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Articles 151 - 180 of 211

Full-Text Articles in Astrophysics and Astronomy

Galaxy And Mass Assembly (Gama) : Galaxy Close Pairs, Mergers And The Future Fate Of Stellar Mass., A. S. G. Robotham, S. P. Driver, L. J. M. Davies, A. M. Hopkins, I. K. Baldry, N. K. Agius, A. E. Bauer, J. Bland-Hawthorn, S. Brough, M. J. I. Brown, M. Cluver, R. De Propis, M. J. Drinkwater, Benne W. Holwerda, L. S. Kelvin, M. A. Lara-Lopez, J. Liske, Angel R. Lopez-Sanchez, J. Loveday, S. Mahajan, T. Mcnaught-Roberts, A. Moffett, P. Norberg, D. Obreschkow, M. S. Owers, S. J. Penny, K. A. Pimbblet, M. Prescott, E. N. Taylor, E. Van Kampen, S. M. Wilkins Nov 2014

Galaxy And Mass Assembly (Gama) : Galaxy Close Pairs, Mergers And The Future Fate Of Stellar Mass., A. S. G. Robotham, S. P. Driver, L. J. M. Davies, A. M. Hopkins, I. K. Baldry, N. K. Agius, A. E. Bauer, J. Bland-Hawthorn, S. Brough, M. J. I. Brown, M. Cluver, R. De Propis, M. J. Drinkwater, Benne W. Holwerda, L. S. Kelvin, M. A. Lara-Lopez, J. Liske, Angel R. Lopez-Sanchez, J. Loveday, S. Mahajan, T. Mcnaught-Roberts, A. Moffett, P. Norberg, D. Obreschkow, M. S. Owers, S. J. Penny, K. A. Pimbblet, M. Prescott, E. N. Taylor, E. Van Kampen, S. M. Wilkins

Faculty and Staff Scholarship

We use a highly complete subset of the Galaxy And Mass Assembly II (GAMA-II) redshift sample to fully describe the stellar mass dependence of close pairs and mergers between 108 and 1012 M⊙. Using the analytic form of this fit we investigate the total stellar mass accreting on to more massive galaxies across all mass ratios. Depending on how conservatively we select our robust merging systems, the fraction of mass merging on to more massive companions is 2.0–5.6 per cent. Using the GAMA-II data we see no significant evidence for a change in the close pair fraction between redshift z …

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Evidence For The Concurrent Growth Of Thick Discs And Central Mass Concentrations From S4g Imaging., S. Comeron, B. G. Elmegreen, H. Salo, E. Laurikainen, Benne W. Holwerda, J. H. Knapen Nov 2014

Evidence For The Concurrent Growth Of Thick Discs And Central Mass Concentrations From S4g Imaging., S. Comeron, B. G. Elmegreen, H. Salo, E. Laurikainen, Benne W. Holwerda, J. H. Knapen

Faculty and Staff Scholarship

We have produced 3.6 μm + 4.5 μm vertically integrated radial luminosity profiles of 69 edge-on galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G). We decomposed the luminosity profiles into a disc and a central mass concentration (CMC). These fits, combined with thin/thick disc decompositions from our previous studies, allow us to estimate the masses of the CMCs, the thick discs, and the thin discs (ℳCMC, ℳT, and ℳT). We obtained atomic disc masses (ℳg) from the literature. We then consider the CMC and the thick disc to be dynamically hot components and the thin …

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Galaxy And Mass Assembly (Gama) : Stellar Mass Functions By Hubble Type., Lee S. Kelvin, Simon P. Driver, Aaron S. G. Robotham, Edward N. Taylor, Alister W. Graham, Mehmet Alpaslan, Ivan K. Baldry, Steven P. Bamford, Amanda E. Bauer, Joss Bland-Hawthorn, Michael J. I. Brown, Matthew Colless, Christopher J. Conselice, Benne W. Holwerda, Andrew M. Hopkins, Maritza A. Lara-Lopez, Jochen Liske, Angel R. Lopez-Sanchez, Jonathan Loveday, Peder Norberg, Steven Phillipps, Cristina C. Popescu, Matthew Prescott, Anne E. Sansom, Richard J. Tuffs Aug 2014

Galaxy And Mass Assembly (Gama) : Stellar Mass Functions By Hubble Type., Lee S. Kelvin, Simon P. Driver, Aaron S. G. Robotham, Edward N. Taylor, Alister W. Graham, Mehmet Alpaslan, Ivan K. Baldry, Steven P. Bamford, Amanda E. Bauer, Joss Bland-Hawthorn, Michael J. I. Brown, Matthew Colless, Christopher J. Conselice, Benne W. Holwerda, Andrew M. Hopkins, Maritza A. Lara-Lopez, Jochen Liske, Angel R. Lopez-Sanchez, Jonathan Loveday, Peder Norberg, Steven Phillipps, Cristina C. Popescu, Matthew Prescott, Anne E. Sansom, Richard J. Tuffs

Faculty and Staff Scholarship

We present an estimate of the galaxy stellar mass function and its division by morphological type in the local (0.025 < z < 0.06) Universe. Adopting robust morphological classifications as previously presented (Kelvin et al.) for a sample of 3727 galaxies taken from the Galaxy And Mass Assembly survey, we define a local volume and stellar mass limited sub-sample of 2711 galaxies to a lower stellar mass limit of M=109.0M⊙ M=109.0M⊙ . We confirm that the galaxy stellar mass function is well described by a double-Schechter function given by M∗=1010.64M⊙ M∗=1010.64M⊙ , α1 = −0.43, ϕ∗1=4.18dex−1Mpc−3 ϕ1∗=4.18dex−1Mpc−3 , α2 = −1.50 and ϕ∗2=0.74dex−1Mpc−3 ϕ2∗=0.74dex−1Mpc−3 . The constituent morphological-type stellar mass functions are well sampled above our lower stellar mass limit, excepting the faint little blue spheroid population of galaxies. We find approximately 71+3−4 71−4+3 per cent of the stellar mass in the local Universe is found within spheroid-dominated galaxies; ellipticals and S0-Sas. The remaining 29+4−3 29−3+4 per cent falls predominantly within late-type disc-dominated systems, Sab-Scds and Sd-Irrs. Adopting reasonable bulge-to-total ratios implies that approximately half the stellar mass today resides in spheroidal structures, and half in disc structures. Within this local sample, we find approximate stellar mass proportions for E : S0-Sa : Sab-Scd : Sd-Irr of 34 : 37 : 24 : 5.

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Galaxy And Mass Assembly (Gama) : Autoz Spectral Redshift Measurements, Confidence And Errors., I. K. Baldry, M. Alpaslan, A. E. Bauer, J. Bland-Hawthorn, S. Brough, M. E. Cluver, S. M. Croom, L. J. M. Davies, S. P. Driver, M. L. P. Gunawardhana, Benne W. Holwerda, A. M. Hopkins, L. S. Kelvin, J. Liske, A. R. Lopez-Sanchez, J. Loveday, P. Norberg, J. A. Peacock, A. S. G. Robotham, E. N. Taylor Jul 2014

Galaxy And Mass Assembly (Gama) : Autoz Spectral Redshift Measurements, Confidence And Errors., I. K. Baldry, M. Alpaslan, A. E. Bauer, J. Bland-Hawthorn, S. Brough, M. E. Cluver, S. M. Croom, L. J. M. Davies, S. P. Driver, M. L. P. Gunawardhana, Benne W. Holwerda, A. M. Hopkins, L. S. Kelvin, J. Liske, A. R. Lopez-Sanchez, J. Loveday, P. Norberg, J. A. Peacock, A. S. G. Robotham, E. N. Taylor

Faculty and Staff Scholarship

The Galaxy And Mass Assembly (GAMA) survey has obtained spectra of over 230 000 targets using the Anglo-Australian Telescope. To homogenize the redshift measurements and improve the reliability, a fully automatic redshift code was developed (autoz). The measurements were made using a cross-correlation method for both the absorption- and the emission-line spectra. Large deviations in the high-pass-filtered spectra are partially clipped in order to be robust against uncorrected artefacts and to reduce the weight given to single-line matches. A single figure of merit (FOM) was developed that puts all template matches on to a similar confidence scale. The redshift confidence …

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Milky Way Red Dwarfs In The Borg Survey : Galactic Scale-Height And The Distribution Of Dwarf Stars In Wfc3 Imaging., Benne W. Holwerda, M. Trenti, W. Clarkson, K. Sahu, L. Bradley, M. Stiavelli, N. Pirzkal, G. De Marchi, M. Andersen, R. J. Bouwens, R. Ryan Jun 2014

Milky Way Red Dwarfs In The Borg Survey : Galactic Scale-Height And The Distribution Of Dwarf Stars In Wfc3 Imaging., Benne W. Holwerda, M. Trenti, W. Clarkson, K. Sahu, L. Bradley, M. Stiavelli, N. Pirzkal, G. De Marchi, M. Andersen, R. J. Bouwens, R. Ryan

Faculty and Staff Scholarship

We present a tally of Milky Way late-type dwarf stars in 68 Wide Field Camera 3 (WFC3) pure-parallel fields (227 arcmin2) from the Brightest of Reionizing Galaxies survey for high-redshift galaxies. Using spectroscopically identified M-dwarfs in two public surveys, the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey and the Early Release Science mosaics, we identify a morphological selection criterion using the half-light radius (r50), a near-infrared J − H, G − J color region where M-dwarfs are found, and a V − J relation with M-dwarf subtype. We apply this morphological selection of stellar objects, color–color selection of M-dwarfs, and …

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Reconstructing The Stellar Mass Distributions Of Galaxies Using S4g Irac 3.6 And 4.5 Μm Images. Ii. The Conversion From Light To Mass., Sharon Meidt, Eva Schinnerer, Glenn Van De Ven, Dennis Zaritsky, Reynier Peletier, Johan H. Knapen, Kartik Sheth, Michael Regan, Miguel Querejeta, Juan Carlos Munoz-Mateos, Taehyun Kim, Joannah Hinz, Armando Gil De Paz, E. Athanassoula, Albert Bosma, Ronald J. Buta, Mauricio Cisternas, Luis C. Ho, Benne W. Holwerda, Ramin Skibba, E. Laurikainen, H. Salo, D. A. Gadotti, Jarkko Laine, Santiago Erroz-Ferrer, Sebastien Comeron, K. Menendez-Delmestre, M. Seibert, T. Mizusawa Jun 2014

Reconstructing The Stellar Mass Distributions Of Galaxies Using S4g Irac 3.6 And 4.5 Μm Images. Ii. The Conversion From Light To Mass., Sharon Meidt, Eva Schinnerer, Glenn Van De Ven, Dennis Zaritsky, Reynier Peletier, Johan H. Knapen, Kartik Sheth, Michael Regan, Miguel Querejeta, Juan Carlos Munoz-Mateos, Taehyun Kim, Joannah Hinz, Armando Gil De Paz, E. Athanassoula, Albert Bosma, Ronald J. Buta, Mauricio Cisternas, Luis C. Ho, Benne W. Holwerda, Ramin Skibba, E. Laurikainen, H. Salo, D. A. Gadotti, Jarkko Laine, Santiago Erroz-Ferrer, Sebastien Comeron, K. Menendez-Delmestre, M. Seibert, T. Mizusawa

Faculty and Staff Scholarship

We present a new approach for estimating the 3.6μm stellar mass-to-light (M/L) ratio ϒ3.6 in terms of the [3.6]–[4.5] colors of old stellar populations. Our approach avoids several of the largest sources of uncertainty in existing techniques using population synthesis models. By focusing on mid-IR wavelengths, we gain a virtually dust extinction-free tracer of the old stars, avoiding the need to adopt a dust model to correctly interpret optical or optical/near-IR colors normally leveraged to assign the mass-to-light ratio ϒ. By calibrating a new relation between near-IR and mid-IR colors of giant stars observed in GLIMPSE we also avoid the …

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The Baryonic Tully-Fisher Relationship For S4g Galaxies And The "Condensed" Baryon Fraction Of Galaxies., Dennis Zaritsky, Helene M. Courtois, Juan Carlos Munoz-Mateos, Jenny Sorce, S. Erroz-Ferrer, S. Comeron, D. A. Gadotti, A. Gil De Paz, J. L. Hinz, E. Laurikainen, T. Kim, J. Laine, K. Menendez-Delmestre, T. Mizusawa, M. W. Regan, H. Salo, M. Seibert, K. Sheth, E. Athanassoula, A. Bosma, M. Cisternas, Luis C. Ho, Benne W. Holwerda Jun 2014

The Baryonic Tully-Fisher Relationship For S4g Galaxies And The "Condensed" Baryon Fraction Of Galaxies., Dennis Zaritsky, Helene M. Courtois, Juan Carlos Munoz-Mateos, Jenny Sorce, S. Erroz-Ferrer, S. Comeron, D. A. Gadotti, A. Gil De Paz, J. L. Hinz, E. Laurikainen, T. Kim, J. Laine, K. Menendez-Delmestre, T. Mizusawa, M. W. Regan, H. Salo, M. Seibert, K. Sheth, E. Athanassoula, A. Bosma, M. Cisternas, Luis C. Ho, Benne W. Holwerda

Faculty and Staff Scholarship

We combine data from the Spitzer Survey for Stellar Structure in Galaxies, a recently calibrated empirical stellar mass estimator from Eskew et al., and an extensive database of H i spectral line profiles to examine the baryonic Tully–Fisher (BTF) relation. We find (1) that the BTF has lower scatter than the classic Tully–Fisher (TF) relation and is better described as a linear relationship, confirming similar previous results, (2) that the inclusion of a radial scale in the BTF decreases the scatter but only modestly, as seen previously for the TF relation, and (3) that the slope of the BTF, which …

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Infall As A Function Of Position And Molecular Tracer In Dense Cores., Jared Alan Keown May 2014

Infall As A Function Of Position And Molecular Tracer In Dense Cores., Jared Alan Keown

College of Arts & Sciences Senior Theses

The standard model of prestellar core collapse suggests that this process works from the inside and moves outwards, with the fastest motions at the center. The relative abundances of many molecules also vary within cores, with certain molecules found only in specific regions characterized by narrow ranges of temperature and density. These characteristics lead to the hypothesis that the observed infall speeds in starless cores depend on both the position of the observations and the molecular tracer chosen. By measuring line emission at multiple positions across a core using an array of tracer molecules, one can determine whether these theoretical …

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Dust Properties Of Z~2 Infrared-Luminous Lyman Break Galaxies., Jennifer Leigh Wojno May 2014

Dust Properties Of Z~2 Infrared-Luminous Lyman Break Galaxies., Jennifer Leigh Wojno

Electronic Theses and Dissertations

Lyman break galaxies (LBGs) are well-known indicators of star formation. By analyzing the dust of moderate redshift (z ~ 2) LBGs, we can further investigate the properties of these strongly star forming galaxies at an epoch when global star formation is expected to peak. Using data observed by the Herschel satellite, we derive far-infrared fluxes for our color-selected sample of LBGs in the GOODS-S field, including a subsample of infrared-luminous LBGs (ILLBGs). This is one of the first samples of UV dropouts/partial dropouts, which are also infrared-luminous, to be studied for their far-IR properties. Fitting modified Planck curves and model …

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The Luminosity Function At Z ~ 8 From 97 Y-Band Dropouts : Inferences About Reionization., Kasper B. Schmidt, Tommaso Treu, Michele Trenti, Larry D. Bradley, Brandon C. Kelly, Pascal A. Oesch, Benne W. Holwerda, J. Michael Shull, Massimo Stiavelli May 2014

The Luminosity Function At Z ~ 8 From 97 Y-Band Dropouts : Inferences About Reionization., Kasper B. Schmidt, Tommaso Treu, Michele Trenti, Larry D. Bradley, Brandon C. Kelly, Pascal A. Oesch, Benne W. Holwerda, J. Michael Shull, Massimo Stiavelli

Faculty and Staff Scholarship

We present the largest search to date for Y-band dropout galaxies (z ∼ 8 Lyman break galaxies, LBGs) based on 350 arcmin2 of Hubble Space Telescope observations in the V, Y, J, and H bands from the Brightest of Reionizing Galaxies (BoRG) survey. In addition to previously published data, the BoRG13 data set presented here includes approximately 50 arcmin2 of new data and deeper observations of two previous BoRG pointings, from which we present 9 new z ∼ 8 LBG candidates, bringing the total number of BoRG Y-band dropouts to 38 with 25.5 mJ 27.6 (AB system). We introduce a …

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Galaxy And Mass Assembly (Gama) : Fine Filaments Of Galaxies Detected Within Voids., Mehmet Alpaslan, Aaron S. G. Robotham, Danail Obreschkow, Samantha Penny, Simon Driver, Peder Norberg, Sarah Brough, Michael Brown, Michelle Cluver, Benne W. Holwerda, Andrew M. Hopkins, Eelco Van Kampen, Lee S. Kelvin, Maritza A. Lara-Lopez, Jochen Liske, Jon Loveday, Smriti Mahajan, Kevin Pimbblet Mar 2014

Galaxy And Mass Assembly (Gama) : Fine Filaments Of Galaxies Detected Within Voids., Mehmet Alpaslan, Aaron S. G. Robotham, Danail Obreschkow, Samantha Penny, Simon Driver, Peder Norberg, Sarah Brough, Michael Brown, Michelle Cluver, Benne W. Holwerda, Andrew M. Hopkins, Eelco Van Kampen, Lee S. Kelvin, Maritza A. Lara-Lopez, Jochen Liske, Jon Loveday, Smriti Mahajan, Kevin Pimbblet

Faculty and Staff Scholarship

Based on data from the Galaxy and Mass Assembly (GAMA) survey, we report on the discovery of structures that we refer to as ‘tendrils’ of galaxies: coherent, thin chains of galaxies that are rooted in filaments and terminate in neighbouring filaments or voids. On average, tendrils contain six galaxies and span 10 h−1 Mpc. We use the so-called line correlation function to prove that tendrils represent real structures rather than accidental alignments. We show that voids found in the Sloan Digital Sky Survey, 7th data release survey that overlap with GAMA regions contain a large number of galaxies, primarily belonging …

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Galaxy And Mass Assembly (Gama) : Mid-Infrared Properties And Empirical Relations From Wise., M. E. Cluver, T. H. Jarrett, A. M. Hopkins, S. P. Driver, J. Liske, M. L. P. Gunawardhana, E. N. Taylor, A. S. G. Robotham, M. Alpaslan, I. Baldry, M. J. I. Brown, J. A. Peacock, C. C. Popescu, R. J. Tuffs, A. E. Bauer, J. Bland-Hawthorn, M. Colless, Benne W. Holwerda, M. A. Lara-Lopez, K. Leschinski, A. R. Lopez-Sanchez, P. Norberg, M. S. Owers, L. Wang, S. M. Wilkins Feb 2014

Galaxy And Mass Assembly (Gama) : Mid-Infrared Properties And Empirical Relations From Wise., M. E. Cluver, T. H. Jarrett, A. M. Hopkins, S. P. Driver, J. Liske, M. L. P. Gunawardhana, E. N. Taylor, A. S. G. Robotham, M. Alpaslan, I. Baldry, M. J. I. Brown, J. A. Peacock, C. C. Popescu, R. J. Tuffs, A. E. Bauer, J. Bland-Hawthorn, M. Colless, Benne W. Holwerda, M. A. Lara-Lopez, K. Leschinski, A. R. Lopez-Sanchez, P. Norberg, M. S. Owers, L. Wang, S. M. Wilkins

Faculty and Staff Scholarship

The Galaxy And Mass Assembly (GAMA) survey furnishes a deep redshift catalog that, when combined with the Wide-field Infrared Survey Explorer (WISE), allows us to explore for the first time the mid-infrared properties of >110,000 galaxies over 120 deg2 to z 0.5. In this paper we detail the procedure for producing the matched GAMA-WISE catalog for the G12 and G15 fields, in particular characterizing and measuring resolved sources; the complete catalogs for all three GAMA equatorial fields will be made available through the GAMA public releases. The wealth of multiwavelength photometry and optical spectroscopy allows us to explore empirical relations …

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The Ultraviolet Attenuation Law In Backlit Spiral Galaxies., William C. Keel, Anna M. Manning, Benne W. Holwerda, Chris J. Lintott, Kevin Schawinski Feb 2014

The Ultraviolet Attenuation Law In Backlit Spiral Galaxies., William C. Keel, Anna M. Manning, Benne W. Holwerda, Chris J. Lintott, Kevin Schawinski

Faculty and Staff Scholarship

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 …

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Arrakis : Atlas Of Resonance Rings As Known In The S4g., S. Comeron, H. Salo, E. Laurikainen, J. H. Knapen, R. J. Buta, M. Herrera-Endoqui, J. Laine, Benne W. Holwerda, K. Sheth, M. W. Regan, J. L. Hinz, J. C. Munoz-Mateos, A. Gil De Paz, K. Menendez-Delmestre, M. Seibert, T. Mizusawa, T. Kim, S. Erroz-Ferrer, D. A. Gadotti, E. Athanassoula, A. Bosma, L. C. Ho Feb 2014

Arrakis : Atlas Of Resonance Rings As Known In The S4g., S. Comeron, H. Salo, E. Laurikainen, J. H. Knapen, R. J. Buta, M. Herrera-Endoqui, J. Laine, Benne W. Holwerda, K. Sheth, M. W. Regan, J. L. Hinz, J. C. Munoz-Mateos, A. Gil De Paz, K. Menendez-Delmestre, M. Seibert, T. Mizusawa, T. Kim, S. Erroz-Ferrer, D. A. Gadotti, E. Athanassoula, A. Bosma, L. C. Ho

Faculty and Staff Scholarship

Context. Resonance rings and pseudorings (here collectively called rings) are thought to be related to the gathering of material near dynamical resonances caused by non-axisymmetries in galaxy discs. This means that they are the result of secular evolution processes that redistribute material and angular momentum in discs. Studying them may give clues on the formation and growth of bars and other disc non-axisymmetries. Aims. Our aims are to produce a catalogue and an atlas of the rings detected in the Spitzer Survey of Stellar Structure in Galaxies (S4G) and to conduct a statistical study of the data in the catalogue. …

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Unveiling The Structure Of Barred Galaxies At 3.6 Μm With The Spitzer Survey Of Stellar Structure In Galaxies (S4g). I. Disk Breaks., Taehyun Kim, Dimitri A. Gadotti, Kartik Sheth, E. Athanassoula, Albert Bosma, Myung Gyoon Lee, Barry F. Madore, Bruce G. Elmegreen, Johan H. Knapen, Dennis Zaritsky, Luis C. Ho, Sebastien Comeron, Benne W. Holwerda, Joannah L. Hinz, Juan Carlos Munoz-Mateos, Mauricio Cisternas, Santiago Erroz-Ferrer, Ron Buta, Eija Laurikainen, Heikki Salo, Jarkko Laine, Karin Menendez-Delmestre, Michael W. Regan, Bonita De Swardt, Armando Gil De Paz, Mark Seibert, Trisha Mizusawa Feb 2014

Unveiling The Structure Of Barred Galaxies At 3.6 Μm With The Spitzer Survey Of Stellar Structure In Galaxies (S4g). I. Disk Breaks., Taehyun Kim, Dimitri A. Gadotti, Kartik Sheth, E. Athanassoula, Albert Bosma, Myung Gyoon Lee, Barry F. Madore, Bruce G. Elmegreen, Johan H. Knapen, Dennis Zaritsky, Luis C. Ho, Sebastien Comeron, Benne W. Holwerda, Joannah L. Hinz, Juan Carlos Munoz-Mateos, Mauricio Cisternas, Santiago Erroz-Ferrer, Ron Buta, Eija Laurikainen, Heikki Salo, Jarkko Laine, Karin Menendez-Delmestre, Michael W. Regan, Bonita De Swardt, Armando Gil De Paz, Mark Seibert, Trisha Mizusawa

Faculty and Staff Scholarship

We have performed two-dimensional multicomponent decomposition of 144 local barred spiral galaxies using 3.6 μm images from the Spitzer Survey of Stellar Structure in Galaxies. Our model fit includes up to four components (bulge, disk, bar, and a point source) and, most importantly, takes into account disk breaks. We find that ignoring the disk break and using a single disk scale length in the model fit for Type II (down-bending) disk galaxies can lead to differences of 40% in the disk scale length, 10% in bulge-to-total luminosity ratio (B/T), and 25% in bar-to-total luminosity ratios. We find that for galaxies …

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Embedded Star Formation In S4g Galaxy Dust Lanes., Debra M. Elmegreen, Bruce G. Elmegreen, Santiago Erroz-Ferrer, Johan H. Knapen, Yaron Teich, Mark Popinchalk, E. Athanassoula, Albert Bosma, Sebastien Comeron, Yuri N. Efremov, Dimitri A. Gadotti, Armando Gil De Paz, Joannah L. Hinz, Luis C. Ho, Benne W. Holwerda, Taehyun Kim, Jarkko Laine, Eija Laurikainen, Karin Menendez-Delmestre, Trisha Mizusawa, Juan Carlos Munoz-Mateos, Michael W. Regan, Heikki Salo, Mark Seibert, Kartik Sheth Jan 2014

Embedded Star Formation In S4g Galaxy Dust Lanes., Debra M. Elmegreen, Bruce G. Elmegreen, Santiago Erroz-Ferrer, Johan H. Knapen, Yaron Teich, Mark Popinchalk, E. Athanassoula, Albert Bosma, Sebastien Comeron, Yuri N. Efremov, Dimitri A. Gadotti, Armando Gil De Paz, Joannah L. Hinz, Luis C. Ho, Benne W. Holwerda, Taehyun Kim, Jarkko Laine, Eija Laurikainen, Karin Menendez-Delmestre, Trisha Mizusawa, Juan Carlos Munoz-Mateos, Michael W. Regan, Heikki Salo, Mark Seibert, Kartik Sheth

Faculty and Staff Scholarship

Star-forming regions that are visible at 3.6 μm and Hα but not in the u, g, r, i, z bands of the Sloan Digital Sky Survey are measured in five nearby spiral galaxies to find extinctions averaging ∼3.8 mag and stellar masses averaging ∼5 × 104 M. These regions are apparently young star complexes embedded in dark filamentary shock fronts connected with spiral arms. The associated cloud masses are ∼107 M. The conditions required to make such complexes are explored, including gravitational instabilities in spiral-shocked gas and compression of incident clouds. We find that instabilities are too slow for a …

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Ghosts I : A New Faint Very Isolated Dwarf Galaxy At D = 12 ± 2 Mpc., Antonela Monachesi, Eric F. Bell, David J. Radburn-Smith, Roelof S. De Jong, Jeremy Bailin, Julianne J. Dalcanton, Benne W. Holwerda, H. Alyson Ford, David Streich, Marija Vlajic, Daniel B. Zucker Jan 2014

Ghosts I : A New Faint Very Isolated Dwarf Galaxy At D = 12 ± 2 Mpc., Antonela Monachesi, Eric F. Bell, David J. Radburn-Smith, Roelof S. De Jong, Jeremy Bailin, Julianne J. Dalcanton, Benne W. Holwerda, H. Alyson Ford, David Streich, Marija Vlajic, Daniel B. Zucker

Faculty and Staff Scholarship

We report the discovery of a new faint dwarf galaxy, GHOSTS I, using HST/ACS data from one of our GHOSTS (Galaxy Halos, Outer disks, Substructure, Thick disk, and Star clusters) fields. Its detected individual stars populate an approximately 1 mag range of its luminosity function (LF). Using synthetic color–magnitude diagrams (CMDs) to compare with the galaxy’s CMD, we find that the colors and magnitudes of GHOSTS I’s individual stars are most consistent with being young helium-burning and asymptotic giant branch stars at a distance of ∼12±2 Mpc. Morphologically, GHOSTS I appears to be actively forming stars, so we tentatively classify …

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Constraining The Age Of The Ngc 4565 Hi Disk Warp : Determining The Origin Of Gas Warps., David J. Radburn-Smith, Roelof S. De Jong, David Streich, Eric F. Bell, Julianne J. Dalcanton, Andrew E. Dolphin, Adrienne M. Stilp, Antonela Monachesi, Benne W. Holwerda, Jeremy Bailin Jan 2014

Constraining The Age Of The Ngc 4565 Hi Disk Warp : Determining The Origin Of Gas Warps., David J. Radburn-Smith, Roelof S. De Jong, David Streich, Eric F. Bell, Julianne J. Dalcanton, Andrew E. Dolphin, Adrienne M. Stilp, Antonela Monachesi, Benne W. Holwerda, Jeremy Bailin

Faculty and Staff Scholarship

We have mapped the distribution of young and old stars in the gaseous H i warp of NGC 4565. We find a clear correlation of young stars (< 600 Myr) with the warp but no coincident old stars (> 1 Gyr), which places an upper limit on the age of the structure. The formation rate of the young stars, which increased ∼ 300 Myr ago relative to the surrounding regions, is (6.3+2.5 −1.5) × 10−5 M yr−1 kpc−2. This implies a ∼ 60 ± 20 Gyr depletion time of the H i warp, similar to the timescales calculated for the outer H i disks of nearby spiral galaxies. While some stars …

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Morphological Parameters Of A Spitzer Survey Of Stellar Structure In Galaxies., Benne W. Holwerda, J. C. Munoz-Mateos, S. Comeron, S. Meidt, K. Sheth, S. Laine, J. L. Hinz, M. W. Regan, A. Gil De Paz, K. Menendez-Delmestre, M. Seibert, T. Kim, T. Mizusawa, E. Laurikainen, H. Salo, J. Laine, D. A. Gadotti, D. Zaritsky, S. Erroz-Ferrer, L. C. Ho, J. H. Knapen, E. Athanassoula, A. Bosma, N. Pirzkal Jan 2014

Morphological Parameters Of A Spitzer Survey Of Stellar Structure In Galaxies., Benne W. Holwerda, J. C. Munoz-Mateos, S. Comeron, S. Meidt, K. Sheth, S. Laine, J. L. Hinz, M. W. Regan, A. Gil De Paz, K. Menendez-Delmestre, M. Seibert, T. Kim, T. Mizusawa, E. Laurikainen, H. Salo, J. Laine, D. A. Gadotti, D. Zaritsky, S. Erroz-Ferrer, L. C. Ho, J. H. Knapen, E. Athanassoula, A. Bosma, N. Pirzkal

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The morphology of galaxies can be quantified to some degree using a set of scale-invariant parameters. Concentration (C), asymmetry (A), smoothness (S), the Gini index (G), the relative contribution of the brightest pixels to the secondorder moment of the flux (M20), ellipticity (E), and the Gini index of the second-order moment (GM) have all been applied to morphologically classify galaxies at various wavelengths. Here, we present a catalog of these parameters for the Spitzer Survey of stellar structure in Galaxies, a volume-limited, near-infrared (NIR) imaging survey of nearby galaxies using the 3.6 and 4.5μm channels of the Infrared Array Camera …

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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 Oct 2013

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 Oct 2013

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

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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 Aug 2013

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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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 Aug 2013

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

Faculty and Staff Scholarship

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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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 Aug 2013

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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Emission-Line Galaxies From The Hubble Space Telescope Probing Evolution And Reionization Spectroscopically (Pears) Grism Survey. Ii. The Complete Sample., N. Pirzkal, Barry Rothberg, Chun Ly, Sangeeta Malhotra, James E. Rhoads, Norman A. Grogin, Tomas Dahlen, Kai G. Noeske, Gerhardt R. Meurer, Jeremy R. Walsh, Nimish P. Hathi, Seth H. Cohen, Andrea Bellini, Benne W. Holwerda, Amber N. Straughn, Matthew Mechtley, Rogier A. Windhorst Jul 2013

Emission-Line Galaxies From The Hubble Space Telescope Probing Evolution And Reionization Spectroscopically (Pears) Grism Survey. Ii. The Complete Sample., N. Pirzkal, Barry Rothberg, Chun Ly, Sangeeta Malhotra, James E. Rhoads, Norman A. Grogin, Tomas Dahlen, Kai G. Noeske, Gerhardt R. Meurer, Jeremy R. Walsh, Nimish P. Hathi, Seth H. Cohen, Andrea Bellini, Benne W. Holwerda, Amber N. Straughn, Matthew Mechtley, Rogier A. Windhorst

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We present a full analysis of the Probing Evolution And Reionization Spectroscopically (PEARS) slitess grism spectroscopic data obtained with the Advanced Camera for Surveys on board Hubble Space Telescope. PEARS covers fields within both the Great Observatories Origins Deep Survey (GOODS) North and South fields, making it ideal as a random survey of galaxies, as well as the availability of a wide variety of ancillary observations complemented by the spectroscopic results. Using the PEARS data, we are able to identify star-forming galaxies (SFGs) within the redshift volume 0 < z < 1.5. Star-forming regions in the PEARS survey are pinpointed independently of the host galaxy. This method allows us to detect the presence of multiple emission-line regions (ELRs) within a single galaxy. We identified a total of 1162 Hα, [O iii], and/or [O ii] emission lines in the PEARS sample of 906 galaxies to a limiting flux of ∼10−18 erg s−1 cm−2. The ELRs have also been compared to the properties of the host galaxy, including morphology, luminosity, and mass. From this analysis, we find three key results: (1) the computed line luminosities show evidence of a flattening in the luminosity function with increasing redshift; (2) the star-forming systems show evidence of complex morphologies with star formation occurring predominantly within one effective (half-light) radius. However, the morphologies show no correlation with host stellar mass. (3) Also, the number density of SFGs with M∗ 109 M decreases by an order of magnitude at z 0.5 relative to the number at 0.5 < z < 0.9, supporting the argument of galaxy downsizing.

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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 Jul 2013

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

Faculty and Staff Scholarship

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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Vlt/Vimos Observations Of An Occulting Galaxy Pair : Redshifts And Effective Extinction Curve., Benne W. Holwerda, T. Boker, J. J. Dalcanton, W. C. Keel, R. S. De Jong Jun 2013

Vlt/Vimos Observations Of An Occulting Galaxy Pair : Redshifts And Effective Extinction Curve., Benne W. Holwerda, T. Boker, J. J. Dalcanton, W. C. Keel, R. S. De Jong

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We present Very Large Telescope/Visible Multiobject Spectrograph Integral Field Unit observations of an occulting galaxy pair previously discovered in Hubble Space Telescope (HST) observations. The foreground galaxy is a low-inclination spiral disc, which causes clear attenuation features seen against the bright bulge and disc of the background galaxy. We find redshifts of z = 0.064 ± 0.003 and 0.065 for the foreground and background galaxy, respectively. This relatively small difference does not rule out gravitational interaction between the two galaxies. Emission line ratios point to a star-forming, not active galactic nuclei dominated foreground galaxy. We fit the Cardelli, Clayton and …

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Testing Galaxy Formation Models With The Ghosts Survey : The Color Profile Of M81'S Stellar Halo., Antonela Monachesi, Eric F. Bell, David J. Radburn-Smith, Marija Vlajic, Roelof S. De Jong, Jeremy Bailin, Julianne J. Dalcanton, Benne W. Holwerda, David Streich Apr 2013

Testing Galaxy Formation Models With The Ghosts Survey : The Color Profile Of M81'S Stellar Halo., Antonela Monachesi, Eric F. Bell, David J. Radburn-Smith, Marija Vlajic, Roelof S. De Jong, Jeremy Bailin, Julianne J. Dalcanton, Benne W. Holwerda, David Streich

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We study the properties of the stellar populations in M81’s outermost part, which hereafter we will call the stellar halo, using Hubble Space Telescope (HST) Advanced Camera for Surveys observations of 19 fields from the GHOSTS survey. The observed fields probe the stellar halo out to a projected distance of ∼50 kpc from the galactic center. Each field was observed in both F606W and F814W filters. The 50% completeness levels of the color–magnitude diagrams (CMDs) are typically at 2 mag below the tip of the red giant branch (TRGB). Fields at distances closer than 15 kpc show evidence of disk-dominated …

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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 Mar 2013

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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Galaxy Zoo : A Catalog Of Overlapping Galaxy Pairs For Dust Studies., William C. Keel, Anna M. Manning, Benne W. Holwerda, Massimo Mezzoprete, Chris J. Lintott, Kevin Schawinski, Pamela Gay, Karen L. Masters Jan 2013

Galaxy Zoo : A Catalog Of Overlapping Galaxy Pairs For Dust Studies., William C. Keel, Anna M. Manning, Benne W. Holwerda, Massimo Mezzoprete, Chris J. Lintott, Kevin Schawinski, Pamela Gay, Karen L. Masters

Faculty and Staff Scholarship

Analysis of galaxies with overlapping images offers a direct way to probe the distribution of dust extinction and its effects on the background light. We present a catalog of 1990 such galaxy pairs selected from the Sloan Digital Sky Survey (SDSS) by volunteers of the Galaxy Zoo project. We highlight subsamples which are particularly useful for retrieving such properties of the dust distribution as UV extinction, the extent perpendicular to the disk plane, and extinction in the inner parts of disks. The sample spans wide ranges of morphology and surface brightness, opening up the possibility of using this technique to …

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