Observations towards early-type stars in the ESO-POP Survey – II. Searches for intermediate- and high-velocity clouds

Abstract

Abstract We present Ca ii K and Ti ii optical spectra of early-type stars taken mainly from the ultraviolet and visual echelle spectrograph (UVES) Paranal Observatory Project, plus H i 21-cm spectra, from the Vila-Elisa and Leiden-Dwingeloo Surveys, which are employed to obtain distances to intermediate- and high-velocity clouds (IHVCs). H i emission at a velocity of −117 km s−1 towards the sightline HD 30677 () with column density ∼1.7 × 1019 cm−2 has no corresponding Ca ii K absorption in the UVES spectrum, which has a signal-to-noise ratio (S/N) of 610 per resolution element. 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 with ), H i at a velocity of +122 km s−1 and column density of 1.2 × 1019 cm−2 is seen. The corresponding Ca ii K spectrum has a S/N of 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 (IV) cloud. The lack of IV Ca ii absorption towards HD 196426 () at a S/N of 500 reinforces a lower distance limit of ∼700 pc towards this part of complex gp, where the H i column density is 1.1 × 1019 cm−2 and velocity is +78 km s−1. Additionally, no IV Ca ii is seen in absorption in the spectrum of HD 19445, which is strong in H i with a column density of 8 × 1019 cm−2 at a velocity of ∼−42 km s−1, placing a firm although uninteresting lower distance limit of 39 pc to this part of IV South. Finally, no high-velocity Ca ii K absorption is seen towards HD 115363 () at a S/N of 410, placing a lower distance of ∼3.2 kpc towards the HVC gas at velocity of ∼+224 km s−1 and H i column density of 5.2 × 1019 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 Ca ii 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.