Deep Hubble Space Telescope Imaging on the Extended Ly$\hat{I}\pm$ Emission of a QSO at $z=2.19$ with Damped Lyman Alpha System as a Natural Coronagraph

Abstract

Recent observations suggest that proximate damped Ly$\hat{I}\pm$ (PDLA) systems can be used to study the host galaxies of Quasi-stellar objects (QSOs), because the PDLAs can block the bright point-spread-function (PSF) from central QSOs. Using six-orbits of narrowband imaging with $HST$/WFC3, we present the first high resolution narrowband image of the Ly$\hat{I}\pm$ emission in the PDLA trough of the QSO SDSSJ115432.67-021537.9 . We detect one major component and one minor component in the narrowband imaging. Combining the $HST$/WFC3 imaging with deep Magellan/MagE spectra, we measure that the Ly$\hat{I}\pm$ flux F${}_{\mathrm{Ly}\hat{\mathrm{I}}\pm }$ = 1.56$\pm 0.10\times 10^{-16}$ $\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{c}{\mathrm{m}}^{-2}$, which is among the luminous ($\approx$ 2.7 L${}_{\mathrm{Ly}\hat{\mathrm{I}}\pm }^{\star }$) Ly$\hat{I}\pm$ emitters at $z=$ 2.19. The $\mathrm{Ly}\hat{\mathrm{I}}\pm$-based star formation rate (SFR) is $\sim$ 7 $\textrm{M_{\sun} \ yr^{-1}}$. These observational results favor that the star formation from the host galaxy could be the main mechanism to power the Ly$\hat{I}\pm$ emission. This new method sheds new light on the study of the kinematic structure and the spatial distribution of the extended Ly$\hat{I}\pm$ emitting regions around the QSO host.