Publications (64)82.48 Total impact
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Article: Unresolved H-Alpha Enhancements at High Galactic Latitude in the WHAM Sky Survey Maps
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ABSTRACT: We have identified 85 regions of enhanced H-Alpha emission at |b| > 10 degrees subtending approximately 1 degree or less on the Wisconsin H-Alpha Mapper (WHAM) sky survey. These high latitude ``WHAM point sources'' have H-Alpha fluxes of 10^{-11} to 10^{-9} erg cm^-2 s^-1, radial velocities within about 70 km/s of the LSR, and line widths that range from less than 20 km/s to about 80 km/s (FWHM). Twenty nine of these enhancements are not identified with either cataloged nebulae or hot stars and appear to have kinematic properties that differ from those observed for planetary nebulae. Another 14 enhancements are near hot evolved low mass stars that had no previously reported detections of associated nebulosity. The remainder of the enhancements are cataloged planetary nebulae and small, high latitude H II regions surrounding massive O and early B stars. Comment: 22 pages, 8 figures, 2 tables, to appear in Feb. 2005 AJ11/2004; -
Article: New Measurements of the Motion of the Zodiacal Dust
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ABSTRACT: Using the Wisconsin H-Alpha Mapper (WHAM), we have measured at high spectral resolution and high signal-to-noise the profile of the scattered solar Mg I 5184 absorption line in the zodiacal light. The observations were carried out toward 49 directions that sampled the ecliptic equator from solar elongations of 48\dg (evening sky) to 334\dg (morning sky) plus observations near +47\dg and +90\dg ecliptic latitude. The spectra show a clear prograde kinematic signature that is inconsistent with dust confined to the ecliptic plane and in circular orbits influenced only by the sun's gravity. In particular, the broadened widths of the profiles, together with large amplitude variations in the centroid velocity with elongation angle, indicate that a significant population of dust is on eccentric orbits. In addition, the wide, flat-bottomed line profile toward the ecliptic pole indicates a broad distribution of orbital inclinations extending up to about 30\dg - 40\dg with respect to the ecliptic plane. The absence of pronounced asymmetries in the shape of the profiles limits the retrograde population to less than 10% of the prograde population and also places constraints on the scattering phase function of the particles. These results do not show the radial outflow or evening--morning velocity amplitude asymmetry reported in some earlier investigations. The reduction of the spectra included the discovery and removal of extremely faint, unidentified terrestrial emission lines that contaminate and distort the underlying Mg I profile. This atmospheric emission is too weak to have been seen in earlier, lower signal-to-noise observations, but it probably affected the line centroid measurements of previous investigations. Comment: 24 pages, 8 figures, 1 table, to appear in ApJ v612; figures appear low-res only on screen05/2004; -
Article: The Wisconsin H-Alpha Mapper Northern Sky Survey
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ABSTRACT: The Wisconsin H-Alpha Mapper (WHAM) has surveyed the distribution and kinematics of ionized gas in the Galaxy above declination -30 degrees. The WHAM Northern Sky Survey (WHAM-NSS) has an angular resolution of one degree and provides the first absolutely-calibrated, kinematically-resolved map of the H-Alpha emission from the Warm Ionized Medium (WIM) within ~ +/-100 km/s of the Local Standard of Rest. Leveraging WHAM's 12 km/s spectral resolution, we have modeled and removed atmospheric emission and zodiacal absorption features from each of the 37,565 spectra. The resulting H-Alpha profiles reveal ionized gas detected in nearly every direction on the sky with a sensitivity of 0.15 R (3 sigma). Complex distributions of ionized gas are revealed in the nearby spiral arms up to 1-2 kpc away from the Galactic plane. Toward the inner Galaxy, the WHAM-NSS provides information about the WIM out to the tangent point down to a few degrees from the plane. Ionized gas is also detected toward many intermediate velocity clouds at high latitudes. Several new H II regions are revealed around early B-stars and evolved stellar cores (sdB/O). This work presents the details of the instrument, the survey, and the data reduction techniques. The WHAM-NSS is also presented and analyzed for its gross properties. Finally, some general conclusions are presented about the nature of the WIM as revealed by the WHAM-NSS. Comment: 42 pages, 14 figures (Fig 6-9 & 14 are full color); accepted for publication in 2003, ApJ, 149; Original quality figures (as well as data for the survey) are available at http://www.astro.wisc.edu/wham/09/2003; -
Article: A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies
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ABSTRACT: 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. Comment: 10 pages, 2 figures, AASTeX two-column format. Accepted for publication in The Astrophysical Journal01/2003; -
Article: WHAM Observations of H-alpha from High-Velocity Clouds: Are They Galactic or Extragalactic?
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ABSTRACT: It has been suggested that high velocity clouds may be distributed throughout the Local Group and are therefore not in general associated with the Milky Way galaxy. With the aim of testing this hypothesis, we have made observations in the H-alpha line of high velocity clouds selected as the most likely candidates for being at larger than average distances. We have found H-alpha emission from 4 out of 5 of the observed clouds, suggesting that the clouds under study are being illuminated by a Lyman continuum flux greater than that of the metagalactic ionizing radiation. Therefore, it appears likely that these clouds are in the Galactic halo and not distributed throughout the Local Group. Comment: 12 pages, 5 eps figures, accepted for publication in ApJ Letters06/2002; -
Article: Three-Dimensional Studies of the Warm Ionized Medium in the Milky Way using WHAM
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ABSTRACT: The Wisconsin H-Alpha Mapper (WHAM) is a high throughput Fabry-Perot facility developed specifically to detect and explore the warm, ionized component of the interstellar medium at high spectral resolution. It began operating at Kitt Peak, Arizona in 1997 and has recently completed the WHAM Northern Sky Survey (WHAM-NSS), providing the first global view of the distribution and kinematics of the warm, diffuse H II in the Milky Way. This H-alpha survey reveals a complex spatial and kinematic structure in the warm ionized medium and provides a foundation for studies of the temperature and ionization state of the gas, the spectrum and strength of the ionizing radiation, and its relationship to other components of the interstellar medium and sources of ionization and heating within the Galactic disk and halo. More information about WHAM and the Survey can be found at http://www.astro.wisc.edu/wham/.02/2002; -
Article: The Wisconsin H-Alpha Mapper Northern Sky Survey of Galactic Ionized Hydrogen
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ABSTRACT: The Wisconsin H-Alpha Mapper (WHAM) has completed a one-degree resolution, velocity-resolved northern sky survey of H-alpha emission from our Galaxy. The unprecedented sensitivity of the instrument and accurate spectral subtraction of atmospheric features allow us to detect Galactic features as faint as 0.1 Rayleighs (EM ~ 0.25 cm^{-6} pc). This survey allows a direct comparison of the ionized and neutral components of the ISM on a global scale for the first time. All-sky maps of H-alpha emission in select velocity bands highlight the rich kinematic structure of the Galaxy's ionized gas. The full set of data from the WHAM survey is now available at http://www.astro.wisc.edu/wham/. (abridged)01/2002; -
Article: WHAM Observations of Halpha from High-Velocity Clouds: Are They Galactic or Extragalactic?
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ABSTRACT: It has been suggested that high-velocity clouds may be distributed throughout the Local Group and are therefore not in general associated with the Milky Way. With the aim of testing this hypothesis, we have made observations in the Halpha line of high-velocity clouds selected as the most likely candidates for being at larger than average distances. We have found Halpha emission from four out of five of the observed clouds, suggesting that the clouds under study are being illuminated by a Lyman continuum flux greater than that of the metagalactic ionizing radiation. Therefore, it appears likely that these clouds are in the Galactic halo and not distributed throughout the Local Group.Astrophysical Journal - ASTROPHYS J. 01/2002; 572. -
Article: Interstellar H-Alpha Line Profiles toward HD 93521 and the Lockman Window
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ABSTRACT: We have used the Wisconsin H-Alpha Mapper (WHAM) facility to measure the interstellar H-Alpha emission toward the high Galactic latitude O star HD 93521 (l = 183.1, b = +62.2). Three emission components were detected having radial velocities of -10 km s^{-1}, -51 km s^{-1}, and -90 km s^{-1} with respect to the local standard of rest (LSR) and H-Alpha intensities of 0.20 R, 0.15 R, and 0.023 R, respectively, corresponding to emission measures of 0.55 cm^{-6} pc, 0.42 cm^{-6} pc, and 0.06 cm^{-6} pc. We have also detected an H-Alpha emission component at -1 km s^{-1} (LSR) with an intensity of 0.20 R (0.55 cm^{-6} pc) toward the direction l = 148.5, b = +53.0, which lies in the region of exceptionally low H I column density known as the Lockman Window. In addition, we studied the direction l = 163.5, b = +53.5. Upper limits on the possible intensity of Galactic emission toward this direction are 0.11 R at the LSR and 0.06 R at -50 km s^{-1}. We also detected and characterized twelve faint (~0.03-0.15 R), unidentified atmospheric lines present in WHAM H-Alpha spectra. Lastly, we have used WHAM to obtain [O I] 6300 spectra along the line of sight toward HD 93521. We place an upper limit of 0.060 R on the [O I] intensity of the -51 km s^{-1} component. If the temperature of the gas is 10,000 K within the H-Alpha emitting region, the hydrogen ionization fraction n(H+)/n(H_total) > 0.6. Comment: 23 pages, 4 figures. Acccepted for publication in the 1 Feb issue of The Astronomical Journal12/2001; -
Article: Observations of the Extended Distribution of Ionized Hydrogen in the Plane of M31
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ABSTRACT: We have used the Wisconsin H-Alpha Mapper (WHAM) to observe the spatially extended distribution of ionized hydrogen in M31 beyond the stellar disk. We obtained five sets of observations, centered near the photometric major axis of M31, that extend from the center of the galaxy to just off the edge of the southwestern HI disk. Beyond the bright stellar disk, but within the HI disk, weak H-alpha is detected with an intensity I(H-alpha) = 0.05 (+0.01 / -0.02) Rayleighs. Since M31 is inclined 77 degrees with respect to the line of sight, this implies that the ambient intergalactic ionizing flux onto each side of M31 is Phi_0 <= 1.6 x 10^4 photons cm^-2 s^-1. Just beyond the outer boundary of the HI disk we find no significant detection of H-alpha and place an upper limit I(H-alpha) <= 0.019 Rayleighs. Comment: To appear in ApJ Letters; 12 pages, 4 figures09/2001; -
Article: A Map Of The Ionized Component Of The Intermediate-Velocity Cloud Complex K
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ABSTRACT: The Wisconsin H-Alpha Mapper (WHAM) Northern Sky Survey is revealing that many intermediate-velocity (kms #1 ) neutral clouds and complexes have an associated ionized component. We present the first Fv F # 100 LSR map of the Ha emission from an intermediate- or high-velocity structure: Complex K. This large, high-latitude feature stretches from to 70#,to#70# and peaks in velocity over to #80 km s #1 . l # 10# b # #30# v # #60 LSR The neutral and ionized gas generally trace each other quite well in the complex, but the detailed structure is not identical. In particular, the Ha emission peaks in brightness at slightly higher Galactic longitudes than corresponding 21 cm features. The ionized gas has a peak Ha intensity of 0.5 R, corresponding to an emission measure of 1.1 cm #6 pc. Structures in the complex are traced by WHAM down to about 0.1 R (0.2 cm #6 pc). Typical line widths of the Ha emission are #30 km s #1 , limiting temperatures in the ionized gas to less than 20,000 K. If radiation is the primary ionizing mechanism, the Lyman continuum flux required to sustain the most strongly emitting ionized regions is photons cm #2 s #1 . There appears to be no local, stellar source 6 1.2 # 10 capable of maintaining the ionization of the gas; however, the required ionizing flux is consistent with current models of the escape of Lyman continuum radiation from OB stars in the disk and of ionizing radiation produced by cooling supernova remnants. Subject headings: Galaxy: halo --- H ii regions --- ISM: atoms --- ISM: clouds --- ISM: individual (IVC K) --- ISM: structure 1.08/2001; -
Article: Detection of a Large Arc of Ionized Hydrogen Far Above the Cas OB6 Association: A Superbubble Blowout into the Galactic Halo?
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ABSTRACT: The Wisconsin H-Alpha Mapper (WHAM) Northern Sky Survey has revealed a loop of H II reaching 1300 pc from the Galactic midplane above the Cas OB6 association in the Perseus sprial arm. This enormous feature surrounds and extends far above the "W4 Chimney" identified by Normandeau et al. and appears to be associated with the star formation activity near the W3/W4/W5 H II region complex. The existence of this ionized structure suggests that past episodes of massive star formation have cleared the H I from an enormous volume above the Perseus arm, allowing Lyman continuum photons from O stars near the Galactic midplane to reach into the halo. Comment: 12 pages, 2 figures, accepted for publication in ApJ (Letters)08/2001; -
Article: Detection of [N II] 5755 Emission from Low Density Ionized Interstellar Gas
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ABSTRACT: The extremely faint, temperature sensitive ``auroral'' emission line [N II] 5755 has been detected from the low density ionized gas along the sight line toward l = 130.0, b = -7.5 using the Wisconsin H-Alpha Mapper (WHAM). The intensity of this emission line, relative to the red nebular line [N II] 6584, is found to be twice that observed in bright, classical H II regions surrounding O stars. This implies that the electron temperature of the ionized gas along this sight line is about 2000 K higher than the H II regions, and that the enhanced [N II] 6584/H-Alpha and [S II] 6716/H-Alpha intensity ratios in this low density gas are due at least in part to an elevated temperature. Comment: 9 pages, 2 figures; Accepted for publication by ApJ Letters01/2001; -
Article: Mapping the Galactic Free-Free Foreground via Interstellar H-Alpha Emission
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ABSTRACT: Recently completed H-Alpha surveys of large portions of the sky can be used to create maps of the free-free intensity distribution at high Galactic latitude that are independent of the spectral fits to the CMB data. This provides an opportunity to test the accuracy of the spectral fitting procedures and to search for other sources of Galactic forground contamination that could be confused spectrally with the free-free, such as spinning dust grains. The Wisconsin H-Alpha Mapper (WHAM) survey has sampled the sky north of declination -30 deg at about one degree angular resolution and has revealed that, except for a few isolated regions of enhanced emission, \Delta T_{ff} (30 GHz) < 30 micro-K at Galactic latitudes near 15 deg, decreasing to \Delta T_{ff} (30 GHz) < 4 mircro-K at latitudes above 50 deg. Also in progress are H-Alpha surveys that sample the sky at higher angular resolution.11/2000; -
Article: The Wisconsin Halpha Mapper: A New Look At The Warm Ionized Medium
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ABSTRACT: The Wisconsin H-Alpha Mapper (WHAM) has surveyed the entire northern sky in H# from Kitt Peak, Arizona. Using a high-throughput, 15-cm diameter double-etalon Fabry-Perot spectrometer and a sensitive CCD detector, the WHAM survey provides the first calibrated, velocity-resolved map of H# emission in our Galaxy. A large portion of the Galaxy, which samples regions of the Local (Orion) spiral arm and the more distant Perseus arm, has been also been observed with the WHAM in lines of [S II] and [N II]. These new data directly probe the physical conditions of the Warm Ionized Medium (WIM) on a global scale for the first time. Trends in these line ratios over this large region of the sky suggest that temperature variations are traced by the [N II]/H# and [S II]/H# maps. Since these ratios increase dramatically away from the Galactic plane, they reveal a substantial temperature rise in WIM halo gas. In addition to this striking new result, the data set also reveals new information...11/2000; -
Article: RevMexAA (Serie de Conferencias), 9, 238-245 (2000)
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ABSTRACT: The Wisconsin H-Alpha Mapper (WHAM) has surveyed the entire northern sky in H from Kitt Peak, Arizona. Using a high-throughput, 15-cm diameter double-etalon Fabry-Perot spectrometer and a sensitive CCD detector, the WHAM survey provides the rst calibrated, velocity-resolved map of H emission in our Galaxy. A large portion of the Galaxy, which samples regions of the Local (Orion) spiral arm and the more distant Perseus arm, has been also been observed with the WHAM in lines of [S II] and [N II]. These new data directly probe the physical conditions of the Warm Ionized Medium (WIM) on a global scale for the rst time. Trends in these line ratios over this large region of the sky suggest that temperature variations are traced by the [N II]/H and [S II]/H maps. Since these ratios increase dramatically away from the Galactic plane, they reveal a substantial temperature rise in WIM halo gas. In addition to this striking new result, the data set also reveals new information about the ionization in the WIM through the [S II]/[N II] ratio, uncovers a previously undiscovered B-star H II region, and provides an accurate measurement of the electron scale height of the WIM.06/2000; -
Article: RevMexAA (Serie de Conferencias), 9, 249-255 (2000)
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ABSTRACT: Optical emission lines observed in the gaseous halo of the Milky Way and other galaxies suggest the existence of a supplemental heat source|in addition to photoionization|that increases the electron temperature in regions of low density. Such heat sources are in fact predicted to exit in the interstellar medium. For example, both the dissipation of turbulence through ion-neutral dampening and photoelectric heating by small grains could heat the warm ionized medium in the Milky Way at the rate of about 10 . If such a source were present, it would dominate over photoionization heating in regions where n e < 0.1 , producing the observed increases in the [S II]/H and [N II]/H intensity ratios at large distances from the Galactic midplane. Magnetic reconnection and Coulomb collisions by cosmic rays are other potential sources. This heating rate would also account for the emission line ratio variations observed in NGC 891, including the increase in [O III] 5007/H with distance from the midplane, which cannot be explained by pure photoionization models.06/2000; -
Article: The extragalactic background and its fluctuations in the far-infrared wavelengths
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ABSTRACT: A Cosmic Far-InfraRed Background (CFIRB) has long been predicted that would traces the intial phases of galaxy formation. It has been first detected by Puget et al.(1996) using COBE data and has been later confirmed by several recent studies (Fixsen et al. 1998, Hauser et al. 1998, Lagache et al. 1999). We will present a new determination of the CFIRB that uses for the first time, in addition to COBE data, two independent gas tracers: the HI survey of Leiden/Dwingeloo (hartmann, 1998) and the WHAM H$_{\alpha}$ survey (Reynolds et al 1998). We will see that the CFIRB above 100 micron is now very well constrained. The next step is to see if we can detect its fluctuations. To search for the CFIRB fluctuations, we have used the FIRBACK observations. FIRBACK is a deep cosmological survey conducted at 170 micron with ISOPHOT (Dole et al., 2000). We show that the emission of unresolved extra-galactic sources clearly dominates, at arcminute scales, the background fluctuations in the lowest galactic emission regions. This is the first detection of the CFIRB fluctuations.03/2000; -
Article: The wisconsin Ha mapper: a new look at the warm ionized medium
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ABSTRACT: The Wisconsin H-Alpha Mapper (WHAM) has surveyed the entire northern sky in H from Kitt Peak, Arizona. Using a high-throughput, 15-cm diameter double-etalon Fabry-Perot spectrometer and a sensitive CCD detector, the WHAM survey provides the rst calibrated, velocity-resolved map of H emission in our Galaxy. A large portion of the Galaxy, which samples regions of the Local (Orion) spiral arm and the more distant Perseus arm, has been also been observed with the WHAM in lines of [S II] and [N II]. These new data directly probe the physical conditions of the Warm Ionized Medium (WIM) on a global scale for the rst time. Trends in these line ratios over this large region of the sky suggest that temperature variations are traced by the [N II]/H and [S II]/H maps. Since these ratios increase dramatically away from the Galactic plane, they reveal a substantial temperature rise in WIM halo gas. In addition to this striking new result, the data set also reveals new information about the ionization in the WIM through the [S II]/[N II] ratio, uncovers a previously undiscovered B-star H II region, and provides an accurate measurement of the electron scale height of the WIM.Revista Mexicana de Astronomía y Astrofísica. 01/2000; -
Article: Temperature variations and non-photoionization heating in the warm ionized medium of galaxies
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ABSTRACT: Optical emission lines observed in the gaseous halo of the Milky Way and other galaxies suggest the existence of a supplemental heat source|in addition to photoionization|that increases the electron temperature in regions of low density. Such heat sources are in fact predicted to exit in the interstellar medium. For example, both the dissipation of turbulence through ion-neutral dampening and photoelectric heating by small grains could heat the warm ionized medium in the Milky Way at the rate of about 10Revista Mexicana de Astronomía y Astrofísica. 01/2000;
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Institutions
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1989–2010
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University of Wisconsin, Madison
- Department of Astronomy
Madison, MS, USA
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2005
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University of St Andrews
- School of Physics and Astronomy
Saint Andrews, SCT, United Kingdom
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