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Articles 3361 - 3390 of 16838

Full-Text Articles in Physical Sciences and Mathematics

A Dust Component ~2 Kpc Above The Plane In Ngc 891., P. Kamphuis, Benne W. Holwerda, R. J. Allen, R. F. Peletier, P. C. Van Der Kruit Mar 2017

A Dust Component ~2 Kpc Above The Plane In Ngc 891., P. Kamphuis, Benne W. Holwerda, R. J. Allen, R. F. Peletier, P. C. Van Der Kruit

Benne Holwerda

Context.The halo of NGC 891 has been the subject of studies for more than a decade. One of its most striking features is the large asymmetry in H emission. In this letter, we will take a quantitative look at this asymmetry at different wavelengths for the first time. Aims.We suggest that NGC 891 is intrinsically almost symmetric and the large asymmetry in H emission is mostly due to dust attenuation. We will quantify the additional optical depth needed to cause the observed asymmetry in this model.Methods.By comparing large strips on the North East side of the galaxy with strips covering …

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An Extended Dust Disk In A Spiral Galaxy : An Occulting Galaxy Pair In The Acs Nearby Galaxy Survey Treasury., Benne W. Holwerda, W. C. Keel, B. Williams, J. J. Dalcanton, R. S. De Jong Mar 2017

An Extended Dust Disk In A Spiral Galaxy : An Occulting Galaxy Pair In The Acs Nearby Galaxy Survey Treasury., Benne W. Holwerda, W. C. Keel, B. Williams, J. J. Dalcanton, R. S. De Jong

Benne Holwerda

We present an analysis of an occulting galaxy pair, serendipitously discovered in the ACS Nearby Galaxy Survey Treasury observations of NGC 253 taken with the Hubble Space Telescope’s (HST) Advanced Camera for Surveys in F475W, F606W, and F814W (SDSS − g, broad V, and I). The foreground disk system (at z 0.06) shows a dusty disk much more extended than the starlight, with spiral lanes seen in extinction out to 1.5 R25, approximately 6 half-light radii. This pair is the first where extinction can be mapped reliably out to this distance from the center. The spiral arms of the extended …

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Host Galaxy Extinction Of Type Ia Supernovae : Co-Evolution Of Interstellar Medium Structure And The Extinction Law With Star Formation., Benne W. Holwerda Mar 2017

Host Galaxy Extinction Of Type Ia Supernovae : Co-Evolution Of Interstellar Medium Structure And The Extinction Law With Star Formation., Benne W. Holwerda

Benne Holwerda

This paper presents a mechanism that may modify the extinction law for Type Ia supernovae (SNeIa) observed at higher redshift. Starting from the observations that (i) SNeIa occur predominantly in spiral galaxies, (ii) star formation ejects interstellar medium (ISM) out of the plane of spirals, (iii) star formation alters the extinction properties of the dust in the ISM, and (iv) there is substantially more star formation at higher redshift, I propose that spiral galaxies have a dustier halo in the past than they do now. The ejected material’s lower value of RV will lead to a lower average value (R¯ …

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Wait Until Soil Temps Drop Before Applying Anhydrous Ammonia, John E. Sawyer, Barbara Stewart, William Ehm Mar 2017

Wait Until Soil Temps Drop Before Applying Anhydrous Ammonia, John E. Sawyer, Barbara Stewart, William Ehm

John E. Sawyer

With the early harvest, Iowa’s conservation leaders are encouraging farmers to wait until soil temperatures lower before applying anhydrous ammonia (NH3) this fall. Anhydrous ammonia applied before daily soil temperatures remain below 50 degrees Fahrenheit and continue trending lower can result in the nitrogen loss that can impact crop development and have negative environmental impacts, such as enhanced leaching into groundwater and streams once converted to nitrate.

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Wet Conditions And Change In Soil Profile Nitrate, John E. Sawyer Mar 2017

Wet Conditions And Change In Soil Profile Nitrate, John E. Sawyer

John E. Sawyer

I wrote an ICM News article February 21, 2013, that provided a summary of fall soil profile nitrate sampling results following the 2012 corn harvest. As I cautioned in that and other articles, the amount of nitrate-N that might remain for a 2013 corn crop depends on springtime rainfall. Unfortunately, much of Iowa has received considerable precipitation since soils thawed, especially the eastern two-thirds of Iowa. The two maps of the Midwest region show the total precipitation and deviation from normal since March 7, 2013. Tile lines are flowing again, and nitrate in the profile will move with percolating water. …

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Sulfur Emerges As A Nutritional Issue In Iowa Alfalfa Production, John E. Sawyer, Brian J. Lang, Daniel W. Barker Mar 2017

Sulfur Emerges As A Nutritional Issue In Iowa Alfalfa Production, John E. Sawyer, Brian J. Lang, Daniel W. Barker

John E. Sawyer

Sulfur is often classified as a “secondary” essential element, mainly due to a smaller plant requirement, but also because it is less frequently applied as a fertilizer compared to N, P, and K. This has certainly been the case in Iowa, where research had not documented S deficiency or fertilization need for optimal crop production. However, if deficient, S can have a dramatic effect on plant growth and crop productivity – more than the classification “secondary” would imply.

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Spectrophotometrically Identified Stars In The Pears-N And Pears-S Fields., N. Pirzkal, A. J. Burgasser, S. Malhotra, Benne W. Holwerda, K. C. Sahu, J. E. Rhoads, C. Xu, J. J. Bochanski, J. R. Walsh, R. A. Windhorst, N. P. Hathi, S. H. Cohen Mar 2017

Spectrophotometrically Identified Stars In The Pears-N And Pears-S Fields., N. Pirzkal, A. J. Burgasser, S. Malhotra, Benne W. Holwerda, K. C. Sahu, J. E. Rhoads, C. Xu, J. J. Bochanski, J. R. Walsh, R. A. Windhorst, N. P. Hathi, S. H. Cohen

Benne Holwerda

Deep ACS slitless grism observations and identification of stellar sources are presented within the Great Observatories Origins Deep Survey North and South fields which were obtained in the Probing Evolution And Reionization Spectroscopically (PEARS) program. It is demonstrated that even low-resolution spectra can be a very powerful means of identifying stars in the field, especially low-mass stars with stellar types M0 and later. The PEARS fields lay within the larger GOODS fields, and we used new, deeper images to further refine the selection of stars in the PEARS field, down to a magnitude of z850 = 25 using a newly …

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The Unusual Vertical Mass Distribution Of Ngc 4013 Seen Through The Spitzer Survey Of Stellar Structure In Galaxies (S4g)., Sebastien Comeron, Bruce G. Elmegreen, Johan H. Knapen, Kartik Sheth, Joannah L. Hinz, Michael W. Regan, Armando Gil De Paz, Juan Carlos Munoz-Mateos, Karin Menendez-Delmestre, Mark Seibert, Taehyun Kim, Trisha Mizusawa, Eija Laurikainen, Heikki Salo, Jarkko Laine, E. Athanassoula, Albert Bosma, Ronald J. Buta, Dimitri A. Gadotti, Luis C. Ho, Benne W. Holwerda, Eva Schinnerer, Dennis Zaritsky Mar 2017

The Unusual Vertical Mass Distribution Of Ngc 4013 Seen Through The Spitzer Survey Of Stellar Structure In Galaxies (S4g)., Sebastien Comeron, Bruce G. Elmegreen, Johan H. Knapen, Kartik Sheth, Joannah L. Hinz, Michael W. Regan, Armando Gil De Paz, Juan Carlos Munoz-Mateos, Karin Menendez-Delmestre, Mark Seibert, Taehyun Kim, Trisha Mizusawa, Eija Laurikainen, Heikki Salo, Jarkko Laine, E. Athanassoula, Albert Bosma, Ronald J. Buta, Dimitri A. Gadotti, Luis C. Ho, Benne W. Holwerda, Eva Schinnerer, Dennis Zaritsky

Benne Holwerda

NGC 4013 is a nearby Sb edge-on galaxy known for its “prodigious” H i 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 3.6μm images from the Spitzer Survey of Stellar Structure in Galaxies. We find evidence for NGC …

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The Thick Disk In The Galaxy Ngc 4244 From S4g Imaging., Sebastien Comeron, Johan H. Knapen, Kartik Sheth, Michael Regan, Joannah L. Hinz, Armando Gil De Paz, Karin Menendez-Delmestre, Juan Carlos Munoz-Mateos, Mark Seibert, Taehyun Kim, E. Athanassoula, Albert Bosma, Ronald J. Buta, Bruce G. Elmegreen, Luis C. Ho, Benne W. Holwerda, Eija Laurikainen, Heikki Salo, Eva Schinnerer Mar 2017

The Thick Disk In The Galaxy Ngc 4244 From S4g Imaging., Sebastien Comeron, Johan H. Knapen, Kartik Sheth, Michael Regan, Joannah L. Hinz, Armando Gil De Paz, Karin Menendez-Delmestre, Juan Carlos Munoz-Mateos, Mark Seibert, Taehyun Kim, E. Athanassoula, Albert Bosma, Ronald J. Buta, Bruce G. Elmegreen, Luis C. Ho, Benne W. Holwerda, Eija Laurikainen, Heikki Salo, Eva Schinnerer

Benne Holwerda

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 (S4G) 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 …

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The Onset Of Warps In Spitzer Observations Of Edge-On Spiral Galaxies., Kanak Saha, Roelof De Jong, Benne W. Holwerda Mar 2017

The Onset Of Warps In Spitzer Observations Of Edge-On Spiral Galaxies., Kanak Saha, Roelof De Jong, Benne W. Holwerda

Benne Holwerda

We analyse warps in the nearby edge-on spiral galaxies observed in the Spitzer/Infrared Array Camera (IRAC )4.5-μm band. In our sample of 24 galaxies, we find evidence of warp in 14 galaxies. We estimate the observed onset radii for the warps in a subsample of 10 galaxies. The dark matter distribution in each of these galaxies are calculated using the mass distribution derived from the observed light distribution and the observed rotation curves. The theoretical predictions of the onset radii for the warps are then derived by applying a self-consistent linear response theory to the obtained mass models for six …

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The Ghosts Survey. I. Hubble Space Telescope Advanced Camera For Surveys Data., D. J. Radburn-Smith, R. S. De Jong, A. C. Seth, J. Bailin, E. F. Bell, T. M. Brown, J. S. Bullock, S. Courteau, J. J. Dalcanton, H. C. Ferguson, P. Goudfrooij, S. Holfeltz, Benne W. Holwerda, C. Purcell, J. Sick, D. Streich, M. Vlajic, D. B. Zucker Mar 2017

The Ghosts Survey. I. Hubble Space Telescope Advanced Camera For Surveys Data., D. J. Radburn-Smith, R. S. De Jong, A. C. Seth, J. Bailin, E. F. Bell, T. M. Brown, J. S. Bullock, S. Courteau, J. J. Dalcanton, H. C. Ferguson, P. Goudfrooij, S. Holfeltz, Benne W. Holwerda, C. Purcell, J. Sick, D. Streich, M. Vlajic, D. B. Zucker

Benne Holwerda

We present an overview of the GHOSTS survey, the largest study to date of the resolved stellar populations in the outskirts of disk galaxies. The sample consists of 14 disk galaxies within 17 Mpc, whose outer disks and halos are imaged with the Hubble Space Telescope Advanced Camera for Surveys (ACS). In the first paper of this series, we describe the sample, explore the benefits of using resolved stellar populations, and discuss our ACS F606W and F814W photometry. We use artificial star tests to assess completeness and use overlapping regions to estimate photometric uncertainties. The median depth of the survey …

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Thick Disks Of Edge-On Galaxies Seen Through The Spitzer Survey Of Stellar Structure In Galaxies (S4g) : Lair Of Missing Baryons?, Sebastien Comeron, Bruce G. Elmegreen, Johan H. Knapen, Heikki Salo, Eija Laurikainen, Jarkko Laine, E. Athanassoula, Albert Bosma, Kartik Sheth, Michael W. Regan, Joannah L. Hinz, Armando Gil De Paz, Karin Menendez-Delmestre, Trisha Mizusawa, Juan Carlos Munoz-Mateos, Mark Seibert, Taehyun Kim, Debra M. Elmegreen, Dimitri A. Gadotti, Luis C. Ho, Benne W. Holwerda, Jani Lappalainen, Eva Schinnerer, Ramin Skibba Mar 2017

Thick Disks Of Edge-On Galaxies Seen Through The Spitzer Survey Of Stellar Structure In Galaxies (S4g) : Lair Of Missing Baryons?, Sebastien Comeron, Bruce G. Elmegreen, Johan H. Knapen, Heikki Salo, Eija Laurikainen, Jarkko Laine, E. Athanassoula, Albert Bosma, Kartik Sheth, Michael W. Regan, Joannah L. Hinz, Armando Gil De Paz, Karin Menendez-Delmestre, Trisha Mizusawa, Juan Carlos Munoz-Mateos, Mark Seibert, Taehyun Kim, Debra M. Elmegreen, Dimitri A. Gadotti, Luis C. Ho, Benne W. Holwerda, Jani Lappalainen, Eva Schinnerer, Ramin Skibba

Benne Holwerda

Most, if not all, disk galaxies have a thin (classical) disk and a thick disk. In most models thick disks are thought to be a necessary consequence of the disk formation and/or evolution of the galaxy. We present the results of a study of the thick disk properties in a sample of carefully selected edge-on galaxies with types ranging from T = 3 to T = 8. We fitted one-dimensional luminosity profiles with physically motivated functions—the solutions of two stellar and one gaseous isothermal coupled disks in equilibrium—which are likely to yield more accurate results than other functions used in …

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The Brightest Of Reionizing Galaxies Survey : Constraints On The Bright End Of The Z ~ 8 Luminosity Function., L. D. Bradley, M. Trenti, P. A. Oesch, M. Stiavelli, T. Treu, R. J. Bouwens, J. M. Shull, Benne W. Holwerda, N. Pirzkal Mar 2017

The Brightest Of Reionizing Galaxies Survey : Constraints On The Bright End Of The Z ~ 8 Luminosity Function., L. D. Bradley, M. Trenti, P. A. Oesch, M. Stiavelli, T. Treu, R. J. Bouwens, J. M. Shull, Benne W. Holwerda, N. Pirzkal

Benne Holwerda

We report the discovery of 33 Lyman-break galaxy candidates at z ∼ 8 detected in Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging as part of the Brightest of Reionizing Galaxies (BoRG) pure-parallel survey. The ongoing BoRG survey currently has the largest area (274 arcmin2) with Y098 (or Y105), J125, and H160 band coverage needed to search for z ∼ 8 galaxies, about three times the current CANDELS area, and slightly larger than what will be the final CANDELS wide component with Y105 data (required to select z ∼ 8 sources). Our sample of 33 relatively bright Y098-dropout galaxies …

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The S4g Perspective On Circumstellar Dust Extinction Of Asymptotic Giant Branch Stars In M100., Sharon Meidt, Eva Schinnerer, Juan Carlos Munoz-Mateos, Benne W. Holwerda, Luis C. Ho, Barry F. Madore, Johan H. Knapen, Albert Bosma, E. Athanassoula, Joannah L. Hinz, Kartik Sheth, Michael Regan, Armando Gil De Paz, Karin Menendez-Delmestre, Mark Seibert, Taehyun Kim, Trisha Mizusawa, Dimitri A. Gadotti, Eija Laurikainen, Heikki Salo, Jarkko Laine, Sebastien Comeron Mar 2017

The S4g Perspective On Circumstellar Dust Extinction Of Asymptotic Giant Branch Stars In M100., Sharon Meidt, Eva Schinnerer, Juan Carlos Munoz-Mateos, Benne W. Holwerda, Luis C. Ho, Barry F. Madore, Johan H. Knapen, Albert Bosma, E. Athanassoula, Joannah L. Hinz, Kartik Sheth, Michael Regan, Armando Gil De Paz, Karin Menendez-Delmestre, Mark Seibert, Taehyun Kim, Trisha Mizusawa, Dimitri A. Gadotti, Eija Laurikainen, Heikki Salo, Jarkko Laine, Sebastien Comeron

Benne Holwerda

We examine the effect of circumstellar dust extinction on the near-IR (NIR) contribution of asymptotic giant branch (AGB) stars in intermediate-age clusters throughout the disk of M100. For our sample of 17 AGB-dominated clusters we extract optical-to-mid-IR spectral energy distributions (SEDs) and find that NIR brightness is coupled to the mid-IR dust emission in such a way that a significant reduction of AGB light, of up to 1 mag in the K band, follows from extinction by the dust shell formed during this stage. Since the dust optical depth varies with AGB chemistry (C-rich or O-rich), our results suggest that …

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Herschel/Spire Observations Of The Dusty Disk Of Ngc 4244., Benne W. Holwerda, S. Bianchi, T. Boker, D. Radburn-Smith, R. S. De Jong, M. Baes, P. C. Van Der Kruit, M. Xilouris, K. D. Gordon, J. J. Dalcanton Mar 2017

Herschel/Spire Observations Of The Dusty Disk Of Ngc 4244., Benne W. Holwerda, S. Bianchi, T. Boker, D. Radburn-Smith, R. S. De Jong, M. Baes, P. C. Van Der Kruit, M. Xilouris, K. D. Gordon, J. J. Dalcanton

Benne Holwerda

We present Herschel/SPIRE images at 250, 350, and 500 μm of NGC 4244, a typical low-mass, disk-only and edge-on spiral galaxy. The dust disk is clumpy and shows signs of truncation at the break radius of the stellar disk. This disk coincides with the densest part of the Hi disk. We compare the spectral energy distribution (SED), including the new SPIRE fluxes, to 3D radiative transfer models; a smooth model disk and a clumpy model with embedded heating. Each model requires a very high value for the dust scale-length (hd = 2−5 h∗), higher dust masses than previous models of …

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Quantified H I Morphology : Vi. The Morphology Of Extended Discs In Uv And H I., Benne W. Holwerda, N. Pirzkal, J. S. Heiner Mar 2017

Quantified H I Morphology : Vi. The Morphology Of Extended Discs In Uv And H I., Benne W. Holwerda, N. Pirzkal, J. S. Heiner

Benne Holwerda

Extended ultraviolet (XUV) discs have been found in a substantial fraction of late-type – S0, spiral and irregular – galaxies. Similarly, most late-type spirals have an extended gas disc, observable in the 21-cm radio line (H i). The morphology of galaxies can be quantified well using a series of scale-invariant parameters; concentration-asymmetry-smoothness (CAS), Gini, M20, and GM parameters. In this series of papers, we apply these to H i column density maps to identify mergers and interactions, lopsidedness and now XUV discs. In this paper, we compare the quantified morphology and effective radius (R50) of the Westerbork observations of neutral …

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Quantified H I Morphology – I. Multi-Wavelength Analysis Of The Things Galaxies., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, A. Bouchard, S. -L. Blyth, K. J. Van Der Heyden, E. C. Elson Mar 2017

Quantified H I Morphology – I. Multi-Wavelength Analysis Of The Things Galaxies., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, A. Bouchard, S. -L. Blyth, K. J. Van Der Heyden, E. C. Elson

Benne Holwerda

Galaxy evolution is driven to a large extent by interactions and mergers with other galaxies and the gas in galaxies is extremely sensitive to the interactions. One method to measure such interactions uses the quantified morphology of galaxy images. Well-established parameters are Concentration, Asymmetry, Smoothness, Gini and M20 of a galaxy image. Thus far, the application of this technique has mostly been restricted to rest-frame ultraviolet and optical images. However, with the new radio observatories being commissioned [South African Karoo Array Telescope (MeerKAT), Australian SKA Pathfinder (ASKAP), Extended Very Large Array (EVLA), Westerbork Synthesis Radio Telescope/APERture Tile In Focus instrument …

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Evolution In The Dust Lane Fraction Of Edge-On L*V Spiral Galaxies Since Z = 0.8., Benne W. Holwerda, J. J. Dalcanton, D. Radburn-Smith, R. S. De Jong, P. Guhathakurta, A. Koekemoer, R. J. Allen, T. Boker Mar 2017

Evolution In The Dust Lane Fraction Of Edge-On L*V Spiral Galaxies Since Z = 0.8., Benne W. Holwerda, J. J. Dalcanton, D. Radburn-Smith, R. S. De Jong, P. Guhathakurta, A. Koekemoer, R. J. Allen, T. Boker

Benne Holwerda

The presence of a well-defined and narrow dust lane in an edge-on spiral galaxy is the observational signature of a thin and dense molecular disk, in which gravitational collapse has overcome turbulence. Using a sample of galaxies out to z ∼ 1 extracted from the COSMOS survey, we identify the fraction of massive (L∗ V ) disks that display a dust lane. Our goal is to explore the evolution in the stability of the molecular interstellar medium (ISM) disks in spiral galaxies over a cosmic timescale. We check the reliability of our morphological classifications against changes in rest-frame wavelength, resolution, …

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Quantified H I Morphology – Ii. Lopsidedness And Interaction In Whisp Column Density Maps., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, A. Bouchard, S. -L. Blyth, K. J. Van Der Heyden, E. C. Elson Mar 2017

Quantified H I Morphology – Ii. Lopsidedness And Interaction In Whisp Column Density Maps., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, A. Bouchard, S. -L. Blyth, K. J. Van Der Heyden, E. C. Elson

Benne Holwerda

Lopsidedness of the gaseous disc of spiral galaxies is a common phenomenon in disc morphology, profile and kinematics. Simultaneously, the asymmetry of a galaxy’s stellar disc, in combination with other morphological parameters, has seen extensive use as an indication of recent merger or interaction in galaxy samples. Quantified morphology of stellar spiral discs is one avenue to determine the merger rate over much of the age of the Universe. In this paper, we measure the quantitative morphology parameters for the H I column density maps from the Westerbork observations of neutral Hydrogen in Irregular and SPiral galaxies (WHISP). These are …

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Breaks In Thin And Thick Disks Of Edge-On Galaxies Imaged In The Spitzer Survey Of Stellar Structure In Galaxies (S4g)., Sebastien Comeron, Bruce G. Elmegreen, Heikki Salo, Eija Laurikainen, E. Athanassoula, Albert Bosma, Johan H. Knapen, Dimitri A. Gadotti, Kartik Sheth, Joannah L. Hinz, Michael W. Regan, Armando Gil De Paz, Juan Carlos Munoz-Mateos, Karin Menendez-Delmestre, Mark Seibert, Taehyun Kim, Trisha Mizusawa, Jarkko Laine, Luis C. Ho, Benne W. Holwerda Mar 2017

Breaks In Thin And Thick Disks Of Edge-On Galaxies Imaged In The Spitzer Survey Of Stellar Structure In Galaxies (S4g)., Sebastien Comeron, Bruce G. Elmegreen, Heikki Salo, Eija Laurikainen, E. Athanassoula, Albert Bosma, Johan H. Knapen, Dimitri A. Gadotti, Kartik Sheth, Joannah L. Hinz, Michael W. Regan, Armando Gil De Paz, Juan Carlos Munoz-Mateos, Karin Menendez-Delmestre, Mark Seibert, Taehyun Kim, Trisha Mizusawa, Jarkko Laine, Luis C. Ho, Benne W. Holwerda

Benne Holwerda

Breaks in the radial luminosity profiles of galaxies have until now been mostly studied averaged over disks. Here, we study separately breaks in thin and thick disks in 70 edge-on galaxies using imaging from the Spitzer Survey of Stellar Structure in Galaxies. We built luminosity profiles of the thin and thick disks parallel to midplanes and we found that thin disks often truncate (77%). Thick disks truncate less often (31%), but when they do, their break radius is comparable with that in the thin disk. This suggests either two different truncation mechanisms—one of dynamical origin affecting both disks simultaneously and …

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Quantified H I Morphology – Iv. The Merger Fraction And Rate In Whisp., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, A. Bouchard, S. -L. Blyth, K. J. Van Der Heyden Mar 2017

Quantified H I Morphology – Iv. The Merger Fraction And Rate In Whisp., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, A. Bouchard, S. -L. Blyth, K. J. Van Der Heyden

Benne Holwerda

The morphology of the atomic hydrogen (H I) disc of a spiral galaxy is the first component to be disturbed by a gravitational interaction such as a merger between two galaxies. We use a simple parametrization of the morphology of H I column density maps of the Westerbork observations of neutral Hydrogen in Irregular and SPiral galaxies (WHISP) project to select those galaxies that are likely undergoing a significant interaction. Merging galaxies occupy a particular part of parameter space defined by Asymmetry (A), the relative contribution of the 20 per cent brightest pixels to the second-order moment of the column …

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Quantified H I Morphology – V. H I Discs In The Virgo Cluster., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, W. Van Driel Mar 2017

Quantified H I Morphology – V. H I Discs In The Virgo Cluster., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, W. Van Driel

Benne Holwerda

We explore the quantified morphology of atomic hydrogen (H i) discs in the Virgo cluster. These galaxies display a wealth of phenomena in their H i morphology, e.g., tails, truncation and warps. These morphological disturbances are related to the ram pressure stripping and tidal interaction that galaxies undergo in this dense cluster environment. To quantify the morphological transformation of the H i discs, we compute the morphological parameters of Concentration, Asymmetry, Smoothness, Gini and M20 and our own GM for 51 galaxies in 48 H i column density maps from the VLA Imaging of Virgo spirals in Atomic gas (VIVA) …

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Outer-Disk Populations In Ngc 7793 : Evidence For Stellar Radial Migration., David J. Radburn-Smith, Rok Roskar, Victor P. Debattista, Julianne J. Dalcanton, David Streich, Roelof S. De Jong, Marija Vlajic, Benne W. Holwerda, Chris W. Purcell, Andrew E. Dolphin, Daniel B. Zucker Mar 2017

Outer-Disk Populations In Ngc 7793 : Evidence For Stellar Radial Migration., David J. Radburn-Smith, Rok Roskar, Victor P. Debattista, Julianne J. Dalcanton, David Streich, Roelof S. De Jong, Marija Vlajic, Benne W. Holwerda, Chris W. Purcell, Andrew E. Dolphin, Daniel B. Zucker

Benne Holwerda

We analyzed the radial surface brightness profile of the spiral galaxy NGC 7793 using HST/ACS images from the GHOSTS survey and a new HST/WFC3 image across the disk break. We used the photometry of resolved stars to select distinct populations covering a wide range of stellar ages. We found breaks in the radial profiles of all stellar populations at 280 (∼5.1 kpc). Beyond this disk break, the profiles become steeper for younger populations. This same trend is seen in numerical simulations where the outer disk is formed almost entirely by radial migration. We also found that the older stars of …

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A Unified Picture Of Breaks And Truncations In Spiral Galaxies From Sdss And S4g Imaging., Ignacio Martin-Navarro, Judit Bakos, Ignacio Trujillo, Johan H. Knapen, E. Athanassoula, A. Bosma, Sebastien Comeron, Bruce G. Elmegreen, Santiago Erroz-Ferrer, 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 Mar 2017

A Unified Picture Of Breaks And Truncations In Spiral Galaxies From Sdss And S4g Imaging., Ignacio Martin-Navarro, Judit Bakos, Ignacio Trujillo, Johan H. Knapen, E. Athanassoula, A. Bosma, Sebastien Comeron, Bruce G. Elmegreen, Santiago Erroz-Ferrer, 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

Benne Holwerda

The mechanism causing breaks in the radial surface-brightness distribution of spiral galaxies is not yet well known. Despite theoretical efforts, there is not a unique explanation for these features and the observational results are not conclusive. In an attempt to address this problem, we have selected a sample of 34 highly inclined spiral galaxies present in both the Sloan Digital Sky Survey (SDSS) and the Spitzer Survey of Stellar Structure in Galaxies (S4G). We have measured the surface-brightness profiles in the five Sloan optical bands and in the 3.6-µm Spitzer band. We have also calculated the colour and stellar surface …

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Quantified H I Morphology – Iii. Merger Visibility Times From H I In Galaxy Simulations., Benne W. Holwerda, N. Pirzkal, T. J. Cox, W. J. G. De Blok, J. Weniger, A. Bouchard, S. -L. Blyth, K. J. Van Der Heyden Mar 2017

Quantified H I Morphology – Iii. Merger Visibility Times From H I In Galaxy Simulations., Benne W. Holwerda, N. Pirzkal, T. J. Cox, W. J. G. De Blok, J. Weniger, A. Bouchard, S. -L. Blyth, K. J. Van Der Heyden

Benne Holwerda

Major mergers of disc galaxies are thought to be a substantial driver in galaxy evolution. To trace the fraction and rate of galaxy mergers over cosmic times, several observational techniques have been developed over the last decade, including parametrized morphological selection. We apply this morphological selection of mergers to 21 cm radio emission line (H I) column density images of spiral galaxies in nearby surveys. In this paper, we investigate how long a 1:1 merger is visible in H I from N-body simulations. We evaluate the merger visibility times for selection criteria based on four parameters: Concentration, Asymmetry, M20 and …

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Xu_Pccp(2017)_Exp_H2o++Co.Pdf, Yuntao Xu Mar 2017

Xu_Pccp(2017)_Exp_H2o++Co.Pdf, Yuntao Xu

Yuntao Xu

No abstract provided.

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Properties Of Spacecraft Materials Exposed To Ionizing Radiation, Alex Souvall, Gregory Wilson, Katie Gamaunt, Ben Russon, Heather Tippets, Jr Dennison Mar 2017

Properties Of Spacecraft Materials Exposed To Ionizing Radiation, Alex Souvall, Gregory Wilson, Katie Gamaunt, Ben Russon, Heather Tippets, Jr Dennison

Katie Gamaunt

The effects of ionizing radiation damage on the various properties of spacecraft materials resulting from exposure in the Space Survivability Testing chamber (SST) are being studied with both ex situ and in situ tests. The SST is a ground based test facility designed to mimic low earth orbit (LEO), and geosynchronous orbit to test potential environmental-induced modifications to small satellites , and materials. Tests described here expose spacecraft materials to a Sr90 ionizing beta radiation source at room temperature and in high vacuum. Ex situ optical transmission/reflectivity measurements glass samples will monitor optical darkening. Properties of polymeric samples will …

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The Space Survivability Test Chamber, Katie Gamaunt, Heather Tippets, Alex Souvall, Ben Russon, Jr Dennison Mar 2017

The Space Survivability Test Chamber, Katie Gamaunt, Heather Tippets, Alex Souvall, Ben Russon, Jr Dennison

Katie Gamaunt

The Space Survivability Test chamber is a new ground-based research instrument being used for accelerated testing of environment-induced modifications of diverse samples. The chamber simulates space environment conditions, including neutral gas atmospheres and vacuum (<10-5 Pa) environments, temperature (~100 K to >450 K), ionizing radiation, electron fluxes (<10 eV to ~2½ MeV), and vacuum ultraviolet through mid-infrared photon fluxes. This versatile test chamber is well-suited for cost-effective testing of complete systems up to the size (< 20 cm dia.) of a 1U CubeSat, smaller components or electronics, and individual material samples. Multiple in-flux or in-situ space survivability and radiation exposure tests can be performed simultaneously, …

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Measurement Of Effects Of Long Term Ionizing Radiation On High Efficiency Solar Arrays, Ben Russon, Heather Tippets, Gregory Wilson, Katie Gamaunt, Alex Souvall, Jr Dennison Mar 2017

Measurement Of Effects Of Long Term Ionizing Radiation On High Efficiency Solar Arrays, Ben Russon, Heather Tippets, Gregory Wilson, Katie Gamaunt, Alex Souvall, Jr Dennison

Katie Gamaunt

Degradation of power output efficiency for high-efficiency multilayer solar arrays due to ionizing radiation is measured using the Space Survivability Test chamber. Exposure to ionizing radiation disrupts the crystalline structure and can reduce solar array power output to the point that it no longer provides adequate output capacity. This can be a significant concern, particularly in the harsh environment of space where radiation dose rate is significantly higher and replacing components is often impossible. Ionizing radiation is simulated in a controlled environment to allow measurement and characterization of the power output of solar arrays, using a 100 mCi encapsulated Sr90 …

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Uv Degradation Effects: Terrestrial Versus Space Environment, Katie Gamaunt, Krysta Moser, Alex Souvall, Jr Dennison Mar 2017

Uv Degradation Effects: Terrestrial Versus Space Environment, Katie Gamaunt, Krysta Moser, Alex Souvall, Jr Dennison

Katie Gamaunt

The decrease in visible and ultraviolet transmission spectra of polymeric and glass spacecraft materials has been measured to determine the extent of degradation due to high energy UV radiation similar to the solar spectrum (both above and below the stratosphere). This project looked at the effects that the atmosphere has in regards to blocking UV radiation and thus, slowing down the UV degradation process. Materials such as quartz, borosilicate glass, sodium glasses, polyethylene, polyimide, and polyethylene terephthalate polymers were exposed to radiation from a focused high intensity deuterium lamp source, which generates radiation in the UVA and UVB spectrum. Duplicates …

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