The distance to the center of the Galaxy - H2O maser proper motions in Sagittarius B2(N)

Reid, M. J.; Schneps, M. H.; Moran, J. M.; Gwinn, C. R.; Genzel, R.; Downes, D.; Roennaeng, B.

doi:10.1086/166514

Cited by 216 publications

(149 citation statements)

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“…1 from Reid et al (1988). Considering the beam major axis (∼0.9 ), we derive relative positional accuracies between 0.2 for SNR of 4.6 (LB31) and ∼5 mas for a SNR of 176 (LB14).…”

Section: Alma Observationsmentioning

confidence: 96%

A search for pre- and proto-brown dwarfs in the dark cloud Barnard 30 with ALMA

Huélamo

Gregorio-Monsalvo

Palau

et al. 2016

A&A

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Context. The origin of brown dwarfs is still under debate. While some models predict a star-like formation scenario, others invoke a substellar mass embryo ejection, a stellar disk fragmentation, or the photo-evaporation of an external core due to the presence of massive stars. Aims. The aim of our work is to characterize the youngest and lowest mass population of the dark cloud Barnard 30, a region within the Lambda Orionis star-forming region. In particular, we aim to identify proto-brown dwarfs and study the mechanism of their formation. Methods. We obtained ALMA continuum observations at 880 µm of 30 sub-mm cores previously identified with APEX/LABOCA at 870 µm. We have complemented part of the ALMA data with sub-mm APEX/SABOCA observations at 350 µm, and with multiwavelength ancillary observations from the optical to the far-infrared (e.g., Spitzer, CAHA/O2000, WISE, INT/WFC). Results. We report the detection of five (out of 30) spatially unresolved sources with ALMA, with estimated masses between 0.9 and 67 M Jup . From these five sources, only two show gas emission. The analysis of multi-wavelength photometry from these two objects, namely B30-LB14 and B30-LB19, is consistent with one Class II-and one Class I low-mass stellar object, respectively. The gas emission is consistent with a rotating disk in the case of B30-LB14, and with an oblate rotating envelope with infall signatures in the case of LB19. The remaining three ALMA detections do not have infrared counterparts and can be classified as either deeply embedded objects or as starless cores if B30 members. In the former case, two of them (LB08 and LB31) show internal luminosity upper limits consistent with Very Low Luminosity objects, while we do not have enough information for LB10. In the starless core scenario, and taking into account the estimated masses from ALMA and the APEX/LABOCA cores, we estimate final masses for the central objects in the substellar domain, so they could be classified as pre-BD core candidates. According to the turbulent fragmentation scenario, the three ALMA pre-BD core candidates should be gravitationally stable based on APEX/LABOCA data. However, this result is not consistent with the presence of compact sources inside the cores, indicative of on-going collapse. As an alternative scenario we propose that these cores could be the result of on-going gravitational contraction. Indeed, we have verified that their estimated masses are consistent with the ones expected within an ALMA beam for a r −2 density profile, which is typical for a collapsing core. Conclusions. ALMA observations have allowed us to detect very low-mass compact sources within three APEX/LABOCA cores. Future observations will help us to unveil their true nature.

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“…1 from Reid et al (1988). Considering the beam major axis (∼0.9 ), we derive relative positional accuracies between 0.2 for SNR of 4.6 (LB31) and ∼5 mas for a SNR of 176 (LB14).…”

Section: Alma Observationsmentioning

confidence: 96%

A search for pre- and proto-brown dwarfs in the dark cloud Barnard 30 with ALMA

Huélamo

Gregorio-Monsalvo

Palau

et al. 2016

A&A

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“…3. The position uncertainty of the maser features is a function of both the synthesized beam θ 22 GHz and of the signal-to-noise ratio (SNR) measured at each channel of the spectrum; this is ∆θ = 0.45 θ 22GHz S NR (Reid et al 1988). The peak flux of both, the strongest and one of the weakest spectral features in Fig 2, as well as the rms value measured at the source position in a line-free channel (rms=1.02 × 10 −2 Jy/beam) were used in order to estimate the SNR.…”

Section: High-velocity H 2 O Maser Emissionmentioning

confidence: 99%

Deep into the Water Fountains

Pérez-Sánchez

Tafoya

López

et al. 2017

A&A

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Context. The formation of large-scale (hundreds to few thousands of AU) bipolar structures in the circumstellar envelopes (CSEs) of post-Asymptotic Giant Branch (post-AGB) stars is poorly understood. The shape of these structures, traced by emission from fast molecular outflows, suggests that the dynamics at the innermost regions of these CSEs does not depend only on the energy of the radiation field of the central star. Aims. Multi-frequency observations towards a group of post-AGB sources known as Water Fountain nebulae can help to constrain the nature of the mechanism responsible for the launching and collimation of the fast molecular outlflows traced by high-velocity features of H 2 O maser emission. Methods. Deep into the Water Fountains is an observational project based on the results of programs carried out with three telescope facilities: The Karl G. Jansky Very Large Array (JVLA), The Australia Telescope Compact Array (ATCA), and the Very Large Telescope (SINFONI-VLT). Results. Here we report the results of the observations towards the WF nebula IRAS 18043−2116: Detection of radio continuum emission in the frequency range 1.5 GHz -8.0 GHz; H 2 O maser spectral features and radio continuum emission detected at 22 GHz, and H 2 ro-vibrational emission lines detected at the near infrared. Conclusions. The high-velocity H 2 O maser spectral features, and the shock-excited H 2 emission detected could be produced in molecular layers which are swept up as a consequence of the propagation of a jet-driven wind. Using the derived H 2 column density, we estimated a molecular mass-loss rate of the order of 10 −9 M yr −1 . On the other hand, if the radio continuum flux detected is generated as a consequence of the propagation of a thermal radio jet, the mass-loss rate associated to the outflowing ionized material is of the order of 10 −5 M yr −1 . The presence of a rotating disk could be a plausible explanation for the mass-loss rates estimated.

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“…8, and the restored continuum maps (dual polarisation) have 1σ root mean square (rms) noise values of ∼0.2 mJy beam −1 . Hence, the statistical positional error, ∆θ stat θ maj θ min /(2S /N) (where θ maj and θ min are the major and minor axes of the beam; Reid et al 1988;Younger et al 2007), can be estimated to be about 0. 18/S 1.3 mm [ mJy beam −1 ], which is about 0.…”

Section: Source Samplementioning

confidence: 99%

(Sub)millimetre interferometric imaging of a sample of COSMOS/AzTEC submillimetre galaxies

Miettinen

Smolčić

Novak

et al. 2015

A&A

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We used the Plateau de Bure Interferometer (PdBI) to map a sample of 15 submillimetre galaxies (SMGs) in the COSMOS field at the wavelength of 1.3 mm. The target SMGs were originally discovered in the James Clerk Maxwell Telescope (JCMT)/AzTEC 1.1 mm continuum survey at S/N 1.1 mm = 4−4.5. This paper presents, for the first time, interferometric millimetre-wavelength observations of these sources. The angular resolution of our observations, ∼1. 8, allowed us to accurately determine the positions of the target SMGs. Using a detection threshold of S/N 1.3 mm > 4.5 regardless of multiwavelength counterpart association, and 4 < S/N 1.3 mm ≤ 4.5 if a multiwavelength counterpart within 1. 5 is also present, the total number of detections in our survey is 22. The most significant PdBI detection of S/N 1.3 mm = 10.3 is towards AzTEC19. Three of our detected SMGs (AzTEC21, 27, and 28; which corresponds to 20%) are marginally resolved at our angular resolution, and these sources are found to have elongated or clumpy morphologies and/or multiple components. Using optical to near-infrared photometric redshifts, available spectroscopic redshifts, and redshifts estimated from the radio-to-submm spectral index we infer a median redshift ofz = 3.20 ± 0.25 for our sample. To study the overall multiplicity and redshift distribution of flux-limited samples of SMGs we combined these sources with the 15 brightest JCMT/AzTEC SMGs detected at 1.1 mm, AzTEC1−15, and studied previously. This constitutes a complete, flux-and S/N-limited 1.1-mm selected sample. We find that the median redshift for the 15 brightest JCMT/AzTEC SMGs (z = 3.05 ± 0.44) is consistent with that for AzTEC16−30. This conforms to recent observational findings that SMGs do not exhibit any significant trend between the redshift and (sub)mm flux density. For the combined AzTEC1−30 sample we derive a median redshift ofz = 3.17 ± 0.27, consistent with previous results based on mm-selected samples. We further infer that within the combined AzTEC1−30 sample ∼25 ± 9% of sources separate into multiple components.

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The distance to the center of the Galaxy - H2O maser proper motions in Sagittarius B2(N)

Cited by 216 publications

References 0 publications

A search for pre- and proto-brown dwarfs in the dark cloud Barnard 30 with ALMA

A search for pre- and proto-brown dwarfs in the dark cloud Barnard 30 with ALMA

Deep into the Water Fountains

(Sub)millimetre interferometric imaging of a sample of COSMOS/AzTEC submillimetre galaxies

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