اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe time evolution of HH~2 from four epochs of HST images
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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.
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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 wavele
t 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 present new H$alpha$ and H$beta$ images of the HH~1/2 system, and we find that the H$alpha$/H$beta$ ratio has high values in ridges along the leading edges of the HH~1 bow shock and of the brighter condensations of HH~2. These ridges have H$alpha$
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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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HH 223 is a knotty, wiggling nebular emission of ~30 length found in the L723 star-forming region. It lies projected onto the largest blueshifted lobe of the cuadrupolar CO outflow powered by a low-mass YSO system embedded in the core of L723. We ana
lysed the physical conditions and kinematics along HH 223 with the aim of disentangling whether the emission arises from shock-excited, supersonic gas characteristic of a stellar jet, or is only tracing the wall cavity excavated by the CO outflow. We performed long-slit optical spectroscopy along HH 223, crossing all the bright knots (A to E) and part of the low-brightness emission nebula (F filament). One spectrum of each knot, suitable to characterize the nature of its emission, was obtained. The physical conditions and the radial velocity of the HH 223 emission along the slits were also sampled at smaller scale (0.6) than the knot sizes. {The spectra of all the HH 223 knots appear as those of the intermediate/high excitation Herbig-Haro objects. The emission is supersonic, with blueshifted peak velocities ranging from -60 to -130 km/s. Reliable variations in the kinematics and physical conditions at smaller scale that the knot sizes are also found. The properties of the HH 223 emission derived from the spectroscopy confirm the HH nature of the object, the supersonic optical outflow most probably also being powered by the YSOs embedded in the L723 core.
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