157 research outputs found
Multi-wavelength characterisation of z~2 clustered, dusty star forming galaxies discovered by Planck
(abridged) We report the discovery of PHz G95.5-61.6, a complex structure
detected in emission in the Planck all-sky survey that corresponds to two
over-densities of high-redshift galaxies. This is the first source from the
Planck catalogue of high-z candidates that has been completely characterised
with follow-up observations from the optical to the sub-millimetre domain.
Herschel/SPIRE observations at 250, 350 and 500 microns reveal the existence of
five sources producing a 500 microns emission excess that spatially corresponds
to the candidate proto-clusters discovered by Planck. Further observations at
CFHT in the optical bands (g and i) and in the near infrared (J, H and K_s),
plus mid infrared observations with IRAC/Spitzer (at 3.6 and 4.5 microns)
confirm that the sub-mm red excess is associated with an over-density of
colour-selected galaxies. Follow-up spectroscopy of 13 galaxies with
VLT/X-Shooter establishes the existence of two high-z structures: one at z~1.7
(three confirmed member galaxies), the other at z~2.0 (six confirmed members).
This double structure is also seen in the photometric redshift analysis of a
sample of 127 galaxies located inside a circular region of 1'-radius containing
the five Herschel/SPIRE sources, where we found a double-peaked excess of
galaxies at z~1.7 and z~2.0 with respect to the surrounding region. These
results suggest that PHz G95.5-61.6 corresponds to two accreting nodes, not
physically linked to one another, embedded in the large scale structure of the
Universe at z~2 and along the same line-of-sight. In conclusion, the data,
methods and results illustrated in this pilot project confirm that Planck data
can be used to detect the emission from clustered, dusty star forming galaxies
at high-z, and, thus, to pierce through the early growth of cluster-scale
structures.Comment: 15 pages, 13 figures. Accepted for publication in Astronomy and
Astrophysic
Caustics of Compensated Spherical Lens Models
We consider compensated spherical lens models and the caustic surfaces they
create in the past light cone. Examination of cusp and crossover angles
associated with particular source and lens redshifts gives explicit lensing
models that confirm previous claims that area distances can differ by
substantial factors from angular diameter distances even when averaged over
large angular scales. `Shrinking' in apparent sizes occurs, typically by a
factor of 3 for a single spherical lens, on the scale of the cusp caused by the
lens; summing over many lenses will still leave a residual effect.Comment: 21 pages, 5 ps figures, eps
Halpha-Derived Star-Formation Rates For Three z ~ 0.75 EDisCS Galaxy Clusters
We present Halpha-derived star-formation rates (SFRs) for three z ~ 0.75
galaxy clusters. Our 1 sigma flux limit corresponds to a star-formation rate of
0.10-0.24 solar mass per year, and our minimum reliable Halpha + [N II]
rest-frame equivalent width is 10\AA. We show that Halpha narrowband imaging is
an efficient method for measuring star formation in distant clusters. In two
out of three clusters, we find that the fraction of star-forming galaxies
increases with projected distance from the cluster center. We also find that
the fraction of star-forming galaxies decreases with increasing local galaxy
surface density in the same two clusters. We compare the median rate of star
formation among star-forming cluster galaxies to a small sample of star-forming
field galaxies from the literature and find that the median cluster SFRs are
\~50% less than the median field SFR. We characterize cluster evolution in
terms of the mass-normalized integrated cluster SFR and find that the z ~ 0.75
clusters have more SFR per cluster mass on average than the z <= 0.4 clusters
from the literature. The interpretation of this result is complicated by the
dependence of the mass-normalized SFR on cluster mass and the lack of
sufficient overlap in the mass ranges covered by the low and high redshift
samples. We find that the fraction and luminosities of the brightest starburst
galaxies at z ~ 0.75 are consistent with their being progenitors of the
post-starburst galaxies at z ~ 0.45 if the post-starburst phase lasts several
(~5) times longer than the starburst phase.Comment: Accepted for publication in ApJ, 20 pages, 24 figure
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
Chandra Observations of Galaxy Cluster Abell 2218
We present results from two observations (combined exposure of ~17 ks) of
galaxy cluster A2218 using the Advanced CCD Imaging Spectrometer on board the
Chandra X-ray Observatory that were taken on October 19, 1999. Using a
Raymond-Smith single temperature plasma model corrected for galactic absorption
we find a mean cluster temperature of kT = 6.9+/-0.5 keV, metallicity of
0.20+/-0.13 (errors are 90 % CL) and rest-frame luminosity in the 2-10 keV
energy band of 6.2x10^{44} erg/s in a LambdaCDM cosmology with H_0=65 km/s/Mpc.
The brightness distribution within 4'.2 of the cluster center is well fit by a
simple spherical beta model with core radius 66".4 and beta = 0.705 . High
resolution Chandra data of the inner 2' of the cluster show the x-ray
brightness centroid displaced ~22" from the dominant cD galaxy and the presence
of azimuthally asymmetric temperature variations along the direction of the
cluster mass elongation. X-ray and weak lensing mass estimates are in good
agreement for the outer parts (r > 200h^{-1}) of the cluster; however, in the
core the observed temperature distribution cannot reconcile the x-ray and
strong lensing mass estimates in any model in which the intracluster gas is in
thermal hydrostatic equilibrium. Our x-ray data are consistent with a scenario
in which recent merger activity in A2218 has produced both significant
non-thermal pressure in the core and substructure along the line of sight; each
of these phenomena probably contributes to the difference between lensing and
x-ray core mass estimates.Comment: 33 pages, 6 figures, uses AASTeX 5.02, ApJ submitte
LRG J0239-0134: A Ring Galaxy or a Pair of Superbubbles at z=1 ?
The unusual morphology of LRG J02390134 at =1.062 has been interpreted
as a ring galaxy. Here we propose an alternative idea that the ring-like
morphology is attributed to a pair of superbubbles driven by the intense
starburst in the central region of this galaxy. Supporting evidence for a
superbubble model is; 1) the poststarburst nature in the central body suggests
that a burst of supernova explosions could occur at least yr ago,
2) the dark lane seen in the central body suggests that we observe this object
from a nearly edge-on view, and, 3) the ring-like morphology is not
inconsistent with an idea that it is a pair of superbubbles. All these pieces
of evidence for the superbubble model seem circumstantial. However, if this is
the case, this galaxy provides an important example of the superwind activity
at high redshift.Comment: 5 pages (3 ps files are included) [emulateapj]. The Astrophysical
Journal (Letters), in pres
Caustic and Weak Lensing Estimators of Galaxy Cluster Masses
There are only two methods for estimating the mass distribution in the outer
regions of galaxy clusters, where virial equilibrium does not hold: weak
gravitational lensing and identification of caustics in redshift space. For the
first time, we apply both methods to three clusters: A2390, MS1358 and Cl 0024.
The two measures are in remarkably good agreement out to ~2 Mpc/h from the
cluster centers. This result demonstrates that the caustic technique is a
valuable complement to weak lensing. With a few tens of redshifts per (Mpc/h)^2
within the cluster, the caustic method is applicable for any z<~0.5.Comment: 5 pages, 1 figure, ApJ Letters, in pres
RC J0311+0507: A Candidate for Superpowerful Radio Galaxies in the Early Universe at Redshift z=4.514
A strong emission line at 6703A has been detected in the optical spectrum for
the host galaxy (R=23.1) of the radio source RC J0311+0507 (4C+04.11). This
radio galaxy, with a spectral index of 1.31 in the frequency range 365-4850
MHz, is one of the ultrasteep spectrum objects from the deep survey of a sky
strip conducted with RATAN-600 in 1980-1981. We present arguments in favor of
the identification of this line with Ly\alpha at redshift z=4.514. In this
case, the object belongs to the group of extremely distant radio galaxies of
ultrahigh radio luminosity (P_{1400}=1.3 x 10^{29}W Hz^{-1}). Such power can be
provided only by a fairly massive black hole (~10^9M_\sun}) that formed in a
time less than the age of the Universe at the observed z(1.3 Gyr) or had a
primordial origin.Comment: 8 pages, 3 figure
TIPS MEMILIH DAN MENYIMPAN TELUR YANG AMAN UNTUK DIKONSUSMI
Eggs are perfect foodstuffs because they contain nutrients such as protein, fat, vitamins, and minerals in sufficient quantities. Under certain conditions, the complete nutritional content in eggs can be a good growth medium for microorganisms. It is important to educate the community about how to differentiate egg quality and how to store eggs properly so that people can choose and get eggs of good quality in the long term. The benefit is that they can be more careful in choosing the eggs to buy, and know-how to store eggs properly so that the egg's shelf life can last longer. This education was carried out online during the Covid-19 pandemic Work From Home (WFH) period using the Zoom meet application. The participants in this counseling consisted of housewives and students
Discovery of a Very Bright Strongly-Lensed Galaxy Candidate at z ~ 7.6
Using HST and Spitzer IRAC imaging, we report the discovery of a very bright
strongly lensed Lyman break galaxy (LBG) candidate at z~7.6 in the field of the
massive galaxy cluster Abell 1689. The galaxy candidate, which we refer to as
A1689-zD1, shows a strong z-J break of at least 2.2 mag and is completely
undetected (<1 sigma) in HST/ACS g, r, i, and z-band data. These properties,
combined with the very blue J-H and H-[4.5] colors, are exactly the properties
of an z~7.6 LBG and can only be reasonably fit by a star-forming galaxy at
z=7.6 +/- 0.4. Attempts to reproduce these properties with a model galaxy at
z<4 yield particularly poor fits. A1689-zD1 has an observed (lensed) magnitude
of 24.7 AB (8 sigma) in the NICMOS H band and is ~1.3 mag brighter than the
brightest-known z-dropout galaxy. When corrected for the cluster magnification
of 9.3 at z~7.6, the candidate has an intrinsic magnitude of H=27.1 AB, or
about an L* galaxy at z~7.6. The source-plane deprojection shows that the star
formation is occurring in compact knots of size ~<300 pc. The best-fit stellar
population synthesis models yield a median redshift of 7.6, stellar masses
(1.6-3.9) x 10^9 M_sun, stellar ages 45-320 Myr, star-formation rates ~<7.6
M_sun/yr, and low reddening with A_V <= 0.3. These properties are generally
similar to those of LBGs found at z~5-6. The inferred stellar ages suggest a
formation redshift of z~8-10 (t~<0.63 Gyr). A1689-zD1 is the brightest
observed, highly reliable z>7.0 galaxy candidate found to date.Comment: Accepted for publication in the Astrophysical Journal, 8 pages, 8
figures, updated to match version in pres
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