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Search Results: 1 - 10 of 489164 matches for " Daniel A. Dale "
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The Convergence Depth of the Local Peculiar Velocity Field
Daniel A. Dale,Riccardo Giovanelli
Physics , 1999,
Abstract: We have obtained Tully-Fisher (TF) measurements for some 3000 late-type galaxies in the field and in 76 clusters distributed throughout the sky between 10 and 200\h Mpc. The cluster data are applied to the construction of an I band TF template, resulting in a relation with a scatter of 0.35 magnitudes and a zero-point accurate to 0.02 magnitudes. Peculiar motions are computed by referral to the template relation, and the distribution of line-of-sight cluster peculiar motions is presented. The dipole of the reflex motion of the Local Group of galaxies with respect to galaxies with measured peculiar velocity converges to the CMB dipole within less than 6000 km/s. The progression of this convergence is well illustrated when the reflex motion is referred to a well-distributed sample of field galaxies, and it is maintained when the reflex motion is referred to the reference frame constituted by the distant clusters in our sample. The field and cluster samples exhibit bulk motion amplitudes of order 200 km/s or smaller. Finally, we apply our sample of cluster peculiar velocities to a test of the putative Hubble bubble recently claimed by Zehavi and coworkers. In contrast to their findings, our data support a relatively quiescent Hubble flow beyond 35\h Mpc.
The Infrared Spectral Energy Distribution of Normal Star-Forming Galaxies: Calibration at Far-Infrared and Submillimeter Wavelengths
Daniel A. Dale,George Helou
Physics , 2002, DOI: 10.1086/341632
Abstract: New far-infrared and submillimeter data are used to solidify and to extend to long wavelengths the empirical calibration of the infrared spectral energy distribution (SED) of normal star-forming galaxies. As was found by Dale et al. (2001), a single parameter family, characterized by f_nu(60 microns)/f_nu(100 microns), is adequate to describe the range of normal galaxy spectral energy distributions observed by IRAS and ISO from 3 to 100 microns. However, predictions based on the first generation models at longer wavelengths (122 to 850 microns) are increasingly overluminous compared to the data for smaller f_nu(60 microns)/f_nu(100 microns), or alternatively, for weaker global interstellar radiation fields. After slightly modifying the far-infrared/submillimeter dust emissivity in those models as a function of the radiation field intensity to better match the long wavelength data, a suite of SEDs from 3 microns to 20 cm in wavelength is presented. Results from relevant applications are also discussed, including submillimeter-based photometric redshift indicators, the infrared energy budget and simple formulae for recovering the bolometric infrared luminosity, and dust mass estimates in galaxies. Regarding the latter, since galaxy infrared SEDs are not well-described by single blackbody curves, the usual methods of estimating dust masses can be grossly inadequate. The improved model presented herein is used to provide a more accurate relation between infrared luminosity and dust mass.
Signatures of Galaxy-Cluster Interactions: Tully-Fisher Observations at z~0.1
Daniel A. Dale,Juan M. Uson
Physics , 2003, DOI: 10.1086/376478
Abstract: We have obtained new optical imaging and spectroscopic observations of 78 galaxies in the fields of the rich clusters Abell 1413 (z = 0.14), Abell 2218 (z = 0.18) and Abell 2670 (z = 0.08). We have detected line emission from 25 cluster galaxies plus an additional six galaxies in the foreground and background, a much lower success rate than what was found (65%) for a sample of 52 lower-richness Abell clusters in the range 0.02 < z < 0.08. We have combined these data with our previous observations of Abell 2029 and Abell 2295 (both at z = 0.08), which yields a sample of 156 galaxies. We evaluate several parameters as a function of cluster environment: Tully-Fisher residuals, H-alpha equivalent width, and rotation curve asymmetry, shape and extent. Although H-alpha is more easily detectable in galaxies that are located further from the cluster cores, we fail to detect a correlation between H-alpha extent and galaxy location in those where it is detected, again in contrast with what is found in the clusters of lesser richness. We fail to detect any statistically significant trends for the other parameters in this study. The zero-point in the z~0.1 Tully-Fisher relation is marginally fainter (by 1.5 sigma) than that found in nearby clusters, but the scatter is essentially unchanged.
Signatures of Interstellar-Intracluster Medium Interactions: Spiral Galaxy Rotation Curves in Abell 2029
Daniel A. Dale,Juan M. Uson
Physics , 2000, DOI: 10.1086/301465
Abstract: We investigate the rich cluster Abell 2029 (z~0.08) using optical imaging and long-slit spectral observations of 52 disk galaxies distributed throughout the cluster field. No strong emission-line galaxies are present within ~400 kpc of the cluster center, a region largely dominated by the similarly-shaped X-ray and low surface brightness optical envelopes centered on the giant cD galaxy. However, two-thirds of the galaxies observed outside the cluster core exhibit line emission. H-alpha rotation curves of 14 cluster members are used in conjunction with a deep I band image to study the environmental dependence of the Tully-Fisher relation. The Tully-Fisher zero-point of Abell 2029 matches that of clusters at lower redshifts, although we do observe a relatively larger scatter about the Tully-Fisher relation. We do not observe any systematic variation in the data with projected distance to the cluster center: we see no environmental dependence of Tully-Fisher residuals, R-I color, H-alpha equivalent width, and the shape and extent of the rotation curves.
Mid-Infrared Observations of Normal Star-Forming Galaxies: The Infrared Space Observatory Key Project Sample
Daniel A. Dale,Nancy A. Silbermann,George Helou
Physics , 2000, DOI: 10.1086/301478
Abstract: We present mid-infrared maps and preliminary analysis for 61 galaxies observed with the ISOCAM instrument aboard the Infrared Space Observatory. Many of the general features of galaxies observed at optical wavelengths---spiral arms, disks, rings, and bright knots of emission---are also seen in the mid-infrared, except the prominent optical bulges are absent at 6.75 and 15 microns. In addition, the maps are quite similar at 6.75 and 15 microns, except for a few cases where a central starburst leads to lower 6.75/15 ratios in the inner region. We also present infrared flux densities and mid-infrared sizes for these galaxies. The mid-infrared color 6.75/15 shows a distinct trend with the far-infrared color 60/100. The quiescent galaxies in our sample (60/100 < 0.6) show 6.75/15 near unity, whereas this ratio drops significantly for galaxies with higher global heating intensity levels. Azimuthally-averaged surface brightness profiles indicate the extent to which the mid-infrared flux is centrally concentrated, and provide information on the radial dependence of mid-infrared colors. The galaxies are mostly well resolved in these maps: almost half of them have < 10% of their flux in the central resolution element. A comparison of optical and mid-infrared isophotal profiles indicates that the optical flux at 4400 Angstroms near the optical outskirts of the galaxies is approximately eight (seven) times that at 6.75 microns (15 microns), comparable with observations of the diffuse quiescent regions of the Milky Way.
Effects of Land Use on Greenhouse Gas Flux in Playa Wetlands and Associated Watersheds in the High Plains, USA  [PDF]
Dale W. Daniel, Loren M. Smith, Scott T. McMurry, Brian A. Tangen, Charles F. Dahl, Ned H. Euliss Jr., Ted LaGrange
Agricultural Sciences (AS) , 2019, DOI: 10.4236/as.2019.102016
Abstract: In the High Plains, U.S., native prairie conversion to cropland agriculture has resulted in a loss of service delivery capabilities from most depressional wetlands as a result of sedimentation. Restoring historic hydrological conditions to affected wetlands may rejuvenate some services, however, there may be tradeoffs due to emissions of CH4 and N2O. We evaluated the influence of two predominant conservation programs (Wetlands Reserve Program, WRP and Conservation Reserve Program, CRP) on gas emissions (CO2, CH4, N2O) from 42 playas and uplands in the High Plains of Nebraska. Because playa restoration through the WRP is most prevalent in the Rainwater Basin (RWB), we studied 27 playas/uplands among reference condition, cropland, and WRP land uses. We studied 15 playas/uplands within native grassland, cropland, and CRP land uses in the Western High Plains (WHP) of Nebraska. Emissions were collected bi-weekly from April-October of 2012 and 2013 from four landscape positions extending outward from the wetland center into upland. In RWB playas, CH4 and N2O emissions were similar among land uses but CO2 was 28% higher in cropland than WRP wetlands. Cropland uplands emitted 648% more N2O than reference and WRP uplands. Overall, net CO2-equiv emissions were lower in playas/uplands in WRP, suggesting that benefits of playa restoration may include climate mitigation services as well as increased water storage capacity and biodiversity provisioning. In the WHP, cropland and grassland playas emitted 46 and 23 times more CH4, respectively, than CRP in 2013. Playas in CRP emitted 43% less N2O than cropland playas. In 2013, net emissions for cropland and native grassland playas were 75% and 39% greater, respectively, than CRP playas. In the WHP, the benefits of lower gas emissions must be appropriately weighted against tradeoffs of ecosystem services related to shorter hydroperiods as a result of reduced runoff into playas in CRP.
The Infrared Spectral Energy Distribution of Normal Star-Forming Galaxies
Daniel A. Dale,George Helou,Alessandra Contursi,Nancy A. Silbermann,Sonali Kolhatkar
Physics , 2000, DOI: 10.1023/A:1012775526521
Abstract: We present a new phenomenological model for the spectral energy distribution of normal star-forming galaxies between 3 and 1100 microns. A sequence of realistic galaxy spectra are constructed from a family of dust emission curves assuming a power law distribution of dust mass over a wide range of interstellar radiation fields. For each interstellar radiation field heating intensity we combine emission curves for large and very small grains and aromatic feature carriers. The model is constrained by IRAS and ISOCAM broadband photometric and ISOPHOT spectrophotometric observations for our sample of 69 normal galaxies; the model reproduces well the empirical spectra and infrared color trends. These model spectra allow us to determine the infrared energy budget for normal galaxies, and in particular to translate far-infrared fluxes into total (bolometric) infrared fluxes. The 20 to 42 micron range appears to show the most significant growth in relative terms as the activity level increases, suggesting that the 20-42 micron continuum may be the best dust emission tracer of current star formation in galaxies. The redshift dependence of infrared color-color diagrams and the far-infrared to radio correlation for galaxies are also explored.
Early-time VLA observations and broad-band afterglow analysis of the Fermi-LAT detected GRB 130907A
Péter Veres,Alessandra Corsi,Dale A. Frail,S. Bradley Cenko,Daniel A. Perley
Physics , 2014, DOI: 10.1088/0004-637X/810/1/31
Abstract: We present multi-wavelength observations of the hyper-energetic gamma-ray burst (GRB) 130907A, a Swift-discovered burst with early radio observations starting at $\approx 4$ hr after the $\gamma$-ray trigger. GRB 130907A was also detected by the Fermi/LAT instrument and, at late times, showed a strong spectral evolution in X-rays. We focus on the early-time radio observations, especially at $>10 $ GHz, to attempt identifying reverse shock signatures. While our radio follow-up of GRB 130907A ranks among the earliest observations of a GRB with the Karl G. Jansky Very Large Array (VLA), we did not see an unambiguous signature of a reverse shock. While a model with both reverse and forward-shock can correctly describe the observations, the data is not constraining enough to decide upon the presence of the reverse-shock component. We model the broad-band data using a simple forward-shock synchrotron scenario with a transition from a wind environment to a constant density interstellar medium (ISM) in order to account for the observed features. Within the confines of this model, we also derive the underlying physical parameters of the fireball, which are within typical ranges except for the wind density parameter ($A_*$), which is higher than those for bursts with wind-ISM transition, but typical for the general population of bursts. We note the importance of early-time radio observations of the afterglow (and of well sampled light curves) to unambiguously identify the potential contribution of the reverse shock.
Towards an Understanding of the Mid-Infrared Surface Brightness of Normal Galaxies
Daniel A. Dale,George Helou,Nancy A. Silbermann,Alessandra Contursi,Sangeeta Malhotra,Robert H. Rubin
Physics , 1999, DOI: 10.1086/301110
Abstract: We report a mid-infrared color and surface brightness analysis of IC 10, NGC 1313, and NGC 6946, three of the nearby galaxies studied under the Infrared Space Observatory Key Project on Normal Galaxies. Images with < 9 arcsecond (170 pc) resolution of these nearly face-on, late-type galaxies were obtained using the LW2 (6.75 mu) and LW3 (15 mu) ISOCAM filters. Though their global I_nu(6.75 mu)/I_nu(15 mu) flux ratios are similar and typical of normal galaxies, they show distinct trends of this color ratio with mid-infrared surface brightness. We find that I_nu(6.75 mu)/I_nu(15 mu) ~< 1 only occurs for regions of intense heating activity where the continuum rises at 15 micron and where PAH destruction can play an important role. The shape of the color-surface brightness trend also appears to depend, to the second-order, on the hardness of the ionizing radiation. We discuss these findings in the context of a two-component model for the phases of the interstellar medium and suggest that star formation intensity is largely responsible for the mid-infrared surface brightness and colors within normal galaxies, whereas differences in dust column density are the primary drivers of variations in the mid-infrared surface brightness between the disks of normal galaxies.
Seeking the Local Convergence Depth. The Abell Cluster Dipole Flow to 200 Mpc/h
Daniel A. Dale,Riccardo Giovanelli,Martha P. Haynes,Luis E. Campusano,Eduardo Hardy,Stefano Borgani
Physics , 1998, DOI: 10.1086/311800
Abstract: We have obtained new Tully-Fisher (TF) peculiar velocity measurements for 52 Abell galaxy clusters distributed throughout the sky between ~ 50 and 200 Mpc/h.The measurements are based on I band photometry and optical rotation curves for a sample of 522 spiral galaxies, from which an accurate TF template relation has been constructed. Individual cluster TF relations are referred to the template to compute cluster peculiar motions. The reflex motion of the Local Group of galaxies is measured with respect to the reference frame defined by our cluster sample and the distant portion of the Giovanelli et al. (1998) cluster set. We find the Local Group motion in this frame to be 565+/-113 km/s in the direction (l,b)=(267,26)+/-10 when peculiar velocities are weighted according to their errors. After optimizing the dipole calculation to sample equal volumes equally, the vector is 509+/-195 km/s towards (255,33)+/-22. Both solutions agree, to within 1-sigma or better, with the Local Group motion as inferred from the cosmic microwave background (CMB) dipole. Thus, the cluster sample as a whole moves slowly in the CMB reference frame, its bulk flow being at most 200 km/s.
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