Abstract
We examine the stability of feedback-regulated star formation (SF) in galactic nuclei and contrast it to SF in extended discs. In galactic nuclei, the orbital time becomes shorter than the time over which feedback from young stars evolves. We argue analytically that traditional feedback-regulated SF equilibrium models break down in the regime. We study this using numerical simulations with the pc-scale resolution and explicit stellar feedback taken from stellar evolution models. The nuclear gas mass, young stellar mass and star formation rate (SFR) within the central ~100 pc (the short-time-scale regime) never reach steady state, but instead go through dramatic, oscillatory cycles. Stars form until a critical surface density of young stars is present (where feedback overwhelms gravity), at which point they expel gas from the nucleus. Since the dynamical times are shorter than the stellar evolution times, the stars do not die as the gas is expelled, but continue to push, triggering a runaway quenching of SF in the nucleus. However, the expelled gas is largely not unbound from the galaxy, but goes into a galactic fountain that re-fills the nuclear region after the massive stars from the previous burst cycle have died off (~50-Myr time-scale). On large scales ( > 1 kpc), the galaxy-scale gas content and SFR is more stable.We examine the consequences of this episodic nuclear SF for the Kennicutt-Schmidt (KS) relation: While a tight KS relation exists on ~1-kpc scales, the scatter increases dramatically in smaller apertures centred on galactic nuclei.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 2301-2314 |
| Number of pages | 14 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 467 |
| Issue number | 2 |
| DOIs | |
| State | Published - May 11 2017 |
Funding
We thank the referee, Eve Ostriker, for the many thoughtful comments that have strengthened this work. PT acknowledges helpful discussions with Sara Ellison, Nick McConnell and SarahWellons. PT is supported through Hubble Fellowship grant #HST-HF2-51384.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, NSF Collaborative Research Grant #1411920, and CAREER grant #1455342. CAFG was supported by NSF through grants AST-1412836 and AST-1517491, by NASA through grant NNX15AB22G and by STScI through grant HST-AR-14293.001-A. MV acknowledges support through an MIT RSC award. DK was supported by NSF grant AST-1412153 and Cottrell Scholar Award from the Research Corporation for Science Advancement. EQ was supported in part by NASA ATP grant 12-APT12-0183, a Simons Investigator award from the Simons Foundation, and the David and Lucile Packard Foundation. The simulations reported in this paper were run and processed on the 'Quest' computer cluster at Northwestern University, the Caltech compute cluster 'Zwicky' (NSF MRI award #PHY-0960291), the joint partition of the MIT-Harvard computing cluster 'Odyssey' supported by MKI and FAS, and allocation TG-AST130039 and TG-AST150059 granted by the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the NSF.
Keywords
- Galaxies: ISM
- Galaxies: evolution
- Galaxies: formation
- Galaxies: starburst
- Stars: formation
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science