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Articles 1 - 15 of 15
Full-Text Articles in Physical Sciences and Mathematics
Non-Isobaric Thermal Instability, Tim Waters, Daniel Proga
Non-Isobaric Thermal Instability, Tim Waters, Daniel Proga
Physics & Astronomy Faculty Research
Multiphase media have very complex structure and evolution. Accurate numerical simulations are necessary to make advances in our understanding of this rich physics. Because simulations can capture both the linear and nonlinear evolution of perturbations with a relatively wide range of sizes, it is important to thoroughly understand the stability of condensation and acoustic modes between the two extreme wavelength limits of isobaric and isochoric instability as identified by Field. Partially motivated by a recent suggestion that large non-isobaric clouds can "shatter" into tiny cloudlets, we revisit the linear theory to survey all possible regimes of thermal instability. We uncover …
Narrow Na And K Absorption Lines Toward T Tauri Stars: Tracing The Atomic Envelope Of Molecular Clouds, I. Pascucci, Suzan Edwards, M Heyer, E. Rigliaco, L. Hillenbrand, U. Gorti, D. Hollenbach, M. N. Simon
Narrow Na And K Absorption Lines Toward T Tauri Stars: Tracing The Atomic Envelope Of Molecular Clouds, I. Pascucci, Suzan Edwards, M Heyer, E. Rigliaco, L. Hillenbrand, U. Gorti, D. Hollenbach, M. N. Simon
Astronomy: Faculty Publications
We present a detailed analysis of narrow Na I and K I absorption resonance lines toward nearly 40 T Tauri stars in Taurus with the goal of clarifying their origin. The Na I λ5889.95 line is detected toward all but one source, while the weaker K I λ7698.96 line is detected in about two-thirds of the sample. The similarity in their peak centroids and the significant positive correlation between their equivalent widths demonstrate that these transitions trace the same atomic gas. The absorption lines are present toward both disk and diskless young stellar objects, which excludes cold gas within the …
A Spitzer View Of The Giant Molecular Cloud Mon Ob1/Ngc 2264, Valerie A. Rapson, Judith L. Pipher, R. A. Gutermuth, Megeatj S. Thomas, Thomas S. Allen, Phillip C. Myers, Lori E. Allen
A Spitzer View Of The Giant Molecular Cloud Mon Ob1/Ngc 2264, Valerie A. Rapson, Judith L. Pipher, R. A. Gutermuth, Megeatj S. Thomas, Thomas S. Allen, Phillip C. Myers, Lori E. Allen
Robert A. Gutermuth
We present Spitzer 3.6, 4.5, 5.8, 8.0, and 24 μm images of the Mon OB1 East giant molecular cloud, which contains the young star forming region NGC 2264, as well as more extended star formation. With Spitzer data and Two Micron All Sky Survey photometry, we identify and classify young stellar objects (YSOs) with dusty circumstellar disks and/or envelopes in Mon OB1 East by their infrared-excess emission and study their distribution with respect to cloud material. We find a correlation between the local surface density of YSOs and column density of molecular gas as traced by dust extinction that is …
The Spitzer Survey Of Interstellar Clouds In The Gould Belt. Vi. The Auriga-California Molecular Cloud Observed With Irac And Mips, Hannah Broekhoven-Fiene, Brenda C. Matthews, Paul M. Harvey, R. A. Gutermuth, Tracy L. Huard, Nicholas F.H. Tothill, David Nutter, Tyler L. Bourke, James Difrancesco, Jes K. Jorgensen, Lori E. Allen, Nicholas L. Chapman, Michael M. Dunham, Bruno Merin, Jennifer Miller, Susan Terebey, Dawn E. Peterson, Karl R. Stapelfeldt
The Spitzer Survey Of Interstellar Clouds In The Gould Belt. Vi. The Auriga-California Molecular Cloud Observed With Irac And Mips, Hannah Broekhoven-Fiene, Brenda C. Matthews, Paul M. Harvey, R. A. Gutermuth, Tracy L. Huard, Nicholas F.H. Tothill, David Nutter, Tyler L. Bourke, James Difrancesco, Jes K. Jorgensen, Lori E. Allen, Nicholas L. Chapman, Michael M. Dunham, Bruno Merin, Jennifer Miller, Susan Terebey, Dawn E. Peterson, Karl R. Stapelfeldt
Robert A. Gutermuth
We present observations of the Auriga-California Molecular Cloud (AMC) at 3.6, 4.5, 5.8, 8.0, 24, 70, and 160 μm observed with the IRAC and MIPS detectors as part of the Spitzer Gould Belt Legacy Survey. The total mapped areas are 2.5 deg2 with IRAC and 10.47 deg2 with MIPS. This giant molecular cloud is one of two in the nearby Gould Belt of star-forming regions, the other being the Orion A Molecular Cloud (OMC). We compare source counts, colors, and magnitudes in our observed region to a subset of the SWIRE data that was processed through our pipeline. Using color-magnitude …
Core Formation In Partially Ionized Magnetic Molecular Clouds, Nicole D. Bailey
Core Formation In Partially Ionized Magnetic Molecular Clouds, Nicole D. Bailey
Electronic Thesis and Dissertation Repository
Linear analysis of the formation of protostellar cores in planar magnetic interstellar clouds shows that molecular clouds exhibit a preferred length scale for collapse that depends on the mass-to-flux ratio and neutral-ion collision time within the cloud. This linear analysis can be used to investigate the formation of star forming clusters and the distribution of mass within star forming regions. By combining the results of the linear analysis with a realistic ionization profile for the cloud, we find that a molecular cloud may evolve through two fragmentation events in the evolution toward the formation of stars. Our model suggests that …
Co Abundance Variations In The Orion Molecular Cloud, F. Ripple, M.H. Heyer, R. A. Gutermuth, R.L. Snell, C.M. Brunt
Co Abundance Variations In The Orion Molecular Cloud, F. Ripple, M.H. Heyer, R. A. Gutermuth, R.L. Snell, C.M. Brunt
Robert A. Gutermuth
Infrared stellar photometry from the Two Micron All-Sky Survey (2MASS) and spectral line imaging observations of 12CO and 13CO J = 1–0 line emission from the Five College Radio Astronomy Observatory (FCRAO) 14-m telescope are analysed to assess the variation of the CO abundance with physical conditions throughout the Orion A and Orion B molecular clouds. Three distinct Av regimes are identified in which the ratio between the 13CO column density and visual extinction changes corresponding to the photon-dominated envelope, the strongly self-shielded interior, and the cold, dense volumes of the clouds. Within the strongly self-shielded interior of the Orion …
Magnetic Diffusion In Star Formation: From Clouds To Cores To Stars To Disks, Wolfgang B. Dapp
Magnetic Diffusion In Star Formation: From Clouds To Cores To Stars To Disks, Wolfgang B. Dapp
Electronic Thesis and Dissertation Repository
We investigate magnetic diffusion on scales from molecular clouds over prestellar and
protostellar cores down to young stellar objects (YSOs) and their surrounding protoplanetary disk.
In Chapter 2, we present thin-sheet simulations that exhibit long-lived magnetic-tension-driven oscillations, founded in the interaction of the cloud's magnetic field with that anchored in an external medium. In contrast with "local" simulations in a periodic box, where turbulence decays away in approximately a sound crossing time, and needs to be continually replenished by driving, our simulation has "global" aspects, and retains some kinetic energy indefinitely. We provide an analytical explanation for these modes, that …
The Herschel M33 Extended Survey (Herm33es): Pacs Spectroscopy Of The Star Forming Region Bclmp 302, B. Mookerjea, C. Kramer, C. Buchbender, M. Boquien, S. Verley, M. Relaño, G. Quintana-Lacaci, S. Aalto, J. Braine, Daniela Calzetti, F. Combes, S. Garcia-Burillo, P. Gratier, C. Henkel, F. Israel, S. Lord, T. Nikola, M. Rölling, G. Stacey, F. S. Tabatabaei, F. Van Der Tak, P. Van Der Werf
The Herschel M33 Extended Survey (Herm33es): Pacs Spectroscopy Of The Star Forming Region Bclmp 302, B. Mookerjea, C. Kramer, C. Buchbender, M. Boquien, S. Verley, M. Relaño, G. Quintana-Lacaci, S. Aalto, J. Braine, Daniela Calzetti, F. Combes, S. Garcia-Burillo, P. Gratier, C. Henkel, F. Israel, S. Lord, T. Nikola, M. Rölling, G. Stacey, F. S. Tabatabaei, F. Van Der Tak, P. Van Der Werf
Daniela Calzetti
Context: The emission line of [CII] at 158 micron is one of the strongest cooling lines of the interstellar medium (ISM) in galaxies. Aims: Disentangling the relative contributions of the different ISM phases to [CII] emission, is a major topic of the HerM33es program, a Herschel key project to study the ISM in the nearby spiral galaxy M33. Methods: Using PACS, we have mapped the emission of [CII] 158 micron, [OI] 63 micron, and other FIR lines in a 2'x2' region of the northern spiral arm of M33, centered on the HII region BCLMP302. At the peak of H-alpha emission, …
Molecular Outflows From The Protocluster, Serpens South, Fumitaka Nakamura, Koji Sugitani, Yoshito Shimajiri, Takashi Tsukagoshi, Aya E. Higuchi, Shogo Nishiyama, Ryohei Kawabe, Michihiro Takami, Jennifer L. Karr, Robert A. Gutermuth, Grant Wilson
Molecular Outflows From The Protocluster, Serpens South, Fumitaka Nakamura, Koji Sugitani, Yoshito Shimajiri, Takashi Tsukagoshi, Aya E. Higuchi, Shogo Nishiyama, Ryohei Kawabe, Michihiro Takami, Jennifer L. Karr, Robert A. Gutermuth, Grant Wilson
Grant Wilson
We present the results of CO ($J=3-2$) and HCO$^+$ ($J=4-3$) mapping observations toward a nearby embedded cluster, Serpens South, using the ASTE 10 m telescope. Our CO ($J=3-2$) map reveals that many outflows are crowded in the dense cluster-forming clump that can be recognized as a HCO$^+$ clump with a size of $\sim$ 0.2 pc and mass of $\sim$ 80 M$_\odot$. The clump contains several subfragments with sizes of $\sim$ 0.05 pc. By comparing the CO ($J=3-2$) map with the 1.1 mm dust continuum image taken by AzTEC on ASTE, we find that the spatial extents of the outflow lobes …
A Search For Dust Emission In The Leo Intergalactic Cloud, Caroline Bot, George Helou, William B. Latter, Jérémie Puget, Stephen Schneider, Yervant Terzian
A Search For Dust Emission In The Leo Intergalactic Cloud, Caroline Bot, George Helou, William B. Latter, Jérémie Puget, Stephen Schneider, Yervant Terzian
Astronomy Department Faculty Publication Series
We present a search for infrared dust emission associated with the Leo cloud, a large intergalactic cloud in the M96 group. Mid-infrared and far-infrared images were obtained with the InfraRed Array Camera and the Multiband Imaging Photometer for Spitzer on the Spitzer Space Telescope. Our analysis of these maps is done at each wavelength relative to the H i spatial distribution. We observe a probable detection at 8 μm and a marginal detection at 24 μm associated with the highest H i column densities in the cloud. At 70 and 160 μm, upper limits on the dust emission are …
The Five College Radio Astronomy Observatory Co Mapping Survey Of The Taurus Molecular Cloud, Gopal Narayanan, Mark H. Heyer, Christopher Brunt, Paul F. Goldsmith, Ronald Snell, Di Li
The Five College Radio Astronomy Observatory Co Mapping Survey Of The Taurus Molecular Cloud, Gopal Narayanan, Mark H. Heyer, Christopher Brunt, Paul F. Goldsmith, Ronald Snell, Di Li
Gopal Narayanan
The FCRAO Survey of the Taurus molecular cloud observed the 12CO and 13CO J = 1–0 emission from 98 deg2 of this important, nearby, star-forming region. This set of data with 45'' resolution comprises the highest spatial dynamic range image of an individual molecular cloud constructed to date and provides valuable insights to the molecular gas distribution, kinematics, and the star formation process. In this contribution, we describe the observations, calibration, data processing, and characteristics of the noise and line emission of the survey. The angular distribution of 12CO and 13CO emission over 1 km s−1 velocity intervals and the …
A Three‐Dimensional Numerical Method For Modelling Weakly Ionized Plasmas, Stephen O'Sullivan, Turlough Downes
A Three‐Dimensional Numerical Method For Modelling Weakly Ionized Plasmas, Stephen O'Sullivan, Turlough Downes
Articles
Astrophysical fluids under the influence of magnetic fields are often subjected to single- or two-fluid approximations. In the case of weakly ionized plasmas, however, this can be inappropriate due to distinct responses from the multiple constituent species to both collisional and non-collisional forces. As a result, in dense molecular clouds and protostellar accretion discs, for instance, the conductivity of the plasma may be highly anisotropic leading to phenomena such as Hall and ambipolar diffusion strongly influencing the dynamics.
An Explicit Scheme For Multifluid Magnetohydrodynamics, Stephen O'Sullivan, Turlough Downes
An Explicit Scheme For Multifluid Magnetohydrodynamics, Stephen O'Sullivan, Turlough Downes
Articles
When modelling astrophysical fluid flows, it is often appropriate to discard the canonical magnetohydrodynamic approximation, thereby freeing the magnetic field to diffuse with respect to the bulk velocity field. As a consequence, however, the induction equation can become problematic to solve via standard explicit techniques. In particular, the Hall diffusion term admits fast-moving whistler waves which can impose a vanishing time-step limit.Within an explicit differencing framework, a multifluid scheme for weakly ionized plasmas is presented which relies upon a new approach to integrating the induction equation efficiently. The first component of this approach is a relatively unknown method of accelerating …
Complex C: A Low-Metallicity High-Velocity Cloud Plunging Into The Milky Way, Todd M. Tripp, Bart P. Wakker, Edward B. Jenkins, C. W. Bowers, A. C. Danks, R. F. Green, S. R. Heap, C. L. Joseph, M. E. Kaiser, J. L. Linsky, B. E. Woodgate
Complex C: A Low-Metallicity High-Velocity Cloud Plunging Into The Milky Way, Todd M. Tripp, Bart P. Wakker, Edward B. Jenkins, C. W. Bowers, A. C. Danks, R. F. Green, S. R. Heap, C. L. Joseph, M. E. Kaiser, J. L. Linsky, B. E. Woodgate
Todd M. Tripp
We present evidence that high-velocity cloud (HVC) complex C is a low-metallicity gas cloud that is plunging toward the disk and beginning to interact with the ambient gas that surrounds the Milky Way. This evidence begins with a new high-resolution (7 km s-1 FWHM) echelle spectrum of 3C 351 obtained with the Space Telescope Imaging Spectrograph (STIS). 3C 351 lies behind the low-latitude edge of complex C, and the new spectrum provides accurate measurements of O I, Si II, Al II, Fe II, and Si III absorption lines at the velocity of complex C; N I, S II, Si IV, …
Star Formation In Bright Rimmed Clouds. I. Millimeter And Submillimeter Molecular Line Surveys, Christopher H. De Vries, Gopal Narayanan, Ronald L. Snell
Star Formation In Bright Rimmed Clouds. I. Millimeter And Submillimeter Molecular Line Surveys, Christopher H. De Vries, Gopal Narayanan, Ronald L. Snell
Gopal Narayanan
We present the results of the first detailed millimeter and submillimeter molecular line survey of bright-rimmed clouds, observed at FCRAO in the CO (J = 1 ? 0), C18O (J = 1 ? 0), HCO+ (J = 1 ? 0), H13CO+ (J = 1 ? 0), and N2H+ (J = 1 ? 0) transitions, and at the Heinrich Hertz Telescope in the CO (J = 2 ? 1), HCO+ (J = 3 ? 2), HCO+ (J = 4 ? 3), H13CO+ (J = 3 ? 2), and H13CO+ (J = 4 ? 3) molecular line transitions. The source list is …