4,333 research outputs found

    High Resolution Observations of the Massive Protostar in IRAS18566+0408

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    We report 3 mm continuum, CH3CN(5-4) and 13CS(2-1) line observations with CARMA, in conjunction with 6 and 1.3 cm continuum VLA data, and 12 and 25 micron broadband data from the Subaru Telescope toward the massive proto-star IRAS18566+0408. The VLA data resolve the ionized jet into 4 components aligned in the E-W direction. Radio components A, C, and D have flat cm SEDs indicative of optically thin emission from ionized gas, and component B has a spectral index alpha = 1.0, and a decreasing size with frequency proportional to frequency to the -0.5 power. Emission from the CARMA 3 mm continuum, and from the 13CS(2-1), and CH3CN(5-4) spectral lines is compact (i.e. < 6700 AU), and peaks near the position of VLA cm source, component B. Analysis of these lines indicates hot, and dense molecular gas, typical for HMCs. Our Subaru telescope observations detect a single compact source, coincident with radio component B, demonstrating that most of the energy in IRAS18566+0408 originates from a region of size < 2400 AU. We also present UKIRT near-infrared archival data for IRAS18566+0408 which show extended K-band emission along the jet direction. We detect an E-W velocity shift of about 10 km/sec over the HMC in the CH3CN lines possibly tracing the interface of the ionized jet with the surrounding core gas. Our data demonstrate the presence of an ionized jet at the base of the molecular outflow, and support the hypothesis that massive protostars with O-type luminosity form with a mechanism similar to lower mass stars

    Long-term Variability of H2_2CO Masers in Star-forming Regions

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    We present results of a multi-epoch monitoring program on variability of 6‚ÄČ\,cm formaldehyde (H2_2CO) masers in the massive star forming region NGC‚ÄČ\,7538‚ÄČ\,IRS‚ÄČ\,1 from 2008 to 2015 conducted with the GBT, WSRT, and VLA. We found that the similar variability behaviors of the two formaldehyde maser velocity components in NGC‚ÄČ\,7538‚ÄČ\,IRS‚ÄČ\,1 (which was pointed out by Araya and collaborators in 2007) have continued. The possibility that the variability is caused by changes in the maser amplification path in regions with similar morphology and kinematics is discussed. We also observed 12.2‚ÄČ\,GHz methanol and 22.2‚ÄČ\,GHz water masers toward NGC‚ÄČ\,7538‚ÄČ\,IRS‚ÄČ\,1. The brightest maser components of CH3_3OH and H2_2O species show a decrease in flux density as a function of time. The brightest H2_2CO maser component also shows a decrease in flux density and has a similar LSR velocity to the brightest H2_2O and 12.2‚ÄČ\,GHz CH3_3OH masers. The line parameters of radio recombination lines and the 20.17 and 20.97‚ÄČ\,GHz CH3_3OH transitions in NGC‚ÄČ\,7538‚ÄČ\,IRS‚ÄČ\,1 are also reported. In addition, we observed five other 6‚ÄČ\,cm formaldehyde maser regions. We found no evidence of significant variability of the 6‚ÄČ\,cm masers in these regions with respect to previous observations, the only possible exception being the maser in G29.96‚ąí-0.02. All six sources were also observed in the H213_2^{13}CO isotopologue transition of the 6‚ÄČ\,cm H2_2CO line; H213_2^{13}CO absorption was detected in five of the sources. Estimated column density ratios [H212_2^{12}CO]/[H213_2^{13}CO] are reported.Comment: 29 pages, 9 figure

    Discovery of 6.035GHz Hydroxyl Maser Flares in IRAS18566+0408

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    We report the discovery of 6.035GHz hydroxyl (OH) maser flares toward the massive star forming region IRAS18566+0408 (G37.55+0.20), which is the only region known to show periodic formaldehyde (4.8 GHz H2CO) and methanol (6.7 GHz CH3OH) maser flares. The observations were conducted between October 2008 and January 2010 with the 305m Arecibo Telescope in Puerto Rico. We detected two flare events, one in March 2009, and one in September to November 2009. The OH maser flares are not simultaneous with the H2CO flares, but may be correlated with CH3OH flares from a component at corresponding velocities. A possible correlated variability of OH and CH3OH masers in IRAS18566+0408 is consistent with a common excitation mechanism (IR pumping) as predicted by theory.Comment: Accepted for publication in the Astrophysical Journa

    Broadband VLA Spectral Line Survey of a Sample of Ionized Jet Candidates

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    The study of the interaction between ionized jets, molecular outflows and their environments is critical to understanding high-mass star formation, especially because jets and outflows are thought to be key in the transfer of angular momentum outwards from accretion disks. We report a low-spectral resolution VLA survey for hydrogen radio recombination lines, OH, NH3_3, and CH3_3OH lines toward a sample of 58 high-mass star forming regions that contain numerous ionized jet candidates. The observations are from a survey designed to detect radio continuum; the novel aspect of this work is to search for spectral lines in broadband VLA data (we provide the script developed in this work to facilitate exploration of other datasets). We report detection of 25‚ÄČ\,GHz CH3_3OH transitions toward ten sources; five of them also show NH3_3 emission. We found that most of the sources detected in CH3_3OH and NH3_3 have been classified as ionized jets or jet candidates and that the emission lines are coincident with, or very near (‚Č≤0.1\lesssim 0.1 pc) these sources, hence, these molecular lines could be used as probes of the environment near the launching site of jets/outflows. No radio recombination lines were detected, but we found that the RMS noise of stacked spectra decreases following the radiometer equation. Therefore, detecting radio recombination lines in a sample of brighter free-free continuum sources should be possible. This work demonstrates the potential of broadband VLA continuum observations as low-resolution spectral line scans.Comment: 38 pages, 19 figures. Accepted for publication in The Astrophysical Journal Supplement Serie

    Evaluation of two toothbrushes prescriptions on the removal of plaque in patients with fixed orthodontic appliances

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    Indexaci√≥n: Web of Science; ScieloLa aparatolog√≠a empleada en los tratamientos de ortodoncia, favorece la retenci√≥n de placa bacteriana y dificulta su eliminaci√≥n por parte del paciente, aumentando el riesgo de desarrollar caries, manchas blancas y enfermedad periodontal. Diferentes cepillos dentales se han desarrollado para facilitar la mantenci√≥n de una adecuada higiene oral en estos pacientes, sin embargo, se ha observado que los cepillos comunmente indicados (cepillo ortod√≥ncico mas cepillo unipenacho), no siempre son bien manejados y dif√≠cilmente se usan ambos. El cepillo Cross Action Pro-Salud¬ģ, se ha presentado como una alternativa simple de usar y de transportar, por ser un √ļnico cepillo que combina las caracteristicas de los dos cepillos comunmente recomendados. Para evaluar la efectividad de este cepillo, en comparaci√≥n con la prescripci√≥n convencional, se evaluaron 2 grupos, de 23 pacientes cada uno, portadores de aparatolog√≠a fija. Un grupo utiliz√≥ la prescripci√≥n habitual y un segundo grupo utiliz√≥ cepillo Cross Action Pro-Salud¬ģ, por un per√≠odo de 45 d√≠as. Los indices de higiene de O`leary, de placa en brackets y gingival modificado fueron registrados al inicio y 45 d√≠as despu√©s del uso diario de los cepillos antes mencionados. Se utiliz√≥ test-t para comparar los resultados obtenidos y se determin√≥ que se produjo una disminuci√≥n significativa en los tres indices de higiene, no existiendo diferencias en los resultados obtenidos entre ambas prescripciones. El cepillo Oral-B Cross-Action Pro-Salud¬ģ es una alternativa recomendable, ya que permite eliminar efectivamente la placa bacteriana en pacientes ortod√≥nticos, y al ser un √ļnico cepillo, facilita y acorta el tiempo de cepillado.Orthodontic fixed appliances include elements that allow the accumulation of bacterial plaque, making tooth brushing more difficult and increasing the risk of developing caries, white spot lesions, and periodontal disease. Several toothbrushes designs have been developed to facilitate oral hygiene in orthodontic patients; however, it has been observed that most patients do not take enough time to brush using adequately both commonly prescribed toothbrushes (Oral-B End-Tufted¬ģ and Oral-B Orthodontic¬ģ brushes). Oral B Cross Action Pro-Health¬ģ has been presented as an alternative, easier to use and to transport. To assess the effectiveness of Cross Action Pro-Health¬ģ versus commonly prescribed toothbrushes, two randomly assigned groups of 23 orthodontic patients each, were evaluated. One group of patients used commonly prescribed toothbrushes and the second group used Cross Action Pro-Health¬ģ. O`Leary, modified gingival and Bracket plaque index were measured before and 45 days after the daily use of the two mentioned toothbrushes prescriptions. T-test was used to detect statistically significant differences among the brushes for each index. The results demonstrated a significant reduction of the three indexes with the daily use of Cross Action Pro-Health¬ģ and no differences were found versus commonly used prescription. Orthodontic patients may benefit from the use of a single brush prescription (Cross Action Pro-Health¬ģ), because effective plaque removal can be achieved easier and faster.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0719-01072012000300002&nrm=is

    Weak and Compact Radio Emission in Early High-Mass Star Forming Regions: II. The Nature of the Radio Sources

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    In this study we analyze 70 radio continuum sources associated with dust clumps and considered to be candidates for the earliest stages of high-mass star formation. The detection of these sources was reported by Rosero et al. (2016), who found most of them to show weak (<{\scriptstyle <}1 mJy) and compact (<‚ÄČ{\scriptstyle <}\,0.6‚Ä≤‚Ä≤^{\prime \prime}) radio emission. Herein, we used the observed parameters of these sources to investigate the origin of the radio continuum emission. We found that at least ‚ąľ30%\sim 30\% of these radio detections are most likely ionized jets associated with high-mass protostars, but for the most compact sources we cannot discard the scenario that they represent pressure-confined HII regions. This result is highly relevant for recent theoretical models based on core accretion that predict the first stages of ionization from high-mass stars to be in the form of jets. Additionally, we found that properties such as the radio luminosity as a function of the bolometric luminosity of ionized jets from low and high-mass stars are extremely well-correlated. Our data improve upon previous studies by providing further evidence of a common origin for jets independently of luminosity.Comment: Accepted for publication in the Ap
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