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Observations towards early-type stars in the ESO-POP survey: II --
searches for intermediate and high velocity clouds | | J. V. Smoker
; I. Hunter
; P. M. W. Kalberla
; F. P. Keenan
; R. Morras
; R. Hanuschik
; H. M. A. Thompson
; D. Silva
; E. Bajaja
; W. G. L. Poppel
; M. Arnal
; | | Date: |
10 Apr 2007 | | Subject: | Astrophysics (astro-ph) | | Abstract: | We present CaII K and TiII optical spectra of early-type stars taken mainly
from the UVES Paranal Observatory Project, plus HI 21-cm spectra from the
Vila-Elisa and Leiden-Dwingeloo surveys, which are employed to obtain distances
to intermediate and high velocity clouds. HI emission at a velocity of -117
km/s towards the sightline HD 30677 with NHI=1.7x10^19 cm-2 has no
corresponding CaII K absorption, which has a signal-to-noise (S/N) ratio of
610. The star has a spectroscopically determined distance of 2.7-kpc, and hence
sets this as a firm lower distance limit towards Anti-Centre cloud ACII.
Towards another sightline (HD 46185), HI at +122 km/s and NHI=1.2x10^19 cm-2 is
seen. The CaII K spectrum has a S/N = 780, although no absorption is observed
at the cloud velocity. This similarly places a firm lower distance limit of
2.9-kpc towards this parcel of gas that may be an intermediate velocity cloud.
The lack of intermediate velocity (IV) CaII K absorption towards HD 196426 at a
S/N = 500 reinforces a lower distance limit of 700-pc towards this part of
Complex gp, where NHI is 1.1x10^19 cm-2 and velocity is +78 km/s. Additionally,
no IV CaII K is seen in absorption in the spectrum of HD 19445, which is strong
in HI with NHI=8x10^19 cm-2 at -42 km/s, placing a firm although uninteresting
lower distance limit of 39-pc to this part of IV South. Finally, no HV CaII K
absorption is seen towards HD 115363 at a S/N = 410, placing a lower distance
of 3.2-kpc towards the HVC gas at velocity of +224 km/s and NHI=5.2x10^19 cm-2.
This gas is in the same region of the sky as complex WE (Wakker 2001), but at
higher velocities. The non-detection of CaII K absorption sets a lower distance
of 3.2-kpc towards the HVC, which is unsurprising if this feature is indeed
related to the Magellanic System. | | Source: | arXiv, arxiv.0704.1315 | | Services: | Forum | Review | PDF | Favorites | |
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