%0 Generic %1 muzahid2016molecular %A Muzahid, Sowgat %A Kacprzak, Glenn G. %A Charlton, Jane C. %A Churchill, Christopher W. %D 2016 %K absorption galaxy gas halos molecular %T Molecular Hydrogen Absorption from the Halo of a z~0.4 Galaxy %U http://arxiv.org/abs/1601.06782 %X Lyman- and Werner-band absorption of molecular hydrogen (H2) is detected in ~50% of low redshift (z<1) DLAs/sub-DLAs with N(H2)>10^14.4 cm^-2. However the true origin(s) of the H2 bearing gas remain elusive. Here we report a new detection of an H2 absorber at z = 0.4298 in the HST/COS spectra of quasar PKS~2128--123. The total N(HI) of 10^19.50\pm0.15 cm^-2 classifies the absorber as a sub-DLA. H2 absorption is detected up to the J=3 rotational level with a total log N(H2)=16.36\pm0.08 corresponding to a molecular fraction of log f(H2)=-2.84\pm0.17. The excitation temperature of T_ex = 206\pm6K indicates the presence of cold gas. Using detailed ionization modelling we obtain a near-solar metallicity (i.e., O/H= -0.26\pm0.19) and a dust-to-gas ratio of log ~ -0.45 for the H2 absorbing gas. The host-galaxy of the sub-DLA is detected at an impact parameter of ~ 48 kpc with an inclination angle of i~48 degree and an azimuthal angle of \Phi ~ 15 degree with respect to the QSO sightline. We show that co-rotating gas in an extended disk cannot explain the observed kinematics of MgII absorption. Moreover, the inferred high metallicity is not consistent with the scenario of gas accretion. An outflow from the central region of the host-galaxy, on the other hand, would require a large opening angle (i.e., 2$þeta>$150\degree), much larger than the observed outflow opening angles in Seyfert galaxies, in order to intercept the QSO sightline. We thus favor a scenario in which the H2 bearing gas is stemming from a dwarf-satellite galaxy, presumably via tidal and/or ram-pressure stripping. Detection of a dwarf galaxy candidate in the HST/WFPC2 image at an impact parameter of ~12 kpc reinforces such an idea.

@misc{muzahid2016molecular, abstract = {Lyman- and Werner-band absorption of molecular hydrogen (H2) is detected in ~50% of low redshift (z<1) DLAs/sub-DLAs with N(H2)>10^14.4 cm^-2. However the true origin(s) of the H2 bearing gas remain elusive. Here we report a new detection of an H2 absorber at z = 0.4298 in the HST/COS spectra of quasar PKS~2128--123. The total N(HI) of 10^{19.50\pm0.15} cm^-2 classifies the absorber as a sub-DLA. H2 absorption is detected up to the J=3 rotational level with a total log N(H2)=16.36\pm0.08 corresponding to a molecular fraction of log f(H2)=-2.84\pm0.17. The excitation temperature of T_ex = 206\pm6K indicates the presence of cold gas. Using detailed ionization modelling we obtain a near-solar metallicity (i.e., [O/H]= -0.26\pm0.19) and a dust-to-gas ratio of log \kappa ~ -0.45 for the H2 absorbing gas. The host-galaxy of the sub-DLA is detected at an impact parameter of \rho ~ 48 kpc with an inclination angle of i~48 degree and an azimuthal angle of \Phi ~ 15 degree with respect to the QSO sightline. We show that co-rotating gas in an extended disk cannot explain the observed kinematics of MgII absorption. Moreover, the inferred high metallicity is not consistent with the scenario of gas accretion. An outflow from the central region of the host-galaxy, on the other hand, would require a large opening angle (i.e., 2$\theta>$150\degree), much larger than the observed outflow opening angles in Seyfert galaxies, in order to intercept the QSO sightline. We thus favor a scenario in which the H2 bearing gas is stemming from a dwarf-satellite galaxy, presumably via tidal and/or ram-pressure stripping. Detection of a dwarf galaxy candidate in the HST/WFPC2 image at an impact parameter of ~12 kpc reinforces such an idea.}, added-at = {2016-01-27T12:30:21.000+0100}, author = {Muzahid, Sowgat and Kacprzak, Glenn G. and Charlton, Jane C. and Churchill, Christopher W.}, biburl = {https://www.bibsonomy.org/bibtex/2375ecceb91b448980c5c995bc33d23a9/miki}, description = {[1601.06782] Molecular Hydrogen Absorption from the Halo of a z~0.4 Galaxy}, interhash = {655ce409f47c222178774d56bde0c320}, intrahash = {375ecceb91b448980c5c995bc33d23a9}, keywords = {absorption galaxy gas halos molecular}, note = {cite arxiv:1601.06782Comment: 15 pages, Submitted to APJ, Comments Welcome!}, timestamp = {2016-01-27T12:30:21.000+0100}, title = {Molecular Hydrogen Absorption from the Halo of a z~0.4 Galaxy}, url = {http://arxiv.org/abs/1601.06782}, year = 2016 }