Rosario Lopez

Ammonia observations of outflow regions

Observations of the (J,K) = (1,1) ammonia transition toward the suspected exciting sources of 12 regions with molecular or optical outflows are presented. In nine of these regions, ammonia emission was detected and mapped. The spatial coincidence of the high-density gas in the proposed exciting sources in five of the mapped regions supports the identification as exciting sources. A new location is proposed for the outflow exciting sources of L1524 (Haro 6-10) and HH 38,43. Also, in L1448, a radio continuum source and an unusually strong H2O maser coinciding with the maximum ammonia emission is detected. It is proposed that this region is the site of very recent star formation. 73 refs.

GRB 060121: Implications of a Short-/Intermediate-Duration γ-Ray Burst at High Redshift

Since the discovery of the first short-population γ-ray burst (GRB) afterglows in 2005, the handful of observed events have been found to be embedded in nearby (z 102). A photometric redshift for this event places the progenitor at a most probable redshift of z = 4.6, with a less probable scenario of z = 1.7. In either case, GRB 060121 could be the farthermost short-population GRB detected to date and implies an isotropic-equivalent energy release in gamma rays comparable to that seen in long-population bursts. We discuss the implications of the released energy on the nature of the progenitor. These results suggest that GRB 060121 may belong to a family of energetic short-population events, lying at z > 1 and whose optical afterglows would outshine their host galaxies, unlike the first short GRBs observed in 2005. The possibility of GRB 060121 being an intermediate-duration burst is also discussed.

The molecular cores in the L1287, AFGL 5142, and IRAS 20126 + 4104 regions

The NH 3 (J, K)=(1, 1) and (2, 2) line emission was mapped toward three regions with molecular outflows, L1287, AFGL 5142, and IRAS 20126+4104, using the Effelsberg 100 m telescope. Additional C 18 O (J=2→1) and CS (J=3→2) observations of L1287 were carried out with the IRAM 30 m telescope. For the three regions, the high-density molecular core, as traced by the ammonia emission, peaks very close to the position of the proposed powering sources of the outflows. In AFGL 5142 we flavor the radio continuum source proposed by Torrelles et al. (1992b) as the powering source of the outflow. The molecular cores best resolved by the telescope beam are elongated in a direction perpendicular to the outflow axis

A double radio source at the center of the outflow in L723

We report the detection of a double radio source at the center of the L723 outflow complex. Whether the four-lobe structure of the outflow constitutes a single or two independent bipolar outflows is a matter of discussion. Our detection of two radio continuum sources, separated ∼ 15″, is suggestive of two outflows with two independent exciting sources

INFRARED AND OPTICAL POLARIMETRY AROUND THE LOW-MASS STAR-FORMING REGION NGC 1333 IRAS 4A

We performed J- and R-band linear polarimetry with the 4.2 m William Herschel Telescope at the Observatorio del Roque de los Muchachos and with the 1.6 m telescope at the Observatorio do Pico dos Dias, respectively, to derive the magnetic field geometry of the diffuse molecular cloud surrounding the embedded protostellar system NGC 1333 IRAS 4A. We obtained interstellar polarization data for about three dozen stars. The distribution of polarization position angles has low dispersion and suggests the existence of an ordered magnetic field component at physical scales larger than the protostar. Some of the observed stars present intrinsic polarization and evidence of being young stellar objects. The estimated mean orientation of the interstellar magnetic field as derived from these data is almost perpendicular to the main direction of the magnetic field associated with the dense molecular envelope around IRAS 4A. Since the distribution of the CO emission in NGC 1333 indicates that the diffuse molecular gas has a multi-layered structure, we suggest that the observed polarization position angles are caused by the superposed projection of different magnetic field components along the line of sight.

Dense gas and the nature of the outflows

We present the results of the observations of the (J, K) = (1, 1) and the (J, K) = (2, 2) inversion transitions of the NH3 molecule toward a large sample of 40 regions with molecular or optical outflows, using the 37 m radio telescope of the Haystack Observatory. We detected NH3 emission in 27 of the observed regions, which we mapped in 25 of them. Additionally, we searched for the 6(16)-5(23) H2O maser line toward six regions, detecting H2O maser emission in two of them, HH265 and AFGL 5173. We estimate the physical parameters of the regions mapped in NH3 and analyze for each particular region the distribution of high density gas and its relationship with the presence of young stellar objects. In particular, we identify the deflecting high-density clump of the HH270/110 jet. We were able to separate the NH3 emission from the L1641-S3 region into two overlapping clouds, one with signs of strong perturbation, probably associated with the driving source of the CO outflow, and a second, unperturbed clump, which is probably not associated with star formation. We systematically found that the position of the best candidate for the exciting source of the molecular outflow in each region is very close to an NH3 emission peak. From the global analysis of our data we find that in general the highest values of the line width are obtained for the regions with the highest values of mass and kinetic temperature. We also found a correlation between the nonthermal line width and the bolometric luminosity of the sources, and between the mass of the core and the bolometric luminosity. We confirm with a larger sample of regions the conclusion of Anglada et al. (1997) that the NH3 line emission is more intense toward molecular outflow sources than toward sources with optical outflow, suggesting a possible evolutionary scheme in which young stellar objects associated with molecular outflows progressively lose their neighboring high-density gas, weakening both the NH3 emission and the molecular outflow in the process, and making optical jets more easily detectable as the total amount of gas decreases.

The stellar population and complex structure of the bright-rimmed cloud IC 1396N

Context. IC 1396N is a bright-rimmed cloud associated with an intermediate-mass star-forming region, where a number of Herbig- Haro objects, H2 jet-like features, CO molecular outflows, and millimeter compact sources have been observed. Aims. We study the complex structure of the IC 1396N core and the molecular outflows detected in the region in detail and reveal the presence of additional YSOs inside this globule. Methods. We carried out a deep survey of the IC 1396N region in the J,H,Kbroadband filters and deep high-angular resolution observations in the H2 narrowband filter with NICS at the TNG telescope. The completeness limits in the 2MASS standard are Ks ∼ 17.5, H ∼ 18.5, and J ∼ 19.5. Results. A total of 736 sources have been detected in all three bands within the area where the JHKimages overlap. There are 128 sources detected only in HK � , 67 detected only in K � , and 79 detected only in JH. We found only a few objects exhibiting a near-infrared excess and no clear signs of clustering of sources towards the southern rim. In the case of triggered star formation in the southern rim of the globule, this could be very recent, because it is not shown through Near-Infrared imaging alone. The H2 emission is complex and knotty and shows a large number of molecular hydrogen features spread over the region, testifying to recent star- formation activity throughout the whole globule. This emission is resolved into several chains or groups of knots that sometimes show a jet-like morphology. The shocked cloudlet model scenario previously proposed to explain the V-shaped morphology of the CO molecular outflow powered by the intermediate-mass YSO BIMA 2 seems to be confirmed by the presence of H2 emission at the position of the deflecting western clump. New possible flows have been discovered in the globule, and some of them could be very long. In particular, the YSO BIMA 3 could be powering an old and poorly collimated outflow.

The transverse velocity and excitation structure of the HH 110 jet

We present long-slit spectroscopic observations of the HH 110 jet obtained with the 4.2 m William Herschel Telescope. We have obtained for the first time, spectra for slit positions along and across the jet axis (at the position of knots B, C, I, J and P) to search for the observational signatures of entrainment and turbulence by studying the kinematics and the exci- tation structure. We find that the HH 110 flow accelerates from a velocity of 35 km s −1 in knot A up to 110 km s −1 in knot P. We find some systematic trends for the variation of the emission line ratios along the jet. No clear trends for the variation of the radial velocity are seen across the width of the jet beam. The cross sections of the jet show complex radial velocity and line emission structures which differ quite strongly from each other.

HH 262: The Red Lobe of the L1551 IRS 5 Outflow

HH 262 is a group of emitting knots located approximately 35 to the northeast of the L1551 IRS 5 source. We present a detailed study of the kinematic properties of HH 262, based on proper-motion measurements and on high-resolution imaging Fabry-Perot observations in the [S II] 6717 A line. From these observations, we conclude that it indeed appears to be the case that HH 262 is associated with the red lobe of the L1551 IRS 5 outflow.

A new radial system of dark globules in Monoceros

Aims. We analyze the LBN 978 HII region in order to study the HII/molecular cloud interaction. Methods. We used the IAC-80 telescope to image the region with narrow-band filters and the Very Large Array to obtain a radio continuum map at 3.6 cm. We also used the DSS2 red images and the NRAO VLA Sky Survey at 20 cm. Results. We have discovered a new radial system of dark globules associated with the LBN 978 HII region, containing a group of at least eight cometary bright-rimmed globules with the same morphological type. The brightest source is also detected in the radio continuum. Analysis of optical and radio emission suggest that this object is photoionized by HD 47432, the central star of the LBN 978 HII region.