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Bulgeless Galaxies and their Angular Momentum Problem

Bulgeless Galaxies and their Angular Momentum Problem. Elena D’Onghia. Max-Planck Institute (MPE, Garching) Observatory University (Munich). with. Andreas Burkert. Observatory University (Munich). Understanding the formation of disk galaxies is linked to understanding the origin of its

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Bulgeless Galaxies and their Angular Momentum Problem

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  1. Bulgeless Galaxies and their Angular Momentum Problem Elena D’Onghia Max-Planck Institute (MPE, Garching) Observatory University (Munich) with Andreas Burkert Observatory University (Munich)

  2. Understanding the formation of disk galaxies is linked to understanding the origin of its angular momentum General Theory (Fall & Efstathiou 1980): Angular momentum origins from tidal torques Gas had the same specific angular momentum of dark matter halos today Infalling gas conserves its specific angular momentum (Mestel 1963) Galactic disks with correct sizes!!!!!

  3. SEMI-ANALYTIC MODELS + General Theory hierarchical structure formation Tidal torques impart angular momentum to dark matter halos Energy Mass Spin parameter Galactic disks with correct sizes!!!!!

  4. However hydrodynamical N-body simulations of disk Formation in CDM yield disks too small Navarro & Steinmetz 2000 Abadi et al. 2003 The Angular Momentum Catastrophe of the gas !!

  5. D´Onghia, Murante & Burkert 2004, in preparation

  6. Simulations show that galaxies are built up by merging of baryonic subclump rather than smooth accretion of gas. Much of the gas cools at the centre of subhalos and spirals toward the centre of parent halo, tranferring its orbital angular momentum to the dark matter Better fits to real disks if Stellar FEEDBACK is included (Sommer-Larsen et al. 2003; Abadi et al. 2003) Too dense and too massive bulges than real galaxies!!

  7. Vitvitska, Klypin et al. 2002, ApJ, 581, 799 Haloes that have had recent major mergers have larger Spin values!

  8. We focus on this question: Is the halo merging history playing a role in building small disks?

  9. STRATEGY We build up a set of CDM only simulations exploring the spin parameter of halos formed through various Merging history (we use Gadget code) For each halo: We identify the last major merger Bulge/(Bulge+Disk) Spin parameter at z=0

  10. D´Onghia & Burkert, ApJL submitted astro-ph/0402504

  11. in BBS sample of bulgeless galaxies estimated for disks based on 1000 Sb-Sdm galaxies (de Jong & Lacey 2000)

  12. Net Result: halos dominated by minor merger accretion from z=3 to z=0 acquired by tidal torques only 2% of the angular momentum for their rotational support, whereas bulgeless galaxies acquired 6-7% Hard to form bulgeless galaxies POSSIBLE SOLUTIONS? Modification to the nature of the dark matter? Warm dark matter or Self-Interacting dark matter ? NO Feedback from early structure formation , e.g. from small sublumps before they merge? However, feedback processes are unlikely to provide the additional specific angular momentum for bulgeless galaxies

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