Discovery of near infrared jets in the Galactic microquasar GRS 1915+105

The Galactic microquasar GRS 1915+105 ejects collimated bipolar jets of plasma which appear to move faster-than-light, or 'superluminally', on the plane of the sky. We present the first non-radio frequency jet detections and polarization measurements from a microquasar. On 18 July 1995, the near infrared (NIR) jets had the same position angle as the radio jets and contained the bulk of the emitted jet energy. If the radiation is synchrotron, the emitting NIR electrons must have energies 100 times higher than those responsible for the radio emission. We call attention to an apparent mass scaling valid over a range of 10"8 which connects the jets in GRS 1915+105 with those from quasars powered by supermassive (M #approx# 10"9M_sun) black holes. Because GRS 1915+105 is in our galaxy, and hence 10"5 times closer than the quasars, it offers an unique opportunity to study the physics of ultra-relativistic jets. (orig.)SIGLEAvailable from TIB Hannover: RN 9303(349) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Kinematics of the ultracompact HII region W3(OH): constraints derived from high n radio recombination

We observed the ultracompact HII region W3(OH) with #approx# 6'' spatial resolution in the H66#alpha#, H76#alpha#, and H110#alpha# radio recombination lines with the goal of constraining its structure and kinematics via the lineshapes. We find that the H66#alpha# line has a LSR center velocity of -50.7#+-#0.3 km s"-"1 and FWHM of 36.0 #+-# 1.8 km s"-"1; the H76#alpha# line has a LSR center velocity of -50.3#+-#0.2 km s"-"1 and FWHM of 40.7#+-#2.1 km s"-"1; and the H110#alpha# line has a LSR center velocity of -63.1#+-#3.9 km s"-"1 and FWHM of 69.4#+-#16.2 km s"-"1. The H110#alpha# line profile is significantly impact broadened, and is the first detection of this phenomena in a compact or ultracompact HII region. The broadening is not as strong as simple modeling predicts, a discrepancy most likely due to clumpiness in the ionized gas. The linewidths and velocities best support and 'accelerated champagne flow' kinematic model. (orig.)Available from TIB Hannover: RN 9303(332) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

High angular resolution spectroscopic and polarimetric imaging of the Galactic center in the near-infrared

We present improved 0.15'' resolution K-band (2.2#mu#m) maps of the central 0.5 parsec of the Galaxy as well as, for the first time, 0.2'' J-band (1.25#mu#m) images, 0.2'' K-band polarimetry and 0.4'' images in the 2.058#mu#m He I emission and 2.29#mu#m CO bandhead absorption features. The new K-band maps reach K magnitudes of about 16 and resolve the previously found object at the position of the radio source Sgr A"*(R) into a small cluster of compact sources. With one exception, their polarizations are similar to other sources in its vicinity and thus are probably caused by anisotropic foreground dust extinction in the Galactic plane. The Sgr A"*(IR) complex does not exhibit any significant flux density variations at 2.2#mu#m on time scales of minutes or years. We therefore interpret Sgr A"*(IR) as a small local clustering of luminous stars (M_Kapprox-3) near/at the position of the compact radio source. The central IRS16 complex and the bright source IRS13 are dominated by bright, luminous HeI stars and confirm the cluster of about a dozen He I stars found at Krabbe et al. (1991). There are also a dozen of sources with K#<=#12.5 exhibiting CO-bandhead absorption within a radius of 10'' of Sgr A"*(IR). The drop in CO-bandhead strength found at Sellgren et al. (1990) thus is most likely not caused by the disappearance of CO sources but by additional presence of the bright early type stars. (orig.)Available from TIB Hannover: RN 9303(308) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Near infrared imaging spectroscopy of cD galaxy NGC1275

We present H and K band imaging spectroscopy of NGC 1275 taken with the MPE 3-D instrument which show an enormous variety of diagnostics which can be exploited to further constrain the star formation and excitation mechanisms in the galaxy's nucleus. These include H_2 lines from 1-0, 2-1, and 3-2 transitions, Br#gamma#, "1"2CO bandheads, [Fe II], He I, [Fe III], and Br#delta# lines. We match the observed spectra with synthetic spectra obtained by combining stellar, AGN and hot dust emission. At the nucleus, the infared light from stars is only 10% of that due to AGN and hot dust emission, whereas 1 kpc from the nucleus, the light is dominated by stars. The H_2 emission is strongly peaked at the nucleus, but shows broad, low level extensions. We attribute this geometry to two separate sources of ionization in NGC 1275: the AGN nucleus, which excites the vast majority of the radiation, and which produces the compact emission core seen in our maps, and the extended region of moderate star formation which excites the highly extended, weak H_2 envelope via shocks. The total H_2 line emission in H and K bands is equivalent to L_H_2#approx#8x10"4"0 erg s"-"1. The H_2 emission shows a rotation of 75#+-#15 km s"-"1 about the #approx#SW-NE axis at a distance of 1'' (#approx#350 pc) from the nucleus. The Br#gamma# emission is highly asymmetric both in line profile and in spatial distribution. The spatial elongation is coincident with the PA=160 angle of the Fanaroff-Riley type I radio lobes, suggesting that shocks from the jets produce star formation along their axis. The HeI_2_._0_6/Br#gamma# ratio suggests that the mean ionizing stars are late type O, although this depends on the nuclear AGN emission and several other factors. The [Fe II] emission dominates the H band spectrum and consists of a broad (1060 km s"-"1) as well as narrow (290 km s"-"1) component. The CO_s_p index shows a ''hole'' at the NGC 1275 nucleus due to the extra contributions of hot dust and AGN emission to the continuum. When the CO_s_p index is undiluted, the result is again consistent with an underlying K5III stellar population. The H_2 line-to-continuum map shows a tongue of emission extending #approx#3'' West of the nucleus, which is aligned with the CO emission ring seen in mm wave maps. (orig.)Available from TIB Hannover: RN 9303(348) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman