28 research outputs found
Deep Observations of Lyman Break Galaxies
We summarise the main results of recent work on the Lyman break galaxy
population which takes advantage of newly commissioned instrumentation on the
VLT and Keck telescopes to push the detection of these objects to new
wavelengths and more sensitive limits. We focus in particular on near-infrared
observations targeted at detecting emission lines of [O II], [O III], and
H-beta and on the first tentative detection of Lyman continuum emission from
star forming galaxies at z = 3.Comment: 9 pages, LaTeX, 6 Postscript Figures. To appear in the Proceedings of
the ESO Symposium: Deep Fields, ed. S. Cristiani (Berlin: Springer
H-alpha Spectroscopy of Galaxies at z>2: Kinematics and Star Formation
We present near-infrared spectroscopy of H-alpha emission lines in a sample
of 16 star-forming galaxies at redshifts 2.0<z<2.6. Our targets are drawn from
a large sample of galaxies photometrically selected and spectroscopically
confirmed to lie in this redshift range. Six of the galaxies exhibit spatially
extended, tilted H-alpha emission lines; rotation curves for these objects
reach mean velocities of ~150 km/s at radii of ~6 kpc, without corrections for
any observational effects. The velocities and radii give a mean dynamical mass
of M>4e10 M_sun. One-dimensional velocity dispersions for the 16 galaxies range
from ~50 to ~260 km/s, and in cases where we have both virial masses implied by
the velocity dispersions and dynamical masses derived from the spatially
extended emission lines, they are in rough agreement. We compare our kinematic
results to similar measurements made at z~3, and find that both the observed
rotational velocities and velocity dispersions tend to be larger at z~2 than at
z~3. We find a mean SFR_H-alpha of 16 M_sun/yr and an average
SFR_H-alpha/SFR_UV ratio of 2.4, without correcting for extinction. We see
moderate evidence for an inverse correlation between the UV continuum
luminosity and the ratio SFR_H-alpha/SFR_UV, such as might be observed if the
UV-faint galaxies suffered greater extinction. We discuss the effects of dust
and star formation history on the SFRs, and conclude that extinction is the
most likely explanation for the discrepancy between the two SFRs.Comment: 20 pages, 9 figures. Accepted by Ap
The Rest Frame Optical Spectra of Lyman Break Galaxies: Star Formation, Extinction, Abundances, and Kinematics
We present the first results of a spectroscopic survey of Lyman break
galaxies in the near-infrared aimed at detecting the emission lines of [O II],
[O III], and Hbeta from the H II regions of star forming galaxies at z = 3.
From observations of 19 objects with the Keck and VLT telescopes, we reach
the following main conclusions. Contrary to expectations, the star formation
rates deduced from the Hbeta luminosity are on average no larger than those
implied by the stellar continuum at 1500 A; presumably any differential
extinction between rest-frame optical and UV is small compared with the
relative uncertainties in the calibrations of these two star formation tracers.
For the galaxies in our sample, the abundance of O can only be determined to
within one order of magnitude. Even so, it seems well established that LBGs are
the most metal-enriched structures at z = 3, apart from QSOs, with abundances
greater than about 1/10 solar. They are also significantly overluminous for
their metallicities; this is probably an indication that their mass-to-light
ratios are small compared with present-day galaxies. At face value their
velocity dispersions, sigma = 50 - 115 km/s imply virial masses of about
10^{10} solar masses within half-light radii of 2.5 kpc. However, we are unable
to establish if the widths of the emission lines do reflect the motions of the
H II regions within the gravitational potential of the galaxies, even though in
two cases we see hints of rotation curves. All 19 LBGs observed show evidence
for galactic-scale superwinds; such outflows are important for regulating star
formation, distributing metals over large volumes, and allowing Lyman continuum
photons to escape and ionize the IGM.Comment: 44 pages, LaTeX, 13 Postscript Figures. Accepted for publication in
the Astrophysical Journal, Vol. 554, No. 2 (Jun 20, 2001
Deep Observations of Lyman Break Galaxies
We summarise the main results of recent work on the Lyman break galaxy population which takes advantage of newly commissioned instrumentation on the VLT and Keck telescopes to push the detection of these objects to new wavelengths and more sensitive limits
Measuring the Average Evolution of Luminous Galaxies at z<3: The Rest-frame Optical Luminosity Density, Spectral Energy Distribution, and Stellar Mass Density
(Abridged) We present the evolution of the volume averaged properties of the
rest-frame optically luminous galaxy population to z~3, determined from four
disjoint deep fields with optical to near-infrared wavelength coverage. We
select galaxies above a rest-frame V-band luminosity of 3x10^10 Lsol and
characterize their rest-frame UV through optical properties via the mean
spectral energy distribution (SED). To measure evolution we apply the same
selection criteria to a sample of galaxies from the Sloan Digital Sky Survey
and COMBO-17. The mean rest-frame 2200Ang through V-band SED becomes steadily
bluer with increasing redshift but at z<3 the mean SED falls within the range
defined by ``normal'' galaxies in the nearby Universe. We measure stellar
mass-to-light ratios (Mstar/L) by fitting models to the rest-frame UV-optical
SEDs and derive the stellar mass density. The stellar mass density in luminous
galaxies has increased by a factor of 3.5-7.9 from z=3 to z=0.1, including
field-to-field variance uncertainties. After correcting to total, the measured
mass densities at z<2 lie below the integral of the star formation rate (SFR)
density as a function of redshift as derived from UV selected samples. This may
indicate a systematic error in the mass densities or SFR(z) estimates. We find
large discrepancies between recent model predictions for the evolution of the
mass density and our results, even when our observational selection is applied
to the models. Finally we determine that Distant Red Galaxies (selected to have
J_s - K_s>2.3) in our LV selected samples contribute 30% and 64% of the stellar
mass budget at z~2 and z~ 2.8 respectively. These galaxies are largely absent
from UV surveys and this result highlights the need for mass selection of high
redshift galaxies.Comment: Accepted for publication in the Astrophysical Journal, 24 pages, 16
figure
What do we learn from IRAC observations of galaxies at 2 < z < 3.5?
We analyze very deep HST, VLT and Spitzer photometry of galaxies at 2<z<3.5
in the Hubble Deep Field South. The sample is selected from the deepest public
K-band imaging currently available. We show that the rest-frame U-V vs V-J
color-color diagram is a powerful diagnostic of the stellar populations of
distant galaxies. Galaxies with red rest-frame U-V colors are generally red in
rest-frame V-J as well. However, at a given U-V color a range in V-J colors
exists, and we show that this allows us to distinguish young, dusty galaxies
from old, passively evolving galaxies. We quantify the effects of IRAC
photometry on estimates of masses, ages, and the dust content of z>2 galaxies.
The estimated distributions of these properties do not change significantly
when adding IRAC data to the UBVIJHK photometry. However, for individual
galaxies the addition of IRAC can improve the constraints on the stellar
populations, especially for red galaxies: uncertainties in stellar mass
decrease by a factor of 2.7 for red (U-V > 1) galaxies, but only by a factor of
1.3 for blue (U-V < 1) galaxies. We find a similar color-dependence of the
improvement for estimates of age and dust extinction. In addition, the
improvement from adding IRAC depends on the availability of full near-infrared
JHK coverage; if only K-band were available, the mass uncertainties of blue
galaxies would decrease by a more substantial factor 1.9. Finally, we find that
a trend of galaxy color with stellar mass is already present at z>2. The most
massive galaxies at high redshift have red rest-frame U-V colors compared to
lower mass galaxies even when allowing for complex star formation histories.Comment: Accepted for publication in the Astrophysical Journal, 16 pages, 16
figure
De Novo ZMYND8 variants result in an autosomal dominant neurodevelopmental disorder with cardiac malformations
Purpose: ZMYND8 encodes a multidomain protein that serves as a central interactive hub for coordinating critical roles in transcription regulation, chromatin remodeling, regulation of superenhancers, DNA damage response and tumor suppression. We delineate a novel neurocognitive disorder caused by variants in the ZMYND8 gene. Methods: An international collaboration, exome sequencing, molecular modeling, yeast twohybrid assays, analysis of available transcriptomic data and a knockdown Drosophila model were used to characterize the ZMYND8 variants. Results: ZMYND8 variants were identified in 11 unrelated individuals; 10 occurred de novo and one suspected de novo; 2 were truncating, 9 were missense, of which one was recurrent. The disorder is characterized by intellectual disability with variable cardiovascular, ophthalmologic and minor skeletal anomalies. Missense variants in the PWWP domain of ZMYND8 abolish the interaction with Drebrin and missense variants in the MYND domain disrupt the interaction with GATAD2A. ZMYND8 is broadly expressed across cell types in all brain regions and shows highest expression in the early stages of brain development. Neuronal knockdown of the Drosophila ZMYND8 ortholog results in decreased habituation learning, consistent with a role in cognitive function. Conclusion: We present genomic and functional evidence for disruption of ZMYND8 as a novel etiology of syndromic intellectual disability
High Resolution Infrared Spectroscopy in Astronomy: Proceedings of an ESO Workshop Held at Garching, Germany, 18-21 November 2003
Two specialized new instruments for ESO's VLT, VISIR and CRIRES, spawned the idea for this workshop. CRIRES is a dedicated very high resolution infrared spectrograph; VISIR features a high resolution spectroscopic mode. Together, the instruments combine the sensitivity of an 8m-telescope with the now well-established reliability of VLT-facility instruments. High resolution here means that lines in cool stellar atmospheres and HII-regions can be resolved. The astrophysical topics discussed in this rather specialized workshop range from the inner solar system to active galactic nuclei. There are many possibilities for new discoveries with these instruments, but the unique capability, which becomes available through high-resolution infrared spectroscopy, is the observation of molecular rotational-vibrational transitions in many astrophysical environments. Particularly interesting and surprising in this context, many papers on modeling and laboratory spectroscopy at the workshop appear to indicate that astronomical observations are lagging a bit behind in this field. The papers are an interesting mix of reports from existing high resolution facilities, reports on modeling efforts of synthetic spectra and reports on laboratory spectra. In this sense, a fruitful exchange between molecular physics and astronomy was again accomplished and is documented in this volume