Spatially resolved star-formation relations of dense molecular gas in NGC 1068

M. Sánchez-García; S. García-Burillo; M. Pereira-Santaella; L. Colina; A. Usero; M. Querejeta; A. Alonso-Herrero; A. Fuente

doi:10.1051/0004-6361/202142396

paper

Spatially resolved star-formation relations of dense molecular gas in NGC 1068

arXiv:2201.06552 · doi:10.1051/0004-6361/202142396

Abstract

We analyse the influence of the dynamical environment on the star formation (SF) relations of the dense molecular gas in the starburst (SB) ring of the Seyfert 2 galaxy NGC 1068. We used ALMA to image the emission of the 1-0 transitions of HCN and HCO+ with a resolution of 56 pc. We also used ancillary data of CO(1-0) at a resolution of ~100 pc, and CO(3-2) and its underlying continuum emission at ~40 pc. These observations allow us to probe a range of molecular gas densities (n(H2)~10 $^{3 - 5} c m^{- 3}$ ). The SF rate (SFR) is derived from Pa $α$ line emission imaged by HST/NICMOS. We analysed how SF relations change depending on the choice of aperture sizes and molecular gas tracer. The scatter in the Kennicutt-Schmidt relation is about a factor of two to three lower for the HCN and HCO+ lines compared to CO(1-0) for a common aperture. Correlations lose statistical significance below a critical spatial scale $\approx$ 300-400 pc. The SF efficiency of the dense molecular gas (SFEdense) shows a scattered distribution as a function of the HCN luminosity (L'(HCN)) around a mean value of $≃ 0.01$ Myr $^{- 1}$ . An alternative prescription for SF relations, linking the SFEdense and the boundedness of the gas measured by the parameter b $\equiv Σ$ dense/ $σ^{2}$ , where $Σ$ dense is the dense molecular gas surface density and $σ$ the velocity dispersion, resolves the degeneracy associated with the SFEdense-L'(HCN) plot. We identify two branches in the SFEdense-b plot that correspond to two dynamical environments in the SB ring, which are defined by their proximity to the bar-ring interface region. This region corresponds to the crossing of two density wave resonances, where an increased rate of cloud-cloud collisions would favour an enhanced compression of molecular gas. Our results suggest that galactic dynamics plays a major role in the efficiency of the gas conversion into stars.

arXiv comment30 pages, 34 figures, 4 tables. Accepted for publication in Astronomy & Astrophysics

Spatially resolved star-formation relations of dense molecular gas in NGC 1068

Abstract

References in corpus (103)

Cited by in corpus (14)