Transcript The SAURON Survey - University of Groningen

Island Universes: Structure
and Evolution of Disk Galaxies
In the footsteps of Kapteyn
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Early career: radio continuum work
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Late 70’s: focus on optical data
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Key contributions to our
understanding of disk galaxies:
– Truncation at ~4 scale-lengths
– Constant vertical scale-height
– Pioneering stellar kinematics
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Supervision of number of
high-quality PhD theses
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Major influence on development of
astronomy on (inter)national level
A foray
into
statistics
This Conference
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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
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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
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Outlook
Stellar Disks
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Gospel by Freeman (1970) and by van der Kruit &
Searle (1981-2) re-addressed and extended
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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
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Ratio of scale lengths constant out to z~1 (Perez)
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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)
Outer Regions
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Heroic star counts in M31
(Ferguson/Guhathakurta)
– Very extended structure (>50 kpc)
– Disk or metal-poor halo?
– Spectroscopy: kinematics, [Fe/H]
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UV & H evidence for faint
outer disks (Zaritsky)
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Origin of these components?
– Star formation threshold?
– Is there a link with presence of HI warp or flare?
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Origin of warps most likely connected to torque
caused by local cosmic inflow pattern (Binney)
Dark halos, kinematics, and M/L
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HI studies of dark halo now ‘mature’
– Some work seems stalled in ‘cusp wars’: time to refocus
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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
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IFU spectroscopy can constrain shape of velocity
ellipsoid and value of (M/L) (Verheyen/Bershady)
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Compare with (M/L) from colors/linestrengths
– Sets limits on IMF (de Jong/Bell)
– Specific angular momentum content of halo (Kassin)
Other Components
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Classical picture of thin disk + R1/4-bulge
embedded in dark halo is now more complicated
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Thick disks are ubiquitous
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Majority of disk galaxies are barred (~70%)
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Much confusion about the central regions:
– Classical and ‘pseudo’-bulges, bars and peanuts
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Neutral and ionized gas in halos
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Not discussed: central black holes in disks
Thick disks
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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
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[/Fe] vs [Fe/H] in MW thick disk  it cannot have
formed by accretion of small stellar lumps (Venn)
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Origin in gas-rich merger (cf Sommer-Larsen)
Bars
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Bar influences dynamics and star formation activity
– They drive gas to the center (and so do interactions)
– This can trigger starburst, sometimes in ring
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Bars slow down and change shape due to friction
by halo (Sellwood/Athanassoula)
– Consistent with ~constant bar fraction since z~1? (Bell)
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Bars do not transform into bulges today (Elmegreen)
– End-on peanut looks like bulge (Bureau)
Impostor Bulges?
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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
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Some classification schemes tied to prejudices
about formation scenario
– Definition of ‘pseudo-bulge’ needs further clarification
Baryonic Halo
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Extended extraplanar gas HI in NGC 891
– HI (Fraternali)
– H and X-rays (Dettmar)
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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
Oosterloo, Fraternali, Sancisi 2005
The Milky Way
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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
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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)
Panchromatic Surveys
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Beautiful multi-wavelength high-resolution imaging
– From UV (GALEX) via HST to Spitzer and HI/CO
– Kennicutt, Regan, Murphy/Braun et al.
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Systematic representative surveys (e.g. SINGS)
–
–
–
–
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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)
0.15 mm
8.0 mm
0.4-0.8 mm
24 mm
1.2-2.2 mm
70 mm
3.6 mm
160 mm
Integral-field Spectroscopy
NGC 7742
WPFC2/F336W/F555W/F675W
(Falcon-Barroso)
Studies to high redshift
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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)
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Metallicity determinations to z~3
– Much progress for disks (Kewley)
– Also for the ISM, via DLA’s (Fall)
– Beware of selection effects
The Future
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Studies of resolved stellar populations in MW
and Local Group galaxies hold much promise
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Panchromatic surveys complemented with IFU
spectroscopy in optical and IR, to high z
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Theoretical models & simulations need to fit
observations in detail; this is within reach
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Herschel, ALMA, GAIA and JWST to come
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Much scope for more pioneering work by Piet