%0 Generic %1 Krumholz2011 %A Krumholz, Mark R. %A Dekel, Avishai %A McKee, Christopher F. %D 2011 %K density law sfr %T A Universal, Local Star Formation Law in Galactic Clouds, Nearby Galaxies, High-Redshift Disks, and Starbursts %U http://arxiv.org/abs/1109.4150 %X abridged While observations of Local Group galaxies show a very simple, local star formation law in which the star formation rate per unit area in each patch of a galaxy scales linearly with the molecular gas surface density in that patch, recent observations of both Milky Way molecular clouds and high redshift galaxies apparently show a more complicated relationship, in which regions of equal molecular gas surface density can form stars at quite different rates. These data have been interpreted as implying either that different star formation laws may apply in different circumstances, that the star formation law is sensitive to large-scale galaxy properties rather than local properties, or that there are high density thresholds for star formation. Here we collate observations of the relationship between gas and star formation rate from resolved observations of Milky Way molecular clouds, from kpc-scale observations of Local Group galaxies, and from unresolved observations of both disk and starburst galaxies in the local universe and at high redshift. We show that all of these data are in fact consistent with a simple, local, volumetric star formation law. The apparent variations stem from the fact that the observed objects have a wide variety of scale heights, so even at fixed gas column density the regions being observed can have wildly varying volume densities. Once this projection effect is removed, all the data, from small Solar neighborhood clouds with masses ~10^3 Msun to sub-mm galaxies with masses ~10^11 Msun, fall on a single star formation law in which the star formation rate is simply ~1% of the molecular gas mass per local free-fall time. In contrast, proposed star formation laws in which the star formation timescale is set by the galactic rotation period or is linearly proportional to the gas mass above some density threshold fail to match the data.

@misc{Krumholz2011, abstract = { [abridged] While observations of Local Group galaxies show a very simple, local star formation law in which the star formation rate per unit area in each patch of a galaxy scales linearly with the molecular gas surface density in that patch, recent observations of both Milky Way molecular clouds and high redshift galaxies apparently show a more complicated relationship, in which regions of equal molecular gas surface density can form stars at quite different rates. These data have been interpreted as implying either that different star formation laws may apply in different circumstances, that the star formation law is sensitive to large-scale galaxy properties rather than local properties, or that there are high density thresholds for star formation. Here we collate observations of the relationship between gas and star formation rate from resolved observations of Milky Way molecular clouds, from kpc-scale observations of Local Group galaxies, and from unresolved observations of both disk and starburst galaxies in the local universe and at high redshift. We show that all of these data are in fact consistent with a simple, local, volumetric star formation law. The apparent variations stem from the fact that the observed objects have a wide variety of scale heights, so even at fixed gas column density the regions being observed can have wildly varying volume densities. Once this projection effect is removed, all the data, from small Solar neighborhood clouds with masses ~10^3 Msun to sub-mm galaxies with masses ~10^11 Msun, fall on a single star formation law in which the star formation rate is simply ~1% of the molecular gas mass per local free-fall time. In contrast, proposed star formation laws in which the star formation timescale is set by the galactic rotation period or is linearly proportional to the gas mass above some density threshold fail to match the data. }, added-at = {2011-09-22T07:32:58.000+0200}, author = {Krumholz, Mark R. and Dekel, Avishai and McKee, Christopher F.}, biburl = {https://www.bibsonomy.org/bibtex/2c2638aac7e5a1a3ed933c2be08f230a9/miki}, description = {[1109.4150] A Universal, Local Star Formation Law in Galactic Clouds, Nearby Galaxies, High-Redshift Disks, and Starbursts}, interhash = {a6aef8f7dd7efb8ad70ec48e250a04bb}, intrahash = {c2638aac7e5a1a3ed933c2be08f230a9}, keywords = {density law sfr}, note = {cite arxiv:1109.4150Comment: 19 pages, 4, figures, 4 tables, emulateapj format, submitted to ApJ}, timestamp = {2011-09-22T07:32:58.000+0200}, title = {A Universal, Local Star Formation Law in Galactic Clouds, Nearby Galaxies, High-Redshift Disks, and Starbursts}, url = {http://arxiv.org/abs/1109.4150}, year = 2011 }