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Looze I.D.,Ghent University | Baes M.,Ghent University | Boselli A.,French National Center for Scientific Research | Cortese L.,European Southern Observatory | And 19 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We use dust scaling relations to investigate the hypothesis that Virgo cluster transition-type dwarfs are infalling star-forming field galaxies, which is argued based on their optical features (e.g. discs, spiral arms and bars) and kinematic properties similar to late-type galaxies. After their infall, environmental effects gradually transform them into early-type galaxies through the removal of their interstellar medium and quenching of all star formation activity. In this paper, we aim to verify whether this hypothesis holds using far-infrared diagnostics based on Herschel observations of the Virgo cluster taken as part of the Herschel Virgo Cluster Survey. We select transition-type objects in the nearest cluster, Virgo, based on spectral diagnostics indicative for their residual or ongoing star formation. We detect dust (Md ~ 105-6 M⊙) in 36 per cent of the transition-type dwarfs located on the high end of the stellar mass distribution. This suggests that the dust reservoirs present in non-detections fall just below the Herschel detection limit (≲1.1 × 105M⊙). Dust scaling relations support the hypothesis of a transformation between infalling late-type galaxies to quiescent low-mass spheroids governed by environmental effects, with dust-tostellar mass fractions for transition-type dwarfs in between values characteristic for late-type objects and the lower dust fractions observed in early-type galaxies. Several transition-type dwarfs demonstrate blue central cores, hinting at the radially outside-in removal of gas and quenching of star formation activity. The fact that dust is also confined to the inner regions suggests that metals are stripped in the outer regions along with the gas. In the scenario of most dust being stripped from the galaxy along with the gas, we argue that the ejected metals by transition-type dwarfs significantly contribute to the enrichment of the intracluster medium over the lifetime of the Virgo cluster. The accretion of gas through tidal interactions and reignition of star formation in the centres of transition-type dwarfs could provide an alternative explanation for the observed dust scaling relations and blue central cores. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Rothman L.S.,Harvard - Smithsonian Center for Astrophysics | Gordon I.E.,Harvard - Smithsonian Center for Astrophysics | Babikov Y.,Zuev Institute of Atmospheric Optics | Barbe A.,CNRS Molecular and Atmospheric Spectrometry Group | And 47 more authors.
Journal of Quantitative Spectroscopy and Radiative Transfer | Year: 2013

This paper describes the status of the 2012 edition of the HITRAN molecular spectroscopic compilation. The new edition replaces the previous HITRAN edition of 2008 and its updates during the intervening years. The HITRAN molecular absorption compilation is comprised of six major components structured into folders that are freely accessible on the internet. These folders consist of the traditional line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, infrared absorption cross-sections for molecules not yet amenable to representation in a line-by-line form, ultraviolet spectroscopic parameters, aerosol indices of refraction, collision-induced absorption data, and general tables such as partition sums that apply globally to the data. The new HITRAN is greatly extended in terms of accuracy, spectral coverage, additional absorption phenomena, and validity. Molecules and isotopologues have been added that address the issues of atmospheres beyond the Earth. Also discussed is a new initiative that casts HITRAN into a relational database format that offers many advantages over the long-standing sequential text-based structure that has existed since the initial release of HITRAN in the early 1970s. © 2013 Elsevier Ltd.


Dore L.,University of Bologna | Bizzocchi L.,CAAUL | Degli Esposti C.,University of Bologna | Gauss J.,University Mainz
Journal of Molecular Spectroscopy | Year: 2010

The hyperfine structure in the ground-state rotational spectrum of methanimine was studied in the frequency range of 64-172 GHz by means of the Lamb-dip technique. This allowed to resolve, in some hyperfine components due to the 14N nucleus, doublets separated by only some tenth of kHz. We explain the splittings as due to magnetic interactions of the three protons with their molecular environment. The analysis of the experimental spectrum has been guided by quantum-chemical calculations of the hyperfine parameters. © 2010 Elsevier Inc. All rights reserved.


Di Serego Alighieri S.,National institute for astrophysics | Bianchi S.,National institute for astrophysics | Pappalardo C.,National institute for astrophysics | Zibetti S.,National institute for astrophysics | And 15 more authors.
Astronomy and Astrophysics | Year: 2013

Aims. We study the dust content of a large optical input sample of 910 early-type galaxies (ETG) in the Virgo cluster, also extending to the dwarf ETG, and examine the results in relation to those on the other cold ISM components. Methods. We have searched for far-infrared emission in all galaxies in the input sample using the 250 μm image of the Herschel Virgo Cluster Survey (HeViCS). This image covers a large fraction of the cluster with an area of ~55 square degrees. For the detected ETG we measured fluxes in five bands from 100 to 500 μm, and estimated the dust mass and temperature with modified black-body fits. Results. Dust is detected above the completeness limit of 25.4 mJy at 250 μm in 46 ETG, 43 of which are in the optically complete part of the input sample. In addition, dust is present at fainter levels in another six ETG. We detect dust in the four ETG with synchrotron emission, including M 87. Dust appears to be much more concentrated than stars and more luminous ETG have higher dust temperatures. Considering only the optically complete input sample and correcting for the contamination by background galaxies, dust detection rates down to the 25.4 mJy limit are 17% for ellipticals, about 40% for lenticulars (S0 + S0a), and around 3% for dwarf ETG. Dust mass does not correlate clearly with stellar mass and is often much greater than expected for a passive galaxy in a closed-box model. The dust-to-stars mass ratio anticorrelates with galaxy luminosity, and for some dwarf ETG reaches values as high as for dusty late-type galaxies. In the Virgo cluster slow rotators appear more likely to contain dust than fast ones. Comparing the dust results with those on Hi there are only eight ETG detected both in dust and in Hi in the HeViCS area; 39 have dust but only an upper limit on Hi, and eight have Hi but only an upper limit on dust. The locations of these galaxies in the cluster are different, with the dusty ETG concentrated in the densest regions, while the Hi rich ETG are at the periphery. © 2013 ESO.


Withers P.,Boston University | Fallows K.,Boston University | Girazian Z.,Boston University | Matta M.,Boston University | And 9 more authors.
Geophysical Research Letters | Year: 2012

[1] By examining electron density profiles from the Mars Express Radio Science Experiment MaRS, we show that the vertical structure of the dayside ionosphere of Mars is more variable and more complex than previously thought. The top of the ionosphere can be below 250 km (25% occurrence rate) or above 650 km (1%); the topside ionosphere can be well-described by a single scale height (10%) or two/three regions with distinct scale heights (25% or 10%), where those scale heights range between tens and hundreds of kilometers; the main layer of the ionosphere can have a sharply pointed (5%), flat-topped (6%), or wavy (8%) shape, in contrast to its usual Chapman-like shape; a broad increase in electron density is detected at 160-180 km (10%); a narrow increase in electron density is sometimes found in strongly-magnetized regions; and an additional layer is present between the M1 and M2 layers (3%). © 2012. American Geophysical Union. All Rights Reserved.


Giuliano B.M.,University of Coimbra | Bizzocchi L.,CAAUL | Sanchez R.,University of Valladolid | Villanueva P.,University of Valladolid | And 3 more authors.
Journal of Chemical Physics | Year: 2011

The pure rotational spectra of 18 and 21 isotopic species of GeSe and GeTe have been measured in the frequency range 5-24GHz using a Fabry-Pérot- type resonator pulsed-jet Fourier-transform microwave spectrometer. Gaseous samples of both chalcogenides were prepared by a combined dc discharge/laser ablation technique and stabilized in supersonic jets of Ne. Global multi-isotopologue analyses of the derived rotational data, together with literature high-resolution infrared data, produced very precise Dunham parameters, as well as rotational constant Born-Oppenheimer breakdown (BOB) coefficients (δ01) for Ge, Se, and Te. A direct fit of the same datasets to an appropriate radial Hamiltonian yielded analytic potential-energy functions and BOB radial functions for the X1Σ+ electronic state of both GeSe and GeTe. Additionally, the electric quadrupole and magnetic hyperfine interactions produced by the nuclei 73Ge, 77Se, and 125Te were observed, yielding much improved quadrupole coupling constants and first determinations of the spin-rotation parameters. © 2011 American Institute of Physics.


Dore L.,University of Bologna | Bizzocchi L.,CAAUL | Esposti C.D.,University of Bologna | Tamassia F.,University of Bologna
Molecular Physics | Year: 2011

The deuterated radical ND was produced in a DC discharge cell cooled at liquid nitrogen temperature. The discharge proved to be vibrationally hot, therefore the transient species could be detected in its vibrational excited states up to v=6. By scanning in the 431-531GHz frequency region, several fine-structure components of the N=1 → 0 transition in vibrational excited states were observed, each of them showing a complex hyperfine structure. A global analysis, including the measured frequencies and previous submillimetre-wave and infrared data, allowed an accurate determination of the equilibrium spectroscopic parameters of the ND radical including fine and hyperfine constants. A very precise determination of the equilibrium bond length r e was obtained. This value is not consistent with the value reported in the literature from NH data. This incongruity was discussed in terms of the breakdown of the Born-Oppenheimer approximation. In view of the recent detection of ND in a solar-mass protostar [A. Bacmann et al., Astron. Astrophys. 521, L42 (2010)], an extended spectroscopic characterization of this deuterated isotopologue of the NH species may prove useful, considering the large deuterium enhancement observed in molecular clouds. Copyright © 2011 Taylor and Francis Group, LLC.


Bizzocchi L.,CAAUL | Tamassia F.,University of Bologna | Esposti C.D.,University of Bologna | Fusina L.,University of Bologna | And 2 more authors.
Molecular Physics | Year: 2011

The infrared spectrum of diacetylene has been recorded at high resolution between 500 and 1000cm -1 by Fourier transform spectroscopy. More than 1200 transitions were assigned to five bands: the v 8 fundamental, the v 7+v 9 combination, and the v 3-v 9 difference bands as well as the most intense v 8+v 9-v 9 and v 7+2v 9-v 9 hot bands. The data were analysed together with the previously recorded millimetre-wave lines for the v 8-v 6 and v 8+v 9-(v 6+v 8) difference bands. Rotational and vibrational l-type resonances, together with the cubic anharmonic interactions which couple the v 3=1 stretching state with the v 8=v 9=1 combination and v 7=2 overtone states, have been considered in the least-squares fits to the observed wavenumbers in order to derive reliable spectroscopic parameters. The spectral analyses deliver very precise B 0 and D 0 parameters and experimental values of the anharmonicity constants for the bending-bending combination states of diacetylene below 1000cm -1. Copyright © 2011 Taylor and Francis Group, LLC.


Bizzocchi L.,CAAUL | Esposti C.D.,University of Bologna | Dore L.,University of Bologna
Molecular Physics | Year: 2010

Rovibrational bands between closely lying bending vibrational states of normal diacetylene and its bideuterated variant have been recorded in the submillimetre-wave region using a source-modulation spectrometer. The two isotopologues were produced by pyrolysis (1200°C) of benzene or benzene-d6 vapour in a flow reactor. Measurements of the v8 - v6 band and of its 9-associated hot band have been extended up to 615 and 420 GHz, respectively. Rotational and vibrational l-type resonance were taken into account in the analysis of the v8 + v9 - v6 - v9 band; in addition the cubic anharmonic resonance existing between the v8 = v9 = 1 state and the v3 = 1 stretching state has been considered explicitly in the least-squares fits to the observed frequencies. Very accurate values of the band origins and of numerous spectroscopic constants have been determined for both isotopologues. © 2010 Taylor & Francis.


Ultra Steep Spectrum (USS) radio sources have been successfully used to select powerful radio sources at high redshifts (z > 2). Typically restricted to large-sky surveys and relatively bright radio flux densities, it has gradually become possible to extend the USS search to sub-mJy levels, thanks to the recent appearance of sensitive low-frequency radio facilities. Here we present a first detailed analysis of the nature of the faintest USS sources. By using GMRT and VLA radio observations of the Lockman Hole (LH) at 610MHz and 1.4GHz, a sample of 58 micro-Jansky USS sources is assembled. Deep infrared data at 3.6 and 4.5μm from the Spitzer Extragalactic Representative Volume Survey (SERVS) is used to reliably identify counterparts for 48 (83%) of these sources, showing an average magnitude of [3.6]=19.7 mag(AB). Spectroscopic redshifts for 14 USS sources, together with photometric redshift estimates, improved by the use of the deep SERVS data, for a further 19 objects, show redshifts ranging from z =0.1 to z=2.8, peaking at z∼0.6 and tailing off at high redshifts. © Springer-Verlag Berlin Heidelberg 2012.

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