- ID:
- ivo://CDS.VizieR/J/A+A/327/755
- Title:
- OH maser emission from IRAS sources
- Short Name:
- J/A+A/327/755
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A high-sensitivity search for water maser emission at 22.2 GHz has been performed on a sample of 91 IRAS point sources at high-latitudes. The aim of the survey is to verify if these clouds are capable of star formation as indicated by the presence of water masers. The sample is based on the recent work of Magnani et al. (1995ApJS...96..159M) who have identified 192 infrared objects from the IRAS Faint Source Survey possibly associated with translucent clouds at galactic latitudes |b|>=30{deg}. These IRAS sources have far-infrared colours typical of young stellar objects and pre-main-sequence stars and thus provide a starting list for further studies about their actual nature. H_2_O maser emission is a good diagnostic of the presence of dense gas and of recent star formation. We did not find water maser emission at a level of 0.2-0.5Jy (3{sigma}) in any of the 91 objects. The negative result indicates that these high-latitude sources do not represent potential sites of star formation, consistent with the fact that most high-latitude molecular clouds do not appear gravitationally bound.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/155/595
- Title:
- OH maser IRAS and MSX observations
- Short Name:
- J/ApJS/155/595
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present OH maser observations at 1612, 1665, 1667, and 1720MHz for 86 likely post-asymptotic giant branch (post-AGB) stars selected from a survey of 1612MHz maser sources in the Galactic plane. The observations were taken with the Parkes Telescope and the Australia Telescope Compact Array between 2002 September and 2003 August. We redetected all 86 sources at 1612MHz, while 27 sources were detected at 1665MHz and 45 at 1667MHz. One source was redetected at 1720MHz. We present a classification scheme for the maser profiles and show that 25% of sources in our sample are likely to have asymmetric or bipolar outflows.
- ID:
- ivo://CDS.VizieR/J/AJ/124/100
- Title:
- OH megamasers at z>0.1. III
- Short Name:
- J/AJ/124/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the final results from the Arecibo Observatory OH megamaser survey. We discuss in detail the properties of the remaining 18 OH megamasers detected in the survey, including three redetections. We place upper limits on the OH emission from 85 nondetections and examine the properties of 25 ambiguous cases for which the presence or absence of OH emission could not be determined. The complete survey has discovered 50 new OH megamasers (OHMs) in (ultra)luminous infrared galaxies ([U]LIRGs), which doubles the sample of known OHMs and increases the sample at z>0.1 sevenfold.
- ID:
- ivo://CDS.VizieR/J/AJ/123/2772
- Title:
- OH-selected AGB and post-AGB objects. I.
- Short Name:
- J/AJ/123/2772
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 766 compact objects found in a systematic survey of the Galactic plane in the 1612MHz masing OH line, new light is cast on the IR properties of evolved stars on the thermally pulsing asymptotic giant branch (AGB) and beyond. The usual mid-IR selection criteria for post-AGB, based on IRAS colors, largely fail to distinguish early post-AGB stages. A two-color diagram from much narrower band MSX flux densities, with bimodal distributions, provides a better tool for doing this. Four mutually consistent selection criteria for OH-masing red protoplanetary nebulae are given, as well as two for early post-AGB masers and one for all post-AGB masers including the earliest ones. All these criteria miss a group of blue, high-outflow post-AGB sources with 60{mu}m excess; these will be discussed in detail in Paper II (Sevenster, 2002AJ....123.2772S). The majority of post-AGB sources show regular double-peaked spectra in the OH 1612MHz line, with fairly low outflow velocities, although the fractions of single peaks and irregular spectra may vary with age and mass. The OH flux density shows a fairly regular relation with the stellar flux and the envelope optical depth, with the maser efficiency increasing with IRAS color R_21_. The OH flux density is linearly correlated with the 60{mu}m flux density.
- ID:
- ivo://CDS.VizieR/J/ApJ/549/155
- Title:
- [OIII] emission in a sample of AGNs
- Short Name:
- J/ApJ/549/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The emission-line flux ratio of [OIII]4363/[OIII]5007 (R_OIII_) is a useful diagnostic for the ionization mechanism and physical properties of emission-line regions in active galactic nuclei (AGNs). However, it is known that simple photoionization models underpredict the [OIII]4363 intensity, being inconsistent with observations. In this paper we report on several pieces of evidence that a large fraction of the [OIII]4363 emission arises from the dense gas obscured by putative tori: (1) the visibility of high-R_OIII_ regions is correlated to that of broad-line regions, (2) higher R_OIII_ objects show hotter mid-infrared colors, (3) higher R_OIII_ objects show stronger highly ionized emission lines such as [FeVII] 6087 and [FeX]6374, and (4) higher R_OIII_ objects have broader line width of [OIII]4363 normalized by that of [OIII]5007.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A26
- Title:
- OMC-2 FIR 3 and FIR 4 [OI] maps
- Short Name:
- J/A+A/596/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first detection of a jet in the far-IR [OI] lines from an intermediate mass protostar. We have carried out a Herschel/PACS spectral mapping study in the [OI] lines of OMC-2 FIR 3 and FIR 4, two of the most luminous protostars in Orion outside of the Orion Nebula. The spatial morphology of the fine structure line emission reveals the presence of an extended photodissociation region (PDR) and a narrow, but intense jet emission connecting the two protostars. The jet seen in [OI] emission is spatially aligned with the Spitzer/IRAC 4.5um jet and the CO (6-5) molecular outflow centered on FIR 3. The mass loss rate derived from the total [OI] 63um line luminosity of the jet is 7.7*10^-6^M_{sun}_/yr, which is more than an order of magnitude higher than that measured for typical low mass class 0 protostars. The implied accretion luminosity is significantly higher than the observed bolometric luminosity of FIR 4, indicating that the [OI] jet is unlikely to be associated with FIR 4. We argue that the peak line emission seen toward FIR 4 originates in the terminal shock produced by the jet driven by FIR 3. The higher mass loss rate that we find for FIR 3 is consistent with the idea that intermediate mass protostars drive more powerful jets than their low-mass counterparts. Our results also call into question the nature of FIR 4.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A136
- Title:
- OMC-2 FIR4 fits images
- Short Name:
- J/A+A/657/A136
- Date:
- 21 Mar 2022 09:38:35
- Publisher:
- CDS
- Description:
- Isotopic fractionation is an important tool for investigating the chemical history of our Solar System. In particular, the isotopic fraction of nitrogen (^14^N/^15^N) is lower in comets and other pristine Solar System bodies with respect to the value measured for the protosolar nebula, suggesting a local chemical enrichment of ^15^N during the formation of the Solar System. Therefore, interferometric studies of nitrogen fractionation in Solar System precursors are needed for us to obtain clues about our astrochemical origins. In this work we have investigated the variation in the ^14^N/^15^N ratio in one of the closest analogues of the environment in which the Solar System was born: the protocluster OMC-2 FIR4. We present the first comparison at high angular resolution between HCN and N_2_H^+^ using interferometric data. We analysed observations of the HCN isotopologues H^13^CN and HC^15^N in the OMC-2 FIR4 protocluster. Specifically, we observed the transitions H^13^CN (1-0) and HC^15^N (1-0) with the NOrthern Extended Millimeter Array (NOEMA) within the context of the IRAM Seeds Of Life In Space (SOLIS) Large Program. We combined our results with analysis of archival data obtained with the Atacama Large Millimeter Array (ALMA) of N_2_H^+^ and its ^15^N isotopologues. Our results show a small regional variation in the ^14^N/^15^N ratio for HCN, from ~250 to 500. The ratios in the central regions of FIR4, where the candidate protostars are located, are largely consistent with one another and within that range (~300). They also show little variation from the part of the protocluster known to harbour a high cosmic-ray ionisation rate to the portion with a lower rate. We also found a small variation in the ^14^N/^15^N ratio of N_2_H^+^ across different regions, from ~200 to ~400. These results suggest that local changes in the physical parameters occurring on the small linear scales probed by our observations in the protocluster do not seem to affect the ^14^N/^15^N ratio in either HCN or N_2_H^+^ and hence that this is independent of the molecule used. Moreover, the high level of irradiation due to cosmic rays does not affect the N fractionation either.
- ID:
- ivo://CDS.VizieR/J/AJ/135/1395
- Title:
- omega Cen Spitzer photometry
- Short Name:
- J/AJ/135/1395
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a Spitzer Space Telescope imaging survey of the most massive Galactic globular cluster, {omega} Centauri, and investigate stellar mass loss at low metallicity and the intracluster medium (ICM). The survey covers approximately 3.2x the cluster half-mass radius at 3.6, 4.5, 5.8, 8, and 24um, resulting in a catalog of over 40000 point sources in the cluster.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/14
- Title:
- Optical & FeII sources in Supernova remnant with HST
- Short Name:
- J/ApJ/899/14
- Date:
- 14 Mar 2022 07:07:21
- Publisher:
- CDS
- Description:
- NGC6946 is a high-star-formation-rate, face-on, spiral galaxy that has hosted 10 supernovae since 1917. Not surprisingly, a large number of supernova remnants and candidates have been identified either as optical nebulae with high [SII]:H{alpha} line ratios (147) or as compact non-thermal radio sources (35). However, there are only seven overlaps between these two samples. Here, we apply [FeII] 1.644{mu}m emission as a new diagnostic to search for supernova remnants in an attempt to resolve this discrepancy. [FeII] is expected to be relatively strong in the radiative shocks of supernova remnants and almost absent in HII regions. It is less susceptible to the effects of absorption along the line of sight than the optical lines normally used to identify remnants. Using data from the WFC3 camera on Hubble Space Telescope (HST), we identify 132 [FeII] emission nebulae in NGC6946 as likely supernova remnants. Of these, 54 align with previously known optical supernova remnants. The remaining 78 objects are new; of these 44 are visible in new HST imagery in H{alpha} and [SII]. This brings the total number of supernova remnant candidates (from optical and/or IR data) in NGC6946 to 225. A total of 14 coincidences with radio supernova remnant candidates (out of 30 in our search area) are found in this expanded list. The identification of so many new remnant candidates validates the use of [FeII] imagery for finding remnants, and suggests that previous remnant searches in other galaxies may be far from complete.
- ID:
- ivo://CDS.VizieR/J/MNRAS/472/334
- Title:
- Optical/MIR properties of Type 1 AGNs
- Short Name:
- J/MNRAS/472/334
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigated the connection between the mid-infrared (MIR) and optical spectral characteristics in a sample of 82 Type 1 active galactic nuclei (AGNs), observed with Infrared Spectrometer on Spitzer (IRS) and Sloan Digital Sky Survey (SDSS, DR12). We found several interesting correlations between optical and MIR spectral properties: (i) as starburst significators in MIR increase, the equivalent widths (EWs) of optical lines H{beta}NLR and FeII, increase as well; (ii) as MIR spectral index increases, EW([OIII]) decreases, while fractional contribution of AGN (RAGN) is not connected with EW([OIII]); (iii) The log([OIII]5007/H{beta}NLR) ratio is weakly related to the fractional contribution of polycyclic aromatic hydrocarbons (RPAHs). We compare the two different MIR and optical diagnostics for starburst contribution to the overall radiation (RPAH and Baldwin, Philips & Terlevich diagram, respectively). The significant differences between optical and MIR starburst diagnostics were found. The starburst influence to observed correlations between optical and MIR parameters is discussed.
