A study of ultraviolet absorption lines through the complete Galactic halo by the analysis of HST faint object spectrograph spectra of active Galactic nuclei, 1

Burks, G. S.; Bartko, F.; Shull, J. M.; Stocke, John T.; Sachs, Elise R.; Burbidge, E. M.; Cohen, R. D.; Junkkarinen, V. T.; Harms, R. J.; Massa, Derck

doi:10.1086/175027

Cited by 8 publications

(4 citation statements)

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“…As stated previously, several of these clouds do not conform to a simple infall model and may represent Galactic fountain material. The 3C 273 O vi wing is consistent with a Galactic fountain , since the sight line passes near Galactic Radio Loops I and IV of the North Polar Spur (Burks et al 1994). The PKS 1302À102 HVC is also detected only in O vi and lies $20 from 3C 273.…”

Section: à2mentioning

confidence: 61%

“…The highvelocity O vi toward 3C 273 is a positive-velocity wing to Galactic absorption and can be explained as cooling gas from a Galactic fountain or SNR radio shells (Burks et al 1994). The PKS 1302À102 high-velocity O vi absorption is well separated from the Galactic component; one possible interpretation is that it traces a low-z filament of the WHIM.…”

Section: Ion Detections In Highly Ionized Hvcsmentioning

confidence: 95%

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Highly Ionized High‐Velocity Clouds: Hot Intergalactic Medium or Galactic Halo?

Collins¹,

Shull²,

Giroux³

2005

ApJ

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We use spectroscopic data from the Hubble Space Telescope (HST ) and Far Ultraviolet Spectroscopic Explorer (FUSE ) to study the wide range of ionization states of the ''highly ionized high-velocity clouds'' (HVCs). Studied extensively in O vi absorption, these clouds are usually assumed to be infalling gas in the Galactic halo at distances less than 50 kpc. An alternative model attributes the O vi (and O vii X-ray absorption) to cosmological structures of low-density, shock-heated intergalactic gas, distributed over 1-3 Mpc surrounding the Milky Way. The latter interpretation is unlikely, owing to the enormous required mass of gas (4 ; 10 12 M ). Our detection, in 9 of 12 sight lines, of low-ionization stages (C ii/iii /iv; Si ii/iii /iv) at similar high velocities as O vi requires gas densities far above that (n H % 5 ; 10 À6 cm À3) associated with the warm-hot intergalactic medium (WHIM). These HVCs are probably cooling, multiphase gas in the Galactic halo, bow shocks, and interfaces between clouds falling through a hot, rotating gaseous halo. The velocity segregation of these HVCs in Galactic coordinates is consistent with a pattern in which infalling clouds reflect the sense of Galactic rotation, with peculiar velocities superposed.

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Section: à2mentioning

confidence: 61%

Section: Ion Detections In Highly Ionized Hvcsmentioning

confidence: 95%

Highly Ionized High‐Velocity Clouds: Hot Intergalactic Medium or Galactic Halo?

Collins¹,

Shull²,

Giroux³

2005

ApJ

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“…The dashed vertical line at −1,200 km s −1 indicates our blueward radial velocity limit for determining which Lyα features are intrinsic or "associated" with the target. As discussed in Sembach & Savage (1996) and Burks et al (1994), the sightline towards 3C 273 passes through the edges of Galactic radio loops I and IV near the North Polar Spur (l, b)=(290 • , 64.4 • ) and near the Sagittarius spiral arm. Although no HVCs are reported in this direction, we do detect Galactic N V λ1238, S II λλ1250, 1253, 1259, and Si II λ1260.4 + Fe II λ1260.5 at infalling velocities up to 50 km s −1 .…”

Section: C 273mentioning

confidence: 83%

The Local Lyα Forest. I. Observations with the GHRS/G160M on the Hubble Space Telescope

Penton

Stocke

Shull

2000

ASTROPHYS J SUPPL S

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We present the target selection, observations, and data reduction and analysis process for a program aimed at discovering numerous, weak (equivalent width ≤ 100 mÅ) Lyα absorption lines in the local Universe (0.003 ≤ z ≤ 0.069). The purpose of this program is to study the physical conditions of the local intergalactic medium, including absorber distributions in Doppler width and H I column density, redshift evolution of absorber number density, line-of-sight two-point correlation function, and the baryonic content and metallicity. By making use of large-angle, nearby galaxy redshift surveys, we will investigate the relationship (if any) between these Lyα absorbers and galaxies, superclusters and voids. In Paper I, we present high resolution (∼ 19 km s −1 ) spectroscopic observations of 15 very bright (V ≤ 14.5) AGN targets made with the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope (HST). We find 81 definite (≥ 4σ) and 30 possible (3 − 4σ) Lyα absorption lines in these spectra, which probe a total pathlength of 116,000 km s −1 (∆z ∼ 0.4) at very low redshift (z ≤ 0.069) and column density (12.5 ≤ log N HI ≤ 14.5). We found numerous metal lines arising in the Milky Way halo, including absorption from high velocity clouds in 10 of 15 sightlines and numerous absorptions intrinsic to the target AGN. Here, we describe the details of the target selection, HST observations, and spectral reduction and analysis. We present reduced spectra, absorption line lists, "pie diagrams" showing the known galaxy distributions in the direction of each target, and nearest galaxy tables for each absorber. In Papers II and III, we use the data presented here to determine the basic physical characteristics of the low-z Lyα forest and to investigate the relationship of the absorbers to the local galaxy distribution.

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“…The 3C 273 sight line (l = 289.95 • , b = +64.36 • , z QSO = 0.1583) is one of the best studied directions in the sky at ultraviolet wavelengths. It has been the subject of numerous spectroscopic investigations encompassing studies of the ionization, kinematics, and chemical composition of the Milky Way interstellar medium (ISM; York et al 1984;Burks et al 1991Burks et al , 1994Savage et al 1993;Sembach, Savage, & Tripp 1997), the content and evolution of the intergalactic medium (IGM; Morris et al 1991;Bahcall et al 1991Bahcall et al , 1993Brandt et al 1993Brandt et al , 1997Weymann et al 1995;Hurwitz et al 1998;Penton, Shull, & Stocke 2000;Penton, Stocke, & Shull 2000), and the relationship of the intergalactic Lyα absorption features to galaxies (e.g., Morris et al 1993;). The sight line contains 18 intergalactic Lyα gas clouds at redshifts z = 0.00338−0.14560.…”

Section: Introductionmentioning

confidence: 99%

Far‐Ultraviolet Spectroscopy of the Intergalactic and Interstellar Absorption toward 3C 273

Sembach

Howk

Savage

et al. 2001

ApJ

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148

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We present Far Ultraviolet Spectroscopic Explorer observations of the molecular, neutral atomic, weakly ionized, and highly ionized components of the interstellar and intergalactic material toward the quasar 3C 273. We identify Lyβ absorption in 8 of the known intergalactic Lyα absorbers along the sight line with rest-frame equivalent widths W r (Lyα) 50 mÅ. Refined estimates of the H I column densities and Doppler parameters (b) of the clouds are presented. We find a range of b ≈ 16 − 46 km s −1 . We detect multiple H I lines (Lyβ -Lyθ) in the 1590 km s −1 Virgo absorber and estimate log N (H I) = 15.85± 0.10 0.08 , ten times more H I than all of the other absorbers along the sight line combined. The Doppler width of this absorber, b ≈ 16 km s −1 , implies T 15, 000 K. We detect O VI absorption at 1015 km s −1 at the 2 − 3σ level that may be associated with hot, X-ray emitting gas in the Virgo Cluster. We detect weak C III and O VI absorption in the IGM at z = 0.12007; this absorber is predominantly ionized and has N(H + )/N(H I) ≥ 4000 Z −1 , where Z is the metallicity.Strong Galactic interstellar O VI is present between −100 and +100 km s −1 , with an additional high-velocity wing containing about 13% of the total O VI between ∼ +100 and ∼ +240 km s −1 . The Galactic O VI, N V, and C IV lines have similar shapes, with roughly constant ratios across the -100 to +100 km s −1 velocity range. The high velocity O VI wing is not detected in other species. Much of the interstellar high ion absorption probably occurs within a highly fragmented medium within the Loop IV remnant or in the outer cavity walls of the remnant. Multiple hot gas production mechanisms are required. The broad O VI absorption wing likely traces the expulsion of hot gas out of the Galactic disk into the halo. A flux limit of 5.4×10 −16 erg cm −2 s −1 on the amount of diffuse O VI emission present ∼ 3.5 ′ off the 3C 273 sight line combined with the observed -2 -O VI column density toward 3C 273, log N(O VI) = 14.73± 0.04, implies n e 0.02 cm −3 and P/k 11, 500 cm −3 K for an assumed temperature of 3 × 10 5 K. The elemental abundances in the neutral and weakly-ionized interstellar clouds are similar to those found for other halo clouds. The warm neutral and warm ionized clouds along the sight line have similar dust-phase abundances, implying that the properties of the dust grains in the two types of clouds are similar. Interstellar H 2 absorption is present at positive velocities at a level of log N (H 2 ) ∼ 15.71, but is very weak at the velocities of the main column density concentration along the sight line observed in H I 21 cm emission.

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A study of ultraviolet absorption lines through the complete Galactic halo by the analysis of HST faint object spectrograph spectra of active Galactic nuclei, 1

Cited by 8 publications

References 0 publications

Highly Ionized High‐Velocity Clouds: Hot Intergalactic Medium or Galactic Halo?

Highly Ionized High‐Velocity Clouds: Hot Intergalactic Medium or Galactic Halo?

The Local Lyα Forest. I. Observations with the GHRS/G160M on the Hubble Space Telescope

Far‐Ultraviolet Spectroscopy of the Intergalactic and Interstellar Absorption toward 3C 273

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