CMB foreground modeling and its subtraction: a prospect from galaxy evolution

1. CMB foreground modeling and its subtraction: a prospect from galaxy evolution Tsutomu T. TAKEUCHI Institute for Advanced Research, Nagoya University, Japan Cosmic Microwave Background Radiation and Its Foreground Interstellar Components, Tokyo, 17th February, 2010

2. Galaxy meets cosmology again

3. 1. CMB and Foregrounds 1.1 Schematic view of the CMB foregrounds Hinshaw et al. (2007)

4. 1.2 Foregrounds from the CMB point of view • Foregrounds: • Galactic: in the Milky Way, • Extragalactic: at a cosmological distance. Galactic disk

5. 1.2 Foregrounds from the CMB point of view • Foregrounds: • Galactic: strongly anisotropic, • Extragalactic: (supposedly) isotropic. Galactic disk

6. 1.2 Foregrounds from the CMB point of view • Foregrounds: • Galactic: strongly anisotropic, • Extragalactic: (supposedly) isotropic. Galactic: astrophysical approach (with local statistics) e.g., multiwavelength map-based subtraction. Extragalactic: global statistical approach e.g., power spectrum (Cℓ)-based treatment.

7. 1.2 Foregrounds from the CMB point of view • Foregrounds: • Galactic: strongly anisotropic, • Extragalactic: (supposedly) isotropic. Galactic: astrophysical approach (with local statistics) e.g., multiwavelength map-based subtraction. Extragalactic: global statistical approach e.g., power spectrum (Cℓ)-based treatment. Though the approach would be different, both of them are basically based on galaxies (including our Galaxy). Then, common knowledge can be used.

8. 2. Extragalactic Foregrounds 2.1 Dusty galaxies as a contributor to the CMB There are various cosmological sources of the CMB foreground, and especially dusty IR galaxies and radio galaxies are relevant. Galaxies contributing to the radio are divided into two categories: Star forming galaxies AGNs Both can be treated simultaneously in the framework of phenomenological galaxy evolution model, since the physical origin of radio continuum is similar (thermal free-free and synchrotron radiation), and they are thought to be related physically (e.g., scenario of starburst-AGN connection).

9. Phenomenological dusty galaxy evolution model Takeuchi et al. (2001a, b, 2002) Lagache et al. (2003, 2004) Le Borgne et al. (2008) Valiante et al. (2009) Béthermin et al. (2011)… Ingredients of the model Spectral energy distribution (SED) Luminosity function (LF) Cosmological parameters Galaxy Evolution (in principle, related to SEDs and LF)

10. Current status of the SED modeling Dopita et al. (2005) As for radio galaxies, we can use the same framework with physical processes of accretion disk and jets. But they are rather minor contributors.

11. Constraints on the evolution from observation Empirical models try to constrain the evolution of galaxies by reproducing galaxy number counts, integrated background spectrum, and recently LF directly. (Takeuchi et al. 2001a, Le Borgne et al. 2008, Valiante et al. 2009)

12. Cosmic infrared background spectrum Takeuchi et al. (2001a) Le Borgne et al. (2008)

13. 2.2 Evolution of the clustering of IR galaxies To calculate the power spectrum of the fluctuation of the cosmic IR background (CIB), we need to model the clustering property of dusty galaxies, which is still very uncertain. Since the connection between dark halo formation and galaxy formation is far from being well understood, we need to introduce a simplistic model. Currently the most popular one is the halo model, but still quite premature. IR galaxy evolution with a halo model: Song et al. (2003) Takeuchi et al. (2005a) Amblard & Cooray (2007) Hall et al. (2010) Marsden et al. (2009)… Pénin et al. (2011)

14. Basic idea of the halo model Halo mass profile 2pt-correlation function Quasi nonlinear Nonlinear Large scale: statistically characterized by the correlation of virialized structures (halos). Small scale: characterized by the internal density profile of each halo. Then, the nonlinear power spectrum of the matter/galaxy distribution is described by halo profiles (1 halo term) + 2pt correlation (2 halo term).

15. Nonlinear evolution of the power spectrum D(k) Nonlinear growth Linear power (Ma 1998)

16. Nonlinear power spectrum D2(k)interpreted by the halo model One halo term Two halo term Peacock (2002)

17. Power spectrum of the IR background from dusty galaxies Takeuchi et al. (2005a)

18. Contribution of extragalactic CO lines to the foreground Righi et al. (2008b) Though CO lines do not contribute dominantly to the extragalactic IR background, they are substantially important in the Galactic foreground (e.g., Wright et al. 2001).

19. 2.3 Theoretical development of IR galaxy evolution Now there are various SED models which can reproduce the observed galaxy SEDs very well. However, most of them are focused on reproducing the snapshot of the present-day SEDs, without dealing with the evolution. What we need is a theoretical framework that can treat the evolution from a first principle (ab initio model). To construct such a model, we must understand the complicated interaction of gas, dust and stars in galaxies. There are still only a few studies along this direction. Takeuchi et al. (2003, 2005b, 2010)

20. IR galaxy SED evolution model of a young galaxy Infrared SED (unmixed, rSF=30pc, SFR=1.0Msunyr-1) Takeuchi et al. (2005b)

21. Dust evolution model in the chemical evolution framework SFR Gas Metal production in stars Metal Dust Growth in ISM SN shock destruction Hirashita (1999), Inoue (2003), Asano et al. (2010)

22. Dust evolution model in the chemical evolution framework Asano et al. (2010) The main contributor of dust switches from SNe to AGBs, and finally to the grain growth in the ISM. This is already incorporated in the SED model (Takeuchi et al. 2011).

23. 3. Galactic Foregrounds 3.1 Continuumcomponents WMAP Hinshaw et al. (2007)

24. Classical dust model in the Galactic ISM Désert et al. (1990)

25. Radio Radio wavelength: synchrotron and free-free emission M82 Synchrotron Dust Free-free Condon (1992) Synchrotron from supernova remnants ⇒ Related to star formation activity

26. 3.2 Effect of Galactic CO lines on CMB CO (J = 1→0) map Schäfer et al. (2006) The effect of CO rotational lines have very rarely discussed in the context of CMB foreground, but now we know that it is one of the most important ingredient (cf. Yamamoto-san and Aumont-san’s talks). Synchrotron (simulated)

27. 3.3 Galactic foreground subtraction HI-infrared correlation in the ISM Based on IRAS-COBE. Boulanger et al. (1996)

28. HI-infrared correlation in the ISM Planck Collaboration (2011)

29. Various neutral hydrogen components in the Galactic ISM There are three main categories of Galactic neutral hydrogen components: Local ISM, intermediate velocity clouds (IVCs), and high-velocity clouds (HVCs). IVC: Galactic origin, Z ~ Z☉ HVC: extragalactic origin Z ~ 1/10 Z☉ (e.g., Richter et al. 2001) Signature of depletion is detected in HVCs ⇒existence of dust! However, There is no guarantee that they obey the same HI-to-dust relation with Galactic ISM.

30. Various neutral hydrogen components in the Galactic ISM Wakker et al. (2008)

31. Template construction for subtraction A two-dimensional map-based point-to-point correlation is the standard method to make a template SED to subtract the Galactic foreground (cf. Hattori-san’s talk; Planck Collaboration 2011). (⇔ power-spectrum approach for extragalactic background) This is an endless chase: the better the angular-resolution of a map becomes, the finer ancillary data are requested (e.g., AKARI FIS all-sky diffuse map: Doi-san’s talk)! To ease this situation, state-of-the-art statistical methods are also introduced. But now, we also have to add CO lines to this process. More physically-oriented approach will also help.

32. 3.4 Physico-statistical modeling of Galactic foreground If a theoretical model can predict the statistical nature of the foreground of the ISM, it provides some information on the power spectrum Cℓ (without information of phase) rather than a map. For example, some models of the power spectrum of the ISM fluctuation considering turbulence and magnetic field are proposed (Cho & Lazarian 2010; Fauvet et al. 2011; Hattori-san and Inutsuka-san’s talks). Since it is tightly related to the alignment of dust grains, it is important for polarization studies.

33. 3.5 Incorporating evolutionary framework to the ISM The SEDs of the foreground emission (dust continuum, synchrotron, free-free, and molecular lines) can be modeled in principle. In order to subtract the Galactic foreground, we have to estimate parameters for each component from the data. This was done in a point-to-point manner with ancillary datasets. In the current situation, the parameter estimation will have practically infinite degrees of freedom. Reasonable prior knowledge is necessary! The extragalactic SED modeling technique, especially the evolutionary method would give a good prior as the first guess and integral constraint, since the sum of all components should reproduce a reasonable SED.

34. 4. Summary and Prospects • The CMB foreground consists of Galactic and extragalactic components. The former is anisotropic, and the latter is isotropic. • The extragalactic foreground can be treated statistically, and the power-spectrum approach is powerful. This is dominated by dusty galaxies. To model this, we need accurate knowledge of the evolution of the SFR, SED, and clustering. • The Galactic foreground is anisotropic and structured, currently map-based method is the mainstream of the analysis. But in small scales, in addition to the point-to-point correlation, astrophysical approach is useful and should be developed. • Galaxy evolution approach may help even the Galactic foreground modeling and subtraction.

35. Acknowledgement TTT has been supported by Program for Improvement of Research Environment for Young Researchers from Special Coordination Funds for Promoting Science and Technology commissioned by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan.