- ID:
- ivo://CDS.VizieR/J/A+A/617/L5
- Title:
- Water delivery in Pluto and Triton atmospheres
- Short Name:
- J/A+A/617/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Both Pluto and Triton possess thin, N_2_-dominated atmospheres controlled by sublimation of surface ices. We aim to constrain the influx and ablation of interplanetary dust grains into the atmospheres of both Pluto and Triton in order to estimate the rate at which oxygen-bearing species are introduced into both atmospheres. We use (i) an interplanetary dust dynamics model to calculate the flux and velocity distributions of interplanetary dust grains relevant for both Pluto and Triton and (ii) a model for the ablation of interplanetary dust grains in the atmospheres of both Pluto and Triton. We sum the individual ablation profiles over the incoming mass and velocity distributions of interplanetary dust grains in order to determine the vertical structure and net deposition of water to both atmospheres. Our results show that <2% of silicate grains ablate at either Pluto or Triton while approximately 75% and >99% of water ice grains ablate at Pluto and Triton, respectively. From ice grains, we calculate net water influxes to Pluto and Triton of ~3.8kg/d (8.5x10^3^H_2_O/cm^2^/s) and ~370kg/d (6.2x10^5^H_2_O/cm^2^/s), respectively. The significant difference in total water deposition between Pluto and Triton is due to the presence of Triton within Neptune's gravity well, which both enhances interplanetary dust particle (IDP) fluxes due to gravitational focusing and accelerates grains before entry into Triton's atmosphere, thereby causing more efficient ablation. We conclude that water deposition from dust ablation plays only a minor role at Pluto due to its relatively low flux. At Triton, water deposition from IDPs is more significant and may play a role in the alteration of atmospheric and ionospheric chemistry. We also suggest that meteoric smoke and smaller, unablated grains may serve as condensation nuclei for the formation of hazes at both worlds.
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- ID:
- ivo://CDS.VizieR/J/A+A/610/A9
- Title:
- Water ice spectra toward the Pipe Nebula
- Short Name:
- J/A+A/610/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic studies of ices in nearby star-forming regions indicate that ice mantles form on dust grains in two distinct steps, starting with polar ice formation (H_2_O rich) and switching to apolar ice (CO rich). We test how well the picture applies to more diffuse and quiescent clouds where the formation of the first layers of ice mantles can be witnessed. Medium-resolution near-infrared spectra are obtained toward background field stars behind the Pipe Nebula. The water ice absorption is positively detected at 3.0um in seven lines of sight out of 21 sources for which observed spectra are successfully reduced. The peak optical depth of the water ice is significantly lower than those in Taurus with the same A_V_. The source with the highest water-ice optical depth shows CO ice absorption at 4.7um as well. The fractional abundance of CO ice with respect to water ice is 16+7-6%, and about half as much as the values typically seen in low-mass star-forming regions. A small fractional abundance of CO ice is consistent with some of the existing simulations. Observations of CO2 ice in the early diffuse phase of a cloud play a decisive role in understanding the switching mechanism between polar and apolar ice formation.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A139
- Title:
- Water lines spectra of 4 protostellar objects
- Short Name:
- J/A+A/587/A139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Herschel/HIFI observations of 14 water lines in a small sample of galactic massive protostellar objects: NGC6334I(N), DR21(OH), IRAS16272-4837, and IRAS05358+3543. Using water as a tracer of the structure and kinematics, we aim to individually study each of these objects, to estimate the amount of water around them, but to also shed light on the high-mass star formation process. We analyze the gas dynamics from the line profiles using Herschel-HIFI observations acquired as part of the WISH key-project of 14 far-IR water lines (water, H_2_^17^O, H_2_^18^O), and several other species. Then through modeling of the observations using the RATRAN radiative transfer code, we estimate outflow, infall, turbulent velocities, molecular abundances, and investigate any correlation with the evolutionary status of each source. The four sources (plus previously studied W43-MM1) have been ordered in terms of evolution based on their SED: NGC64334I(N)-W43-MM1-DR21(OH)-IRAS16272-4837-IRAS05358+3543. The molecular line profiles exhibit a broad component coming from the shocks along the cavity walls associated with the protostars, and an infalling (or expansion for IRAS05358+3543) and passively heated envelope component, with highly supersonic turbulence likely increasing with the distance from the center. Accretion rates between 6.3x10^-5^ and 5.6x10^-4^M_{sun}_/yr are derived from the infall observed in three of our sources. The outer water abundance is estimated to be at the typical value of a few 10^-8^ while the inner abundance varies from 1.7x10^-6^ to 1.4x10^-4^ with respect to H_2_ depending on the source. We confirm that regions of massive star formation are highly turbulent and that the turbulence likely increases in the envelope with the distance to the star. The inner abundances are lower than the expected 10^-4^ perhaps because our observed lines do not probe deep enough into the inner envelope, or because photodissociation through protostellar UV photons is more efficient than expected. We show that the higher the infall/expansion velocity in the protostellar envelope, the higher is the inner abundance, maybe indicating that larger infall/expansion velocities generate shocks that will sputter water from the ice mantles of dust grains in the inner region. High-velocity water must be formed in the gas-phase from shocked material.
- ID:
- ivo://CDS.VizieR/J/ApJ/764/61
- Title:
- Water maser and NH_3_ survey of GLIMPSE EGOs
- Short Name:
- J/ApJ/764/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a Nobeyama 45m H_2_O maser and NH_3_ survey of all 94 northern GLIMPSE extended green objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5{mu}m emission. We observed the NH_3_(1,1), (2,2), and (3,3) inversion lines, and detected emission toward 97%, 63%, and 46% of our sample, respectively (median rms~50mK). The H_2_O maser detection rate is 68% (median rms~0.11Jy). The derived H_2_O maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on mid-infrared (MIR) properties or maser associations. H_2_O masers and warm dense gas, as indicated by emission in the higher-excitation NH_3_ transitions, are most frequently detected toward EGOs also associated with both Class I and II CH_3_OH masers. Ninety-five percent (81%) of such EGOs are detected in H_2_O (NH_3_(3,3)), compared to only 33% (7%) of EGOs without either CH_3_OH maser type. As populations, EGOs associated with Class I and/or II CH_3_OH masers have significantly higher NH_3_ line widths, column densities, and kinetic temperatures than EGOs undetected in CH_3_OH maser surveys. However, we find no evidence for statistically significant differences in H_2_O maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic H_2_O maser luminosity and clump number density. H_2_O maser luminosity is weakly correlated with clump (gas) temperature and clump mass.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A162
- Title:
- Water maser data of 380 galaxies
- Short Name:
- J/A+A/641/A162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Water megamaser emission at 22GHz has proven to be a powerful tool for astrophysical studies of active galactic nuclei (AGN) because it allows an accurate determination of the mass of the central black hole and of the accretion disc geometry and dynamics. However, after searches among thousands of galaxies, only ~200 of them have shown such spectroscopic features, most of them of uncertain classification. In addition, the physical and geometrical conditions under which a maser activates are still unknown. We characterize the occurrence of water maser emission in an unbiased sample of AGN by investigating the relation with the X-ray properties and the possible favourable geometry that is required to detect water maser. We searched for 22GHz maser emission in a hard X-ray selected sample of AGN, taken from the INTEGRAL/IBIS survey above 20keV. Only half of the 380 sources in the sample have water maser data. We also considered a volume-limited sub-sample of 87 sources, for which we obtained new observations with the Green Bank and Effelsberg telescopes (for 35 sources). We detected one new maser and increased its radio coverage to 75%. The detection rate of water maser emission in the total sample is 15+/-3%. This fraction increases to 19+/-5% for the complete sub-sample, especially when we consider type 2 (22+/-5% and 31+/-10% for the total and complete samples, respectively) and Compton-thick AGN (56+/-18% and 50+/-35% for the total and complete samples, respectively). No correlation is found between water maser and X-ray luminosity. We note that all types of masers (disc and jet) are associated with hard X-ray selected AGN. These results demonstrate that the hard X--ray selection may significantly enhance the maser detection efficiency over comparably large optical or infrared surveys. A possible decline in detection fraction with increasing luminosity might suggest that an extremely luminous nuclear environment does not favour maser emission. The large fraction of CT AGN with water maser emission could be explained in terms of geometrical effects. The maser medium would then be the very edge-on portion of the obscuring medium.
- ID:
- ivo://CDS.VizieR/J/ApJ/652/136
- Title:
- Water maser emission in five AGNs
- Short Name:
- J/ApJ/652/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of water maser emission in five active galactic nuclei (AGNs) with the 100m Green Bank Telescope (GBT). The positions of the newly discovered masers, measured with the VLA, are consistent with the optical positions of the host nuclei to within 1{sigma} (0.3" radio and 1.3" optical) and most likely mark the locations of the embedded central engines. The spectra of three sources, 2MASX J08362280+3327383, NGC 6264, and UGC 09618 NED02 (PGC 053432), display the characteristic spectral signature of emission from an edge-on accretion disk with maximum orbital velocity of ~700, ~800, and ~1300km/s, respectively. We also present a GBT spectrum of a previously known source, Mrk 0034, and interpret the narrow Doppler components reported here as indirect evidence that the emission originates in an edge-on accretion disk with orbital velocity of ~500km/s .
- ID:
- ivo://CDS.VizieR/J/A+A/578/A119
- Title:
- Water maser emission toward post-AGB and PN
- Short Name:
- J/A+A/578/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Water maser emission at 22GHz is a useful probe for studying the transition between the nearly spherical mass loss in the asymptotic giant branch (AGB) to a collimated one in the post-AGB phase. In their turn, collimated jets in the post-AGB phase could determine the shape of planetary nebulae once photoionization starts. We intend to find new cases of post-AGB stars and planetary nebulae (PNe) with water maser emission, including some especially interesting and rare types: water fountains (evolved objects with high velocity collimated jets traced by water masers) or water-maser-emitting PNe. Since previous studies have shown a higher detection rate of water maser emission in evolved objects that are optically obscured, we selected a sample that contains a significant fraction of post-AGB and young PN candidate sources showing signs of strong obscuration. We searched for water maser emission in 133 evolved objects using the radio telescopes in Robledo de Chavela, Parkes, and Green Bank. We detected water maser emission in 15 sources of our sample, of which seven are reported here for the first time (IRAS 13483-5905, IRAS 14249-5310, IRAS 15408-5413, IRAS 17021-3109, IRAS 17348-2906, IRAS 17393-2727, and IRAS 18361-1203). We identified three water fountain candidates: IRAS 17291-2147, with a total velocity spread of =~96km/s in its water maser components and two sources (IRAS 17021-3109 and IRAS 17348-2906) that show water maser emission whose velocity lies outside the velocity range covered by OH masers. We have also identified IRAS 17393-2727 as a possible new water-maser-emitting PN. The detection rate is higher in obscured objects (14%) than in those with optical counterparts (7%), which is consistent with previous results. Water maser emission seems to be common in objects that are bipolar in the near-IR (43% detection rate in such sources). The water maser spectra of water fountain candidates like IRAS 17291-2147 show significantly fewer maser components than others (e.g., IRAS 18113-2503). We speculate that most post-AGBs may show water maser emission with wide enough velocity spread (>=100km/s) when observed with enough sensitivity and/or for long enough periods of time. Therefore, it may be necessary to single out a special group of "water fountains", probably defined by their high maser luminosities. We also suggest that the presence of both water and OH masers in a PN is a better tracer of its youth, than is the presence of just one of these species.
- ID:
- ivo://CDS.VizieR/J/A+AS/120/283
- Title:
- Water maser features in ultracompact HII regions
- Short Name:
- J/A+AS/120/283
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present high resolution images and spectra toward 21 H_2_O maser sources in the vicinity of ultracompact (UC) HII regions. This survey provides the basis for future studies with milli-arcsecond resolution, utilizing very long baseline interferometry (VLBI) techniques. Emission from the 6_16_-5_23_ masing transition of interstellar H_2_O is observed in the close vicinity of UC HII regions with a median angular distance of 2.9" and a median linear projected distance of 0.1pc from the continuum peak. We find that for UC HII regions with cometary morphology the water maser emission is located in front of the cometary arc whereas for non-cometary UC HII regions the water masers are often observed projected onto the contours of the ionized gas. Due to the large median distance of the water masers from the I-front of the UC HII region, it is unlikely, that the water masers are formed in the shocked layer of warm molecular gas in the interface between the ionized gas of the UC HII region and surrounding molecular gas which is predicted by the Bow Shock theory of UC HII regions. A comparison with maps in the NH_3_ inversion transitions shows that in at least 7 cases, the water masers are associated with hot (T>100K), dense (n(H_2_)=~10^7^cm^-3^) molecular clumps. For the UC HII regions G5.89-0.38 and G45.07+0.13 we find spatial and velocity correspondence between water masers and outflowing molecular gas. It is thus likely, that for these sources the H_2_O masers are taking part in the bipolar outflow.
- ID:
- ivo://CDS.VizieR/J/PASJ/59/1185
- Title:
- Water maser in galactic IRAS sources
- Short Name:
- J/PASJ/59/1185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present H_2_O maser data from a survey toward IRAS sources in the Galaxy with the Nobeyama 45m telescope. This survey had a 1{sigma} noise level as small as 0.24Jy, resulting in one of the most sensitive water-maser surveys. The maximum distance of the masers to be detected by our survey is estimated to be 3kpc for sources with F_nu,1kpc_<10Jy and 10kpc for those with 10Jy<=F_nu,1kpc_<100Jy, where F_nu,1kpc_ is the maser flux density converted at a distance of 1kpc. For strong masers with F_nu,1kpc_>=100Jy, our survey could detect all sources in the Galaxy. We carried out a total of 2229 observations toward 1563 sources and detected water-maser emission toward 222 sources. Our survey newly found masers from 75 of the 222 sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/769/48
- Title:
- Water maser in Orion-KL with Herschel
- Short Name:
- J/ApJ/769/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have performed mapping observations of the 620.701GHz 5_32_-4_41_ transition of ortho-H_2_O within a ~1.5'x1.5' region encompassing the Kleinmann-Low nebula in Orion (Orion-KL), and pointed observations of that transition toward the Orion South condensation and the W49N region of high-mass star formation. Using the Effelsberg 100m radio telescope, we obtained ancillary observations of the 22.23508GHz 6_16_-5_23_ water maser transition; in the case of Orion-KL, the 621GHz and 22GHz observations were carried out within 10days of each other. The 621GHz water line emission shows clear evidence for strong maser amplification in all three sources, exhibiting narrow (~1km/s FWHM) emission features that are coincident (kinematically and/or spatially) with observed 22GHz features. Moreover, in the case of W49N --for which observations were available at three epochs spanning a 2yr period-- the spectra exhibited variability. The observed 621GHz/22GHz line ratios are consistent with a maser pumping model in which the population inversions arise from the combined effects of collisional excitation and spontaneous radiative decay, and the inferred physical conditions can plausibly arise in gas heated by either dissociative or non-dissociative shocks. The collisional excitation model also predicts that the 22GHz population inversion will be quenched at higher densities than that of the 621GHz transition, providing a natural explanation for the observational fact that 22GHz maser emission appears to be a necessary but insufficient condition for 621GHz maser emission.
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