric used for the calculations in agreement with the classical mathematical theorem. The spectra of the 'short-time' LCN (stretching numbers) evaluated for the same trajectories turned out to be non-invariant. We confirmed this result obtained for the real galactic disk on classical model examples.

  6. Infrared observations of the spiral galaxy NGC 891

    NASA Astrophysics Data System (ADS)

    Whaley, Cynthia

    2007-08-01

    This thesis is a detailed, multi-waveband study of the inner 14 kpc of the famous spiral galaxy, NCG 891. The primary data have come from the Infrared Space Observatory's Camera. These data are images of the galaxy in 9 different mid-infrared wavebands. We have supported these data with archived data from the Spitzer Infrared Array Camera in 4 similar wavebands. Surface brightness contour maps of the galaxy were created and examined to determine where the mid-infrared emitters are located with respect to the galactic plane. We have determined that the main mid-infrared emission, due to warm dust and PAHs, lies in a thin disk of width 700 - 800 pc, but has faint emission that reaches up to about 2.3 kpc into the halo. The infrared spectral energy distribution (SED) for four environments in NGC 891 were created from the above mentioned wavebands as well as measurements from Spitzer's Multiband Imaging Photometer (3 Far-Infrared wavebands), the Two Micron All Sky Survey J, H, and K near-infrared wavebands, and the Sub- millimeter Common User Bolometer Array 450 and 850 mm bands. These spectra were fit with a SED model created by Frederic Galliano, and the physical properties of these environments were computed. The maps and SED show that while there is a relatively large amount of dust in NGC 891's halo, there is a depletion of PAHs beyond 2.3 kpc from the mid-plane. This is only the fourth galaxy to date that has PAH emission discovered in the halo, and it is the first in which the SED has been modeled for the halo.

  7. Big Fish in Small Ponds: massive stars in the low-mass clusters of M83

    SciTech Connect

    Andrews, J. E.; Calzetti, D.; McElwee, Sean; Chandar, R.; Elmegreen, B. G.; Kennicutt, R. C.; Kim, Hwihyun; Krumholz, Mark R.; Lee, J. C.; Whitmore, B.; O'Connell, R. W. E-mail: callzetti@astro.umass.edu

    2014-09-20

    We have used multi-wavelength Hubble Space Telescope WFC3 data of the starbursting spiral galaxy M83 in order to measure variations in the upper end of the stellar initial mass function (uIMF) using the production rate of ionizing photons in unresolved clusters with ages ≤ 8 Myr. As in earlier papers on M51 and NGC 4214, the uIMF in M83 is consistent with a universal IMF, and stochastic sampling of the stellar populations in the ∼<10{sup 3} M {sub ☉} clusters are responsible for any deviations in this universality. The ensemble cluster population, as well as individual clusters, also imply that the most massive star in a cluster does not depend on the cluster mass. In fact, we have found that these small clusters seem to have an over-abundance of ionizing photons when compared to an expected universal or truncated IMF. This also suggests that the presence of massive stars in these clusters does not affect the star formation in a destructive way.

  8. Big Fish in Small Ponds: Massive Stars in the Low-mass Clusters of M83

    NASA Astrophysics Data System (ADS)

    Andrews, J. E.; Calzetti, D.; Chandar, R.; Elmegreen, B. G.; Kennicutt, R. C.; Kim, Hwihyun; Krumholz, Mark R.; Lee, J. C.; McElwee, Sean; O'Connell, R. W.; Whitmore, B.

    2014-09-01

    We have used multi-wavelength Hubble Space Telescope WFC3 data of the starbursting spiral galaxy M83 in order to measure variations in the upper end of the stellar initial mass function (uIMF) using the production rate of ionizing photons in unresolved clusters with ages <= 8 Myr. As in earlier papers on M51 and NGC 4214, the uIMF in M83 is consistent with a universal IMF, and stochastic sampling of the stellar populations in the lap103 M ⊙ clusters are responsible for any deviations in this universality. The ensemble cluster population, as well as individual clusters, also imply that the most massive star in a cluster does not depend on the cluster mass. In fact, we have found that these small clusters seem to have an over-abundance of ionizing photons when compared to an expected universal or truncated IMF. This also suggests that the presence of massive stars in these clusters does not affect the star formation in a destructive way.

  9. The nearby spiral density-wave structure of the Galaxy

    NASA Astrophysics Data System (ADS)

    Griv, Evgeny; Jiang, Ing-Guey; Hou, Li-Gang

    2017-07-01

    Accurate measurements of distances and line-of-sight velocities of 19291 intermediate-old giant stars in the near-infrared with typical uncertainties in the distances and velocities of 5 per cent and 0.1 km s-1 have recently been carried out to examine the Galactic disc with the APOGEE survey. In the framework of the Lin-Shu density-wave proposal for the galactic spiral structure, we use the APOGEE-RC DR13 data to investigate coherent non-axisymmetric flows within a few kiloparsecs from the Sun which are superimposed on a circular motion in the disc. Systematic wave-like departures of velocities from circular motion for stars are really detected. These systematic non-circular velocities are used to recover the parameters of the spiral arm segments of density waves of the Galaxy in the solar vicinity. The results of the work can be tested with the large amount of data from the Gaia satellite mission in the near future.

  10. Analyzing Non-circular Motions in Spiral Galaxies Through 3D Spectroscopy

    NASA Astrophysics Data System (ADS)

    Fuentes-Carrera, I.; Rosado, M.; Amram, P.

    3D spectroscopic techniques allow the assessment of different types of motions in extended objects. In the case of spiral galaxies, thes type of techniques allow us to trace not only the (almost) circular motion of the ionized gas, but also the motions arising from the presence of structure such as bars, spiral arms and tidal features. We present an analysis of non-circular motions in spiral galaxies in interacting pairs using scanning Fabry-Perot interferometry of emission lines. We show how this analysis can be helpful to differentiate circular from non-circular motions in the kinematical analysis of this type of galaxies.

  11. Galactic Winds and the X-ray Luminous Bulges of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Wilcots, Eric M.; Kaczmarek, J.

    2010-01-01

    Galactic winds are typically associated with galaxies that host AGN or are undergoing vigorous star formation. The discovery of the overpressurized hot gas in the bulge of NGC 3631 inspired the investigation of several more normal, quiescent spiral galaxies_all with an X-ray luminous bulge. The sample was studied with the WIYN 3.5m. We present the results of an integral field unit study of the kinematics of ionized and neutral gas in the bulges of spiral galaxies and discuss the frequency of galactic winds amongst "normal” early-type spirals.

  12. UIT Ultraviolet Surface Photometry of the Spiral Galaxy M74

    NASA Astrophysics Data System (ADS)

    Cornett, R. H.; Greason, M. R.; Offenberg, J. D.; Bohlin, R. C.; Cheng, K. P.; O'Connell, R. W.; Roberts, M. R.; Smith, A. M.; Smith, E. P.; Angione, R. J.; Talbert, F. D.; Stecher, T. P.

    1993-05-01

    UV photometry from Ultraviolet Imaging Telescope (UIT) images at 1520 Angstroms (magnitudes mbone) and 2490 Angstroms (maone) of the spiral galaxy M74 (NGC628) is compared with ha, R, V, and B surface photometry and models. M74's surface brightness profiles have central peaks with exponential falloffs; the profiles' exponential scale lengths increase with decreasing continuum wavelength. The slope of the continuum-subtracted ha profile is between those of FUV and NUV profiles, consistent with related origins of ha and UV emission in extreme Population I material. M74's color profiles have small gradients, all becoming bluer with increasing radius. The UIT color (mbone-maone) averages near 0.0, the color of an A0 star, over the central 20 arcsec radius, and slopes from ~ -0.2 to ~ -0.4 from 20 to 200 arcsec. Spiral arms dominate surface photometry colors; interarm regions are slightly redder. In the UV, M74's nuclear region resembles disk/spiral arm material in color and morphology, unlike M81. (mbone-maone) colors and models of M74's central region clearly demonstrate that there are no O or B stars in the central 10 arcsec. M74's (mbone-maone) profile is similar to M33's but is ~ 0.5 mag redder. M74 is ~ 0.4 mag bluer than M81 in its outer disk. We investigate explanations for both the color profiles and the differences among the galaxies. M74's maone-V and mbone-V color profiles cannot be explained by a disk of uniform color behind a screen of dust with a known reddening function, distributed like the neutral gas with a fixed gas-to-dust ratio. Known abundance variations could produce the observed color gradient in M74; however, evolutionary cluster models show that sensible time parameters, including star formation start time and exponential decay rate, also produce the observed colors of M74, M33, and M81.

  13. Near-infrared surface photometry and morphology in virgo cluster spiral galaxy nuclear regions

    NASA Astrophysics Data System (ADS)

    Rauscher, Bernard J.

    1995-04-01

    This paper presents very high spatial resolution (seeing 0.75 arcsec FWHM) K band surface photometry of 15 Virgo cluster spiral galaxy nuclear regions (radii less then 1 kpc). It presents B and I CCD images of 13 of these galaxies. The goals of the study were: (1) to begin to establish a K band baseline of normal spiral galaxy nuclear regions against which peculiar galaxies may be compared, (2) to provide better contsraints on N-body models, and (3) to complement near-infrared studies of large scale structure in spiral galaxies with very high resolution imaging of the important nuclear regions. The principle findings are (1) between 1/4 and 1/3 of these nuclear regions show K band evidence of traxiality, (2) approximately 1/2 of these galaxies have axisymmetric nuclear regions, and (3) NGC 4321 has a bar that is not detectable in the optical images.

  14. New insights on the formation and assembly of M83 from deep near-infrared imaging

    SciTech Connect

    Barnes, Kate L.; Van Zee, Liese; Dale, Daniel A.; Staudaher, Shawn; Bullock, James S.; Calzetti, Daniela; Chandar, Rupali; Dalcanton, Julianne J.

    2014-07-10

    We present results from new near-infrared (NIR) imaging from the Spitzer Space Telescope that trace the low surface brightness features of the outer disk and stellar stream in the nearby spiral galaxy, M83. Previous observations have shown that M83 hosts a faint stellar stream to the northwest and a star-forming disk that extends to ∼3 times the optical radius (R{sub 25}). By combining the NIR imaging with archival far-ultraviolet (FUV) and H I imaging, we study the star formation history of the system. The NIR surface brightness profile has a break at ∼5.'8 (equivalent to 8.1 kpc and 0.9 R{sub 25}) with a shallower slope beyond this radius, which may result from the recent accretion of gas onto the outer disk and subsequent star formation. Additionally, the ratio of FUV to NIR flux increases with increasing radius in several arms throughout the extended star forming disk, indicating an increase in the ratio of the present to past star formation rate with increasing radius. This sort of inside-out disk formation is consistent with observations of gas infall onto the outer disk of M83. Finally, the flux, size, and shape of the stellar stream are measured and the origin of the stream is explored. The stream has a total NIR flux of 11.6 mJy, which implies a stellar mass of 1 × 10{sup 8} M{sub ☉} in an area subtending ∼80°. No FUV emission is detected in the stream at a level greater than the noise, confirming an intermediate-age or old stellar population in the stream.

  15. Disk mass densities in edge-on spiral galaxies

    NASA Technical Reports Server (NTRS)

    Rupen, Michael P.

    1990-01-01

    Very Large Array (VLA) observations of the neutral hydrogen (HI) gas in two nearby edge-on spirals (NGC 4565 and NGC 891) successfully resolve the thickness of the gas layers in both disks over a wide range in radii. The combination of B, C, and D array data produces a 4 arcsec (approx. 200 pc) beam and 21 km s(exp -1) velocity resolution, combined with sensitivity to structures as large as 18 arcmin (approx. 54 kpc). These observations directly constrain the mid-plane disk mass densities, under the assumption of an equilibrium between the thermal pressure of the gas and the gravitational attraction of the disk. The results of a preliminary analysis are given regarding the z-velocity dispersion of the gas, the mass-to-light ratio of the disk in NGC 4565, and the roles of atomic and molecular gases. The data also allow a detailed study of the HI in these galaxies; in general their brightness temperature distributions seem similar to that in the Milky Way. Both galaxies show asymmetric HI extensions beyond the optical disk. In NGC 4565 the extension is a surprisingly abrupt warp, which may bend back to parallel the galactic plane; the velocity structure implies the warp is continuous around the disk.

  16. Gas and stellar spiral arms and their offsets in the grand-design spiral galaxy M51

    NASA Astrophysics Data System (ADS)

    Egusa, Fumi; Mentuch Cooper, Erin; Koda, Jin; Baba, Junichi

    2017-02-01

    Theoretical studies on the response of interstellar gas to a gravitational potential disc with a quasi-stationary spiral arm pattern suggest that the gas experiences a sudden compression due to standing shock waves at spiral arms. This mechanism, called a galactic shock wave, predicts that gas spiral arms move from downstream to upstream of stellar arms with increasing radius inside a corotation radius. In order to investigate if this mechanism is at work in the grand-design spiral galaxy M51, we have measured azimuthal offsets between the peaks of stellar mass and gas mass distributions in its two spiral arms. The stellar mass distribution is created by the spatially resolved spectral energy distribution fitting to optical and near-infrared images, while the gas mass distribution is obtained by high-resolution CO and H I data. For the inner region (r ≤ 150 arcsec), we find that one arm is consistent with the galactic shock while the other is not. For the outer region, results are less certain due to the narrower range of offset values, the weakness of stellar arms, and the smaller number of successful offset measurements. The results suggest that the nature of two inner spiral arms is different, which is likely due to an interaction with the companion galaxy.

  17. 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

  18. Model of outgrowths in the spiral galaxies NGC 4921 and NGC 7049 and the origin of spiral arms

    NASA Astrophysics Data System (ADS)

    Carlqvist, Per

    2013-02-01

    NGC 4921 and 7049 are two spiral galaxies presenting narrow, distinct dust features. A detailed study of the morphology of those features has been carried out using Hubble Space Telescope archival images. NGC 4921 shows a few but well-defined dust arms midway to its centre while NGC 7049 displays many more dusty features, mainly collected within a ring-shaped formation. Numerous dark and filamentary structures, called outgrowths, are found to protrude from the dusty arms in both galaxies. The outgrowths point both outwards and inwards in the galaxies. Mostly they are found to be V-shaped or Y-shaped with the branches connected to dark arm filaments. Often the stem of the Y appears to consist of intertwined filaments. Remarkably, the outgrowths show considerable similarities to elephant trunks in H ii regions. A model of the outgrowths, based on magnetized filaments, is proposed. The model provides explanations of both the shapes and orientations of the outgrowths. Most important, it can also give an account for their intertwined structures. It is found that the longest outgrowths are confusingly similar to dusty spiral arms. This suggests that some of the outgrowths can develop into such arms. The time-scale of the development is estimated to be on the order of the rotation period of the arms or shorter. Similar processes may also take place in other spiral galaxies. If so, the model of the outgrowths can offer a new approach to the old winding problem of spiral arms.

  19. A radio continuum survey of edge-on spiral galaxies at 90 cm

    NASA Technical Reports Server (NTRS)

    Heikkila, B.; Webber, W. R.; Burns, Jack O.; Walterbos, R. A. M.; Duric, N.

    1993-01-01

    Accurate spectral indices of the radio emission from both the thin disk and thick disk or halo components are critical to understanding the propagation mechanisms of electrons within spiral galaxies. The spectral indices give information of relative importance of diffusion and synchrotron energy loss in the propagation of electrons in the disk. Our goal of this survey is to locate a larger sample of spiral galaxies that exhibit halo phenomena so that a statistical analysis will be possible.

  20. Vertical motions in the gaseous disk of the spiral galaxy NGC 3631

    NASA Astrophysics Data System (ADS)

    Fridman, A. M.; Koruzhii, O. V.; Zasov, A. V.; Sil'chenko, O. K.; Moiseev, A. V.; Burlak, A. N.; Afanas'ev, V. L.; Dodonov, S. N.; Knapen, J.

    1998-11-01

    The velocity field of the nearly face-on galaxy NGC 3631 is derived from observations in the Hα line on the 6-m telescope of the Special Astrophysical Observatory. These optical data are compared with radio observations of this galaxy (Knapen 1997). It is argued that the two-armed spiral structure of NGC 3631 has a wave nature, and that the observed vertical gas motions represent motions in a spiral density wave.

  1. 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.

  2. Spiral Galaxy Formation, Shape, Rotation and Evolution: A Perspective withOUT Mysterious Dark Matter

    NASA Astrophysics Data System (ADS)

    Gallo, C. F.; Feng, James Q.

    2013-04-01

    Various models for Spiral Galaxies are compared to arrive at the following viewpoint. (1)Peratt theoretically displays the formation and evolution of galaxies from hot plasma with a combination of gravity and electromagntic plasma effects, particularly circulating currents. The sequence proceeds from Elliptical to Irregular to stable Spiral Disc Galaxies. The spirals are initiated by radial EM plasma jets oriented around magnetic fields. (2)DeSouza observes/analyzes young spiral galaxies in the process of forming their spiral shapes. He observes radial Jets initiating from the central Bulge and evolving into full trailing spirals in agreement with Peratt's EM plasma simulations. (3) Feng and Gallo have successfully analyzed galactic rotation data with Newtonian gravity/dynamics withOUT Mysterious Dark Matter. Our model represents mature spiral disk galaxies whose behavior is dominated by gravity since the plasma has mostly condensed into stars at this late stage. This situation in similar to our gravity dominated Solar System. (4) All three models are based on known verified physics withOUT Mysterious Dark Matter.

  3. Hα Imaging of Early-Type (SA-SAB) Spiral Galaxies. I.

    NASA Astrophysics Data System (ADS)

    Hameed, Salman; Devereux, Nick

    1999-08-01

    Hα and continuum images are presented for 27 nearby early-type (Sa-Sab) spiral galaxies. Contrary to popular perception, the images reveal copious massive star formation in some of these galaxies. A determination of the Hα morphology and a measure of the Hα luminosity suggest that early-type spirals can be classified into two broad categories based on the luminosity of the largest H II region in the disk. The first category includes galaxies for which the individual H II regions have L_Hα<10^39 ergs s^-1. Most of the category 1 galaxies appear to be morphologically undisturbed but show a wide diversity in nuclear Hα properties. The second category includes galaxies that have at least one H II region in the disk with L_Hα>=10^39 ergs s^-1. All category 2 galaxies show either prominent dust lanes or other morphological peculiarities such as tidal tails, which suggests that the anomalously luminous H II regions in category 2 galaxies may have formed as a result of a recent interaction. The observations, which are part of an ongoing Hα survey, reveal early-type spirals to be a heterogeneous class of galaxies that are evolving in the current epoch. We have also identified some systematic differences between the classifications of spiral galaxies in the Second General Catalog and the Revised Shapley-Ames Catalog that may be traced to subtle variations in the application of the criteria used for classifying spiral galaxies. An examination of earlier studies suggests that perceptions concerning the Hubble-type dependence of star formation rates among spiral galaxies depends on the choice of catalog.

  4. 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.

  5. 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.

  6. Supermassive Black Hole Mass and Spiral Galaxy Pitch Angle at Intermediate to High Redshift

    NASA Astrophysics Data System (ADS)

    Hughes, John A.; Barrows, R. S.; Berrier, J. C.; Davis, B. L.; Kennefick, D.; Kennefick, J. D.; Lacy, C. H. S.; Seigar, M. S.; Shields, D. W.; Zoldak, K. A.

    2012-01-01

    A possible correlation between spiral galaxy pitch angle (P) and the mass of the central supermassive black hole (SMBH) of the galaxy (M) was reported (Seigar et al. 2008) from a sample of 27 nearby galaxies. Here we investigate the extension of this result to intermediate and high redshifts. We have selected AGN showing spiral structure in their host galaxies from the GOODS fields and from a sample of AGN with reverberation mapping SMBH mass estimates. After careful measure of the pitch angle of these galaxies, we compare the mass found from the M-P relation to that reported from reverberation mapping or estimated from their MgII profiles. By extending the sample to higher redshift, we demonstrate how the M-P relationship can be used to estimate the mass of SMBHs in the center of galaxies with imaging data alone, a useful tool in the study of galaxy evolution.

  7. Kinematics of the nuclear region of M83

    NASA Astrophysics Data System (ADS)

    Rodrigues, I.; Díaz, R. J.; Dottori, H.; Mediavilla, E.; Agüero, M. P.; Mast, D.

    2006-06-01

    The enormous energy output detected in many cores of galaxies is one of the key issues in the studies of galaxies and their evolution, notwithstanding several questions remain unsolved: Are accretion onto super-massive black holes and violent star formation just coevolving phenomena or necessary partners of the activity? How is the detailed physics of the mechanisms triggering the nuclear extended violent star formation? Which is the relationship of the triggering mechanisms with galaxy evolution? The main drawback to face these issues is that developed stages of large star formation events at galactic centres do not provide enough clues about their origin, since the morphological signatures of the triggering mechanism are smeared out in the time scale of a few orbital revolutions of the galaxy core. Here we present the onset of such an event undergone by M83, a galaxy nearby enough to allow detailed spatial cinematic and morphological studies. High resolution 3D near-IR spectroscopy sugests the capture of a satellite galaxy, whose spur left behind a giant nuclear arc of violent star formation. The age gradient within the arc supports that this structure traces the orbital path of the intruder. Our numerical modelling indicates that the two nuclei would coalesce in less than 50 Myr.

  8. A computer-generated galaxy model with long-lived two-armed spiral structure

    NASA Astrophysics Data System (ADS)

    Thomasson, Magnus; Elmegreen, Bruce G.; Donner, Karl Johan; Sundelius, Bjorn

    1990-06-01

    A long-lived two-armed spiral has been generated in an N-body computer simulation of a galaxy with a static bulge and halo and an active disk composed of 60,000 particles. The spiral lasts for about three pattern revolutions without severe distortion and persists for at least two more revolutions with distortions and bifurcations resulting from an increasingly clumpy ISM. This suggests that two-armed grand design spirals in nonbarred noninteracting galaxies can be long-lived if star formation and other heat sources not present in the simulation maintain a steady interstellar medium.

  9. Late-type galaxies - The shapes of the spiral arm filaments

    NASA Astrophysics Data System (ADS)

    Isserstedt, J.; Schindler, R.

    1987-03-01

    A study is conducted of the shapes of spiral arm filaments in 18 late-type galaxies in order to test the SSPSF theory's hyperbolic spiral arm predictions. After subtracting the disk component from the luminosity distribution by image filtering, the directions along which the intensity variations of the extreme Population I are minimal were determined in circular zones around the centers of the deprojected images; this constitutes an objective determination of pitch angles even for galaxies with very short and filamentary arms. The results obtained severely contradict SSPSF theory, instead implying that the spiral arms are wave phenomena exhibiting logarithmic shapes.

  10. Formation des etoiles massives dans les galaxies spirales

    NASA Astrophysics Data System (ADS)

    Lelievre, Mario

    Le but de cette thèse est de décrire la formation des étoiles massives dans les galaxies spirales appartenant à divers types morphologiques. L'imagerie Hα profonde combinée à une robuste méthode d'identification des régions HII ont permis de détecter et de mesurer les propriétés (position, taille, luminosité, taux de formation d'étoiles) de plusieurs régions HII situées dans le disque interne (R < R25) de dix galaxies mais aussi à leur périphérie (R ≥ R 25). De façon générale, la répartition des régions HII ne montre aucune évidence de structure morphologique à R < R25 (bras spiraux, anneau, barre) à moins de limiter l'analyse aux régions HII les plus grosses ou les plus lumineuses. La répartition des régions HII, de même que leur taille et leur luminosité, sont toutefois sujettes à de forts effets de sélection qui dépendent de la distance des galaxies et qu'il faut corriger en ramenant l'échantillon à une résolution spatiale commune. Les fonctions de luminosité montrent que les régions HII les plus brillantes ont tendance à se former dans la portion interne du disque. De plus, l'analyse des pentes révèle une forte corrélation linéaire par rapport au type morphologique. Aucun pic n'est observé dans les fonctions de luminosité à log L-37 qui révèlerait la transition entre les régions HII bornées par l'ionisation et par la densité. Une relation cubique est obtenue entre la taille et la luminosité des régions HII, cette relation variant toutefois de façon significative entre le disque interne et la périphérie d'une même galaxie. La densité et la dynamique du gaz et des étoiles pourraient influencer de façon significative la stabilité des nuages moléculaires face à l'effondrement gravitationnel. D'une part, l'étendue du disque de régions HII pour cinq galaxies de l'échantillon coïncide avec celle de l'hydrogène atomique. D'autre part, en analysant la stabilité des disques galactiques, on conclue

  11. Spiral Density Wave Triggering of Star Formation in SA and SAB Galaxies

    NASA Astrophysics Data System (ADS)

    Martínez-García, Eric E.; González-Lópezlira, Rosa A.; Bruzual-A, Gustavo

    2009-03-01

    Azimuthal color (age) gradients across spiral arms are one of the main predictions of density wave theory; gradients are the result of star formation triggered by the spiral waves. In a sample of 13 spiral galaxies of types A and AB, we find that ten of them present regions that match the theoretical predictions. By comparing the observed gradients with stellar population synthesis models, the pattern speed and the location of major resonances have been determined. The resonance positions inferred from this analysis indicate that nine of the objects have spiral arms that extend to the outer Lindblad resonance; for one of the galaxies, the spiral arms reach the corotation radius. The effects of dust, and of stellar densities, velocities, and metallicities on the color gradients are also discussed.

  12. Feathers in CO: CARMA CO(1-0) Observations of Four Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    La Vigne, Misty A.; Vogel, S. N.

    2007-12-01

    Feathers are striking extinction features that emerge from a spiral arm dust lane and arch into the interarm. Based on a study of HST archival images, La Vigne et al. 2006 find that feathers are common in a range of spiral galaxy types, and that observations of M51 suggest feathers emerge from giant molecular associations (GMAs) and can be associated with much of the star formation in a spiral galaxy. To evaluate whether the conclusions based on M51 can be more generally applied, we have observed CO(1-0) emission in four spiral galaxies at 2-3” resolution using the newly operational CARMA millimeter wave array. Maps of NGC 0628, NGC 3627, NGC 4637, and NGC 5055 are presented and implications for theories for the origin of feathers are discussed. CARMA operations are supported by the NSF under a cooperative agreement, and by the partner universities.

  13. The Distribution of Supernovae Relative to Spiral Arms of Host Disc Galaxies

    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.

    2017-07-01

    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. Our results suggest that shocks in spiral arms of GD galaxies trigger star formation in the leading edges of arms affecting the distributions of core-collapse (CC) SNe (known to have short-lived progenitors). The closer locations of SNe Ibc vs. 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, show symmetric distribution with respect to the peaks of spiral arms.

  14. VizieR Online Data Catalog: Southern sky survey of 1355 spiral galaxies (Mathewson+, 1992)

    NASA Astrophysics Data System (ADS)

    Mathewson, D. S.; Ford, V. L.; Buchhorn, M.

    2003-06-01

    Photometry of spiral galaxies less than about 5' in diameter was obtained in the Kron-Cousins I passband at the 1m f/8 telescope at Siding Sping Observatory. The 64m radio telescope at Parkes Observatory, CSIRO,was used to obtain HI profiles of 551 galaxies. (3 data files).

  15. The Resolved Stellar Population in 50 Regions of M83 from HST/WFC3 Early Release Science Observations

    NASA Technical Reports Server (NTRS)

    Kim, Hwihyun; Whitmore, Bradley C.; Chandar, Rupali; Saha, Abhijit; Kaleida, Catherine C.; Mutchler, Max; Cohen, Seth H.; Calzetti, Daniela; O’Connell, Robert W.; Windhorst, Rogier A.; hide

    2012-01-01

    We present a multi-wavelength photometric study of approximately 15,000 resolved stars in the nearby spiral galaxy M83 (NGC 5236, D = 4.61 Mpc) based on Hubble Space Telescope Wide Field Camera 3 observations using four filters: F336W, F438W, F555W, and F814W. We select 50 regions (an average size of 260 pc by 280 pc) in the spiral arm and inter-arm areas of M83 and determine the age distribution of the luminous stellar populations in each region. This is accomplished by correcting for extinction toward each individual star by comparing its colors with predictions from stellar isochrones.We compare the resulting luminosity-weighted mean ages of the luminous stars in the 50 regions with those determined from several independent methods, including the number ratio of red-to-blue supergiants, morphological appearance of the regions, surface brightness fluctuations, and the ages of clusters in the regions. We find reasonably good agreement between these methods. We also find that young stars are much more likely to be found in concentrated aggregates along spiral arms, while older stars are more dispersed. These results are consistent with the scenario that star formation is associated with the spiral arms, and stars form primarily in star clusters and then disperse on short timescales to form the field population. The locations ofWolf-Rayet stars are found to correlate with the positions of many of the youngest regions, providing additional support for our ability to accurately estimate ages. We address the effects of spatial resolution on the measured colors, magnitudes, and age estimates. While individual stars can occasionally show measurable differences in the colors and magnitudes, the age estimates for entire regions are only slightly affected.

  16. THE RESOLVED STELLAR POPULATION IN 50 REGIONS OF M83 FROM HST/WFC3 EARLY RELEASE SCIENCE OBSERVATIONS

    SciTech Connect

    Kim, Hwihyun; Cohen, Seth H.; Windhorst, Rogier A.; Whitmore, Bradley C.; Mutchler, Max; Bond, Howard E.; Chandar, Rupali; Saha, Abhijit; Kaleida, Catherine C.; Calzetti, Daniela; O'Connell, Robert W.; Balick, Bruce; Carollo, Marcella; Disney, Michael J.; Dopita, Michael A.; Frogel, Jay A.; Hall, Donald N. B.; Holtzman, Jon A.; Kimble, Randy A.; McCarthy, Patrick J.; and others

    2012-07-01

    We present a multi-wavelength photometric study of {approx}15,000 resolved stars in the nearby spiral galaxy M83 (NGC 5236, D = 4.61 Mpc) based on Hubble Space Telescope Wide Field Camera 3 observations using four filters: F336W, F438W, F555W, and F814W. We select 50 regions (an average size of 260 pc by 280 pc) in the spiral arm and inter-arm areas of M83 and determine the age distribution of the luminous stellar populations in each region. This is accomplished by correcting for extinction toward each individual star by comparing its colors with predictions from stellar isochrones. We compare the resulting luminosity-weighted mean ages of the luminous stars in the 50 regions with those determined from several independent methods, including the number ratio of red-to-blue supergiants, morphological appearance of the regions, surface brightness fluctuations, and the ages of clusters in the regions. We find reasonably good agreement between these methods. We also find that young stars are much more likely to be found in concentrated aggregates along spiral arms, while older stars are more dispersed. These results are consistent with the scenario that star formation is associated with the spiral arms, and stars form primarily in star clusters and then disperse on short timescales to form the field population. The locations of Wolf-Rayet stars are found to correlate with the positions of many of the youngest regions, providing additional support for our ability to accurately estimate ages. We address the effects of spatial resolution on the measured colors, magnitudes, and age estimates. While individual stars can occasionally show measurable differences in the colors and magnitudes, the age estimates for entire regions are only slightly affected.

  17. The Cluster Environment of a Triple-Double Episodic Radio Spiral Galaxy BCG

    NASA Astrophysics Data System (ADS)

    Irwin, Jimmy

    2012-10-01

    SDSS J140948.85-030232.5 (also referred to as or Speca) is unique in that it is the only known galaxy that is both a spiral radio galaxy and harbors three distinct pairs of radio relic lobes indicative of episodic radio outbursts. Furthermore, it is the brightest cluster galaxy of a cluster despite being a spiral. We propose a short XMM-Newton snapshot observation of the environment of Speca to determine the X-ray flux of the previously unobserved host cluster as a prelude to deeper X-ray observations to investigate the radio relic lobes interaction with the hot intracluster medium of the cluster.

  18. 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.

  19. Chemical abundances in Virgo cluster spirals - what drives the environmental dependence of galaxy metallicity?

    NASA Astrophysics Data System (ADS)

    Ellison, Sara; Skillman, Evan; Chung, Aeree

    2009-08-01

    The Virgo cluster is not only our nearest massive cluster, but its dynamical infancy also renders it an ideal laboratory for studies of cluster formation and galaxy evolution. Given the intense interest in Virgo, it is astounding that only 9 out of over 100 spirals in its firmament have chemical abundance measurements. We propose to simultaneously address this gap in our fundamental knowledge of Virgo cluster spirals and investigate how the metallicity and abundance gradients of star forming galaxies are sensitive to environment. Our sample consists of 13 Virgo cluster spiral galaxies, preferentially gas-poor early types, which complement the existing metallicity measurements. We also sample a range of clustercentric distances (0.3 -- 3 Mpc from M87), local densities and include several galaxies which exhibit evidence for interactions with the intra-cluster medium.

  20. How do spiral arm contrasts relate to bars, disc breaks and other fundamental galaxy properties?

    NASA Astrophysics Data System (ADS)

    Bittner, Adrian; Gadotti, Dimitri A.; Elmegreen, Bruce G.; Athanassoula, Evangelie; Elmegreen, Debra M.; Bosma, Albert; Muñoz-Mateos, Juan-Carlos

    2017-10-01

    We investigate how the properties of spiral arms relate to other fundamental galaxy properties, including bars and disc breaks. We use previously published measurements of those properties, and our own measurements of arm and bar contrasts for a large sample of galaxies, using 3.6 μm images from the Spitzer Survey of Stellar Structure in Galaxies. Flocculent galaxies are clearly distinguished from other spiral arm classes, especially by their lower stellar mass and surface density. Multi-armed and grand-design galaxies are similar in most of their fundamental parameters, excluding some bar properties and the bulge-to-total ratio. Based on these results, we revisit the sequence of spiral arm classes, and discuss classical bulges as a necessary condition for standing spiral wave modes in grand-design galaxies. We find a strong correlation between bulge-to-total ratio and bar contrast, and a weaker correlation between arm and bar contrasts. Barred and unbarred galaxies exhibit similar arm contrasts, but the highest arm contrasts are found exclusively in barred galaxies. Interestingly, the bar contrast, and its increase from flocculent to grand-design galaxies, is systematically more significant than that of the arm contrast. We corroborate previous findings concerning a connection between bars and disc breaks. In particular, in grand-design galaxies, the bar contrast correlates with the normalized disc break radius. This does not hold for other spiral arm classes or the arm contrast. Our measurements of arm and bar contrast and radial contrast profiles are publicly available.

  1. Distant encounters between disk galaxies and the origin of S 0 spirals

    NASA Astrophysics Data System (ADS)

    Icke, V.

    1985-03-01

    Numerical calculations of the hydrodynamics of a gaseous disk in a galaxy perturbed by an intruder flying in a hyperbolic orbit are presented. It is shown that if the pericenter of the distance between the galaxy and the intruder object becomes so large that stellar bridges and tails become unimportant, gravitational shocks may occur. It is suggested that the theoretical calculations may help explain the physical mechanisms of S 0 spiral galaxy formation. Computer-generated illustrations of the numerical results are provided.

  2. Gas motions in the plane of the spiral galaxy NGC 3631

    NASA Astrophysics Data System (ADS)

    Fridman, A. M.; Khoruzhii, O. V.; Polyachenko, E. V.; Zasov, A. V.; Sil'chenko, O. K.; Moiseev, A. V.; Burlak, A. N.; Afanasiev, V. L.; Dodonov, S. N.; Knapen, J. H.

    2001-05-01

    The velocity field of the nearly face-on galaxy NGC 3631, derived from observations in the Hα line and Hi radio line, is analysed to study perturbations related to the spiral structure of the galaxy. We confirm our previous conclusion that the line-of-sight velocity field gives evidence of the wave nature of the observed two-armed spiral structure. Fourier analysis of the observed velocity field is used to determine the location of corotation of the spiral structure of this galaxy, and the radius of corotation Rc is found to be about 42arcsec, or 3.2kpc. The vector velocity field of the gas in the plane of the disc is restored, and, taking into account that we previously investigated vertical motions, we now have a full three-dimensional gaseous velocity field of the galaxy. We show clear evidence of the existence of two anticyclonic and four cyclonic vortices near corotation in a frame of reference rotating with the spiral pattern. The centres of the anticyclones lie between the observed spiral arms. The cyclones lie close to the observed spirals, but their centres are shifted from the maxima in brightness.

  3. 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

  4. 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.

  5. VizieR Online Data Catalog: Hα in HII regions in spiral galaxies (Marquez+, 2002)

    NASA Astrophysics Data System (ADS)

    Marquez, I.; Masegosa, J.; Moles, M.; Varela, J.; Bettoni, D.; Galletta, G.

    2002-07-01

    In this paper we study long slit spectra in the region of Hα emission line of a sample of 111 spiral galaxies with recognizable and well defined spiral morphology and with a well determined environmental status, ranging from isolation to non-disruptive interaction with satellites or companions. The form and properties of the rotation curves are considered as a function of the isolation degree, morphological type and luminosity. The line ratios are used to estimate the metallicity of all the detected H II regions, thus producing a composite metallicity profile for different types of spirals. We have found that isolated galaxies tend to be of later types and lower luminosity than the interacting galaxies. The outer parts of the rotation curves of isolated galaxies tend to be flatter than in interacting galaxies, but they show similar relations between global parameters. The scatter of the Tully-Fisher relation defined by isolated galaxies is significantly lower than that of interacting galaxies. The [NII]/Hα ratios, used as a metallicity indicator, show a clear trend between Z and morphological type, t, with earlier spirals showing higher ratios; this trend is tighter when instead of t the gradient of the inner rotation curve, G, is used; no trend is found with the change in interaction status. The Z-gradient of the disks depends on the type, being almost flat for early spirals, and increasing for later types. The [NII]/Hα ratios measured for disk H II regions of interacting galaxies are higher than for normal/isolated objects, even if all the galaxy families present similar distributions of Hα equivalent width. (1 data file).

  6. 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.

  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.

    2016-12-01

    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) arcsec (≃1.83 ± 0.04 kpc) to within 4 per cent: Mein = (7.8 ± 0.3) × 1010 M⊙. 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 centre requires a steep total mass-to-light ratio gradient. A dynamical model including an NFW halo (with virial velocity v200 ≃ 240 ± 40 km s-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. Characterizing dw1335-29, a recently discovered dwarf satellite of M83

    NASA Astrophysics Data System (ADS)

    Carrillo, Andreia; Bell, Eric F.; Bailin, Jeremy; Monachesi, Antonela; de Jong, Roelof S.; Harmsen, B2enjamin; Slater, Colin T.

    2017-03-01

    The number, distribution and properties of dwarf satellites are crucial probes of the physics of galaxy formation at low masses and the response of satellite galaxies to the tidal and gas dynamical effects of their more massive parent. To make progress, it is necessary to augment and solidify the census of dwarf satellites of galaxies outside the Local Group. Müller et al. presented 16 dwarf galaxy candidates near M83, but lacking reliable distances, it is unclear which candidates are M83 satellites. Using red-giant-branch stars from the HST/GHOSTS survey in conjunction with ground-based images from VLT/VIMOS, we confirm that one of the candidates, dw1335-29 - with a projected distance of 26 kpc from M83 and a distance modulus of (m-M)_0 = 28.5^{+0.3}_{-0.1} - is a satellite of M83. We estimate an absolute magnitude MV = -10.1 ± 0.4, an ellipticity of 0.40^{+0.14}_{-0.22}, a half-light radius of 656^{+121}_{-170} pc and [Fe/H] = -1.3^{+0.3}_{-0.4}. Owing to dw1335-29's somewhat irregular shape and possible young stars, we classify this galaxy as a dwarf irregular or transition dwarf. This is curious, as with a projected distance of 26 kpc from M83, dw1335-29 is expected to lack recent star formation. Further study of M83's dwarf population will reveal if star formation in its satellites is commonplace (suggesting a lack of a hot gas envelope for M83 that would quench star formation) or rare (suggesting that dw1335-29 has a larger M83-centric distance, and is fortuitously projected to small radii).

  9. Modeling Spiral Galaxy Surface Luminosity to Explain Non-Uniform Inclination Distributions

    NASA Astrophysics Data System (ADS)

    Rozum, Jordan C.; Larson, S. L.

    2014-01-01

    The distribution of spiral and bar galaxy orientations is expected to be uniform. However, analysis of several major galaxy catalogs shows this is not always reflected in data. In an attempt to explain this discrepancy, we have developed a galaxy simulation code to compute the appearance of a spiral type galaxy as a function of its morphological parameters. We examine the dependence of observed brightness upon inclination angle by using smooth luminous mass density and interstellar medium (ISM) density distributions. The luminous mass component is integrated along a particular line of sight, thus producing a mass distribution, from which a surface luminosity profile is derived. The ISM component is integrated alongside the luminous mass component to account for light extinction. Using this model, we present simulated galaxy inclination distributions that account for potential selection effects.

  10. Detection of Extraplanar Diffuse Ionized Gas in M83

    NASA Astrophysics Data System (ADS)

    Boettcher, Erin; Gallagher, J. S., III; Zweibel, Ellen G.

    2017-08-01

    We present the first kinematic study of extraplanar diffuse ionized gas (eDIG) in the nearby, face-on disk galaxy M83 using optical emission-line spectroscopy from the Robert Stobie Spectrograph on the Southern African Large Telescope. We use a Markov Chain Monte Carlo method to decompose the [N ii]λ λ 6548, 6583, Hα, and [S ii]λ λ 6717, 6731 emission lines into H ii region and diffuse ionized gas emission. Extraplanar, diffuse gas is distinguished by its emission-line ratios ([N ii]λ6583/Hα ≳ 1.0) and its rotational velocity lag with respect to the disk ({{Δ }}v=-24 km s-1 in projection). With interesting implications for isotropy, the velocity dispersion of the diffuse gas, σ =96 km s-1, is a factor of a few higher in M83 than in the Milky Way and nearby, edge-on disk galaxies. The turbulent pressure gradient is sufficient to support the eDIG layer in dynamical equilibrium at an electron scale height of {h}z=1 kpc. However, this dynamical equilibrium model must be finely tuned to reproduce the rotational velocity lag. There is evidence of local bulk flows near star-forming regions in the disk, suggesting that the dynamical state of the gas may be intermediate between a dynamical equilibrium and a galactic fountain flow. As one of the first efforts to study eDIG kinematics in a face-on galaxy, this study demonstrates the feasibility of characterizing the radial distribution, bulk velocities, and vertical velocity dispersions in low-inclination systems. Based on observations made with the Southern African Large Telescope (SALT) under program 2015-2-SCI-004 (PI: E. Boettcher).

  11. Effect of dark matter halo on global spiral modes in galaxies

    NASA Astrophysics Data System (ADS)

    Ghosh, Soumavo; Saini, Tarun Deep; Jog, Chanda J.

    2016-02-01

    Low surface brightness (LSB) galaxies form a major class of galaxies, and are characterized by low disc surface density and low star formation rate. These are known to be dominated by dark matter halo from the innermost regions. Here, we study the role of the dark matter halo on the grand-design, m = 2, spiral modes in a galactic disc by carrying out a global mode analysis in the WKB approximation. The Bohr-Sommerfeld quantization rule is used to determine how many discrete global spiral modes are permitted. First, a typical superthin, LSB galaxy UGC 7321 is studied by taking only the galactic disc, modelled as a fluid; and then the disc embedded in a dark matter halo. We find that both cases permit the existence of global spiral modes. This is in contrast to earlier results where the inclusion of dark matter halo was shown to nearly fully suppress local, swing-amplified spiral features. Although technically global modes are permitted in the fluid model as shown here, we argue that due to lack of tidal interactions, these are not triggered in LSB galaxies. For comparison, we carried out a similar analysis for the Galaxy, for which the dark matter halo does not dominate in the inner regions. We show that here too the dark matter halo has little effect, hence the disc embedded in a halo is also able to support global modes. The derived pattern speed of the global mode agrees fairly well with the observed value for the Galaxy.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  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. 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.

  16. Determination of Disk Thickness of Face-on Spiral Galaxies and Its Image Processing Method

    NASA Astrophysics Data System (ADS)

    Hu, T.; Peng, Q. H.

    2014-11-01

    It is uneasy to obtain the disk thickness of face-on spiral galaxies by measuring the galactic light distributions. Here we obtain the spiral galactic disk thickness based on an asymptotic expression of Poisson's equation for a logarithmic perturbation of matter density in spiral galaxies. For measuring the key parameter of the innermost position of the spiral arm (forbidden radius r_0) freed from the contamination by the light of bulge, an improved image processing method is used in this study by subtracting a decomposition brightness model from the galactic observed image. On the basis of measuring some fundamental parameters of spiral structures, we obtain the disk thickness and some other parameters of two (types S and SB) face-on spiral galaxies, and their ratio parameters (r_{b}/r_{d} and r_{d}/H) are also derived. By using this improved subtracted-method, it is easy to measure the forbidden radius r_0, which is smaller than that obtained from unsubtracted-method.

  17. 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.

  18. 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.

  19. A COMPARATIVE STUDY OF KNOTS OF STAR FORMATION IN INTERACTING VERSUS SPIRAL GALAXIES

    SciTech Connect

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

    2016-03-15

    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.

  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. 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.

  2. On the nature and correction of the spurious S-wise spiral galaxy winding bias in Galaxy Zoo 1

    NASA Astrophysics Data System (ADS)

    Hayes, Wayne B.; Davis, Darren; Silva, Pedro

    2017-04-01

    The Galaxy Zoo 1 catalogue displays a bias towards the S-wise winding direction in spiral galaxies, which has yet to be explained. The lack of an explanation confounds our attempts to verify the Cosmological Principle, and has spurred some debate as to whether a bias exists in the real Universe. The bias manifests not only in the obvious case of trying to decide if the universe as a whole has a winding bias, but also in the more insidious case of selecting which Galaxies to include in a winding direction survey. While the former bias has been accounted for in a previous image-mirroring study, the latter has not. Furthermore, the bias has never been corrected in the GZ1 catalogue, as only a small sample of the GZ1 catalogue was reexamined during the mirror study. We show that the existing bias is a human selection effect rather than a human chirality bias. In effect, the excess S-wise votes are spuriously 'stolen' from the elliptical and edge-on-disc categories, not the Z-wise category. Thus, when selecting a set of spiral galaxies by imposing a threshold T so that max (PS, PZ) > T or PS + PZ > T, we spuriously select more S-wise than Z-wise galaxies. We show that when a provably unbiased machine selects which galaxies are spirals independent of their chirality, the S-wise surplus vanishes, even if humans still determine the chirality. Thus, when viewed across the entire GZ1 sample (and by implication, the Sloan catalogue), the winding direction of arms in spiral galaxies as viewed from Earth is consistent with the flip of a fair coin.

  3. The Black Hole Mass - Pitch Angle Relation of Type I AGN In Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Schilling, Amanda; Jones, Logan; Hughes, John A.; Barrows, R. Scott; Kennefick, Julia D.

    2017-01-01

    A relationship between the mass of supermassive black holes, M, at the center of galaxies and the pitch angle, P, a measure of tightness of spiral arms, was recently reported by Berrier, et al. (2013 ApJ 769, 132) for late type galaxies. The relationship, established for a local sample, shows that spiral galaxies with tighter pitch angles host higher mass black holes. In this work, we explore the M-P relation for a sample of 50 low to moderate redshift (0.04spiral galaxies that host Type 1 Active Galactic Nuclei, AGN. These objects were selected from the SDSS quasar catalog and various studies involving HST imaging. Broad Hβ, Hα, and MgII and narrow [OIII]λ5007 emission lines were used with established mass scaling relations to estimate black-hole mass. Pitch angles were measured using a 2DFFT technique (Davis, et al., 2012 ApJS 199, 33). We find that the M-P relation for the higher redshift, AGN sample differs from that of the local sample and discuss the possibility of AGN feedback by looking at a proposed Fundamental Plane for late-type galaxies - a correlation between bulge mass, disk mass, and spiral-arm pitch angle (Davis, et al. 2015, ApJ 802, L13).

  4. Galaxy And Mass Assembly (GAMA): Gas Fueling of Spiral Galaxies in the Local Universe. I. The Effect of the Group Environment on Star Formation in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Grootes, M. W.; Tuffs, R. J.; Popescu, C. C.; Norberg, P.; Robotham, A. S. G.; Liske, J.; Andrae, E.; Baldry, I. K.; Gunawardhana, M.; Kelvin, L. S.; Madore, B. F.; Seibert, M.; Taylor, E. N.; Alpaslan, M.; Brown, M. J. I.; Cluver, M. E.; Driver, S. P.; Bland-Hawthorn, J.; Holwerda, B. W.; Hopkins, A. M.; Lopez-Sanchez, A. R.; Loveday, J.; Rushton, M.

    2017-03-01

    We quantify the effect of the galaxy group environment (for group masses of 1012.5–1014.0 M ⊙) on the current star formation rate (SFR) of a pure, morphologically selected sample of disk-dominated (i.e., late-type spiral) galaxies with redshift ≤0.13. The sample embraces a full representation of quiescent and star-forming disks with stellar mass M * ≥ 109.5 M ⊙. We focus on the effects on SFR of interactions between grouped galaxies and the putative intrahalo medium (IHM) of their host group dark matter halos, isolating these effects from those induced through galaxy–galaxy interactions, and utilizing a radiation transfer analysis to remove the inclination dependence of derived SFRs. The dependence of SFR on M * is controlled for by measuring offsets Δlog(ψ *) of grouped galaxies about a single power-law relation in specific SFR, {\\psi }* \\propto {M}* -0.45+/- 0.01, exhibited by non-grouped “field” galaxies in the sample. While a small minority of the group satellites are strongly quenched, the group centrals and a large majority of satellites exhibit levels of ψ * statistically indistinguishable from their field counterparts, for all M *, albeit with a higher scatter of 0.44 dex about the field reference relation (versus 0.27 dex for the field). Modeling the distributions in Δlog(ψ *), we find that (i) after infall into groups, disk-dominated galaxies continue to be characterized by a similar rapid cycling of gas into and out of their interstellar medium shown prior to infall, with inflows and outflows of ∼1.5–5 x SFR and ∼1–4 x SFR, respectively; and (ii) the independence of the continuity of these gas flow cycles on M * appears inconsistent with the required fueling being sourced from gas in the circumgalactic medium on scales of ∼100 kpc. Instead, our data favor ongoing fueling of satellites from the IHM of the host group halo on ∼Mpc scales, i.e., from gas not initially associated with the galaxies upon infall. Consequently

  5. 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.

  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 Supermassive Black Hole Mass - Pitch Angle Relation in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Kennefick, Daniel; Berrier, J. C.; Kennefick, J. D.; Seigar, M.; Davis, B. L.; Barrows, R. S.; Shields, D.; Lacy, C. H.

    2013-01-01

    We present new and improved evidence for a strong correlation, with low scatter, between supermassive black hole mass and spiral arm pitch angle in disk galaxies. Such a correlation could be a useful tool for developing a SMBH mass function for both local and distant galaxies, because other host galaxy features which correlate with black hole mass either require expensive spectroscopy (as in the M-sigma relation) or work less well for spiral than for other galaxies because of the need to disentangle the bulge component from the disk and bar components (Bulge luminosity or Sersic index). A late-type SMBH mass function derived from pitch angle measurements could complement nicely early-type mass functions derived from these other measurements, especially because the late-type mass function has so far received less attention than the early-type mass function.

  8. 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.

  9. Characterizing Dw1335-29, a Recently Discovered Dwarf Satellite of M83

    NASA Astrophysics Data System (ADS)

    Carrillo, Andreia Jessica; Bell, Eric F.; Bailin, Jeremy; Monachesi, Antonela

    2016-01-01

    Simulations of galaxy formation in a cosmological context predict that galaxies should be surrounded by hundreds of relatively massive dark matter subhalos, each of which was expected to host a dwarf satellite galaxy. Large numbers of luminous dwarf galaxies do not exist around the Milky Way or M31 - this has been termed the missing satellite problem. There are a number of possible physical drivers of this discrepancy, some of which might predict significant differences from galaxy to galaxy. Accordingly, there are a number of efforts whose goal is to solidify and augment the census of dwarf satellites of external galaxies, outside the Local Group. Recently, Mueller, Jergen & Bingelli (2015; arXiv.1509.04931) presented 16 dwarf galaxy candidates in the vicinity of M83 using the Dark Energy CAMera (DECAM). With a field from the HST/GHOSTS survey that partly covers dw1335-29 (Radburn-Smith et al. 2011; ApJS, 195, 18) in conjunction with complementary ground-based images from VIMOS that cover the whole dwarf, we confirm that one of the candidates dw1335-29 is a dwarf satellite of M83, at a projected distance from M83 of 26 kpc and a with distance modulus of m-M = 28.5-0.1+0.3, placing it in the M83 group. From our VIMOS imaging that covers the entire dwarf, we estimate an absolute magnitude of MV = -9.8-0.1+0.3, show that it is elongated with an ellipticity of 0.35+/-0.15, and has a half light radius of 500+/-50pc. Dw1335-29 has both a somewhat irregular shape and has superimposed young stars in the resolved stellar population maps, leading us to classify this galaxy as a faint dwarf irregular or transition dwarf. This is especially curious, as with a projected distance of only 26kpc from M83, our prior expectation from study of the Local Group (following e.g., Grebel et al. 2003; AJ, 125, 1926, Slater & Bell 2013; ApJ, 772, 15) would be that dw1335-29 would lack recent star formation. Further study of M83's dwarf population will reveal if star formation in its dwarfs

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  12. A neutral hydrogen study of the barred spiral galaxy NGC 3319

    NASA Astrophysics Data System (ADS)

    Moore, E. M.; Gottesman, S. T.

    1998-03-01

    Neutral hydrogen line observations of the late-type barred spiral galaxy NGC 3319 are presented. The distribution and kinematics of the galaxy are studied using the Very Large Array, with spatial resolutions between 11 and 50 arcsec and a channel separation of 10.33 km/s. As is typical for late-type galaxies, NGC 3319 is rich in H I, with a gaseous bar and spiral features. Several large, low-density regions are present, and the H I spiral structure is distorted, especially in the south. The gas distribution is asymmetric and extends significantly further to the southeast due to a long, off-center tail. Noncircular motions caused by the bar, spiral structure, and low-density regions are present in the radial velocity field, complicating the rotation curve analysis. These nonaxisymmetric structures cause the values of the position angle and inclination derived from the velocity field to vary across the disk. In addition, beyond a radius of 180 arcsec, the velocity field is severely perturbed on the approaching (southern) side of the galaxy, and the disk becomes nonplanar. However, the galaxy does not show the typical 'integral sign' shape of a warped system. We detect a small system approximately 11 arcmin south of the center of NGC 3319. It is seen in eight velocity channels and is coincident with a small, resolved object in the Palomar Sky Survey. A tidal interaction between this object and NGC 3319 is the most likely cause of the distorted spiral structure, the H I tail, and the velocity perturbations found in the southern half of the galaxy. Infalling tidal debris from such an event may account for the large, low-density regions found in the disk, several of which show kinematic evidence that suggest they are expanding superstructures.

  13. Les Abondances Chimiques dans les Galaxies Spirales de Type Precoce

    NASA Astrophysics Data System (ADS)

    Dutil, Yvan

    1998-09-01

    Les galaxies spriales presentent une distribution continue de formes et de proprietes physiques. A l'heure actuelle, il existe deux ecoles de pensee au sujet de la nature de ces proprietes morphologiques des galaxies. Pour certains elles sont innees, pour d'autres elles sont acquises. Les gradients d'abondance nebulaires, de par leur sensibilite aux mouvements a grande echelle du gaz et au taux de formation stellaire, offrent une possibilite de trancher dans ce debat. Toutefois, jusqu'ici, on a surtout observe les gradients d'abondance dans les galaxies de type tardif. Le premier objectif de cette these est d'enrichir l'echantillon de galaxies de type precoce observees. Le second objectif est de demontrer qu'il y a deja eu une barre dans les galaxies de type precoce et, si possible, de chercher des traces d'interactions dans ces galaxies. Dans le cadre de cette these, j'ai observe huit galaxies de type precoce. Mes observations indiquent que ces galaxies presentent des profils d'abondance dont les caracteristiques se rapprochent des galaxies barrees, meme si certaines ne presentent pas de barres. Ce resultat renforce l'hypothese selon laquelle les galaxies changent de type morphologique au cours du temps sous l'effet d'instabilites comme les barres.

  14. X-ray, optical, and radio properties of the extensive SNR population in M83

    NASA Astrophysics Data System (ADS)

    Blair, W.; Long, S. K.; Winkler, F.; Soria, R.; Kuntz, D. K.; Plucinsky, P. P.; Dopita, A. M.

    2016-06-01

    The nearly face-on spiral galaxy M83 (d=4.6 Mpc) provides a significant opportunity for finding and studying a large and diverse sample of SNRs all at the same distance, given its active star formation, a starburst nuclear region, and at least six SNe since 1923. As the result of a concerted effort involving ground and spaced-based studies at radio (ATCA), optical and NIR (Magellan 6.5m and HST), and X-ray (Chandra) wavelengths, we have identified almost 300 SNRs in M83. Of these, at least 87 and 47 were detected in the X-ray and radio bands. Some 227 of the SNR candidates are within the regions observed in [Fe II] 1.64 microns with HST WFC3/IR, and we detect ∼100 of them, including ~8 in dusty regions where the [Fe II] emission was the primary means of identification. Follow-up ground-based spectroscopy of 99 of the 300 SNRs with Gemini-S and the GMOS instrument shows that essentially all of the SNRs identified in ground-based imaging have the [S II]/Halpha ratios expected of bona fide SNRs, and that most of the SNRs in the sample are “normal ISM-dominated” SNRs, in the sense that the line widths are narrow and the spectra look like radiative shocks. We have studied a number of interesting individual SNRs and historical SNe counterparts, as well as investigating the ensemble population of nearly 300 SNRs to better understand their properties as a group, their evolution, and their impact on their host galaxy. Of particular interest is a set of the smallest diameter (and hence presumably youngest) objects measured with HST, where the 0.04arcsec WFC3-UVIS pixels correspond to ~1 pc. One SNR has very broad emission lines and given its small size, was most likely a SN that occurred during the last century but was missed. A number of the other objects are comparable to the Crab Nebula or Cas A in size, but very few show the high velocities and spectral signatures of ejecta. Rather, their spectra show low velocities and “normal” ISM-dominated emissions, albeit

  15. Formation of S0 galaxies through mergers. Explaining angular momentum and concentration change from spirals to S0s

    NASA Astrophysics Data System (ADS)

    Querejeta, M.; Eliche-Moral, M. C.; Tapia, T.; Borlaff, A.; van de Ven, G.; Lyubenova, M.; Martig, M.; Falcón-Barroso, J.; Méndez-Abreu, J.

    2015-07-01

    The CALIFA team has recently found that the stellar angular momentum and concentration of late-type spiral galaxies are incompatible with those of lenticular galaxies (S0s), concluding that fading alone cannot satisfactorily explain the evolution from spirals into S0s. Here we explore whether major mergers can provide an alternative way to transform spirals into S0s by analysing the spiral-spiral major mergers from the GalMer database that lead to realistic, relaxed S0-like galaxies. We find that the change in stellar angular momentum and concentration can explain the differences in the λRe-R90/R50 plane found by the CALIFA team. Major mergers thus offer a feasible explanation for the transformation of spirals into S0s. Table 1 is available in electronic form at http://www.aanda.org

  16. Massive Star Formation in Early-type(Sa-Sab) Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Hameed, S.

    1999-12-01

    We have conducted an Hα imaging survey of 57 bright, nearby, early-type spiral galaxies. The new Hα images have revealed them to be a heterogeneous class of galaxies with Hα morphologies ranging from filamentary, low luminosity nuclear emission line spirals to what we suspect are compact, luminous nuclear starbursts. Contrary to popular perception, our images have revealed a significant number(15-20%) of Sa-Sab galaxies with massive star formation rates comparable to the most prolifically star forming Sc galaxies. A determination of the Hα morphology and a measure of the Hα luminosity suggests that early-type spirals can be classified into two broad categories. The first category includes galaxies for which the individual HII regions have L(Hα ) < 1039 erg/s. Most of the category 1 galaxies appear to be morphologically undisturbed, but show a wide diversity in nuclear Hα properties. The second category includes galaxies which have at least one HII region in the disk with L(Hα ) >= 1039 erg/s. All category 2 galaxies show morphological peculiarities, such as tidal tails, which suggests that the anomalously luminous HII regions may have formed as a result of a recent interaction. We have also determined HII region luminosity functions for a subset of our sample and find that the shape of the HII region LF is different when a giant HII region is present compared to a galaxy which contains only HII regions of modest luminosity. The difference may point to corresponding differences in massive star formation triggering mechanisms.

  17. Hα Imaging of Early-Type Sa-Sab Spiral Galaxies. II. Global Properties

    NASA Astrophysics Data System (ADS)

    Hameed, Salman; Devereux, Nick

    2005-06-01

    New results, based on one of the most comprehensive Hα imaging surveys of nearby Sa-Sab spirals completed to date, reveals early-type spirals to be a diverse group of galaxies that span a wide range in massive star formation rates. While the majority of Sa-Sab galaxies in our sample are forming stars at a modest rate, a significant fraction (~29%) exhibit star formation rates greater than 1 Msolar yr-1, rivaling the most prolifically star-forming late-type spirals. A similar diversity is apparent in the star formation history of Sa-Sab spirals as measured by their Hα equivalent widths. Consistent with our preliminary results presented in the first paper in this series, we find giant H II regions [L(Hα)>=1039 ergs s-1] in the disks of ~37% of early-type spirals. We suspect that recent minor mergers or past interactions are responsible for the elevated levels of Hα emission and, perhaps, for the presence of giant H II regions in these galaxies. Our results, however, are not in total agreement with the Hα study of Kennicutt & Kent, who did not find any early-type spirals with Hα equivalent widths >14 Å. A close examination of the morphological classification of galaxies, however, suggests that systematic differences between the Revised Shapley-Ames Catalog and the Second Reference Catalogue may be responsible for the contrasting results. Based on observations obtained with the 3.5 m telescope at Apache Point Observatory (APO) and the 0.9 m telescope at Kitt Peak National Observatory (KPNO). The APO 3.5 m telescope is owned and operated by the Astrophysical Research Consortium.

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

    PubMed

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

    2011-08-31

    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.

  19. 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.

  20. CO(J = 3-2) on-the-fly mapping of the nearby spiral galaxies NGC 628 and NGC 7793: Spatially resolved CO(J = 3-2) star-formation law

    NASA Astrophysics Data System (ADS)

    Muraoka, Kazuyuki; Takeda, Miho; Yanagitani, Kazuki; Kaneko, Hiroyuki; Nakanishi, Kouichiro; Kuno, Nario; Sorai, Kazuo; Tosaki, Tomoka; Kohno, Kotaro

    2016-04-01

    We present the results of CO(J = 3-2) on-the-fly mappings of two nearby non-barred spiral galaxies, NGC 628 and NGC 7793, with the Atacama Submillimeter Telescope Experiment at an effective angular resolution of 25″. We successfully obtained global distributions of CO(J = 3-2) emission over the entire disks at a sub-kpc resolution for both galaxies. We examined the spatially resolved (sub-kpc) relationship between CO(J = 3-2) luminosities (L^' }_CO(3-2)) and infrared (IR) luminosities (LIR) for NGC 628, NGC 7793, and M 83, and compared it with global luminosities of a JCMT (James Clerk Maxwell Telescope) Nearby Galaxy Legacy Survey sample. We found a striking linear L^' }_CO(3-2)-LIR correlation over the four orders of magnitude, and the correlation is consistent even with that for ultraluminous IR galaxies and submillimeter-selected galaxies. In addition, we examined the spatially resolved relationship between CO(J = 3-2) intensities (ICO(3-2)) and extinction-corrected star formation rates (SFRs) for NGC 628, NGC 7793, and M 83, and compared it with that for Giant Molecular Clouds in M 33 and 14 nearby galaxy centers. We found a linear ICO(3-2)-SFR correlation with ˜1 dex scatter. We conclude that the CO(J = 3-2) star-formation law (i.e., linear L^' }_CO(3-2)-LIR and ICO(3-2)-SFR correlations) is universally applicable to various types and spatial scales of galaxies; from spatially resolved nearby galaxy disks to distant IR-luminous galaxies, within ˜1 dex scatter.

  1. Environmental Variations in the Atomic and Molecular Gas Radial Profiles of Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Mok, Angus; Wilson, Christine; JCMT Nearby Galaxies Legacy Survey

    2017-01-01

    We present an analysis of the radial profiles of a sample of 43 HI-flux selected spiral galaxies from the Nearby Galaxies Legacy Survey (NGLS) with resolved James Clerk Maxwell Telescope (JCMT) CO J= 3-2 and/or Very Large Array (VLA) HI maps. Comparing the Virgo and non-Virgo populations, we confirm that the HI disks are truncated in the Virgo sample, even for these relatively HI-rich galaxies. On the other hand, the H2 distribution is enhanced for Virgo galaxies near their centres, resulting in higher H2 to HI ratios and steeper H2 and total gas radial profiles. This is likely due to the effects of moderate ram pressure stripping in the cluster environment, which would preferentially remove low density gas in the outskirts while enhancing higher density gas near the centre. Combined with Hα star formation rate data, we find that the star formation efficiency (SFR/H2) is relatively constant with radius for both samples, but Virgo galaxies have a ˜40% lower star formation efficiency than non-Virgo galaxies. These results suggest that the environment of spiral galaxies can play an important role in the formation of molecular gas and the star formation process.

  2. 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}⊙ , 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.

  3. RELATIVE ORIENTATION OF PAIRS OF SPIRAL GALAXIES IN THE SLOAN DIGITAL SKY SURVEY

    SciTech Connect

    Buxton, Jesse; Ryden, Barbara S. E-mail: ryden@astronomy.ohio-state.edu

    2012-09-10

    From our study of binary spiral galaxies in the Sloan Digital Sky Survey Data Release 6, we find that the relative orientation of disks in binary spiral galaxies is consistent with their being drawn from a random distribution of orientations. For 747 isolated pairs of luminous disk galaxies, the distribution of {phi}, the angle between the major axes of the galaxy images, is consistent with a uniform distribution on the interval [0 Degree-Sign , 90 Degree-Sign ]. With the assumption that the disk galaxies are oblate spheroids, we can compute cos {beta}, where {beta} is the angle between the rotation axes of the disks. In the case that one galaxy in the binary is face-on or edge-on, the tilt ambiguity is resolved, and cos {beta} can be computed unambiguously. For 94 isolated pairs with at least one face-on member, and for 171 isolated pairs with at least one edge-on member, the distribution of cos {beta} is statistically consistent with the distribution of cos i for isolated disk galaxies. This result is consistent with random orientations of the disks within pairs.

  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. 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)

  6. 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)

  7. Rotation curves and metallicity gradients from HII regions in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Márquez, I.; Masegosa, J.; Moles, M.; Varela, J.; Bettoni, D.; Galletta, G.

    2002-10-01

    In this paper we study long slit spectra in the region of Hα emission line of a sample of 111 spiral galaxies with recognizable and well defined spiral morphology and with a well determined environmental status, ranging from isolation to non-disruptive interaction with satellites or companions. The form and properties of the rotation curves are considered as a function of the isolation degree, morphological type and luminosity. The line ratios are used to estimate the metallicity of all the detected HII regions, thus producing a composite metallicity profile for different types of spirals. We have found that isolated galaxies tend to be of later types and lower luminosity than the interacting galaxies. The outer parts of the rotation curves of isolated galaxies tend to be flatter than in interacting galaxies, but they show similar relations between global parameters. The scatter of the Tully-Fisher relation defined by isolated galaxies is significantly lower than that of interacting galaxies. The [NII]/Hα ratios, used as a metallicity indicator, show a clear trend between Z and morphological type, t, with earlier spirals showing higher ratios; this trend is tighter when instead of t the gradient of the inner rotation curve, G, is used; no trend is found with the change in interaction status. The Z-gradient of the disks depends on the type, being almost flat for early spirals, and increasing for later types. The [NII]/Hα ratios measured for disk HII regions of interacting galaxies are higher than for normal/isolated objects, even if all the galaxy families present similar distributions of Hα Equivalent Width. Tables 3 and 4 and Figs. 6, 7 and 21 are only available in electronic form at http://www.edpsciences.org. Table 5 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/389 Based on data obtained Asiago/Ekar Observatory. Also based on observations made

  8. High velocity dispersion in a rare grand-design spiral galaxy at redshift z = 2.18.

    PubMed

    Law, David R; Shapley, Alice E; Steidel, Charles C; Reddy, Naveen A; Christensen, Charlotte R; Erb, Dawn K

    2012-07-18

    Although grand-design spiral galaxies are relatively common in the local Universe, only one has been spectroscopically confirmed to lie at redshift z > 2 (HDFX 28; z = 2.011); and it may prove to be a major merger that simply resembles a spiral in projection. The rarity of spirals has been explained as a result of disks being dynamically 'hot' at z > 2 (refs 2-5), which may instead favour the formation of commonly observed clumpy structures. Alternatively, current instrumentation may simply not be sensitive enough to detect spiral structures comparable to those in the modern Universe. At z < 2, the velocity dispersion of disks decreases, and spiral galaxies are more numerous by z ≈ 1 (refs 7, 13-15). Here we report observations of the grand-design spiral galaxy Q2343-BX442 at z = 2.18. Spectroscopy of ionized gas shows that the disk is dynamically hot, implying an uncertain origin for the spiral structure. The kinematics of the galaxy are consistent with a thick disk undergoing a minor merger, which can drive the formation of short-lived spiral structure. A duty cycle of <100 Myr for such tidally induced spiral structure in a hot massive disk is consistent with its rarity.

  9. The Chemical Evolution Carousel of Spiral Galaxies: Azimuthal Variations of Oxygen Abundance in NGC1365

    NASA Astrophysics Data System (ADS)

    Ho, I.-Ting; Seibert, Mark; Meidt, Sharon E.; Kudritzki, Rolf-Peter; Kobayashi, Chiaki; Groves, Brent A.; Kewley, Lisa J.; Madore, Barry F.; Rich, Jeffrey A.; Schinnerer, Eva; D’Agostino, Joshua; Poetrodjojo, Henry

    2017-09-01

    The spatial distribution of oxygen in the interstellar medium of galaxies is the key to understanding how efficiently metals that are synthesized in massive stars can be redistributed across a galaxy. We present here a case study in the nearby spiral galaxy NGC 1365 using 3D optical data obtained in the TYPHOON Program. We find systematic azimuthal variations of the H ii region oxygen abundance imprinted on a negative radial gradient. The 0.2 dex azimuthal variations occur over a wide radial range of 0.3–0.7 R 25 and peak at the two spiral arms in NGC 1365. We show that the azimuthal variations can be explained by two physical processes: gas undergoes localized, sub-kiloparsec-scale self-enrichment when orbiting in the inter-arm region, and experiences efficient, kiloparsec-scale mixing-induced dilution when spiral density waves pass through. We construct a simple chemical evolution model to quantitatively test this picture and find that our toy model can reproduce the observations. This result suggests that the observed abundance variations in NGC 1365 are a snapshot of the dynamical local enrichment of oxygen modulated by spiral-driven, periodic mixing and dilution.

  10. PITCH ANGLE RESTRICTIONS IN LATE-TYPE SPIRAL GALAXIES BASED ON CHAOTIC AND ORDERED ORBITAL BEHAVIOR

    SciTech Connect

    Perez-Villegas, A.; Pichardo, B.; Moreno, E.; Peimbert, A.; Velazquez, H. M.

    2012-01-20

    We built models for low bulge mass spiral galaxies (late type as defined by the Hubble classification) using a three-dimensional self-gravitating model for spiral arms, and analyzed the orbital dynamics as a function of pitch angle, ranging from 10 Degree-Sign to 60 Degree-Sign . Indirectly testing orbital self-consistency, we search for the main periodic orbits and studied the density response. For pitch angles up to approximately {approx}20 Degree-Sign , the response closely supports the potential readily permitting the presence of long-lasting spiral structures. The density response tends to 'avoid' larger pitch angles in the potential by keeping smaller pitch angles in the corresponding response. Spiral arms with pitch angles larger than {approx}20 Degree-Sign would not be long-lasting structures but would rather be transient. On the other hand, from an extensive orbital study in phase space, we also find that for late-type galaxies with pitch angles larger than {approx}50 Degree-Sign , chaos becomes pervasive, destroying the ordered phase space surrounding the main stable periodic orbits and even destroying them. This result is in good agreement with observations of late-type galaxies, where the maximum observed pitch angle is {approx}50 Degree-Sign .

  11. A Technique for Separating the Gravitational Torques of Bars and Spirals in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Buta, R.; Block, D. L.; Knapen, J. H.

    2003-09-01

    We describe a Fourier-based method of separating bars from spirals in near-infrared images. The method takes advantage of the fact that a bar is typically a feature with a relatively fixed position angle and uses the simple assumption that the relative Fourier amplitudes due to the bar decline with radius past a maximum in the same or a similar manner as they rose to that maximum. With such an assumption, the bar can be extrapolated into the spiral region and removed from an image, leaving just the spiral and the axisymmetric background disk light. We refer to such a bar-subtracted image as the ``spiral plus disk'' image. The axisymmetric background (Fourier index m=0 image) can then be added back to the bar image to give the ``bar plus disk'' image. The procedure allows us to estimate the maximum gravitational torque per unit mass per unit square of the circular speed for the bar and spiral forcing separately, parameters that quantitatively define the bar strength Qb and the spiral strength Qs following the recent study of Buta & Block. For the first time, we are able to measure the torques generated by spiral arms alone, and we can now define spiral torque classes, in the same manner as bar torque classes are delineated. We outline the complete procedure here using a 2.1 μm image of NGC 6951, a prototypical SAB(rs)bc spiral having an absolute blue magnitude of -21 and a maximum rotation velocity of 230 km s-1. Comparison between a rotation curve predicted from the m=0 near-infrared light distribution and an observed rotation curve suggests that NGC 6951 is maximum disk in its bar and main spiral region, implying that our assumption of a constant mass-to-light ratio in our analysis is probably reliable. We justify our assumption on how to make the bar extrapolation using an analysis of NGC 4394, a barred spiral with only weak near-infrared spiral structure, and we justify the number of needed Fourier terms using NGC 1530, one of the most strongly barred galaxies

  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. The Role of Interactions in the Evolution of Highly Star-forming Early-Type (Sa-Sab) Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Hameed, Salman; Young, Lisa M.

    2003-06-01

    We present a search for the signatures of galaxy-galaxy interactions in the neutral gas of early-type spirals. New neutral hydrogen observations for four highly star-forming early-type spirals are presented here, along with H I data for three additional galaxies from other sources. H I maps of six of seven galaxies reveal unambiguous signs of a recent encounter, via tidal tails and H I bridges. Most of these galaxies appear undisturbed in the optical, and these interactions probably would have gone unnoticed without H I mapping. Such high rates of interaction suggest that galactic encounters may play an important role in the evolution of early-type spiral galaxies.

  14. The Elaboration of Spiral Galaxies: Morpho-Kinematics Analyses of their Progenitors with IMAGES

    NASA Astrophysics Data System (ADS)

    Hammer, F.; Images Collaboration

    2009-12-01

    The IMAGES (Intermediate MAss Galaxy Evolution Sequence) project aims at measuring the velocity fields of a representative sample of 100 massive galaxies at z=0.4-0.75, selected in the CDFS, the CFRS and the HDFS fields. It uses the world-unique mode of multiple integral field units of FLAMES/ GIRAFFE at VLT. The resolved-kinematics data allow us to sample the large scale motions at ˜ few kpc scale for each galaxy. They have been combined with the deepest HST/ACS, Spitzer (MIPS and IRAC) and VLT/FORS2 ever achieved observations. Most intermediate redshift galaxies show anomalous velocity fields: 6 Gyrs ago, half of the present day spirals were out of equilibrium and had peculiar morphologies. The wealth of the data in these fields allow us to modelize the physical processes in each galaxy with an accuracy almost similar to what is done in the local Universe. These detailed analyses reveal the importance of merger processes, including their remnant phases. Together with the large evolution of spiral properties, this points out the importance of disk survival and strengthens the disk rebuilding scenario. This suggests that the hierarchical scenario may apply to the elaboration of disk galaxies as it does for ellipticals.

  15. 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.

  16. 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.

  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. Stellar disc truncations and extended haloes in face-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Peters, S. P. C.; van der Kruit, P. C.; Knapen, J. H.; Trujillo, I.; Fliri, J.; Cisternas, M.; Kelvin, L. S.

    2017-09-01

    We use data from the IAC Stripe82 Legacy Project to study the surface photometry of 22 nearby, face-on to moderately inclined spiral galaxies. The reprocessed and combined Stripe 82 g',r' and i' images allow us to probe the galaxy down to 29-30 r'-magnitudes arcsec-2 and thus reach into the very faint outskirts of the galaxies. Truncations are found in three galaxies. An additional 15 galaxies are found to have an apparent extended stellar halo. Simulations show that the scattering of light from the inner galaxy by the point spread function (PSF) can produce faint structures resembling haloes, but this effect is insufficient to fully explain the observed haloes. The presence of these haloes and of truncations is mutually exclusive, and we argue that the presence of a stellar halo and/or light scattered by the PSF can hide truncations. Furthermore, we find that the onset of the stellar halo and the truncations scales tightly with galaxy size. Interestingly, the fraction of light does not correlate with dynamic mass. Nineteen galaxies are found to have breaks in their profiles, the radius of which also correlates with galaxy size.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  20. 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

  1. 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.

  2. Updating the (supermassive black hole mass)-(spiral arm pitch angle) relation: a strong correlation for galaxies with pseudobulges

    NASA Astrophysics Data System (ADS)

    Davis, Benjamin L.; Graham, Alister W.; Seigar, Marc S.

    2017-10-01

    We have conducted an image analysis of the (current) full sample of 44 spiral galaxies with directly measured supermassive black hole (SMBH) masses, MBH, to determine each galaxy's logarithmic spiral arm pitch angle, ϕ. For predicting black hole masses, we have derived the relation: log (MBH/M⊙) = (7.01 ± 0.07) - (0.171 ± 0.017)[|ϕ| - 15°]. The total root mean square scatter associated with this relation is 0.43 dex in the log MBH direction, with an intrinsic scatter of 0.30 ± 0.08 dex. The MBH-ϕ relation is therefore at least as accurate at predicting SMBH masses in spiral galaxies as the other known relations. By definition, the existence of an MBH-ϕ relation demands that the SMBH mass must correlate with the galaxy discs in some manner. Moreover, with the majority of our sample (37 of 44) classified in the literature as having a pseudobulge morphology, we additionally reveal that the SMBH mass correlates with the large-scale spiral pattern and thus the discs of galaxies hosting pseudobulges. Furthermore, given that the MBH-ϕ relation is capable of estimating black hole masses in bulge-less spiral galaxies, it therefore has great promise for predicting which galaxies may harbour intermediate-mass black holes (IMBHs, MBH < 105 M⊙). Extrapolating from the current relation, we predict that galaxies with |ϕ| ≥ 26.7° should possess IMBHs.

  3. 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.

  4. 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.

  5. The Infrared Massive Stellar Content of M83

    NASA Astrophysics Data System (ADS)

    Williams, Stephen James; Bonanos, Alceste; Whitmore, Bradley; Prieto, Jose L.; Blair, William P.

    2015-08-01

    We have undertaken a program to detect and categorize the frequency and nature of the mass loss in massive stars like red supergiants (RSGs), yellow supergiants (YSGs), and supergiant Be stars (sgB[e]). Making use of imaging from Spitzer mid infrared (IR), ground-based near-IR from the FourStar instrument on the Magellan Baade telescope, and optical HST WFC3, we have selected the brightest point-like sources in the galaxy M83. Our catalog of near- and mid-IR sources contains 4258 entries across J, KS, Spitzer IRAC 3.6, 4.5, 5.8, and 8.0 micron bands. We employed a combination of photometric criteria in concert with the appearance of candidates in HST optical (U, B, V, I) images to select 49 strong candidates for individual massive stars. Here, we will briefly describe the photometric selection criteria, and the spectroscopic follow-up of 24 probable RSGs from our period 95 approved proposal for VLT/KMOS time (095.D-0189(A)).

  6. 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.

  7. A spectroscopic method for determining the luminosities of spiral galaxies and estimating their stellar population

    NASA Astrophysics Data System (ADS)

    Cowley, A. P.; Crampton, D.; McClure, R. D.

    1982-12-01

    Spectra of the nuclei of 44 normal spiral galaxies have been obtained using the McGraw-Hill Observatory intensified Reticon scanner. A composite spectral index, Σ, has been formed which measures the strengths of Ca II, Hδ , CH, and Mg, all of which correlate with absolute magnitude of the nuclear bulge. It is found that this index can predict the magnitudes of normal galaxies with a dispersion of 0.5 mag. This index is used to show that many galaxies within 6° of the Virgo cluster center, normally assumed to be members, may not be at the mean cluster distance. Using the same instrument, we also obtained fluxed spectra of halo globular clusters and solar neighborhood stars of both Population I and II. These data were used to construct simple population models for the nuclei of late-type spiral galaxies. It was found that, except in the case of the ˜2" semistellar nucleus in M33, the line strengths of Sc galaxy nuclei fit well models constructed from globular cluster observations but could not be reproduced using only a Population I stellar mix. The reverse was true, on the other hand, for the semistellar nucleus of M33, where a good fit is obtained by using young star light plus a smaller contribution from an old metalpoor population. We interpret this to indicate that the predominant light from the amorphous nuclear bulges of late-type spiral nuclei is old, but some of these galaxies may have had recent bursts of star formation that affect the spectral characteristics of a central component of the nucleus.

  8. 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).

  9. A New Dataset of Automatically Extracted Structure of Arms and Bars in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Hayes, Wayne B.; Davis, D.

    2012-05-01

    We present an algorithm capable of automatically extracting quantitative structure (bars and arms) from images of spiral galaxies. We have run the algorithm on 30,000 galaxies and compared the results to human classifications generously provided pre-publication by the Galaxy Zoo 2 team. In all available measures, our algorithm agrees with the humans about as well as they agree with each other. In addition we provide objective, quantitative measures not available in human classifications. We provide a preliminary analysis of this dataset to see how the properties of arms and bars vary as a function of basic variables such as environment, redshift, absolute magnitude, and color. We also show how structure can vary across wavebands as well as along and across individual arms and bars. Finally, we present preliminary results of a measurement of the total angular momentum present in our observed set of galaxies with an eye towards determining if there is a preferred "handedness" in the universe.

  10. 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.

  11. 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

  12. Optical studies of galaxies in clusters. Observations of spirals in Virgo. III.

    NASA Astrophysics Data System (ADS)

    Sperandio, M.; Chincarini, G.; Rampazzo, R.; de Souza, R.

    1995-04-01

    We present the analysis of the rotation curves of a sample of 32 spiral galaxies derived from the spectroscopic observations of a sample of 47 galaxies. For 15 galaxies we were either unable to detect emission lines or measure a reasonably good rotation curve. Of the 32 rotation curves 23 are of galaxies member of the Virgo Cluster and 9 selected from the "field". Analysis of mass and density distribution have been obtained. The mass distribution of cluster galaxies belongs to the Type III proposed by Burstein & Rubin (1985) with few exceptions (NGC 4519 Type I, NGC 2280, NGC 4189, NGC 5861, NGC 6070 Type II) and, is unrelated to the morphological type. Density distribution curves from equidensity surface spheroids model, computed for the Virgo sample, result to be primarily composed of three classes. Rotation curves, none of which shows a peculiar trend, have been parametrized using the criteria introduced by Whitmore et al. (1984). The clustercentric distance of Virgo spirals does not correlate neither with OG nor with OGML in agreement with the findings of Distefano et al. (1990) and Amram et al. (1993, 1994) for other clusters.

  13. 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

  14. 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.

  15. VizieR Online Data Catalog: NIR photometry in 10 nearby spiral galaxies (Grosboel+, 2012)

    NASA Astrophysics Data System (ADS)

    Grosbol, P.; Dottori, H.

    2012-04-01

    Near-infrared (NIR) aperture photometry of sources in 7 arcmin fields around 10 nearby, grand-design spiral galaxies is presented based on HAWK-I/VLT observations. The sources were identified using Sextractor (Bertin & Amouts, 1996A&AS..117..393B) and measured with an aperture of 1 arcsec diameter. The sources numbers are those of the original Sextractor search on the Ks maps and are not strictly sequential. (11 data files).

  16. 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.

  17. REVIEWS OF TOPICAL PROBLEMS: Prediction and discovery of new structures in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Fridman, Aleksei M.

    2007-02-01

    A review is given of the last 20 years of published research into the nature, origin mechanisms, and observed features of spiral-vortex structures found in galaxies. The so-called rotating shallow water experiments are briefly discussed, carried out with a facility designed by the present author and built at the Russian Scientific Center 'Kurchatov Institute' to model the origin of galactic spiral structures. The discovery of new vortex-anticyclone structures in these experiments stimulated searching for them astronomically using the RAS Special Astrophysical Observatory's 6-meter BTA optical telescope, formerly the world's and now Europe's largest. Seven years after the pioneering experiments, Afanasyev and the present author discovered the predicted giant anticyclones in the galaxy Mrk 1040 by using BTA. Somewhat later, the theoretical prediction of giant cyclones in spiral galaxies was made, also to be verified by BTA afterwards. To use the observed line-of-sight velocity field for reconstructing the 3D velocity vector distribution in a galactic disk, a method for solving a problem from the class of ill-posed astrophysical problems was developed by the present author and colleagues. In addition to the vortex structure, other new features were discovered — in particular, slow bars (another theoretical prediction), for whose discovery an observational test capable of distinguishing them from their earlier-studied normal (fast) counterparts was designed.

  18. The effect of host cluster gravitational tidal forces on the internal dynamics of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Mayer, Alexander

    2013-04-01

    New empirical observation by Bidin, Carraro, Mendez & Smith finds ``a lack of dark matter in the Solar neighborhood" (2012 ApJ 751, 30). This, and the discovery of a vast polar structure of Milky Way satellites by Pawlowski, Pflamm-Altenburg & Kroupa (2012 MNRAS 423, 1109), conflict with the prevailing interpretation of the measured Galactic rotation curve. Simulating the dynamical effects of host cluster tidal forces on galaxy disks reveals radial migration in a spiral structure and an orbital velocity that accelerates with increasing galactocentric radial coordinate. A virtual ``toy model,'' which is based on an Earth-orbiting system of particles and is physically realizable in principle, is available at GravitySim.net. Given the perturbing gravitational effect of the host cluster on a spiral galaxy disk and that a similar effect does not exist for the Solar System, the two systems represent distinct classes of gravitational dynamical systems. The observed `flat' and accelerating rotation curves of spiral galaxies can be attributed to gravitational interaction with the host cluster; no `dark matter halo' is required to explain the observable.

  19. Discovery and Study of Spiral Galaxies with Dark Matter in a Series of Clusters in the Northern Galactic Hemisphere

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

    Data from the Merged Catalog of Galaxies (MERCG) are used to study the dynamic characteristics of spiral galaxies with absolute magnitudes M ≥ -20m.6 in the Perseus, A779, and Coma clusters and the Great Wall formation. The diameters of the galaxies from the MERCG were used to determine the radius R D corresponding to the possible radius within which dark matter is concentrated. The dynamic parameters M dyn and M dyn /L B of the spiral galaxies were calculated based on the condition of centrifugal equilibrium. The theory of angular momentum transfer was used to estimate the central surface density m 0 and angular momentum K of stars in the spiral galaxies. A comparison of the dynamic parameters of the spiral galaxies with M ≥ -20m.6 and M ≤ -20m.6 reveals a statistically significant reduction in the number of spiral galaxies with M ≥ -20m.6 that have a larger fraction of dark matter. The following values have been obtained for these clusters: Perseus (35.3%), A779 (17.4%), Coma (12.6%), and Great Wall (23.6%).

  20. The Interacting Galaxies NGC 5394/5395: A Post-Ocular Galaxy and Its Ring/Spiral Companion

    NASA Astrophysics Data System (ADS)

    Kaufman, Michele; Brinks, Elias; Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Klarić , Mario; Struck, Curtis; Thomasson, Magnus; Vogel, Stuart

    1999-10-01

    H I, radio continuum, Fabry-Perot Hα, and ^12CO J=1-->0 observations and broadband optical and near infrared images are presented of the interacting spiral galaxies NGC 5395 and NGC 5394. Kinematically, there are three important, separate components to the H I gas associated with this galaxy pair: (1) the main disk of NGC 5395, (2) a long, northern tidal arm of NGC 5395 distinct in velocity from its main disk, and (3) the disk of NGC 5394. The H I northern tidal arm of NGC 5395 has a line of-sight velocity as much as 75-100 km s^-1 greater than the main disk of NGC 5395 at the same projected location and thus is not in the same plane as the disk. The velocity field of the disk of NGC 5395 is asymmetric and distorted by large-scale and small-scale noncircular motions. In NGC 5395, the encounter appears to be exciting m=1 and m=0 modes in what had been a two-armed spiral. The dominant spiral arm of NGC 5395 forms a large ring or pseudo-ring of Hα, radio continuum, and H I emission, somewhat off center with respect to the nucleus. The H I trough in the center of NGC 5395 is not filled in by molecular gas. The Hα velocity contours exhibit an organized pattern of kinks in crossing the ring and also show streaming motions in a large stellar caustic feature. The eastern side of the ring is brighter in radio continuum and Hα the western side is brighter in H I and contains massive (10^8 M_solar) H I clouds not associated with the most luminous H II regions. The smaller galaxy NGC 5394 is in an immediate post-ocular phase, with a central starburst, an intrinsically oval disk, two long, fairly symmetric, open tidal arms with high arm-interarm contrast, and very bright inner spiral arms, disjoint from the outer tidal arms. Most of the gas in NGC 5394 is in molecular form and concentrated within 3.8 kpc of the center, so is suitable for fueling the starburst. Despite the presence of H I gas, two of the three optically bright inner spiral arms of NGC 5394 show no evidence

  1. 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.

  2. A Numerical Simulation of Star Formation in Nuclear Rings of Barred-Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Seo, Woo-Young; Kim, W.

    2014-01-01

    We use grid-based hydrodynamic simulations to study star formation history in nuclear rings of barred-spiral galaxies. We assume infinitesimally thin, isothermal, and unmagnetized gaseous disk. To investigate effects of spiral arm potential, we calculate both models with and without spiral. We find that star formation rate (SFR) in a nuclear ring is determined by the mass inflow rate to the ring rather than the total gas mass in the ring. In case of models without spiral arms, the SFR shows a strong primary burst at early time, and declines to small values after after that. The primary burst is caused by the rapid gas infall to the ring due to the bar growth. On the other hand, models with spiral arms show multiple star bursts at late time caused by additional gas inflow from outside bar region. When the SFR is low, ages of young star clusters exhibit a bipolar azimuthal gradient along the ring since star formation occurs near the contact points between dust lanes and the nuclear ring. When the SFR is large, there are no age gradient of star clusters since star formation sites are widely distributed throughout the whole ring region.

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

    SciTech Connect

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

    1983-08-01

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

  4. Star formation in grand-design, spiral galaxies. Young, massive clusters in the near-infrared

    NASA Astrophysics Data System (ADS)

    Grosbøl, P.; Dottori, H.

    2012-06-01

    Aims: Spiral structure is a prominent feature in many disk galaxies and is often outlined by bright, young objects. We study the distribution of young stellar clusters in grand-design spiral galaxies and thereby determine whether strong spiral perturbations can influence star formation. Methods: Deep, near-infrared JHK-maps were observed for ten nearby, grand-design, spiral galaxies using HAWK-I at the Very Large Telescope. Complete, magnitude-limited candidate lists of star-forming complexes were obtained by searching within the K-band maps. The properties of the complexes were derived from (H - K) - (J - H) diagrams including the identification of the youngest complexes (i.e. ≲7 Myr) and the estimation of their extinction. Results: Young stellar clusters with ages ≲7 Myr have significant internal extinction in the range of AV = 3-7m, while older ones typically have AV < 1m. The cluster luminosity function (CLF) is well-fitted by a power law with an exponent of around -2 and displays no evidence of a high luminosity cut-off. The brightest cluster complexes in the disk reach luminosities of MK = -15.5m or estimated masses of 106 M⊙. At radii with a strong, two-armed spiral pattern, the star formation rate in the arms is higher by a factor of 2-5 than in the inter-arm regions. The CLF in the arms is also shifted towards brighter MK by at least 0.4m. We also detect clusters with colors compatible with Large Magellanic Cloud intermediate age clusters and Milky Way globular clusters. The (J - K) - MK diagram of several galaxies shows, for the brightest clusters, a clear separation between young clusters that are highly attenuated by dust and older ones with low extinction. Conclusions: The gap in the (J - K) - MK diagrams implies that there has been a rapid expulsion of dust at an age around 7 Myr, possibly triggered by supernovae. Strong spiral perturbations concentrate the formation of clusters in the arm regions and shifts their CLF towards brighter magnitudes

  5. Radio Continuum Mapping of the Spiral Galaxy NGC 4258

    NASA Astrophysics Data System (ADS)

    Calle, Daniel; Hyman, Scott D.; Weiler, Kurt W.; van Dyk, Schuyler D.; Sramek, Richard A.

    1996-05-01

    We have combined numerous, short radio continuum observations of the Seyfert 1 galaxy NGC 4258 (M 106) made at 20 and 6 cm with the Very Large Array (VLA) to produce deep radio maps at these frequencies. These observations were originally taken for monitoring the radio supernova SN 1981K (Weiler et al. 1986, ApJ, 310, 790; Van Dyk et al. 1992, ApJ, 396, 195). The present analysis is analogous to our recent work on NGC 6946 (Hyman et al. 1993, BAAS 25, 1322) and on NGC 4321 (Hyman et al. 1994, BAAS 26, 1498) using observations taken for monitoring SN 1980K and SN 1979C, respectively. The maps we produce for NGC 4258 are of superior sensitivity (sigma ~ lt 0.02 mJy/beam at 6 cm) and spatial resolution ( ~ 0.5" at 6 cm) to those previously published by other investigators (e. g., Turner & Ho 1994, ApJ, 421, 122; Cecil et al. 1995, ApJ, 452, 613). We present preliminary measurements and analyses of the nuclear region, the anomalous arms, and of detected thermal and nonthermal sources throughout the galaxy. We also make comparisons of our radio maps with existing data at other wavelengths and with the results of our analyses of NGC 6946 and NGC 4321.

  6. The onset of large-scale turbulence in the interstellar medium of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Falceta-Gonçalves, D.; Bonnell, I.; Kowal, G.; Lépine, J. R. D.; Braga, C. A. S.

    2015-01-01

    Turbulence is ubiquitous in the interstellar medium (ISM) of the Milky Way and other spiral galaxies. The energy source for this turbulence has been much debated with many possible origins proposed. The universality of turbulence, its reported large-scale driving, and that it occurs also in starless molecular clouds, challenges models invoking any stellar source. A more general process is needed to explain the observations. In this work, we study the role of galactic spiral arms. This is accomplished by means of three-dimensional hydrodynamical simulations which follow the dynamical evolution of interstellar diffuse clouds (˜100 cm-3) interacting with the gravitational potential field of the spiral pattern. We find that the tidal effects of the arm's potential on the cloud result in internal vorticity, fragmentation and hydrodynamical instabilities. The triggered turbulence results in large-scale driving, on sizes of the ISM inhomogeneities, i.e. as large as ˜100 pc, and efficiencies in converting potential energy into turbulence in the range ˜10-25 per cent per arm crossing. This efficiency is much higher than those found in previous models. The statistics of the turbulence in our simulations are strikingly similar to the observed power spectrum and Larson scaling relations of molecular clouds and the general ISM. The dependence found from different models indicate that the ISM turbulence is mainly related to local spiral arm properties, such as its mass density and width. This correlation seems in agreement with recent high angular resolution observations of spiral galaxies, e.g. M51 and M33.

  7. The particle resonance in spiral galaxies - Nonlinear effects.

    NASA Technical Reports Server (NTRS)

    Contopoulos, G.

    1973-01-01

    A theory is developed to account for the nonlinear effects, near the particle resonance, found by numerical integration. There are four equilibrium points in the rotating frame of reference: two of them unstable, at the minima of potential (L1, L2), and two stable, at the maxima of potential (L4, L5). Many particles are trapped in librating orbits around L4, L5. Using the lowest-order terms of a 'third integral' of motion near L4, L5, the behavior of the trapped orbits is determined, and the approximate theoretical results are compared with the orbits found numerically by computer. An estimate of the trapped mass is given. It amounts to about 30% of the total mass between 9 and 11 kpc when the particle resonance is at r sub s = 10 kpc and the maximum force due to the spiral is 4% of the axisymmetric force. Some effects due to these mass concentrations are found numerically and theoretically.

  8. Untangling the magnetic fields in spiral galaxy NGC 6946 with wide-band polarimetry

    NASA Astrophysics Data System (ADS)

    Williams, Anna; Heald, George; Wilcots, Eric M.; Gould Zweibel, Ellen

    2017-01-01

    We present 13 cm polarization observations of nearby spiral galaxy NGC 6946. These data provide a new perspective into the magnetic field structure of this galaxy. Previous observations show strong depolarization between 6 cm and 22 cm, and we show that the morphology of the 13 cm polarization bridges this gap. We combine all available high resolution polarization observations to fit models of the line of sight magnetic field structure across the disk. We find simple screens of Faraday rotation, differential Faraday rotation, and internal Faraday dispersion are insufficient to explain the observed depolarization, and present the results of the best fit models. We discuss how future broadband observations and improved models will help reconstruct the full 3D model of the magnetic field structure in the disks and haloes of galaxies.

  9. Diffuse X-Ray Emission from the Hot ISM in Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Sanders, Wilton

    2002-09-01

    We propose 100-ks observations of two nearby face-on galaxies with the ACIS S3 chip to measure the X-ray emission from their hot ISM. We have selected NGC 3631 and NGC 3938 because of their relatively high star formation rates. Our primary goal is to characterize the spatial distribution and spectral characteristics of the hot interstellar plasma in spiral galaxies similar to the Milky Way. The CXO angular resolution allows us to separate diffuse and point source emission, and the ACIS spectral resolution allows us to find the temperature and abundance parameters of the hot ISM. Other goals are to better understand the diffuse X-ray emission seen in some edge-on galaxy halos, to study the point sources in the galactic disk, and to study the cosmological diffuse background below 0.5 keV.

  10. Inner and outer star forming regions over the discs of spiral galaxies I. Sample characterization

    NASA Astrophysics Data System (ADS)

    Rodríguez-Baras, Marina; Díaz, A. I.; Rosales-Ortega, F. F.

    2017-03-01

    This project is aimed at understanding the dependence of star formation on the environment by analysing young stellar populations in two very different positions in disk galaxies: circumnuclear and outer disk giant regions. Integral field spectroscopy (IFS) provide an ideal means to achieve these goals providing simultaneous spatial and spectral resolution. Here we present the characterization of the work sample, composed by 671 outer regions and 725 inner regions from 263 isolated spirals galaxies observed by the CALIFA survey. The wide number of regions in both samples allows us to obtain statistically relevant results about the influence of metallicity, density and environment on star formation, and how it disseminates over the galaxy, to obtain evolutionary stories for the star-forming regions and to compare our results with models of massive star formation and galactic chemical evolution.

  11. 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.

  12. 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.

  13. The effects of interactions on spiral galaxies. II - Disk star-formation rates

    NASA Technical Reports Server (NTRS)

    Kennicutt, Robert C., Jr.; Roettiger, Kurt A.; Keel, William C.; Van Der Hulst, J. M.; Hummel, E.

    1987-01-01

    H-alpha emission-line and IRAS far-IR observations of interacting spiral and irregular galaxies are here used to assess the influence of interactions on their global star-formation rates. Two samples of interacting galaxies were observed: a complete sample of close pairs, and an Arp atlas sample of peculiar systems. When compared to a control sample of single galaxies, both samples of interacting systems exhibit systematically higher levels of H-alpha and infrared emission on average, and a larger dispersion in emission properties. Emission levels in the very active system are much more strongly correlated with the properties of the interaction than with the internal properties of the galaxies themselves. Strong disk emission is almost always accompanied by unusually strong nuclear activity. Simple star-formation burst models can reproduce the observed H-alpha equivalent widths and broadband colors of most of the galaxies. The bursts are relatively short (few times 10 million yr) and rarely involve more than 1-2 percent of a galaxy's total mass.

  14. Hubble Sees Spiral Bridge of Young Stars Between Two Ancient Galaxies

    NASA Image and Video Library

    2017-09-27

    NASA's Hubble Space Telescope has photographed the dense galaxy cluster SDSS J1531+3414 in the northern constellation Corona Borealis. Made up primarily of giant elliptical galaxies with a few spirals and irregular galaxies thrown in for good measure, the cluster's powerful gravity warps the image of background galaxies into blue streaks and arcs. At the center of the bull's-eye of blue, gravitationally lensed filaments lies a pair of elliptical galaxies that are also exhibiting some interesting features. A 100,000-light-year-long structure that looks like a string of pearls twisted into a corkscrew shape winds around the cores of the two massive galaxies. The "pearls" are superclusters of blazing, blue-white, newly born stars. These super star clusters are evenly spaced along the chain at separations of 3,000 light-years from one another. Read more: 1.usa.gov/1ztQvL9 Credit: NASA/ESA NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  15. ASSOCIATIONS OF HIGH-REDSHIFT QUASI-STELLAR OBJECTS WITH ACTIVE, LOW-REDSHIFT SPIRAL GALAXIES

    SciTech Connect

    Burbidge, G.; Napier, W. M. E-mail: smawmn@cardiff.ac.u

    2009-11-20

    Following the discovery in the 1960s of radio and optical QSOs it was found that some of them lie very close to low-redshift (z <= 0.01) spiral galaxies with separations of approx<2 arcmin. These were discovered both serendipitously by many observers, and systematically by Arp. They are some of the brightest QSOs in radio and optical wavelengths and are very rare. We have carried out a new statistical analysis of most of those galaxy-QSO pairs and find that the configurations have high statistical significance. We show that gravitational microlensing due to stars or other dark objects in the halos of the galaxies apparently cannot account for the excess. Sampling or identification bias likewise seems unable to explain it. Following this up we selected all approx4000 QSOs with g <= 18 from a catalog of confirmed QSOs in the Sloan Digital Sky Survey, and compared them with various subsets of galaxies from the RC 3 galaxy catalog. In contrast to the earlier results, no significant excess of such QSOs was found around these galaxies. Possible reasons for the discrepancy are discussed.

  16. 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.

  17. 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.

  18. The Elaboration of Disk in Spiral Galaxies: Analyses of their Progenitors, 6 Gyrs Ago

    NASA Astrophysics Data System (ADS)

    Hammer, F.; Images Team

    2010-10-01

    The Large program (Intermediate MAss Galaxy Evolution Sequence, IMAGES) aims at measuring the velocity fields of a representative sample of 100 massive galaxies at z=0.4-0.75, taken from the CDFS, the CFRS and the HDFS fields. It uses the unique mode of multiple integral field units of FLAMES/GIRAFFE at VLT. The resolved kinematics data allow to sample the large scale motions at few kpc scale for each individual galaxy. They have been combined with the deepest HST/ACS, Spitzer (MIPS and IRAC) and VLT/FORS2 ever achieved observations. Most intermediate redshift galaxies show anomalous velocity fields implying that, 6 Gyrs ago, half of the present day spirals were out of equilibrium and have peculiar morphologies. The wealth of data in these fields allows to modelize the physical processes in each galaxy with an accuracy almost similar to what is done in the local Universe. These detailed analyses reveal the importance of merger processes, including their remnant phases. It points out the importance of disk survival and it supports the disk rebuilding scenario, suggesting that the hierarchical scenario may apply to the elaboration of disk galaxies as well as it does for ellipticals.

  19. 13CO/C18O Gradients across the Disks of Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Jiménez-Donaire, María J.; Cormier, Diane; Bigiel, Frank; Leroy, Adam K.; Gallagher, Molly; Krumholz, Mark R.; Usero, Antonio; Hughes, Annie; Kramer, Carsten; Meier, David; Murphy, Eric; Pety, Jérôme; Schinnerer, Eva; Schruba, Andreas; Schuster, Karl; Sliwa, Kazimierz; Tomicic, Neven

    2017-02-01

    We use the IRAM Large Program EMPIRE and new high-resolution ALMA data to measure 13CO(1-0)/C18O(1-0) intensity ratios across nine nearby spiral galaxies. These isotopologues of 12CO are typically optically thin across most of the area in galaxy disks, and this ratio allows us to gauge their relative abundance due to chemistry or stellar nucleosynthesis effects. Resolved 13CO/C18O gradients across normal galaxies have been rare due to the faintness of these lines. We find a mean 13CO/C18O ratio of 6.0 ± 0.9 for the central regions of our galaxies. This agrees well with results in the Milky Way, but differs from results for starburst galaxies (3.4 ± 0.9) and ultraluminous infrared galaxies (1.1 ± 0.4). In our sample, the 13CO/C18O ratio consistently increases with increasing galactocentric radius and decreases with increasing star formation rate surface density. These trends could be explained if the isotopic abundances are altered by fractionation; the sense of the trends also agrees with those expected for carbon and oxygen isotopic abundance variations due to selective enrichment by massive stars.

  20. Star Formation Histories across the Interacting Galaxy NGC 6872, the Largest-known Spiral

    NASA Astrophysics Data System (ADS)

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

    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.

  1. The angular momentum of cosmological coronae and the inside-out growth of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Pezzulli, Gabriele; Fraternali, Filippo; Binney, James

    2017-01-01

    Massive and diffuse haloes of hot gas (coronae) are important intermediaries between cosmology and galaxy evolution, storing mass and angular momentum acquired from the cosmic web until eventual accretion onto star forming discs. We introduce a method to reconstruct the rotation of a galactic corona, based on its angular momentum distribution (AMD). This allows us to investigate in what conditions the angular momentum acquired from tidal torques can be transferred to star forming discs and explain observed galaxy-scale processes, such as inside-out growth and the build-up of abundance gradients. We find that a simple model of an isothermal corona with a temperature slightly smaller than virial and a cosmologically motivated AMD is in good agreement with galaxy evolution requirements, supporting hot-mode accretion as a viable driver for the evolution of spiral galaxies in a cosmological context. We predict moderately sub-centrifugal rotation close to the disc and slow rotation close to the virial radius. Motivated by the observation that the Milky Way has a relatively hot corona (T ≃ 2 × 106 K), we also explore models with a temperature larger than virial. To be able to drive inside-out growth, these models must be significantly affected by feedback, either mechanical (ejection of low angular momentum material) or thermal (heating of the central regions). However, the agreement with galaxy evolution constraints becomes, in these cases, only marginal, suggesting that our first and simpler model may apply to a larger fraction of galaxy evolution history.

  2. 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.

  3. 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.

  4. 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.

  5. INVESTIGATING THE NUCLEAR ACTIVITY OF BARRED SPIRAL GALAXIES: THE CASE OF NGC 1672

    SciTech Connect

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

    2011-06-10

    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 D{sub 25} 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 (L{sub X} > 5 x 10{sup 39} erg s{sup -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 ({Gamma} {approx} 1.5) nuclear X-ray source with a 2-10 keV luminosity of 4 x 10{sup 38} erg s{sup -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.

  6. An Expanded HST/WFC3 Survey of M83: Project Overview and Targeted Supernova Remnant Search

    NASA Astrophysics Data System (ADS)

    Blair, William P.; Chandar, Rupali; Dopita, Michael A.; Ghavamian, Parviz; Hammer, Derek; Kuntz, K. D.; Long, Knox S.; Soria, Roberto; Whitmore, Bradley C.; Winkler, P. Frank

    2014-06-01

    We present an optical/NIR imaging survey of the face-on spiral galaxy M83, using data from the Hubble Space Telescope Wide Field Camera 3 (WFC3). Seven fields are used to cover a large fraction of the inner disk, with observations in nine broadband and narrowband filters. In conjunction with a deep Chandra survey and other new radio and optical ground-based work, these data enable a broad range of science projects to be pursued. We provide an overview of the WFC3 data and processing and then delve into one topic, the population of young supernova remnants (SNRs). We used a search method targeted toward soft X-ray sources to identify 26 new SNRs. Many compact emission nebulae detected in [Fe II] 1.644 μm align with known remnants and this diagnostic has also been used to identify many new remnants, some of which are hard to find with optical images. We include 37 previously identified SNRs that the data reveal to be <0.''5 in angular size and thus are difficult to characterize from ground-based data. The emission line ratios seen in most of these objects are consistent with shocks in dense interstellar material rather than showing evidence of ejecta. We suggest that the overall high elemental abundances in combination with high interstellar medium pressures in M83 are responsible for this result. Future papers will expand on different aspects of the these data including a more comprehensive analysis of the overall SNR population. Based on observations 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 NAS5-26555.

  7. An expanded HST/WFC3 survey of M83: Project overview and targeted supernova remnant search

    SciTech Connect

    Blair, William P.; Kuntz, K. D.; Chandar, Rupali; Dopita, Michael A.; Ghavamian, Parviz; Hammer, Derek; Long, Knox S.; Whitmore, Bradley C.; Soria, Roberto; Frank Winkler, P. E-mail: kuntz@pha.jhu.edu E-mail: Michael.Dopita@anu.edu.au E-mail: long@stsci.edu E-mail: whitmore@stsci.edu E-mail: winkler@middlebury.edu

    2014-06-10

    We present an optical/NIR imaging survey of the face-on spiral galaxy M83, using data from the Hubble Space Telescope Wide Field Camera 3 (WFC3). Seven fields are used to cover a large fraction of the inner disk, with observations in nine broadband and narrowband filters. In conjunction with a deep Chandra survey and other new radio and optical ground-based work, these data enable a broad range of science projects to be pursued. We provide an overview of the WFC3 data and processing and then delve into one topic, the population of young supernova remnants (SNRs). We used a search method targeted toward soft X-ray sources to identify 26 new SNRs. Many compact emission nebulae detected in [Fe II] 1.644 μm align with known remnants and this diagnostic has also been used to identify many new remnants, some of which are hard to find with optical images. We include 37 previously identified SNRs that the data reveal to be <0.''5 in angular size and thus are difficult to characterize from ground-based data. The emission line ratios seen in most of these objects are consistent with shocks in dense interstellar material rather than showing evidence of ejecta. We suggest that the overall high elemental abundances in combination with high interstellar medium pressures in M83 are responsible for this result. Future papers will expand on different aspects of the these data including a more comprehensive analysis of the overall SNR population.

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

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

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

  9. 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.

  10. Influence of shear motion on evolution of molecular clouds in the spiral galaxy M 51

    NASA Astrophysics Data System (ADS)

    Miyamoto, Yusuke; Nakai, Naomasa; Kuno, Nario

    2014-04-01

    We have investigated the dynamics of the molecular gas and the evolution of giant molecular associations (GMAs) in the spiral galaxy M 51 with the Nobeyama Radio Observatory 45-m telescope. The velocity components of the molecular gas perpendicular and parallel to the spiral arms are derived at each spiral phase from the distribution of the line-of-sight velocity of the CO gas. In addition, the shear motion in the galactic disk is determined from the velocity vectors at each spiral phase. It is revealed that the distributions of the shear strength and of GMAs are anti-correlated. GMAs exist only in the area of the weak shear strength and further on the upstream side of the high shear strength. GMAs and most giant molecular clouds (GMCs) exist in the regions where the shear critical surface density is smaller than the gravitational critical surface density, indicating that they can stably grow by self-gravity and the collisional agglomeration of small clouds without being destroyed by shear motion. These factors indicate that the shear motion is an important factor in evolution of GMCs and GMAs.

  11. 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.

  12. Simulations of the grand design galaxy M51: a case study for analysing tidally induced spiral structure

    NASA Astrophysics Data System (ADS)

    Dobbs, C. L.; Theis, C.; Pringle, J. E.; Bate, M. R.

    2010-04-01

    We present hydrodynamical models of the grand design spiral M51 (NGC 5194), and its interaction with its companion NGC 5195. Despite the simplicity of our models, our simulations capture the present-day spiral structure of M51 remarkably well, and even reproduce details such as a kink along one spiral arm, and spiral arm bifurcations. We investigate the offset between the stellar and gaseous spiral arms, and find at most times (including the present day) there is no offset between the stars and gas within our error bars. We also compare our simulations with recent observational analysis of M51. We compute the pattern speed versus radius, and similar to observations, find no single global pattern speed. We also show that the spiral arms cannot be fitted well by logarithmic spirals. We interpret these findings as evidence that M51 does not exhibit a quasi-steady density wave, as would be predicted by density wave theory. The internal structure of M51 derives from the complicated and dynamical interaction with its companion, resulting in spiral arms showing considerable structure in the form of short-lived kinks and bifurcations. Rather than trying to model such galaxies in terms of global spiral modes with fixed pattern speeds, it is more realistic to start from a picture in which the spiral arms, while not being simple material arms, are the result of tidally induced kinematic density `waves' or density patterns, which wind up slowly over time.

  13. Understanding the scatter in the spatially resolved star formation main sequence of local massive spiral galaxies

    NASA Astrophysics Data System (ADS)

    Abdurro'uf, Akiyama, Masayuki

    2017-08-01

    We investigate the relation between star formation rate (SFR) and stellar mass (M*) at the sub-galactic scale (∼1 kpc) of 93 local (0.01 < z < 0.02) massive (M* > 1010.5 M⊙) spiral galaxies. To derive a spatially resolved SFR and stellar mass, we perform the so-called pixel-to-pixel spectral energy distribution (SED) fitting, which fits an observed spatially resolved multiband SED with a library of model SEDs using Bayesian statistics. We use two bands (far-ultraviolet or FUV and near-ultraviolet or NUV) and five bands (u, g, r, i and z) of imaging data from Galaxy Evolution Explorer (GALEX) and Sloan Digital Sky Survey (SDSS), respectively. We find a tight nearly linear relation between the local surface density of SFR (ΣSFR) and stellar mass (Σ*), which is flattened at high Σ*. The near linear relation between Σ* and ΣSFR suggests a constant specific SFR (sSFR) throughout the galaxies, and the scatter of the relation is directly related to that of the sSFR. Therefore, we analyse the variation of the sSFR in various scales. More massive galaxies on average have lower sSFR throughout them than less massive galaxies. We also find that barred galaxies have a lower sSFR in the core region than non-barred galaxies. However, in the outer region, the sSFRs of barred and non-barred galaxies are similar and lead to a similar total sSFR.

  14. CO interferometry of gas-rich spiral galaxies in the outskirts of an intermediate redshift cluster

    NASA Astrophysics Data System (ADS)

    Geach, James E.; Smail, Ian; Coppin, Kristen; Moran, Sean M.; Edge, Alastair C.; Ellis, Richard S.

    2009-05-01

    We present IRAM Plateau de Bure Interferometer 3-mm observations of CO J(1 -> 0) emission in two 24-μm selected starburst galaxies in the outskirts (~2-3Rvirial) of the rich cluster Cl0024+16 (z = 0.395). The galaxies' inferred far-infrared luminosities place them in the luminous infrared galaxy (LIRG) class (LFIR > 1011Lsolar), with star formation rates of ~60Msolaryr-1. Strong CO J(1 -> 0) emission is detected in both galaxies, and we use the CO line luminosity to estimate the mass of cold molecular gas, M(H2). Assuming M(H2)/L'CO = 0.8Msolar (Kkm-1pc2)-1, we estimate M(H2) = (5.4-9.1) × 109Msolar for the two galaxies. We estimate the galaxies' dynamical masses from their CO line widths, Mdyn ~ 1-3 × 1010Msolar, implying large cold gas fractions in the galaxies' central regions. At their current rates, they will complete the assembly of M* ~ 1010Msolar and double their stellar mass within as little as ~150Myr. If these galaxies are destined to evolve into S0s, then the short time-scale for stellar mass assembly implies that their major episode of bulge growth occurs while they are still in the cluster outskirts, long before they reach the core regions. Subsequent fading of the disc component relative to the stellar bulge after the gas reservoirs have been exhausted could complete the transformation of spiral-to-S0.

  15. The origin of the ionization of the diffuse interstellar medium in spiral galaxies. I. Photometric measurements

    NASA Astrophysics Data System (ADS)

    Zurita, A.; Rozas, M.; Beckman, J. E.

    2000-11-01

    We present a complete study of the diffuse ionized gas (DIG) in a sample of six spiral galaxies (NGC 157, NGC 3359, NGC 3631, NGC 6764, NGC 6951, NGC 7479) using very high quality Hα images which allow analysis down to very low surface brightness (between 0.3 and 2 pc cm-6). Separation of the diffuse Hα emission from that of the H II regions was performed using the most reliable method: subtracting from the integrated Hα flux of a complete galaxy the contribution from its fully catalogued population of H II regions. The integrated luminosity of the DIG is considerable ( ~ 1040-1042 erg s-1) and is a high fraction of the total Hα emission of each galaxy. Lower and upper limits to the DIG emission in Hα were derived. The lower limits vary from 25% to 50% and the upper limits from 45% to 70%, in our observed sample. Previous studies of a very small number of objects, showed that there is a spatial correlation between the DIG and the H II regions in spiral galaxies suggesting that the DIG is photoionized by Lyman continuum photons (Lyc) which leak from H II regions. Here we go further: we show that the correlation of the DIG is stronger with the most luminous H II regions and we propose a specific model for the ionization of the DIG: we show that the luminosity, in Lyc photons, leaking from the most luminous H II regions is enough to ionize the diffuse gas in a model where the H II regions with luminosities greater than LHα>= 1038.6 erg s-1 are density bounded (Beckman et al. \\cite{gordo}). This model predicts that a fraction of this flux escapes from the galaxy into the surrounding medium.

  16. 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.

  17. 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.

  18. Halos of Spiral Galaxies. I. The Tip of the Red Giant Branch as a Distance Indicator

    NASA Astrophysics Data System (ADS)

    Mouhcine, M.; Ferguson, H. C.; Rich, R. M.; Brown, T. M.; Smith, T. E.

    2005-11-01

    We have imaged the halo populations of a sample of nearby spiral galaxies using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope with the aim of studying the stellar population properties and relating them to those of the host galaxies. In four galaxies, the red giant branch is sufficiently well populated to measure the magnitude of the tip of the red giant branch (TRGB), a well-known distance indicator. Using both the Sobel edge-detection technique and maximum likelihood analysis to measure the I-band magnitude of the TRGB, we determine distances to four nearby galaxies: NGC 253, NGC 4244, NGC 4945, and NGC 4258. For the first three galaxies, the TRGB distance is here determined more directly, and is likely to be more accurate, than previous distance estimates. In the case of NGC 4258, our TRGB distance is in good agreement with the geometrical maser distance, supporting the Large Magellanic Cloud distance modulus (m-M)0=18.50 that is generally adopted in recent estimates of the Hubble constant. Based on observations 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.

  19. SDSS-IV MaNGA: Variation of the Stellar Initial Mass Function in Spiral and Early-type Galaxies

    NASA Astrophysics Data System (ADS)

    Li, Hongyu; Ge, Junqiang; Mao, Shude; Cappellari, Michele; Long, R. J.; Li, Ran; Emsellem, Eric; Dutton, Aaron A.; Li, Cheng; Bundy, Kevin; Thomas, Daniel; Drory, Niv; Lopes, Alexandre Roman

    2017-04-01

    We perform Jeans anisotropic modeling (JAM) on elliptical and spiral galaxies from the MaNGA DR13 sample. By comparing the stellar mass-to-light ratios estimated from stellar population synthesis and from JAM, we find a systematic variation of the initial mass function (IMF) similar to that in the earlier {{ATLAS}}3{{D}} results. Early-type galaxies (elliptical and lenticular) with lower velocity dispersions within one effective radius are consistent with a Chabrier-like IMF, while galaxies with higher velocity dispersions are consistent with a more bottom-heavy IMF such as the Salpeter IMF. Spiral galaxies have similar systematic IMF variations, but with slightly different slopes and larger scatters, due to the uncertainties caused by the higher gas fractions and extinctions for these galaxies. Furthermore, we examine the effects of stellar mass-to-light ratio gradients on our JAM modeling, and we find that the trends become stronger after considering the gradients.

  20. 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

  1. 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.

  2. 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.

  3. Catalog of Observed Tangents to the Spiral Arms in the Milky Way Galaxy

    NASA Astrophysics Data System (ADS)

    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.

  4. Hydrodynamical simulations of the barred spiral galaxy NGC 1300. Dynamical interpretation of observations

    NASA Astrophysics Data System (ADS)

    Lindblad, P. A. B.; Kristen, H.

    1996-09-01

    We perform two-dimensional time dependent hydrodynamical simulations of the barred spiral galaxy NGC 1300. The input potential is divided into an axisymmetric part mainly derived from the observed rotation curve, and a perturbing part obtained from near infrared surface photometry of the bar and spiral structure. Self-gravitation of the gas is not taken into account in our modeling. A pure bar perturbed model is unable to reproduce the observations. It was found necessary to add a weak spiral potential to the perturbation, thus suggesting the presence of massive spiral arms in NGC 1300. We find two models, differing mainly in pattern speed, which are able to reproduce the essentials of NGC 1300. The high pattern speed model has {OMEGA}_p_=20km/s/kpc, corresponding to a corotation radius at R_CR_~104"=1.3R_bar_. Furthermore, the adopted rotation curve for this model supports one ILR at R_ILR_~26" and an OLR at R_OLR_~188". The low pattern speed model has {OMEGA}_p_=12km/s/kpc, corresponding to a corotation radius at R_ CR_~190"=2.4R_bar_. The adopted rotation curve for this model, which differs from the fast pattern speed model, supports one ILR at R_ILR_~25" and an OLR at R_OLR_~305". Morphological features, like spiral arms and offset dust lanes, are basically reproduced by both models. They are driven by orbit crowding effects across various resonances, leading to density enhancements. The general velocity structure, as described by HI data and optical long slit measurements, is fairly consistent with the model velocities.

  5. VizieR Online Data Catalog: Growth curves of CALIFA spiral galaxies (Iglesias-Paramo+, 2016)

    NASA Astrophysics Data System (ADS)

    Iglesias-Paramo, J.; Vilchez, J. M.; Rosales-Ortega, F. F.; Sanchez, S. F.; Duarte Puertas, S.; Petropoulou, V.; Gil de Paz, A.; Galbany, L.; Molla, M.; Catalan-Torrecilla, C.; Castillo Morales, A.; Mast, D.; Husemann, B.; Garcia-Benito, R.; Mendoza, M. A.; Kehrig, C.; Perez-Montero, E.; Papaderos, P.; Gomes, J. M.; Walcher, C. J.; Gonzalez Delgado, R. M.; Marino, R. A.; Lopez-Sanchez, A. R.; Ziegler, B.; Flores, H.; Alves, J.

    2016-09-01

    This paper aims to provide aperture corrections for emission lines in a sample of spiral galaxies from the Calar Alto Legacy Integral Field Area Survey (CALIFA; Sanchez+, 2012A&A...538A...8S) database. In particular, we explore the behavior of the log([OIII]λ5007/Hβ)/([NII]λ6583/Hα) (O3N2) and log[NII]λ6583/Hα (N2) flux ratios since they are closely connected to different empirical calibrations of the oxygen abundances in star-forming galaxies. We compute the median growth curves of Hα, Hα/Hβ, O3N2, and N2 up to 2.5R50 and 1.5 disk Reff. These distances cover most of the optical spatial extent of the CALIFA galaxies. The growth curves simulate the effect of observing galaxies through apertures of varying radii. We split these growth curves by morphological types and stellar masses to check if there is any dependence on these properties. The median growth curve of the Hα flux shows a monotonous increase with radius with no strong dependence on galaxy inclination, morphological type, and stellar mass. The median growth curve of the Hα/Hβ ratio monotonically decreases from the center toward larger radii, showing for small apertures a maximum value of ~10% larger than the integrated one. It does not show any dependence on inclination, morphological type, and stellar mass. The median growth curve of N2 shows a similar behavior, decreasing from the center toward larger radii. No strong dependence is seen on the inclination, morphological type, and stellar mass. Finally, the median growth curve of O3N2 increases monotonically with radius, and it does not show dependence on the inclination. However, at small radii it shows systematically higher values for galaxies of earlier morphological types and for high stellar mass galaxies. Applying our aperture corrections to a sample of galaxies from the SDSS survey at 0.02<=z<=0.3 shows that the average difference between fiber-based and aperture-corrected oxygen abundances, for different galaxy stellar mass and

  6. 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.

  7. On the Effective Oxygen Yield in the Disks of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Zasov, A.; Saburova, A.; Abramova, O.

    2015-12-01

    The factors that influence the chemical evolution of galaxies are poorly understood. Both gas inflow and gas outflow reduce the gas-phase abundance of heavy elements (metallicity), whereas ongoing star formation continuously increases it. To exclude the stellar nucleosynthesis from consideration, we analyze for a sample of 14 spiral galaxies the radial distribution of the effective yield of oxygen yeff, which would be identical to the true stellar yield (per stellar generation) yo if the evolution followed the closed-box model. As the initial data for gas-phase abundance, we used the O/H radial profiles from Moustakas et al., based on two different calibrations (the PT2005 and KK2004 methods). In most of the galaxies with the PT2005 calibration, which we consider the preferred one, the yield yeff in the main disk (R≥slant 0.2 {R}25, where R25 is the optical radius) increases with radius, remaining lower than the empirically found true stellar yield yo. This may indicate the inflow of less-enriched gas predominantly to the inner disk regions, which reduces yeff. We show that the maximal values of the effective yield in the main disks of galaxies, {y}{eff,{max}}, anticorrelate with the total mass of galaxies and with the mass of their dark halos enclosed within R25. It allows us to propose the greater role of gas accretion for galaxies with massive halos. We also found that the radial gradient of oxygen abundance normalized to R25 has a tendency to be shallower in the systems with lower dark halo to stellar mass ratio within the optical radius, which, if confirmed, gives evidence of the effective radial mixing of gas in galaxies with a relatively light dark matter halo.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Ford, H. Alyson; Bregman, Joel N.

    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 1018 cm-2 or greater. This HI gas, which would have been difficult to detect with previous instruments, could be a significant contributor to the missing baryons. The Green Bank Telescope (GBT) presents a unique opportunity to detect this emission. We present results from GBT 21 cm observations of a sample of ten nearby optically luminous spirals, which reveal extended HI gas in half of our sample. The column densities of this extended HI are typically ~ 1 × 1019 cm-2, as measured at distances of 100 kpc from the center of the galaxies.

  10. The radio-far infrared correlation: Spiral and blue compact dwarf galaxies opposed

    NASA Technical Reports Server (NTRS)

    Klein, U.; Wunderlich, E.

    1987-01-01

    The recently established correlation between radio continuum and far infrared emission in galaxies was further investigated by comparing normal spiral and blue compact dwarf galaxies. The puzzling result is that the ratio of radio to far infrared luminosity and its dispersion is the same for both samples, although their ratios of blue to far infrared luminosity, their radio spectral indices and their dust temperatures exhibit markedly different mean values and dispersions. This suggests that the amount of energy radiated in the two regimes is enhanced in the same way although the mechanisms responsible for the two components are rather different and complex. The fact that the blue light does not increase at the same proportion shows that both the radio and the far infrared emission are connected with the recent star formation history.

  11. A Multiwavelength Study of Face-On Spiral Galaxy NGC 3631

    NASA Astrophysics Data System (ADS)

    Keddie-Hill, Crystal; Chomiuk, L.; Freeland, E.; Wilcots, E.

    2007-12-01

    We have undertaken a multiwavelength study of nearby face-on spiral galaxy NGC 3631. Data sets include 21 cm line data from the VLA with 14" resolution, radio continuum data at 6cm and 20 cm with 4" resolution, optical data from the WIYN 3.5m, and Chandra X-ray data. Preliminary results are interesting, including what appears to be a hole in the center of the galaxy in both the Hα and radio continuum images. There is also evidence of tidally removed HI near the edge of the disk. The research is ongoing and was supported in part by the REU and ASSURE programs through NSF award AST-0453442.

  12. Antitruncated stellar light profiles in the outer regions of STAGES spiral galaxies: bulge or disc related?

    NASA Astrophysics Data System (ADS)

    Maltby, David T.; Hoyos, Carlos; Gray, Meghan E.; Aragón-Salamanca, Alfonso; Wolf, Christian

    2012-03-01

    We present a comparison of azimuthally averaged radial surface brightness μ(r) profiles and analytical bulge-disc decompositions (de Vaucouleurs, r1/4 bulge plus exponential disc) for spiral galaxies using Hubble Space Telescope/Advanced Camera for Surveys V-band imaging from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). In the established classification scheme, antitruncated μ(r) profiles (Type III) have a broken exponential disc with a shallower region beyond the break radius rbrk. The excess light at large radii (r > rbrk) can either be caused by an outer exponential disc (Type III-d) or an extended spheroidal component (Type III-s). Using our comparisons, we determine the contribution of bulge light at r > rbrk for a large sample of 78 (barred/unbarred, Sa-Sd) spiral galaxies with outer disc antitruncations (?). In the majority of cases (˜85 per cent), evidence indicates that excess light at r > rbrk is related to an outer shallow disc (Type III-d). Here, the contribution of bulge light at r > rbrk is either negligible (˜70 per cent) or too little to explain the antitruncation (˜15 per cent). However in the latter cases, bulge light can affect the measured disc properties (e.g. μbrk, outer scalelength). In the remaining cases (˜15 per cent), light at r > rbrk is dominated by the bulge (Type III-s). Here, for most cases the bulge profile dominates at all radii and only occasionally (? galaxies, ˜5 per cent) extends beyond that of a dominant disc and explains the excess light at r > rbrk. We thus conclude that in the vast majority of cases antitruncated outer discs cannot be explained by bulge light and thus remain a pure disc phenomenon.

  13. 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.

  14. The structure and evolution of galacto-detonation waves - Some analytic results in sequential star formation models of spiral galaxies

    NASA Technical Reports Server (NTRS)

    Cowie, L. L.; Rybicki, G. B.

    1982-01-01

    Waves of star formation in a uniform, differentially rotating disk galaxy are treated analytically as a propagating detonation wave front. It is shown, that if single solitary waves could be excited, they would evolve asymptotically to one of two stable spiral forms, each of which rotates with a fixed pattern speed. Simple numerical solutions confirm these results. However, the pattern of waves that develop naturally from an initially localized disturbance is more complex and dies out within a few rotation periods. These results suggest a conclusive observational test for deciding whether sequential star formation is an important determinant of spiral structure in some class of galaxies.

  15. THE SPIRAL GALAXY M100 AS SEEN WITH THE HUBBLE'S IMPROVED VISION

    NASA Technical Reports Server (NTRS)

    2002-01-01

    An image of the grand design spiral galaxy M100 obtained with the second generation Wide Field and Planetary Camera (WFPC-2), newly installed in the Hubble Space Telescope. Though the galaxy lies several tens of millions of light-years away, modified optics incorporated within the WFPC-2 allow Hubble to view M100 with a level of clarity and sensitivity previously possible only for the very few nearby galaxies that compose our ``Local Group.'' Just as one does not learn about the diversity of mankind by conversing only with your next door neighbor, astronomers must study many galaxies in a host of different environments if they are to come to understand how our own galaxy, our star, and our earth came to be. By expanding the region of the universe that can be studied in such detail a thousand fold, the WFPC-2 will help the Hubble Space Telescope to fulfill this mission. One of the greatest gains of the high resolution provided by Hubble is the ability to resolve individual stars in other galaxies. The new camera not only allows astronomers to separate stars which would have been blurred together at the resolution available from the ground, but also allows astronomers to accurately measure the light from very faint stars. The quantitative study of compositions, ages, temperatures, and other properties of stars and gas in other galaxies will provide important clues about how galaxies form and evolve. In addition, the WFPC-2 will allow the Hubble Space Telescope to be used to attack one of the most fundamental questions in science: the age and scale of the universe. Astronomers have many ``yardsticks'' for measuring the scale of the universe, but lack a good knowledge of how long these yardsticks really are. M100 is a member of the Virgo Cluster of galaxies. By allowing astronomers to resolve and measure individual stars in the Virgo Cluster -- in particular a special type of star called Cepheid variables, which have well known absolute brightnesses -- HST observations

  16. The stellar content of the nuclei of late-type spiral galaxies

    NASA Astrophysics Data System (ADS)

    Frogel, J. A.

    1985-11-01

    Optical and infrared photometry for nineteen late-type spiral galaxies were used to estimate stellar content in the galactic nuclei. Numerical analysis of the UBVJHK colors and CO and H2O indices showed no correlation between the stellar content of the UBV galaxies and the JHK galaxies. Blue stars from the young stellar systems such as the Magellanic cloud clusters of SWB type I-III (less than about 100 Myr) were found to contribute significantly to the optical light of many of the Sc nuclei in the sample. The infrared light was dominated by an older and probably metal-rich stellar population such as in the Magellanic cloud clusters of the SWB type-IV-VI (a few Gyr) and/or elliptical galaxies. The U-V and V-K colors of the Sc nuclei appeared to be much redder than the nuclei of regions farther out. The gradients are attributed to the radial dependence of internal reddening and the relative number of different types of stars. The optical and infrared photometry of the clusters are given in a table.

  17. Disk and Halo Globular Clusters in the Edge-On Spiral Galaxy NGC 5170

    NASA Astrophysics Data System (ADS)

    Van Der Kruit, Pieter

    1991-07-01

    The system of globular clusters of our Galaxy is known to consist of two sub-systems, the disk and halo sub-systems. The halo sub-system has metal-poor globular clusters, is at most moderately flattened and and is slowly rotating. Ths disk sub-system has more metal-rich globulars, is much flatter and has significant rotation. The latter resembles the ``thick disk' of Gilmore and Wyse. These sub-systems relate to different phases in the formation of the Galaxy; the halo sub-system to the very early phases of Population II formation and the disk-system probably to a stage much later related to disk formation or satellite capture. The structure of the globular cluster system thus contains much information about disk galaxy formation. In this project we will determine how common this phenomenon is. By mapping with WPC the distribution in an edge-on spiral we can uniquely determine the spatial relation of any disk sub-system to the thin disk, which is not possible in our Galaxy or moderately inclined systems (e.g. M31). We will use colors to discriminate between the two sub-systems, since metallicity differences predict a color-index difference in our proposed system of at least 0.6 mag. We will make parallel observations with the FOC to search for outlying clusters and dwarf companions.

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

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

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

  19. The angular momentum of cosmological coronae and the inside-out growth of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Pezzulli, Gabriele; Fraternali, Filippo; Binney, James

    2017-05-01

    Massive and diffuse haloes of hot gas (coronae) are important intermediaries between cosmology and galaxy evolution, storing mass and angular momentum acquired from the cosmic web until eventual accretion on to star-forming discs. We introduce a method to reconstruct the rotation of a galactic corona, based on its angular momentum distribution (AMD). This allows us to investigate in what conditions the angular momentum acquired from tidal torques can be transferred to star-forming discs and explain observed galaxy-scale processes, such as inside-out growth and the build-up of abundance gradients. We find that a simple model of an isothermal corona with a temperature slightly smaller than virial and a cosmologically motivated AMD is in good agreement with galaxy evolution requirements, supporting hot-mode accretion as a viable driver for the evolution of spiral galaxies in a cosmological context. We predict moderately sub-centrifugal rotation close to the disc and slow rotation close to the virial radius. Motivated by the observation that the Milky Way has a relatively hot corona (T ≃ 2 × 106 K), we also explore models with a temperature larger than virial. To be able to drive inside-out growth, these models must be significantly affected by feedback, either mechanical (ejection of low angular momentum material) or thermal (heating of the central regions). However, the agreement with galaxy evolution constraints becomes, in these cases, only marginal, suggesting that our first and simpler model may apply to a larger fraction of galaxy evolution history.

  20. Spiral Galaxies with HST/NICMOS. II. Isophotal Fits and Nuclear Cusp Slopes

    NASA Astrophysics Data System (ADS)

    Seigar, Marc; Carollo, C. Marcella; Stiavelli, Massimo; de Zeeuw, P. Tim; Dejonghe, Herwig

    2002-01-01

    We present surface brightness profiles for 56 of the 78 spiral galaxies observed in the HST/NICMOS2 F160W snapshot survey introduced in Paper I of this series, as well as surface brightness profiles for 23 objects out of the 41 that were also observed in the F110W filter. We fit these surface brightness profiles with the Nuker law of Lauer et al. and use the smooth analytical descriptions of the data to compute the average nuclear stellar cusp slopes <γ> in the 0.1"-0.5" radial range. Our main result is the startling similarity between the nuclear stellar cusp slopes <γ> in the near-infrared compared with those derived in the visual passband. This similarity has several implications: (1) Despite the significant local color variations that are found in the nuclear regions of spirals and that are documented in Paper I, there are typically little or no optical-NIR global color gradients, and thus no global stellar population variations, inside ~50-100 pc from the nucleus in nearby spirals. (2) The large observed range of the strength of the nuclear stellar cusps seen in the HST optical study of spiral galaxies reflects a physical difference between galaxies and is not an artifact caused by nuclear dust and/or recent star formation. (3) The dichotomy between R1/4 bulges, with steep nuclear stellar cusps <γ>~1, and exponential bulges, with shallow nuclear stellar cusps <γ><0.3, is also not an artifact of the effects of dust or recent star formation. (4) The presence of a surrounding massive disk appears to have no effect on the rise of the stellar density distribution within the innermost hundred parsecs of the R1/4 spheroids. These results imply a breakdown within the family of exponential bulges of the nuclear versus global relationships that have been found for the R1/4 spheroids. Such a breakdown is likely to have significant implications concerning the formation of exponential bulges and their connection with the R1/4 spheroids. Based on observations with the

  1. An Atlas of Hubble Space Telescope Spectra and Images of Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Hughes, M. A.; Alonso-Herrero, A.; Axon, D.; Scarlata, C.; Atkinson, J.; Batcheldor, D.; Binney, J.; Capetti, A.; Carollo, C. M.; Dressel, L.; Gerssen, J.; Macchetto, D.; Maciejewski, W.; Marconi, A.; Merrifield, M.; Ruiz, M.; Sparks, W.; Stiavelli, M.; Tsvetanov, Z.; van der Marel, R.

    2003-08-01

    We have observed 54 nearby spiral galaxies with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope to obtain optical long-slit spectra of nuclear gas disks and STIS optical (~R band) images of the central 5''×5'' of the galaxies. These spectra are being used to determine the velocity field of nuclear disks and hence to detect the presence of central massive black holes. Here we present the spectra for the successful observations. Dust obscuration can be significant at optical wavelengths, and so we also combine the STIS images with archival Near-Infrared Camera and Multi-Object Spectrometer H-band images to produce color maps to investigate the morphology of gas and dust in the central regions. We find a great variety in the different morphologies, from smooth distributions to well-defined nuclear spirals and dust lanes. Based on observations 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 NAS5-26555.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    In this work we address the study of the detection in Ha of a radial corrugation in the vertical velocity field in a sample of four nearly face-on, spiral galaxies. The geometry of the problem is a main criterion in the selection of the sample as well as of the azimuthal angle of the slits. These spatial corrugations must be equally associated with wavy vertical motions in the galactic plane with a strong large-scale consistency. Evidence of these kinematic waves were first detected in the analysis of the rotation curves of spiral galaxies (e.g. te{1963ApJ...137..363D,1965BOTT....4....8P}), but it was not until 2001 that te{2001ApJ...550..253A} analyzed in more detail the velocity corrugations in NGC 5427 and a possible physical mechanism for their origin. The aim of this study is to analyze the corrugated velocity pattern in terms of the star formation processes. We describe the geometry of the problem and establish its fundamental relationships.

  3. 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.

  4. Redshift--Independent Distances of Spiral Galaxies: II. Internal Extinction at I Band

    NASA Astrophysics Data System (ADS)

    Giovanelli, R.; Haynes, M. P.; Salzer, J. J.; Wegner, G.; Dacosta, L. N.; Freudling, W.; Chamaraux, P.

    1993-12-01

    We analyze the photometric properties of a sample of 1450 Sbc--Sc galaxies with known redshifts, single--dish HI profiles and CCD I band images to derive laws that relate the measured isophotal radius at mu_I =23.5, magnitude, scale length and HI flux to the face--on aspect. Our results show that the central regions of spiral galaxies are substantially less transparent than most previous determinations suggest, but not as opaque as claimed by Valentijn (1990). Regions in the disk farther than two or three scale lengths from the center are close to completely transparent. In addition to statistically derived relations for the inclination dependence of photometric parameters, we present the results of a modelling exercise that utilizes the ``triplex'' model of Disney et al. (1989). Within the framework of that model, late spiral disks at I band have central optical depths on the order of tau_I ~ 5 and dust absorbing layers with scale heights on the order of half that of the stellar component. We discuss our results in light of previous determinations of internal extinction relations and point out the substantial impact of internal extinction on the scatter of the Tully--Fisher relation. We also find that the visual diameters by which large catalogs are constructed (UGC, ESO--Uppsala) are nearly proportional to face--on isophotal diameters.

  5. SPIRALS, BRIDGES, AND TAILS: A GALAXY EVOLUTION EXPLORER ULTRAVIOLET ATLAS OF INTERACTING GALAXIES

    SciTech Connect

    Smith, Beverly J.; Giroux, Mark L.; Hancock, Mark; Struck, Curtis E-mail: girouxm@etsu.edu E-mail: curt@iastate.edu

    2010-03-15

    We have used the Galaxy Evolution Explorer (GALEX) ultraviolet telescope to study stellar populations and star formation morphology in a well-defined sample of 42 nearby optically selected pre-merger interacting galaxy pairs. Galaxy interactions were likely far more common in the early universe than in the present; thus our study provides a nearby well-resolved comparison sample for high-redshift studies. We have combined the GALEX near-ultraviolet (NUV) and far-ultraviolet images with broadband optical maps from the Sloan Digitized Sky Survey to investigate the ages and extinctions of the tidal features and the disks. The distributions of the UV/optical colors of the tidal features and the main disks of the galaxies are similar; however, the tidal features are bluer on average in NUV - g when compared with their own parent disks; thus tails and bridges are often more prominent relative to the disks in UV images compared to optical maps. This effect is likely due to enhanced star formation in the tidal features compared to the disks rather than reduced extinction; however, lower metallicities may also play a role. We have identified a few new candidate tidal dwarf galaxies in this sample. Other interesting morphologies such as accretion tails and 'beads on a string' are also seen in these images. We also identify a possible 'Taffy' galaxy in our sample, which may have been produced by a head-on collision between two galaxies. In only a few cases are strong tidal features seen in H I maps but not in GALEX.

  6. 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.

  7. H II Regions in Spiral Galaxies: Size Distribution, Luminosity Function, and New Isochrone Diagnostics of Density-Wave Kinematics

    DTIC Science & Technology

    2003-11-01

    conjecture to physical galaxies , placing the corotation where the distribution of H ii regions is seen to end. Tremaine & Weinberg (1984) developed an...H ii REGIONS IN SPIRAL GALAXIES : SIZE DISTRIBUTION, LUMINOSITY FUNCTION, AND NEW ISOCHRONE DIAGNOSTICS OF DENSITY-WAVE KINEMATICS M. S. Oey Lowell...Department of Physics and Astronomy, JohnsHopkins University, 3400 North Charles Street, Baltimore, MD 21218 and Xiaolei Zhang Remote Sensing Division

  8. 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.

  9. Embedded Spiral Patterns in the Cool Core of the Massive Cluster of Galaxies Abell 1835

    NASA Astrophysics Data System (ADS)

    Ueda, Shutaro; Kitayama, Tetsu; Dotani, Tadayasu

    2017-03-01

    We present the properties of an intracluster medium (ICM) in the cool core of the massive cluster of galaxies, Abell 1835, obtained with the data from the Chandra X-ray Observatory. We find distinctive spiral patterns with a radius of 70 kpc (or 18″) as a whole in the residual image of the X-ray surface brightness after the two-dimensional ellipse model of surface brightness is subtracted. The size is smaller by a factor of 2–4 than that of other clusters that are known to have a similar pattern. The spiral patterns consist of two arms. One of them appears as positive, and the other appears as negative excesses in the residual image. Their X-ray spectra show that the ICM temperatures in the positive- and negative-excess regions are {5.09}-0.13+0.12 keV and {6.52}-0.15+0.18 keV, respectively. In contrast, no significant difference is found in the abundance or pressure, the latter of which suggests that the ICM in the two regions of the spiral patterns is near or is in pressure equilibrium. The spatially resolved X-ray spectroscopy of the central region (r< 40\\prime\\prime ), divided into 92 sub-regions indicates that Abell 1835 is a typical cool core cluster. We also find that the spiral patterns extend from the cool core out to the hotter surrounding ICM. The residual image reveals some lumpy substructures in the cool core. The line of sight component of the disturbance velocity that is responsible for the substructures is estimated to be lower than 600 km s‑1. Abell 1835 may now be experiencing an off-axis minor merger.

  10. The Spiral Arm Segments of the Galaxy within 3 kpc from the Sun: A Statistical Approach

    NASA Astrophysics Data System (ADS)

    Griv, Evgeny; Jiang, Ing-Guey; Hou, Li-Gang

    2017-08-01

    As can be reasonably expected, upcoming large-scale APOGEE, GAIA, GALAH, LAMOST, and WEAVE stellar spectroscopic surveys will yield rather noisy Galactic distributions of stars. In view of the possibility of employing these surveys, our aim is to present a statistical method to extract information about the spiral structure of the Galaxy from currently available data, and to demonstrate the effectiveness of this method. The model differs from previous works studying how objects are distributed in space in its calculation of the statistical significance of the hypothesis that some of the objects are actually concentrated in a spiral. A statistical analysis of the distribution of cold dust clumps within molecular clouds, H ii regions, Cepheid stars, and open clusters in the nearby Galactic disk within 3 kpc from the Sun is carried out. As an application of the method, we obtain distances between the Sun and the centers of the neighboring Sagittarius arm segment, the Orion arm segment in which the Sun is located, and the Perseus arm segment. Pitch angles of the logarithmic spiral segments and their widths are also estimated. The hypothesis that the collected objects accidentally form spirals is refuted with almost 100% statistical confidence. We show that these four independent distributions of young objects lead to essentially the same results. We also demonstrate that our newly deduced values of the mean distances and pitch angles for the segments are not too far from those found recently by Reid et al. using VLBI-based trigonometric parallaxes of massive star-forming regions.

  11. Galactic models with massive coronae. V. The spiral SAB galaxy M 81

    NASA Astrophysics Data System (ADS)

    Tenjes, P.; Haud, U.; Einasto, J.

    1998-07-01

    Stellar populations in spiral galaxy M 81 are studied by using modelling. The galaxy is assumed to be stationary and consisting of a superposition of several subsystems. Each subsystem corresponds to a certain stellar/gas/dark matter population with a certain density distribution, chemical composition and kinematical characteristics. We presume that equidensity surfaces of the galactic populations are similar concentric ellipsoids or can be represented as sums of such ellipsoids. The input observational data base consists of surface photometry along the minor and major axis in UBVRI colours, rotation velocities of gas, stellar velocity dispersions, distribution and kinematics of globular clusters, distribution of the young stellar component and gas, kinematics of M 81 satellite galaxies. These data are used to decompose the galaxy into a central nucleus, a metal-rich core and a bulge, a metal-poor halo, an old stellar disk, a young gaseous-stellar disk and a massive dark matter component. Each population is characterized by its ellipticity, radius, mass, luminosity, structure parameter and colour indices. These population parameters are found using the least-squares algorithm. The algorithm minimizes the sum of squares of relative deviations of the model from observations. The values of the parameters were calculated in several steps from a preliminary crude model to the final model. The sensitivity of the population parameters to various observational data is analysed. Particular attention is devoted to the dark matter problem. In the final model the mean mass-to-luminosity ratio of the optically visible parts of the galaxy is found to be M/L_B = 5.4+/- 2.4 M_{sun/Lsun, and the ratio of the total mass to the visible one M_T/M_vis = 44. In the inner regions the best fit with observations is obtained when a central point mass 2.7* 10(8) M_{sun is added to the nucleus.

  12. The 158 micron (CII) mapping of galaxies: Probing the atomic medium

    NASA Technical Reports Server (NTRS)

    Madden, S. C.; Geis, N.; Genzel, R.; Herrmann, F.; Jackson, J.; Poglitsch, A.; Stacey, G. J.; Townes, C. H.

    1993-01-01

    Using the MPE/UCB Far-infrared Imaging Fabry-Perot Interferometer (FIFI) on the Kuiper Airborne Observatory (KAO), we have made large scale maps of (CII) in the spiral galaxies NGC 6946, NGC 891, M83 and the peculiar elliptical Cen A, thus allowing for the first time, detailed studies of the spatial distribution of the FIR line emission in external galaxies. We find that the (CII) emission comes from a mixture of components of interstellar gas. The brightest emission is associated with the nuclear regions, a second component traces the spiral arms as seen in the nearly face on spiral galaxies NGC 6946 and M83 and the largest star forming/H2 regions contained within them, and another extended component of low brightness can be detected in all of the galaxies far from the nucleus, beyond the extent of CO emission.

  13. Modelling resonances and orbital chaos in disk galaxies. Application to a Milky Way spiral model

    NASA Astrophysics Data System (ADS)

    Michtchenko, T. A.; Vieira, R. S. S.; Barros, D. A.; Lépine, J. R. D.

    2017-01-01

    Context. Resonances in the stellar orbital motion under perturbations from the spiral arm structure can play an important role in the evolution of the disks of spiral galaxies. The epicyclic approximation allows the determination of the corresponding resonant radii on the equatorial plane (in the context of nearly circular orbits), but is not suitable in general. Aims: We expand the study of resonant orbits by analysing stellar motions perturbed by spiral arms with Gaussian-shaped groove profiles without any restriction on the stellar orbital configurations, and we expand the concept of Lindblad (epicyclic) resonances for orbits with large radial excursions. Methods: We define a representative plane of initial conditions, which covers the whole phase space of the system. Dynamical maps on representative planes of initial conditions are constructed numerically in order to characterize the phase-space structure and identify the precise location of the co-rotation and Lindblad resonances. The study is complemented by the construction of dynamical power spectra, which provide the identification of fundamental oscillatory patterns in the stellar motion. Results: Our approach allows a precise description of the resonance chains in the whole phase space, giving a broader view of the dynamics of the system when compared to the classical epicyclic approach. We generalize the concept of Lindblad resonances and extend it to cases of resonant orbits with large radial excursions, even for objects in retrograde motion. The analysis of the solar neighbourhood shows that, depending on the current azimuthal phase of the Sun with respect to the spiral arms, a star with solar kinematic parameters (SSP) may evolve in dynamically distinct regions, either inside the stable co-rotation resonance or in a chaotic zone. Conclusions: Our approach contributes to quantifying the domains of resonant orbits and the degree of chaos in the whole Galactic phase-space structure. It may serve as a

  14. 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

  15. The H I column density power spectrum of six nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Dutta, Prasun; Bharadwaj, Somnath

    2013-11-01

    We propose a method to determine the power spectrum of H I column density fluctuations using radio-interferometric observations of 21-cm emission from the interstellar medium of galaxies. We have used this to estimate the power spectra of six nearly face-on nearby spiral galaxies. Earlier work has shown that these power spectra are well fitted by power laws with slopes around -1.6 across length-scales ˜1 to ˜10 kpc, the amplitude however was undetermined. In this work, we have determined the amplitude of the H I column density power spectrum. We find that the H I column density NHI expressed in units of 1020 cm-2 has mean square fluctuations in the range ˜0.03 to ˜20. The amplitude of the power spectrum is found to be tightly correlated with the H I mass fraction of the galaxies. The physical process responsible for these scale-invariant fluctuations is, however, at present not known.

  16. The fluorescence-dominated X-ray spectrum of the spiral galaxy NGC 6552

    NASA Technical Reports Server (NTRS)

    Fukazawa, Yasushi; Makishima, Kazuo; Ebisawa, Ken; Fabian, Andrew C.; Gendreau, Keith C.; Ikebe, Yasushi; Iwasawa, Kazushi; Kii, Tsuneo; Mushotzky, Richard F.; Ohashi, Takaya

    1994-01-01

    A hard X-ray source with a 2-10 keV flux of approximately 6 x 10(exp -13) ergs/sec/sq cm was detected with ASCA in the north ecliptic pole region. It is identified with the spiral galaxy NGC 6552 at a redshift of z = 0.026, which is optically classified as a Seyfert 2 galaxy. The X-ray spectrum consists of a series of atomic K-emission lines from (nearly-) neutral species of at least seven abundant elements, and a heavily absorbed (N(sub H) approx. = 6 x 10(exp 23)/sq cm) hard continuum. The iron line has an equivalent width as large as approximately 0.9 keV. Our results show that NGC 6552 is an extreme type 2 Seyfert galaxy, in which the fluorescent lines are produced when hard X-rays from a hidden active nucleus are reflected off thick cool matter into our line of sight. The intrinsic 2-10 keV luminosity of the nucleus is estimated to be at least 6 x 10(exp 42) ergs/s.

  17. 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

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

    NASA Astrophysics Data System (ADS)

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

    2001-03-01

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

  19. 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

  20. GLOBULAR CLUSTERS AND SPUR CLUSTERS IN NGC 4921, THE BRIGHTEST SPIRAL GALAXY IN THE COMA CLUSTER

    SciTech Connect

    Lee, Myung Gyoon; Jang, In Sung E-mail: isjang@astro.snu.ac.kr

    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 × 10{sup 5} M{sub ⊙}. 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 M{sub I} (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, H{sub 0} = 77.9 ± 3.6 km s{sup −1} Mpc{sup −1}. We estimate the GC specific frequency of NGC 4921 to be S{sub N} = 1.29 ± 0.25, close to the values for early-type galaxies. This indicates that NGC 4921 is in the transition phase to S0s.

  1. 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.

  2. Caught in the act: Cluster `k+a' galaxies as a link between spirals and S0s

    NASA Astrophysics Data System (ADS)

    Rodriguez Del Pino, B.; Bamford, S. P.; Aragón-Salamanca, A.; Milvang-Jensen, B.; Merrifield, M. R.; Balcells, M.

    2015-05-01

    We use integral field spectroscopy of 13 disk galaxies in the cluster AC114 at z ˜ 0.31 in an attempt to disentangle the physical processes responsible for the transformation of spiral galaxies in clusters. Our sample is selected to display a dominant young stellar population, as indicated by strong Hδ absorption lines in their integrated spectra. Most of our galaxies lack the [OII]λ3727 emission line, and hence ongoing star formation. They therefore possess `k+a' spectra, indicative of a recent truncation of star formation, possibly preceded by a starburst. Disky `k+a' galaxies are a promising candidate for the intermediate stage of the transformation from star-forming spiral galaxies to passive S0s. Our observations allow us to study the spatial distributions and the kinematics of the different stellar populations within the galaxies. We used three different indicators to evaluate the presence of a young population: the equivalent width of Hδ, the luminosity-weighted fraction of A stars, and the fraction of the galaxy light attributable to simple stellar populations with ages between 0.5 and 1.5 Gyr. We find a mixture of behaviours, but are able to show that in most of galaxies the last episode of star-formation occurred in an extended disk, similar to preceding generations of stars, though somewhat more centrally concentrated. We thus exclude nuclear starbursts and violent gravitational interactions as causes of the star formation truncation. Gentler mechanisms, such as ram-pressure stripping or weak galaxy-galaxy interactions, appear to be responsible for ending star-formation in these intermediate-redshift cluster disk galaxies.

  3. Caught in the act: cluster `k+a' galaxies as a link between spirals and S0s

    NASA Astrophysics Data System (ADS)

    Rodríguez Del Pino, Bruno; Bamford, Steven P.; Aragón-Salamanca, Alfonso; Milvang-Jensen, Bo; Merrifield, Michael R.; Balcells, Marc

    2014-02-01

    We use integral field spectroscopy of 13 disc galaxies in the cluster AC114 at z ˜ 0.31 in an attempt to disentangle the physical processes responsible for the transformation of spiral galaxies in clusters. Our sample is selected to display a dominant young stellar population, as indicated by strong Hδ absorption lines in their integrated spectra. Most of our galaxies lack the [O II]λ3727 emission line, and hence ongoing star formation. They therefore possess `k+a' spectra, indicative of a recent truncation of star formation, possibly preceded by a starburst. Discy `k+a' galaxies are a promising candidate for the intermediate stage of the transformation from star-forming spiral galaxies to passive S0s. Our observations allow us to study the spatial distributions and the kinematics of the different stellar populations within the galaxies. We used three different indicators to evaluate the presence of a young population: the equivalent width of Hδ, the luminosity-weighted fraction of A stars, and the fraction of the galaxy light attributable to simple stellar populations with ages between 0.5 and 1.5 Gyr. We find a mixture of behaviours, but are able to show that in most of the galaxies the last episode of star formation occurred in an extended disc, similar to preceding generations of stars, though somewhat more centrally concentrated. We thus exclude nuclear starbursts and violent gravitational interactions as causes of the star formation truncation. Gentler mechanisms, such as ram-pressure stripping or weak galaxy-galaxy interactions, appear to be responsible for ending star formation in these intermediate-redshift cluster disc galaxies.

  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. 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

  6. Observational Manifestation of Chaos in the Gaseous Disk of the Grand Design Spiral Galaxy NGC 3631

    NASA Astrophysics Data System (ADS)

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

    2002-10-01

    The main goal of the paper is to demonstrate the presence of chaotic trajectories in the gaseous disk of a real spiral galaxy. As an example we have chosen NGC 3631. First, we show the stationarity of the 3-D velocity field restored from the observed line-of-sight velocity field of the gaseous disk. That allows to analyse behaviour of the trajectories of the fluid particles (gas clouds) in the disk, calculating the corresponding observed streamlines. We estimate the Lyapunov characteristic numbers using their independence of the metrics and show the existence of chaotic trajectories outside the vortices which are present in the velocity field, and in the vicinity of the saddle point. Related spectra of the stretching numbers for some trajectories are also calculated.

  7. EVN VLBI Imaging of the Jet in the Nucleus of the Barred Spiral Galaxy NGC 7479

    NASA Astrophysics Data System (ADS)

    Laine, Seppo J.; Momjian, Emmanuel; Krichbaum, Thomas; Beck, Rainer; Komossa, S.

    2017-01-01

    The nearby (D = 32 Mpc) barred spiral galaxy NGC 7479 hosts a remarkable jet-like radio continuum feature: bright, 12-kpc long in projection, and hosting an S-shaped, aligned magnetic field. The bending of the jet in 3-D is most easily explained by precession, with a jet age less than a million years. We have imaged the nucleus with European VLBI Network (EVN) observations at 6 and 18 cm. Here we report our tentative results on the search for nuclear jet emission on sub-arcsecond scales, including its alignment with the outer kpc-scale jet. We also describe the nature of the nucleus with the help of spectral index determination, brightness temperature limit and variability of the nucleus.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. Revealing a spiral-shaped molecular cloud in our galaxy: Cloud fragmentation under rotation and gravity

    NASA Astrophysics Data System (ADS)

    Li, Guang-Xing; Wyrowski, Friedrich; Menten, Karl

    2017-02-01

    The dynamical processes that control star formation in molecular clouds are not well understood, and in particular, it is unclear if rotation plays a major role in cloud evolution. We investigate the importance of rotation in cloud evolution by studying the kinematic structure of a spiral-shaped Galactic molecular cloud G052.24+00.74. The cloud belongs to a large filament, and is stretching over 100 pc above the Galactic disk midplane. The spiral-shaped morphology of the cloud suggests that the cloud is rotating. We have analysed the kinematic structure of the cloud, and study the fragmentation and star formation. We find that the cloud exhibits a regular velocity pattern along west-east direction - a velocity shift of 10km s-1 at a scale of 30 pc. The kinematic structure of the cloud can be reasonably explained by a model that assumes rotational support. Similarly to our Galaxy, the cloud rotates with a prograde motion. We use the formalism of Toomre (1964) to study the cloud's stability, and find that it is unstable and should fragment. The separation of clumps can be consistently reproduced assuming gravitational instability, suggesting that fragmentation is determined by the interplay between rotation and gravity. Star formation occurs in massive, gravitational bound clumps. Our analysis provides a first example in which the fragmentation of a cloud is regulated by the interplay between rotation and gravity.

  13. 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.

  14. The Molecular Gas Excitation and Mass in Edge-On Spiral Galaxies: Constraining the Physical Parameters

    NASA Astrophysics Data System (ADS)

    Stacey, Gordon; Charmandaris, Vassilis; Higdon, Sarah; Nikola, Thomas

    2008-03-01

    We propose to accurately trace molecular gas excitation and mass along the plane of the two nearby nearby edge-on spiral galaxies, NGC 4905 and 5907 through deep IRS spectroscopy of four pure rotational lines (S(3), S(2), S(1), and S(0)) of H2. Our primary goal is to investigate the physical state, mass, and heating processes in the molecular ISM in these galaxies, and compare them with our on-going study of the edge-on galaxy NGC 891. Prior modeling of the S(1) and S(0) emission from NCG 891 suggests an enormous amount of cool (T< 90K) H2 (5 to 15 times the atomic mass) for this galaxy if the ortho to para H2 ratio is 3. However, these models are hampered by the degeneracy between gas excitation and the (assumed) o/p ratio. Including the S(3) and S(2) lines in the analysis breaks the degeneracy, enabling independent determination of gas excitation for the ortho and para species, and a measure of the o/p ratio. Using three lines (S(2), S(1), and S(0)) for NGC 891, we find gas excitation near 220 K, with an o/p ratio near unity, resulting in greatly reduced molecular gas mass. We were awarded time in Cycle 4 to verify this model through deeper integrations of the S(0), S(1), and S(2) lines, and observations of the S(3) line in NGC 891. {These observations have not yet been scheduled}. Here we propose to extend our study by mapping all four lines in the disks of galaxies with different gas contents than NGC 891: the early type Sb NGC 4565 and the late type Sc NGC 5907. We are particularly intrigued with the regions outside of the CO emitting disk where the gas is likely not heated in a PDR scenario but rather by modest velocity cloud-cloud collisions in the outer galaxy. The proposed observations address the heating source as the ortho and para ratio depends on the formation temperature: a larger ratio indicates a larger formation temperature. Did H2 form in a relatively warm far-UV bathed environment near stars, or in a cold environment devoid of young stars?

  15. 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).

  16. ON THE INTRINSIC ALIGNMENTS OF THE LATE-TYPE SPIRAL GALAXIES FROM THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 7

    SciTech Connect

    Lee, Jounghun

    2011-05-10

    A robust detection of the tidally induced intrinsic alignments of the late-type spiral galaxies with high statistical significance is reported. From the spectroscopic galaxy sample of Sloan Digital Sky Survey DR7 compiled by Huertas-Company et al., which lists each galaxy's probabilities of being in five Hubble types, P(E), P(Ell), P(S0), P(Sab), P(Scd), we select the nearby large late-type spiral galaxies which have redshifts of 0 {<=} z {<=} 0.02, probabilities of P(Scd) {>=} 0.5, and angular sizes of D {>=} 7.92 arcsec. The spin axes of the selected nearby large late-type spiral galaxies are determined up to the two-fold ambiguity with the help of the circular thin-disk approximation, and their spatial correlations are measured as a function of the separation distance r. A clear signal of the intrinsic correlation as high as 3.4{sigma} and 2.4{sigma} is found at the separation distance of r {approx} 1 h{sup -1} Mpc and r {approx} 2 h{sup -1} Mpc, respectively. The comparison of this observational results with the analytic model based on the tidal torque theory reveals that the spin correlation function for the late-type spiral galaxies follows the quadratic scaling of the linear density correlation and that the intrinsic correlations of the galaxy spin axes are stronger than that of the underlying dark halos. We investigate a local density dependence of the galaxy spin correlations and found that the correlations are stronger for the galaxies located in dense regions having more than 10 neighbors within 2 h{sup -1} Mpc. We also attempt to measure a luminosity dependence of the galaxy spin correlations, but find that it is impossible with our magnitude-split samples to disentangle a luminosity from a redshift dependence. We provide the physical explanations for these observational results and also discuss the effects of possible residual systematics on the results.

  17. SPATIALLY RESOLVED KINEMATICS OF THE CENTRAL REGIONS OF M83: HIDDEN MASS SIGNATURES AND THE ROLE OF SUPERNOVAE

    SciTech Connect

    Piqueras Lopez, J.; Colina, L.; Davies, R.; Orban de Xivry, G.

    2012-06-10

    The barred grand-design spiral M83 (NGC 5236) is one of the most studied galaxies given its proximity, orientation, and particular complexity. Nonetheless, many aspects of the central regions remain controversial, conveying our limited understanding of the inner gas and stellar kinematics, and ultimately of the nucleus evolution. In this work, we present AO VLT-SINFONI data of its central {approx}235 Multiplication-Sign 140 pc with an unprecedented spatial resolution of {approx}0.2 arcsec, corresponding to {approx}4 pc. We have focused our study on the distribution and kinematics of the stars and the ionized and molecular gas by studying the Pa{alpha} and Br{gamma} emission in detail, the H{sub 2} 1-0S(1) line at 2.122 {mu}m, and the [Fe II] line at 1.644 {mu}m, together with the CO absorption bands at 2.293 {mu}m and 2.323 {mu}m. Our results reveal a complex situation where the gas and stellar kinematics are totally unrelated. Supernova explosions play an important role in shaping the gas kinematics, dominated by shocks and inflows at scales of tens of parsecs that make them unsuitable to derive general dynamical properties. We propose that the location of the nucleus of M83 is unlikely to be related to the off-center 'optical nucleus'. The study of the stellar kinematics reveals that the optical nucleus is a gravitationally bound massive star cluster with M{sub dyn} = (1.1 {+-} 0.4) Multiplication-Sign 10{sup 7} M{sub Sun }, formed by a past starburst. The kinematic and photometric analysis of the cluster yield that the stellar content of the cluster is well described by an intermediate age population of log T(yr) = 8.0 {+-} 0.4, with a mass of M* {approx_equal} (7.8 {+-} 2.4) Multiplication-Sign 10{sup 6} M{sub Sun }.

  18. Prospecting for Elements: Galactic Halo Planetary Nebulae Abundances and Virgo Spiral Galaxy Color Profiles

    NASA Astrophysics Data System (ADS)

    Howard, Joseph William

    Halo planetary nebulae. Using published spectral line data for nine halo planetary nebulae (HPNe), I have calculated photoionization models in an attempt to gain insight into the physical conditions and chemical abundances of these nebulae. The nine HPNE reported upon are K648, DdDm-1, NGC2242, NGC4361, PN243.8-37.1, PN006-41.9, M2-29, BB-1, and H4-1. The derived abundance ranges for the HPNe are: C 6.60-8.95, N 7.18-8.00, O 7.56-8.56, Ne 6.24-7.71, Ar 4.12-7.70, and S 4.90-7.00 (log(x) + 12). The temperature range for the central stars of these nebulae is 40,000 to 140,000K. Specifically, with a few exceptions, I find that all nine objects exhibit subsolar O/H; most show enhanced C/O and N/O, and a constant Ne/O ration. I also note the existence of comparatively larger abundance scatter in the HPNe as opposed to disk PNe, and suggest that this is consistent with the accretion model of halo formation formulated by Searle & Zinn. In addition, I test the effects on derived abundances and central star temperatures of a variety of model atmospheres as well as blackbodies for input ionizing spectra. I find that nebular line strengths are relatively insensitive to atmospheric details; thus blackbody spectra are suitable for central star continua. Near-infrared Virgo cluster spiral colors. Near-infrared (NIR) surface photometry in J (1.2μm), H (1.6μm) and K (2.2μm) have been obtained for a sample of Virgo cluster spirals; NGC4321, NGC4303, NGC4571, NGC4689, and NGC4254 which span a large range in HI deficiency. The spirals range from a normal gas content to a deficiency of a factor of 10 compared to normal galaxies. Using previous HII region abundance studies along with the NIR colors an attempt has been made to calibrate any correlation between the J-K index to the overall gas phase abundance gradients as a first step to probing the underlying stellar metallicity. Decomposition techniques have been used to produce estimates of spiral bulge/disk masses and luminosities

  19. 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.

  20. Gas and Stellar Kinematics in the Giant Spiral Galaxy NGC 1961

    NASA Astrophysics Data System (ADS)

    Sacash, Brian; Pinkney, Jason

    2009-04-01

    Long-slit spectroscopy and CCD imaging from the Hubble Space Telescope and the MDM Observatory is presented for the massive spiral galaxy NGC 1961. We aimed to measure the mass of the central supermassive black hole (SMBH). We have developed our own software for spectral extraction and for the fitting of absorption and emission lines. The program subtracts the absorption-line (stellar) component from the emission-line spectra to improve the fidelity of our emission line measurements. We present our line centroids (velocities), widths (velocity dispersions), and strengths for the most prominent emission lines (Hα, [NII], and [SII]). The rotation curve from the ground-based data is in good agreement with previous work by Rubin (1979); its asymmetric appearance suggests a tidal interaction or merger. We use the rotation curve and surface photometry to estimate the enclosed mass profile of the galaxy. The emission lines near the nucleus broaden indicating more intrinsic dispersion than expected for a cold, gas disk. We estimate the BH mass using simple gas disk models. However, the high dispersion and the asymmetry in its inner rotation curve suggest that this approach is unreliable.

  1. Building Late-type Spiral Galaxies by In-situ and Ex-situ Star Formation

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-05-01

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

  3. 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.

  4. Evidence for azimuthal variations of the oxygen-abundance gradient tracing the spiral structure of the galaxy HCG 91c

    NASA Astrophysics Data System (ADS)

    Vogt, F. P. A.; Pérez, E.; Dopita, M. A.; Verdes-Montenegro, L.; Borthakur, S.

    2017-05-01

    Context. The distribution of elements in galaxies forms an important diagnostic tool to characterize these systems' formation and evolution. This tool is, however, complex to use in practice, as galaxies are subject to a range of simultaneous physical processes active from pc to kpc scales. This renders observations of the full optical extent of galaxies down to sub-kpc scales essential. Aims: Using the WiFeS integral field spectrograph, we previously detected abrupt and localized variations in the gas-phase oxygen abundance of the spiral galaxy HCG 91c. Here, we follow-up on these observations to map HCG 91c's disk out to 2 Re at a resolution of 600 pc, and characterize the non-radial variations of the gas-phase oxygen abundance in the system. Methods: We obtained deep MUSE observations of the target under 0.6 arcsec seeing conditions. We perform both a spaxel-based and aperture-based analysis of the data to map the spatial variations of 12 +log (O/H) across the disk of the galaxy. Results: We confirm the presence of rapid variations of the oxygen abundance across the entire extent of the galaxy previously detected with WiFeS, for all azimuths and radii. The variations can be separated in two categories: a) localized and associated with individual H ii regions; and b) extended over kpc scales, and occurring at the boundaries of the spiral structures in the galaxy. Conclusions: Our MUSE observations suggest that the enrichment of the interstellar medium in HGC 91c has proceeded preferentially along spiral structures, and less efficiently across them. Our dataset highlights the importance of distinguishing individual star-forming regions down to scales of a few 100 pc when using integral field spectrographs to spatially resolve the distribution of oxygen abundances in a given system, and accurately characterize azimuthal variations and intrinsic scatter. The movie associated to Fig. 8 is available at http://www.aanda.org

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  6. 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

  7. 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.

  8. Distribution and motions of H I and H_2_ in the peculiar spiral galaxy NGC 3310.

    NASA Astrophysics Data System (ADS)

    Mulder, P. S.; van Driel, W.; Braine, J.

    1995-08-01

    galaxy exhibits highly non-circular motions, with radial velocity deviations up to 120km/s. The observed H I kinematics are most naturally explained as due to a recent merger of NGC 3310 with a gas-rich dwarf galaxy. While being quite normal in its optical and H I global properties, NGC 3310 has an exceptionally low rotation velocity at radii near its de Vaucouleurs' radius (~80km/s), and hence a very low dynamical mass inside that radius (~2x10^10^Msun_). This may indicate that the pre-merger object was a dwarf spiral galaxy. The CO observations show that NGC 3310 has rather weak CO emission, implying a low H_2_ mass if a standard conversion is appropriate. If so, the ratio of H_2_ to H I gas mass is typical for a very late-type spiral, once more suggesting a recent merger with such an object. The ratio of CO(2-1) to CO(1-0) emission is exceptionally high. This may be due to the CO(1-0) line being optically thin. Combined with a low metallicity, a strong UV radiation field and a high dust temperature in the interstellar medium, this probably results in a CO flux to molecular hydrogen column density conversion factor lower than Galactic, closer to that found in the Magellanic clouds.

  9. Bridging the Gap from Galactic to Extragalactic: Star Formation and Giant Molecular Clouds within the Nearby Spiral Galaxy NGC 300

    NASA Astrophysics Data System (ADS)

    Faesi, Christopher

    2017-01-01

    The questions surrounding the origins of stars are of key importance in astrophysics across a huge range in physical scales. However, until recently, investigations have been restricted to either detailed studies targeting a few nearby regions in the Milky Way, or kpc- or larger-scale studies of entire galaxies. Between these two scales lies a crucial gap in understanding. In this thesis work, I have taken steps in bridging this gap between Galactic and extragalactic star formation. I will present the results of a campaign of observations and modeling targeting the nearby spiral galaxy NGC 300. Using an extensive suite of multi-wavelength data I have characterized the star formation activity and molecular gas in a large sample of star-forming regions within this galaxy. Additionally, I have assembled an extensive (300 clouds) and high resolution (10 pc) catalog of Giant Molecular Clouds (GMCs) based on ALMA CO observations. This unprecedented look at the population of GMCs in a nearby spiral galaxy reveals an astonishing range of morphologies and properties in the Molecular Gas as well as providing a key testbed for comparison with GMCs in the Milky Way and other nearby galaxies. The GMCs in NGC 300 appear to have similar global properties and show scaling relations consistent with those seen in the Milky Way. Furthermore, the star formation rate appears to correlate with the mass of molecular gas with approximately 250 Gyr depletion time, extending the relation discovered in the Milky Way linearly to larger scales. These results suggest a level of universality in the star formation process within spiral galaxy disks like our own Milky Way.

  10. The Relation between Globular Cluster Systems and Supermassive Black Holes in Spiral Galaxies: The Case Study of NGC 4258

    NASA Astrophysics Data System (ADS)

    González-Lópezlira, Rosa A.; Lomelí-Núñez, Luis; Álamo-Martínez, Karla; Órdenes-Briceño, Yasna; Loinard, Laurent; Georgiev, Iskren Y.; Muñoz, Roberto P.; Puzia, Thomas H.; Bruzual A., Gustavo; Gwyn, Stephen

    2017-02-01

    We aim to explore the relationship between globular cluster total number, {N}{GC}, and central black hole mass, M •, in spiral galaxies, and compare it with that recently reported for ellipticals. We present results for the Sbc galaxy NGC 4258, from Canada-France-Hawaii Telescope data. Thanks to water masers with Keplerian rotation in a circumnuclear disk, NGC 4258 has the most precisely measured extragalactic distance and supermassive black hole mass to date. The globular cluster (GC) candidate selection is based on the ({u}* -{i}\\prime ) versus ({i}\\prime -{K}s) diagram, which is a superb tool to distinguish GCs from foreground stars, background galaxies, and young stellar clusters, and hence can provide the best number counts of GCs from photometry alone, virtually free of contamination, even if the galaxy is not completely edge-on. The mean optical and optical-near-infrared colors of the clusters are consistent with those of the Milky Way and M 31, after extinction is taken into account. We directly identify 39 GC candidates; after completeness correction, GC luminosity function extrapolation, and correction for spatial coverage, we calculate a total {N}{GC}=144+/- {31}-36+38 (random and systematic uncertainties, respectively). We have thus increased to six the sample of spiral galaxies with measurements of both M • and {N}{GC}. NGC 4258 has a specific frequency {S}{{N}}=0.4+/- 0.1 (random uncertainty), and is consistent within 2σ with the {N}{GC} versus M • correlation followed by elliptical galaxies. The Milky Way continues to be the only spiral that deviates significantly from the relation.

  11. A Multivariate Statistical Analysis of Spiral Galaxy Luminosities. I. Data and Results

    NASA Astrophysics Data System (ADS)

    Shapley, Alice; Fabbiano, G.; Eskridge, P. B.

    2001-11-01

    We have performed a multiparametric analysis of luminosity data for a sample of 234 normal spiral and irregular galaxies observed in X-rays with the Einstein Observatory. This sample is representative of S and Irr galaxies, with a good coverage of morphological types and absolute magnitudes. In addition to X-ray and optical data, we have compiled H-band magnitudes, IRAS near- and far-infrared, and 6 cm radio continuum observations for the sample from the literature. We have also performed a careful compilation of distance estimates. We have explored the effect of morphology by dividing the sample into early- (S0/a-Sab), intermediate- (Sb-Sbc), and late-type (Sc-Irr) subsamples. The data were analyzed with bivariate and multivariate survival analysis techniques that make full use of all the information available in both detections and limits. We find that most pairs of luminosities are correlated when considered individually, and this is not due to a distance bias. Different luminosity-luminosity correlations follow different power-law relations. Contrary to previous reports, the LX-LB correlation follows a power law with exponent larger than 1. Both the significances of some correlations and their power-law relations are morphology dependent. Our analysis confirms the ``representative'' nature of our sample, by returning well-known results derived from previous analyses of independent samples of galaxies (e.g., the LB-LH, L12-LFIR, and LFIR-L6 cm correlations). Our multivariate analysis suggests that there are two fundamentally strong correlations, regardless of galaxy morphology, when all the wave bands are analyzed together with conditional probability methods. These are the LB-LH and the L12-LFIR correlations. As it is well known, the former links stellar emission processes and points to a basic connection between the initial mass function of low-mass and intermediate- to high-mass stars. The latter may be related to the heating of small and larger size dust

  12. The Structure & Stellar Populations of Nuclear Star Clusters in Late-Type Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Carson, Daniel James

    Luminous, compact stellar systems known as nuclear clusters (NCs) are commonly found in the centers of galaxies across the entire Hubble sequence. I present an analysis of the structure and stellar populations of a sample of ten of the nearest and brightest NCs residing in late-type spiral galaxies, using images from Hubble Space Telescope Wide Field Camera 3 in seven bands that span the near-ultraviolet to the near-infrared in wavelength. The intrinsic shapes and sizes of the NCs, disentangled from the effects of point spread function (PSF) blurring, were measured using GALFIT. We find evidence for radial color gradients within the NCs, as well as young disk structures aligned with the host galaxy disk. In color-color diagrams spanning the near-UV through the near-IR, NCs tend to lie far from single-burst evolutionary tracks, indicating the presence of multi-age populations. I developed a Monte Carlo code to fit linear combinations of simple stellar population models to the observed spectral energy distribution (SED) of each NC and assess the uncertainties in the fit parameters. Tests on a catalog of mock SEDs demonstrate that our method gives unbiased mass age, and reddening estimates for populations with U - V colors redder than ˜ -2 mag. Stellar masses computed via SED fitting are in good agreement with previous dynamical studies. The NCs are generally dominated by an old (> 1 Gyr) population component, but are best described by temporally extended star formation histories. On average, populations with ages < 100 Myr contribute 1.8% of the total stellar mass and 10.4% of the total B-band luminosity. From spatially resolved stellar population modeling, we compute maps of stellar density and age, which reveal radial age gradients. Multi-Gaussian Expansion models of NC stellar surface density, which will be used in future dynamical studies, are presented. We report an effective surface density of 6.7 x 105 solar masses per square parsec in IC 342, the densest

  13. 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

  14. Accretion states of the transient ULX in M83

    NASA Astrophysics Data System (ADS)

    Kuntz, Kip

    2012-10-01

    In Dec 2010, Chandra revealed a previously unknown ULX in M83 where there had been no detectable X-ray source before. It has varied in flux and hardness but has remained bright for nearly two years. Our analysis shows that it is a black hole (BH) accreting from a low-mass secondary. The spectral evolution of a transient ULX as it fades is a critical test of the nature of these intriguing objects. Our goal is to determine whether it goes through the same canonical accretion states defined for Galactic BHs. We propose two 50-ks observations, separated by a few months, to identify the accretion state(s), accurately determine the physical parameters, and compare with stellar-mass BH states. This will constrain the mass of this ULX and help clarify the relation between ULXs and stellar-mass BHs.

  15. KINEMATICS AND MODELING OF THE INNER REGION OF M 83

    SciTech Connect

    Rodrigues, Irapuan; Dottori, Horacio; Diaz, Ruben J.; Agueero, Maria P.; Mast, Damian E-mail: dottori@if.ufrgs.br

    2009-05-15

    Two-dimensional kinematics of the central region of M 83 (NGC 5236) were obtained through three-dimensional NIR spectroscopy with the Gemini South telescope. The spatial region covered by the integral field unit ({approx}5'' x 13'' or {approx}90 x 240 pc) was centered approximately at the center of the bulge isophotes and oriented southeast-northwest. The Pa{beta} emission at half-arcsecond resolution clearly reveals spider-like diagrams around three centers, indicating the presence of extended masses, which we describe in terms of Satoh distributions. One of the mass concentrations is identified as the optical nucleus (ON), another as the center of the bulge isophotes, similar to the CO kinematical center (KC), and the third as a condensation hidden at optical wavelengths (hidden nucleus, HN), coincident with the largest lobe in 10 {mu}m emission. We run numerical simulations that take into account ON, KC, and HN and four more clusters, representing the star-forming arc at the southwest of the optical nucleus. We show that ON, KC, and HN suffer strong evaporation and merge in 10-50 Myr. The star-forming arc is scattered in less than one orbital period, also falling into the center. Simulations also show that tidal striping boosts the external shell of the condensations to their escape velocity. This fact might lead to an overestimation of the mass of the condensations in kinematical observations with spatial resolution smaller than the condensations' apparent sizes. Additionally, the existence of two ILR resonances embracing the chain of H II regions, claimed by different authors, might not exist due to the similarity of the masses of the different components and the fast dynamical evolution of M 83 central 300 pc.

  16. Ultraviolet Spectroscopy of Circumnuclear Star Clusters in M83

    NASA Astrophysics Data System (ADS)

    Wofford, Aida; Leitherer, Claus; Chandar, Rupali

    2011-02-01

    We analyze archival HST/STIS/FUV-MAMA imaging and spectroscopy of 13 compact star clusters within the circumnuclear starburst region of M83, the closest such example. We compare the observed spectra with semi-empirical models, which are based on an empirical library of Galactic O and B stars observed with IUE, and with theoretical models, which are based on a new theoretical UV library of hot massive stars computed with WM-Basic. The models were generated with Starburst99 for metallicities of Z = 0.020 and Z = 0.040, and for stellar initial mass functions (IMFs) with upper mass limits of 10, 30, 50, and 100 M sun. We estimate the ages and masses of the clusters from the best-fit model spectra and find that the ages derived from the semi-empirical and theoretical models agree within a factor of 1.2 on average. A comparison of the spectroscopic age estimates with values derived from HST/WFC3/UVIS multi-band photometry shows a similar level of agreement for all but one cluster. The clusters have a range of ages from about 3 to 20 Myr and do not appear to have an age gradient along M83's starburst. Clusters with strong P-Cygni profiles have masses of a few×104 M sun, seem to have formed stars more massive than 30 M sun, and are consistent with a Kroupa IMF from 0.1to100 M sun. Field regions in the starburst lack P-Cygni profiles and are dominated by B stars.

  17. A Large-Scale Jet and FR I Radio Source in a Spiral Galaxy: The Host Properties and External Environment

    NASA Astrophysics Data System (ADS)

    Ledlow, Michael J.; Owen, Frazer N.; Yun, Min S.; Hill, John M.

    2001-05-01

    We have identified a large (~200 h-175 kpc), powerful double radio source whose host galaxy is clearly a disk and most likely a spiral. This FR I-like radio galaxy is located very near the center of the richness class 0 cluster A428. The existence of such an object violates a fundamental paradigm for radio-loud active galactic nuclei (AGNs). In our first paper, we showed that this object was most consistent with a spiral host classification with optical emission-line ratios and colors suggestive of an active nucleus. However, we were not able to confirm actual radio jet emission based on the maps available at that time. In this paper, we present new, higher resolution radio imaging, a radio/millimeter continuum spectrum for the nucleus, a detection of H I absorption against the bright radio core, an upper limit to CO emission and the gas mass, and 70 (68 new) optical redshifts measured in the direction of A428. We confirm the existence of a radio jet at 20 cm, extending 42 h-175 into the southern lobe. At 3.6 cm, we also detect a nuclear jet similar in length to that in M87, although 10 times weaker. We believe that this is the first detection of a radio jet on these scales in a disk/spiral host galaxy. The nuclear radio spectrum is similar to many blazar- or quasar-like objects, suggesting that the galaxy harbors an imbedded and obscured AGN. We model a turnover in the spectrum at low frequencies as a result of free-free absorption. We detect very strong and narrow H I absorption, with nearly the entire 20 cm continuum flux of the core being absorbed, implying an unusually large optical depth (τ~1). The most consistent model is that we are viewing the nucleus through a disklike distribution of gas in the interstellar medium, possibly through a spiral arm or a warp to account for the above-average column density. From the radial velocity distribution, we find that A428 is in fact made up of at least two clumps of galaxies separated by ~3300 km s-1, which

  18. Multi-Wavelength Observations of the Supernova Remnant Populations in the Nearby Spiral Galaxies IC 342 and NGC 4258

    NASA Astrophysics Data System (ADS)

    Pannuti, Thomas; Chomiuk, L.; Grimes, C. K.; Staggs, W. D.; Tussey, J. M.; Laine, S.; Schlegel, E.

    2011-01-01

    Supernova remnants (SNRs) are intimately tied to many crucial processes associated with the interstellar medium of galaxies, such as the acceleration of cosmic-ray particles and the deposition of vast amounts of kinetic energy and chemically-enriched material. Well-known observational challenges in the study of SNRs located in the Milky Way Galaxy (for example, formidable extinction along Galactic lines of sight and considerable uncertainties in the distances to these sources) have motivated searches for SNRs in nearby galaxies at such characteristic wavelengths as X-ray, optical and radio. These searches have revealed a considerable number of SNRs and led to new insights into their properties, but the SNR populations in only a handful of nearby galaxies have been adequately surveyed at multiple wavelengths. To help remedy this situation, we are conducting a multi-wavelength study of the SNR population of selected nearby galaxies. To illustrate our work, we present the results of studies of the SNR population in two nearby spiral galaxies, IC 342 and NGC 4258. Our results draw upon the analysis of pointed archival radio and X-ray observations of these two galaxies. Initial results will be presented and discussed.

  19. Joint Impact Proposal: A complete velocity resolved 3-D [CII] map of the M51 grand-design spiral galaxy: Unraveling the impact of spiral density waves on the evolution of the ISM and star formation.

    NASA Astrophysics Data System (ADS)

    Stutzki, Juergen

    2015-10-01

    We propose to obtain the first complete, velocity resolved [CII] 158um image of the M51 grand-design spiral galaxy with the upGREAT and FIFI-LS instruments on SOFIA. Spiral density waves play a fundamental role on the conversion of atomic to molecular gas, leading to gravitational contraction and thus to star formation. Understanding the impact of spiral density waves on the lifecycle of the interstellar medium and on star formation in galaxies is thus critical for our understanding of galaxy evolution. The [CII] line (in combination with the low-J CO lines and HI 21 cm) is an important tool to diagnose the physical state of the ISM. It can reveal the distribution of the gas that is making a transition between atomic and molecular phases, including the CO-dark H2 gas (hydrogen molecular but carbon ionized, and thus not traced by either HI or CO) in the spiral arms and interarm regions of M51. We will use the high spectral resolution of the upGREAT instrument to resolve spiral arms in velocity, allowing us to study the flow of gas through spiral arms and measure line widths and determine the dynamical state of prominent interarm clouds. The significantly more sensitive FIFI-LS will be used to detect extended faint [CII] emission in the interarm regions and outskirts of the galaxy, including the gas connection to the companion galaxy. The 3-D data cube of velocity-resolved [CII] in this nearby galaxy, combined with the wealth of ancillary data, can be used for a large set of investigations by the broader astronomical community. It will provide for the first time the link between the detailed physical processes in the star-forming ISM in the Milky Way and the average properties of distant external galaxies. This complete map will be also an excellent showcase of SOFIA's capabilities for years to come.

  20. Joint Impact Proposal: A complete velocity resolved 3-D [CII] map of the M51 grand-design spiral galaxy: Unraveling the impact of spiral density waves on the evolution of the ISM and star formation.

    NASA Astrophysics Data System (ADS)

    Pineda, Jorge

    2015-10-01

    We propose to obtain the first complete, velocity resolved [CII] 158um image of the M51 grand-design spiral galaxy with the upGREAT and FIFI-LS instruments on SOFIA. Spiral density waves play a fundamental role on the conversion of atomic to molecular gas, leading to gravitational contraction and thus to star formation. Understanding the impact of spiral density waves on the lifecycle of the interstellar medium and on star formation in galaxies is thus critical for our understanding of galaxy evolution. The [CII] line (in combination with the low-J CO lines and HI 21 cm) is an important tool to diagnose the physical state of the ISM. It can reveal the distribution of the gas that is making a transition between atomic and molecular phases, including the CO-dark H2 gas (hydrogen molecular but carbon ionized, and thus not traced by either HI or CO) in the spiral arms and interarm regions of M51. We will use the high spectral resolution of the upGREAT instrument to resolve spiral arms in velocity, allowing us to study the flow of gas through spiral arms and measure line widths and determine the dynamical state of prominent interarm clouds. The significantly more sensitive FIFI-LS will be used to detect extended faint [CII] emission in the interarm regions and outskirts of the galaxy, including the gas connection to the companion galaxy. The 3-D data cube of velocity--resolved [CII] in this nearby galaxy, combined with the wealth of ancillary data, can be used for a large set of investigations by the broader astronomical community. It will provide for the first time the link between the detailed physical processes in the star-forming ISM in the Milky Way and the average properties of distant external galaxies. This complete map will be also an excellent showcase of SOFIA's capabilities for years to come.

  1. Tidal Effects on the Oort Cloud Comets and Dynamics of the Sun in the Spiral Arms of the Galaxy

    NASA Astrophysics Data System (ADS)

    De Biasi, Alice

    2014-01-01

    The Solar System presents a complex dynamical structure and is not isolated from the Galaxy. In particular the comet reservoir of our planetary system, the Oort cloud, is extremely sensitive to the the galactic environment due to its peripheral collocation inside the Solar System. In this framework, the growing evidences about a possible migration of the Sun open new research scenarios relative to the effects that such kind of migration might induce on the cometary motion. Following several previous studied, we identified the spiral arm structure as the main perturbation that is able to produce an efficient solar migration through the disk. Widening the classical model for the spiral arms, provided by Lin& Shu to a 3D formalism, we verified the compatibility between the presence of the spiral perturbation and a significant solar motion for an inner Galactic position to the current one, in agreement with the constrains in position, velocity and metallicity due to the present conditions of our star. The main perturbers of the Oort cloud, the close stellar passages and the tidal field of the Galaxy, might be both affected by the variation of Galactic environment that the solar migration entails. Despite that, in order to isolate the effects to the two different perturbators, we decided to focus our attention only on the Galactic tide. The perturbation due to the spiral structure was included in the study on the cometary motion, introducing the solar migration and adding the direct presence of the non-axisymmetric component in the Galactic potential of the tidal field. The results show a significant influence of the spiral arm in particular on cometary objects belonged to the outer shell of the Oort cloud, for which provides an injection rate three times bigger than the integration performed without the spiral arms. The introduction of the spiral perturbation seems to bolster the planar component of the tide, indeed it produces the most significant variation of the

  2. The origin of the far-infrared luminosity within the spiral galaxy M101

    NASA Technical Reports Server (NTRS)

    Devereux, Nicholas A.; Scowen, Paul A.

    1994-01-01

    High resolution 60 and 100 micron images obtained with the Infared Astronomical Satellite (IRAS) are compared with H alpha images in order to investigate the origin of the far-infrared luminosity within the late-type spiral galaxy M101. There is a good correspondence between the far-infrared and H-alpha morphology. The far-infrared and H-alpha luminosities have been measured at 129 independent locations on the star forming disk of M101. After correcting the H-alpha luminosity for extinction and extrapolating the IRAS (40-120 microns) luminosity to 1000 microns we find that the far-infrared luminosity is commensurate with that expected from the O and B stars which are required to ionize the hydrogen gas, at all locations within M101. Additionally, the IRAS HiRes 60 and 100 micron images reveal that the dust temperature peaks coincide identically with the location of H II regions. The far-infrared luminosity of M101 is radiated primarily by dust with temperatures well in excess of that expected for cirrus, but similar to that observed for Galactic and extragalactic H II regions.

  3. X-ray-emitting gas surrounding the spiral galaxy NGC 891

    NASA Technical Reports Server (NTRS)

    Bregman, Joel N.; Pidis, Rachel A.

    1994-01-01

    We observed the edge-on spiral galaxy NGC 891 with the Position Sensitive Proportional Counter (PSPC) on Roentgen Satellite (ROSAT) to search for how extraplanar gas expected in the galactic fountain model. Diffuse X-ray emission surrounds the disk with a Half Width at Half Maximum (HWHM) for the surface brightness perpendicular to the disk of 50 sec (2.4 kpc) and a radial extent of approximately 6.5 kpc, both of which are similar in extent to the extended H(alpha) and radio halo component; the implied density scale height for the hot gas is 7 kpc. The spectrum is best fitted with a hard stellar component and a soft diffuse gas component of temperature 3.6 x 10(exp 6) K. The density of this gas is 2 x 10(exp -3)/cu cm, the luminosity is 4.4 x 10(exp 39) ergs/s, the mass is 1 x 10(exp 8) solar mass, and the pressure (P/k) is 1.4 10(exp 4) K/cu cm. These data are consistent with this gas participating in a galactic fountain, where the material approaches hydrostatic equilibrium before cooling at a rate of 0.12 solar mass/yr. The cooled material may be responsible for some of the H(alpha) emission.

  4. 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.

  5. 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.

  6. 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.

  7. The JCMT Nearby Galaxies Legacy Survey - XI. Environmental variations in the atomic and molecular gas radial profiles of nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Mok, Angus; Wilson, C. D.; Knapen, J. H.; Sánchez-Gallego, J. R.; Brinks, E.; Rosolowsky, E.

    2017-06-01

    We present an analysis of the radial profiles of a sample of 43 H i-flux selected spiral galaxies from the Nearby Galaxies Legacy Survey (NGLS) with resolved James Clerk Maxwell Telescope (JCMT) CO J = 3 - 2 and/or Very Large Array (VLA) H I maps. Comparing the Virgo and non-Virgo populations, we confirm that the H I discs are truncated in the Virgo sample, even for these relatively H i-rich galaxies. On the other hand, the H2 distribution is enhanced for the Virgo galaxies near their centres, resulting in higher H2 to H I ratios and steeper H2 and total gas radial profiles. This is likely due to the effects of moderate ram pressure stripping in the cluster environment, which would preferentially remove low-density gas in the outskirts while enhancing higher density gas near the centre. Combined with Hα star formation rate data, we find that the star formation efficiency (SFR/H2) is relatively constant with radius for both samples, but the Virgo galaxies have an ˜40 per cent lower star formation efficiency than the non-Virgo galaxies.

  8. Accurate Distances to Important Spiral Galaxies: M63, M74, NGC 1291, NGC 4559, NGC 4625, and NGC 5398

    NASA Astrophysics Data System (ADS)

    McQuinn, Kristen. B. W.; Skillman, Evan D.; Dolphin, Andrew E.; Berg, Danielle; Kennicutt, Robert

    2017-08-01

    Accurate distances are fundamental for interpreting various measured properties of galaxies. Surprisingly, many of the best-studied spiral galaxies in the Local Volume have distance uncertainties that are much larger than can be achieved with modern observation techniques. Using Hubble Space Telescopeoptical imaging, we use the tip of the red giant branch method to measure the distances to six galaxies that are included in the Spitzer Infrared Nearby Galaxies Survey program and its offspring surveys. The sample includes M63, M74, NGC 1291, NGC 4559, NGC 4625, and NGC 5398. We compare our results with distances reported to these galaxies based on a variety of methods. Depending on the technique, there can be a wide range in published distances, particularly from the Tully-Fisher relation. In addition, differences between the planetary nebular luminosity function and surface brightness fluctuation techniques can vary between galaxies, suggesting inaccuracies that cannot be explained by systematics in the calibrations. Our distances improve upon previous results, as we use a well-calibrated, stable distance indicator, precision photometry in an optimally selected field of view, and a Bayesian maximum likelihood technique that reduces measurement uncertainties. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  9. Dynamical mass estimates of young massive clusters in NGC1140 and M83

    NASA Astrophysics Data System (ADS)

    Moll, Sarah L.; de Grijs, Richard; Mengel, Sabine; Smith, Linda J.; Crowther, Paul A.

    2009-12-01

    We present virial mass estimates of young massive clusters (YMCs) in the starburst galaxies NGC1140 and M83, determined from high spectral resolution VLT echelle spectroscopy and high spatial resolution Hubble Space Telescope imaging. The survivability of such clusters is important in testing the scenario that YMCs are potentially proto-globular clusters. As young clusters, they lie in the domain in which dynamical masses appear to overestimate true cluster masses, most likely due to the clusters not being virialised. We find that the dynamical mass of NGC1140-1 is approximately ten times greater than its photometric mass. We propose that the most likely explanation for this disparity is the crowded environment of NGC1140-1, rather than this being solely due to a lack of virial equilibrium.

  10. 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

  11. 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

  12. A catalog of planetary nebula candidates in the Sculptor spiral galaxy NGC 300

    NASA Astrophysics Data System (ADS)

    Peña, M.; Reyes-Pérez, J.; Hernández-Martínez, L.; Pérez-Guillén, M.

    2012-11-01

    Aims: [O iii] 5007 Å on-band and off-band images, obtained with the Very Large Telescope (VLT) and FORS 2 spectrograph in two zones (center and outskirts) of the spiral galaxy NGC 300, are analyzed searching for emission line objects. In particular we search for planetary nebula (PN) candidates to analyze their distribution and luminosity properties, to perform follow-up spectroscopy, and to study the planetary nebula luminosity function, PNLF. Methods: In the continuum-subtracted images, a large number of emission line objects were detected. From this sample we selected those objects with stellar appearance and no detectable central star as PN candidates. [O iii] 5007 Å instrumental magnitudes were measured and calibrated by using spectrophotometric data from the follow-up spectroscopy. Results: We have identified more than a hundred PN candidates and many compact HII regions. The PN sample is the largest one reported for this galaxy so far. For all the objects we present coordinates, instrumental [O iii] 5007 magnitudes, and apparent nebular [O iii] 5007 fluxes and magnitudes. The [O iii] 5007 observed luminosity function for PNe (PNLF) was calculated for the whole sample and for the central and outskirts samples. The three PNLF are similar within uncertainties. We fit the empirical PNLF to the observed PNLF for all the samples. From our best fit for the whole sample, we derived a maximum value for the apparent magnitudes of m✩5007 = 22.019 ± 0.022 and obtained a tentative estimate of the distance modulus m5007-M5007= 26.29+0.12-0.22 mag, which agrees well with the recent value derived from Cepheid stars. Based on observations collected at the European Southern Observatory, VLT, Paranal, Chile, program ID 077.B-0430.Table 2 is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/547/A78

  13. The fundamental manifold of spiral galaxies: ordered versus random motions and the morphology dependence of the Tully-Fisher relation

    NASA Astrophysics Data System (ADS)

    Tonini, C.; Jones, D. H.; Mould, J.; Webster, R. L.; Danilovich, T.; Ozbilgen, S.

    2014-03-01

    We investigate the morphology dependence of the Tully-Fisher (TF) relation, and the expansion of the relation into a three-dimensional manifold defined by luminosity, total circular velocity and a third dynamical parameter, to fully characterize spiral galaxies across all morphological types. We use a full semi-analytic hierarchical model (based on Croton et al.), built on cosmological simulations of structure formation, to model galaxy evolution and build the theoretical TF relation. With this tool, we analyse a unique data set of galaxies for which we cross-match luminosity with total circular velocity and central velocity dispersion. We provide a theoretical framework to calculate such measurable quantities from hierarchical semi-analytic models. We establish the morphology dependence of the TF relation in both model and data. We analyse the dynamical properties of the model galaxies and determine that the parameter σ/VC, i.e. the ratio between random and total motions defined by velocity dispersion and circular velocity, accurately characterizes the varying slope of the TF relation for different model galaxy types. We apply these dynamical cuts to the observed galaxies and find indeed that such selection produces a differential slope of the TF relation. The TF slope in different ranges of σ/VC is consistent with that for the traditional photometric classification in Sa, Sb and Sc. We conclude that σ/VC is a good parameter to classify galaxy type, and we argue that such classification based on dynamics more closely mirrors the physical properties of the observed galaxies, compared to visual (photometric) classification. We also argue that dynamical classification is useful for samples where eye inspection is not reliable or impractical. We conclude that σ/VC is a suitable parameter to characterize the hierarchical assembly history that determines the disc-to-bulge ratio, and to expand the TF relation into a three-dimensional manifold, defined by luminosity

  14. Stellar Tidal Streams in Spiral Galaxies of the Local Volume: A Pilot Survey with Modest Aperture Telescopes

    NASA Astrophysics Data System (ADS)

    Martínez-Delgado, David; Gabany, R. Jay; Crawford, Ken; Zibetti, Stefano; Majewski, Steven R.; Rix, Hans-Walter; Fliri, Jürgen; Carballo-Bello, Julio A.; Bardalez-Gagliuffi, Daniella C.; Peñarrubia, Jorge; Chonis, Taylor S.; Madore, Barry; Trujillo, Ignacio; Schirmer, Mischa; McDavid, David A.

    2010-10-01

    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 (μlim(V) ~ 28.5 mag arcsec-2). This initial observational effort has led to the discovery of six previously undetected extensive (to ~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 ΛCold 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 that these theoretical models also

  15. 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.

  16. 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.

  17. A Census of Nuclear Star Clusters in Late-Type Spiral Galaxies: II. Spectroscopy and Stellar Populations

    NASA Astrophysics Data System (ADS)

    Boeker, Torsten

    2001-07-01

    Recent HST observations have revealed that many spiral galaxies have a prominent star cluster in their dynamical center, but statistics for cluster frequency, size, and luminosity remain incomplete. To fill this gap, we are undertaking a Cycle 9 WFPC2 snapshot survey of a well-defined sample of late-type galaxies. However, imaging data alone cannot yield the age distribution of the clusters, which is needed to clarify whether nuclear cluster formation is a one-time event or a recurrent process. This question is important because a central mass concentration is required for some models of bulge formation. In the few cases where cluster ages could be measured from ground-based spectra, they have been found to be rather young { < 10^7.5 yrs} and metal-rich. The question then is whether nuclear clusters indeed form recurrently, or whether ground-based observations are biased towards the brightest and hence youngest clusters. To address this issue, we will follow up our Cycle 9 imaging program with a snapshot program of low-resolution STIS spectroscopy of the detected clusters. HST's spatial resolution is required to separate the cluster light from the underlying galaxy emission. We will use stellar population synthesis models to infer the age distribution of the clusters, and to constrain their star formation history. The combined Cycle 9 and 10 programs will provide the first systematic census of nuclear star clusters in any class of spirals.

  18. Etude des Abondances de MG et de fe dans la Composante Stellaire des Disques des Galaxies Spirales

    NASA Astrophysics Data System (ADS)

    Beauchamp, Dominique

    Je presente ici une technique d'observation par imagerie des disques stellaires des galaxies spirales. Je tente, a l'aide d'un modele evolutif multiphase, de determiner les abondances de fer et de magnesium dans les disques. Dans ce but, je mesure les indices Mg2 et Fe5270 du systeme de Lick. Ces elements representent un choix judicieux d'indicateurs car ils sont formes par des supernovae de deux types differents ayant des durees de vie differentes. Le rapport d'abondances de ces deux elements est un indicateur du taux de formation des populations stellaires. Je decris, en premier lieu, les observations, la technique de mesure, ainsi que son application. J'analyse ensuite les indices mesures. A partir du modele multiphase, j'explore differents parametres physiques des spirales comme le taux de formation stellaire, l'evolution des abondances, les effets possibles de la presence de la barre, etc.

  19. HUBBLE SPACE TELESCOPE Imaging of Globular Clusters in the Edge-on Spiral Galaxies NGC 4565 and NGC 5907

    NASA Astrophysics Data System (ADS)

    Kissler-Patig, Markus; Ashman, Keith M.; Zepf, Stephen E.; Freeman, Kenneth C.

    1999-07-01

    We present a study of the globular cluster systems of two edge-on spiral galaxies, NGC 4565 and NGC 5907, from WFPC2 images in the F450W and F814W filters. The globular cluster systems of both galaxies appear to be similar to the Galactic globular cluster system. In particular, we derive total numbers of globular clusters of N_GC(4565)=204+/-38^+87_-53 and N_GC(5907)=170+/-41^+47_-72 (where the first are statistical, the second potential systematic errors) for NGC 4565 and NGC 5907, respectively. This determination is based on a comparison with the Milky Way system, for which we adopt a total number of globular clusters of 180+/-20. The specific frequency of both galaxies is S_N~=0.6, indistinguishable from the value for the Milky Way. The similarity in the globular cluster systems of the two galaxies is noteworthy, since they have significantly different thick disks and bulge-to-disk ratios. This would suggest that these two components do not play a major role in the building up of a globular cluster system around late-type galaxies.

  20. Time Variability and Luminosity of X-ray Sources of Face-on Spiral Galaxy NGC 1232

    NASA Astrophysics Data System (ADS)

    Cantua, Oscar; Rucas, Tyler; Singh, Pranjal; Schlegel, Eric M.

    2017-01-01

    The ACIS detector (Advanced CCD Imaging Spectrometer) onboard the Chandra X-ray Observatory has imaged the face-on spiral NGC 1232 over six epochs for a total exposure of ~250 ksec. We describe each observation as well as the merged data set. Each exposure contains ~50 individual sources. We focus on the time variability and luminosity distributions of the sources. We also describe our search for diffuse emission as well as our search for evidence for a reported collision with a dwarf galaxy. Finally, we compare the merged data set and the detected sources with other wavebands.

  1. Spatially resolved physical conditions of molecular gas and potential star formation tracers in M 83, revealed by the Herschel SPIRE FTS

    NASA Astrophysics Data System (ADS)

    Wu, R.; Madden, S. C.; Galliano, F.; Wilson, C. D.; Kamenetzky, J.; Lee, M.-Y.; Schirm, M.; Hony, S.; Lebouteiller, V.; Spinoglio, L.; Cormier, D.; Glenn, J.; Maloney, P. R.; Pereira-Santaella, M.; Rémy-Ruyer, A.; Baes, M.; Boselli, A.; Bournaud, F.; De Looze, I.; Hughes, T. M.; Panuzzo, P.; Rangwala, N.

    2015-03-01

    We investigate the physical properties of the molecular and ionized gas, and their relationship to the star formation and dust properties in M 83, based on submillimeter imaging spectroscopy from within the central 3.5' (~4 kpc in diameter) around the starburst nucleus. The observations use the Fourier Transform Spectrometer (FTS) of the Spectral and Photometric Imaging REceiver (SPIRE) onboard the Herschel Space Observatory. The newly observed spectral lines include [CI] 370 μm, [CI] 609 μm, [NII] 205 μm, and CO transitions from J = 4-3 to J = 13-12. Combined with previously observed J = 1-0 to J = 3-2 transitions, the CO spectral line energy distributions are translated to spatially resolved physical parameters, column density of CO, N(CO), and molecular gas thermal pressure, Pth, with a non-local thermal equilibrium (non-LTE) radiative transfer model, RADEX. Our results show that there is a relationship between the spatially resolved intensities of [NII] 205 μm and the surface density of the star formation rate (SFR), ΣSFR. This relation, when compared to integrated properties of ultra-luminous infrared galaxies (ULIRGs), exhibits a different slope, because the [NII] 205 μm distribution is more extended than the SFR. The spatially resolved [CI] 370 μm, on the other hand, shows a generally linear relationship with ΣSFR and can potentially be a good SFR tracer. Compared with the dust properties derived from broad-band images, we find a positive trend between the emissivity of CO in the J = 1-0 transition with the average intensity of interstellar radiation field (ISRF), ⟨ U ⟩. This trend implies a decrease in the CO-to-H2 conversion factor, XCO, when ⟨ U ⟩ increases. We estimate the gas-to-dust mass ratios to be 77 ± 33 within the central 2 kpc and 93 ± 19 within the central 4 kpc of M 83, which implies a Galactic dust-to-metal mass ratio within the observed region of M 83. The estimated gas-depletion time for the M 83 nucleus is 1.13 ± 0.6 Gyr

  2. 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.

  3. Simulating Galaxies: Investigating Spiral Pitch Angle and the Efficiency of Radial Mixing

    NASA Astrophysics Data System (ADS)

    Lifset, Noah; Barbano, Luke; Daniel, Kathryne J.

    2017-01-01

    Radial mixing refers to the permanent rearrangement of orbital angular momenta in a galactic disk due to interactions with transient spiral arms. A star is subject to this dynamical process when it is temporarily in a trapped orbit between the spiral arms near the corotation radius. The purpose of this research was to numerically investigate how spiral shape affects the efficiency of radial mixing. This was done by designing an orbital integrator that numerically simulated the motion of test particles in a 2D disk potential that had a steady spiral pattern and was populated using a Monte Carlo simulation. Several realizations of N=10^4 orbits were simulated and analyzed using the open source, distributed computing service Open Science Grid (OSG). The results were in agreement with previous theoretical predictions, and preliminary analysis of the data indicates that the RMS change in orbital angular momentum for stars in trapped orbits depends on spiral arm pitch angle.

  4. Predicting HCN, HCO+, multi-transition CO, and dust emission of star-forming galaxies. From local spiral and ultraluminous infrared galaxies to high-z star-forming and submillimeter galaxies

    NASA Astrophysics Data System (ADS)

    Vollmer, B.; Gratier, P.; Braine, J.; Bot, C.

    2017-06-01

    High-z star-forming galaxies have significantly higher gas fractions and star-formation efficiencies per molecular gas mass than local star-forming galaxies. In this work, we take a closer look at the gas content or fraction and the associated star-formation rate in main sequence and starburst galaxies at z = 0 and z 1-2 by applying an analytical model of galactic clumpy gas disks to samples of local spiral galaxies, ULIRGs, submillimeter (smm), and high-z star-forming galaxies. The model simultaneously calculates the total gas mass, Hi/H2 mass, the gas velocity dispersion, IR luminosity, IR spectral energy distribution, CO spectral line energy distribution (SLED), HCN(1-0) and HCO+(1-0) emission of a galaxy given its size, integrated star formation rate, stellar mass radial profile, rotation curve, and Toomre Q parameter. The model reproduces the observed CO luminosities and SLEDs of all sample galaxies within the model uncertainties ( 0.3 dex). Whereas the CO emission is robust against the variation of model parameters, the HCN and HCO+ emissions are sensitive to the chemistry of the interstellar medium. The CO and HCN mass-to-light conversion factors, including CO-dark H2, are given and compared to the values found in the literature. All model conversion factors have uncertainties of a factor of two. Both the HCN and HCO+ emissions trace the dense molecular gas to a factor of approximately two for the local spiral galaxies, ULIRGs and smm-galaxies. Approximately 80% of the molecular line emission of compact starburst galaxies originates in non-self-gravitating gas clouds. The effect of HCN infrared pumping is small but measurable (10-20%). The gas velocity dispersion varies significantly with the Toomre Q parameter. The Q = 1.5 model yields high-velocity dispersions (vdisp ≫ 10 km s-1) consistent with available observations of high-z star-forming galaxies and ULIRGs. However, we note that these high-velocity dispersions are not mandatory for starburst galaxies

  5. Spirality: A Noval Way to Measure Spiral Arm Pitch Angle

    NASA Astrophysics Data System (ADS)

    Shields, Douglas; Arkansas Galaxy Evolution Survey

    2017-01-01

    We present the MATLAB code Spirality, a novel method for measuring spiral arm pitch angles by fitting galaxy images to spiral templates of known pitch. Computation time is typically on the order of 2 minutes per galaxy, assuming 8 GB of working memory. We tested the code using 117 synthetic spiral images with known pitches, varying both the spiral properties and the input parameters. The code yielded correct results for all synthetic spirals with galaxy-like properties. We also compared the code’s results to two-dimensional Fast Fourier Transform (2DFFT) measurements for the sample of nearby galaxies defined by DMS PPak. Spirality’s error bars overlapped 2DFFT’s error bars for 26 of the 30 galaxies. The two methods’ agreement correlates strongly with galaxy radius in pixels and also with i-band magnitude, but not with redshift, a result that is consistent with at least some galaxies’ spiral structure being fully formed by z=1.2, beyond which there are few galaxies in our sample. We also analyze apparent spiral structure of three galaxies beyond z=2. The Spirality 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.

  6. 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.

  7. A Spectroscopic Study of the Rich Supernova Remnant Population in M83

    NASA Astrophysics Data System (ADS)

    Winkler, P. Frank; Blair, William P.; Long, Knox S.

    2017-04-01

    We report the results from a spectrophotometric study sampling the ≳ 300 candidate supernova remnants (SNRs) in M83 identified through optical imaging with Magellan/IMACS and Hubble Space Telescope/WFC3. Of the 118 candidates identified based on a high [S ii] λλ 6716, 6731 to Hα emission ratio, 117 show spectroscopic signatures of shock-heated gas, confirming them as SNRs—the largest uniform set of SNR spectra for any galaxy. Spectra of 22 objects with a high [O iii] λ5007 to Hα emission ratio, selected in an attempt to identify young ejecta-dominated SNRs like Cas A, reveal only one (previously reported) object with the broad (≳ 1000 {km} {{{s}}}-1) emission lines characteristic of ejecta-dominated SNRs, beyond the known SN1957D remnant. The other 20 [O iii]-selected candidates include planetary nebulae, compact H ii regions, and one background QSO. Although our spectroscopic sample includes 22 SNRs smaller than 11 pc, none of the other objects show broad emission lines; instead their spectra stem from relatively slow (˜ 200 {km} {{{s}}}-1) radiative shocks propagating into the metal-rich interstellar medium of M83. With six SNe in the past century, one might expect more of M83's small-diameter SNRs to show evidence of ejecta; this appears not to be the case. We attribute their absence to several factors, including that SNRs expanding into a dense medium evolve quickly to the ISM-dominated phase, and that SNRs expanding into regions already evacuated by earlier SNe are probably very faint. 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 National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil).

  8. Observations and kinematic modeling of neutral hydrogen in spiral galaxies: Implications for disk-halo flows and accretion

    NASA Astrophysics Data System (ADS)

    Zschaechner, Laura Kristina

    Recent realizations concerning kinematic measurements of extra-planar layers in nearby galaxies may provide important clues to the origin of such layers and thereby the growth and evolution of galaxy disks. In particular, observations have shown a decrease in rotation speed with height (lags) in the extra-planar layers of multiple galaxies, leading to various models which attempt to understand this gradient in terms of disk-halo flows and accretion of primordial gas. In this thesis we present deep observations and detailed kinematic models of neutral hydrogen (HI) in five nearby, edge-on spiral galaxies (NGC 4244, NGC 4565, NGC 4302, NGC 3044 and NGC 4013) observed with the Very Large Array and the Westerbork Synthesis Radio Telescope. These models provide insight concerning both the morphology and kinematics of HI above and within the disk, especially in terms of their lags. Characterization of the magnitude and radial variation of lags aids in determining whether extra-planar HI originates in the plane of the disk (as described in galactic fountain-type models) or is accreted. In these galaxies we find substantial extra- planar Hi is not ubiquitous, while lags appear to be so. Furthermore, the lags we measure are steeper than those produced by purely ballistic effects, indicating that additional physical effects must be at work. In every (with the exception of NGC 4013) galaxy we model, a radial shallowing of the lag is observed, starting at approximately half of R25, and reaching its lowest magnitude near R25. Combining our sample with results from the literature, we see no clear connection between the presence of extra-planar Hi and star formation, nor do we see any connection between lag magnitude and star formation. Our findings provide constraints for theoretical scenarios which we will describe.

  9. Spectrum of Lin-Shu-type density waves in the Galaxy: a number of discrete spiral modes of collective oscillations?

    NASA Astrophysics Data System (ADS)

    Griv, Evgeny; Kharchenko, Nina V.; Piskunov, Anatoly E.; Hou, Li-Gang; Jiang, Ing-Guey

    2015-10-01

    Measurements of great importance of photometric/trigonometric distances and velocities have recently done for 2859 open clusters and 103 masers associated with young high-mass stars in the disc of our Galaxy by Kharchenko et al. and Reid et al. We use these new high-precision data to determine the spectrum of Lin-Shu-type density waves in the system. The kinematics of 472 clusters and 65 masers selected within 4 kpc from the Sun is analysed on the assumption that the Galaxy is subject to moderately unstable, tightly-wound, small-amplitude density waves. For a given number of spiral arms, several minima of a least-squares estimator S of measured and predicted line-of-sight velocities of both clusters and masers with respect to the pitch angle p and the phase of the wave at the Sun's location are apparent from our calculation as |p| increases from 1° to 20°. The appearance of the minima of S is explained in terms of a number of discrete spiral modes of collective oscillations developing in the solar vicinity as suggested analytically by Lau, Lin & Mark, Bertin & Mark, Lau & Bertin and others in the late 1970s.

  10. 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

    2016-11-01

    We performed a series of 29 gas dynamical 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 3 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 towards 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× 10^{10} M_{⊙}) the large amount of gas funnelled towards 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 towards 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.

  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.