Netherlands Institute for Space Research

About: Netherlands Institute for Space Research is a facility organization based out in Utrecht, Netherlands. It is known for research contribution in the topics: Galaxy & Neutron star. The organization has 737 authors who have published 3026 publications receiving 106632 citations. The organization is also known as: SRON & Space Research Organisation Netherlands.

APEX-CHAMP+ high-J CO observations of low-mass young stellar objects - I. The HH 46 envelope and outflow

Abstract: Context. The spectacular outflow of HH 46/47 is driven by HH 46 IRS 1, an embedded Class I Young Stellar Object (YSO). Although much is known about this region from extensive optical and infrared observations, the properties of its protostellar envelope and molecular outflow are poorly constrained. Aims. Our aim is to characterize the size, mass, density and temperature profiles of the protostellar envelope of HH 46 IRS 1 and its surrounding cloud material as well as the effect the outflow has on its environment. Methods. The newly commisioned CHAMP(+) and LABOCA arrays on the APEX telescope, combined with lower frequency line receivers, are used to obtain a large (5' x 5', 0.6 x 0.6 pc) continuum map and smaller (80 '' x 80 '', 36 000 x 36 000 AU) heterodyne maps in various isotopologues of CO and HCO+. The high-J lines of CO (6-5 and 7-6) and its isotopologues together with [C I] 2-1, observed with CHAMP(+), are used to probe the warm molecular gas in the inner few hundred AU and in the outflowing gas. The data are interpreted with continuum and line radiative transfer models. Results. Broad outflow wings are seen in CO low-and high-J lines at several positions, constraining the gas temperatures to a constant value of similar to 100 K along the red outflow axis and to similar to 60 K for the blue outflow. The derived outflow mass is of order 0.4-0.8 M-circle dot, significantly higher than previously found. The bulk of the strong high-J CO line emission has a surprisingly narrow width, however, even at outflow positions. These lines cannot be fit by a passively heated model of the HH 46 IRS envelope. We propose that it originates from photon heating of the outflow cavity walls by ultraviolet photons originating in outflow shocks and the accretion disk boundary layers. At the position of the bow shock itself, the UV photons are energetic enough to dissociate CO. The envelope mass of similar to 5 M-circle dot is strongly concentrated towards HH 46 IRS with a density power law of -1.8. Conclusions. The fast mapping speed offered by CHAMP(+) allows the use of high-J CO lines and their isotopes to generate new insights into the physics of the interplay between the molecular outflow and protostellar envelope around low-mass protostars. The UV radiation inferred from the high-J CO and [C I] data will affect the chemistry of other species.

Multiwavelength campaign on Mrk 509 III. The 600 ks RGS spectrum: unravelling the inner region of an AGN

Abstract: We present the results of our 600 ks RGS observation as part of the multiwavelength campaign on Mrk 509. The very high quality of the spectrum allows us to investigate the ionized outflow with an unprecedented accuracy due to the long exposure and the use of the RGS multipointing mode. We detect multiple absorption lines from the interstellar medium and from the ionized absorber in Mrk 509. A number of emission components are also detected, including broad emission lines consistent with an origin in the broad line region, the narrow O VII forbidden emission line and also (narrow) radiative recombination continua. The ionized absorber consists of two velocity components (upsilon = -13 +/- 11 km s(-1) and upsilon = -319 +/- 14 km s(-1)), which both are consistent with earlier results, including UV data. There is another tentative component outflowing at high velocity, -770 +/- 109 km s(-1), which is only seen in a few highly ionized absorption lines. The outflow shows discrete ionization components, spanning four orders of magnitude in ionization parameter. Due to the excellent statistics of our spectrum, we demonstrate for the first time that the outflow in Mrk 509 in the important range of log. between 1-3 cannot be described by a smooth, continuous absorption measure distribution, but instead shows two strong, discrete peaks. At the highest and lowest ionization parameters we cannot differentiate smooth and discrete components.

Hydrides in young stellar objects: Radiation tracers in a protostar-disk-outflow system

Abstract: Context. Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays. Aims. We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass star formation. Methods. W3 IRS5 was observed by HIFI on the Herschel Space Observatory with deep integration (� 2500 s) in 8 spectral regions. Results. The target lines including CH, NH, H3O + , and the new molecules SH + ,H 2O + ,a nd OH + are detected. The H2O + and OH + J = 1−0 lines are found mostly in absorption, but also appear to exhibit weak emission (P-Cyg-like). Emission requires high density, thus originates most likely near the protostar. This is corroborated by the absence of line shifts relative to the young stellar object (YSO). In addition, H2O + and OH + also contain strong absorption components at a velocity shifted relative to W3 IRS5, which are attributed to foreground clouds. Conclusions. The molecular column densities derived from observations correlate well with the predictions of a model that assumes the main emission region is in outflow walls, heated and irradiated by protostellar UV radiation.

HDO abundance in the envelope of the solar-type protostar IRAS 16293–2422

Abstract: We present IRAM 30m and JCMT observations of HDO lines towards the solar-type protostar IRAS 16293-2422. Five HDO transitions have been detected on-source, and two were unfruitfully searched for towards a bright spot of the outflow of IRAS 16293-2422. We interpret the data by means of the Ceccarelli, Hollenbach and Tielens (1996) model, and derive the HDO abundance in the warm inner and cold outer parts of the envelope. The emission is well explained by a jump model, with an inner abundance of 1e-7 and an outer abundance lower than 1e-9 (3 sigma). This result is in favor of HDO enhancement due to ice evaporation from the grains in theinner envelope. The deuteration ratio HDO/H2O is found to be f_in=3% and f_out < 0.2% (3 sigma) in the inner and outer envelope respectively and therefore, the fractionation also undergoes a jump in the inner part of the envelope. These results are consistent with the formation of water in the gas phase during the cold prestellar core phase and storage of the molecules on the grains, but do not explain why observations of H2O ices consistently derive a H2O ice abundance of several 1e-5 to 1e-4, some two orders of magnitude larger than the gas phase abundance of water in the hot core around IRAS 16293-2422.

Chemical abundances in an AGN environment : X-Ray/UV campaign on the Markarian 279 outflow

Abstract: We present the first reliable determination of chemical abundances in an active galactic nucleus (AGN) outflow The abundances are extracted from the deep and simultaneous Far Ultraviolet Spectroscopic Explorer (FUSE) and Hubble Space Telescope (HST) STIS observations of Mrk 279 This data set is exceptional for its high signal-to-noise ratio, unblended doublet troughs, and little Galactic absorption contamination These attributes allow us to solve for the velocity-dependent covering fraction and therefore obtain reliable column densities for many ionic species For the first time, we have enough such column densities to simultaneously determine the ionization equilibrium and abundances in the flow Our analysis uses the full spectral information embedded in these high-resolution data Slicing a given trough into many independent outflow elements yields the extra constraints needed for a physically meaningful abundance determination We find that relative to solar, the abundances in the Mrk 279 outflow are (linear scaling) carbon 22 ± 07, nitrogen 35 ± 11, and oxygen 16 ± 08 Our UV-based photoionization and abundance results are in good agreement with the independent analysis of the simultaneous Mrk 279 X-ray spectra This is the best agreement between the UV and X-ray analyses of the same outflow to date