INTERGALACTIC MEDIUM EMISSION OBSERVATIONS WITH THE COSMIC WEB IMAGER. I. THE CIRCUM-QSO MEDIUM OF QSO 1549+19, AND EVIDENCE FOR A FILAMENTARY GAS INFLOW

Abstract

The Palomar Cosmic Web Imager (PCWI), an integral field spectrograph designed\nto detect and map low surface brightness emission, has obtained imaging\nspectroscopic maps of Ly-alpha from the circum-QSO medium (CQM) of QSO\nHS1549+19 at redshift of 2.843. Extensive extended emission is detected from\nthe CQM, consistent with fluorescent and pumped Ly-alpha produced by the\nionizing and Ly-alpha continuum of the QSO. Many features present in PCWI\nspectral images match those detected in narrow-band images. Filamentary\nstructures with narrow line profiles are detected in several cases as long as\n250-400 kpc. One of these is centered at a velocity redshifted with respect to\nthe systemic velocity, and displays a spatially collimated and kinematically\ncold line profile increasing in velocity width approaching the QSO. This\nsuggests that the filament gas is infalling onto the QSO, perhaps in a cold\naccretion flow. Because of the strong ionizing flux, the neutral column density\nis low, typically N(HI) is roughly 10E12-10E15/square-cm, and the line center\noptical depth is also low (typically tau0 is less than 10), insufficient to\ndisplay well-separated double peak emission characteristic of higher line\noptical depths. With a simple ionization and cloud model we can very roughly\nestimate the total gas mass (log M(gas) equal to 12.5 +/- 0.5) and the total\nmass (log M(tot) equal to 13.3+/- 0.5). We can also calculate a kinematic mass\nfrom the total line profile (2x10E13 M(sun)), which agrees with the mass\nestimated from the gas emission. The intensity-binned spectrum of the CQM shows\na progression in kinematic properties consistent with heirarchical structure\nformation.\n