25 research outputs found
Halpha and 4000 Angstrom Break Measurements for ~3500 K-selected Galaxies at 0.5<z<2.0
We measure spectral features of ~3500 K-selected galaxies at 0.5<z<2.0 from
high quality medium-band photometry using a new technique. First, we divide the
galaxy sample in 32 subsamples based on the similarities between the full
spectral energy distributions (SEDs) of the galaxies. For each of these 32
galaxy types we construct a composite SED by de-redshifting and scaling the
observed photometry. This approach increases the signal-to-noise ratio and
sampling of galaxy SEDs and allows for model-independent stellar population
studies. The composite SEDs are of spectroscopic quality, and facilitate -- for
the first time -- Halpha measurement for a large magnitude-limited sample of
distant galaxies. The linewidths indicate a photometric redshift uncertainty of
dz<0.02x(1+z). The composite SEDs also show the Balmer and 4000 Angstrom
breaks, MgII absorption at ~2800 Angstrom, the dust absorption feature at 2175
Angstrom, and blended [OIII]+Hbeta emission. We compare the total equivalent
width of Halpha, [NII], and [SII] (W_Halpha+) with the strength of the 4000
Angstrom break (D(4000)) and the best-fit specific star formation rate, and
find that all these properties are strongly correlated. This is a reassuring
result, as currently most distant stellar population studies are based on just
continuum emission. Furthermore, the relation between W_Halpha+ and Dn(4000)
provides interesting clues to the SFHs of galaxies, as these features are
sensitive to different stellar ages. We find that the correlation between
W_Halpha+ and D(4000) at 0.5<z<2.0 is similar to z~0, and that the suppression
of star formation in galaxies at z<2 is generally not abrupt, but a gradual
process.Comment: Accepted for publication in ApJ; high-resolution version can be
downloaded at https://www.cfa.harvard.edu/~mkriek/papers
A massive, quiescent galaxy at redshift of z=3.717
In the early Universe finding massive galaxies that have stopped forming
stars present an observational challenge as their rest-frame ultraviolet
emission is negligible and they can only be reliably identified by extremely
deep near-infrared surveys. These have revealed the presence of massive,
quiescent early-type galaxies appearing in the universe as early as z2,
an epoch 3 Gyr after the Big Bang. Their age and formation processes have now
been explained by an improved generation of galaxy formation models where they
form rapidly at z3-4, consistent with the typical masses and ages derived
from their observations. Deeper surveys have now reported evidence for
populations of massive, quiescent galaxies at even higher redshifts and earlier
times, however the evidence for their existence, and redshift, has relied
entirely on coarsely sampled photometry. These early massive, quiescent
galaxies are not predicted by the latest generation of theoretical models.
Here, we report the spectroscopic confirmation of one of these galaxies at
redshift z=3.717 with a stellar mass of 1.710 M whose
absorption line spectrum shows no current star-formation and which has a
derived age of nearly half the age of the Universe at this redshift. The
observations demonstrates that the galaxy must have quickly formed the majority
of its stars within the first billion years of cosmic history in an extreme and
short starburst. This ancestral event is similar to those starting to be found
by sub-mm wavelength surveys pointing to a possible connection between these
two populations. Early formation of such massive systems is likely to require
significant revisions to our picture of early galaxy assembly.Comment: 6 pages, 7 figures. This is the final preprint corresponding closely
to the published version. Uploaded 6 months after publication in accordance
with Nature polic
The Age Spread of Quiescent Galaxies with the NEWFIRM Medium-band Survey: Identification of the Oldest Galaxies out to z~2
With a complete, mass-selected sample of quiescent galaxies from the NEWFIRM
Medium-Band Survey (NMBS), we study the stellar populations of the oldest and
most massive galaxies (>10^11 Msun) to high redshift. The sample includes 570
quiescent galaxies selected based on their extinction-corrected U-V colors out
to z=2.2, with accurate photometric redshifts, sigma_z/(1+z)~2%, and rest-frame
colors, sigma_U-V~0.06 mag. We measure an increase in the intrinsic scatter of
the rest-frame U-V colors of quiescent galaxies with redshift. This scatter in
color arises from the spread in ages of the quiescent galaxies, where we see
both relatively quiescent red, old galaxies and quiescent blue, younger
galaxies towards higher redshift. The trends between color and age are
consistent with the observed composite rest-frame spectral energy distributions
(SEDs) of these galaxies. The composite SEDs of the reddest and bluest
quiescent galaxies are fundamentally different, with remarkably well-defined
4000A- and Balmer-breaks, respectively. Some of the quiescent galaxies may be
up to 4 times older than the average age- and up to the age of the universe, if
the assumption of solar metallicity is correct. By matching the scatter
predicted by models that include growth of the red sequence by the
transformation of blue galaxies to the observed intrinsic scatter, the data
indicate that most early-type galaxies formed their stars at high redshift with
a burst of star formation prior to migrating to the red sequence. The observed
U-V color evolution with redshift is weaker than passive evolution predicts;
possible mechanisms to slow the color evolution include increasing amounts of
dust in quiescent galaxies towards higher redshift, red mergers at z<1, and a
frosting of relatively young stars from star formation at later times.Comment: 20 pages, 20 figures, accepted for publication in Ap
The NEWFIRM Medium-band Survey: Photometric Catalogs, Redshifts and the Bimodal Color Distribution of Galaxies out to z~3
We present deep near-infrared (NIR) medium-bandwidth photometry over the
wavelength range 1-1.8 microns in the All-wavelength Extended Groth strip
International Survey (AEGIS) and Cosmic Evolution Survey (COSMOS) fields. The
observations were carried out as part of the NEWFIRM Medium-Band Survey (NMBS),
an NOAO survey program on the Mayall 4m telescope on Kitt Peak using the NOAO
Extremely Wide-Field Infrared Imager (NEWFIRM). In this paper, we describe the
full details of the observations, data reduction and photometry for the survey.
We also present a public K-selected photometric catalog, along with accurate
photometric redshifts. The redshifts are computed with 37 (20) filters in the
COSMOS (AEGIS) fields, combining the NIR medium-bandwidth data with existing
ultraviolet (UV; Galaxy Evolution Explorer), visible and NIR
(Canada-France-Hawaii Telescope and Subaru) and mid-IR (Spitzer/IRAC) imaging.
We find excellent agreement with publicly available spectroscopic redshifts,
with sigma_z/(1+z)~1-2% for ~4000 galaxies at z=0-3. The NMBS catalogs contain
~13,000 galaxies at z>1.5 with accurate photometric redshifts and rest-frame
colors. Due to the increased spectral resolution obtained with the five NIR
medium-band filters, the median 68% confidence intervals of the photometric
redshifts of both quiescent and star-forming galaxies are a factor of ~2 times
smaller when comparing catalogs with medium-band NIR photometry to NIR
broadband photometry. We show evidence for a clear bimodal color distribution
between quiescent and star-forming galaxies that persists to z~3, a higher
redshift than has been probed so far.Comment: All NMBS data products and a high resolution version of paper are
available for download at http://www.astro.yale.edu/nmbs; Accepted for
publication in ApJ; 24 pages, 21 figures, 4 table
HLA-G and HLA-E specific mRNAs connote opposite prognostic significance in renal cell carcinoma
HLA-G and HLA-E specific mRNAs connote opposite prognostic significance in renal cell carcinoma
Abstract Background Renal cell carcinoma (RCC) is characterized by its resistance to radiotherapy and/or chemotherapy. On the other hand, it is an immunogenic tumor - it is able to stimulate antitumor responses. A prognostic significance of HLA-G expression by neoplastic cells in RCC is not well characterized; significance HLA-E expression in RCC is not characterized at all. Methods In our study, we evaluated the expression of HLA-G and HLA-E specific mRNA transcripts produced by neoplastic cells in 38 cases of RCC and in 10 samples of normal kidney parenchyma. The results were statistically correlated with various clinico-pathological parameters. Results We confirmed that HLA-G is downregulated in normal kidney tissue; if it is up-regulated in RCC, then it is connected to worse prognosis. On the other hand, HLA-E mRNA transcripts were present in both normal kidney tissue and RCC and their increasing concentrations counterintuitively carried better prognosis, more favorable pT stage and lower nuclear Fuhrmann’s grade. Conclusion Considering the fact that there is known aberrant activation of HLA-G and HLA-E expression by interferons, identification of HLA-G and HLA-E status could contribute to better selection of RCC patients who could possibly benefit from more tailored neoadjuvant biological/immunological therapy. Thus, these molecules could represent useful prognostic biomarkers in RCC, and the expression of both these molecules in RCC deserves further study. The virtual Slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/7383071387016614</p
A Spectroscopic Follow-up Program of Very Massive Galaxies at 3 < z
We present the analysis and results of a spectroscopic follow-up program of a
mass-selected sample of six galaxies at 3 < z < 4 using data from Keck-NIRSPEC
and VLT-Xshooter. We confirm the z > 3 redshifts for half of the sample through
the detection of strong nebular emission lines, and improve the zphot accuracy
for the remainder of the sample through the combination of photometry and
spectra. The modeling of the emission-line-corrected spectral energy
distributions (SEDs) adopting improved redshifts confirms the very large
stellar masses of the sample (M_* ~ 1.5-4 x 10^11 Msun) in the first 2 Gyrs of
cosmic history, with a diverse range in stellar ages, star formation rates and
dust content. From the analysis of emission line luminosities and widths, and
far-infrared (FIR) fluxes we confirm that >80% of the sample are hosts to
luminous hidden active galactic nuclei (AGNs), with bolometric luminosities of
~10^(44-46) erg/s. We find that the MIPS 24um photometry is largely
contaminated by AGN continuum, rendering the SFRs derived using only 24um
photometry to be severely overestimated. By including the emission from the AGN
in the modeling of the UV-to-FIR SEDs, we confirm that the presence of the AGN
does not bias considerably the stellar masses (< 0.3 dex at 1\sigma). We show
evidence for a rapid increase of the AGN fraction from ~30% to ~60-100% over
the 1 Gyr between z~2 and z~3. Although we cannot exclude some enhancement of
the AGN fraction for our sample due to selection effects, the small measured
[OIII] contamination to the observed K-band fluxes suggests that our sample is
not significantly biased toward massive galaxies hosting AGNs.Comment: 16 pages, 8 figures, 6 tables, Accepted to ApJ. arXiv admin note:
text overlap with arXiv:1406.000