the jcmt nearby galaxies legacy survey

The JCMT Nearby Galaxies Legacy SurveyThe JCMT Nearby Galaxies Legacy Survey

Chris Wilson McMaster University

1. Survey design and goals

2. Science results

The JCMT Nearby Galaxies The JCMT Nearby Galaxies Legacy Survey teamLegacy 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

The JCMT Nearby Galaxies Legacy The JCMT Nearby Galaxies Legacy Survey: Physical Processes in Survey: Physical Processes in Galaxies in the Local UniverseGalaxies 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)

An HI-selected SampleAn 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)

JCMT data: COJCMT 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

JCMT data: continuumJCMT 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

JCMT data: continuumJCMT 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)

1. Star forming molecular gas in 1. Star forming molecular gas in Virgo cluster and other spiralsVirgo cluster and other spirals

NGC 4254(M99)

NGC 4579(M58)

NGC 4569(M90)

NGC 4321(M100)

Wilson et al.2009, ApJ

““Star formation rates” = 24 Star formation rates” = 24 m + Hm + H

All imagesare on same colour scale

SFR recipe from Calzettiet al. 2007

Gas depletion time = 1/SFEGas depletion time = 1/SFENGC4254 0.7 Gyr

NGC4321 1.1 Gyr

NGC4569

Quite uniform gas depletion times whenCO J=3-2 used to tracemass of molecular gas

1.1 Gyr

tgas= Mmol/SFR

NGC3521

Warren et al., 2010, ApJ

2. Velocity dispersions in the 2. Velocity dispersions in the molecular interstellar mediummolecular interstellar medium

• Gas velocity dispersion is an important input to the Toomre criterion for disk stability Q = gGg

• HI velocity dispersion 10+/-2 km/s at r25 (higher in interior,Tamburro et al. 2009)

• Measurements of g in molecular component are rare

Velocity dispersion in molecular gas Velocity dispersion in molecular gas as a function of radiusas a function of radius

C. Wilson et al., 2011, MNRAS

3. Correlation between CO J=3-2 and L3. Correlation between CO J=3-2 and LFIRFIR in SINGS galaxies from the NGLSin 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)

4. The effect of environment 4. The effect of environment on the molecular gason the molecular gas

• Similar M(H2) but different tgas= M(H2)/SFR in Virgo, group, and isolated galaxies

Mok et al., 2014, in prep.

5. Dust in NGC 3627 with SCUBA-25. Dust in NGC 3627 with SCUBA-2

450 micron 500 micronJCMT+SCUBA2 Herschel+SPIRENGLS KINGFISH (Kennicutt et al. 2011, PASP)

5. Dust in NGC 3627 with SCUBA-25. Dust in NGC 3627 with SCUBA-2

450 micron 500 micronJCMT+SCUBA2 Herschel+SPIRENGLS(Wilson et al.) KINGFISH (Kennicutt et al. 2011, PASP)

Dust mass and temperature from Dust mass and temperature from SCUBA-2 + Herschel dataSCUBA-2 + Herschel data

free

T

Mdust

J. Newton, M.Sc. thesis

ConclusionsConclusions• 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/


The JCMT Nearby Galaxies The JCMT Nearby Galaxies Legacy Survey: PapersLegacy Survey: Papers

I. Star-forming molecular gas in Virgo Cluster spiral galaxies, Wilson et al., 2009, ApJ, 693, 1736

II. Warm molecular gas and star formation in three field spiral galaxies, Warren et al., 2010, ApJ, 714, 571

III. The relations among PAHs, cold dust, molecular, and atomic gas in NGC 2403, G. Bendo et al., 2010, MNRAS, 402, 1409

IV. Very low velocity dispersions in the molecular interstellar medium of spiral galaxies, C. Wilson et al., 2011, MNRAS, 410, 1409

The JCMT Nearby Galaxies The JCMT Nearby Galaxies Legacy Survey: PapersLegacy Survey: Papers

V. The CO(J= 3-2) distribution and molecular outflow in NGC 4631, Irwin et al., 2011, MNRAS, 410, 1423

VI. The distribution of gas and star formation in M 81, Sanchez-Gallego et al., 2011, A&A, 527, 16

VII. Halpha imaging and massive star formation properties, Sanchez-Gallego et al., 2012, A&A, 422, 3208

VIII. CO data and the LCO(3-2)-LFIR correlation in the SINGS sample, Wilson et al., 2012, MNRAS, 424, 3050 - overview of survey

IX. 12CO J = 3-->2 observations of NGC 2976 and NGC 3351, Tan et al., 2013, MNRAS, 436, 921

The JCMT Nearby Galaxies The JCMT Nearby Galaxies Legacy SurveyLegacy Survey

Public link to reduced CO J=3-2 data cubes and maps for complete NGLS:




JCMT data: COJCMT 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

Prospects for future surveys of Prospects for future surveys of nearby galaxies with the JCMTnearby 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?


(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)


(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 …

3. A linear correlation between CO 3. A linear correlation between CO J=3-2 and far-infrared luminosityJ=3-2 and far-infrared luminosity

• Slope (0.92+/-0.03) is similar to HCN (Gao & Solomon 2004) and significantly steeper than CO(1-0) (Yao et al. 2003)

(Iono et al. 2009, ApJ)

Mean velocity dispersion in Mean velocity dispersion in molecular gas only ~6 km/smolecular gas only ~6 km/s

QuickTime™ and a decompressor

are needed to see this picture.

C. Wilson et al., 2011, MNRAS

Warren et al., 2010, ApJ

OutlineOutline

• 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

the jcmt nearby galaxies legacy survey

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