1,190 research outputs found
Morphology and Redshifts of Extremely Red Galaxies in the GOODS/CDFS deep ISAAC field
We present the photometric redshift distribution of a sample of 198 Extremely
Red Galaxies (ERGs) with Ks3.92 (Vega), selected by Roche et al.
in 50.4 sq. arcmin of the Chandra Deep Field South (CDFS). The sample has been
obtained using ISAAC-VLT and ACS-HST GOODS public data. We also show the
results of a morphological study of the 72 brightest ERGs in the z band (z<25,
AB).Comment: 2 pages, 2 figures. To appear in the proceedings of the ESO/USM/MPE
Workshop "Multiwavelength Mapping of Galaxy Formation and Evolution", Venice,
October 13-16, 200
The role of the LIRG and ULIRG phases in the evolution of Ks-selected galaxies
We investigate the role of the luminous infrared galaxy (LIRG) and
ultra-luminous infrared galaxy (ULIRG) phases in the evolution of Ks-selected
galaxies and, in particular, Extremely Red Galaxies (ERGs). With this aim, we
compare the properties of a sample of 2905 Ks<21.5 (Vega mag) galaxies in the
GOODS/CDFS with the sub-sample of those 696 sources which are detected at 24
microns. We find that LIRGs constitute 30% of the galaxies with stellar mass
M>1x10^{11} Msun assembled at redshift z=0.5. A minimum of 65% of the galaxies
with M>2.5x10^{11} Msun at z~2-3 are ULIRGs at those redshifts. 60% of the
ULIRGs in our sample have the characteristic colours of ERGs. Conversely, 40%
of the ERGs with stellar mass M>1.3x10^{11} Msun at 1.5<z<2.0 and a minimum of
52% of those with the same mass cut at 2.0<z<3.0 are ULIRGs. The average
optical/near-IR properties of the massive ERGs at similar redshifts that are
identified with ULIRGs and that are not have basically no difference,
suggesting that both populations contain the same kind of objects in different
phases of their lives.
LIRGs and ULIRGs have an important role in galaxy evolution and mass
assembly, and, although they are only able to trace a fraction of the massive
(M>1x10^{11} Msun) galaxies present in the Universe at a given time, this
fraction becomes very significant (>50%) at redshifts z>~2.Comment: Accepted for publication in A&A. 9 pages, 6 figure
Chlorinated auxinsâhow does Arabidopsis thaliana deal with them?
Plant hormones have various functions in plants and play crucial roles in all developmental and differentiation stages. Auxins constitute one of the most important groups with the major representative indole-3-acetic acid (IAA). A halogenated derivate of IAA, 4-chloro-indole-3-acetic acid (4-Cl-IAA), has previously been identified in Pisum sativum and other legumes. While the enzymes responsible for the halogenation of compounds in bacteria and fungi are well studied, the metabolic pathways leading to the production of 4-Cl-IAA in plants, especially the halogenating reaction, are still unknown. Therefore, bacterial flavin-dependent tryptophan-halogenase genes were transformed into the model organism Arabidopsis thaliana. The type of chlorinated indole derivatives that could be expected was determined by incubating wild type A. thaliana with different Cl-tryptophan derivatives. We showed that, in addition to chlorinated IAA, chlorinated IAA conjugates were synthesized. Concomitantly, we found that an auxin conjugate synthetase (GH3.3 protein) from A. thaliana was able to convert chlorinated IAAs to amino acid conjugates in vitro. In addition, we showed that the production of halogenated tryptophan (Trp), indole-3-acetonitrile (IAN) and IAA is possible in transgenic A. thaliana in planta with the help of the bacterial halogenating enzymes. Furthermore, it was investigated if there is an effect (i) of exogenously applied Cl-IAA and Cl-Trp and (ii) of endogenously chlorinated substances on the growth phenotype of the plants
The stellar mass function of the most massive galaxies at 3<=z<5 in the UKIDSS Ultra Deep Survey
We have analysed a sample of 1292 4.5 micron-selected galaxies at z>=3, over
0.6 square degrees of the UKIRT Infrared Deep Survey (UKIDSS) Ultra Deep Survey
(UDS). Using photometry from the U band through 4.5 microns, we have obtained
photometric redshifts and derived stellar masses for our sources. Only two of
our galaxies potentially lie at z>5. We have studied the galaxy stellar mass
function at 3<=z<5, based on the 1213 galaxies in our catalogue with [4.5]<=
24.0. We find that: i) the number density of M > 10^11 Msun galaxies increased
by a factor > 10 between z=5 and 3, indicating that the assembly rate of these
galaxies proceeded > 20 times faster at these redshifts than at 0<z<2; ii) the
Schechter function slope alpha is significantly steeper than that displayed by
the local stellar mass function, which is both a consequence of the steeper
faint end and the absence of a pure exponential decline at the high-mass end;
iii) the evolution of the comoving stellar mass density from z=0 to 5 can be
modelled as log10 (rho_M) =-(0.05 +/- 0.09) z^2 - (0.22 -/+ 0.32) z + 8.69. At
3 10^11 Msun galaxies would be missed by optical
surveys with R<27 or z<26. Thus, our study demonstrates the importance of deep
mid-IR surveys over large areas to perform a complete census of massive
galaxies at high z and trace the early stages of massive galaxy assembly.Comment: 16 pages, 15 figures, 2 tables. Accepted for publication in MNRA
Is Evidence of the Defendant\u27s Wealth Admissable When Punitive Damages Are Awarded in New York?
Spitzer bright, UltraVISTA faint sources in COSMOS: the contribution to the overall population of massive galaxies at z=3-7
We have analysed a sample of 574 Spitzer 4.5 micron-selected galaxies with
[4.5]24 (AB) over the UltraVISTA ultra-deep COSMOS field. Our
aim is to investigate whether these mid-IR bright, near-IR faint sources
contribute significantly to the overall population of massive galaxies at
redshifts z>=3. By performing a spectral energy distribution (SED) analysis
using up to 30 photometric bands, we have determined that the redshift
distribution of our sample peaks at redshifts z~2.5-3.0, and ~32% of the
galaxies lie at z>=3. We have studied the contribution of these sources to the
galaxy stellar mass function (GSMF) at high redshifts. We found that the
[4.5]24 galaxies produce a negligible change to the GSMF
previously determined for Ks_auto<24 sources at 3=<z<4, but their contribution
is more important at 4=~50% of the galaxies with stellar
masses Mst>~6 x 10^10 Msun. We also constrained the GSMF at the highest-mass
end (Mst>~2 x 10^11 Msun) at z>=5. From their presence at 5=<z<6, and virtual
absence at higher redshifts, we can pinpoint quite precisely the moment of
appearance of the first most massive galaxies as taking place in the ~0.2 Gyr
of elapsed time between z~6 and z~5. Alternatively, if very massive galaxies
existed earlier in cosmic time, they should have been significantly
dust-obscured to lie beyond the detection limits of current, large-area, deep
near-IR surveys.Comment: 18 pages, 15 figures, 4 tables. Updated to match version in press at
the Ap
Linking stellar mass and star formation in Spitzer/MIPS 24 micron galaxies
We present deep Ks<21.5 (Vega) identifications, redshifts and stellar masses
for most of the sources composing the bulk of the 24 micron background in the
GOODS/CDFS. Our identified sample consists of 747 Spitzer/MIPS 24 micron
objects, and includes ~94% of all the 24 micron sources in the GOODS-South
field which have fluxes Snu(24)>83 microJy (the 80% completeness limit of the
Spitzer/GTO 24 micron catalog). 36% of our galaxies have spectroscopic
redshifts (mostly at z<1.5) and the remaining ones have photometric redshifts
of very good quality, with a median of |dz|=|zspec-zphot|/(1+zspec)=0.02. We
find that MIPS 24 micron galaxies span the redshift range z~0-4, and that a
substantial fraction (28%) lie at high redshifts z>1.5. We determine the
existence of a bump in the redshift distribution at z~1.9, indicating the
presence of a significant population of galaxies with PAH emission at these
redshifts. Massive (M>10^11 Msun) star-forming galaxies at redshifts 2<z<3 are
characterized by very high star-formation rates (SFR>500 Msun/yr), and some of
them are able to construct a mass of 10^10-10^11 Msun in a single burst
lifetime (~0.01-0.1 Gyr). At lower redshifts z<2, massive star-forming galaxies
are also present, but appear to be building their stars on long timescales,
either quiescently or in multiple modest burst-like episodes. At redshifts
z~1-2, the ability of the burst-like mode to produce entire galaxies in a
single event is limited to some lower (M<7x10^10 Msun) mass systems, and it is
basically negligible at z<1. Our results support a scenario where
star-formation activity is differential with assembled stellar mass and
redshift, and where the relative importance of the burst-like mode proceeds in
a down-sizing way from high to low redshifts. (abridged)Comment: Accepted for publication in the ApJ. 19 pages, 10 figures. Uses
emulateap
Monitoramento orbital das queimadas em ĂĄreas indĂgenas e unidades de conservação no Brasil em 2001.
bitstream/CNPM/727/1/cot8_qmdindig.pd
Help-negation among telephone crisis support workers: Impact on personal wellbeing and worker performance
Paper presented at the National Suicide Prevention Conference, 24-26 July 2013, Melbourne, Australia.
Telephone counsellors (TCs) provide front line mental health support to callers in crisis. TCs often support callers with suicidal thoughts, depression and anxiety, and the caller\u27s experience of the call will influence whether they will seek help from a helpline in the future. Despite their important role, little information on TCs\u27 mental health and help-seeking behaviours exists - a structured literature search returned 2 papers. This paper presents the results of a study that answered three research questions: 1. Do telephone counsellors experience symptoms of suicidal ideation, depression and anxiety? 2. Do telephone counsellors intend to seek help for these symptoms? 3. Do service provision intentions vary for telephone counsellors experiencing different levels of symptoms? A representative sample of 124 Lifeline Telephone Crisis Supporters (TCSs) from across Australia took part in the study. Results suggest that help-negation (reluctance to seek help as distress levels increase) occurs among TCSs who are exposed to suicidal, depressed and anxious callers, and impacts both personal wellbeing and TCSs intention to use recommended skills with callers. The impact of exposure to callers in crisis is an occupational hazard for all telephone counsellors in the sector. Implications for TC training, preparation, supervision, and support are discussed
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