Context. High resolution spectroscopy at high signal-to-noise ratios (S/Ns) is one the key techniques of the quantitative study of the atmospheres of extrasolar planets. Observations at near-infrared ...wavelengths with fiber-fed spectrographs coupled to extremely large telescopes are particularly important to tackle the ultimate goal of detecting biosignatures in rocky planets. Aims. To achieve high S/Ns in fiber-fed spectrogrpahs, the systematic noise effects introduced by the fibers must be properly understood and mitigated. In this paper we concentrate on the effects of modal noise in multimode fibers. Methods. Starting from our puzzling on-sky experience with the GIANO-TNG spectrometer we set up an infrared high resolution spectrometer in our laboratory and used this instrument to characterize the modal noise generated in fibers of different types (circular and octagonal) and sizes. Our experiment includes two conventional scrambling systems for fibers: a mechanical agitator and an optical double scrambler. Results. We find that the strength of the modal noise primarily depends on how the fiber is illuminated. It dramatically increases when the fiber is under-illuminated, either in the near field or in the far field. The modal noise is similar in circular and octagonal fibers. The Fourier spectrum of the noise decreases exponentially with frequency; i.e., the modal noise is not white but favors broad spectral features. Using the optical double scrambler has no effect on modal noise. The mechanical agitator has effects that vary between different types of fibers and input illuminations. In some cases this agitator has virtually no effect. In other cases, it mitigates the modal noise, but flattens the noise spectrum in Fourier space; i.e., the mechanical agitator preferentially filters the broad spectral features. Conclusions. Our results show that modal noise is frustratingly insensitive to the use of octagonal fibers and optical double scramblers; i.e., the conventional systems used to improve the performances of spectrographs fed via unevenly illuminated fibers. Fiber agitation may help in some cases, but its effect has to be verified on a case-by-case basis. More generally, our results indicate that the design of the fiber link feeding a spectrograph should be coupled with laboratory measurements that reproduce, as closely as possible, the conditions expected at the telescope.
The use of darbepoetin alfa to treat anemia in patients with lower-risk myelodysplastic syndromes (MDS) was evaluated in a phase 3 trial. Eligible patients had low/intermediate-1 risk MDS, hemoglobin ...⩽10 g/dl, low transfusion burden and serum erythropoietin (EPO) ⩽500 mU/ml. Patients were randomized 2:1 to receive 24 weeks of subcutaneous darbepoetin alfa 500 μg or placebo every 3 weeks (Q3W), followed by 48 weeks of open-label darbepoetin alfa. A total of 147 patients were randomized, with median hemoglobin of 9.3 (Q1:8.8, Q3:9.7) g/dl and median baseline serum EPO of 69 (Q1:36, Q3:158) mU/ml. Transfusion incidence from weeks 5-24 was significantly lower with darbepoetin alfa versus placebo (36.1% (35/97) versus 59.2% (29/49), P=0.008) and erythroid response rates increased significantly with darbepoetin alfa (14.7% (11/75 evaluable) versus 0% (0/35 evaluable), P=0.016). In the 48-week open-label period, dose frequency increased from Q3W to Q2W in 81% (102/126) of patients; this was associated with a higher hematologic improvement-erythroid response rate (34.7% (34/98)). Safety results were consistent with a previous darbepoetin alfa phase 2 MDS trial. In conclusion, 24 weeks of darbepoetin alfa Q3W significantly reduced transfusions and increased rates of erythroid response with no new safety signals in lower-risk MDS (registered as EudraCT#2009-016522-14 and NCT#01362140).
Approximately 5% of gynecological malignancies are associated with paraneoplastic hypercalcemia. Awareness of its association with certain tumor types allows for earlier disease detection and ...facilitates monitoring of treatment response and disease recurrence. We review the salient clinicopathological features, differential diagnosis and management issues in some of these gynecological tumors, namely: small cell carcinoma, hypercalcemic type; ovarian clear cell carcinoma, dysgerminoma and juvenile granulosa cell tumors.
We present Spitzer IRS low resolution, mid-IR spectra of a sample of 25 high luminosity QSOs at $2<z<3.5$. When combined with archival IRS observations of local, low luminosity type-I active galactic ...nuclei (AGNs), the sample spans five orders of magnitude in luminosity. We find that the continuum dust thermal emission at $\rm \lambda _{rest}=6.7~\mu m$ is correlated with the optical luminosity, following the non-linear relation $\lambda L_{\lambda}(6.7~\mu{\rm m}) \propto \lambda L_{\lambda}(5100~\AA)^{0.82}$. We also find an anti correlation between $\lambda L_{\lambda}(6.7~\mu{\rm m})/\lambda L_{\lambda}(5100~\AA)$ and the Oiiiλ5007 line luminosity. These effects are interpreted as a decreasing covering factor of the circumnuclear dust as a function of luminosity. Such a result is in agreement with the decreasing fraction of absorbed AGNs as a function of luminosity recently found in various surveys. In particular, while X-ray surveys find a decreasing covering factor of the absorbing gas as a function of luminosity, our data provides an independent and complementary confirmation by finding a decreasing covering factor of dust. We clearly detect the silicate emission feature in the average spectrum, but also in four individual objects. These are the silicate emission in the most luminous objects obtained so far. When combined with the silicate emission observed in local, low luminosity type-I AGNs, we find that the silicate emission strength is correlated with luminosity. The silicate strength of all type-I AGNs also follows a positive correlation with the black hole mass and with the accretion rate. The Polycyclic Aromatic Hydrocarbon (PAH) emission features, expected from starburst activity, are not detected in the average spectrum of luminous, high-z QSOs. The upper limit inferred from the average spectrum points to a ratio between PAH luminosity and QSO optical luminosity significantly lower than observed in lower luminosity AGNs, implying that the correlation between star formation rate and AGN power saturates at high luminosities.
We obtained optical/near-IR rest-frame Magellan FIRE spectra (including Paβ and Paγ) of 25 starburst galaxies at 0.5 < z < 0.9, with average star formation rates (SFRs) seven times above the main ...sequence (MS). We find that Paschen-to-Balmer line ratios saturate around a constant value corresponding to AV ∼ 2-3 mag, while line-to-IR-luminosity ratios suggest a large range of more extreme obscurations and appear to be uncorrelated with the former. This behavior is not consistent with standard attenuation laws derived for local and distant galaxies, yet is remarkably consistent with observations of starburst cores in which young stars and dust are homogeneously mixed. This model implies AV = 2-30 mag attenuation to the center of starburst cores, with a median of ∼9 mag (a factor of 4000). X-ray hardness ratios for six AGNs in our sample and column densities derived from observed dust masses and radio sizes independently confirm this level of attenuation. In these conditions observed optical/near-IR emission comes from surface regions, while inner starburst cores are invisible. We thus attribute the high N ii/H ratios to widespread shocks from accretion, turbulence, and dynamic disturbances rather than to AGNs. The large range of optical depths demonstrates that substantial diversity is present within the starburst population, possibly connected to different merger phases or progenitor properties. The majority of our targets are, in fact, morphologically classified as mergers. We argue that the extreme obscuration provides in itself smoking gun evidence of their merger origin, and a powerful tool for identifying mergers at even higher redshifts.
Abstract
We present the first systematic study of lithium abundance in a chemically homogeneous sample of 27 red supergiants (RSGs) in the young Perseus complex. For these stars, accurate stellar ...parameters and detailed chemical abundances of iron and iron peak, CNO, alpha, light, and neutron capture elements have already been obtained by means of high-resolution optical and near-infrared spectroscopy. The observed RSGs have half-solar metallicity, 10–30 Myr ages, bolometric luminosities in the 10
4
–10
5
L
⊙
range, and likely mass progenitors in the 9–14
M
⊙
range. We detected the optical Li
i
doublet in eight out of the 27 observed K- and M-type RSGs, finding relatively low A(Li) < 1.0 dex abundances, while for the remaining 19 RSGs upper limits of A(Li) < –0.2 dex have been set. Warmer and less luminous (i.e., likely less massive) as well as less mixed (i.e., with lower C/N and
12
C/
13
C depletion) RSGs with Li detection show somewhat higher Li abundances. In order to explain the Li detection in ∼30% of the observed RSGs, we speculate that some stochasticity should be at work, in a scenario where the Li was not completely destroyed in the convective atmospheres and/or a secondary production took place during the post-main-sequence evolution.
We investigate the metallicity of the broad line region (BLR) of a sample of 30 quasars in the redshift range 4 < z < 6.4, by using near-IR and optical spectra. We focus on the ratio of the broad ...lines (SiIV1397+OIV 1402)/CIV1549, which is a good metallicity tracer of the BLR. We find that the metallicity of the BLR is very high even in QSOs at z ~ 6. The inferred metallicity of the BLR gas is so high (several times solar) that metal ejection or mixing with lower metallicity gas in the host galaxy is required to match the metallicities observed in local massive galaxies. On average, the observed metallicity changes neither among quasars in the observed redshift range 4 < z <6.4, nor when compared with quasars at lower redshifts. We show that the apparent lack of metallicity evolution is a likely consequence of both the black hole-galaxy co-evolution and of selection effects. The data also suggest a lack of evolution in the carbon abundance, even among z > 6 quasars. The latter result is puzzling, since the minimum enrichment timescale of carbon is about 1 Gyr, i.e. longer than the age of the universe at z ~ 6.
Abstract
We present the first detailed observational picture of a possible ongoing massive cluster hierarchical assembly in the Galactic disk as revealed by the analysis of the stellar full phase ...space (3D positions and kinematics and spectro-photometric properties) of an extended area (6° diameter) surrounding the well-known
h
and
χ
Persei double stellar cluster in the Perseus Arm. Gaia-EDR3 shows that the area is populated by seven comoving clusters, three of which were previously unknown, and by an extended and quite massive (
M
∼ 10
5
M
⊙
) halo. All stars and clusters define a complex structure with evidence of possible mutual interactions in the form of intra-cluster overdensities and/or bridges. They share the same chemical abundances (half-solar metallicity) and age (
t
∼ 20 Myr) within a small confidence interval and the stellar density distribution of the surrounding diffuse stellar halo resembles that of a cluster-like stellar system. The combination of these pieces of evidence suggests that stars distributed within a few degrees from
h
and
χ
Persei are part of a common, substructured stellar complex that we named LISCA I. Comparison with results obtained through direct
N
-body simulations suggest that LISCA I may be at an intermediate stage of an ongoing cluster assembly that can eventually evolve in a relatively massive (a few times 10
5
M
⊙
) stellar system. We argue that such a cluster formation mechanism may be quite efficient in the Milky Way and disk-like galaxies and, as a consequence, it has a relevant impact on our understanding of cluster formation efficiency as a function of the environment and redshift.
Increased postprandial lipemia is a cardiovascular disease (CVD) risk factor. Carob fruit extract (CFE) contains condensed tannins, and their intake has been inversely related to CVD. The objective ...was to evaluate the in vitro pancreatic lipase activity in the presence of CFE and the in vivo effect of CFE on postprandial lipemia of healthy Wistar rats in acute and subchronic digestibility studies and to relate it with changes in fat digestion and absorption. CFE significantly reduced pancreatic lipase activity. A peak delay and a dose-dependent decrease in plasma triglyceride and cholesterol areas under the curve were observed, effects that increased after the subchronic treatment. The levels of nondigested, nonabsorbed triglycerides of the remaining intestinal lumen fat were significantly higher in the maximum dose of CFE administrated versus the control (P < 0.05). This study demonstrates for the first time the hypolipemic properties of CFE from the first administration, modifying postprandial lipemia by reducing the extents of fat digestion and absorption.
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