We use a background quasar to detect the presence of circumgalactic gas around a z = 0.91 low-mass star-forming galaxy .
Data from the new Multi Unit Spectroscopic Explorer ( MUSE ) on the Very Large Telescope show that the galaxy has a dust-corrected star formation rate ( SFR ) of 4.7 \pm 2.0 M _ { \odot } yr ^ { -1 } , with no companion down to 0.22 M _ { \odot } yr ^ { -1 } ( 5 \sigma ) within 240 h ^ { -1 } kpc ( 30″ ) .
Using a high-resolution spectrum ( UVES ) of the background quasar , which is fortuitously aligned with the galaxy major axis ( with an azimuth angle \alpha of only 15 ^ { \circ } ) , we find , in the gas kinematics traced by low-ionization lines , distinct signatures consistent with those expected for a “ cold-flow disk ” extending at least 12 kpc ( 3 \times R _ { 1 / 2 } ) .
We estimate the mass accretion rate \dot { M } _ { in } to be at least two to three times larger than the SFR , using the geometric constraints from the IFU data and the H i column density of \log N _ { \textsc { h \scriptsize { i } } } / \hbox { cm$ { } ^ { -2 } $ } \simeq 20.4 obtained from a Hubble Space Telescope /COS near-UV spectrum .
From a detailed analysis of the low-ionization lines ( e.g .
Zn ii , Cr ii , Ti ii , Mn ii , Si ii ) , the accreting material appears to be enriched to about 0.4 Z _ { \odot } ( albeit with large uncertainties : \log Z / Z _ { \odot } = -0.4 ~ { } \pm~ { } 0.4 ) , which is comparable to the galaxy metallicity ( 12 + \log O / H = 8.7 \pm 0.2 ) implying a large recycling fraction from past outflows .
Blueshifted Mg ii and Fe ii absorptions in the galaxy spectrum from the MUSE data reveals the presence of an outflow .
The Mg ii and Fe ii doublet ratios indicate emission infilling due to scattering processes , but the MUSE data do not show any signs of fluorescent Fe ii * emission .