High-<i>J</i>CO emission in the Cepheus E protostellar outflow observed with SOFIA/GREAT

Gómez-Ruiz, Arturo I.; Leurini, S.; Codella, C.; Güsten, R.; Wyrowski, F.; Requeña-Torres, M. A.; Risacher, C.; Wampfler, S. F.

doi:10.1051/0004-6361/201218936

Cited by 20 publications

(21 citation statements)

References 18 publications

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“…The component that we identify a few km s −1 blueward of the systemic V lsr is kinematically distinct from the envelope (Table 2), but it apparently harbors gas that is similar in density and temperature. Our results are consistent with conditions found in other protostellar outflows (e.g., Giannini et al 2001;Moro-Martín et al 2001;Lefloch et al 2010;Yıldız et al 2010Yıldız et al , 2012Bjerkeli et al 2011;Gómez-Ruiz et al 2012). Specifically, CHESS spectra toward the L1157-B1 outflow reveal H 2 gas densities of ∼10 5 to a few 10 6 cm −3 and temperatures around 200 K (Codella et al 2012;Benedettini et al 2012;Lefloch et al 2010Lefloch et al , 2012.…”

Section: Outflow Gassupporting

confidence: 92%

“…The blue component observed in this work may in fact trace swept-up envelope material ( < ∼ 10 km s −1 from the systemic velocity) rather than fast outflowing gas that is farther separated from the parent envelope, see, e.g., Van der Tak et al (1999) for AFGL 2591, or Qiu et al (2011) andGómez-Ruiz et al (2012) for other protostars. Our outflow conditions are compatible with the temperature and density derived for the warmest of the three outflow components in L1157-B1, as found by Lefloch et al (2012).…”

Section: Outflow Gasmentioning

confidence: 83%

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The HIFI spectral survey of AFGL 2591 (CHESS)

Wiel

Pagani

Tak

et al. 2013

A&A

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Context. Linear rotor molecules such as CO, HCO+ and HCN are important probes of star-forming gas. For these species, temperatures of < ∼ 50 K are sufficient to produce emission lines that are observable from the ground at (sub)millimeter wavelengths. Molecular gas in the environment of massive protostellar objects, however, is known to reach temperatures of several hundred K. To probe this, space-based far-infrared observations are required. Aims. We aim to reveal the gas energetics in the circumstellar environment of the prototypical high-mass protostellar object AFGL 2591. Methods. Rotational spectral line signatures of CO species, HCO + , CS, HCN and HNC from a 490-1240 GHz survey with Herschel/HIFI, complemented by ground-based JCMT and IRAM 30 m spectra, cover transitions in the energy range (E up /k) between 5 K and ∼300 K. Selected frequency settings in the highest frequency HIFI bands (up to 1850 GHz) extend this range to 750 K for 12 C 16 O. The resolved spectral line profiles are used to separate and study various kinematic components. Observed line intensities are compared with a numerical model that calculates excitation balance and radiative transfer based on spherical geometry. Results. The line profiles show two emission components, the widest and bluest of which is attributed to an approaching outflow and the other to the envelope. We find evidence for progressively more redshifted and wider line profiles from the envelope gas with increasing energy level. This trend is qualitatively explained by residual outflow contribution picked up in the systematically decreasing beam size. Integrated line intensities for each species decrease as E up /k increases from < ∼ 50 to ∼700 K. The H 2 density and temperature of the outflow gas are constrained to ∼10 5 -10 6 cm −3 and 60-200 K. In addition, we derive a temperature between 9 and 17 K and N(H 2 ) ∼ 3 × 10 21 cm −2 for a known foreground cloud seen in absorption, and N(H 2 ) < ∼ 10 19 cm −2 for a second foreground component. Conclusions. Our spherical envelope model systematically underproduces observed line emission at E up /k > ∼ 150 K for all species. This indicates that warm gas should be added to the model and that the model's geometry should provide low optical depth pathways for line emission from this warm gas to escape, for example in the form of UV heated outflow cavity walls viewed at a favorable inclination angle. Physical and chemical conditions derived for the outflow gas are similar to those in the protostellar envelope, possibly indicating that the modest velocity ( < ∼ 10 km s −1 ) outflow component consists of recently swept-up gas.

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Section: Outflow Gassupporting

confidence: 92%

Section: Outflow Gasmentioning

confidence: 83%

The HIFI spectral survey of AFGL 2591 (CHESS)

Wiel

Pagani

Tak

et al. 2013

A&A

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“…3 and 4) or SiO (G11) line profiles, where a "plateau" or a "bump" can be seen between 20 and 40 km s −1 , very much resembling the bullets revealed in the CO (in e.g. Cep E, Gómez-Ruiz et al 2012) or water line profiles (in e.g. L1448-mm, Kristensen et al 2011).…”

Section: Constraining Shock Modelsmentioning

confidence: 62%

Impacts of pure shocks in the BHR71 bipolar outflow

Gusdorf

Riquelme

Anderl

et al. 2015

A&A

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Context. During the formation of a star, material is ejected along powerful jets that impact the ambient material. This outflow regulates star formation by e.g. inducing turbulence and heating the surrounding gas. Understanding the associated shocks is therefore essential to the study of star formation. Aims. We present comparisons of shock models with CO, H 2 , and SiO observations in a "pure" shock position in the BHR71 bipolar outflow. These comparisons provide an insight into the shock and pre-shock characteristics, and allow us to understand the energetic and chemical feedback of star formation on Galactic scales. Methods. New CO (J up = 16, 11, 7, 6, 4, 3) observations from the shocked regions with the SOFIA and APEX telescopes are presented and combined with earlier H 2 and SiO data (from the Spitzer and APEX telescopes). The integrated intensities are compared to a grid of models that were obtained from a magneto-hydrodynamical shock code, which calculates the dynamical and chemical structure of these regions combined with a radiative transfer module based on the "large velocity gradient" approximation. Results. The CO emission leads us to update the conclusions of our previous shock analysis: pre-shock densities of 10 4 cm −3 and shock velocities around 20−25 km s −1 are still constrained, but older ages are inferred (∼4000 years). Conclusions. We evaluate the contribution of shocks to the excitation of CO around forming stars. The SiO observations are compatible with a scenario where less than 4% of the pre-shock SiO belongs to the grain mantles. We infer outflow parameters: a mass of 1.8 × 10 −2 M was measured in our beam, in which a momentum of 0.4 M km s −1 is dissipated, corresponding to an energy of 4.2 × 10 43 erg. We analyse the energetics of the outflow species by species. Comparing our results with previous studies highlights their dependence on the method: H 2 observations only are not sufficient to evaluate the mass of outflows.

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“…The receiver was tuned to the frequency of the CO lines J = 13-12 at 1496.923 GHz and J = 16-15 at 1841.346 GHz, respectively, during the Cycle 1 SOFIA flight on 2 November 2013. The emission of the CO line J = 12-11 at 1381.995 GHz was observed towards the same position in July 2011 during Basic Science flights (Gomez-Ruiz et al 2012).…”

Section: Sofiamentioning

confidence: 74%

The structure of the Cepheus E protostellar outflow: The jet, the bowshock, and the cavity

Leflóch

Gusdorf

Codella

et al. 2015

A&A

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Context. Protostellar outflows are a crucial ingredient of the star-formation process. However, the physical conditions in the warm outflowing gas are still poorly known. Aims. We present a multi-transition, high spectral resolution CO study of the outflow of the intermediate-mass Class 0 protostar Cep E-mm. The goal is to determine the structure of the outflow and to constrain the physical conditions of the various components in order to understand the origin of the mass-loss phenomenon. Methods. We have observed the J = 12-11, J = 13-12, and J = 16-15 CO lines at high spectral resolution with SOFIA/GREAT and the J = 5-4, J = 9-8, and J = 14-13 CO lines with HIFI/Herschel towards the position of the terminal bowshock HH377 in the southern outflow lobe. These observations were complemented with maps of CO transitions obtained with the IRAM 30 m telescope (J = 1-0, 2-1), the Plateau de Bure interferometer (J = 2-1), and the James Clerk Maxwell Telescope (J = 3-2, 4-3). Results. We identify three main components in the protostellar outflow: the jet, the cavity, and the bowshock, with a typical size of 1.7 × 21 , 4.5 , and 22 × 10 , respectively. In the jet, the emission from the low-J CO lines is dominated by a gas layer at T kin = 80-100 K, column density N(CO) = 9 × 10 16 cm −2 , and density n(H 2 ) = (0.5−1) × 10 5 cm −3 ; the emission of the high-J CO lines arises from a warmer (T kin = 400-750 K), denser (n(H 2 ) = (0.5−1) × 10 6 cm −3 ), lower column density (N(CO) = 1.5 × 10 16 cm −2 ) gas component. Similarly, in the outflow cavity, two components are detected: the emission of the low-J lines is dominated by a gas layer of column density N(CO) = 7 × 10 17 cm −2 at T kin = 55-85 K and density in the range (1−8) × 10 5 cm −3 ; the emission of the high-J lines is dominated by a hot, denser gas layer with T kin = 500-1500 K, n(H 2 ) = (1−5) × 10 6 cm −3 , and N(CO) = 6 × 10 16 cm −2 . A temperature gradient as a function of the velocity is found in the high-excitation gas component. In the terminal bowshock HH377, we detect gas of moderate excitation, with a temperature in the range T kin ≈ 400-500 K, density n(H 2 ) (1−2) × 10 6 cm −3 and column density N(CO) = 10 17 cm −2 . The amounts of momentum carried away in the jet and in the entrained ambient medium are similar. Comparison with time-dependent shock models shows that the hot gas emission in the jet is well accounted for by a magnetized shock with an age of 220-740 yr propagating at 20-30 km s −1 in a medium of density n(H 2 ) = (0.5−1) × 10 5 cm −3 , consistent with that of the bulk material. Conclusions. The Cep E protostellar outflow appears to be a convincing case of jet bowshock driven outflow. Our observations trace the recent impact of the protostellar jet into the ambient cloud, produing a non-stationary magnetized shock, which drives the formation of an outflow cavity.

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High-JCO emission in the Cepheus E protostellar outflow observed with SOFIA/GREAT

Cited by 20 publications

References 18 publications

The HIFI spectral survey of AFGL 2591 (CHESS)

The HIFI spectral survey of AFGL 2591 (CHESS)

Impacts of pure shocks in the BHR71 bipolar outflow

The structure of the Cepheus E protostellar outflow: The jet, the bowshock, and the cavity

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