%0 Generic %1 biggs2016parsecscale %A Biggs, A. D. %A Zwaan, M. A. %A Hatziminaoglou, E. %A Péroux, C. %A Liske, J. %D 2016 %K HI absorption parsec scale %T Parsec-scale HI absorption structure in a low-redshift galaxy seen against a Compact Symmetric Object %U http://arxiv.org/abs/1607.05995 %X We present global VLBI observations of the 21-cm transition of atomic hydrogen seen in absorption against the radio source J0855+5751. The foreground absorber (SDSS~J085519.05+575140.7) is a dwarf galaxy at $z$ = 0.026. As the background source is heavily resolved by VLBI, the data allow us to map the properties of the foreground HI gas with a spatial resolution of 2pc. The absorbing gas corresponds to a single coherent structure with an extent $>$35pc, but we also detect significant and coherent variations, including a change in the HI optical depth by a factor of five across a distance of $łeq$6pc. The large size of the structure provides support for the Heiles & Troland model of the ISM, as well as its applicability to external galaxies. The large variations in HI optical depth also suggest that caution should be applied when interpreting $T_S$ measurements from radio-detected DLAs. In addition, the distorted appearance of the background radio source is indicative of a strong jet-cloud interaction in its host galaxy. We have measured its redshift ($z$ = 0.54186) using optical spectroscopy on the William Herschel Telescope and this confirms that J0855+5751 is a FRII radio source with a physical extent of $<$1kpc and supports the previous identification of this source as a Compact Symmetric Object. These sources often show absorption associated with the host galaxy and we suggest that both HI and OH should be searched for in J0855+5751.

@misc{biggs2016parsecscale, abstract = {We present global VLBI observations of the 21-cm transition of atomic hydrogen seen in absorption against the radio source J0855+5751. The foreground absorber (SDSS~J085519.05+575140.7) is a dwarf galaxy at $z$ = 0.026. As the background source is heavily resolved by VLBI, the data allow us to map the properties of the foreground HI gas with a spatial resolution of 2pc. The absorbing gas corresponds to a single coherent structure with an extent $>$35pc, but we also detect significant and coherent variations, including a change in the HI optical depth by a factor of five across a distance of $\leq$6pc. The large size of the structure provides support for the Heiles & Troland model of the ISM, as well as its applicability to external galaxies. The large variations in HI optical depth also suggest that caution should be applied when interpreting $T_S$ measurements from radio-detected DLAs. In addition, the distorted appearance of the background radio source is indicative of a strong jet-cloud interaction in its host galaxy. We have measured its redshift ($z$ = 0.54186) using optical spectroscopy on the William Herschel Telescope and this confirms that J0855+5751 is a FRII radio source with a physical extent of $<$1kpc and supports the previous identification of this source as a Compact Symmetric Object. These sources often show absorption associated with the host galaxy and we suggest that both HI and OH should be searched for in J0855+5751.}, added-at = {2016-07-21T10:54:46.000+0200}, author = {Biggs, A. D. and Zwaan, M. A. and Hatziminaoglou, E. and Péroux, C. and Liske, J.}, biburl = {https://www.bibsonomy.org/bibtex/2d79e72de5d05c7bb6732d050b46d31b3/miki}, description = {[1607.05995] Parsec-scale HI absorption structure in a low-redshift galaxy seen against a Compact Symmetric Object}, interhash = {ca4a6b71fc3bb0bc75d10da225662aa5}, intrahash = {d79e72de5d05c7bb6732d050b46d31b3}, keywords = {HI absorption parsec scale}, note = {cite arxiv:1607.05995Comment: 14 pages and 10 figures. Accepted for publication in MNRAS}, timestamp = {2016-07-21T10:54:46.000+0200}, title = {Parsec-scale HI absorption structure in a low-redshift galaxy seen against a Compact Symmetric Object}, url = {http://arxiv.org/abs/1607.05995}, year = 2016 }