ABSTRACT We study the spatially resolved (sub-kpc) gas velocity dispersion (σ)–star formation rate (SFR) relation in the FIRE-2 (Feedback in Realistic Environments) cosmological simulations. We specifically focus on Milky Way-mass disc galaxies at late times (z ≈ 0). In agreement with observations, we find a relatively flat relationship, with σ ≈ 15–30 km s−1 in neutral gas across 3 dex in SFRs. We show that higher dense gas fractions (ratios of dense gas to neutral gas) and SFRs are correlated at constant σ. Similarly, lower gas fractions (ratios of gas to stellar mass) are correlated with higher σ at constant SFR. The limits of the σ–ΣSFR relation correspond to the onset of strong outflows. We see evidence of ‘on-off’ cycles of star formation in the simulations, corresponding to feedback injection time-scales of 10–100 Myr, where SFRs oscillate about equilibrium SFR predictions. Finally, SFRs and velocity dispersions in the simulations agree well with feedback-regulated and marginally stable gas disc (Toomre’s Q = 1) model predictions, and the simulation data effectively rule out models assuming that gas turns into stars at (low) constant efficiency (i.e. 1 per cent per free-fall time). And although the simulation data do not entirely exclude gas accretion/gravitationally powered turbulence as a driver of σ,more »
The centres of M83 and the Milky Way: opposite extremes of a common star formation cycle
ABSTRACT In the centres of the Milky Way and M83, the global environmental properties thought to control star formation are very similar. However, M83’s nuclear star formation rate (SFR), as estimated by synchrotron and H α emission, is an order of magnitude higher than the Milky Way’s. To understand the origin of this difference we use ALMA observations of HCN (1 − 0) and HCO+ (1 − 0) to trace the dense gas at the size scale of individual molecular clouds (0.54 arcsec, 12 pc) in the inner ∼500 pc of M83, and compare this to gas clouds at similar resolution and galactocentric radius in the Milky Way. We find that both the overall gas distribution and the properties of individual clouds are very similar in the two galaxies, and that a common mechanism may be responsible for instigating star formation in both circumnuclear rings. Given the considerable similarity in gas properties, the most likely explanation for the order of magnitude difference in SFR is time variability, with the Central Molecular Zone (CMZ) currently being at a more quiescent phase of its star formation cycle. We show M83’s SFR must have been an order of magnitude higher 5–7 Myr ago. M83’s ‘starburst’ phase was highly localized, both more »
- Award ID(s):
- 2008101
- Publication Date:
- NSF-PAR ID:
- 10342437
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 505
- Issue:
- 3
- Page Range or eLocation-ID:
- 4310 to 4337
- ISSN:
- 0035-8711
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Publisher's Version of Record
- https://doi.org/10.1093/mnras/stab1527
