%0 Generic %1 read2015matter %A Read, J. I. %A Agertz, O. %A Collins, M. L. M. %D 2015 %K baryon cores dark feedback matter %T Dark matter cores all the way down %U http://arxiv.org/abs/1508.04143 %X We use high resolution simulations of isolated dwarf galaxies to study the physics of dark matter cusp-core transformation at the edge of galaxy formation (Mvir = 10^7 - 10^9 Msun). We work at a resolution (4 pc) at which the impact from individual supernovae explosions can be resolved, becoming insensitive to even large changes in our numerical 'sub-grid' parameters. We find that our dwarf galaxies give a remarkable match to the stellar light profile; star formation history; metallicity distribution function; and star/gas kinematics of isolated dwarf irregular galaxies. Our key result is that dark matter cores of size comparable to the half light radius r_1/2 always form if star formation proceeds for long enough. Cores fully form in less than 4 Gyrs for the Mvir =10^8 Msun and 14 Gyrs for the 10^9 Msun dwarf. We provide a convenient two parameter 'coreNFW' fitting function that captures this dark matter core growth as a function of star formation time and the projected half light radius. Our results have several important implications: (i) we make a strong prediction that if LambdaCDM is correct, then 'pristine' dark matter cusps will be found either in systems that have truncated star formation and/or at radii r > r_1/2; (ii) complete core formation lowers the projected velocity dispersion at r_1/2 by a factor ~2, which is sufficient to fully explain the 'too big to fail problem' (though we stress that a full solution likely also involves unmodelled environmental effects); and (iii) cored dwarfs will be much more susceptible to tides, leading to a dramatic scouring of the subhalo mass function inside galaxies and groups. We will explore such environmental effects in a forthcoming paper.

@misc{read2015matter, abstract = {We use high resolution simulations of isolated dwarf galaxies to study the physics of dark matter cusp-core transformation at the edge of galaxy formation (Mvir = 10^7 - 10^9 Msun). We work at a resolution (4 pc) at which the impact from individual supernovae explosions can be resolved, becoming insensitive to even large changes in our numerical 'sub-grid' parameters. We find that our dwarf galaxies give a remarkable match to the stellar light profile; star formation history; metallicity distribution function; and star/gas kinematics of isolated dwarf irregular galaxies. Our key result is that dark matter cores of size comparable to the half light radius r_1/2 always form if star formation proceeds for long enough. Cores fully form in less than 4 Gyrs for the Mvir =10^8 Msun and 14 Gyrs for the 10^9 Msun dwarf. We provide a convenient two parameter 'coreNFW' fitting function that captures this dark matter core growth as a function of star formation time and the projected half light radius. Our results have several important implications: (i) we make a strong prediction that if LambdaCDM is correct, then 'pristine' dark matter cusps will be found either in systems that have truncated star formation and/or at radii r > r_1/2; (ii) complete core formation lowers the projected velocity dispersion at r_1/2 by a factor ~2, which is sufficient to fully explain the 'too big to fail problem' (though we stress that a full solution likely also involves unmodelled environmental effects); and (iii) cored dwarfs will be much more susceptible to tides, leading to a dramatic scouring of the subhalo mass function inside galaxies and groups. We will explore such environmental effects in a forthcoming paper.}, added-at = {2015-08-19T10:51:28.000+0200}, author = {Read, J. I. and Agertz, O. and Collins, M. L. M.}, biburl = {https://www.bibsonomy.org/bibtex/2d40eb11221b936b1293223889699bb18/miki}, description = {[1508.04143] Dark matter cores all the way down}, interhash = {5a7afc85dd6c9aa9fbd60abdbc4ec795}, intrahash = {d40eb11221b936b1293223889699bb18}, keywords = {baryon cores dark feedback matter}, note = {cite arxiv:1508.04143Comment: 17 pages; 7 figures; submitted to MNRAS. Comments welcome!}, timestamp = {2015-08-19T10:51:28.000+0200}, title = {Dark matter cores all the way down}, url = {http://arxiv.org/abs/1508.04143}, year = 2015 }