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Galaxy Evolution: The Shape of Galactic Stellar Disks
NGC 6118 (ESO VLT VIMOS) NGC 4565 (ESO VLT FORS)

Michael Pohlen
Kapteyn Instituut Rijksuniversiteit Groningen

Ignacio Trujillo (IAC) Peter Erwin (MPE) John Beckman (IAC)
Saleem Zaroubi (RUG) Reynier Peletier (RUG)


My 2 dusty slides (1)
Study distribution of stars to study of galaxy formation and evolution

Problem: There is dust!

NGC 4565 (ESO VLT FORS)


My 2 dusty slides (1)
Study distribution of stars to study of galaxy formation and evolution

Problem: There is dust! My Solution: Try to avoid it!

NGC 4565 (ESO VLT FORS)


My 2 dusty slides (2)
Question: Why are you here?

NGC 4565 (ESO VLT FORS)


My 2 dusty slides (2)
Question: Why are you here?

Answer: how it affects me by e.g. extinction how it can be used to trace gas (gas starformation stars important!) 2) Tell you how the stars are distributed and why
NGC 4565 (ESO VLT FORS)

1) To learn which dust is where and


Outer Disk: New faceon samples



EarlyType (S0Sb) barred + unbarred Sample Diameter and distance limited 66+45 galaxies (UGC, CCD+SDSS)
LateType SDSS Sample: Examples
(Erwin, Beckman & Pohlen 2005, ApJL 626, 81 Erwin, Pohlen, & Beckman, in prep. Aladro, Gutierrez, Erwin, Beckman, & Pohlen, in prep.

LateType (SbSdm) Sample Volume limited sample down to limiting M 98 galaxies (LEDA, SDSS)
(Pohlen & Trujillo 2006, A&A 454, 759)

ab s

two large complementary studies


Type I
r' exp.fit r' band g'band

Outer disk: Classification
Type I : no break (Freeman 1970) Type II : downbending break Type III : upbending break
(Erwin, Beckman & Pohlen 2005, ApJL 626,81) (Pohlen & Trujillo 2006, A&A 454, 759)

Type II

Type III


Type I

Outer disk: Classification
Type I : no break Type II : downbending break Type III : upbending break

Type II

Type III


Star counts
independent method significantly deeper (µeff = 31.5 Vmag/arcsec^2) same shape!

M33 ­ Type II

inner disk (textbook example)

outer disk

(Ferguson et al. 2006, astroph/0601121)


NGC 300 ­ Type I

(BlandHawthorn et al. 2005)

NGC 300
GMOS star counts


M31 ­ Type III

M 31
(Ibata et al. 2005)

INT star counts


Theory: Origin of outer disk structure
Type I: long standing debate about exp. form (but we may have for Type II and Type III) Type II: several models CT: starformation threshold (Kennicutt, 1989; Martin & Kennicutt, 2001; Schaye, 2004) (Elmegreen & Hunter, 2006; Li, Mac Low & Klessen, 2006) OLR: (bar) resonance phenomenon (Debattista et al. 2006) Type III: connection with interactions? star formation? (Elmegreen & Hunter, 2006)


Origin of outer disk structure
Li, Mac Type I: exponential has no physical explLow &ioln en, 2006 anat K ess but we may have for Type II and Type III Elmegreen & Hunter, 2006

Type II: several models CT: starformation threshold (Kennicutt, 1989; Martin & Kennicutt, 2001; Schaye, 2004) (Elmegreen & Hunter, 2006; Li, Mac Low & Klessen, 2006) OLR: (bar) resonance phenomenon (Debattista et al. 2006) Type III: connection with interactions? star formation? (Elmegreen & Hunter, 2006)


Origin of outer disk structure
Type I: exponential has no physical explanation but we may have for Type II and Type III Type II: several models CT: starformation threshold (Kennicutt, 1989; Martin & Kennicutt, 2001; Schaye, 2004) (Elmegreen & Hunter, 2006; Li, Mac Low & Klessen, 2006) OLR: (bar) resonance phenomenon (Debattista et al. 2006) Type III: connection with interactions? star formation? (Elmegreen & Hunter, 2006)


Origin of outer disk structure
Type I: exponential has no physical explanation but we may have for Type II and Type III

Nbody simulations

(edgeon)

D Type II: several models ebattista et al., 2006 CT: starformation threshold o: observed (Ken n:cuttu l19ed ; Martin & Kennicutt, 2001; Schaye, 2004) i , 89 + sim at (Elmegreen & Hunter, 2006; Li, Mac Low & Klessen, 2006) OLR: (bar) resonance phenomenon (Debattista et al. 2006)

(faceon)

Type III: connection with interactions? star formation? (Elmegreen & Hunter, 2006)


Origin of outer disk structure
Type I: exponential has no physical explanation but we may have for Type II and Type III Type II: several models CT: starformation threshold (Kennicutt, 1989; Martin & Kennicutt, 2001; Schaye, 2004) (Elmegreen & Hunter, 2006; Li, Mac Low & Klessen, 2006) OLR: (bar) resonance phenomenon (Debattista et al. 2006) Type III: connection with interactions? star formation? (Elmegreen & Hunter, 2006)


Origin of outer disk structure
Type I: exponential has no physical explanation but we may have for Type II and Type III
Elmegreen & Hunter, 2006

Type II: several models CT: starformation threshold (Kennicutt, 1989; Martin & Kennicutt, 2001; Schaye, 2004) (Elmegreen & Hunter, 2006; Li, Mac Low & Klessen, 2006) OLR: (bar) resonance phenomenon (Debattista et al. 2006) Type III: connection with interactions? star formation? (Elmegreen & Hunter, 2006) more data is needed to decide on origin!


Interpretative Subclassification
to study origin of the breaks Type IIAB morphology different origin

Type IIOLR

Type IICT


Type IIAB

Type II: Subclassification
Type IIAB: Apparent/Asym. Breaks
(Outer Lindblad Resonance) outer rings @23 · bar radius (Buta & Crocker 1993)

Type IIOLR: Resonance Breaks

Radius [arcsec]

Type IICT: Classical Truncation

Type IIOLR

Type IICT

Radius [arcsec]

Radius [arcsec]


Type IIOLR vs. Type IICT
Rbr coincides with visible outer ring Rbr is consistent with outerring

morphology

classification

no bar Rbr is beyond visible outer ring Rbr is at too large radius

Type IIOLR

Type IICT

but * different!
Radius [arcsec]

physically distinct

Radius [arcsec]


Type III: Sub classification
Type IIId Type IIId: disk component Type IIIs: spheroidal component

Type IIId

Type IIIs


Clues: Disk Type vs. Hubble Type
Early types Late types
Pohlen & Trujillo 2006, A&A 454, 759) (Erwin, Beckman & Pohlen 2005, ApJL 626,81

Type I Type IIOLR Type IICT Type III

Hubble Type


Clues: GALEX XUV vs. Type III ?
Gil de Paz et al. 2005


Study of Vertical Structure
may give important constraints

only possible for edgeon galaxies (as N891)
(Dale Cupp/Flynn Haase NOAO/AURA/NSF )


Clues: Vertical Structure
model data: single broken exponential (Type IICT)

real data: flattening of "break"


Clues: Vertical Structure
model data: sin"weakenen exf truncation" gle brok ing o ponential t
Type IICT


Highz galaxies: HST/UDF data


Observational Size Evolution
standard scenario: (e.g. Fall & Efstathiou, 1980) generic consequence insideout growth

observed

corrected

~5 kpc

~13 kpc

(Trujillo&Pohlen, 2005, ApJL, 630, 17)

observed SB evolution

(Barden et al. 2005, GEMS data)


Summary
SB profiles from 2 new faceon samples: Diameter distance limited earlytype galaxies Volume limited latetype galaxies (SDSS) Classification of outer disk: Three basic classes: Type I, Type II, Type III not produced by dust! disk truncations are part of Type II (CT) Interpretive subclassification: Type IICT (starformation), Type IIOLR (resonance) Quest for Origin still ongoing!


The End