HI 21cm imaging of a nearby Damped Lyman-alpha system

Abstract

We present Giant Metrewave Radio Telescope (GMRT) HI 21cm emission images of the z=0.009 damped Lyman-alpha (DLA) absorber towards the QSO HS 1543+5921. The DLA has been earlier identified as a low surface brightness galaxy SBS 1543+593 at an impact parameter of ~ 400 pc to the QSO line of sight. The extremely low redshift of the absorber allows us to make spatially resolved images of the 21cm emission; besides the HI mass, this also enables us to determine the velocity field of the galaxy and, hence, to estimate its dynamical mass. We obtain a total HI mass of ~ 1.4x10^9 Msun, considerably smaller than the value of M*(HI) determined from blind 21cm emission surveys. This continues the trend of low HI mass in all low redshift DLAs for which HI emission observations have been attempted. We also find that the QSO lies behind a region of low local HI column density in the foreground galaxy. This is interesting in view of suggestions that DLA samples are biased against high HI column density systems. The dynamical mass of the galaxy is found to be Mdyn ~ 5x10^9 Msun.

Accepted for publication in A&A

References in corpus (5)

• The CORALS Survey I: New Estimates of the Number Density and Gas Content of Damped Lyman Alpha Systems Free from Dust Bias
• Implications of 21cm observations for damped Ly-$\alpha$ systems
• HI 21cm absorption in low z damped lyman-alpha systems
• ATCA search for 21 cm emission from a candidate damped Ly-$\alpha$ absorber at z = 0.101
• 21-cm H I emission from the Damped Lyman-alpha absorber SBS 1543+593

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