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[en] Recent determinations of baryonic density using the angular power spectrum of the Cosmic Microwave Background are very close to the classical estimate from Big Bang Nucleosynthesis. This reinforces the case for dark baryons in the Universe and for a large component of exotic cold dark matter. Present-day baryons can be hidden in substellar objects, stellar remnants, cold gas clouds, hot diffuse ionized gas in various astrophysical environments. Direct detection searches and microlensing experiments provide estimates of the Galactic mass budget in massive compact objects concluding that the bulk of the dark matter in the halo of the Galaxy cannot be associated to MACHOs. Baryons in high redshift Lyman-α systems can account for the cosmic baryonic density. However, the dominant form of present-day baryons and, in particular, the nature of the halo dark matter remains a mystery
[en] We report an ultra-bright lensed submillimeter galaxy (SMG) at z = 2:0439, WISE J132934.18+224327.3, identified as a result of a full-sky cross-correlation of the AllWISE and Planck compact source catalogs aimed to search for bright analogs of the submillimeter galaxy SMMJ2135, the Cosmic Eyelash. Inspection of archival SCUBA-2 observations of the candidates revealed a source with fluxes (S850m= 130 mJy) consistent with the Planck measurements. The centroid of the SCUBA-2 source coincides within 1 arcsec with the position of the AllWISE mid-IR source, and, remarkably, with an arc shaped lensed galaxy in HST images at visible wavelengths. Low-resolution rest-frame UV-optical spectroscopy of this lensed galaxy obtained with 10.4 m GTC reveals the typical absorption lines of a starburst galaxy. Gemini-N near-IR spectroscopy provided a clear detection of H emission. The lensed source appears to be gravitationally magnified by a massive foreground galaxy cluster lens at z = 0:44, modeling with Lenstool indicates a lensing amplification factor of 112. We determine an intrinsic restframe 8-1000-m luminosity, LIR, of (1:30:1)1013 L, and a likely star-formation rate (SFR) of 500. The SED shows a remarkable similarity with the Cosmic Eyelash from optical-mid/IR to sub-millimeter/radio, albeit at higher fluxes.
[en] The oxygen abundance has been determined by analysis of the O I infrared triplet in 30 unevolved field stars of metallicities in the range Fe/H abundance ratio between -0.2 and -3.5. The data show that the O/Fe abundance ratio increases monotonically as metallicity decreases from solar, reaching values in the range 1.0-1.2 at an Fe/H abundance ratio of about -2. The results, when compared with those already published for metal-deficient red giants, suggest that oxygen could have been depleted in the latter. A discussion of the O/Fe abundance ratios in connection with the chemical evolution of the Galaxy is also presented. 83 refs
[en] Results are reported from a search for fluctuations in the cosmic microwave background radiation (CMBR) on angular scales of 2 deg or greater at 10.4 GHz. Data obtained over a 2-yr period at Teide Observatory at Tenerife are presented in a map and briefly characterized. At high Galactic latitudes, signals with rms Delta-T/T of about 0.000037 are detected in beams of 5-8 deg when the system sensitivity is of order 0.00001. Assuming the signals are from intrinsic CMBR fluctuations (z = about 1000), these observations appear to rule out ordinary adiabatic cosmological scenarios comprising baryonic matter at density less than the closure density of the universe
[en] The iron abundance of seven stars near the main-sequence (MS) turnoff and a giant in M67 are spectroscopically derived, and the results are discussed. The resulting mean iron abundance of the turnoff stars is (Fe/H) = 0.04 + or - 0.04. Taken together with previous determinations for younger clusters, this shows that there has been relatively little change of the iron abundance in the solar neighborhood during the last 5 Gyr. Lithium was detected in one unevolved star and marginally in the giant, while in the other MS stars only upper limits were found. The considerable differences in Li abundances for stars with similar surface temperature imply that there is at least one parameter affecting Li depletion apart from stellar mass and metallicity. Nonsimultaneous star formation in the cluster cloud explain the scatter in lithium abundances. 50 references
[en] We have used the CCD camera and Intermediate Dispersion Spectrograph of the 2.5m Isaac Newton Telescope to obtain high quality spectra of the 6708 A 7Li resonance doublet in 22 dwarfs with metallicities ≤ -0.7. We find a mean constant value of Log N(Li)= 2.07 (±0.1) for highly metal deficient dwarfs ([Fe/H] ≤ -1.5) with atmospheric temperatures Teff > 5500 K, and a larger spread with values of Log N(Li) up to 2.4 for the warmer dwarfs with metallicities between -0.7 and -1.2. Our results agree with previous findings showing a highly uniform Li abundance near the inception of the galaxy. Li depletion appears to set in at higher temperatures for the moderately metal deficient stars than for the extremely metal deficient, consistent with metallicity-dependent depletion rates (low metals, low depletion)
[en] A representative set of profiles is presented for the Ca II H resonace line in Stokes V and I, for the quiet sun, plages, sunspot umbrae, and a flare, as well as one example of the Ca II K line in a sunspot penumbra. The degree of polarization is highest in the spots and zero in the quiet sun, within error limits. The V profile asymmetries are, however, highest in the flare. The spectra of the Ca II K line are used to obtain a linear relation between V(lambda) and -dI/d(lambda) and a value for B(parallel) of 820 + or - 40 G using the weak-field approximation. 25 refs
[en] The close agreement of the spectrum of the CMB with the blackbody shape confirms that it is a relic of the big bang. Moreover, the lack of detectable deviations from the blackbody shape shows that no large energy inputs have occurred at early epochs. All scenarios of galaxy formation require that there should be angular perturbations in the CMB at the epoch of recombination (z = 1000) that result from the mass fluctuations at the epoch and that eventually grow to become the galaxies and other large-scale structures (clusters, voids, etc.) of the present epoch. All such scenarios predict intensity fluctuations having at least ΔT/T = 3 x 10-6 over most angular scales. Some adiabatic scenarios envisage fluctuations as high as ΔT/T = '0-4. The sensitivity of the experiments discussed in this paper is ΔT/T ≅ 10-5
[en] We present evidence for anomalous microwave emission (AME) in the Pleiades reflection nebula, using data from the seven-year release of the Wilkinson Microwave Anisotropy Probe and from the COSMOSOMAS (Cosmological Structures on Medium Angular Scales) experiment. The flux integrated in a 1° radius around R.A. = 56.024, decl. = 23.078 (J2000) is 2.15 ± 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data show no significant emission, but allow one to set upper limits of 0.94 and 1.58 Jy (99.7% confidence level), respectively, at 10.9 and 14.7 GHz, which are crucial to pin down the AME spectrum at these frequencies, and to discard any other emission mechanisms which could have an important contribution to the signal detected at 22.8 GHz. We estimate the expected level of free-free emission from an extinction-corrected Hα template, while the thermal dust emission is characterized from infrared DIRBE data and extrapolated to microwave frequencies. When we deduct the contribution from these two components at 22.8 GHz, the residual flux, associated with AME, is 2.12 ± 0.12 Jy (17.7σ). The spectral energy distribution from 10 to 60 GHz can be accurately fitted with a model of electric dipole emission from small spinning dust grains distributed in two separated phases of molecular and atomic gas, respectively. The dust emissivity, calculated by correlating the 22.8 GHz data with 100 μm data, is found to be 4.36 ± 0.17 μK (MJy sr–1)–1, a value considerably lower than in typical AME clouds, which present emissivities of ∼20 μK (MJy sr–1)–1, although higher than the 0.2 μK (MJy sr–1)–1 of the translucent cloud LDN 1780, where AME has recently been claimed. The physical properties of the Pleiades nebula, in particular its low extinction AV ∼ 0.4, indicate that this is indeed a much less opaque object than those where AME has usually been studied. This fact, together with the broad knowledge of the stellar content of this region, provides an excellent testbed for AME characterization in physical conditions different from those generally explored up to now.
[en] High resolution high signal to noise spectral profiles of the λ 8498 and λ 8542 A lines of the Ca II infrared triplet (IRT) have been obtained for a sample of late type dwarfs, with a wide range of levels of chromospheric activity, in the spectral range F9 to K4/5. We present these profiles, and the difference profiles for selected active and quiescent objects of corresponding spectral type. After absolute calibration in flux we take advantage of the high resolution and S/N ratios of the spectra to define several IRT indices of chromospheric activity, for a set of bandwidths between 0.2 A and 1 A about the line centres. Excellent correlations for active stars between the IRT and the Ca H indices and between the respective line widths are shown, which pertain despite the different depths of formation of the lines in the stellar chromospheres