426 research outputs found
The ALMA Frontier Fields Survey - IV. Lensing-corrected 1.1 mm number counts in Abell 2744, MACSJ0416.1-2403 and MACSJ1149.5+2223
[abridged] Characterizing the number counts of faint, dusty star-forming
galaxies is currently a challenge even for deep, high-resolution observations
in the FIR-to-mm regime. They are predicted to account for approximately half
of the total extragalactic background light at those wavelengths. Searching for
dusty star-forming galaxies behind massive galaxy clusters benefits from strong
lensing, enhancing their measured emission while increasing spatial resolution.
Derived number counts depend, however, on mass reconstruction models that
properly constrain these clusters. We estimate the 1.1 mm number counts along
the line of sight of three galaxy clusters, i.e. Abell 2744, MACSJ0416.1-2403
and MACSJ1149.5+2223, which are part of the ALMA Frontier Fields Survey. We
perform detailed simulations to correct these counts for lensing effects. We
use several publicly available lensing models for the galaxy clusters to derive
the intrinsic flux densities of our sources. We perform Monte Carlo simulations
of the number counts for a detailed treatment of the uncertainties in the
magnifications and adopted source redshifts. We find an overall agreement among
the number counts derived for the different lens models, despite their
systematic variations regarding source magnifications and effective areas. Our
number counts span ~2.5 dex in demagnified flux density, from several mJy down
to tens of uJy. Our number counts are consistent with recent estimates from
deep ALMA observations at a 3 level. Below 0.1 mJy, however,
our cumulative counts are lower by 1 dex, suggesting a flattening in
the number counts. In our deepest ALMA mosaic, we estimate number counts for
intrinsic flux densities 4 times fainter than the rms level. This
highlights the potential of probing the sub-10 uJy population in larger samples
of galaxy cluster fields with deeper ALMA observations.Comment: 19 pages, 14 figures, 3 tables. Accepted for publication in A&
The evolution of Balmer jump selected galaxies in the ALHAMBRA survey
We present a new color-selection technique, based on the Bruzual & Charlot
models convolved with the bands of the ALHAMBRA survey, and the redshifted
position of the Balmer jump to select star-forming galaxies in the redshift
range 0.5 < z < 1.5. These galaxies are dubbed Balmer jump Galaxies BJGs. We
apply the iSEDfit Bayesian approach to fit each detailed SED and determine
star-formation rate (SFR), stellar mass, age and absolute magnitudes. The mass
of the haloes where these samples reside are found via a clustering analysis.
Five volume-limited BJG sub-samples with different mean redshifts are found to
reside in haloes of median masses slightly
increasing toward z=0.5. This increment is similar to numerical simulations
results which suggests that we are tracing the evolution of an evolving
population of haloes as they grow to reach a mass of at z=0.5. The likely progenitors of our samples at z3 are Lyman
Break Galaxies, which at z2 would evolve into star-forming BzK galaxies,
and their descendants in the local Universe are elliptical galaxies.Hence, this
allows us to follow the putative evolution of the SFR, stellar mass and age of
these galaxies. From z1.0 to z0.5, the stellar mass of the volume
limited BJG samples nearly does not change with redshift, suggesting that major
mergers play a minor role on the evolution of these galaxies. The SFR evolution
accounts for the small variations of stellar mass, suggesting that star
formation and possible minor mergers are the main channels of mass assembly.Comment: 14 pages, 10 figures. Submitted to A&A. It includes first referee's
comments. Abstract abridged due to arXiv requirement
Endogenous GABA controls oligodendrocyte lineage cell number, myelination, and CNS internode length
Adjusting the thickness and internodal length of the myelin sheath is a mechanism for tuning the conduction velocity of axons to match computational needs. Interactions between oligodendrocyte precursor cells (OPCs) and developing axons regulate the formation of myelin around axons. We now show, using organotypic cerebral cortex slices from mice expressing eGFP in Sox10-positive oligodendrocytes, that endogenously released GABA, acting on GABAA receptors, greatly reduces the number of oligodendrocyte lineage cells. The decrease in oligodendrocyte number correlates with a reduction in the amount of myelination but also an increase in internode length, a parameter previously thought to be set by the axon diameter or to be a property intrinsic to oligodendrocytes. Importantly, while TTX block of neuronal activity had no effect on oligodendrocyte lineage cell number when applied alone, it was able to completely abolish the effect of blocking GABAA receptors, suggesting that control of myelination by endogenous GABA may require a permissive factor to be released from axons. In contrast, block of AMPA/KA receptors had no effect on oligodendrocyte lineage cell number or myelination. These results imply that, during development, GABA can act as a local environmental cue to control myelination and thus influence the conduction velocity of action potentials within the CNS. GLIA 2017;65:309-321
Adrenalectomy promotes a permanent decrease of plasma corticoid levels and a transient increase of apoptosis and the expression of Transforming Growth Factor β1 (TGF-β1) in hippocampus: effect of a TGF-β1 oligo-antisense
BACKGROUND: Corticosterone reduction produced by adrenalectomy (ADX) induces apoptosis in dentate gyrus (DG) of the hippocampus, an effect related to an increase in the expression of the pro-apoptotic gene bax. However it has been reported that there is also an increase of the anti-apoptotic gene bcl-2, suggesting the promotion of a neuroprotective phenomenon, perhaps related to the expression of transforming growth factor β1 (TGF-β1). Thus, we have investigated whether TGF-β1 levels are induced by ADX, and whether apoptosis is increased by blocking the expression of TGF-β1 with an antisense oligonucleotide (ASO) administered intracerebrally in corticosterone depleted rats. RESULTS: It was observed an increase of apoptosis in DG, 2 and 5 days after ADX, in agreement with a reduction of corticosterone levels. However, the effect of ADX on the number of apoptotic positive cells in DG was decreased 5 days after the lesion. In CA1–CA3 regions, the effect was only observed 2 days after ADX. TGF-β1 mRNA levels were increased 2 days after ADX. The sustained intracerebro-ventricular administration of a TGF-β1 ASO via an osmotic mini pump increased apoptosis levels in CA and DG regions 5 days after ADX as well as sham-operated control animals. No significant effect was observed following a scrambled-oligodeoxynucleotide treatment. CONCLUSION: The changes in both the pattern and the magnitude of apoptotic-cell morphology observed 2 and 5 days after ADX suggest that, as a consequence of the reduction of corticosteroids, some trophic mechanisms restricting cell death to a particular time window are elicited. Sustained intracerebral administration of TGF-β1 ASO increased the apoptosis promoted by ADX, suggesting that TGF-β1 plays an anti-apoptotic role in vivo in hippocampus
Tunneling dynamics in exactly-solvable models with triple-well potentials
Inspired by new trends in atomtronics, cold atoms devices and Bose-Einstein
condensate dynamics, we apply a general technique of N=4 extended
Supersymmetric Quantum Mechanics to isospectral Hamiltonians with triple-well
potentials, i.e. symmetric and asymmetric. Expressions of quantum-mechanical
propagators, which take into account all states of the spectrum, are obtained,
within the N = 4 SQM approach, in the closed form. For the initial Hamiltonian
of a harmonic oscillator, we obtain the explicit expressions of potentials,
wavefunctions and propagators. The obtained results are applied to tunneling
dynamics of localized states in triple-well potentials and for studying its
features. In particular, we observe a Josephson-type tunneling transition of a
wave packet, the effect of its partial trapping and a non-monotonic dependence
of tunneling dynamics on the shape of a three-well potential. We investigate,
among others, the possibility of controlling tunneling transport by changing
parameters of the central well, and we briefly discuss potential applications
of this aspect to atomtronic devices.Comment: Latex, 28 pages, 7 Figs, 2 Tables; minor presentation changes,
journal versio
X-ray, UV, and optical observations of the accretion disk and boundary layer in the symbiotic star RT Crucis
Compared to mass transfer in cataclysmic variables, the nature of accretion in symbiotic binaries in which red giants transfer material to white dwarfs (WDs) has been difficult to uncover. The accretion flows in a symbiotic binary are most clearly observable, however, when there is no quasi-steady shell burning on the WD to hide them. RT Cru is the prototype of such non-burning symbiotics, with its hard (δ-type) X-ray emission providing a view of its innermost accretion structures. In the past 20 yr, RT Cru has experienced two similar optical brightening events, separated by ∼ 4000 days and with amplitudes of ΔV ∼ 1.5 mag. After Swift became operative, the Burst Alert Telescope (BAT) detector revealed a hard X-ray brightening event almost in coincidence with the second optical peak. Spectral and timing analyses of multi-wavelength observations that we describe here, from NuSTAR, Suzaku, Swift/X-Ray Telescope (XRT) + BAT + UltraViolet Optical Telescope (UVOT) (photometry) and optical photometry and spectroscopy, indicate that accretion proceeds through a disk that reaches down to the WD surface. The scenario in which a massive, magnetic WD accretes from a magnetically truncated accretion disk is not supported. For example, none of our data show the minute-time-scale periodic modulations (with tight upper limits from X-ray data) expected from a spinning, magnetic WD. Moreover, the similarity of the UV and X-ray fluxes, as well as the approximate constancy of the hardness ratio within the BAT band, indicate that the boundary layer of the accretion disk remained optically thin to its own radiation throughout the brightening event, during which the rate of accretion onto the WD increased to 6.7 × 10-9M· yr-1 (d/2 kpc)2. For the first time from a WD symbiotic, the NuSTAR spectrum showed a Compton reflection hump at E > 10 keV, due to hard X-rays from the boundary layer reflecting off of the surface of the WD; the reflection amplitude was 0.77 ± 0.21. The best fit spectral model, including reflection, gave a maximum post-shock temperature of kT = 53 ± 4 keV, which implies a WD mass of 1.25 ± 0.02 M·. Although the long-term optical variability in RT Cru is reminiscent of dwarf-novae-type outbursts, the hard X-ray behavior does not correspond to that observed in well-known dwarf nova. An alternative explanation for the brightening events could be that they are due to an enhancement of the accretion rate as the WD travels through the red giant wind in a wide orbit, with a period of about ∼4000 days. In either case, the constancy of the hard X-ray spectrum while the accretion rate rose suggests that the accretion-rate threshold between a mostly optically thin and thick boundary layer, in this object, may be higher than previously thought.Fil: Luna, Gerardo Juan Manuel. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Mukai, K.. National Aeronautics and Space Administration; Estados UnidosFil: Sokoloski, J. L.. Columbia University; Estados UnidosFil: Lucy, A. B.. Columbia University; Estados UnidosFil: Cusumano, G.. Istituto Nazionale di Astrofisica; ItaliaFil: Segreto, A.. Istituto Nazionale di Astrofisica; ItaliaFil: Jaque Arancibia, Marcelo Daniel. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Nuñez, Natalia Edith. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Puebla, R. E.. Universidad Central del Ecuador; EcuadorFil: Nelson, T.. University of Pittsburgh at Johnstown; Estados UnidosFil: Walter, F. M.. Columbia University; Estados Unido
The ALMA Frontier Fields Survey
CONTEXT: Dusty star-forming galaxies are among the most prodigious systems at high redshift (z > 1), characterized by high star-formation rates and huge dust reservoirs. The bright end of this population has been well characterized in recent years, but considerable uncertainties remain for fainter dusty star-forming galaxies, which are responsible for the bulk of star formation at high redshift and thus play a key role in galaxy growth and evolution.
AIMS: In this first paper of our series, we describe our methods for finding high redshift faint dusty galaxies using millimeter observations with ALMA.
METHODS: We obtained ALMA 1.1 mm mosaic images for three strong-lensing galaxy clusters from the Frontier Fields Survey, which constitute some of the best studied gravitational lenses to date. The ≈2′ × 2′ mosaics overlap with the deep HST WFC3/IR footprints and encompass the high magnification regions of each cluster for maximum intrinsic source sensitivity. The combination of extremely high ALMA sensitivity and the magnification power of these clusters allows us to systematically probe the sub-mJy population of dusty star-forming galaxies over a large surveyed area.
RESULTS: We present a description of the reduction and analysis of the ALMA continuum observations for the galaxy clusters Abell 2744 (z = 0.308), MACS J0416.1-2403 (z = 0.396) and MACS J1149.5+2223 (z = 0.543), for which we reach observed rms sensitivities of 55, 59 and 71 μJy beam-1 respectively. We detect 12 dusty star-forming galaxies at S/N ≥ 5.0 across the three clusters, all of them presenting coincidence with near-infrared detected counterparts in the HST images. None of the sources fall close to the lensing caustics, thus they are not strongly lensed. The observed 1.1 mm flux densities for the total sample of galaxies range from 0.41 to 2.82 mJy, with observed effective radii spanning ≲0.̋05 to 0.̋37 ± 0.̋21 . The lensing-corrected sizes of the detected sources appear to be in the same range as those measured in brighter samples, albeit with possibly larger dispersion
Multiwavelength monitoring of the nucleus in PBC J2333.9-2343: the giant radio galaxy with a blazar-like core
PBC J2333.9-2343 is a giant radio galaxy at z = 0.047 with a bright central
core associated to a blazar nucleus. If the nuclear blazar jet is a new phase
of the jet activity, then the small orientation angle suggest a dramatic change
of the jet direction. We present observations obtained between September 2018
and January 2019 (cadence larger than three days) with Effeslberg, SMARTS-1.3m,
ZTF, ATLAS, Swift, and Fermi-LAT, and between April-July 2019 (daily cadence)
with SMARTS-1.3m and ATLAS. Large (>2x) flux increases are observed on
timescales shorter than a month, which are interpreted as flaring events. The
cross correlation between the SMARTS-1.3m monitoring in the NIR and optical
shows that these data do not show significant time lag within the measured
errors. A comparison of the optical variability properties between non-blazars
and blazars AGN shows that PBC J2333.9-2343 has properties more comparable to
the latter. The SED of the nucleus shows two peaks, that were fitted with a one
zone leptonic model. Our data and modelling shows that the high energy peak is
dominated by External Compton from the dusty torus with mild contribution from
Inverse Compton from the jet. The derived jet angle of 3 degrees is also
typical of a blazar. Therefore, we confirm the presence of a blazar-like core
in the center of this giant radio galaxy, likely a Flat Spectrum Radio Quasar
with peculiar properties.Comment: Accepted for publication in MNRAS. 15 pages, 6 figures, 2 appendix
including tables and figure
Persistent and occasional: searching for the variable population of the ZTF/4MOST sky using ZTF data release 11
We present a variability, color and morphology based classifier, designed to
identify transients, persistently variable, and non-variable sources, from the
Zwicky Transient Facility (ZTF) Data Release 11 (DR11) light curves of extended
and point sources. The main motivation to develop this model was to identify
active galactic nuclei (AGN) at different redshift ranges to be observed by the
4MOST ChANGES project. Still, it serves as a more general time-domain astronomy
study. The model uses nine colors computed from CatWISE and PS1, a morphology
score from PS1, and 61 single-band variability features computed from the ZTF
DR11 g and r light curves. We trained two versions of the model, one for each
ZTF band. We used a hierarchical local classifier per parent node approach,
where each node was composed of a balanced random forest model. We adopted a
17-class taxonomy, including non-variable stars and galaxies, three transient
classes, five classes of stochastic variables, and seven classes of periodic
variables. The macro averaged precision, recall and F1-score are 0.61, 0.75,
and 0.62 for the g-band model, and 0.60, 0.74, and 0.61, for the r-band model.
When grouping the four AGN classes into one single class, its precision,
recall, and F1-score are 1.00, 0.95, and 0.97, respectively, for both the g and
r bands. We applied the model to all the sources in the ZTF/4MOST overlapping
sky, avoiding ZTF fields covering the Galactic bulge, including 86,576,577
light curves in the g-band and 140,409,824 in the r-band. Only 0.73\% of the
g-band light curves and 2.62\% of the r-band light curves were classified as
stochastic, periodic, or transient with high probability ().
We found that, in general, more reliable results are obtained when using the
g-band model. Using the latter, we identified 384,242 AGN candidates, 287,156
of which have .Comment: Accepted for publication in Astronomy & Astrophysics. Abstract
shortened for arXiv. Tables containing the classifications and features for
the ZTF g and r bands, and the labeled sets will be available at CDS.
Individual catalogs per class and band, as well as the labeled set catalogs,
can be downloaded at Zenodo DOI:10.5281/zenodo.782604
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