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X-rays from disk galaxy halos

X-rays from disk galaxy halos. - t esting galaxy formation. Jesper Rasmussen ( Univ. of Copenhagen, Denmark ) + Jesper Sommer-Larsen, Kristian Pedersen (Copenhagen), Sune Toft (Yale), Richard Bower (Durham, UK), Andy Benson (Oxford, UK).

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X-rays from disk galaxy halos

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  1. X-rays from disk galaxy halos - testing galaxy formation Jesper Rasmussen(Univ. of Copenhagen, Denmark) + Jesper Sommer-Larsen, Kristian Pedersen (Copenhagen), Sune Toft (Yale), Richard Bower (Durham, UK), Andy Benson (Oxford, UK)

  2. Theory + sim’s: Disk galaxies should possess hot, gaseous halos. Cooling halo gas emits X-rays  signature of active (gas-)disk assembly. LX Vc5 Background Cosmological simulations of galaxy formation (Toft, Rasmussen, Sommer-Larsen, Pedersen 2002): > 95% of LXinside ~20 kpc

  3. NGC2841 (ROSAT) : 1. Direct searches: Benson et al. (2000): ROSAT analysis of NGC2841 (D = 13.9 Mpc, Vc = 317 km/s)LX< 3.7 x 1040 erg/s (3σ). Previous work 2. Other works: NGC4631 (Wang et al. 2001) – hot halo likely fueled by disk outflows. NGC891 (Bregman & Pildis 1994) – probably something similar (Strickland et al. 2004) Milky Way (e.g. Wolfire et al. 1995, Pietz et al. 1998, Kuntz & Snowden 2000) – some evidence for a hot halo, with LX~ few times 1039 erg/s.

  4. Theory + sim’s: Disk galaxies should possess hot, gaseous halos. Cooling halo gas emits X-rays  signature of active (gas-)disk assembly. LX Vc5 Background Cosmological simulations of galaxy formation (Toft, Rasmussen, Sommer-Larsen, Pedersen 2002): Hot halos not yet observed  testing predictions using (1) More sophisticated simulations + higher resolution (2) Sensitive X-ray data of carefully selected candidates > 95% of LXinside ~20 kpc

  5. Vc ~ 250 km/s Densities, log N: -3.5-3-2cm-3 Temperatures: 104105106K Temperatures: 104105106K (J. Sommer-Larsen + collaborators) 1: Novel simulations Sim’s include: star formation, stellar feedback, radiative cooling, UV radiation field, self-consistent chemical evolution.

  6. 2: X-ray/optical observations NGC5170 NGC5746 Vc = 252 km/s, D = 24 Mpc Vc = 307 km/s, D = 29 Mpc —— 16 arcmin ≈ 100 kpc—— —— 16 arcmin ≈ 140 kpc—— Chandra: 2 x 37 ks XMM: 33 ks (NGC5170 only) Danish 1.54m: 160/120 min Hα (+UBVRI)

  7. An example: NGC1800 45 ks of Chandra/ACIS exposure (Rasmussen, Stevens, Ponman 2004): 0.3-5 keV, adaptively smoothed X-ray/optical overlay D25 (25 mag/arcsec2) ~ 2kpc Extent ≈ 2 kpc, Lx = 1.3 +/- 0.3 x 1038 erg/s Most distant dwarf starburst (D = 7.4 Mpc) with clear detection of diffuse X-rays.

  8. LX Vc5 No detection in annulus Lx < 1038 erg/s (3σ)(assuming T = 0.1 keV, Z = 0.2 Zsun ) A hot halo around NGC1800?

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