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The Two T ightest Correlations: FIR-RC and FIR-HCN

The Two T ightest Correlations: FIR-RC and FIR-HCN. Yu GAO Purple Mountain Observatory, Nanjing Chinese Academy of Sciences . Stars are forming in giant molecular clouds (GMCs). Diffuse a tomic gas （ HI ） , the gas reservoir for the molecular clouds, and the supply

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The Two T ightest Correlations: FIR-RC and FIR-HCN

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  1. The Two Tightest Correlations: FIR-RC and FIR-HCN Yu GAO Purple Mountain Observatory, Nanjing Chinese Academy of Sciences

  2. Stars are forming in giant molecular clouds (GMCs)

  3. Diffuse atomic gas（HI）, the gas reservoir for the molecular clouds, and the supply of future star formation. PDRs

  4. Break-down of corr.: one example Zhang, Gao & Wang arXiv: 0911.4815

  5. Zhang, Gao & Wang arXiv: 0911.4815 70um and 160um overlaid with CO(1-0)

  6. Zhang, Gao & Wang arXiv: 0911.4815 HI and RC (radio continuum) images overlaid with CO(1-0)

  7. Dense gas is the essentialfuel for high mass SF in Galaxies HCN Surveys in 53 Galaxies: Gao & Solomon 2004a ApJS Far-IR, HCN, CO Correlations: Gao & Solomon 2004b ApJ

  8. SFR Dense Molecular Gas

  9. More CO data of ULIGs (Solomon et al. 1997) that Lco > ~ 10^10 K km/s pc^2 Total Molecular Gas Mass

  10. Gao, Carilli, Solomon & Vanden Bout 2007 ApJ, 660, L93 ^^^ || ~15hrs VLA, stacking 3 lens components

  11. r.m.s.~19uJy/beam More than 45hrs VLA

  12. Gao, Carilli, Solomon & Vanden Bout 2007 ApJ, 660, L93 13 HCN @high-z

  13. Fit to Galaxies Wu, Evans, Gao et al. 2005 ApJL Fit to GMCs Fit to All Krumholz & Thompson 2007

  14. SSCs in nearby galaxies could fill in the gap in FIR-HCN corr. Gap？

  15. Resovled Local (FIR-HCN) SF Law ? In Dense Gas (M51 & N6946)

  16. 70um maps & compared to HCN measurements Work in progress! Still far from the size scale of SSCs (by more than two orders of magnitude)

  17. Baan, Henkel, Loenen et al. 2008 HCN,CS,HNC etc. in SF Gals. • Baan et al. (2008) • Kohno 2007, et al. (2003) • Imanishi (2006) • Aalto et al. 2007, 2002, 1995 • Solomon et al. 1992 • Nguyen et al. 1992 • Henkel et al. 1990 • Henkel, Baan, Mauersberger 1991

  18. SF thresholds may simply reflect the change of the dominant cold gas phase in galaxies from HI ->H2 & from H2->denseH2 Bigiel’s talk @SFR50

  19. SFR vs. M_dense(H2): linear correlation

  20. SFR vs. M(H2): No Unique Slope:1, 1.4, 1.7? H2-dominated HI ~ H2 HI-dominated LSB galaxies Gao & Solomon 2004b ApJ

  21. Liu & Gao 2010 RC-HCN corr.

  22. Liu & Gao 2010 ApJ submitted

  23. Gao & Solomon 2004b Liu & Gao 2010

  24. Summary • Dense Cores in Dense Molecular Gas Complexes  High Mass Stars & SSCs -> SFR • (FIR-HCN Linear Correlation) SFR ~ M(DenseH2): the dense gas mass in galaxies & all star-forming systems? • SF thresholds: change of the dominant cold gas phase in galaxies from HI ->H2 & from H2->denseH2 • SFR: Counting Dense Cores/SSCs in Galaxies? • HI (LSBs) H2 (Spiral disks) denseH2 (starbursts/ULIRGs) Stars/SSCs • Resolved local correlations are the key  SFR

  25. FIR-radio vs. FIR-HCN correlations Differ both spatially and temporally • FIR, radio continuum (RC), HCN & CO • FIR-RC > FIR/RC-HCN > FIR/RC-CO • Stars Death SN/SNRs RC • Stars Form  UV/dust  FIR • CO  HCN  SF  FIR  RC • FIR-RC & FIR-HCN corr. the strongest! • Comparison of different SFR indicators

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