The Galaxy The Galaxy Luminosity Luminosity FunctionFunctionSimon Driver

Research School of Astronomy and Astrophysics,

Institute of Advanced Studies,Australian National University

JENAM 2002

OverviewOverview• The Field Luminosity Function - Consensus or

Conflict ?– 2dFGRS, SDSS, ESP, (APM, SSRS2, LCRS, UKST, NOG, CS)– The Millennium Galaxy Catalogue and the GLOBAL LF

• Group and Cluster Luminosity Functions– The Local Group/Sphere– Virgo, Fornax and Coma– Other low-z clusters

• The 2 degree-field galaxy redshift survey cluster and field LF– LF dependencies ?– Spectral type variations between field and cluster ?

• Hubble Space Telescope WFPC2 Observations– Abell 0868 (A morphological dissection)– Abell 2218 (The luminosity profile of giants and dwarfs)

• The Bivariate Brightness Distribution– Overcoming/monitoring selection bias ?– Expanding the toolbox ?

The Schechter Luminosity The Schechter Luminosity FunctionFunction

– Derived from Press-Schechter theory (Schechter 1976)

– * = normalisation parameter– L* = charachteristic turn-over

luminosity– = faint slope parameter

***

***

L

Lde

L

L

L

Ld

L

L L

L

Note: also depends upon thebrightest galaxies

Measuring the Field LFMeasuring the Field LF• Problems:

– Completeness• Imaging• Spectroscopic

– Selection Bias• Imaging• Spectroscopic

– Limited statistics• Bright-end (rare)• Faint-end (dV)

– M*, correlated

N(z)

N(M

)

statistical limit ?

The Field Luminosity Function !The Field Luminosity Function !

GIANTS DWARFS

NU

MB

ER

OF

GA

LA

XIE

S /M

pc^3Large uncertainties

in all parameters ?

x2 at M*

x5 at limit (M=-16)

How do we choosewhich field LF toadopt ?

Constraining the GLOBAL LFConstraining the GLOBAL LF

• The various field LFs predict dramatically differing number-counts:

The Millennium Galaxy The Millennium Galaxy CatalogueCatalogue

• A deep wide survey (36 sq deg, to lim=26 mags/sq arcsec, B~24 mags) overlapping with the 2dF GRS and SDSS-EDR, fully eyeballed.

70 degrees

FIRST THREE POINTINGS

Constraining the GLOBAL LFConstraining the GLOBAL LF• Using the Millennium Galaxy Catalogue (Liske et al

2002) enables * to be recalibrated: 2dFGRS)x1.06, (SDSS)x0.71, *(ESP)x0.90

• But which M* and which faint-end slope to adopt ? (-0.9 > > -1.3 ?)

Constraining the LF without Constraining the LF without z’s ?z’s ?

• For a cosmology, k(z) and e(z) the LF predicts the galaxy number counts.

• The shape of the counts depends on M* & e.g:

• The Millennium Galaxy Catalogue represents a pristine CCD based galaxy count sample (Liske et al 2002) over 36 sq deg to =26 B mags

Deriving the GLOBAL LF from Deriving the GLOBAL LF from counts alone ?counts alone ?

Yes but the constraints are weak:

Require some priors: Adopt mean M* from: 2dFGRS & SDSS redshift surveys:

– Most recent– Largest ( > 100,000s)

=> M*=-19.67 +5 log(h) mags

Fit to counts now yields: h^3/Mpc^3

The GLOBAL LF (h=1)The GLOBAL LF (h=1) Finally we have a consensus between the US, Anglo-

Australian and European measurements plus an independent estimate of

M*(B) (ESP -19.61 0.0179

-1.22) SDSS -19.77 0.0147 -1.26 2dFGRS -19.66 0.0171 -1.21

MGC (Counts) -19.72 0.0158 -1.23

GLOBAL (h=0.65) -20.61 0.0043 -1.23

Now for the group and cluster LFs ---->

The Local GroupThe Local Group

INCOMPLETENESS ?

GLOBAL LF

~50 galaxies only

The Local Sphere (R=10Mpc)The Local Sphere (R=10Mpc)

GLOBAL LF

Incompletenessor turn-over ?

~300 galaxies

VirgoVirgo

Proposed LSBGs based on size

Membership determinedby morphology and size

~400 galaxies

FornaxFornax

Proposed LSBGs basedon background profiling/over-density

~300 galaxies

Membership based onmorphological appearancealthough criticised as excluding dwarf spirals etc

ComaComa

COREREGION

PURE BACKGROUNDSUBTRACTION

~2000 galaxies

Combined Nearby Cluster LFCombined Nearby Cluster LF

• Straight sum of all three clusters to improve statistics

• Overall cluster LF only discrepant at M > -16 where field LF invalid

• Conclude:GLOBAL FIELD LF and GLOBAL CLUSTER LF identical=> STRONG INFALL ?

The 2dFGRSThe 2dFGRSClusters in the 2dFGRSCan we confirm the universalityfrom within the 2dFGRS data ? (de Propris 2002)

• -many clusters• -spectroscopic

selection• -identical biases• -faint mag limit

The cluster sampleThe cluster sample• 60 clusters with z <

0.11 and >40 spectroscopic members with high completeness.

• Composite LF's are computed, each cluster normalized to N(M<-19) and the number of clusters contributing to each bin weighted 1/Nclus.

• Adopt a single k-correction, valid for the E/S0 types that dominate the cluster.

• Completeness corrections assume no bias for/against cluster members.

The overall cluster LFThe overall cluster LFM* = -19.93

0.07 = -1.25

0.03

Cluster and field LFs are Cluster and field LFs are identicalidentical!!!!

Cluster:M* = -19.93 0.07 = -1.25 0.03

Field:M* = -19.79 0.04 = -1.19 0.01

LFs and richness/velocity LFs and richness/velocity dispersiondispersion

M* = -20.01 = -1.27

M* = -19.94 = -1.26

M* = -19.93 = -1.18

M* = -19.89 = -1.20

M* 0.1 , 0.05

Low

High

Poor

Rich

LFs and cluster structureLFs and cluster structure

M* = -19.92 = -1.22

M* = -19.99 = -1.26

M* = -20.03 = -1.43

M* = -19.90 = -1.26

No substructure

Substructure

B-M > II

B-M < II

Cluster LFs - inner Cluster LFs - inner vsvs outer outer regionsregions

M* = -20.09 = -1.29

M* = -19.93 = -1.32

R>300kpc

R<300kpc

Only global variation found is for inner and outer regions:

Intermediate dip reminiscent of that seen in Coma

Spectral and morphological Spectral and morphological typestypes

• Spectral types from principal component analysis parameter

correlates strongly with H EW (i.e. SFR)

correlates weakly with morphological type - can only distinguish E/S0/Sa & Sb/Scd/Im

• The distribution of differs between the field and clusters:– more low- (low SFR)

types in clusters

– more high- (high SFR) types in field

Cluster & field LFs by spectral Cluster & field LFs by spectral typetype

M*: type 1 is 0.5 mag brighter than field; types 2 and 3+4 are within 0.2 mag.

: all types have steeper faint ends in clusters than in field!

Background Subtraction Method Background Subtraction Method (Driver et al 1998)(Driver et al 1998)

SIMULATED DATA

FIELD

CLUSTER

RECOVEREDLUMINOSITYFUNCTION

VALID FORRICHNESS >2CLUSTERSIN GOODSEEING < 1’’

Cluster cores via Background Cluster cores via Background subtractionsubtraction

• Driver et al 1998 - 7 Abell clusters - variations seen in core regions.

• See also:– Lopez-Cruz et al (1997)– Paolillo et al 2001

However variations MAY be partly due to cosmic variance along the cluster sight-line (Valotto et al 2000)

The dwarf-density relationThe dwarf-density relation

• Dwarf-to-giant ratio a better discriminant than

• The DGR rises towards the core• Substantial scatter at core• Consistency at low density

– comparable to the field

)5.195.24(

)5.165.19(

R

R

M

MDGR

COMA (Various)

DRIVER et al 1998

Lopez-Cruz et al 1997

A2218 Mosaic - Luminosity A2218 Mosaic - Luminosity profilesprofiles

The deep WFPC2 mosaic (Archival Data)- 22 pointings- F606W filter- 0.2 deg (1.4 Mpc/h)- 12 drizzled 700 sec exposures per pointing (8400secs)- Probes LF to M(F606W) = -14

1.4 Mpc/h

The Inner and Outer A2218 LFThe Inner and Outer A2218 LF

• Overall LF: M*(F606W) = -20.4,

• Inner LF:

• Outer LF:

The A2218 galaxy profileThe A2218 galaxy profile

• DGR profile of A2218 follows Phillipps et al 2000

• Higher DGR in core• Smooth transition

• Profile of giants steep• Profile of intermediate shallow• Profile of dwarfs flat

A2218 - Morphology Radius A2218 - Morphology Radius relation relation

A868 A Morphological A868 A Morphological DissectionDissection

• A868 initially showed a steep upturn via background subtraction

• z=0.15, BM=II-III, R=2• 24 orbits in F606W

tilled to provide continuous coverageCORE

Sub-Clump

A868 Morphological A868 Morphological ClassificationClassification

• Morphological classification by Artifical Neural Networks into: stars, E/S0s, Sabcs, Sd/Irrs

• Identical analysis performed on: HDFN+HDFS+53W02 for field reference

• Millennium Galaxy Catalogue classified using identical ANN classifier to provide very bright counts

• Statistical field subtraction to extract overall and morphological LFs

STARS E/S0s Sabcs Sd/Irrs

16.5

17.5

18.5

19.5

20.5

21.5

22.5

23.5

A868 Number-CountsA868 Number-Counts

A868 Morphological LFsA868 Morphological LFs

COMBINEDLF(DIPPING)

GLOBAL LF

M*=-20.14 =+0.51 = 41.2

M*=-16.6 =-1.14 = 86.0

M*=-20.50 =-1.16 = 14.8

SummarySummary• Consensus now reached on the GLOBAL LF (=-1.23)• Overall cluster LF identical to the GLOBAL LF to M = -

16– Significant recent infall from field to cluster– Cluster haloes mostly inert

• LSBGs may dominate at M > -14– Implications for field LF ?

• Cluster cores deviate from the GLOBAL LF (intermediate dip)– Evolutionary process at work in cluster core only– Core LF characterised by an overdensity of E/S0s AND a steeper faint-

end• implies two process (Sabc --> S0, Sd/Irr --> dE ?) • implies morphology-density relation

• Cluster LF dominated by eta type 1’s– Star-formation inhibited throughout cluster halo during infall

• Radial profile of giants steeper than dwarfs– Implies luminosity-density relation as seen by Phillipps et al 1998

The BBD: A new methodologyThe BBD: A new methodology

• Surface brightness versus magnitude– Quantitative– Physical basis ? (SB -> ang. Mom., mag -> mass)