L. F. Rodriguez

The triple radio continuum source in serpens : the birth of a Herbig-Haro system ?

VLA observations of the triple radio continuum source in Serpens have revealed its extraordinary characteristics. While it is associated with a star-forming region, its outer components exhibit nonthermal spectra and large proper motions. Here, we present the results of high-sensitivity, multifrequency VLA radio continuum observations of this source

Detection of radio continuum emission from Herbig-Haro objects 1 and 2 and from their central exciting source

The region in Orion containing HH 1 and HH 2 was observed with the VLA at 20, 6, and 2 cm on several occasions from 1981 to 1984. At lower resolution, four continuum sources were detected. Two of these sources coincide positionally with HH 1 and HH 2. At 6 cm and higher resolution, HH 1 is resolved into at least two components. The emission is probably bremsstrahlung originating in the same region where the visible line emission is produced. This is the first detection of radio continuum from classic Herbig-Haro objects. At a position closely centered between HH 1 and HH 2, an object that can be interpreted as the energy source of the system was detected. The central source spectrum is S(nu) of about nu to the alpha power, where alpha = 0.4 + or - 0.2, suggesting a stellar wind. Finally, the fourth radio continuum source coincides positionally with an H2O maser and is probably excited by an independent star. There is evidence of time variability in its radio flux. No emission was detected from the Cohen-Schwartz (1979) star at the 0.1 mJy level.

The exciting source of the bipolar outflow in L1448

A fast (+ or - 70 km/s), highly collimated CO bipolar outflow has been recently detected in the L1448 molecular cloud. No optical or infrared object has been found near the center of the outflow, implying a bolometric luminosity less than 3 solar luminosities for the exciting source. The VLA detected, at 2-cm wavelength, a radio continuum source at the center of this outflow. This radio source may be the exciting source of the bipolar outflow. The spectral index of the main component is alpha of about 0.2, similar to that expected for a thermal jet. The second component has a spectral index of alpha of about 1.0, consistent with that of a partially thick H II region. 18 refs.

Radio continuum from the powering sources of the RNO 43, Haro 4-255 FIR, B 335, and PV Cephei outflows and from the Herbig-Haro object 32 A

A sensitive VLA search for 3.6 cm continuum emission from the central regions of eight outflows is reported. Continuum sources in RNO 43, Haro 4-255 FIR, B335, and PV Cephei are detected, that are probably associated with the powering sources of these bipolar outflows. For objects with low bolometric luminosity (L(bol) ≤ 100 L ⊙ ), a marginal correlation is found between the momentum rate in the molecular outflow and the centimeter continuum luminosity

Radio continuum emission from knots in the DG Tauri jet

Context. HH 158, the jet from the young star DG Tau, is one of the few sources of its type where jet knots have been detected at optical and X-ray wavelengths. Aims. We aim to search for radio knots to compare them with the optical and X-ray knots. We also aim to model the emission from the radio knots. Methods. We analyzed archive data and also obtained new Very Large Array observations of this source, as well as an optical image to measure the present position of the knots. We furthermore modeled the radio emission from the knots in terms of shocks in a jet with intrinsically time-dependent ejection velocities. Results. We detected radio knots in the 1996.98 and 2009.62 VLA data. These radio knots are, within error, coincident with optical knots. We also modeled satisfactorily the observed radio flux densities as shock features from a jet with intrinsic variability. All observed radio, optical, and X-ray knot positions can be intepreted as four successive knots, ejected with a period of 4.80 years and traveling away from the source with a velocity of 198 km s −1 in the plane of the sky. Conclusions. The radio and optical knots are spatially correlated and our model can explain the observed radio flux densities. However, the X-ray knots do not appear to have optical or radio counterparts and their nature remains poorly understood.

A search for possible interactions between ejections from GRS 1915+105 and the surrounding interstellar medium

We have observed an extended region surrounding the rst discovered galactic superluminal source GRS 1915+105, seeking evidence of interaction between the relativistic ejecta of that object and the interstel- lar medium. We nd two radio sources axisymmetrically aligned along the sub-arcsecond relativistic ejecta of GRS 1915+105 and roughly 17 0 distant from it, which coincide with the luminous IRAS sources 19124+1106 and 19132+1035. We have observed these sources at centimeter (VLA), millimeter (IRAM 30 m), and infrared (ISO, UKIRT, ESO/MPI 2.2 m) wavelengths in both line and continuum emission. At centimeter wavelengths a non-thermal jet-like feature aligned along the outflow axis is located adjacent to the inner edge of the southern source. Strong density enhancements are found in the millimeter tracers CO and H 13 CO + at the positions of both sources and some of the morphology is reminiscent of shock-like interactions; however, linewidths are narrow. At infrared wavelengths strong hydrogen recombination lines and weak lines of molecular hydrogen are observed at the southern source. We discuss these results as possible evidence of the sought-after interaction, both in terms of the regions undergoing ongoing shock-heating and in terms of them being locations of shock-induced star for- mation. The evidence for each of these is inconclusive. Millimeter line mapping of a portion of W 50 where the relativistic jets of the X-ray binary SS 433 interact with the interstellar medium shows roughly similar morphology as GRS 1915+105, suggesting that the phenomena observed at the IRAS sources may not be unusual for such a long distance interaction.

VLA observations of high-velocity H I associated with the Herbig-Haro objects 7-11

The continuum and H I emission from the HH 7-11 region has been observed with the VLA at 21 cm. A total of 58 sources are detected in the region in the continuum, most of them background objects. Several of these sources are almost certainly associated with the HH 7-11 region, and their nature is discussed. At the velocity of the ambient cloud, H I emission regions around SVS 3 and BD + 30 549 deg are detected which are the illuminating stars of NGC 1333, the reflection nebula to the northeast of HH 7-11. It is suggested that these zones are photodissociated H I regions. The H I emission at + or - 20 km/s maps two apparently independent bipolar outflows associated with HH 7-11 and with HH 12. At higher velocities, the high-velocity bipolar H I emission associated with HH 7-11 can still be detected. The 40 km/s redshifted H I emission is more compact than the 20 km/s redshifted H I emission, as expected for a decelerating outflow. 39 refs.

Mass outflow in star formation regions: Cepheus A

The velocity extents, the spatial distributions, and the masses, deduced from CO observations, are very different for the red and blue outflows in Cepheus A. These properties can be modeled by placing the source of outflow amidst an anisotropic density distribution. The red outflow expands in the direction of lower density while the blue outflow encounters greater resistance as it expands toward the density peak in the cloud, as delineated by the NH/sub 3/ emission. The ratio of the masses and the total mass swept up by the outflow can be estimated by a simple model. The observed self-absorption in the line profile is probably due to absorption by the ambient cloud against a hot and optically thick component in the red outlow. We conclude that the appearance of an outflow is strongly affected by the environment in which it is embedded. In particular, the outflow in Cepheus A may not be very well collimated. The general attributes of the model are shown to be applicable to other regions of outflow. The apparently bipolar nature of outflows in star formation regions is discussed.

RADIO JETS AND DISKS IN THE INTERMEDIATE-MASS STAR-FORMING REGION NGC2071IR

We report the results of simultaneous radio continuum and water maser observations toward the NGC 2071IR star-forming region, carried out with the VLA in its A configuration. We detect continuum emission toward the infrared sources IRS 1 and IRS 3 at 1.3 and 3.6 cm. In addition, a new continuum source, VLA 1, is also detected at both wavelengths, which is located between IRS 1 and IRS 3. IRS 1 breaks up into three continuum peaks (IRS 1E, 1C, and 1W), aligned in the east-west direction (P.A. = 100°). IRS 1 is the central source, while the sources E and W seem to be condensations ejected by IRS 1. In the same way, IRS 3 is also forming a triple system (IRS 3N, 3C and 3S), which is elongated in the northeast-southwest direction and the condensations, IRS 3N and IRS 3S, are symmetrically located along the major axis. Based on the morphology and the continuum emission, we suggest that both IRS 1 and IRS 3 are radio jets, which have ejected condensations into the interstellar medium. Moreover, IRS 1 and IRS 3 seem to be the driving sources of the large-scale outflows observed in H2 and CO, respectively. In addition, we also detected water emission toward the systems IRS 1, IRS 3, and the new source VLA 1. Based on the spatial-kinematic distribution of the water masers, we find evidence that the water masers are tracing part of circumstellar disks around IRS 1C and IRS 3C. Moreover, we estimate that the sources IRS 1C and IRS 3C have central masses of ~5 and ~1 M ☉, respectively. We conclude that the radio continuum and water maser emission are tracing disk-YSO-outflow systems toward IRS 1 and IRS 3, which are low- and intermediate-mass young stellar objects, respectively.

Galactic black hole binaries: Multifrequency connections

We review the recent multifrequency studies of galactic black hole binaries, aiming at revealing the underlying emission processes and physical properties in these systems. The optical and infrared observations are important for determining their system parameters, such as the companion star type, orbital period and separation, inclination angle and the black hole mass. The radio observations are useful for studying high energy electron acceleration process, jet formation and transport. X-ray observations can be used to probe the inner accretion disk region in order to understand the fundamental physics of the accretion disk in the strongest gravitational field and the properties of the black hole. Future higher sensitivity and better resolution instrumentation will be needed to answer the many fundamental questions that have arisen.