the cool and warm molecular gas in m82 with...

Julia Kamenetzky

University of Colorado, Center for Astrophysics and Space Astronomy

IAU SpS12:Modern Views of the Interstellar Medium

August 30, 2012, Beijing

THE COOL AND WARM MOLECULAR GAS IN M82 WITH HERSCHEL-SPIRE

The Astrophysical Journal, 753:70 (17pp), 2012 July 1:

COLLABORATORS •  University of Colorado

•  Jason Glenn (Advisor) •  Phil Maloney •  Naseem Rangwala

•  NASA Jet Propulsion Laboratory •  Matt Bradford

•  McMaster University •  Christine Wilson (PI) •  Maximilien Schirm

•  UK ALMA Regional Centre Node •  George Bendo

•  ESA Astrophysics Missions Division •  Kate Isaak

•  CEA France •  Suzanne Madden •  Pasquale Panuzzo •  Ronin Wu

•  INAF Italy •  Luigi Spinoglio

•  … And other members of the Herschel SAG-2 Group, Very Nearby Galaxies Survey (VNGS)

KAMENETZKY, M82, IAU 2

MOLECULAR GAS AND CO

KAMENETZKY, M82, IAU 3

•  Edge-on (77�) SBc (Mayya 2005)

•  3.4 Mpc away (17 pc/”)

•  9.8 M¤/yr, enhanced with interaction with M81 (Yun 1993)

NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

M82

•  Interaction between star formation, molecular gas excitation (and AGN…)

•  Who is influencing whom?

•  Balance of different energy sources

•  Cosmic rays, UV from stars, X-rays from AGN, turbulent motion

•  CO 1-0 traces morphology of cold molecular gas

•  CO excitation ladder can tell us physical conditions (temperature, density, column density)

•  This knowledge required for energy budgets •  What is different about the CO SLED at higher-

J lines, previously unobservable before Herschel?

KAMENETZKY, M82, IAU 4

400 450 500 550 600 650 700 750Frequency [GHz]

50

0

50

100

150

200Jy

CO4

3

CI1

0

HCN 6

5

13CO

54 CO

54

HCO

+ 76

13CO

65

CO6

5

700 650 600 550 500 450 400Wavelength [microns]

700 750 800 850 900 950 1000Frequency [GHz]

050

100

150

200

250300

Jy

H 2O

13CO

76 CO

76

CI2

1

OH+

CO8

7 OH+

H 2O

300325350375400425Wavelength [microns]

950 1000 1050 1100 1150 1200 1250 1300Frequency [GHz]

0

100

200

300

Jy

OH+

H 2O

OH+

CO9

8 H 2O

H 2O

H 2O

+

CO10

9 H 2O

HF

CO11

10

240250260270280290300310Wavelength [microns]

Ripples are because spectrum is the FT of interferogram. Source/Beam Coupling: •  Panuzzo (2010) •  Derived using SPIRE

photometer 250 µm map (Roussel 2010)

•  Tested by comparison to mapping observation with kernels to scale all maps to CO 4-3 beam.

Fitting; •  Lines fit as individual sinc

functions, allows for subtraction of local background.

•  Brightest (CO, [CI], [NII]) lines subtracted before weaker lines fit.

1250 1300 1350 1400 1450 1500 1550 1600

Frequency [GHz]

0

200

400

600

800

Jy

CO11

10

CO12

11 NII

CO13

12

230 220 210 200 190Wavelength [microns]

•  RADEX: Radiative Transfer

•  van der Tak 2007

•  Temperature, density, column density per unit linewidth

•  CMB background

•  Introduce area filling factor parameter, scales vertically

•  Bayesian Likelihood

•  Compare data, x, to model fluxes, I(p)

•  Binary Prior Probabilities: grid point must not be more massive than dynamical mass, or longer in column than the length of the galaxy, or have an optical depth > 100

•  Two-Component, Iterative Approach

RADEX AND BAYESIAN LIKELIHOOD

KAMENETZKY, M82, IAU 5

•  Ground based data alone (Ward 2003) would only indicate the cool (40 K) molecular gas.

•  SPIRE data requires warmer (450 K) molecular gas (~ 5% of the cool gas mass).

•  Intermediate-J (3-2, 4-3) lines have contributions from both components.

RADEX LIKELIHOOD RESULTS

KAMENETZKY, M82, IAU 6

SIMULTANEOUS MODELING WITH 13CO

KAMENETZKY, M82, IAU 7

•  Add 13CO/12CO column density ratio as an extra parameter, result is about 3%.

•  Increases relative mass of warm component (10%).

GAS EXCITATION

KAMENETZKY, M82, IAU 8

•  Warm component temperature

•  cooling dominated by hydrogen

•  3 L¤/M¤ (Le Bourlot 1999)

•  Cosmic rays not enough alone, no AGN to power XDR

•  PDRs? Good enough for low-J.

•  High-density PDRs required to explain high-J emission; inconsistent with radiative transfer results.

•  Enhanced cosmic-ray PDRs may explain (Meijerink 2006)

•  Shocks + PDRs (Pon 2012) for J > 7-6

•  Turbulent heating sufficient given large enough velocity gradients (~ 35 km/s/pc)

COMPARISONS TO OTHER GALAXIES

KAMENETZKY, M82, IAU 9

•  Mrk 231, Seyfert 1, van der Werf 2010

•  Flat high-J CO luminosity SLED

•  Requires XDR or dense PDR

•  Arp220, Rangwala 2011

•  XDR for ionized molecules

•  HLSW-01, Scott 2011, z=2.96

•  Can be fit with one component

•  Tentative evidence for AGN

•  NGC891, quiescent galaxy, Nikola 2011

•  Requires shocks + PDRs for J=7-6, 6-5.

Image courtesy of Naseem Rangwala

CONCLUSIONS

KAMENETZKY, M82, IAU 10

•  Herschel has enabled use to see the high-excitation molecular gas in an increasing number of galaxies.

•  Warm (450 K) molecular gas in M82 is likely coming from a non-ionizing source

•  Combinations of turbulent motion, shocks + PDRs, cosmic-ray enhanced PDRs

•  The molecular mass is dominated by cool gas, but the luminosity dominated by warmer gas, consistent with other star-forming galaxies.

•  CO SLEDs demonstrate different shapes with different galaxy types.

QUESTIONS?

KAMENETZKY, M82, IAU 11

KAMENETZKY, M82, IAU 12

CO only 12CO and 13CO

HERSCHEL SPACE TELESCOPE SPIRE FOURIER TRANSFORM SPECTROMETER (FTS)

KAMENETZKY, M82, IAU 13

Image: ESA / AOES Medialab, Background: Hubble Space Telescope, NASA/ ESA/ STScI

Maiolino 2008 1200! 1400! 1600!

450 to 1550 GHz

(About 700 to 190 microns)

CO J=1-0 2-1 3-2 4-3 5-4 6-5 7-6 8-7 9-8 10-9 11-10 12-11 13-12

KAMENETZKY, M82, IAU 14

400 450 500 550 600 650 700 750Frequency [GHz]

50

0

50

100

150

200Jy

CO4

3

CI1

0

HCN 6

5

13CO

54 CO

54

HCO

+ 76

13CO

65

CO6

5

700 650 600 550 500 450 400Wavelength [microns]

700 750 800 850 900 950 1000Frequency [GHz]

050

100

150

200

250300

Jy

H 2O

13CO

76 CO

76

CI2

1

OH+

CO8

7 OH+

H 2O

300325350375400425Wavelength [microns]

950 1000 1050 1100 1150 1200 1250 1300Frequency [GHz]

0

100

200

300

Jy

OH+

H 2O

OH+

CO9

8 H 2O

H 2O

H 2O

+

CO10

9 H 2O

HF

CO11

10

240250260270280290300310Wavelength [microns]

Ripples are because spectrum is the FT of interferogram. Source/Beam Coupling: •  Panuzzo (2010) •  Derived using SPIRE

photometer 250 µm map (Roussel 2010)

•  Tested by comparison to mapping observation with kernels to scale all maps to CO 4-3 beam.

1250 1300 1350 1400 1450 1500 1550 1600Frequency [GHz]

0

200

400

600

800

Jy

CO11

10

CO12

11 NII

CO13

12

230 220 210 200 190Wavelength [microns]

COMPARISONS TO OTHER GALAXIES

KAMENETZKY, M82, IAU 15

•  Mrk 231, Seyfert 1, van der Werf 2010 •  Flat high-J CO luminosity SLED •  Requires XDR or dense PDR

•  Arp220, Rangwala 2011 •  XDR for ionized molecules

•  HLSW-01, Scott 2011, z=2.96 •  Can be fit with one component

•  Tentative evidence for AGN •  NGC891, quiescent galaxy, Nikola 2011

•  Requires shocks + PDRs for J=7-6, 6-5.

FUTURE WORK

Image courtesy of Naseem Rangwala

•  Herschel’s mission will end in less than a year

•  ALMA will add morphology to many submm galaxies (not M82 – too far north)