The Dust and Molecular Gas in Brightest Cluster Galaxies. Alastair Edge (Durham University) and many collaborators

Transcription

1 The Dust and Molecular Gas in Brightest Cluster Galaxies Alastair Edge (Durham University) and many collaborators

2 Summary In the next 20mins I will skim the results on cold molecular and atomic gas and dust in the cores of clusters. Why clusters? start with X ray selected clusters orientalon of Brightest Cluster Galaxy and its core will be random BCGs are the most massive galaxies we know

3 Secular washing cycle (Mericlessly cribbed from Alexander & Hickox 2012!)

4 Cold, cooling and cooled I will leave the semanlc discussion of cool core/cooling flow for others and instead I ll focus on the simple issue of the presence and properles of gas/dust at <10 3 K in clusters and the links to the wider properles of the cluster. We will learn only when we determine the properles of many clusters, not just a few extreme ones.

5 .talking of which! No review in this area is complete without acknowledging the Monster that is NGC1275

6

7 Feeding Feedback? The realisalon that AGN feedback has a dramalc effect on cluster cores is thanks largely to Chandra observalons of caviles and temperature profiles on <100kpc scales. However, the feedback loop requires some gas to cool in order fuel AGN aclvity. Can we find this gas and use its properles to refine models?

8 CO History In the 1990s a number of groups searched for CO in BCGs with no success apart from NGC1275. Why? Receivers narrow bandwidth Telescopes 10 12m dishes are not sensilve enough Targets very few BCGs as extreme as NGC1275 were observed.

9 Like near Earth asteroids? You wait for ages for one event then more seem to follow immediately ajer. Likewise with CO deteclons of BCGs. Within a year of the first JCMT deteclon we had more than a dozen others!

10

11 CO deteclons reach teenage years! In the past 13 years we have gone from one to >46 CO deteclons! What can we learn from these deteclons?

12 Sepng a baseline Making any deteclon of CO tells us that there is at least some molecular gas present. The fact it isn t at the level expected for a classic cooling flow that is years old is an important mirror of the X ray constraints on mass deposilon rates.

13 CO dynamics One of the factors that affects the likelihood of deteclng a parlcular line is the line width. This can vary from 100 to 800 km s 1!

14

15 CO dynamics One of the factors that affects the likelihood of deteclng a parlcular line is the line width. This can vary from 100 to 800 km s 1! Also there are a number of systems that show clear double peaked line profiles that are characterislc of gas disks.

16 Hydra A CO(2 1) IRAM 30m spectrum

17 A1664 CO(2 1) IRAM 30m spectrum

18 CO correlalons The CO line strengths and the molecular gas mass derived from them can be compared to a number of other tracers of the cold gas phase.

19 Edge (2001) updated Hα line luminosity vs M H2 NGC1275 AGN dominated Cygnus A

20 O Dea et al (2008) Spitzer MIR derived SFR vs MH2

21 CO future ALMA is clearly going to revolulonise our ability to study CO in BCGs in terms of spalal resolulon and sensilvity. CAMRA, SMA and PdBI in the north will be important. Also there are many other lines that can be used to derive the properles of the cold phase ( 13 CO, HCN, CN, HCO + ) see Bayet et al (2011).

22 Atomic Gas Herschel offered us the first realislc opportunity to detect emission from atomic lines CII, OI and others that are efficient cooling lines in the cool ISM. I am PI of a Key Project that observed 11 BCGs. There are also several other OT1 and OT2 programmes.

23 See Edge et al (2010)

24 See Edge et al (2010)

25 NGC1275 CII Herschel PACS channel map Miual et al 2012

26 Herschel Spectroscopy Summary Cold atomic gas found in all sources with significant CO deteclons. RaLos of lines consistent with other classes of starburst and (U)LIRG galaxies. Line widths similar to oplcal and CO lines but perhaps not idenlcal. Extended emission consistent with oplcal line morphology.

27 Dust Cold molecular gas is infused with dust wherever it is found. Can we use the FIR dust conlnuum to understand the cold gas? SCUBA deteclons of two BCGs were published in July 1999 and now with Herschel this number is it is ~ In the MIR, 24µm deteclons with Spitzer and WISE are nearing 100.

28 Herschel imaging of Edge et al (2010) clusters PACS SPIRE

29 Abell 1068 radio UV SED including Herschel PACS+Spire

30 Rawle et al (2012)

31 Rawle et al (2012)

32 Rawle et al (2012)

33 What does it all mean? The implicalons of the cold gas in BCGs is perhaps best illustrated in one system Hydra A (or 3C218 to the radio astronomers in the audience!).

34 Hydra A VIMOS IFU Hamer et al 2013

35 Hydra A Sinfoni IFU Hamer et al 2013

36 Hydra A Disk fits Hamer et al 2013

37 Hydra A Disk fits Hamer et al 2013

38 Hydra A Feedback? Hamer et al 2013

39 What does it all mean? There is an observed conneclon between X ray cooling and oplcal line emission (Cavagnolo et al 2008).

40 Cavagnolo et al (2008) Hα vs central entropy L H! [10 40 ergs s -1 ] K 0 [kev cm 2 ]

41 What does it all mean? There is an observed conneclon between X ray cooling and oplcal line emission (Cavagnolo et al 2008). Therefore, by inference, X ray cooling and the amount of cold gas are also related. The CO deteclon limit with current technology means we don t detect every line emipng BCG. Yet.

42 The Future ALMA will allow CO deteclons of a factor of fainter. WISE, GALEX, oplcal/nir and S Z can be used to select aclve BCGs irrespeclve of the X ray properles of the cluster so in principle many hundreds of systems can be studied.

43 The Phoenix McDonald et al 2012 (aka SPT ) Nature z=0.596 L x =8x erg/s M=3800M o /yr SFR=800M o /yr L FIR =10 13 L o T dust = 85K L QSO =10 47 erg/s? Most X ray luminous cluster known is found from its S Z properles!

44 Conclusions There is a cold phase in essenlally every cooling flow that can be traced in CO, FIR, oplcal and NIR lines and dust conlnuum. The properles and dynamics of this gas have a major influence on the appearance and future AGN aclvity of the BCG it pollutes and the surrounding cluster caught in the cross fire.