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Register a new userA comparison of the radio and optical time-evolution of HH~1 and 2
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We present a comparison between the time-evolution over the past $sim 20$ years of the radio continuum and H$alpha$ emission of HH~1 and 2. We find that the radio continuum and the H$alpha$ emission of both objects show very similar trends, with HH~1 becoming fainter and HH~2 brightening quite considerably (about a factor of 2). We also find that the $F_{rm Halpha}/F_{ff}$ (H$alpha$ to free-free continuum) ratio of HH~1 and 2 has higher values than the ones typically found in planetary nebulae (PNe) which we interpret as an indication that the H$alpha$ and free-free emission of HH~1/2 is produced in emitting regions with lower temperatures ($sim 2000$~K) than the emission of PNe (with $sim 10^4$~K).
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We present high angular resolution, high sensitivity 8.46 GHz (3.6 cm) radio continuum observations made toward the core of the HH~92 outflow with the Very Large Array in 2002-2003 and with the Expanded Very Large Array in 2011. We detect a group of three compact sources distributed in a region 2$$ in extension and discuss their nature. We conclude that one of the objects (VLA 1) is the exciting source of the giant outflow associated with HH~92. In the case of HH~34 we present new 43.3 GHz (7 mm) observations that reveal the presence of a structure associated with the exciting source and elongated perpendicular to the highly collimated optical jet in the region. We propose that this 7 mm source is a circumstellar disk with radius of $sim$80 AU and mass of $sim$0.21 $M_odot$.
We present an analysis of four epochs of H$alpha$ and [S II] $lambdalambda$ 6716/6731 HST images of HH 1. For determining proper motions we explore a new method based on analysis of spatially degraded images obtained convolving the images with wavelet functions of chosen widths. With this procedure we are able to generate maps of proper motion velocities along and across the outflow axis, as well as (angularly integrated) proper motion velocity distributions. From the four available epochs, we find the time evolution of the velocities, intensities and spatial distribution of the line emission. We find that over the last two decades HH 1 shows a clear acceleration. Also, the H$alpha$ and [S II] intensities have first dropped, and then recovered in the more recent (2014) images. Finally, we show a comparison between the two available HST epochs of [O III] $lambda$ 5007 (1994 and 2014), in which we see a clear drop in the value of the [O III]/H$alpha$ ratio.
We have analyzed four epochs of H$alpha$ and [S~II] HST images of the HH~1/2 outflow (covering a time interval from 1994 to 2014) to determine proper motions and emission line fluxes of the knots of HH~2. We find that our new proper motions agree surprisingly well with the motions measured by Herbig & Jones (1981), although there is partial evidence for a slight deceleration of the motion of the HH~2 knots from 1945 to 2014. We also measure the time-variability of the H$alpha$ intensities and the [S~II]/H$alpha$ line ratios, and find that knots H and A have the largest intensity variabilities (in $1994to 2014$). Knot H (which now dominates the HH~2 emission) has strengthened substantially, while keeping an approximately constant [S~II]/H$alpha$ ratio. Knot A has dramatically faded, and at the same time has had a substantial increase in its [S~II]/H$alpha$ ratio. Possible interpretations of these results are discussed.
(abridged) The HH 80/81/80N jet extends from the HH 80 object to the recently discovered Source 34 and has a total projected jet size of 10.3 pc, constituting the largest collimated radio-jet system known so far. It is powered by IRAS 18162-2048 associated with a massive young stellar object. We report 6 cm JVLA observations that, compared with previous 6 cm VLA observations carried out in 1989, allow us to derive proper motions of the HH 80, HH 81 and HH 80N radio knots located about 2.5 pc away in projection from the powering source. For the first time, we measure proper motions of the optically obscured HH 80N object providing evidence that HH 81, 80 and 80N are associated with the same radio-jet. We derived tangential velocities of these HH objects between 260 and 350 km/s, significantly lower than those for the radio knots of the jet close to the powering source (600-1400 km/s) derived in a previous work, suggesting that the jet material is slowing down due to a strong interaction with the ambient medium. The HH 80 and HH 80N emission at 6 cm is, at least in part, probably synchrotron radiation produced by relativistic electrons in a magnetic field of 1 mG. If these electrons are accelerated in a reverse adiabatic shock, we estimate a jet total density of $lesssim1000$ cm$^{-3}$. All these features are consistent with a jet emanating from a high mass protostar and make evident its capability of accelerating particles up to relativistic velocities.
We present subarcsecond angular resolution observations carried out with the Submillimeter Array (SMA) at 880 $mu$m centered at the B0-type protostar GGD27~MM1, the driving source of the parsec scale HH 80-81 jet. We constrain its polarized continuum emission to be $lesssim0.8%$ at this wavelength. Its submm spectrum is dominated by sulfur-bearing species tracing a rotating disk--like structure (SO and SO$_2$ isotopologues mainly), but also shows HCN-bearing and CH$_3$OH lines, which trace the disk and the outflow cavity walls excavated by the HH 80-81 jet. The presence of many sulfurated lines could indicate the presence of shocked gas at the disks centrifugal barrier or that MM1 is a hot core at an evolved stage. The resolved SO$_2$ emission traces very well the disk kinematics and we fit the SMA observations using a thin-disk Keplerian model, which gives the inclination (47$^{circ}$), the inner ($lesssim170$ AU) and outer ($sim950-1300$~AU) radii and the disks rotation velocity (3.4 km s$^{-1}$ at a putative radius of 1700 AU). We roughly estimate a protostellar dynamical mass of 4-18msun. MM2 and WMC cores show, comparatively, an almost empty spectra suggesting that they are associated with extended emission detected in previous low-angular resolution observations, and therefore indicating youth (MM2) or the presence of a less massive object (WMC).
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