134 research outputs found
A deep i-selected multi-waveband galaxy catalogue in the COSMOS field
In this paper we present a deep and homogeneous i-band selected
multi-waveband catalogue in the COSMOS field covering an area of about 0.7
square-degree. Our catalogue with a formal 50 percent completeness limit for
point sources of i~26.7 comprises about 290.000 galaxies with information in 8
passbands. We combine publicly available u, B, V, r, i, z, and K data with
proprietary imaging in H band. We discuss in detail the observations, the data
reduction, and the photometric properties of the H-band data. We estimate
photometric redshifts for all the galaxies in the catalogue. A comparison with
162 spectroscopic redshifts in the redshift range 0 < z < 3 shows that the
achieved accuracy of the photometric redshifts is (Delta_z / (z_spec+1)) ~0.035
with only ~2 percent outliers. We derive absolute UV magnitudes and investigate
the evolution of the luminosity function evaluated in the rest-frame UV at 1500
Angstrom. There is a good agreement between the LFs derived here and the LFs
derived in the FORS Deep Field. We see a similar brightening of M_star and a
decrease of phi_star with redshift. The catalogue including the photometric
redshift information is made publicly available.Comment: 20 pages, 17 figures, accepted for publication in MNRAS; high
resulution paper: http://www.mpe.mpg.de/~gabasch/COSMOS/cosmos.pd
The stellar mass function of galaxies to z ~ 5 in the Fors Deep and GOODS-S fields
We present a measurement of the evolution of the stellar mass function (MF)
of galaxies and the evolution of the total stellar mass density at 0<z<5. We
use deep multicolor data in the Fors Deep Field (FDF; I-selected reaching
I_AB=26.8) and the GOODS-S/CDFS region (K-selected reaching K_AB=25.4) to
estimate stellar masses based on fits to composite stellar population models
for 5557 and 3367 sources, respectively. The MF of objects from the GOODS-S
sample is very similar to that of the FDF. Near-IR selected surveys hence
detect the more massive objects of the same principal population as do
I-selected surveys. We find that the most massive galaxies harbor the oldest
stellar populations at all redshifts. At low z, our MF follows the local MF
very well, extending the local MF down to 10^8 Msun. The faint end slope is
consistent with the local value of alpha~1.1 at least up to z~1.5. Our MF also
agrees very well with the MUNICS and K20 results at z<2. The MF seems to evolve
in a regular way at least up to z~2 with the normalization decreasing by 50% to
z=1 and by 70% to z=2. Objects having M>10^10 Msun which are the likely
progenitors of todays L* galaxies are found in much smaller numbers above z=2.
However, we note that massive galaxies with M>10^11 Msun are present even to
the largest redshift we probe. Beyond z=2 the evolution of the mass function
becomes more rapid. We find that the total stellar mass density at z=1 is 50%
of the local value. At z=2, 25% of the local mass density is assembled, and at
z=3 and z=5 we find that at least 15% and 5% of the mass in stars is in place,
respectively. The number density of galaxies with M>10^11 Msun evolves very
similarly to the evolution at lower masses. It decreases by 0.4 dex to z=1, by
0.6 dex to z=2, and by 1 dex to z=4.Comment: Accepted for publication in ApJ
Implementation of PhotoZ under Astro-WISE - A photometric redshift code for large datasets
We describe the implementation of the PhotoZ code in the framework of the
Astro-WISE package and as part of the Photometric Classification Server of the
PanSTARRS pipeline. Both systems allow the automatic measurement of photometric
redshifts for the millions of objects being observed in the PanSTARRS project
or expected to be observed by future surveys like KIDS, DES or EUCLID.Comment: Accepted for publication in topical issue of Experimental Astronomy
on Astro-WISE information system, references update
Tracing the Mass-Assembly History of Galaxies with Deep Surveys
We use the optical and near-infrared galaxy samples from the Munich
Near-Infrared Cluster Survey (MUNICS), the FORS Deep Field (FDF) and GOODS-S to
probe the stellar mass assembly history of field galaxies out to z ~ 5.
Combining information on the galaxies' stellar mass with their star-formation
rate and the age of the stellar population, we can draw important conclusions
on the assembly of the most massive galaxies in the universe: These objects
contain the oldest stellar populations at all redshifts probed. Furthermore, we
show that with increasing redshift the contribution of star-formation to the
mass assembly for massive galaxies increases dramatically, reaching the era of
their formation at z ~ 2 and beyond. These findings can be interpreted as
evidence for an early epoch of star formation in the most massive galaxies in
the universe.Comment: 3 pages, 2 figures; published in B. Aschenbach, V. Burwitz, G.
Hasinger, B. Leibundgut (eds.): "Relativistic Astrophysics and Cosmology -
Einstein's Legacy. Proceedings of the Conference held in Munich, 2006", ESO
Astrophysics Symposia, Springer Verlag, 2007, p. 310. Replaced to match final
published versio
The star formation rate history in the FORS Deep and GOODS South Fields
We measure the star formation rate (SFR) as a function of redshift z up to z
\~4.5, based on B, I and (I+B) selected galaxy catalogues from the FORS Deep
Field (FDF) and the K-selected catalogue from the GOODS-South field. Distances
are computed from spectroscopically calibrated photometric redshifts accurate
to (Delta_z / (z_spec+1)) ~0.03 for the FDF and ~0.056 for the GOODS-South
field. The SFRs are derived from the luminosities at 1500 Angstroem. We find
that the total SFR estimates derived from B, I and I+B catalogues agree very
well (\lsim 0.1 dex) while the SFR from the K catalogue is lower by ~0.2 dex.
We show that the latter is solely due to the lower star-forming activity of
K-selected intermediate and low luminosity (L<L_*) galaxies. The SFR of bright
(L>L_*) galaxies is independent of the selection band, i.e. the same for B, I,
(I+B), and K-selected galaxy samples. At all redshifts, luminous galaxies
(L>L_*) contribute only ~1/3 to the total SFR. There is no evidence for
significant cosmic variance between the SFRs in the FDF and GOODs-South field,
~0.1 dex, consistent with theoretical expectations. The SFRs derived here are
in excellent agreement with previous measurements provided we assume the same
faint-end slope of the luminosity function as previous works (alpha ~ -1.6).
However, our deep FDF data indicate a shallower slope of alpha=-1.07, implying
a SFR lower by ~0.3 dex. We find the SFR to be roughly constant up to z ~4 and
then to decline slowly beyond, if dust extinctions are assumed to be constant
with redshift.Comment: 6 pages, 2 figures, Accepted for publication in ApJ
Lyman-alpha emission galaxies at a redshift of z = 5.7 in the FORS Deep Field
We present the results of a search for Lyman-alpha emission galaxies at z~
5.7 in the FORS Deep Field. The objective of this study is to improve the faint
end of the luminosity function of high-redshift Lyman-alpha emitting galaxies
and to derive properties of intrinsically faint Lyman-alpha emission galaxies
in the young universe. Using FORS2 at the ESO VLT and a set of special
interference filters, we identified candidates for high-redshift Lyman-alpha
galaxies. We then used FORS2 in spectroscopic mode to verify the
identifications and to study their spectral properties. The narrow-band
photometry resulted in the detection of 15 likely Lyman-alpha emission
galaxies. Spectra with an adequate exposure time could be obtained for eight
galaxies. In all these cases the presence of Lyman-alpha emission at z = 5.7
was confirmed spectroscopically. The line fluxes of the 15 candidates range
between 3 and 16 * 10^-21 Wm^-2, which corresponds to star-formation rates not
corrected for dust between 1 and 5 Msun/yr. The luminosity function derived for
our photometrically identified objects extends the published luminosity
functions of intrinsically brighter Lyman-alpha galaxies. With this technique
the study of high-redshift Lyman-alpha emission galaxies can be extended to low
intrinsic luminosities.Comment: 9 pages, 17 figures. Accepted by A&A. PDF version with higher
resolution figures here:
http://www.lsw.uni-heidelberg.de/users/jheidt/fdf/pubs/fdflae5_7_110406.pd
The evolution of the mass function split by morphology up to redshift 1 in the FORS Deep and the GOODS-S Fields
We study the evolution of the stellar mass density for the separate families
of bulge-dominated and disk-dominated galaxies over the redshift range 0.25 < z
< 1.15. We derive quantitative morphology for a statistically significant
galaxy sample of 1645 objects selected from the FORS Deep and the GOODS-S
Fields. We find that the morphological mix evolves monotonically with time: the
higher the redshift, the more disk systems dominate the total mass content. At
redshift about 1, massive objects (M_stellar > 7E10 M_solar) host about half of
the mass contained in objects of similar mass in the local universe. The
contribution from early and late type galaxies to the mass budget at z about 1
is nearly equal. We show that in situ star formation is not sufficient to
explain the changing mass budget. Moreover we find that the star formation rate
per unit stellar mass of massive galaxies increases with redshift only for the
intermediate and early morphological types, while it stays nearly constant for
late-type objects. This suggests that merging and/or frequent accretion of
small mass objects has a key role in the shaping of the Hubble sequence as we
observe it now, and also in decreasing the star formation activity of the
bulge-dominated descendants of massive disk galaxies.Comment: Accepted for publication in ApJL; 4 pages, 3 color figures, uses
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