Elizabeth Cooke

Elizabeth Cooke
In collaboration with Nina Hatch & Stuart Muldrew
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Cluster galaxies differ from field galaxies
In the local universe:
◦ Redder (e.g. Bamford et al., 2009)
◦ Predominantly early types
(e.g. Dressler et al., 1980)
◦ Older ellipticals
(e.g. Rettura et al., 2010)
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At high redshift (z > 1.5):
◦ Larger (e.g. Papovich et al., 2012)
◦ More massive (e.g. Steidel et al., 2005)
◦ Redder (e.g. Hayashi et al., 2012)
High z (proto)clusters can
help constrain what
processes are going on
Elizabeth Cooke
Abell 1689
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No difference in sSFR
between (proto)cluster
and field
Used K band flux to
estimate masses
Av ∝ M
Do these results change
with more robust
measures of mass/Av?
From Koyama et al., 2013a
Elizabeth Cooke
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Study field around HzRG MRC2104-242
◦ 2.5′ x 2.5′
◦ z = 2.49
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Study properties of any galaxies with respect to
environment at this redshift
MRC2104
A = 7.09 sq arcmin
Elizabeth Cooke
COSMOS
UDS
A =170.4 sq arcmin (total)
GOODS-S
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NB survey
◦ VLT: ISAAC
◦ NB λcen = 2.29μm
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VLT HAWK-I: K, J, H
◦ (rest frame optical)
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Gemini GMOS: g, z
◦ (rest frame UV)
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IRAC: 3.6μm, 4.5μm
◦ (rest frame IR)
Elizabeth Cooke
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Ks-NB colour vs NB magnitude
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Σ>2
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Remove low-z
contaminants
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(B-z) – (z-K) > -0.2
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EAzY
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zphot > 1.4
◦ Selection in SFR
(Daddi et al., 2004)
(Brammer, van Dokkum & Coppi, 2008, ApJ)
Elizabeth Cooke
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FAST
(Kriek et al., 2009, ApJ)
SEDs robust
measure of mass
Line emission not
accounted for
Constrained
redshift to width
of NB filter
Elizabeth Cooke
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Spatial density of 8.6 x control field density
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Overdensity of same order as other protoclusters
(e.g. Hayashi et al., 2012; Hatch et al., 2011b; Kurk et al., 2004)
MRC2104
COSMOS
UDS
22 sources
60 sources (total)
A = 7.09 sq arcmin
A =170.4 sq arcmin (total)
Elizabeth Cooke
GOODS-S
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Masses from SED fit
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KS = 3x10-7
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Consistent with
previous
surveys
◦ Steidel et al., 2005
◦ Hatch et al., 2011b
◦ Koyama et al., 2013
Elizabeth Cooke
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Uncorrected for dust absorption
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KS = 0.66
Elizabeth Cooke
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E(B-V) = 0.25(B-z + 0.1)AB
(Daddi et al., 2004)
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No B/z signal:
◦ Use convolved
SED values
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KS = 0.1
Elizabeth Cooke
Field
LIR (x 1010 Lʘ)
MRC2104
COSMOS
UDS
GOODS-S
5.8
0.8
1.6
0.4
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Median stacks of Hα
emitters: rest frame ~7 μm
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More hidden star formation?
Elizabeth Cooke
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Corrected using Av from B-z colour
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KS = 0.02
Elizabeth Cooke
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Corrected for
extinction
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Same sSFRno starbursts
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No clear
relation
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MRC2104
galaxies more
massive/star
forming
Elizabeth Cooke
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No difference in sSFR
Different mass
distributions
8.6 x density of
control field
Elizabeth Cooke
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~40 x control field at M > 1010.5 Mʘ
Lack of lowmass sources
Detect in SFR,
not mass
Similar for SFR
Elizabeth Cooke
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Not forming
stars?
Dust?
Mass function
turning over?
Mass
segregation?
Elizabeth Cooke
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Not forming
stars?
Dust?
Mass function
turning over?
Mass
segregation?
Elizabeth Cooke
From Rudnick et al., 2012
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Not forming
stars?
Dust?
Mass function
turning over?
Mass
segregation?
Elizabeth Cooke
Circle = 10 Mpc diameter, comoving
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MRC2104-242 field is overdense
Protocluster galaxies more massive and more
star forming
Lack of lower mass objects
◦
◦
◦
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Star formation shut off?
Extincted?
Mass function turning over?
Mass segregation?
Elizabeth Cooke