Physical Sciences and Mathematics | Open Access Articles

X-Ray Nuclear Activity In S4g Barred Galaxies : No Link Between Bar Strength And Co-Occurrent Supermassive Black Hole Fueling., Mauricio Cisternas, Dimitri A. Gadotti, Johan H. Knapen, Taehyun Kim, Simon Diaz-Garcia, Eija Laurikainen, Heikki Salo, Omaira Gonzalez-Martin, Luis C. Ho, Bruce G. Elmegreen, Dennis Zaritsky, Kartik Sheth, E. Athanassoula, Albert Bosma, Sebastien Comeron, Santiago Erroz-Ferrer, Armando Gil De Paz, Joannah L. Hinz, Benne W. Holwerda, Jarkko Laine, Sharon Meidt, Karin Menendez-Delmestre, Trisha Mizusawa, Juan Carlos Munoz-Mateos, Michael W. Regan, Mark Seibert

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Stellar bars can lead to gas inflow toward the center of a galaxy and stimulate nuclear star formation. However, there is no compelling evidence on whether they also feed a central supermassive black hole: by measuring the fractions of barred active and inactive galaxies, previous studies have yielded conflicting results. In this paper, we aim to understand the lack of observational evidence for bar-driven active galactic nucleus (AGN) activity by studying a sample of 41 nearby (d < 35 Mpc) barred galaxies from the Spitzer Survey for Stellar Structure in Galaxies. We use Chandra observations to measure nuclear 2–10 keV X-ray luminosities and estimate Eddington ratios, together with Spitzer 3.6 μm imaging to quantify the strength of the stellar bar in two independent ways: (1) from its structure, as traced by its ellipticity and boxiness, and (2) from its gravitational torque Qb, taken as the maximum ratio of the tangential force to the mean background radial force. In this way, rather than discretizing the presence of both stellar bars and nuclear activity, we are able to account for the continuum of bar strengths and degrees of AGN activity. We find nuclear X-ray sources in 31 out of 41 galaxies with median X-ray luminosity and Eddington ratio of LX = 4.3×1038 erg s−1 and Lbol/LEdd = 6.9×10−6, respectively, consistent with low-luminosity AGN activity. Including upper limits for those galaxies without nuclear detections, we find no significant correlation between any of the bar strength indicators and the degree of nuclear activity, irrespective of galaxy luminosity, stellar mass, Hubble type, or bulge size. Strong bars do not favor brighter or more efficient nuclear activity, implying that at least for the low-luminosity regime, supermassive black hole fueling is not closely connected to large-scale features.

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Quantified H I Morphology – Vii. Star Formation And Tidal Influence On Local Dwarf H I Morphology., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, S. -L. Blyth

Faculty Scholarship

Scale-invariant morphology parameters applied to atomic hydrogen maps (H i) of galaxies can be used to quantify the effects of tidal interaction or star formation on the interstellar matter (ISM). Here we apply these parameters, concentration, asymmetry, smoothness, Gini, M20, and the GM parameter, to two public surveys of nearby dwarf galaxies, the Very Large Array-ANGST and Local Irregulars That Trace Luminosity Extremes-The H i Nearby Galaxy Survey, to explore whether tidal interaction or the ongoing or past star formation is a dominant force shaping the H i disc of these dwarfs. Previously, H i morphological criteria were identified for …

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The Occulting Galaxy Pair Ugc 3995 : Dust Properties From Hst And Califa Data., Benne W. Holwerda, W. C. Keel

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UGC 3995 is an interacting and occulting galaxy pair. UGC 3995B is a foreground face-on spiral and UGC 3995A a bright background spiral with an AGN. We present analysis of the dust in the disc of UGC 3995B based on archival Hubble Space Telescope (HST) WFPC2 and PPAK IFU data from the CALIFA survey’s first data release. From the HST F606W image, we construct an extinction map by modeling the isophotes of the background galaxy UGC 3995A and the resulting transmission through UGC 3995B. This extinction map of UGC 3995B shows several distinct spiral extinction features. The radial distribution of …

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Herschel Observations Of Edge-On Spirals (Heroes) I. Far-Infrared Morphology And Dust Mass Determination., J. Verstappen, J. Fritz, M. Baes, M. W. L. Smith, F. Allaert, S. Bianchi, J. A. D. L. Blommaert, G. De Geyter, I. De Looze, G. Gentile, K. D. Gordon, Benne W. Holwerda, S. Viaene, E. M. Xilouris

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Context. Edge-on spiral galaxies with prominent dust lanes provide us with an excellent opportunity to study the distribution and properties of the dust within them. The HEROES project was set up to observe a sample of seven large edge-on galaxies across various wavelengths for this investigation. Aims. Within this first paper, we present the Herschel observations and perform a qualitative and quantitative analysis on them, and we derive some global properties of the far infrared and submillimetre emission. Methods. We determine horizontal and vertical profiles from the Herschel observations of the galaxies in the sample and describe the morphology. Modified …

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On The Origin Of Lopsidedness In Galaxies As Determined From The Spitzer Survey Of Stellar Structure In Galaxies (S4g)., Dennis Zaritsky, Heikki Salo, Eija Laurikainen, Debra M. Elmegreen, E. Athanassoula, Albert Bosma, Sebastien Comeron, Santiago Erroz-Ferrer, Bruce G. Elmegreen, Dimitri A. Gadotti, Armando Gil De Paz, Joannah L. Hinz, Luis C. Ho, Benne W. Holwerda, Taehyun Kim, Johan H. Knapen, Jarkko Laine, Seppo Laine, Barry F. Madore, Sharon Meidt, Karin Menendez-Delmestre, Trisha Mizusawa, Juan Carlos Munoz-Mateos, Michael W. Regan, Mark Seibert, Kartik Sheth

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We study the m = 1 distortions (lopsidedness) in the stellar components of 167 nearby galaxies that span a wide range of morphologies and luminosities. We confirm the previous findings of (1) a high incidence of lopsidedness in the stellar distributions, (2) increasing lopsidedness as a function of radius out to at least 3.5 exponential scale lengths, and (3) greater lopsidedness, over these radii, for galaxies of later type and lower surface brightness. Additionally, the magnitude of the lopsidedness (1) correlates with the character of the spiral arms (stronger arm patterns occur in galaxies with less lopsidedness), (2) is not …

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The Impact Of Bars On Disk Breaks As Probed By S4g Imaging., Juan Carlos Munoz-Mateos, Kartik Sheth, Armando Gil De Paz, Sharon Meidt, E. Athanassoula, Albert Bosma, Sebastien Comeron, Debra M. Elmegreen, Bruce G. Elmegreen, Santiago Erroz-Ferrer, Dimitri A. Gadotti, Joannah L. Hinz, Luis C. Ho, Benne W. Holwerda, Thomas H. Jarrett, Taehyun Kim, Johan H. Knapen, Jarkko Laine, Eija Laurikainen, Barry F. Madore, Karin Menendez-Delmestre, Trisha Mizusawa, Michael Regan, Heikki Salo, Eva Schinnerer, Mark Seibert, Ramin Skibba, Dennis Zaritsky

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We have analyzed the radial distribution of old stars in a sample of 218 nearby face-on disks, using deep 3.6μm images from the Spitzer Survey of Stellar Structure in Galaxies. In particular, we have studied the structural properties of those disks with a broken or down-bending profile. We find that, on average, disks with a genuine single-exponential profile have a scale length and a central surface brightness which are intermediate to those of the inner and outer components of a down-bending disk with the same total stellar mass. In the particular case of barred galaxies, the ratio between the break …

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The Opacity Of Spiral Galaxy Disks : Ix. Dust And Gas Surface Densities., Benne W. Holwerda, R. J. Allen, W. J. G. De Blok, A. Bouchard, R. A. Gonzalez-Lopezlira, P. C. Van Der Kruit, A. Leroy

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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 …

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Quantified H I Morphology – Vii. Star Formation And Tidal Influence On Local Dwarf H I Morphology., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, S. -L. Blyth

Faculty Scholarship

The Occulting Galaxy Pair Ugc 3995 : Dust Properties From Hst And Califa Data., Benne W. Holwerda, W. C. Keel

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The Opacity Of Spiral Galaxy Disks : Ix. Dust And Gas Surface Densities., Benne W. Holwerda, R. J. Allen, W. J. G. De Blok, A. Bouchard, R. A. Gonzalez-Lopezlira, P. C. Van Der Kruit, A. Leroy

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