The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Tammy A. Smecker-hane - One of the best experts on this subject based on the ideXlab platform.
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A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies
The Astrophysical Journal, 2003Co-Authors: J. S. Gallagher, Ronald J. Reynolds, G. J. Madsen, Eva K. Grebel, Tammy A. Smecker-haneAbstract:The Wisconsin Hα Mapper has been used to set the first deep upper limits on the intensity of diffuse Hα emission from warm Ionized Gas in the Draco and Ursa Minor dwarf spheroidal galaxies (dSphs). Assuming a velocity dispersion of 15 km s-1 for the Ionized Gas, we set limits of IHα ≤ 0.024 R and IHα ≤ 0.021 R for the Draco and Ursa Minor dSphs, respectively, averaged over our 1° circular beam. Adopting a simple model for the Ionized interstellar medium, these limits translate to upper bounds on the mass of Ionized Gas of 10% of the stellar mass, or ~10 times the upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa Minor dSphs could contain substantial amounts of interstellar Gas, equivalent to all of the Gas injected by dying stars since the end of their main star-forming episodes 8 Gyr in the past, without violating these limits on the mass of Ionized Gas.
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A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies
The Astrophysical Journal, 2003Co-Authors: J. S. Gallagher, Ronald J. Reynolds, G. J. Madsen, Eva K. Grebel, Tammy A. Smecker-haneAbstract:The Wisconsin H Alpha Mapper has been used to set the first deep upper limits on the intensity of diffuse H alpha emission from warm Ionized Gas in the Local Group dwarf spheroidal galaxies (dSphs) Draco and Ursa Minor. Assuming a velocity dispersion of 15 km/s for the Ionized Gas, we set limits for the H alpha intensity of less or equal to 0.024 Rayleighs and less or equal to 0.021 Rayleighs for the Draco and Ursa Minor dSphs, respectively, averaged over our 1 degree circular beam. Adopting a simple model for the Ionized interstellar medium, these limits translate to upper bounds on the mass of Ionized Gas of approximately less than 10% of the stellar mass, or approximately 10 times the upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa Minor dSphs could contain substantial amounts of interstellar Gas, equivalent to all of the Gas injected by dying stars since the end of their main star forming episodes more than 8 Gyr in the past, without violating these limits on the mass of Ionized Gas.
J. S. Gallagher - One of the best experts on this subject based on the ideXlab platform.
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A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies
The Astrophysical Journal, 2003Co-Authors: J. S. Gallagher, Ronald J. Reynolds, G. J. Madsen, Eva K. Grebel, Tammy A. Smecker-haneAbstract:The Wisconsin Hα Mapper has been used to set the first deep upper limits on the intensity of diffuse Hα emission from warm Ionized Gas in the Draco and Ursa Minor dwarf spheroidal galaxies (dSphs). Assuming a velocity dispersion of 15 km s-1 for the Ionized Gas, we set limits of IHα ≤ 0.024 R and IHα ≤ 0.021 R for the Draco and Ursa Minor dSphs, respectively, averaged over our 1° circular beam. Adopting a simple model for the Ionized interstellar medium, these limits translate to upper bounds on the mass of Ionized Gas of 10% of the stellar mass, or ~10 times the upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa Minor dSphs could contain substantial amounts of interstellar Gas, equivalent to all of the Gas injected by dying stars since the end of their main star-forming episodes 8 Gyr in the past, without violating these limits on the mass of Ionized Gas.
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A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies
The Astrophysical Journal, 2003Co-Authors: J. S. Gallagher, Ronald J. Reynolds, G. J. Madsen, Eva K. Grebel, Tammy A. Smecker-haneAbstract:The Wisconsin H Alpha Mapper has been used to set the first deep upper limits on the intensity of diffuse H alpha emission from warm Ionized Gas in the Local Group dwarf spheroidal galaxies (dSphs) Draco and Ursa Minor. Assuming a velocity dispersion of 15 km/s for the Ionized Gas, we set limits for the H alpha intensity of less or equal to 0.024 Rayleighs and less or equal to 0.021 Rayleighs for the Draco and Ursa Minor dSphs, respectively, averaged over our 1 degree circular beam. Adopting a simple model for the Ionized interstellar medium, these limits translate to upper bounds on the mass of Ionized Gas of approximately less than 10% of the stellar mass, or approximately 10 times the upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa Minor dSphs could contain substantial amounts of interstellar Gas, equivalent to all of the Gas injected by dying stars since the end of their main star forming episodes more than 8 Gyr in the past, without violating these limits on the mass of Ionized Gas.
G. J. Madsen - One of the best experts on this subject based on the ideXlab platform.
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A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies
The Astrophysical Journal, 2003Co-Authors: J. S. Gallagher, Ronald J. Reynolds, G. J. Madsen, Eva K. Grebel, Tammy A. Smecker-haneAbstract:The Wisconsin Hα Mapper has been used to set the first deep upper limits on the intensity of diffuse Hα emission from warm Ionized Gas in the Draco and Ursa Minor dwarf spheroidal galaxies (dSphs). Assuming a velocity dispersion of 15 km s-1 for the Ionized Gas, we set limits of IHα ≤ 0.024 R and IHα ≤ 0.021 R for the Draco and Ursa Minor dSphs, respectively, averaged over our 1° circular beam. Adopting a simple model for the Ionized interstellar medium, these limits translate to upper bounds on the mass of Ionized Gas of 10% of the stellar mass, or ~10 times the upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa Minor dSphs could contain substantial amounts of interstellar Gas, equivalent to all of the Gas injected by dying stars since the end of their main star-forming episodes 8 Gyr in the past, without violating these limits on the mass of Ionized Gas.
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A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies
The Astrophysical Journal, 2003Co-Authors: J. S. Gallagher, Ronald J. Reynolds, G. J. Madsen, Eva K. Grebel, Tammy A. Smecker-haneAbstract:The Wisconsin H Alpha Mapper has been used to set the first deep upper limits on the intensity of diffuse H alpha emission from warm Ionized Gas in the Local Group dwarf spheroidal galaxies (dSphs) Draco and Ursa Minor. Assuming a velocity dispersion of 15 km/s for the Ionized Gas, we set limits for the H alpha intensity of less or equal to 0.024 Rayleighs and less or equal to 0.021 Rayleighs for the Draco and Ursa Minor dSphs, respectively, averaged over our 1 degree circular beam. Adopting a simple model for the Ionized interstellar medium, these limits translate to upper bounds on the mass of Ionized Gas of approximately less than 10% of the stellar mass, or approximately 10 times the upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa Minor dSphs could contain substantial amounts of interstellar Gas, equivalent to all of the Gas injected by dying stars since the end of their main star forming episodes more than 8 Gyr in the past, without violating these limits on the mass of Ionized Gas.
Eva K. Grebel - One of the best experts on this subject based on the ideXlab platform.
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A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies
The Astrophysical Journal, 2003Co-Authors: J. S. Gallagher, Ronald J. Reynolds, G. J. Madsen, Eva K. Grebel, Tammy A. Smecker-haneAbstract:The Wisconsin Hα Mapper has been used to set the first deep upper limits on the intensity of diffuse Hα emission from warm Ionized Gas in the Draco and Ursa Minor dwarf spheroidal galaxies (dSphs). Assuming a velocity dispersion of 15 km s-1 for the Ionized Gas, we set limits of IHα ≤ 0.024 R and IHα ≤ 0.021 R for the Draco and Ursa Minor dSphs, respectively, averaged over our 1° circular beam. Adopting a simple model for the Ionized interstellar medium, these limits translate to upper bounds on the mass of Ionized Gas of 10% of the stellar mass, or ~10 times the upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa Minor dSphs could contain substantial amounts of interstellar Gas, equivalent to all of the Gas injected by dying stars since the end of their main star-forming episodes 8 Gyr in the past, without violating these limits on the mass of Ionized Gas.
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A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies
The Astrophysical Journal, 2003Co-Authors: J. S. Gallagher, Ronald J. Reynolds, G. J. Madsen, Eva K. Grebel, Tammy A. Smecker-haneAbstract:The Wisconsin H Alpha Mapper has been used to set the first deep upper limits on the intensity of diffuse H alpha emission from warm Ionized Gas in the Local Group dwarf spheroidal galaxies (dSphs) Draco and Ursa Minor. Assuming a velocity dispersion of 15 km/s for the Ionized Gas, we set limits for the H alpha intensity of less or equal to 0.024 Rayleighs and less or equal to 0.021 Rayleighs for the Draco and Ursa Minor dSphs, respectively, averaged over our 1 degree circular beam. Adopting a simple model for the Ionized interstellar medium, these limits translate to upper bounds on the mass of Ionized Gas of approximately less than 10% of the stellar mass, or approximately 10 times the upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa Minor dSphs could contain substantial amounts of interstellar Gas, equivalent to all of the Gas injected by dying stars since the end of their main star forming episodes more than 8 Gyr in the past, without violating these limits on the mass of Ionized Gas.
Robert A Benjamin - One of the best experts on this subject based on the ideXlab platform.
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testing a dynamical equilibrium model of the extraplanar diffuse Ionized Gas in ngc 891
The Astrophysical Journal, 2016Co-Authors: Erin Boettcher, Ellen G Zweibel, J S Gallagher, Robert A BenjaminAbstract:The observed scale heights of extraplanar diffuse Ionized Gas (eDIG) layers exceed their thermal scale heights by a factor of a few in the Milky Way and other nearby edge-on disk galaxies. Here, we test a dynamical equilibrium model of the extraplanar diffuse Ionized Gas layer in NGC 891, where we ask whether the thermal, turbulent, magnetic field, and cosmic ray pressure gradients are sufficient to support the layer. In optical emission line spectroscopy from the SparsePak integral field unit on the WIYN 3.5-meter telescope, the H-alpha emission in position-velocity space suggests that the eDIG is found in a ring between galactocentric radii of R_min = 2 kpc. We find that the thermal (sigma_th = 11 km/s) and turbulent (sigma_turb = 25 km/s) velocity dispersions are insufficient to satisfy the hydrostatic equilibrium equation given an exponential electron scale height of h_z = 1.0 kpc. Using a literature analysis of radio continuum observations from the CHANG-ES survey, we demonstrate that the magnetic field and cosmic ray pressure gradients are sufficient to stably support the Gas at R >= 8 kpc if the cosmic rays are sufficiently coupled to the system (gamma_cr = 1.45). Thus, a stable dynamical equilibrium model is viable only if the extraplanar diffuse Ionized Gas is found in a thin ring around R = 8 kpc, and non-equilibrium models such as a galactic fountain flow are of interest for further study.
