Water maser variability over 20 years in a large sample of star-forming regions: the complete database

Felli, M.; Brand, J.; Cesaroni, R.; Codella, C.; Comoretto, G.; Franco, S.; Massi, F.; Moscadelli, L.; Nesti, R.; Olmi, L.; Palagi, F.; Panella, D.; Valdettaro, R.

doi:10.1051/0004-6361:20077804

Cited by 76 publications

(70 citation statements)

References 40 publications

(32 reference statements)

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“…(a) These sources have poor uv-coverage, thus no position for the maser spots is given. Table C.3), as expected because of the wellknown variability of water masers (e.g., Felli et al 2007). All of these sources show other signs of active star formation.…”

Section: Water Maser Emissionmentioning

confidence: 57%

Physical properties of high-mass clumps in different stages of evolution

Giannetti

Brand

Sánchez-Monge

et al. 2013

A&A

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Context. The details of the process of massive star formation are still elusive. A complete characterization of the first stages of the process from an observational point of view is needed to constrain theories on the subject. In the past 20 years we have made a thorough investigation of colour-selected IRAS sources over the whole sky. The sources in the northern hemisphere were studied in detail and used to derive an evolutionary sequence based on their spectral energy distribution. Aims. To investigate the first stages of the process of high-mass star formation, we selected a sample of massive clumps previously observed with the Swedish-ESO Submillimetre Telescope at 1.2 mm and with the ATNF Australia Telescope Compact Array at 1.3 cm. We want to characterize the physical conditions in such sources, and test whether their properties depend on the evolutionary stage of the clump. Methods. With ATCA we observed the selected sources in the NH 3 (1, 1) and (2, 2) transitions and in the H 2 O(6 16 −5 23 ) maser line. Ammonia lines are a very good temperature probe that allow us to accurately determine the mass and the column, volume, and surface densities of the clumps. We also collected all data available to construct the spectral energy distribution of the individual clumps and to determine if star formation is already occurring through observations of its most common signposts, thus putting constraints on the evolutionary stage of the source. We fitted the spectral energy distribution between 1.2 mm and 70 µm with a modified black body to derive the dust temperature and independently determine the mass. Results. We find that the clumps are cold (T ∼ 10−30 K), massive (M ∼ 10 2 −10 3 M ), and dense (n(H 2 ) 10 5 cm −3 ) and that they have high column densities (N(H 2 ) ∼ 10 23 cm −2 ). All clumps appear to be potentially able to form high-mass stars. The most massive clumps appear to be gravitationally unstable, if the only sources of support against collapse are turbulence and thermal pressure, which possibly indicates that the magnetic field is important in stabilizing them. Conclusions. After investigating how the average properties depend on the evolutionary phase of the source, we find that the temperature and central density progressively increase with time. Sources likely hosting a ZAMS star show a steeper radial dependence of the volume density and tend to be more compact than starless clumps.

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Section: Water Maser Emissionmentioning

confidence: 57%

Physical properties of high-mass clumps in different stages of evolution

Giannetti

Brand

Sánchez-Monge

et al. 2013

A&A

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“…Such a low number of usable spots is not surprising, due to the well known variability of H 2 O maser emission (see e.g. Felli et al 2007). Moreover, this emission happened to be especially faint in IRAS 20126+4104 during the period of our observations.…”

Section: The Distance To Iras 20126+4104mentioning

confidence: 99%

Methanol and water masers in IRAS 20126+4104: the distance, the disk, and the jet

Moscadelli

Cesaroni

Rioja

et al. 2010

A&A

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104

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Context. Knowledge of the distance to high-mass star forming regions is crucial to obtain accurate luminosity and mass estimates of young OB-type (proto)stars and thus better constrain their nature and age. IRAS 20126+4104 is a special case, being the best candidate of a high-mass (proto)star surrounded by an accretion disk. Such a fact may be used to set constraints on theories of highmass star formation, but requires confirmation that the mass and luminosity of IRAS 20126+4104 are indeed typical of a B0.5 star, which in turn requires an accurate estimate of the distance. Aims. The goal of our study is twofold: to determine the distance to IRAS 20126+4104, using the parallax of H 2 O masers associated with the source, and unveil the 3D velocity field of the disk, through proper motion measurements of the 6.7 GHz CH 3 OH masers. At the same time, we can also obtain an estimate of the systemic velocity in the plane of the sky of the disk+star system. Methods. We used the Very Long Baseline Array and the European VLBI Network to observe the 22.2 GHz H 2 O and 6.7 GHz CH 3 OH masers in IRAS 20126+4104 at a number of epochs suitably distributed in time. The absolute positions of the maser features were established with respect to reference quasars, which allowed us to derive absolute proper motions. Results. From the parallax of the H 2 O masers we obtain a distance of 1.64 ± 0.05 kpc, which is very similar to the value adopted so far in the literature (1.7 kpc) and confirms that IRAS 20126+4104 is a high-mass (proto)star. From the CH 3 OH masers we derive the component in the plane of the sky of the systemic velocity of the disk+star system (−16 km s −1 in right-ascension and +7.6 km s −1 in declination). Accurate knowledge of the distance and systemic velocity allows us to improve on the model fit to the H 2 O maser jet presented in a previous study. Finally, we identify two groups of CH 3 OH maser features, one undergoing rotation in the disk and possibly distributed along a narrow ring centered on the star, the other characterised by relative proper motions indicating that the features are moving away from the disk, perpendicular to it. We speculate that the latter group might be tracing the disk material marginally entrained by the jet. Conclusions. VLBI multi-epoch observations with phase referencing are confirmed to be an excellent tool for distance determinations and for the investigation of the structure and 3D velocity field within a few 100 AU from newly born high-mass stars.

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“…Studying variability over long timescales is very time consuming, hence variability studies over many epochs tend to be with smaller sample sizes (Brand et al 2003;Felli et al 2007). …”

Section: Variabilitymentioning

confidence: 99%

A search for water masers associated with class II methanol masers – II. Longitude range 341° to 6°

Titmarsh

Ellingsen

Breen

et al. 2016

Mon. Not. R. Astron. Soc.

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This is the second paper in a series of catalogues of 22-GHz water maser observations towards the 6.7-GHz methanol masers from the Methanol Multibeam (MMB) Survey. In this paper we present our water maser observations made with the Australia Telescope Compact Array towards the masers from the MMB survey between l = 341 • through the Galactic centre to l = 6 • . Of the 204 6.7-GHz methanol masers in this longitude range we found 101 to have associated water maser emission (∼ 50 per cent). We found no difference in the 6.7-GHz methanol maser luminosities of those with and without water masers. In sources where both maser species are observed, the luminosities of the methanol and water masers are weakly correlated. Studying the mid-infrared colours from GLIMPSE we found no differences between the colours of those sources associated with both methanol and water masers and those associated with just methanol. Comparing the column density and dust mass calculated from the 870-µm thermal dust emission observed by ATLASGAL, we found no differences between those sources associated with both water and methanol masers and those with methanol only. Since water masers are collisionally pumped and often show emission further away from their accompanying YSO than the radiatively pumped 6.7-GHz methanol masers, it is likely water masers are not as tightly correlated to the evolution of the parent YSO and so do not trace such a well defined evolutionary state as 6.7-GHz methanol masers.

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Water maser variability over 20 years in a large sample of star-forming regions: the complete database

Cited by 76 publications

References 40 publications

Physical properties of high-mass clumps in different stages of evolution

Physical properties of high-mass clumps in different stages of evolution

Methanol and water masers in IRAS 20126+4104: the distance, the disk, and the jet

A search for water masers associated with class II methanol masers – II. Longitude range 341° to 6°

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