397 research outputs found
Preprint arXiv: 2204.02923 Submitted on 6 Apr 2022
We present an ansatz for the ground states of the Quantum Sherrington-Kirkpatrick model, a paradigmatic model for quantum spin glasses. Our ansatz, based on the concept of generalized coherent states, very well captures the fundamental aspects of the model, including the ground state energy and the position of the spin glass phase transition. It further enables us to study some previously unexplored features, such as the non-vanishing longitudinal field regime and the entanglement structure of the ground states. We find that the ground state entanglement can be captured by a simple ensemble of weighted graph states with normally distributed phase gates, leading to a volume law entanglement, contrasting with predictions based on entanglement monogamy
Limits on the LyC signal from z~3 sources with secure redshift and HST coverage in the E-CDFS field
Aim: We aim to measure the LyC signal from a sample of sources in the Chandra
deep field south. We collect star-forming galaxies (SFGs) and active galactic
nuclei (AGN) with accurate spectroscopic redshifts, for which Hubble Space
Telescope (HST) coverage and multi-wavelength photometry are available. Method:
We selected a sample of about 200 sources at z~3. Taking advantage of HST
resolution, we applied a careful cleaning procedure and rejected sources
showing nearby clumps with different colours, which could be lower-z
interlopers. Our clean sample consisted of 86 SFGs (including 19 narrow-band
selected Lya emitters) and 8 AGN (including 6 detected in X-rays). We measured
the LyC flux from aperture photometry in four narrow-band filters covering
wavelengths below a 912 A rest frame (3.11<z<3.53). We estimated the ratio
between ionizing (LyC flux) and 1400 A non-ionizing emissions for AGN and
galaxies. Results: By running population synthesis models, we assume an average
intrinsic L(1400 A)/L(900 A) ratio of 5 as the representative value for our
sample. With this value and an average treatment of the lines of sight of the
inter-galactic medium, we estimate the LyC escape fraction relative to the
intrinsic value (fesc_rel(LyC)). We do not directly detect ionizing radiation
from any individual SFG, but we are able to set a 1(2)sigma upper limit of
fesc_rel(LyC)<12(24)%. This result is consistent with other non-detections
published in the literature. No meaningful limits can be calculated for the
sub-sample of Lya emitters. We obtain one significant direct detection for an
AGN at z=3.46, with fesc_rel(LyC) = (72+/-18)%. Conclusions: Our upper limit on
fescrel(LyC) implies that the SFGs studied here do not present either the
physical properties or the geometric conditions suitable for efficient
LyC-photon escape.Comment: Accepted for publication in A&A on Jan 5th, 201
Antipodean Theory for Educational Research
published_or_final_versio
Constraining Lyman-alpha spatial offsets at from VANDELS slit spectroscopy
We constrain the distribution of spatially offset Lyman-alpha emission
(Ly) relative to rest-frame ultraviolet emission in high
redshift () Lyman-break galaxies (LBGs) exhibiting Ly emission
from VANDELS, a VLT/VIMOS slit-spectroscopic survey of the CANDELS Ultra Deep
Survey and Chandra Deep Field South fields (
total). Because slit spectroscopy compresses two-dimensional spatial
information into one spatial dimension, we use Bayesian inference to recover
the underlying Ly spatial offset distribution. We model the
distribution using a 2D circular Gaussian, defined by a single parameter
, the standard deviation expressed in polar
coordinates. Over the entire redshift range of our sample (), we find
kpc ( conf.),
corresponding to arcsec at . We also find that
decreases significantly with redshift. Because
Ly spatial offsets can cause slit-losses, the decrease in
with redshift can partially explain the increase
in the fraction of Ly emitters observed in the literature over this
same interval, although uncertainties are still too large to reach a strong
conclusion. If continues to decrease into the
reionization epoch, then the decrease in Ly transmission from galaxies
observed during this epoch might require an even higher neutral hydrogen
fraction than what is currently inferred. Conversely, if spatial offsets
increase with the increasing opacity of the IGM, slit losses may explain some
of the drop in Ly transmission observed at . Spatially resolved
observations of Ly and UV continuum at are needed to settle the
issue.Comment: Submitted to MNRA
The VANDELS survey: A strong correlation between Ly equivalent width and stellar metallicity at
We present the results of a new study investigating the relationship between
observed Ly equivalent width ((Ly)) and the
metallicity of the ionizing stellar population () for a sample of
star-forming galaxies at drawn from the VANDELS survey.
Dividing our sample into quartiles of rest-frame (Ly)
across the range -58 \unicode{xC5} \lesssim (Ly)
\lesssim 110 \unicode{xC5} we determine from full spectral
fitting of composite far-ultraviolet (FUV) spectra and find a clear
anti-correlation between (Ly) and . Our results
indicate that decreases by a factor between the lowest
(Ly) quartile
((Ly)\rangle=-18\unicode{xC5}) and the highest
(Ly) quartile
((Ly)\rangle=24\unicode{xC5}). Similarly,
galaxies typically defined as Lyman Alpha Emitters (LAEs;
(Ly) >20\unicode{xC5}) are, on average, metal poor with
respect to the non-LAE galaxy population ((Ly)
\leq20\unicode{xC5}) with
. Finally, based on the best-fitting stellar models, we
estimate that the increasing strength of the stellar ionizing spectrum towards
lower is responsible for of the observed variation
in (Ly) across our sample, with the remaining contribution
() being due to a decrease in the HI/dust covering fractions in
low galaxies.Comment: 10 pages, 6 figures, MNRAS accepte
Physical properties of Lyman-alpha emitters at from UV-to-FIR measurements
The analysis of the physical properties of low-redshift Ly emitters
(LAEs) can provide clues in the study of their high-redshift analogues. At , LAEs are bright enough to be detected over almost the entire
electromagnetic spectrum and it is possible to carry out a more precise and
complete study than at higher redshifts. In this study, we examine the UV and
IR emission, dust attenuation, SFR and morphology of a sample of 23
GALEX-discovered star-forming (SF) LAEs at with direct UV (GALEX),
optical (ACS) and FIR (PACS and MIPS) data. Using the same UV and IR limiting
luminosities, we find that LAEs at tend to be less dusty, have
slightly higher total SFRs, have bluer UV continuum slopes, and are much
smaller than other galaxies that do not exhibit Ly emission in their
spectrum (non-LAEs). These results suggest that at Ly
photons tend to escape from small galaxies with low dust attenuation. Regarding
their morphology, LAEs belong to Irr/merger classes, unlike non-LAEs. Size and
morphology represent the most noticeable difference between LAEs and non-LAEs
at . Furthermore, the comparison of our results with those obtained
at higher redshifts indicates that either the Ly technique picks up
different kind of galaxies at different redshifts or that the physical
properties of LAEs are evolving with redshift.Comment: Accepted for publication in Ap
Adipose-Derived Fatty Acid-Binding Proteins Plasma Concentrations Are Increased in Breast Cancer Patients.
BACKGROUND: Adipose tissue is an endocrine organ that could play a role in tumor progression via its secreted adipokines. The role of adipose-derived fatty acid-binding protein (FABP) 4 and FABP5 in breast cancer is presently under study, but their circulating levels in this pathology are poorly known. We analyzed the blood concentrations of FABP4 and FABP5 in breast cancer patients to determine whether there is an association between them and breast cancer. MATERIALS AND METHODS: We studied 294 women in the oncology department with a family history of breast cancer; 198 of the women had breast cancer, and 96 were healthy controls. The levels of FABP4, FABP5, lipid profile, standard biochemical parameter, and high-sensitivity C-reactive protein (hsCRP) were determined. We analyzed the association of FABP4 and FABP5 with breast cancer, while adjusting for demographic, anthropometric, and biochemical parameters. RESULTS: Breast cancer patients had a 24.8% (pâ<â.0001) and 11.4% (pâ<â.05) higher blood concentration of FABP4 and FABP5, respectively. Fatty acid-binding protein 4 was positively associated with age, body mass index (BMI), FABP5, very-low-density lipoprotein cholesterol (VLDLc), non-high-density lipoprote in cholesterol (non-HDLc), Apolipoprotein B 100 (ApoB100), triglycerides, glycerol, glucose, and hsCRP (pâ<â.05), and was negatively associated with HDLc (pâ<â.005) in breast cancer patients. Fatty acid-binding protein 5 was positively associated with BMI, FABP4, VLDLc, triglycerides, glycerol, and hsCRP (pâ<â.05), and was negatively associated with HDLc and Apolipoprotein AI (ApoAI) (pâ<â.05) in breast cancer patients. Using a logistic regression analysis and adjusting for age, BMI, hsCRP, non-HDLc, and triglycerides, FABP4 was independently associated with breast cancer (odds ratio [OR]: 1.091 [95% CI: 1.037-1.149]). Moreover, total cholesterol, VLDLc, non-HDLc, ApoB100, triglycerides, and hsCRP were significantly increased in breast cancer patients (pâ<â.005). In contrast, the non-esterified fatty acids concentrations were significantly decreased in breast cancer patients (pâ<â.05). CONCLUSION: Circulating FABP4 and FABP5 levels were increased in breast cancer patients compared with controls. The positive association of FABP4 with breast cancer was maintained after adjusting for important covariates, while the association with FABP5 was lost. Our data reinforce the role of adipose tissue and their adipokines in breast cancer. Despite these data, further studies must be performed to better explain the prognosis or diagnostic value of these blood parameters and their possible role in breast cancer. IMPLICATIONS FOR PRACTICE: We focus on the effect of adipose tissue on cancer, which is increasingly recognized. The association between adipocyte-derived adipokines and breast cancer opens new diagnosis and therapy perspectives. In this study, we provide original data concerning FABP4 and FABP5 plasma concentrations in breast cancer patients. Compared to control group, breast cancer patients show higher FABP4 and FABP5 blood levels. Our data suggest that, particularly, circulating FABP4 levels could be considered a new independent breast cancer biomarker. Our work translates basic science data to clinic linking the relationship between adipose tissue and lipid metabolism to breast cancer
PACS-Herschel FIR detections of Lyman-alpha emitters at 2.0<z<3.5
In this work we analyze the physical properties of a sample of 56
spectroscopically selected star-forming (SF) Ly emitting galaxies at
2.0z3.5 using both a spectral energy distribution (SED)
fitting procedure from rest-frame UV to mid-IR and direct 160m
observations taken with the Photodetector Array Camera & Spectrometer (PACS)
instrument onboard \emph{Herschel Space Observatory}. We define LAEs as those
Ly emitting galaxies whose rest-frame Ly equivalent widths
(Ly EW) are above 20\AA, the typical threshold in
narrow-band searches. Ly emitting galaxies with Ly
EW are called non-LAEs. As a result of an individual SED fitting
for each object, we find that the studied sample of LAEs contains galaxies with
ages mostly below 100Myr and a wide variety of dust attenuations, SFRs, and
stellar masses. The heterogeneity in the physical properties is also seen in
the morphology, ranging from bulge-like galaxies to highly clumpy systems. In
this way, we find that LAEs at 2.0z3.5 are very diverse,
and do not have a bimodal nature, as suggested in previous works. Furthermore,
the main difference between LAEs and non-LAEs is their dust attenuation,
because LAEs are not as dusty as non-LAEs. On the FIR side, four galaxies of
the sample (two LAEs and two non-LAEs) have PACS-FIR counterparts. Their total
IR luminosity place all of them in the ULIRG regime and are all dusty objects,
with A4mag. This is an indication from direct FIR
measurements that dust and Ly emission are not mutually exclusive. This
population of red and dusty LAEs is not seen at z0.3, suggesting an
evolution with redshift of the IR nature of galaxies selected via their
Ly emission.Comment: Accepted for publication in A&
The VIMOS Ultra Deep Survey: Ly Emission and Stellar Populations of Star-Forming Galaxies at 2<z<2.5
The aim of this paper is to investigate spectral and photometric properties
of 854 faint (<~25 mag) star-forming galaxies (SFGs) at 2<z<2.5 using
the VIMOS Ultra-Deep Survey (VUDS) spectroscopic data and deep multi-wavelength
photometric data in three extensively studied extragalactic fields (ECDFS,
VVDS, COSMOS). These SFGs were targeted for spectroscopy based on their
photometric redshifts. The VUDS spectra are used to measure the UV spectral
slopes () as well as Ly equivalent widths (EW). On average, the
spectroscopically measured (-1.360.02), is comparable to the
photometrically measured (-1.320.02), and has smaller measurement
uncertainties. The positive correlation of with the Spectral Energy
Distribution (SED)-based measurement of dust extinction, E(B-V),
emphasizes the importance of as an alternative dust indicator at high
redshifts. To make a proper comparison, we divide these SFGs into three
subgroups based on their rest-frame Ly EW: SFGs with no Ly
emission (SFG; EW0\AA), SFGs with Ly emission (SFG; EW0\AA), and Ly emitters (LAEs; EW20\AA). The fraction of
LAEs at these redshifts is 10%, which is consistent with previous
observations. We compared best-fit SED-estimated stellar parameters of the
SFG, SFG and LAE samples. For the luminosities probed here
(L), we find that galaxies with and without Ly in emission
have small but significant differences in their SED-based properties. We find
that LAEs have less dust, and lower star-formation rates (SFR) compared to
non-LAEs. We also find that LAEs are less massive compared to non-LAEs, though
the difference is smaller and less significant compared to the SFR and E(B-V). [abridged]Comment: Accepted for publication in A&A, 19 pages, 10 figures, 1 tabl
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