Browsing by Author "Elmegreen, Bruce G."

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    DO BARS DRIVE SPIRAL DENSITY WAVES?
    (IOP Publishing, 2009-05) Buta, Ronald J.; Knapen, Johan H.; Elmegreen, Bruce G.; Salo, Heikki; Laurikainen, Eija; Elmegreen, Debra Meloy; Puerari, Ivanio; Block, David L.; University of Alabama Tuscaloosa; Instituto de Astrofisica de Canarias; International Business Machines (IBM); University of Oulu; Vassar College; Instituto Nacional de Astrofisica, Optica y Electronica; University of Witwatersrand
    We present deep near-infrared Ks-band Anglo-Australian Telescope Infrared Imager and Spectrograph observations of a selected sample of nearby barred spiral galaxies, including some with the strongest known bars. The sample covers a range of Hubble types from SB0(-) to SBc. The goal is to determine if the torque strengths of the spirals correlate with those of the bars, which might be expected if the bars actually drive the spirals as has been predicted by theoretical studies. This issue has implications for interpreting bar and spiral fractions at high redshift. Analysis of previous samples suggested that such a correlation exists in the near-infrared, where effects of extinction and star formation are less important. However, the earlier samples had only a few excessively strong bars. Our new sample largely confirms our previous studies, but still any correlation is relatively weak. We find two galaxies, NGC 7513 and UGC 10862, where there is only a weak spiral in the presence of a very strong bar. We suggest that some spirals probably are driven by their bars at the same pattern speed, but that this may be only when the bar is growing or if there is abundant gas and dissipation.
  • Thumbnail Image
    Item
    GRAND DESIGN AND FLOCCULENT SPIRALS IN THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S(4)G)
    (IOP Publishing, 2011-07-26) Elmegreen, Debra Meloy; Elmegreen, Bruce G.; Yau, Andrew; Athanassoula, E.; Bosma, Albert; Buta, Ronald J.; Helou, George; Ho, Luis C.; Gadotti, Dimitri A.; Knapen, Johan H.; Laurikainen, Eija; Madore, Barry F.; Masters, Karen L.; Meidt, Sharon E.; Menendez-Delmestre, Karin; Regan, Michael W.; Salo, Heikki; Sheth, Kartik; Zaritsky, Dennis; Aravena, Manuel; Skibba, Ramin; Hinz, Joannah L.; Laine, Jarkko; Gil de Paz, Armando; Munoz-Mateos, Juan-Carlos; Seibert, Mark; Mizusawa, Trisha; Kim, Taehyun; Erroz Ferrer, Santiago; Vassar College; International Business Machines (IBM); Centre National de la Recherche Scientifique (CNRS); UDICE-French Research Universities; Aix-Marseille Universite; University of Alabama Tuscaloosa; California Institute of Technology; Carnegie Institution for Science; Max Planck Society; European Southern Observatory; Instituto de Astrofisica de Canarias; Universidad de la Laguna; University of Oulu; University of Turku; University of Portsmouth; Space Telescope Science Institute; National Radio Astronomy Observatory (NRAO); University of Arizona; Complutense University of Madrid; Seoul National University (SNU)
    Spiral arm properties of 46 galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S(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.
  • Thumbnail Image
    Item
    THE THICK DISK IN THE GALAXY NGC 4244 FROM S(4)G IMAGING
    (IOP Publishing, 2011-02-07) Comeron, Sebastien; Knapen, Johan H.; Sheth, Kartik; Regan, Michael W.; Hinz, Joannah L.; Gil de Paz, Armando; Menendez-Delmestre, Karin; Munoz-Mateos, Juan-Carlos; Seibert, Mark; Kim, Taehyun; Athanassoula, E.; Bosma, Albert; Buta, Ronald J.; Elmegreen, Bruce G.; Ho, Luis C.; Holwerda, Benne W.; Laurikainen, Eija; Salo, Heikki; Schinnerer, Eva; Korea Astronomy & Space Science Institute (KASI); Instituto de Astrofisica de Canarias; Universidad de la Laguna; National Radio Astronomy Observatory (NRAO); California Institute of Technology; Space Telescope Science Institute; University of Arizona; Complutense University of Madrid; Carnegie Institution for Science; Seoul National University (SNU); Centre National de la Recherche Scientifique (CNRS); UDICE-French Research Universities; Aix-Marseille Universite; University of Alabama Tuscaloosa; International Business Machines (IBM); University of Cape Town; University of Oulu; University of Turku; Max Planck Society
    If thick disks are ubiquitous and a natural product of disk galaxy formation and/or evolution processes, all undisturbed galaxies that have evolved during a significant fraction of a Hubble time should have a thick disk. The late-type spiral galaxy NGC 4244 has been reported as the only nearby edge-on galaxy without a confirmed thick disk. Using data from the Spitzer Survey of Stellar Structure in Galaxies (S(4)G) we have identified signs of two disk components in this galaxy. The asymmetries between the light profiles on both sides of the mid-plane of NGC 4244 can be explained by a combination of the galaxy not being perfectly edge-on and a certain degree of opacity of the thin disk. We argue that the subtlety of the thick disk is a consequence of either a limited secular evolution in NGC 4244, a small fraction of stellar material in the fragments which built the galaxy, or a high amount of gaseous accretion after the formation of the galaxy.
  • Thumbnail Image
    Item
    THE UNUSUAL VERTICAL MASS DISTRIBUTION OF NGC 4013 SEEN THROUGH THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S(4)G)
    (IOP Publishing, 2011-08-17) Comeron, Sebastien; Elmegreen, Bruce G.; Knapen, Johan H.; Sheth, Kartik; Hinz, Joannah L.; Regan, Michael W.; Gil de Paz, Armando; Munoz-Mateos, Juan-Carlos; Menendez-Delmestre, Karin; Seibert, Mark; Kim, Taehyun; Mizusawa, Trisha; Laurikainen, Eija; Salo, Heikki; Laine, Jarkko; Athanassoula, E.; Bosma, Albert; Buta, Ronald J.; Gadotti, Dimitri A.; Ho, Luis C.; Holwerda, Benne; Schinnerer, Eva; Zaritsky, Dennis; Korea Astronomy & Space Science Institute (KASI); International Business Machines (IBM); Instituto de Astrofisica de Canarias; Universidad de la Laguna; National Radio Astronomy Observatory (NRAO); University of Arizona; Space Telescope Science Institute; Complutense University of Madrid; Carnegie Institution for Science; University of Oulu; University of Turku; Centre National de la Recherche Scientifique (CNRS); UDICE-French Research Universities; Aix-Marseille Universite; University of Alabama Tuscaloosa; European Southern Observatory; European Space Agency; Max Planck Society
    NGC 4013 is a nearby Sb edge-on galaxy known for its "prodigious" Hi warp and its "giant" tidal stream. Previous work on this unusual object shows that it cannot be fitted satisfactorily by a canonical thin+thick disk structure. We have produced a new decomposition of NGC 4013, considering three stellar flattened components (thin+thick disk plus an extra and more extended component) and one gaseous disk. All four components are considered to be gravitationally coupled and isothermal. To do so, we have used the 3.6 mu m images from the Spitzer Survey of Stellar Structure in Galaxies. We find evidence for NGC 4013 indeed having a thin and a thick disk and an extra flattened component. This smooth and extended component (scale height z(EC) similar to 3 kpc) could be interpreted as a thick disk or as a squashed ellipsoidal halo and contains similar to 20% of the total mass of all three stellar components. We argue it is unlikely to be related to the ongoing merger or due to the off-plane stars from a warp in the other two disk components. Instead, we favor a scenario in which the thick disk and the extended component were formed in a two-stage process, in which an initially thick disk has been dynamically heated by a merger soon enough in the galaxy history to have a new thick disk formed within it.
  • Thumbnail Image
    Item
    Variation of galactic bar length with amplitude and density as evidence for bar growth over a Hubble time
    (IOP Publishing, 2007-12-01) Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Knapen, Johan H.; Buta, Ronald J.; Block, David L.; Puerari, Ivanio; International Business Machines (IBM); Vassar College; Instituto de Astrofisica de Canarias; University of Alabama Tuscaloosa; University of Witwatersrand; Instituto Nacional de Astrofisica, Optica y Electronica
    K-s-band images of 20 barred galaxies show an increase in the peak amplitude of the normalized m = 2 Fourier component with the R-25-normalized radius at this peak. This implies that longer bars have higher m = 2 amplitudes. The long bars also correlate with an increased density in the central parts of the disks, as measured by the luminosity inside 0.25R(25) divided by the cube of this radius in kpc. Because denser galaxies evolve faster, these correlations suggest that bars grow in length and amplitude over a Hubble time, with the fastest evolution occurring in the densest galaxies. All but three of the sample have early-type flat bars; there is no clear correlation between the correlated quantities and the Hubble type.