Distance limits to intermediate- and high-velocity clouds

Abstract

We present optical spectra of 403 stars and quasi-stellar objects in order to obtain distance limits towards intermediate- and high-velocity clouds (IHVCs), including new Fibre-fed Extended Range Optical Spectrograph (FEROS) observations plus archival ELODIE, FEROS, High Resolution Echelle Spectrometer (HIRES) and Ultraviolet and Visual Echelle Spectrograph (UVES) data. The non-detection of Caii K interstellar (IS) absorption at a velocity of -130 to -60kms-1 towards HDE248894 (d~ 3kpc) and HDE256725 (d~ 8kpc) in data at signal-to-noise ratio (S/N) > 450 provides a new firm lower distance limit of 8kpc for the anti-centre shell HVC. Similarly, the non-detection of Caii K IS absorption towards HD86248 at S/N ~ 500 places a lower distance limit of 7.6kpc for Complex EP, unsurprising since this feature is probably related to the Magellanic System. The lack of detection of Nai D at S/N = 35 towards Mrk595 puts an improved upper limit for the Nai column density of log(NNaD