Issue |
A&A
Volume 386, Number 2, May I 2002
|
|
---|---|---|
Page(s) | 446 - 455 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20020259 | |
Published online | 15 May 2002 |
Photometric redshifts from evolutionary synthesis with PÉGASE: The code Z-PEG and the
age constraint
1
Institut d'Astrophysique de Paris, 98 bis, boulevard Arago, 75014 Paris, France
2
Institut d'Astrophysique Spatiale, Bât. 121, Université Paris XI, 91405 Orsay, France
Corresponding author: D. Le Borgne, leborgne@iap.fr
Received:
19
November
2001
Accepted:
8
February
2002
Photometric redshifts are estimated on the basis of
template scenarios with the help of the code Z-PEG, an extension of the
galaxy evolution model PÉGASE.2 and available on
the PÉGASE web site. The spectral energy distribution (SED) templates are
computed for nine spectral types including starburst, irregular,
spiral and elliptical. Dust, extinction and metal effects
are coherently taken into account, depending on evolution scenarios.
The sensitivity of results to adding
near-infrared colors and IGM absorption is analyzed. A comparison
with results of other models without evolution measures the evolution factor which
systematically increases the estimated photometric redshift values by
for
. Moreover we systematically check that
the evolution scenarios match observational standard templates
of nearby galaxies, implying an age constraint of the stellar
population at
for each type. The respect of this
constraint makes it possible to significantly improve the accuracy of photometric
redshifts by decreasing the well-known degeneracy problem. The
method is applied to the HDF-N sample (see in Fernández-Soto et al.
1999). From fits on SED templates by a
-minimization procedure, not
only is the photometric redshift derived but also the corresponding
spectral type and the formation redshift
when stars first formed.
Early epochs
of galaxy formation
are found from this new method and results
are compared to faint galaxy count interpretations. The new tool is
available at: http://www.iap.fr/pegase
Key words: galaxies: distances and redshifts, evolution / methods: data analysis / techniques: photometric
© ESO, 2002
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.