- ID:
- ivo://CDS.VizieR/J/ApJS/208/20
- Title:
- Nine-year WMAP point source catalogs
- Short Name:
- J/ApJS/208/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the final nine-year maps and basic results from the Wilkinson Microwave Anisotropy Probe (WMAP) mission. The full nine-year analysis of the time-ordered data provides updated characterizations and calibrations of the experiment. We also provide new nine-year full sky temperature maps that were processed to reduce the asymmetry of the effective beams. Temperature and polarization sky maps are examined to separate cosmic microwave background (CMB) anisotropy from foreground emission, and both types of signals are analyzed in detail. We provide new point source catalogs as well as new diffuse and point source foreground masks. An updated template-removal process is used for cosmological analysis; new foreground fits are performed, and new foreground-reduced CMB maps are presented.
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- ID:
- ivo://CDS.VizieR/J/A+A/617/A7
- Title:
- Nitrogen isotopic ratio in prestellar cores
- Short Name:
- J/A+A/617/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ^15^N fractionation has been observed to show large variations among astrophysical sources, depending both on the type of target and on the molecular tracer used. These variations cannot be reproduced by the current chemical models. Until now, the ^14^N/^15^N ratio in N_2_H^+^ has been accurately measured in only one prestellar source, L1544, where strong levels of fractionation, with depletion in ^15^N, are found (^14^N/^15^N~1000). In this paper we extend the sample to three more bona fide prestellar cores, in order to understand if the antifractionation in N_2_H^+^ is a common feature of this kind of sources. Methods. We observed N_2_H^+^ , N^15^NH^+^ and ^15^NNH^+^ in L183, L429 and L694-2 with the IRAM 30m telescope. We modeled the emission with a non-local radiative transfer code in order to obtain accurate estimates of the molecular column densities, including the one for the optically thick N_2_H^+^ . We used the most recent collisional rate coefficients available, and with these we also re-analysed the L1544 spectra previously published. The obtained isotopic ratios are in the range 630-770 and significantly differ with the value, predicted by the most recent chemical models, of ~440, close to the protosolar value. Our prestellar core sample shows high level of depletion of ^15^N in diazenylium, as previously found in L1544. A revision of the N chemical networks is needed in order to explain these results.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A109
- Title:
- ^14^N/^15^N isotopic ratio in L1544
- Short Name:
- J/A+A/555/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Samples of pristine solar system material found in meteorites and interplanetary dust particles are highly enriched in ^15^N. Conspicuous nitrogen isotopic anomalies have also been measured in comets, and the ^14^N/^15^N abundance ratio of the Earth is itself higher than the recognised presolar value by almost a factor of two. Ion/molecules, low-temperature chemical reactions in the proto-solar nebula have been repeatedly indicated as being responsible for these ^15^N-enhancements. We have searched for ^15^N variants of the N2H^+^ ion in L1544, a prototypical starless cloud core that is one of the best candidate sources for detection owing to its low central core temperature and high CO depletion. The goal is to evaluate accurate and reliable ^14^N/^15^N ratio values for this species in the interstellar gas. A deep integration of the ^15^NNH^+^(1-0) line at 90.4GHz was obtained with the IRAM 30m telescope. Non-LTE radiative transfer modelling was performed on the J=1-0 emissions of the parent and ^15^N-containing dyazenilium ions, using a Bonnor-Ebert sphere as a model for the source. A high-quality fit of the N2H^+^(1-0) hyperfine spectrum has allowed us to derive a revised value of the N2H+ column density in L1544. Analysis of the observed N^15^NH^+^ and ^15^NNH^+^ spectra yielded an abundance ratio N(N^15^NH^+^)/N(^15^NNH^+^)=1.1+/-0.3. The obtained ^14^N/^15^N isotopic ratio is ~1000+/-200, suggestive of a sizeable ^15^N depletion in this molecular ion. Such a result is not consistent with the prediction of the current nitrogen chemical models. Since chemical models predict high ^15^N fractionation of N_2_H^+^, we suggest that ^15^N^14^N, or ^15^N in some other molecular form, is preferentially depleted onto dust grains.
1144. 14N/15N ratio in YSOs
- ID:
- ivo://CDS.VizieR/J/A+A/644/A29
- Title:
- 14N/15N ratio in YSOs
- Short Name:
- J/A+A/644/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nitrogen isotopic ratio is considered an important diagnostic tool of the star formation process, and N_2_H^+^ is particularly important because it is directly linked to molecular nitrogen N_2_. However, theoretical models still lack to provide an exhaustive explanation for the observed^14^N/^15^N values. Recent theoretical works suggest that the^14^N/^15^N behaviour is dominated by two competing reactions that destroy N_2_H^+^: dissociative recombination and reaction with CO. When CO is depleted from the gas phase, if N_2_H^+^ recombination rate is lower with respect to the N^15^NH^+^ one, the rarer isotopologue is destroyed faster. In prestellar cores, due to a combination of low temperatures and high densities, most CO is frozen in ices onto the dust grains, leading to high levels of depletion. On the contrary, in protostellar cores, where temperature are higher, CO ices evaporate back to the gas phase. This implies that the N_2_H^+^ isotopic ratio in protostellar cores should be lower than the one in prestellar cores, and consistent with the elemental value of ~440. We aim to test this hypothesis, producing the first sample of N_2_H^+^ /N^15^NH^+^ measurements in low mass protostars. We observe the N_2_H^+^ and N^15^NH^+^ lowest rotational transition towards six young stellar objects in Perseus and Taurusmolecular clouds. We model the spectra with a custom python code using a constant T_ex_ approach to fit the observations. We discuss in appendix the validity of this hypothesis. The derived column densities are used to compute the nitrogen isotopic ratios. Our analysis yields an average of^14^N/^15^N|_pro_=420+/-15 in the protostellar sample. This is consistent with the protosolar value of 440, and significantly lower than the average value previously obtained in a sample of prestellar objects. Our results are in agreement with the hypothesis that, when CO is depleted from the gas-phase, dissociative recombinations with free electrons destroy N^15^NH^+^ faster than N_2_H^+^ , leading to high isotopic ratios in prestellar cores, where carbon monoxide is frozen onto dust grains.
- ID:
- ivo://jvo/nobeyama
- Title:
- Nobeyama Radio Telescope FITS Archive
- Short Name:
- NRO FITS ARCHIVE
- Date:
- 14 Nov 2019 03:48:50
- Publisher:
- JVO
- Description:
- FITS data archive for Nobeyama 45m radio telescope.
- ID:
- ivo://CDS.VizieR/J/ApJS/117/319
- Title:
- Northern RASS X-ray sources catalog
- Short Name:
- J/ApJS/117/319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of optical identifications of a representative sample of northern ({delta})>-9{deg}) ROSAT All-Sky Survey (RASS) sources. A full identification has been carried out for a count-rate- and area-limited complete RASS subsample comprising 674 sources. All sources are within six study areas outside the galactic plane (|b|>19.6{deg}), one area being near the north Galactic pole and one near the north ecliptic pole.
- ID:
- ivo://CDS.VizieR/J/AJ/77/797
- Title:
- NRAO 5GHz Strong Source Survey
- Short Name:
- J/AJ/77/797
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 140-ft telescope at the National Radio Astronomy Observatory has been used to extend the 5-GHz strong source (S) survey over an area of 1.14 steradian. Some 240 sources have been detected in this region, of which 135 are above the completeness limit of 0.6f.u. The distribution of spectral indices for sources above the completeness limit is much broader than for samples selected from long-wavelength surveys, owing to an increase in the fraction of compact sources with flat spectra. For about half of the sources selected at 6 cm, the spectral index {alpha}>-0.5. Analysis of the dependence of the spectral index on the flux density shows that, as expected from the 408-MHz number counts and spectral index distribution, at 5 GHz there are fewer flat spectra among the weak sources than among the stronger ones. The spectral index distributions for the identified galaxies and quasars show the familiar forms: the galaxies have a strong concentration near {alpha}=-0.8 with a small tail extending toward flat spectra. The quasars show a much broader distribution of indices, but the fraction (80%) of quasars having flat spectra ({alpha}>-0.5) is much greater than that found in the low-frequency surveys. The number-flux density relation for various groups of sources selected from the 5-GHz survey show that the anomalously steep slope is confined to (a) unidentified sources, (b) sources with steep spectra ({alpha}<-0.5), and (c) sources located in the north galactic hemisphere. Sources identified with radio galaxies or quasars, or which have flat spectra, or which are in the south galactic hemisphere all show a number-flux density slope near -1.5.
- ID:
- ivo://CDS.VizieR/J/other/A+C/25.176
- Title:
- NVSS and FIRST variable sources
- Short Name:
- J/other/A+C/25.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the present study we have cross-correlated NVSS and FIRST radio catalogues having radio flux measurements at the same 1.4GHz frequency. This way we benefit from repeated observations from both catalogues, as they give more accurate positions and fluxes and more important, reveal large differences between the two measured fluxes, thus allowing to establish radio variability. As a result 79382 radio variables have been revealed, including 6301 with flux differences at 1.4GHz larger than 15mJy, 1917 with flux differences 45mJy and 260 with flux differences 200mJy. By using a special technique (Mickaelian & Sinamyan 2010 (J/MNRAS/407/681) Mickaelian+ 2011 (J/MNRAS/415/1061)), 2425 optically variable objects out of 6301 radio sources have been revealed. 2425 radio sources with both high radio and optical variability into four categories have been divided. 1206 (19%) out of 6301 radio sources have activity types from available catalogues and 619 (25.5%) out of 2425 radio sources with at the same time radio and optical variability have activity types from available catalogues. In addition, 279 radio sources out of 2425 have high variability in optical range. We have established their activity types when available. The IR fluxes and colours for the 6301 variable radio sources have been studied. Colour-colour diagrams show that most of the "unknown" sources are galaxies. The activity types for 110 (42%) out of 260 extremely high variable radio sources also have been retrieved.
- ID:
- ivo://CDS.VizieR/J/AZh/71/352
- Title:
- Objects of 1988 Zenith Sky Survey
- Short Name:
- J/AZh/71/352
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of optical identification of radio sources Zenith Sky Survey with the Palomar Sky Survey prints are presented. The sky survey was conducted with a RATAN-600 radio telescope at 8.0cm in a ring-aperture operation mode. All the objects belong to the radio source population with flux densities in a range from 5 to 50mJy. The mean value of the spectral index distribution for the sources identified with other catalogs was found to be equal to -0.9 at 8.0cm.
- ID:
- ivo://CDS.VizieR/J/ApJ/810/85
- Title:
- Observation of first Fermi-LAT sources at Parkes
- Short Name:
- J/ApJ/810/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a search with the Parkes radio telescope of 56 unidentified Fermi-Large Area Telescope (LAT) gamma-ray sources, we have detected 11 millisecond pulsars (MSPs), 10 of them discoveries, of which five were reported by Kerr et al (2012ApJ...748L...2K). We did not detect radio pulsations from six other pulsars now known in these sources. We describe the completed survey, which included multiple observations of many targets conducted to minimize the impact of interstellar scintillation, acceleration effects in binary systems, and eclipses. We consider that 23 of the 39 remaining sources may still be viable pulsar candidates. We present timing solutions and polarimetry for five of the MSPs and gamma-ray pulsations for PSR J1903-7051 (pulsations for five others were reported in the second Fermi-LAT catalog of gamma-ray pulsars). Two of the new MSPs are isolated and five are in >1 day circular orbits with 0.2-0.3 M_{sun}_ presumed white dwarf companions. PSR J0955-6150, in a 24 day orbit with a 0.2-0.3 M_{sun}_ companion but eccentricity of 0.11, belongs to a recently identified class of eccentric MSPs. PSR J1036-8317 is in an 8 hr binary with a>0.14 M_{sun}_ companion that is probably a white dwarf. PSR J1946-5403 is in a 3 hr orbit with a>0.02 M_{sun}_ companion with no evidence of radio eclipses.