1 / 19

Island Universes: Structure and Evolution of Disk Galaxies

Island Universes: Structure and Evolution of Disk Galaxies. Early career: radio continuum work Late 70’s: focus on optical data Key contributions to our understanding of disk galaxies: Truncation at ~4 scale-lengths Constant vertical scale-height

palmer-mcfarland
Download Presentation

Island Universes: Structure and Evolution of Disk Galaxies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Island Universes: Structure and Evolution of Disk Galaxies

  2. Early career: radio continuum work Late 70’s: focus on optical data Key contributions to our understanding of disk galaxies: Truncation at ~4 scale-lengths Constant vertical scale-height Pioneering stellar kinematics Supervision of number of high-quality PhD theses Major influence on development of astronomy on (inter)national level In the footsteps of Kapteyn

  3. A foray into statistics

  4. This Conference • Many new (and some old) results on disk galaxies • Disk galaxies are quite complex ‘Island Universes’ • They are key to galaxy formation process • Significant challenge to theory • Brief summary restricted to some highlights • Structure and properties of stellar disks • Thick disks, bulges, bars, peanuts & other components • Expanding horizons: panchromatic surveys to high z • Outlook

  5. Stellar Disks • Gospel by Freeman (1970) and by van der Kruit & Searle (1981-2) re-addressed and extended • Three types of surface brightness profile (Pohlen) • Pure exponential, sometimes to 9 disk scale-lengths • Double exponential, like vdK+S truncation (Freeman II) • Idem, but outer slope shallower than inner one • Ratio of scale lengths constant out to z~1(Perez) • Studies of ~face-on and edge-on disks disagree? • Fractions of three different types need to be checked • Try to do this in much larger samples (SDSS/MGC)

  6. Outer Regions • Heroic star counts in M31 (Ferguson/Guhathakurta) • Very extended structure (>50 kpc) • Disk or metal-poor halo? • Spectroscopy: kinematics, [Fe/H] • UV & H evidence for faint outer disks (Zaritsky) • Origin of these components? • Star formation threshold? • Is there a link with presence of HI warp or flare? • Origin of warps most likely connected to torque caused by local cosmic inflow pattern (Binney)

  7. Dark halos, kinematics, and M/L • HI studies of dark halo now ‘mature’ • Some work seems stalled in ‘cusp wars’: time to refocus • Key development: determine (M/L) of disk • Measure vertical velocity dispersion • Breaks the degeneracy between stellar vs halo mass • Builds on Piet’s early work, followed by Bottema • IFU spectroscopy can constrain shape of velocity ellipsoid and value of (M/L) (Verheyen/Bershady) • Compare with (M/L) from colors/linestrengths • Sets limits on IMF (de Jong/Bell) • Specific angular momentum content of halo (Kassin)

  8. Other Components • Classical picture of thin disk + R1/4-bulge embedded in dark halo is now more complicated • Thick disks are ubiquitous • Majority of disk galaxies are barred (~70%) • Much confusion about the central regions: • Classical and ‘pseudo’-bulges, bars and peanuts • Neutral and ionized gas in halos • Not discussed: central black holes in disks

  9. Thick disks • Most disk galaxies have additional, thick, disk (Yoachim/Dalcanton) • Modest mass fraction, but increases below vc~120 km/s • Some counter-rotate:  external origin • Heavier counter-rotating disks seen in S0s • [/Fe] vs [Fe/H] in MW thick disk  it cannot have formed by accretion of small stellar lumps (Venn) • Origin in gas-rich merger (cf Sommer-Larsen)

  10. Bars • Bar influences dynamics and star formation activity • They drive gas to the center (and so do interactions) • This can trigger starburst, sometimes in ring • Bars slow down and change shape due to friction by halo (Sellwood/Athanassoula) • Consistent with ~constant bar fraction since z~1? (Bell) • Bars do not transform into bulges today (Elmegreen) • End-on peanut looks like bulge (Bureau)

  11. Impostor Bulges? • Traditional bulges may be mix of structures • Some classical bulges similar to E/S0s • Nearly 50% of bulges have exponential profiles, and may be disks; these all have central star clusters • In many cases the central bar may be the bulge; it may have an embedded central disk (cf Milky Way) • Not clear at all which of these have central black hole • Some classification schemes tied to prejudices about formation scenario • Definition of ‘pseudo-bulge’ needs further clarification

  12. Extended extraplanar gas HI (Fraternali) H and X-rays (Dettmar) Properties consistent with theory of fountains/winds Not evident that in situ star formation is needed in halo Effect of run-away stars to be investigated Baryonic Halo HI in NGC 891 Oosterloo, Fraternali, Sancisi 2005

  13. The Milky Way • Piet measured scale-length of MW disk • Based on Pioneer 10 data • This is Paper V in the legendary series (but vdK only) • Generated follow-up work to measure run of  with R • Milky Way received relatively little attention here • Kinematics of disk stars (Binney) • Stellar halo not formed by dissolving present-day like dSph’s, dIrr, of LMC-clones (Venn) • Comparison of MW properties with simulations: key test of formation paradigm (Bullock/Sommer-Larsen)

  14. Panchromatic Surveys • Beautiful multi-wavelength high-resolution imaging • From UV (GALEX) via HST to Spitzer and HI/CO • Kennicutt, Regan, Murphy/Braun et al. • Systematic representative surveys (e.g. SINGS) • Separation of stars and different types of dust • Still to be linked with NIR extinction method (Alves) • Get full SED’s, star formation rates, CR structure • Images constrain lifetime of embedded phase of massive star formation • Key challenge is to model all this in detail (Dopita)

  15. 0.15 mm 0.4-0.8 mm 1.2-2.2 mm 3.6 mm 8.0 mm 24 mm 70 mm 160 mm

  16. WPFC2/F336W/F555W/F675W Integral-field Spectroscopy NGC 7742 (Falcon-Barroso)

  17. Studies to high redshift • Much work on properties of galaxies to high z • Be careful with selection biases (Vogt) • Most objects found: progenitors of present-day spheroids (Pettini) • Disks detected to z~2 (Abraham/Kassin) • DLA hosts resemble local galaxies with HI (Zwaan) • Inside-out formation (Bell/Trujillo) • Evolution of population  evolution of objects (Bell) • Metallicity determinations to z~3 • Much progress for disks (Kewley) • Also for the ISM, via DLA’s (Fall) • Beware of selection effects

  18. The Future • Studies of resolved stellar populations in MW and Local Group galaxies hold much promise • Panchromatic surveys complemented with IFU spectroscopy in optical and IR, to high z • Theoretical models & simulations need to fit observations in detail; this is within reach • Herschel, ALMA, GAIA and JWST to come • Much scope for more pioneering work by Piet

More Related