A survey of H I absorption at low latitudes

Dickey, John M.; Kulkarni, S. R.; Heiles, Carl; Gorkom, J. H. van

doi:10.1086/190903

Cited by 57 publications

(71 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…All of the spectra show the presence of a strong absorption feature near 5 km s~1, a slight curvature resulting from the absence of a bandpass correction, and a typical rms determined outside the H I line of p q B 0.012. Our absorption spectra are in good agreement with those found by Dickey et al (1983).…”

Section: Observations and Analysissupporting

confidence: 91%

“…are sensitive to H I emission on angular scales much larger than any structures plausibly responsible for the ESE itself. The emission spectra we obtain are in generally good agreement with those found by Dickey et al (1983) using the NRAO 90 m telescope : the peak emission occurs near 5 km s~1, and the emission is skewed toward positive velocities. The width of the emission line from our spectrum and the brightness temperature of the line are larger than those found by Dickey et al (1983) owing to the smaller diameter antenna in our case (25 m vs. 90 m).…”

Section: Observations and Analysissupporting

confidence: 87%

“…The emission spectra we obtain are in generally good agreement with those found by Dickey et al (1983) using the NRAO 90 m telescope : the peak emission occurs near 5 km s~1, and the emission is skewed toward positive velocities. The width of the emission line from our spectrum and the brightness temperature of the line are larger than those found by Dickey et al (1983) owing to the smaller diameter antenna in our case (25 m vs. 90 m). Because we are searching for changes in an absorption line with time, we discuss in detail the steps we took to calibrate these observations.…”

Section: Observations and Analysissupporting

confidence: 87%

“…The maximum optical depth for all four of our epochs also di †ers from previous observations by Dickey et al (1983), and Dickey & Benson q max B 1, (1982), Dickey & Benson (1982) observed q max B 3. 1741[038 using an interferometer composed of the NRAO 140 foot and 300 foot telescopes in 1980 and 1981.…”

Section: Ine Changescontrasting

confidence: 71%

“…1741[038 using an interferometer composed of the NRAO 140 foot and 300 foot telescopes in 1980 and 1981. Dickey et al (1983) observed 1741[038 using the phased VLA in 1982. There is some danger in comparing observations from di †erent telescopes, and the large optical depth found by Dickey & Benson (1982) has a large uncertainty associated with it.…”

Section: Ine Changesmentioning

confidence: 99%

See 4 more Smart Citations

The Extreme Scattering Event toward 1741−038: HiAbsorption

Lazio¹,

Gaume²,

Claussen³

et al. 2001

ApJ

View full text Add to dashboard Cite

We report multi-epoch Very Large Array H I absorption observations of the source 1741[038 (OT [068) before and during an extreme scattering event (ESE). Observations at four epochs, three during the ESE, were obtained. We Ðnd no changes in the equivalent width, maximum optical depth, or velocity of maximum optical depth during the ESE, but we do Ðnd a secular trend of decreasing maximum optical depth between our observations and ones by other observers a decade prior. The resulting limit on the H I column density change during the ESE for a structure with a spin temperature is 6.4 ] 1017 T s K). Tiny-scale atomic structures (TSAS), with cm~2, are ruled out marginally cm~2(T s /10 N H D 3 ] 1018 by this limit, though geometric arguments may allow this limit to be relaxed. Galactic halo molecular clouds that are opaque in the H I line cannot be excluded from causing the ESE because the observed velocity range covers only 25% of their allowed velocity range.

show abstract

Section: Observations and Analysissupporting

confidence: 91%

Section: Observations and Analysissupporting

confidence: 87%