HCOOCH3 as a probe of temperature and structure of Orion-KL

We studied the O-bearing molecule HCOOCH3 to characterize the physical conditions of the different molecular source components in Orion-KL. We identify 28 methyl formate emission peaks throughout the 50" field of observations. The two strongest peaks are in the Compact Ridge (MF1) and in the SouthWest of the Hot Core (MF2). Spectral confusion is still prevailing as half of the expected transitions are blended over the region. Assuming that the transitions are thermalized, we derive the temperature at the five main emission peaks. At the MF1 position we find a temperature of 80K in a 1.8"x0.8" beam size and 120K on a larger scale (3.6" x2.2"), suggesting an external source of heating, whereas the temperature is about 130K at the MF2 position on both scales. Transitions of HCOOCH3 in vt=1 are detected as well and the good agreement of the positions on the rotational diagrams between the vt=0 and the vt=1 transitions suggests a similar temperature. The velocity of the gas is between 7.5 and 8.0km/s depending on the positions and column density peaks vary from 1.6x10^16 to 1.6x10^17cm^-2. A second velocity component is observed around 9-10 km/s in a North-South structure stretching from the Compact Ridge up to the BN object; this component is warmer at the MF1 peak. The two other C2H4O2 isomers are not detected and the derived upper limit for the column density is <3x10^14cm^-2 for glycolaldehyde and <2x10^15cm^-2 for acetic acid. From the 223GHz continuum map, we identify several dust clumps with associated gas masses in the range 0.8 to 5.8Msun. Assuming that the HCOOCH3 is spatially distributed as the dust, we find relative abundances of HCOOCH3 in the range <0.1x10^-8 to 5.2x10^-8. We suggest a relation between the methyl formate distribution and shocks as traced by 2.12 mum H2 emission.Comment: Accepted for publication in A&

A Proper Motion Study of the Haro 6-10 Outflow: Evidence for a Subarcsecond Binary

We present single-dish and VLBI observations of an outburst of water maser emission from the young binary system Haro 6-10. Haro 6-10 lies in the Taurus molecular cloud and contains a visible T Tauri star with an infrared companion 1.3" north. Using the Very Long Baseline Array, we obtained five observations spanning 3 months and derived absolute positions for 20 distinct maser spots. Three of the masers can be traced over 3 or more epochs, enabling us to extract absolute proper motions and tangential velocities. We deduce that the masers represent one side of a bipolar outflow that lies nearly in the plane of the sky with an opening angle of ~45\deg. They are located within 50 mas of the southern component of the binary, the visible T Tauri star Haro 6-10S. The mean position angle on the sky of the maser proper motions (~220\deg) suggests they are related to the previously observed giant Herbig-Haro (HH) flow which includes HH410, HH411, HH412, and HH184A-E. A previously observed HH jet and extended radio continuum emission (mean position angle of ~190\deg) must also originate in the vicinity of Haro6-10S and represent a second, distinct outflow in this region. We propose that a yet unobserved companion within 150 mas of Haro6-10S is responsible for the giant HH/maser outflow while the visible star is associated with the HH jet. Despite the presence of H_2 emission in the spectrum of the northern component of the binary, Haro6-10N, none of outflows/jets can be tied directly to this young stellar object

CH2D+, the Search for the Holy Grail

CH2D+, the singly deuterated counterpart of CH3+, offers an alternative way to mediate formation of deuterated species at temperatures of several tens of K, as compared to the release of deuterated species from grains. We report a longstanding observational search for this molecular ion, whose rotational spectroscopy is not yet completely secure. We summarize the main spectroscopic properties of this molecule and discuss the chemical network leading to the formation of CH2D+, with explicit account of the ortho/para forms of H2, H3+ and CH3+. Astrochemical models support the presence of this molecular ion in moderately warm environments at a marginal level.Comment: 25 pages, 6 Figures Accepted in Journal of Physical Chemistry A. "Oka Festschrift: Celebrating 45 years of Astrochemistry

ALMA and VLA Observations: Evidence for Ongoing Low-mass Star Formation near Sgr A*

Using the VLA, we recently detected a large number of protoplanetary disk (proplyd) candidates lying within a couple of light years of the massive black hole Sgr A*. The bow-shock appearance of proplyd candidates point toward the young massive stars located near Sgr A*. Similar to Orion proplyds, the strong UV radiation from the cluster of massive stars at the Galactic center is expected to photoevaporate and photoionize the circumstellar disks around young, low mass stars, thus allowing detection of the ionized outflows from the photoionized layer surrounding cool and dense gaseous disks. To confirm this picture, ALMA observations detect millimeter emission at 226 GHz from five proplyd candidates that had been detected at 44 and 34 GHz with the VLA. We present the derived disk masses for four sources as a function of the assumed dust temperature. The mass of protoplanetary disks from cool dust emission ranges between 0.03 -- 0.05 solar mass. These estimates are consistent with the disk masses found in star forming sites in the Galaxy. These measurements show the presence of on-going star formation with the implication that gas clouds can survive near Sgr A* and the relative importance of high vs low-mass star formation in the strong tidal and radiation fields of the Galactic center.Comment: 13 pages, 3 figures, MNRAS (in press

Time-Resolved AU-Scale Jets Traced by Masers in the IRAS 4A/B Regions of NGC1333

We present results of VLBI observations of the water masers associated with IRAS 4A and IRAS 4B in the NGC 1333 star-forming region taken in four epochs over a two month period. Both objects have been classified as extremely young sources and each source is known to be a multiple system. Using the Very Long Baseline Array, we detected 35 masers in Epoch I, 40 masers in Epoch II, 35 in Epoch III, and 24 in Epoch IV. Only one identified source in each system associates with these masers. These data are used to calculate proper motions for the masers and trace the jet outflows within 100 AU of IRAS 4A2 and IRAS 4BW. In IRAS 4A2 there are two groups of masers, one near the systemic cloud velocity and one red-shifted. They expand linearly away from each other at velocities of 53 km/s. In IRAS 4BW, masers are observed in two groups that are blue-shifted and red-shifted relative to the cloud velocity. They form complex linear structures with a thickness of 3 mas (1 AU at a distance of 320 pc) that expand linearly away from each other at velocities of 78 km/s. Neither of the jet outflows traced by the maser groups align with the larger scale outflows. We suggest the presence of unresolved companions to both IRAS 4A2 and 4BW.Comment: Accepted by Ap

Tourism and final wish making: the discourse of terminal illness and travel

This paper identifies a new discourse about tourism, that of final wish making. The website communications of charitable foundations whose dedicated purpose is to grant final wishes for adults with a terminal illness and their families were examined using critical discourse analysis. Specifically, the aim of this study was to understand how these charitable organisations construct, communicate and mediate meanings around terminal illness and travel for these individuals. Our study found that, promoted as a final wish in one’s life, tourism is framed as a transformational concept that is beneficial in the imminent time before death, as a legacy for life, and after death. Our analysis indicated implications around the memory-making potential of tourism and the differential power relations between final wish organisers and vulnerable individuals with a terminal illness. The paper calls for further research exploring the marginalisation of the terminally ill through tourism, but equally the potential of tourism to include the most vulnerable tourists in their final days