The gas-phase iron abundance in Herbig-Haro objects

Beck-Winchatz, Bernhard; Bohm, Karl‐Heinz; Noriega-Crespo, A.

doi:10.1086/133504

Cited by 11 publications

(16 citation statements)

References 26 publications

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“…In this case the estimate does not depend upon assumptions of the shock characteristics (velocity, pre-shock density, magnetic field intensity) but depends on the accuracy of the determinations of the gas parameters. Beck-Winchatz et al (1994 used this method to estimate Fe and Ni gas-phase abundance in HH jets. They found that Fe is not, or only partially, depleted in HH jets, while Ni is surprisingly over-abundant.…”

Section: Observational Estimates Of Calcium Gas-phase Abundance In Stmentioning

confidence: 99%

Physical structure and dust reprocessing in a sample of HH jets

Podio

Medves

Bacciotti

et al. 2009

A&A

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Context. Stellar jets are an essential ingredient of the star formation process and a wealth of information can be derived from their characteristic emission-line spectra. Aims. We investigate the physical structure and dust reprocessing in the shocks along the beam of a number of classical Herbig-Haro (HH) jets in the Orion and Lupus molecular clouds (HH 111, HH 1/2, HH 83, HH 24 M/A/E/C, and Sz68). Parameters describing plasma conditions, as well as dust content, are derived as a function of distance from the source and, for HH 111, of gas velocity. Methods. Spectral diagnostic techniques are applied to obtain the jet physical conditions (the electron and total density, n e and n H , the ionisation fraction, x e , and the temperature, T e ) from the ratios of selected forbidden lines. The presence of dust grains is investigated by estimating the gas-phase abundance of calcium with respect to its solar value. Results. We find the electron density varies between 0.05-4 × 10 3 cm −3 , the ionisation fraction x e from 0.01-0.7, the temperature ranges between 0.6-3 × 10 4 K, and the hydrogen density between 0.01-6 × 10 4 cm −3 . Interestingly, in the HH 111 jet, n e , x e , and T e peak in the high velocity interval (HVI) of the strongest working surfaces, confirming a prediction from shocks models. Calcium turns out to be depleted with respect to its solar value, but its gas-phase abundance is higher than estimates for the interstellar medium in Orion. The depletion is high (up to 80%) along the low-excited jets, while low or no depletion is measured in those jets which show higher excitation conditions. Moreover, for HH 111 the depletion is lower in the HVI of the fastest shock. Conclusions. Our results confirm the shock structure predicted by models and indicate that shocks occurring along jets, and presumably those present in the launch zone, only partially destroy dust grains and that the efficiency of dust reprocessing strongly depends on shock velocity. However, the high Ca gas-phase abundance estimated in some of the knots, is not well understood in terms of existing models of dust reprocessing in shocks, and indicates that the dust must have been partially reprocessed in the region where the flow originates.

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Section: Observational Estimates Of Calcium Gas-phase Abundance In Stmentioning

confidence: 99%

Physical structure and dust reprocessing in a sample of HH jets

Podio

Medves

Bacciotti

et al. 2009

A&A

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“…This method was first applied to HH objects by Beck-Winchatz et al (1994, using a large sample of op- Nisini et al (2002) proposed two other methods to measure the Fe gas phase abundance in young stellar jets, relying only on near-infrared lines. The first one involves the [Fe ] 1.257 µm/Paβ ratio, assuming that Paβ is emitted under case B recombination.…”

Section: Diagnostic Of Gas Phase Fe Abundancementioning

confidence: 99%

“…The method is simply an extension to the near-IR domain of that introduced by Beck-Winchatz et al (1994) in the optical range. As described above, it will yield a lower limit to the Fe/S ratio.…”

Section: Diagnostic Of Gas Phase Fe Abundancementioning

confidence: 99%

“…Extending the work of Nisini et al (2002) and Beck-Winchatz et al (1994), we first derive in Sect. 2 diagnostic diagrams that allow to constrain, independently of the heating process and ejection model, the electronic temperature and density as well as the Fe + /S + gas phase abundance ratio -a critical parameter to derive mass loss rates from [Fe ] line fluxes and to estimate the amount of depletion onto dust grains.…”

Section: Introductionmentioning

confidence: 99%

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Near-IR [$\ion{Fe}{ii}$] emission diagnostics applied to cold disk winds in young stars

Pesenti

Dougados

Cabrit

et al. 2003

A&A

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Abstract.We investigate the emissivity properties of the main near-IR transitions of the Fe + ion in the conditions prevailing in the inner regions of jets from young stars, based on a simplified 16-level atom model. We present new diagnostic diagrams involving prominent near-IR line ratios that allow us to constrain the electronic density, temperature, and Fe gas phase abundance ratio, independently of the heating process. Comparison with recent near-IR observations of a sample of HH objects indicates gas phase Fe abundances ranging from 15-50% up to 100% of the solar value (depending on the assumed temperature and on the HH object), in agreement with the moderate depletions previously derived from optical line ratios or shock models. Hence, it appears that Fe-bearing dust is efficiently destroyed in stellar jets. We then use our Fe cold disk wind model reproduces quite well the two velocity components observed at −100 and −300 km s −1 , although the high velocity component appears overestimated by a factor of 1.5 in the DG Tau jet. However, the model predicts too little emission at intermediate velocities and insufficient densities. Similar problems were encountered in previous model comparisons in the optical range with jets from T Tauri stars. Denser disk winds with stronger heating at the jet base, which have been invoked for optical jets, also appear needed in younger, embedded Class I jet sources.

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“…Refractory species such as Ca, Ni, Cr, and Fe are often locked onto dust grains, thus a strong depletion of their gas phase abundance is expected in the interstellar medium (ISM) (Savage & Sembach 1996). A few studies have investigated the gas phase abundance of Fe and Ni in HH jets (Beck-Winchatz et al 1994Mouri & Taniguchi 2000;Böhm & Matt 2001;Nisini et al 2002), and only recently the analysis has been extended to other refractory species such as Si, Ca, C, Cr, and Ti (Nisini et al 2005(Nisini et al , 2007Cabrit et al 2007;Podio et al 2006Podio et al , 2009Garcia Lopez et al 2008). These studies showed that the refractory species may be depleted by up to 90% in HH jets and molecular outflows, thus suggesting the presence of dust grains in the ejected material.…”

Section: Introductionmentioning

confidence: 99%

Tracing kinematical and physical asymmetries in the jet from DG Tauri B

Podio¹,

Eislöffel

Melnikov

et al. 2011

A&A

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Context. Jets from young stars can be highly asymmetric and have multiple velocity components. Aims. To clarify the origin of jet asymmetries and constrain the launch mechanism, we study as a test case the physical and kinematical structure of the prototypical asymmetric flow emitted by DG Tau B. Methods. The analysis of deep, high spectral resolution observations taken with the KECK telescope allows us to infer the properties and the spatial distribution of the velocity components in the two jet lobes. From selected line ratios we derive the gas physical conditions (the electron and total density, n e and n H , the ionisation fraction, x e , and the temperature, T e ), as a function of the distance from the source and the gas velocity. The presence of dust grains in the jet is investigated by estimating the gas-phase abundance of calcium with respect to its solar value. Results. The detected lines show broad velocity profiles at the base of the jet (up to ∼100 km s −1 ), where up to three velocity components are detected. At 5 from the source, however, only the denser and more excited high-velocity components survive and the lines are narrower (∼10-30 km s −1 ). The jet is strongly asymmetric in the velocity and in its physical structure. The red lobe, which is slower (∼140 km s −1 ) and more collimated (opening angle: α ∼ 3-4 • ), presents low ionisation fractions (x e ∼ 0.1-0.4) and temperatures (T e < 5 × 10 3 K), while the total density is up to ∼2.5 × 10 4 cm −3 . The blue lobe, faster (∼-320 km s −1 ) and less collimated (α ∼ 14 • ), is also less dense (n H < 10 4 cm −3 ), but highly excited (T e up to ∼5 × 10 4 K and x e up to 0.9). The estimated mass-loss rate turns out to be similar in the two lobes (∼6-8 × 10 −9 M yr −1 ), while the flux of the linear momentum is three times higher in the blue one (∼2.5 × 10 −7 M yr −1 km s −1 ). Calcium is strongly depleted with respect to its solar abundance, indicating that the jet contains dust grains. The depletion is lower for higher velocities, which is consistent with dust destruction by shocks. Conclusions. The similar mass-loss rate in the two lobes suggests that the ejection power is comparable on the two sides of the system, as expected from a magneto-centrifugal ejection mechanism, and that the observed asymmetries are caused by a different mass load and propagation properties in an inhomogeneous environment. The presence of dust grains implies that the jet is generated from a region of the disc extending beyond the dust sublimation radius.

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The gas-phase iron abundance in Herbig-Haro objects

Cited by 11 publications

References 26 publications

Physical structure and dust reprocessing in a sample of HH jets

Physical structure and dust reprocessing in a sample of HH jets

Near-IR [$\ion{Fe}{ii}$] emission diagnostics applied to cold disk winds in young stars

Tracing kinematical and physical asymmetries in the jet from DG Tauri B

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