the galaxy luminosity function simon driver research school of astronomy and astrophysics, institute...
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The Galaxy The Galaxy Luminosity Luminosity FunctionFunctionSimon Driver
Research School of Astronomy and Astrophysics,
Institute of Advanced Studies,Australian National University
JENAM 2002
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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 ?
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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
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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 ?
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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 ?
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Constraining the GLOBAL LFConstraining the GLOBAL LF
• The various field LFs predict dramatically differing number-counts:
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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
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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 ?)
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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
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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
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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 ---->
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The Local GroupThe Local Group
INCOMPLETENESS ?
GLOBAL LF
~50 galaxies only
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The Local Sphere (R=10Mpc)The Local Sphere (R=10Mpc)
GLOBAL LF
Incompletenessor turn-over ?
~300 galaxies
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VirgoVirgo
Proposed LSBGs based on size
Membership determinedby morphology and size
~400 galaxies
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FornaxFornax
Proposed LSBGs basedon background profiling/over-density
~300 galaxies
Membership based onmorphological appearancealthough criticised as excluding dwarf spirals etc
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ComaComa
COREREGION
PURE BACKGROUNDSUBTRACTION
~2000 galaxies
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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 ?
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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
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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.
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The overall cluster LFThe overall cluster LFM* = -19.93
0.07 = -1.25
0.03
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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
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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
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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
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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
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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
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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!
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Background Subtraction Method Background Subtraction Method (Driver et al 1998)(Driver et al 1998)
SIMULATED DATA
FIELD
CLUSTER
RECOVEREDLUMINOSITYFUNCTION
VALID FORRICHNESS >2CLUSTERSIN GOODSEEING < 1’’
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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)
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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
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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
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The Inner and Outer A2218 LFThe Inner and Outer A2218 LF
• Overall LF: M*(F606W) = -20.4,
• Inner LF:
• Outer LF:
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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
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A2218 - Morphology Radius A2218 - Morphology Radius relation relation
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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
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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
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A868 Number-CountsA868 Number-Counts
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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
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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
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The BBD: A new methodologyThe BBD: A new methodology
• Surface brightness versus magnitude– Quantitative– Physical basis ? (SB -> ang. Mom., mag -> mass)