Models of Galaxy Number Counts in the
Groth-Westphal Strip of the GOYA Survey
.
gotzon
18-1-95
.
Prieto M.,
1,2
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3
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, Eliche C., , Garcia-Dabo C.E., , Balcells M., , Cristobal D., , Erwin P.,Dominguez L., Dabreu D.
(1) Instituto de Astrofisica de Canarias (2) Universidad de La Laguna (3) Gran Telescopio de Canarias
RESULTS
ABSTRACT
We have used the traditional approach of tracing back the
evolution of the population of nearby galaxies to get
information on galaxy evolution and cosmology from the
deep optical and IR counts of galaxies in the GrothWestphal-Strip of the GOYA survey.
We have used the ncmod code from Gardner (1998) to build
galaxy number count and color distribution predictions and
compare with our data. The main ingredients of the model
are the local Luminosity function, the Spectral Energy
distribution of the local galaxies, their evolution and the
geometry of the Universe.
!We have found that Ë-dominated flat universe with
Ùm~0.3 gives the best fit to our optical data, and a modest
number evolution with nu~<1 is also permite. To fit near IR
data, we need to divide the Elliptical population in giants and
dwar
!
!INTRODUCCION
!
!A study of the HDF galaxy counts performed by Pozzetti et
al. 1998, found that a simple model of pure luminosity
evolution (PLE), in which galaxies evolve passively due to
star formation histories without mergers (number
evolution), gives a reasonable fit to the HDF optical counts
when an open universe with Ùm=0.1 is assumed. The
Einstein-de Sitter(EdS) universe, Ùm=1, underpredicts the
observed galaxy counts at faint magnitudes in a PLE, but
can reproduce it with a simple model of merger.
This degenerancy between the effects of galaxy evolution
and cosmology has been a major problem in using galaxy
number counts to determine the geometry of the universe.
However, Totani & Yoshii 2000 after correcting the model
from select effects found that a PLE model in a
Ë-dominated flat universe with Ùm~0.2 gives the best fit
to the HDF data, and a modest number evolution with
Þ~<1 is also permited. In the frame work of a SAM, Totani
et al. 2001a found similar results. To fit the near IR Subaru
Deep field data he needs to divide the E in giants and
dwarfs, Totani et al. 2001b.
Texto
Ë dominated univ.
Figure 1. Galaxy number count model in a
Ë–dominated universe with h=0.7, Ùm=0.3,
Ùl=0.7. The solid line is the prediction for all
galaxy types, and the red points are our data.
Figure 2. Galaxy number counts data for
Standard Model in K, U and B data. The
dashed lines are the models for a flat Einstein
de Sitter universe, h=0.5, Ùm=1.
Itexto
Here we have a new set of data, code, SEDs and LF and
we try to fit a number count model to the optical and near
IR data of the GrothWestphal Strip field of the GOYA
survey to put new constraint to the galaxy evolution.
THE DATA
The optical galaxy number counts are in B and U filters from a field that
comprises a ~900 arcmin2 area of sky, and which covers the Groth-Westphal
Strip (GWS)(Eliche et al.2004). The 50% limiting magnitudes are 24.8 in U and
25.5 in B in the Vega system. The V and I filters are from the HST, which limiting
magnitudes are 24.5 and 23.5 for SN=10. The near IR number counts are in K
band from the area that cover the GWS, ~18 arcmin2.(Cristobal et al. 2003). The
50% limiting magnitudes in the Ks filter is 21. Both set of data are corrected of
the cosmological dimming of the surface brightness of galaxies, under the
observational conditions employed in each frame.
The model considers the effects of absortion by dust internal, and merging is
simulated by the formula proposed by Rocca-Volmerange & Guiderdoni (1990)
or alternatively, to avoid the overenthusiastic deblending in the object detection
routine, by Broadhurst et al. 1992
THE MODEL
We have used the MDLF obtained by Nakamura et al. 2003
from about 1500 bright galaxies of the Sloan Digital Sky
Survey northern equatorial strips. The limiting magnitud is
r*(AB)<=15.9 mag. after Galactic
Extinction Correction,
this is r*(Vega)<=15.7 or B(Vega)<=17.3mag. This limits
allows to include the local Blue Compact Dwarf Galaxies
population, since their have a B~=12-17mag. In Table 1 we
give the Schechter parameters of this MDLF in the filter r* of
the SDSS, with M* in the Vega system magnitudes and for
Ho=70 km-sMpc-1. The SEDs of the galaxies have been
taken from galaxy isochrone synthesis spectral evolution
library (GISSEL96) model (Bruzual & Charlo98). We have
simulated each type of galaxy as indicated in Table2.
Figura 3. Comparison with other authors. The optical are
anly CCD data.
Model with gE and dE
CONCLUSIONS
Our optical data are compatible with a Lambda dominate
universe with Omegam approx. 0.3 and with a mild rate of
merging.
I Table 1. Morphological Dependent Luminosity Function
To explain the change of the slope in K number counts, we
have investigated the approach of dividing the Es in giants
and dwarfs, but it does not solve completely the problem.
The Schechter parameters of the MDLF in the filter r*
of the SDSS, with M* in the Vega magnitud system
and for Ho=70 km s-1 Mpc-1
LF Parameters
M*(r*)-5logh
a
Ö*(0.001h^3 Mpc-3)
E-S0
-21.53
-00.83
01.61
S0-Sab
-21.08
-01.15
03.26
Sbc-Sd
-21.08
-00.71
01.48
The colour distribution of the model fails to explain the red
side of the colour distribution data. New ingredients are
necessary to explain both discrepancies.
Im
-20.10
-01.9
00.37
Table 2. SPECTRAL ENERGY DISTRIBUTION (SED)
The SEDs of the galaxies have been taken from galaxy
isochrone synthesis spectral evolution library
(GISSEL96) model (Bruzual & Charlot 1998).
type
RSF
E-S0
SSP
S0-Sab exp.
Sbc-Sd exp.
Im
cont.
e-folding times
------4 Gyr
7 Gyr
--
metalicity
solar
solar
2/5 solar
1/5 solar
IMF
Salpeter
Salpeter
Salpeter
Salpeter
Figura 4. The gE have a gaussian LF, and the dE a
Schechter one, Chiba and Yoshii, 1999. The solid lines
represent the model without merger, the dashed lines with
merger and the point lines with mild merger.
References
Figure 5. F606W-F814W color distribution data for the
model with division of Es. The red lines are the model
without merger and the green one with merger. T
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