Deep Impact :! Molecular Gas Properties under Strong ICM Pressure

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1 Deep Impact : Molecular Gas Properties under Strong ICM Pressure Bumhyun Lee & Aeree Chung Department of Astronomy, Yonsei University (Korea) The 3rd workshop on Large Aperture Mm/Submm Telescopes in the ALMA Era March 10-11, 2015, NAOJ, Mitaka, Japan

2 Cluster environments & Ram pressure stripping 2 Red Density Blue Low High Hogg et al Dressler 1980 Ellipticals and S0 galaxies: 90% of the whole population in cluster center Cluster galaxy population : passive and red Ram pressure stripping (the ISM stripping due to the ICM pressure): a spiral galaxy >>> a red S0

3 Cluster environments & Ram pressure stripping 3 Cluster spiral Field spiral Chung et al Yellow contours: HI gas Grey scale: the stellar disk Walter et al HI gas of many cluster spirals: smaller in mass compared to field counterpart with highly disturbed morphology and/or truncation within the stellar disk. (Davies & Lewis 1973; Warmerls 1988; Cayatte et al. 1990; Chung et al. 2009)

4 Cluster environments & Star formation activity 4 Cluster spiral, NGC4569 (Boselli et al. 2006) Field spiral, M33 (Hinz et al. 2004) B-band Hα B-band Hα Star formation activity in Virgo spirals is often found to be truncated within the stellar disk.

5 How about molecular gas in the cluster environment? 5 ICM pressure??? Molecular gas SF activities Galaxy evolution Still puzzling whether the ICM pressure can also strip dense molecular gas or not still under debate whether cluster galaxies are deficient in molecular gas or not (Casoli et al.1991; Kenny & Young 1989; Stark et al.1986 vs. Rengarajan & Iyenger 1992; Fumagalli et al. 2009)

6 How about molecular gas in the cluster environment? 6 E. J. Chung 2012, PhD thesis, Yonsei Univ. It is hard to define how deficient one galaxy is in molecular gas. The CO brightness ranges widely for galaxies in high and low-density environments CO deficiency cannot be defined in the same way as HI deficiency. E. Chung in preparation

7 How about molecular gas in the cluster environment? 7 Scientific goals : Investigate detailed properties of molecular gas of galaxies under ICM pressure Questions 1. How deeply can the impact of ICM pressure reach close to the center of a galaxy? 2. Can the molecular gas be still displaced even if it is not stripped? 3. Is it kinematics similar to those of field spirals? 4. Are the temperature and density comparable of field spirals?

8 Virgo cluster & Sample galaxies 8 NGC4569 NGC4522 M87 NGC4402 M86 NGC4330 Different HI stripping stages : (Simulation & Stellar population) Early to active ram pressure stage NGC4330, NGC 4402, NGC4522 post peak ram pressure NGC4569 M49 X-ray : blue, Böringer et al Optical : gray, DSS2 blue HI : yellow, Chung et al. 2009

9 Virgo cluster & Sample galaxies 9 NGC4569 NGC4522 M87 NGC4402 M86 NGC4330 Different HI stripping stages : (Simulation & Stellar population) Early to active ram pressure stage NGC4330, NGC 4402, NGC4522 post peak ram pressure NGC4569 M49 X-ray : blue, Böringer et al Optical : gray, DSS2 blue HI : yellow, Chung et al. 2009

10 Observations in sub-millimeter region 10 The Submillimeter Array (SMA) 8 antennas Array configuration : Subcompact NGC4330, NGC4402, NGC4522, except for NGC CO (2-1), GHz 13CO (2-1), GHz

11 Asymmetric molecular gas morphology 11 12CO (2-1): blue, SMA, Lee et al. in preparation 12CO (2-1): green, IRAM 30m, Vollmer et al HI: red, Chung et al D 25 in the optical B band: black, RC3

12 Asymmetric molecular gas morphology 12 NGC 4402 EAST WEST 12CO (2-1): blue, SMA, Lee et al. in preparation 12CO (2-1): green, IRAM 30m, Vollmer et al HI: red, Chung et al D 25 in the optical B band: black, RC3

13 Peculiar molecular gas kinematics 13 Velocity field (NGC 4402) Position-velocity diagram Color scale: velocity range(km/s) Lee et al. in preparation 1) Deviated from galactic rotation 2) Asymmetric kinematical structure Lee et al. in preparation Evidence for the influence of ICM pressure on the kinematics of molecular gas

14 Multi-wavelength data under ICM pressure 14 HI (green) 12CO (2-1) (white contours) FUV (blue) Hα (red) Optical (black) ICM wind direction (black arrows) NGC4402 Morphological correlation among multi-wavelength data 1) Similarity between Hα and CO 2) Locally induced star formation by compressed molecular gas Fujita & Nagashima (1999) 3) FUV, distinct morphology and extent from those of Hα/CO. 4) Time delay in star formation quenching

15 Active ram pressure vs. Post active ram pressure 15 NGC4330 NGC4522 NGC4569 NGC4402 Δ Active ram pressure stage (NGC 4330, NGC 4402, NGC4522) - Hα and CO are overall in good agreement. - FUV shows distinct morphology and extent from those of Hα/CO. Δ Post active ram pressure stage (NGC 4569) - The extent of FUV disc is comparable to that of Hα and CO.

16 Work in progress Physical properties of molecular gas 16 Studying physical properties in molecular gas with line ratios (12CO, 13CO) & non-lte model (RADEX, Van der Tak et al. 2007) Temperature and density distribution of CO gas of NGC 4402 IRAM 30m telescope OTF (on the fly) mode NGC CO (1-0), GHz 13CO (1-0), GHz 12CO (2-1), GHz 13CO (2-1), GHz

17 Work in progress Physical properties of molecular gas 17 North 3 South 3 Color scale: line ratio of To be further probed, temperature tool? North 3 South 3

18 Work in progress Physical properties of molecular gas 18 Temperature and density distribution of molecular gas in NGC 4402 Understand the star formation quenching process in the cluster galaxies Color scale: line ratio of 12CO (2-1) / (1-0) White contours: convolved 12CO (2-1) line

19 Summary 19 Molecular gas morphology is asymmetric and disturbed due to ICM pressure. Molecular gas kinematics also looks asymmetric and quite peculiar due to ICM pressure. Peculiarities found in molecular gas well trace of diffuse atomic gas, so as the direction of the wind. Molecular gas may get stripped (e.g. NGC 4522). More importantly, the ICM pressure seems to be able to change its properties deep inside of a galaxy, which can change star formation activity even if stripping does not take place. More detailed physical and chemical properties are under investigation using multi molecular gas transitions.

20 Scientific expectation for large single dish telescopes (LST, LMT, ) High-resolution CO imaging survey of nearby cluster galaxies ALMA Better understand the star formation quenching process in cluster galaxies ALMA, ideal system to do mapping with a few tens points and a few hours per galaxy. However, it s too expensive ALMA time Eg. 50meter single-dish telescope gives a resolution of ~6.5 arcsec at 12CO (2-1), which is still enough to trace the features to diagnose the environmental effects at a distance of Virgo

21 Scientific expectation for large single dish telescopes (LST, LMT, ) High-resolution CO imaging survey of nearby cluster galaxies SMA beam size, 7.21 X 3.89 arcsec ALMA Better understand the star formation quenching process in cluster galaxies ALMA, ideal system to do mapping with a few tens points and a few hours per galaxy. However, it s too expensive ALMA time Eg. 50meter single-dish telescope gives a resolution of ~6.5 arcsec at 12CO (2-1), which is still enough to trace the features to diagnose the environmental effects at a distance of Virgo Convolved beam size, 7.3 X 7.3 arcsec

22 Scientific expectation for large single dish telescopes (LST, LMT, ) Potential to use line ratios to probe the molecular conditions at all redshifts Cluster spiral (NGC4402) vs. Field spiral (NGC2903) 12CO(2-1)/(1-0): thermometer 12/13CO(1-0): optical depth, indicator of star formation activity The line ratios obtained by sensitive single-dish telescope will help us to understand the star formation activities and hence the evolution of galaxies at higher redshift.