The JCMT Nearby Galaxies Legacy Survey

1. The JCMT Nearby Galaxies Legacy Survey Chris Wilson McMaster University 1. Survey design and goals 2. Science results

2. The JCMT Nearby Galaxies Legacy Survey team • C. Wilson, F. Israel, S. Serjeant (coordinators) • B. Warren, E. Sinukoff, D. Attewell; C. Baker, J. Newton, T. Parkin (major data processing) • G. Bendo, H. Butner, E. Brinks, S. Courteau, D. Clement, J. Irwin, J. Gallego, W. Heesen, J. Knapen, J. Leech, H. Matthews, A. Mok, S. Muhle, A. Mortimer, G. Petitpas, K. Spekkens, B. Tan, R. Tilanus, A. Usero, P. van der Werf, C. Vlahkis, T. Wiegert, M. Zhu • plus ~35 additional collaborators from the UK, Canada, and Netherlands

3. The JCMT Nearby Galaxies Legacy Survey: Physical Processes in Galaxies in the Local Universe • Relative mass and physical properties of different dust components (Galliano et al. 2003) • How reliable are integrated measurements of physical conditions in galaxies? • Molecular gas and the gas-to-dust ratio (Neininger et al. 1996) • Effect of galaxy morphology on the ISM • Effect of dense cluster environments (Kenney & Young 1989) • Effect of metallicity on the ISM (Madden et al. 2006) • The local submillimetre luminosity function (Dunne et al. 2000)

4. The JCMT Nearby Galaxies Legacy Survey: Physical Processes in Galaxies in the Local Universe • Relative mass and physical properties of different dust components (Galliano et al. 2003) • How reliable are integrated measurements of physical conditions in galaxies? • Molecular gas and the gas-to-dust ratio (Neininger et al. 1996) • Effect of galaxy morphology on the ISM • Effect of dense cluster environments (Kenney & Young 1989) • Effect of metallicity on the ISM (Madden et al. 2006) • The local submillimetre luminosity function (Dunne et al. 2000)

5. An HI-selected Sample • 155 galaxies between 2 and 25 Mpc • HI flux > 6 Jy km/s • 47 SINGS galaxies (Kennicutt et al. 2003) • 18 HI brightest Irr and E galaxies (HI flux > 3 Jy km/s) + 18 randomly selected spirals in Virgo Cluster • random selection of 72 field galaxies • D25 < 5’ • Randomly select 18 galaxies in each of 4 morphology bins (E, early S, late S, Irr)

6. JCMT data: CO • CO J=3-2 data cubes • Area covered is D25/2 • velocity range of 1000 km/s centered on mean galaxy velocity • Sensitivity 19 mK at 20 km/s resolution rms • Equivalent to Av = 1 mag or 2x1021 H/cm2 rms • Awarded 256 hours for CO • HARP science verification May-Oct 2007 • HARP survey observing Nov 2007-Nov 2009 • Detect ~45% of spirals, 20% of ellipticals, almost no irregulars • 9 papers published so far + 1 in preparation

7. JCMT data: continuum • SCUBA-2 850 and 450 micron imaging • Area covered is roughly D25/2 • Sensitivity goal 1.8 mJy/beam at 850 m in center of map • Awarded 100 hours in grade 2 weather for SCUBA-2 • SCUBA-2 science verification January 2012 • Survey observing February 2012-present • 48 spiral galaxies observed (25 from SINGS sample) • Insufficient sensitivity in practice to detect many of the field+Virgo galaxies in the allocated time • In the end, only a few galaxies observed in sufficiently good weather that 450 m data usable

8. JCMT data: continuum • Data reduction is still in progress … “One regime in which SMURF does not presently perform well is in maps of faint extended structures” (Chapin et al. 2013, MNRAS) - exactly the regime of the NGLS! • Don’t have a good idea of our rms noise level yet but is likely higher than target of 1.8 mJy/beam • Filtering in map making removes large-scale structure • Clearly seen in a comparison of SCUBA-2 and Herschel data for NGC 3627 (J. Newton, M.Sc. Thesis, McMaster)

9. 1. Star forming molecular gas in Virgo cluster and other spirals NGC 4321 (M100) NGC 4254 (M99) Wilson et al. 2009, ApJ NGC 4579 (M58) NGC 4569 (M90)

10. “Star formation rates” = 24 m + H SFR recipe from Calzetti et al. 2007 All images are on same colour scale

11. Gas depletion time = 1/SFE NGC4254 0.7 Gyr NGC4321 1.1 Gyr NGC4569 Quite uniform gas depletion times when CO J=3-2 used to trace mass of molecular gas tgas= Mmol/SFR 1.1 Gyr

12. NGC3521 Warren et al., 2010, ApJ

13. 2. Velocity dispersions in the molecular interstellar medium • Gas velocity dispersion is an important input to the Toomre criterion for disk stability Q = gGg • HI velocity dispersion 10+/-2 km/s at r25 (higher in interior,Tamburro et al. 2009) • Measurements of g in molecular component are rare

14. Velocity dispersion in molecular gas as a function of radius C. Wilson et al., 2011, MNRAS

15. 3. Correlation between CO J=3-2 and LFIR in SINGS galaxies from the NGLS LFIR/LCO(3-2) is 5 times larger for the U/LIRGs and high redshift galaxies from Iono et al. (2009) than for the SINGS galaxies from the NGLS (Wilson et al. 2012, MNRAS)

16. 4. The effect of environment on the molecular gas • Similar M(H2) but different tgas= M(H2)/SFR in Virgo, group, and isolated galaxies Mok et al., 2014, in prep.

17. 5. Dust in NGC 3627 with SCUBA-2 450 micron 500 micron JCMT+SCUBA2 Herschel+SPIRE NGLS KINGFISH (Kennicutt et al. 2011, PASP)

18. 5. Dust in NGC 3627 with SCUBA-2 450 micron 500 micron JCMT+SCUBA2 Herschel+SPIRE NGLS(Wilson et al.) KINGFISH (Kennicutt et al. 2011, PASP)

19. Dust mass and temperature from SCUBA-2 + Herschel data T  free Mdust J. Newton, M.Sc. thesis

20. Conclusions • NGLS CO survey has produced exciting new results • Still room to exploit the resolved nature of the CO images • Reduction and analysis of SCUBA-2 data still at a very early stage • Potential to involve new partners in this work? Public link to reduced CO J=3-2 data cubes and maps for complete NGLS: http://www.physics.mcmaster.ca/~wilson/www_xfer/NGLS/

21. The JCMT Nearby Galaxies Legacy Survey: Papers • Star-forming molecular gas in Virgo Cluster spiral galaxies, Wilson et al., 2009, ApJ, 693, 1736 • Warm molecular gas and star formation in three field spiral galaxies, Warren et al., 2010, ApJ, 714, 571 • The relations among PAHs, cold dust, molecular, and atomic gas in NGC 2403, G. Bendo et al., 2010, MNRAS, 402, 1409 • Very low velocity dispersions in the molecular interstellar medium of spiral galaxies, C. Wilson et al., 2011, MNRAS, 410, 1409

22. The JCMT Nearby Galaxies Legacy Survey: Papers • The CO(J= 3-2) distribution and molecular outflow in NGC 4631, Irwin et al., 2011, MNRAS, 410, 1423 • The distribution of gas and star formation in M 81, Sanchez-Gallego et al., 2011, A&A, 527, 16 • Halpha imaging and massive star formation properties, Sanchez-Gallego et al., 2012, A&A, 422, 3208 • CO data and the LCO(3-2)-LFIR correlation in the SINGS sample, Wilson et al., 2012, MNRAS, 424, 3050 - overview of survey • 12CO J = 3-->2 observations of NGC 2976 and NGC 3351, Tan et al., 2013, MNRAS, 436, 921

23. The JCMT Nearby Galaxies Legacy Survey Public link to reduced CO J=3-2 data cubes and maps for complete NGLS: http://www.physics.mcmaster.ca/~wilson/www_xfer/NGLS/

25. JCMT data: CO • Jiggle maps • Most efficient way to map small targets • CO J=3-2 field of view 2’x2’; ~1 hr/galaxy • Beam-switching with 150” chop of secondary • Used for galaxies with D25 < 5’ • Used 2-3 overlapping jiggles for edge-on galaxies • Raster maps • Required for larger targets (>4 jiggles in size) • On-the-fly scanning of rectangular area with specified position angle on the sky • Visit specified off position at end of each row • “basket weave” each map and make pairs of maps with 90 degree rotation of scan axis

26. Prospects for future surveys of nearby galaxies with the JCMT (1) CO J=3-2 surveys • Complete survey of all spiral galaxies within 25 Mpc accessible to JCMT • Smaller subset might focus on matching other samples with existing complementary data • Deeper surveys of elliptical galaxies • Good match in declination coverage to ATLAS-3D sample • CO 3-2/1-0 ratio could be interesting diagnostic • Deeper surveys of irregular galaxies • What does the very low detection rate in the NGLS tell us about their ISM?

27. Prospects for future surveys of nearby galaxies with the JCMT (2) SCUBA-2 450 m surveys • Competition for the same weather with the much larger Cosmology Legacy Survey resulted in few 450 m maps in the NGLS • High resolution (8”) at 450 m particularly interesting for nearby galaxies • Follow-up on SINGS spirals observed with NGLS • Follow-up on particularly interesting galaxies observed with Herschel (e.g. Virgo cluster)

28. Prospects for future surveys of nearby galaxies with the JCMT (3) SCUBA-2 850 m surveys • Originally we planned to use our time to map the 54 spiral galaxies in the HI-statistical sample from Virgo and the field sample • Lower than expected 850 m fluxes and higher noise meant this was impractical in the remaining time • Interesting environmental differences showing up in the CO 3-2 data from the NGLS • Reaching an rms noise of 1-1.5 mJy in ~3 hours per galaxy might make this feasible …

29. 3. A linear correlation between CO J=3-2 and far-infrared luminosity (Iono et al. 2009, ApJ) Slope (0.92+/-0.03) is similar to HCN (Gao & Solomon 2004) and significantly steeper than CO(1-0) (Yao et al. 2003)

30. Mean velocity dispersion in molecular gas only ~6 km/s C. Wilson et al., 2011, MNRAS

31. Warren et al., 2010, ApJ

32. Outline • Science goals and design of NGLS • Science results from the NGLS • Star formation efficiency in four Virgo and three field spiral galaxies • Low velocity dispersions in molecular gas • Global correlation between CO J=3-2 luminosity and star formation rate • Environmental differences in H2 content • Dust temperature and emissivity in NGC3627