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Articles 1 - 8 of 8
Full-Text Articles in Physical Sciences and Mathematics
The Relations Among 8, 24 And 160 Mu M Dust Emission Within Nearby Spiral Galaxies, Gj Bendo, Bt Draine, Cw Engelbracht, G Helou, Md Thornley, C Bot, Ba Buckalew, D Calzetti, Da Dale, J Hollenbach, A Li, J Moustakas
The Relations Among 8, 24 And 160 Mu M Dust Emission Within Nearby Spiral Galaxies, Gj Bendo, Bt Draine, Cw Engelbracht, G Helou, Md Thornley, C Bot, Ba Buckalew, D Calzetti, Da Dale, J Hollenbach, A Li, J Moustakas
Astronomy Department Faculty Publication Series
We investigate the relations among the stellar continuum-subtracted 8 μm polycyclic aromatic hydrocarbon (PAH 8 μ m) emission, 24 μm hot dust emission and 160 μm cold dust emission in 15 nearby face-on spiral galaxies in the Spitzer Infrared Nearby Galaxies Survey sample. The relation between PAH 8 and 24 μm emission measured in ∼2 kpc regions is found to exhibit a significant amount of scatter, and strong spatial variations are observed in the (PAH 8 μ m)/24 μm surface brightness ratio. In particular, the (PAH 8 μ m)/24 μm surface brightness ratio is observed to be high in the …
The Opacity Of Spiral Galaxy Disks. Viii. Structure Of The Cold Ism, Bw Holwerda, B Draine, Kd Gordon, Ra Gonzalez, D Calzetti, M Thornley, B Buckalew, Rj Allen, Pc Van Der Kruit
The Opacity Of Spiral Galaxy Disks. Viii. Structure Of The Cold Ism, Bw Holwerda, B Draine, Kd Gordon, Ra Gonzalez, D Calzetti, M Thornley, B Buckalew, Rj Allen, Pc Van Der Kruit
Astronomy Department Faculty Publication Series
The quantity of dust in a spiral disk can be estimated using the dust's typical emission or the extinction of a known source. In this paper we compare two techniques, one based on emission and one on absorption, applied to sections of 14 disk galaxies. The two measurements reflect, respectively, the average and apparent optical depth of a disk section. Hence, they depend differently on the average number and optical depth of ISM structures in the disk. The small-scale geometry of the cold ISM is critical for accurate models of the overall energy budget of spiral disks. ISM geometry, relative …
Warm Molecular Hydrogen In The Spitzer Sings Galaxy Sample, H Roussel, G Helou, Dj Hollenbach, Bt Draine, Jd Smith, L Armus, E Schinnerer, F Walter, Cw Engelbracht, Md Thornley, Rc Kennicutt, D Calzetti, Da Dale, Ej Murphy, C Bot
Warm Molecular Hydrogen In The Spitzer Sings Galaxy Sample, H Roussel, G Helou, Dj Hollenbach, Bt Draine, Jd Smith, L Armus, E Schinnerer, F Walter, Cw Engelbracht, Md Thornley, Rc Kennicutt, D Calzetti, Da Dale, Ej Murphy, C Bot
Astronomy Department Faculty Publication Series
Results on the properties of warm molecular hydrogen in 57 normal galaxies are derived from measurements of H2 rotational transitions, obtained as part of SINGS. This study extends previous extragalactic surveys of emission lines of H2 to fainter and more common systems (LFIR = 107-6 × 1010 L). The 17 μm S(1) transition is securely detected in the nuclear regions of 86% of galaxies with stellar masses above 109.5 M. The derived column densities of warm H2 (T ≥ 100 K), although averaged over kiloparsec-scale areas, are commensurate with values observed in resolved photodissociation regions. They amount to between 1% …
Gaps In The Cloud Cover? Comparing Extinction Measures In Spiral Disks, Bw Holwerda, M Meyer, M Regan, D Calzetti, Kd Gordon, Jd Smith, D Dale, Cw Engelbracht, T Jarrett, M Thornley, C Bot, B Buckalew, Rc Kennicutt, Ra Gonzalez
Gaps In The Cloud Cover? Comparing Extinction Measures In Spiral Disks, Bw Holwerda, M Meyer, M Regan, D Calzetti, Kd Gordon, Jd Smith, D Dale, Cw Engelbracht, T Jarrett, M Thornley, C Bot, B Buckalew, Rc Kennicutt, Ra Gonzalez
Astronomy Department Faculty Publication Series
Dust in galaxies can be mapped either by the FIR/submillimeter emission, the optical or infrared reddening of starlight, or the extinction of a known background source. We compare two dust extinction measurements for a set of 15 sections in 13 nearby galaxies to determine the scale of the dusty interstellar medium (ISM) responsible for disk opacity: one using stellar reddening and the other a known background source. In our earlier papers, we presented extinction measurements of 29 galaxies, based on calibrated counts of distant background objects identified though foreground disks in Hubble Space Telescope WFPC2 images. For the 13 galaxies …
Variations In 24-Mu M Morphologies Among Galaxies In The Spitzer Infrared Nearby Galaxies Survey: New Insights Into The Hubble Sequence, Gj Bendo, D Calzetti, Cw Engelbracht, Rc Kennicutt, Mj Meyer, Md Thornley, F Walter, Da Dale, A Li, Ej Murphy
Variations In 24-Mu M Morphologies Among Galaxies In The Spitzer Infrared Nearby Galaxies Survey: New Insights Into The Hubble Sequence, Gj Bendo, D Calzetti, Cw Engelbracht, Rc Kennicutt, Mj Meyer, Md Thornley, F Walter, Da Dale, A Li, Ej Murphy
Astronomy Department Faculty Publication Series
To study the distribution of star formation and dust emission within nearby galaxies, we measured five morphological parameters in the 3.6- and 24-μm wavebands for 65 galaxies in the Spitzer Infrared Nearby Galaxies Survey (SINGS) and eight galaxies that were serendipitously observed by SINGS. The morphological parameters demonstrate strong variations along the Hubble sequence, including statistically significant differences between S0/a-Sab and Sc-Sd galaxies. Early-type galaxies are generally found to be compact, centralized, symmetric sources in the 24-μm band, while late-type galaxies are generally found to be extended, asymmetric sources. These results suggest that the processes that increase the real or …
Star Formation In Ngc 5194 (M51a). Ii. The Spatially Resolved Star Formation Law, Rc Kennicutt, D Calzetti, F Walter, G Helou, Dj Hollenbach, L Armus, G Bendo, Da Dale, Bt Draine, Cw Engelbracht, Kd Gordon, Mkm Prescott, Mw Regan, Md Thornley, C Bot, E Brinks, E De Blok, D De Mello, M Meyer, J Moustakas, Ej Murphy, K Sheth, Jdt Smith
Star Formation In Ngc 5194 (M51a). Ii. The Spatially Resolved Star Formation Law, Rc Kennicutt, D Calzetti, F Walter, G Helou, Dj Hollenbach, L Armus, G Bendo, Da Dale, Bt Draine, Cw Engelbracht, Kd Gordon, Mkm Prescott, Mw Regan, Md Thornley, C Bot, E Brinks, E De Blok, D De Mello, M Meyer, J Moustakas, Ej Murphy, K Sheth, Jdt Smith
Astronomy Department Faculty Publication Series
We have studied the relationship between the star formation rate (SFR), surface density, and gas surface density in the spiral galaxy M51a (NGC 5194), using multiwavelength data obtained as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS). We introduce a new SFR index based on a linear combination of Hα emission-line and 24 μm continuum luminosities, which provides reliable extinction-corrected ionizing fluxes and SFR densities over a wide range of dust attenuations. The combination of these extinction-corrected SFR densities with aperture synthesis H I and CO maps has allowed us to probe the form of the spatially resolved star …
The Galaxy Angular Correlation Functions And Power Spectrum From The Two Micron All Sky Survey, Ah Maller, Dh Mcintosh, N Katz, Md Weinberg
The Galaxy Angular Correlation Functions And Power Spectrum From The Two Micron All Sky Survey, Ah Maller, Dh Mcintosh, N Katz, Md Weinberg
Astronomy Department Faculty Publication Series
We calculate the angular correlation function of galaxies in the Two Micron All Sky Survey. We minimize the possible contamination by stars, dust, seeing, and sky brightness by studying their cross correlation with galaxy density and limiting the galaxy sample accordingly. We measure the correlation function at scales between 1' < θ < 18° using a half-million galaxies. We find that a best-fit power law to the correlation function has a slope of -0.79 ± 0.02 and an amplitude at 1° of 0.10 ± 0.01 in the range 1'-2fdg5. However, there are statistically significant oscillations around this power law. The largest oscillation occurs at about 0fdg8, corresponding to 700 h-1 kpc at the median redshift of our survey, as expected in halo occupation distribution descriptions of galaxy clustering. In addition, there is a break in the power-law shape of the correlation function at θ > 2fdg5. Our results are in good agreement with other measurements of the angular correlation function. We invert the angular correlation function using singular value decomposition to measure the three-dimensional power spectrum and find that it too is in good agreement with previous measurements. A dip seen in the power spectrum …
The Clustering Dipole Of The Local Universe From The Two Micron All Sky Survey, Ah Maller, Dh Mcintosh, N Katz, Md Weinberg
The Clustering Dipole Of The Local Universe From The Two Micron All Sky Survey, Ah Maller, Dh Mcintosh, N Katz, Md Weinberg
Astronomy Department Faculty Publication Series
The unprecedented sky coverage and photometric uniformity of the Two Micron All Sky Survey (2MASS) provides a rich resource for investigating the galaxies populating the local universe. A full characterization of the large-scale clustering distribution is important for theoretical studies of structure formation. 2MASS offers an all-sky view of the local galaxy population at 2.15 μm, unbiased by young stellar light and minimally affected by dust. We use 2MASS to map the local distribution of galaxies, identifying the largest structures in the nearby universe. The inhomogeneity of these structures causes an acceleration on the Local Group of galaxies, which can …