ASTRONOMY AND ASTROPHYSICS Thermal H2O emission from the Herbig-Haro flow HH 54? (original) (raw)
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H2 observations of outflows from young stars
Analizamos observaciones del IR cercano recientes de jets Herbig-Haro (HH) y de flujos moleculares de protoestrellas muy jóvenes profundamente embebidas. Mediciones de movimiento propio y estudios espectroscópicos de baja y de alta resolución muestran la excitación y la cinemática de objetos individuales, que podrían interpretarse en términos de choques de proa de alta velocidad que barren y incorporan material del ambiente para formar flujos moleculares de "CO". Las propiedades observadas de muchos objetos puede explicarse razonablemente bien con modelos de choques de proa tipo "C" magnetizados, aunque choques del tipo "J" no puede excluirse del todo. Analizamos también nuevas observaciones echelle de las fuentes mismas de los flujos. Estos datos de H 2 muestran emisión de línea de velocidades intermedias y altas en la base del flujo (de menos de unas pocos cientos de unidades astronómicas de la fuente que lo impulsa) en la mayoría de las fuentes observadas. Las propiedades de estas regiones de líneas de emisión de hidrógeno molecular-o MHEL, por sus siglas en inglés-son similares a las regiones de líneas prohibidas (FEL, por sus siglas en inglés) hacia estrellas T Tauri.
Astronomy and Astrophysics, 2002
To search for further evidence of H2 line emission towards the central engines of Herbig-Haro (HH) flows we have obtained near-infrared Fabry-Perot images of eight Class I outflow sources (SVS 13 [HH 7-11], L 1551-IRS5, HH 26-IRS, HH 72-IRS, SSV 63E [HH 24C], SSV 63W [HH 24J], HH 34-IRS and HH 111-IRS) and two Class 0 sources (HH 24-MMS and HH 25-MMS). Elongated H2 emission (on scales of a few arcseconds) is detected from four of the Class I YSOs. These small-scale "jets" are associated with the base of more extended, parsec-scale HH outflows (and the "Molecular Hydrogen Emission Line" regions, or MHELs, discussed in Davis et al. 2001).
The Giant Herbig-Haro Flow HH 212 and Associated Star Formation
2019
The bipolar jet HH 212, among the finest collimated jets known, has so far been detected only in near-infrared H_2 emission. Here we present deep optical images that show two of the major bow shocks weakly detected in optical [SII] emission, as expected for a bona fide Herbig-Haro jet. We present widefield H_2 images which reveal two more bow shocks located symmetrically around the source and along the main jet axis. Additionally, examination of Spitzer 4.5 μm images reveals yet another bright bow shock further to the north along the jet axis; no corresponding bow shock is seen to the south. In total, the HH 212 flow has an extent of 1050 arcsec, corresponding to a projected dimension of 2.0 pc. HH 212 thus joins the growing group of parsec-scale Herbig-Haro jets. Proper motion measurements indicate a velocity of about 170 km/sec, highly symmetric around the source, with an uncertainty of ∼30 km/sec, suggesting a probable age of the giant HH 212 flow of about 7000 yr. The jet is dri...
Infrared Space Observatory Spectroscopy of HH 7–11 Flow and Its Redshifted Counterpart
The Astrophysical Journal, 2000
We have used the two spectrometers on the Infrared Space Observatory to observe the HH 7-11 flow, its red-shifted counterpart, and the candidate exciting source SVS 13, in the star formation region NGC 1333. We detect atomic ([Oi]63µm, [Oi]145µm, [Siii]34.8µm, [Cii]158µm) and molecular (H 2 , CO, H 2 O) lines at various positions along the bipolar flow.
Astronomy & Astrophysics, 2013
Context. Understanding the physical phenomena involved in the earlierst stages of protostellar evolution requires knowledge of the heating and cooling processes that occur in the surroundings of a young stellar object. Spatially resolved information from its constituent gas and dust provides the necessary constraints to distinguish between different theories of accretion energy dissipation into the envelope. Aims. Our aims are to quantify the far-infrared line emission from low-mass protostars and the contribution of different atomic and molecular species to the gas cooling budget, to determine the spatial extent of the emission, and to investigate the underlying excitation conditions. Analysis of the line cooling will help us characterize the evolution of the relevant physical processes as the protostar ages. Methods. Far-infrared Herschel-PACS spectra of 18 low-mass protostars of various luminosities and evolutionary stages are studied in the context of the WISH key program. For most targets, the spectra include many wavelength intervals selected to cover specific CO, H2O, OH, and atomic lines. For four targets the spectra span the entire 55-200 μm region. The PACS field-of-view covers ~47" with the resolution of 9.4". Results. Most of the protostars in our sample show strong atomic and molecular far-infrared emission. Water is detected in 17 out of 18 objects (except TMC1A), including 5 Class I sources. The high-excitation H2O 818-707 63.3 μm line (Eu/kB = 1071 K) is detected in 7 sources. CO transitions from J = 14-13 up to J = 49 - 48 are found and show two distinct temperature components on Boltzmann diagrams with rotational temperatures of ~350 K and ~700 K. H2O has typical excitation temperatures of ~150 K. Emission from both Class 0 and I sources is usually spatially extended along the outflow direction but with a pattern that depends on the species and the transition. In the extended sources, emission is stronger off source and extended on &≥10,000 AU scales; in the compact sample, more than half of the flux originates within 1000 AU of the protostar. The H2O line fluxes correlate strongly with those of the high-J CO lines, both for the full array and for the central position, as well as with the bolometric luminosity and envelope mass. They correlate less strongly with OH fluxes and not with [O I] fluxes. In contrast, [O I] and OH often peak together at the central position. Conclusions. The PACS data probe at least two physical components. The H2O and CO emission very likely arises in non-dissociative (irradiated) shocks along the outflow walls with a range of pre-shock densities. Some OH is also associated with this component, most likely resulting from H2O photodissociation. UV-heated gas contributes only a minor fraction to the CO emission observed by PACS, based on the strong correlation between the shock-dominated CO 24-23 line and the CO 14-13 line. [O I] and some of the OH emission probe dissociative shocks in the inner envelope. The total far-infrared cooling is dominated by H2O and CO, with the fraction contributed by [O I] increasing for Class I sources. Consistent with previous studies, the ratio of total far-infrared line emission over bolometric luminosity decreases with the evolutionary state.
Spectroscopy of molecular hydrogen in outflows from young stars
Astronomy and Astrophysics
We present new medium-resolution longslit spectra in the near-infrared and examine the excitation of molecular hydrogen across several outflows from young stars. In contrast to previous studies, in which the brightest patches in the flows were selected, we find evidence for variations in excitation with position within several sources.
High-resolution near-infrared observations of Herbig-Haro flows -- I. H2 imaging and proper motions
Monthly Notices of the Royal Astronomical Society, 2000
We present results of an H 2 proper motion study of three Herbig±Haro flows: HH 7±11, 25± 26 and 33/40. These are the first proper motion measurements for these objects in the nearinfrared, and are complementary to a velocity-resolved, echelle spectroscopy study of the H 2 line profile from these objects, presented in a companion paper (Paper II, this issue).
A New Look at Stellar Outflows: Spitzer Observations of the HH 46/47 System
The Astrophysical Journal Supplement Series, 2004
We present the Early Release Observations of the HH 46/47 system and HH 46 IRS 1 source, taken with the three instruments aboard the Spitzer Space Telescope. The optically invisible southwest lobe, driven by the HH 47C bow shock, is revealed in full detail by the Infrared Array Camera (IRAC) images and displays a ''loop''-like morphology. Both of the mid-infrared outflow lobes are narrower than those of CO flow. We believe that the combination of emission by H 2 rotational lines [S(11)-S(4)] and some atomic lines, which fall within the IRAC passbands, are responsible for the bulk of the observed emission, although contributions from the 3.3, 6.2, and 7.7 m polycyclic aromatic hydrocarbon emission bands cannot be ruled out. Weak spectral features corresponding to these emitters are present in the Infrared Spectrograph spectrum of the HH 47A bow shock. The spectrum of HH 46 IRS 1 shows remarkable similarities to those of high-mass protostars, which include the presence of H 2 O, CO 2 , CH 4 , and possibly NH 3 , CH 3 OH, and NH þ 4 ices. The high ice abundances and the lack of signs of thermal processing indicate that these ices in the envelope are well shielded from the powerful outflow and its cavity. Emission from the Bok globule at 24 m is detected and displays a similar structure to that observed at 8 m.
The Astrophysical Journal, 1997
We present new narrow-band near-infrared images together with K band spectra of highly collimated bipolar jets close to the IRAS 05487+0255 source. The jets are located at ∼ 50 ′′ West of the Herbig-Haro 110 outflow. The jets are not visible at optical wavelengths, and therefore, do not fall into the 'standard' Herbig-Haro object classification scheme. Nevertheless, they belong to an ever growing group of molecular hydrogen jets associated with YSOs which are optically undetected.