- ID:
- ivo://CDS.VizieR/J/ApJS/149/29
- Title:
- ROSAT North Ecliptic Pole Survey
- Short Name:
- J/ApJS/149/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The X-ray data around the North Ecliptic Pole (NEP) of the ROSAT All Sky Survey have been used to construct a contiguous area survey consisting of a sample of 445 individual X-ray sources above a flux of ~2x10^-14^erg/cm^2^/s in the 0.5-2.0keV energy band. The NEP survey is centered at RA=18:00 (2000) DE=+66:33 and covers a region of 80.7deg^2^ at a moderate Galactic latitude of b=29.8{deg}. Hence, the NEP survey is as deep and covers a comparable solid angle to the ROSAT serendipitous surveys but is also contiguous. We have identified 99.6% of the sources and determined redshifts for the extragalactic objects. In this paper we present the optical identifications of the NEP catalog of X-ray sources including basic X-ray data and properties of the sources. We also describe with some detail the optical identification procedure. The classification of the optical counterparts to the NEP sources is very similar to that of previous surveys, in particular the Einstein Extended Medium Sensitivity Survey (EMSS). The main constituents of the catalog are active galactic nuclei (AGNs) (~49%), either type 1 or type 2 according to the broadness of their permitted emission lines. Stellar counterparts are the second most common identification class (~34%). Clusters and groups of galaxies comprise 14%, and BL Lacertae objects 2%. One non-AGN galaxy and one planetary nebula have also been found. The NEP catalog of X-ray sources is a homogeneous sample of astronomical objects featuring complete optical identification.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/461/977
- Title:
- Rosat North Ecliptic survey stellar population
- Short Name:
- J/A+A/461/977
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- X-ray surveys are a very efficient mean of detecting young stars and therefore allow us to study the young stellar population in the solar neighborhood and the local star formation history in the last billion of years. We want to study the young stellar population in the solar neighborhood, to constrain its spatial density and scale height as well as the recent local star formation history. We analyze the stellar content of the ROSAT North Ecliptic Pole survey, and compare the observations with the predictions derived from stellar galactic model. Since the ROSAT NEP survey is sensitive at intermediate fluxes is able to sample both the youngest stars and the intermediate age stars (younger than 10^9^years), linking the shallow and deep flux surveys already published in the literature. We confirm the existence of an excess of yellow stars in our neighborhood previously seen in shallow survey, which is likely due to a young star population not accounted for in the model. However the excellent agreement between observations and predictions of dM stars casts some doubt on the real nature of this active population.
- ID:
- ivo://CDS.VizieR/J/ApJ/554/202
- Title:
- ROSAT X-ray observations of M81
- Short Name:
- J/ApJ/554/202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from the analysis of deep ROSAT HRI and PSPC observations of the spiral galaxy M81. The inferred total (0.5-2keV band) luminosity of M81 is ~3x10^40^ergs/s, excluding the contribution from identified interlopers found within the D_25_ ellipse. The nucleus of the galaxy alone accounts for about 65% of this luminosity. The rest is due to 26 other X-ray sources (contributing ~10%) and to apparently diffuse emission, which is seen across much of the galactic disk and is particularly bright in the bulge region around the nucleus. Spectral analysis further gives evidence for a soft component, which can be characterized by a two-temperature optically thin plasma with temperature at ~0.15 and 0.60keV and an absorption of the galactic foreground only. These components, accounting for ~13% of the X-ray emission from the region, apparently arise in a combination of hot gas and faint discrete sources. We find interesting spatial coincidences of luminous (10^37^-10^40^ergs/s) and variable X-ray sources with shock-heated optical nebulae. Three of them are previously classified as supernova remnant candidates. The other one is far off the main body of M81 but is apparently associated with a dense H I concentration produced most likely by the tidal interactions of the galaxy with its companions. These associations suggest that such optical nebulae may be powered by outflows from luminous X-ray binaries, which are comparable to, or more luminous than, Galactic "microquasars."
1484. Rosette Nebula globules
- ID:
- ivo://CDS.VizieR/J/A+A/605/A82
- Title:
- Rosette Nebula globules
- Short Name:
- J/A+A/605/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Rosette nebula is an HII region ionized mainly by the stellar cluster NGC 2244. Elephant trunks, globules, and globulettes are seen at the interface where the HII region and the surrounding molecular shell meet. We have observed a field in the northwestern part of the Rosette nebula where we study the small globules protruding from the shell. Our aim is to measure their properties and study their star-formation history in continuation of our earlier study of the features of the region. We imaged the region in broadband near-infrared (NIR) JsHKs filters and narrowband H_2_ 1-0 S(1), P{beta}, and continuum filters using the SOFI camera at the ESO/NTT. The imaging was used to study the stellar population and surface brightness, create visual extinction maps, and locate star formation. Mid-infrared (MIR) Spitzer IRAC and WISE and optical NOT images were used to further study the star formation and the structure of the globules. The NIR and MIR observations indicate an outflow, which is confirmed with CO observations made with APEX.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A123
- Title:
- Rotational spectroscopy of CH_2_OH
- Short Name:
- J/A+A/644/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The hydroxymethyl radical (CH_2_OH) is one of the two structural isomers, together with the methoxy radical (CH_3_O), that can be produced by abstraction of a hydrogen atom from methanol (CH_3_OH). In the interstellar medium (ISM), both CH_2_OH and CH_3_O are suspected to be intermediate species in many chemical reactions, including those of formation and destruction of methanol. The determination of the CH_3_O/CH_2_OH ratio in the ISM would bring important information concerning the formation processes of these species in the gas and solid phases. Interestingly, only CH_3_O has been detected in the ISM so far, despite the recent first laboratory measurement of the CH_2_OH rotation-tunneling spectrum. This lack of detection is possibly due to the non-observation in the laboratory of the most intense rotational-tunneling transitions at low temperature. To support further searches for the hydroxymethyl radical in space, we have performed a thorough spectroscopic study of its rotation-tunneling spectrum, with particular focus on transitions involving the lowest quantum numbers of the species. We have recorded the rotation-tunneling spectrum of CH_2_OH at room temperature in the millimeter-wave domain using a frequency multiplication chain spectrometer associated to a fluorine-induced H-abstraction method. The radical was produced from methanol precursor. About 180 transitions were observed including those involving the lowest N and Ka quantum numbers, predicted intense under cold astrophysical conditions. These transitions were fitted together with available millimeter-wave lines from the literature. The systematic observation of all components of the rotational transitions yields a large improvement of the spectroscopic parameters which now allow confident searches of the hydroxymethyl radical in cold to warm environments of the ISM.
- ID:
- ivo://CDS.VizieR/J/A+A/500/1109
- Title:
- Rotational spectrum of HCOO^13^CH_3_
- Short Name:
- J/A+A/500/1109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Laboratory measurements and analysis of the microwave and millimeter-wave spectra of potential interstellar molecules are a prerequisite for their subsequent identification by radioastronomical techniques. The spectral analysis provides spectroscopic parameters that are used in the assignment procedure of the laboratory spectra, and that also predict the frequencies of transitions not measured in the laboratory with a high degree of precision. An experimental laboratory study and its theoretical analysis is presented for ^13^C_2_-methyl formate (HCOO^13^CH_3_) allowing a search for this isotopologue in the Orion molecular cloud. The ^13^C_1_-methyl formate (H^13^COOCH_3_) molecule was also searched for in this interstellar cloud, using previously published spectroscopic data.
- ID:
- ivo://CDS.VizieR/J/ApJ/702/1230
- Title:
- Rotation measure image of the sky
- Short Name:
- J/ApJ/702/1230
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have re-analyzed the NRAO VLA Sky Survey (NVSS) data to derive rotation measures (RMs) toward 37543 polarized radio sources. The resulting catalog of RM values covers the sky area north of declination -40{deg} with an average density of more than one RM per square degree. We have identified five regions of the sky where the foreground median RM is consistently less than 1rad/m^2^ over several degrees. These holes in the foreground RM will be useful for future studies of possible small-scale fluctuations in cosmic magnetic field structures. In addition to allowing measurement of RMs toward polarized sources, the new analysis of the NVSS data removes the effects of bandwidth depolarization for |RM|>~100rad/m^2^ inherent in the original NVSS source catalog.
- ID:
- ivo://CDS.VizieR/J/other/JApA/32.567
- Title:
- Rotation measures in A2255 at 18, 21, 25, 85cm
- Short Name:
- J/other/JApA/32.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Polarized radio emission is detected at various scales in the Universe. In this document, I will briefly review our knowledge on polarized radio sources in galaxy clusters and at their outskirts, emphasizing the crucial information provided by the polarized signal on the origin and evolution of such sources. Successively, I will focus on Abell 2255, which is known in the literature as the first cluster for which filamentary polarized emission associated with the radio halo has been detected. By using RM (plasma Rotation Measure) synthesis on our multi-wavelength WSRT observations, we studied the 3-dimensional geometry of the cluster, unveiling the nature of the polarized filaments at the borders of the central radio halo. Our analysis points out that these structures are relics lying at large distance from the cluster center.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/92
- Title:
- Rotation measures in radio source pairs
- Short Name:
- J/ApJ/878/92
- Date:
- 03 Mar 2022 08:14:01
- Publisher:
- CDS
- Description:
- Faraday rotation measures (RMs) of extragalactic radio sources provide information on line-of-sight magnetic fields, including contributions from our Galaxy, source environments, and the intergalactic medium (IGM). Looking at differences in RMs, {Delta}RM, between adjacent sources on the sky can help isolate these different components. In this work, we classify adjacent polarized sources in the NRAO VLA Sky Survey (NVSS) as random or physical pairs. We recompute and correct the uncertainties in the NVSS RM catalog, since these were significantly overestimated. Our sample contains 317 physical and 5111 random pairs, all with Galactic latitudes |b|>=20{deg}, polarization fractions >=2%, and angular separations between 1.5' and 20'. We find an rms {Delta}RM of 14.9+/-0.4 and 4.6+/-1.1rad/m^2^ for the random and physical pairs, respectively. This means that polarized extragalactic sources that are close on the sky but at different redshifts have larger differences in RM than two components of one source. This difference of ~10rad/m^2^ is significant at 5{sigma} and persists in different data subsamples. While there have been other statistical studies of {Delta}RM between adjacent polarized sources, this is the first unambiguous demonstration that some of this RM difference must be extragalactic, thereby providing a firm upper limit on the RM contribution of the IGM. If the {Delta}RMs originate local to the sources, then the local magnetic field difference between random sources is a factor of 2 larger than that between components of one source. Alternatively, attributing the difference in {Delta}RMs to the intervening IGM yields an upper limit on the IGM magnetic field strength of 40nG.
- ID:
- ivo://CDS.VizieR/J/ApJ/755/21
- Title:
- Rotation measures of extragalactic radio sources
- Short Name:
- J/ApJ/755/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the Milky Way disk and halo magnetic field, determined from observations of Faraday rotation measure (RM) toward 641 polarized extragalactic radio sources in the Galactic longitude range 100{deg}-117{deg}, within 30{deg} of the Galactic plane. For |b|<15{deg}, we observe a symmetric RM distribution about the Galactic plane. This is consistent with a disk field in the Perseus arm of even parity across the Galactic mid-plane. In the range 15{deg}<|b|<30{deg}, we find median RMs of -15+/-4rad/m2 and -62+/-5rad/m2 in the northern and southern Galactic hemispheres, respectively. If the RM distribution is a signature of the large-scale field parallel to the Galactic plane, then this suggests that the halo magnetic field toward the outer Galaxy does not reverse direction across the mid-plane. The variation of RM as a function of Galactic latitude in this longitude range is such that RMs become more negative at larger |b|. This is consistent with an azimuthal magnetic field of strength 2{mu}G (7{mu}G) at a height 0.8-2kpc above (below) the Galactic plane between the local and the Perseus spiral arm. We propose that the Milky Way could possess spiral-like halo magnetic fields similar to those observed in M51.