%0 Generic %1 Giavalisco2011 %A Giavalisco, Mauro %A Vanzella, Eros %A Salimbeni, Sara %A Tripp, Todd M. %A Dickinson, Mark %A Cassata, Paolo %A Renzini, Alvio %A Guo, Yicheng %A Ferguson, Henry C. %A Nonino, Mario %A Cimatti, Andrea %A Kurk, Jaron %A Mignoli, Marco %A Tang, Yuping %A ., %D 2011 %K accretion cold flows observation %T Discovery Of Cold, Pristine Gas Possibly Accreting Onto An Overdensity Of Star-Forming Galaxies At Redshift z ~ 1.6 %U http://arxiv.org/abs/1106.1205 %X We report the discovery of large amounts of cold (T ~ 10^4 K), chemically young gas in an overdensity of galaxies at redshift z ~ 1.6 in the Great Observatories Origins Deep Survey southern field (GOODS-S). The gas is identified thanks to the ultra-strong Mg II absorption features it imprints in the rest-frame UV spectra of galaxies in the background of the overdensity. There is no evidence that the optically-thick gas is part of any massive galaxy (i.e. M_star > 4x10^9 M_sun), but rather is associated with the overdensity; less massive and fainter galaxies (25.5 < z_850 < 27.5 mag) have too large an impact parameter to be causing ultra-strong absorption systems, based on our knowledge of such systems. The lack of corresponding Fe II absorption features, not detected even in co-added spectra, suggests that the gas is chemically more pristine than the ISM and outflows of star-forming galaxies at similar redshift, including those in the overdensity itself, and comparable to the most metal-poor stars in the Milky Way halo. A crude estimate of the projected covering factor of the high-column density gas (N_H >~ 10^20 cm-2) based on the observed fraction of galaxies with ultra-strong absorbers is C_F ~ 0.04. A broad, continuum absorption profile extending to the red of the interstellar Mg II absorption line by <~ 2000 km/s is possibly detected in two independent co-added spectra of galaxies of the overdensity, consistent with a large-scale infall motion of the gas onto the overdensity and its galaxies. Overall, these findings provides the first tentative evidence of accretion of cold, chemically young gas onto galaxies at high redshift, possibly feeding their star formation activity. The fact that the galaxies are members of a large structure, as opposed to field galaxies, might play a significant role in our ability to detect the accreting gas.

@misc{Giavalisco2011, abstract = { We report the discovery of large amounts of cold (T ~ 10^4 K), chemically young gas in an overdensity of galaxies at redshift z ~ 1.6 in the Great Observatories Origins Deep Survey southern field (GOODS-S). The gas is identified thanks to the ultra-strong Mg II absorption features it imprints in the rest-frame UV spectra of galaxies in the background of the overdensity. There is no evidence that the optically-thick gas is part of any massive galaxy (i.e. M_star > 4x10^9 M_sun), but rather is associated with the overdensity; less massive and fainter galaxies (25.5 < z_850 < 27.5 mag) have too large an impact parameter to be causing ultra-strong absorption systems, based on our knowledge of such systems. The lack of corresponding Fe II absorption features, not detected even in co-added spectra, suggests that the gas is chemically more pristine than the ISM and outflows of star-forming galaxies at similar redshift, including those in the overdensity itself, and comparable to the most metal-poor stars in the Milky Way halo. A crude estimate of the projected covering factor of the high-column density gas (N_H >~ 10^20 cm-2) based on the observed fraction of galaxies with ultra-strong absorbers is C_F ~ 0.04. A broad, continuum absorption profile extending to the red of the interstellar Mg II absorption line by <~ 2000 km/s is possibly detected in two independent co-added spectra of galaxies of the overdensity, consistent with a large-scale infall motion of the gas onto the overdensity and its galaxies. Overall, these findings provides the first tentative evidence of accretion of cold, chemically young gas onto galaxies at high redshift, possibly feeding their star formation activity. The fact that the galaxies are members of a large structure, as opposed to field galaxies, might play a significant role in our ability to detect the accreting gas. }, added-at = {2011-06-08T04:36:56.000+0200}, author = {Giavalisco, Mauro and Vanzella, Eros and Salimbeni, Sara and Tripp, Todd M. and Dickinson, Mark and Cassata, Paolo and Renzini, Alvio and Guo, Yicheng and Ferguson, Henry C. and Nonino, Mario and Cimatti, Andrea and Kurk, Jaron and Mignoli, Marco and Tang, Yuping and .}, biburl = {https://www.bibsonomy.org/bibtex/228a4180d647fa819891f7a81d84a74f7/miki}, description = {[1106.1205] Discovery Of Cold, Pristine Gas Possibly Accreting Onto An Overdensity Of Star-Forming Galaxies At Redshift z ~ 1.6}, interhash = {3212c25509294858b0e80333fc9d5068}, intrahash = {28a4180d647fa819891f7a81d84a74f7}, keywords = {accretion cold flows observation}, note = {cite arxiv:1106.1205Comment: 55 pages, 17 figures; submitted to ApJ; the manuscript incorporates the response to the referee report}, timestamp = {2011-06-08T04:36:56.000+0200}, title = {Discovery Of Cold, Pristine Gas Possibly Accreting Onto An Overdensity Of Star-Forming Galaxies At Redshift z ~ 1.6}, url = {http://arxiv.org/abs/1106.1205}, year = 2011 }