Recently it has become apparent that proto-stellar-like outflow activity
extends to the brown dwarf (BD) mass regime. While the presence of accretion
appears to be the common ingredient in all objects known to drive jets
fundamental questions remain unanswered. The more prominent being the exact
mechanism by which jets are launched, and whether this mechanism remains
universal among such a diversity of sources and scales. To address these
questions we have been investigating outflow activity in a sample of
protostellar objects that differ considerably in mass and mass accretion rate.
Central to this is our study of brown dwarf jets. To date Classical T Tauri
stars (CTTS) have offered us the best touchstone for decoding the launching
mechanism. Here we shall summarise what is understood so far of BD jets and the
important constraints observations can place on models. We will focus on the
comparison between jets driven by objects with central mass < 0.1M \odot and
those driven by CTTSs. In particular we wish to understand how the the ratio of
the mass outflow to accretion rate compares to what has been measured for
CTTSs.Comment: Proceedings of IAU meeting 275, "Jets at All Scales

Bacciotti

Barrado

Camenzind

Catherine Dougados

Chauvin

Comerón

Dougados

Emma Teresa Whelan

Fernández

Francesca Bacciotti

Gatti

Lada

Natta

Reipurth

Tom Ray

English

arXiv

Recently it has become apparent that proto-stellar-like outflow activity extends to the brown dwarf (BD) mass regime. While the presence of accretion appears to be the common ingredient in all objects known to drive jets fundamental questions remain unanswered. The more prominent being the exact mechanism by which jets are launched, and whether this mechanism remains universal among such a diversity of sources and scales. To address these questions we have been investigating outflow activity in a sample of protostellar objects that differ considerably in mass and mass accretion rate. Central to this is our study of brown dwarf jets. To date Classical T Tauri stars (CTTS) have offered us the best touchstone for decoding the launching mechanism. Here we shall summarise what is understood so far of BD jets and the important constraints observations can place on models. We will focus on the comparison between jets driven by objects with central mass <0.1M⊙ and those driven by CTTSs. In particular we wish to understand how the the ratio of the mass outflow to accretion rate compares to what has been measured for CTTSs

Whelan, Emma

Bacciotti, F.

Ray, T.P.

Dougados, C.

Maynooth EPrints and ETheses Archive

Brown dwarf jets: Investigating the universality of jet launching mechanisms at the lowest masses

AbstractRecently it has become apparent that proto-stellar-like outflow activity extends to the brown dwarf (BD) mass regime. While the presence of accretion appears to be the common ingredient in all objects known to drive jets fundamental questions remain unanswered. The more prominent being the exact mechanism by which jets are launched, and whether this mechanism remains universal among such a diversity of sources and scales. To address these questions we have been investigating outflow activity in a sample of protostellar objects that differ considerably in mass and mass accretion rate. Central to this is our study of brown dwarf jets. To date Classical T Tauri stars (CTTS) have offered us the best touchstone for decoding the launching mechanism. Here we shall summarise what is understood so far of BD jets and the important constraints observations can place on models. We will focus on the comparison between jets driven by objects with central mass &lt;0.1M⊙ and those driven by CTTSs. In particular we wish to understand how the the ratio of the mass outflow to accretion rate compares to what has been measured for CTTSs.</jats:p

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Proceedings of the International Astronomical Union

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Jets at all ScalesProceedings IAU Symposium No. 275, 2011G. E. Romero, R. A. Sunyaev & T. Belloni, eds.c© International Astronomical Union 2011doi:10.1017/S1743921310016467Brown dwarf jets: Investigating theuniversality of jet launching mechanisms atthe lowest massesEmma Teresa Whelan1 and Francesca Bacciotti2, and Tom Ray3, andCatherine Dougados11Laboratoire d’Astrophysique de Grenoble, UMR 5571, BP 53, 38041 Grenoble Cedex 09,Franceemail: whelane@obs.ujf-grenoble.fr2 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy,Box 515, SE-75120 Uppsala, Swedenemail: fran@arcetri.astro.it3Dublin Institute for Advanced Studies, Irelandemail: tr@cp.dias.ieAbstract. Recently it has become apparent that proto-stellar-like outflow activity extendsto the brown dwarf (BD) mass regime. While the presence of accretion appears to be thecommon ingredient in all objects known to drive jets fundamental questions remain unanswered.The more prominent being the exact mechanism by which jets are launched, and whether thismechanism remains universal among such a diversity of sources and scales. To address thesequestions we have been investigating outflow activity in a sample of protostellar objects thatdiffer considerably in mass and mass accretion rate. Central to this is our study of brown dwarfjets. To date Classical T Tauri stars (CTTS) have offered us the best touchstone for decodingthe launching mechanism. Here we shall summarise what is understood so far of BD jets andthe important constraints observations can place on models. We will focus on the comparisonbetween jets driven by objects with central mass < 0.1M and those driven by CTTSs. Inparticular we wish to understand how the the ratio of the mass outflow to accretion rate comparesto what has been measured for CTTSs.Keywords. stars: low-mass, brown dwarfs, mass loss, ISM: jets and outflows1. Brown Dwarf OutflowsJets from CTTSs are traditionally probed at forbidden emission line (FEL) wavelengthsand long-slit and integral field spectroscopic techniques have been hugely important intheir study (Dougados et al. 2000). That CTT-like outflows could be launched by activelyaccreting BDs was first suggested when high quality spectra revealed the presence of FELregions in the optical spectra of BDs known to be accretors (Ferna´ndez & Comero´n 2001).While the FEL regions were easily identified they were considerably fainter than thosedetected in the spectra of CTTSs and any extension in the form of an outflow was notapparent (Ferna´ndez & Comero´n 2001). Hence their origin in an outflow could not beestablished. As the most intense forbidden emission coincides with the critical densityregion it is currently challenging to directly resolve a BD outflow in FELs and this goalhas not yet been achieved. Our approach to this problem has been to obtain high qualityspectra using the UV-Visual Echelle Spectrometer (UVES) on the European SouthernObservatory’s (ESO) Very Large Telescope (VLT) and to recover the spatial offset in theregion of forbidden emission using spectro-astrometry (Whelan & Garcia 2008).396https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921310016467Downloaded from https://www.cambridge.org/core. Maynooth University, on 17 Sep 2018 at 14:03:28, subject to the Cambridge Core terms of use, available atBrown dwarf jets: launching mechanisms at the lowest masses 397To date we have observed 5 optical outflows driven by BDs (Table 1). While overallthese jets are T Tauri-like in nature each object has its own unique properties. ISO-Oph102 was the first BD confirmed to be driving a jet. Interesting follow-up observationswith the SMA conducted by Phan-Bao et al. (2008) also detected a molecular outflowdriven by this BD. The properties of the outflow agreed with what was observed in theoptical by Whelan et al. (2005). This is only one of a small number of objects (includingprotostellar objects) known to be driving both an optical jet and a molecular outflow.2MASS1207-3932 at only 24MJU P is the lowest mass galactic object known to drivea jet. The detection of a jet was first reported by Whelan et al. (2007) and follow-upobservations have constrained the position angle (PA) of the jet at ∼ 220◦. 2MASS1207-3932 is an intriguing object as it has a planetary mass companion which was imagedwith the VLT (Chauvin et al. 2005). Our recent observations show the jet PA to beapproximately perpendicular to the PA of the companion suggesting the presence ofcircumbinary structure (Whelan et al. 2010, in prep). This observation is relevant to theformation of the companion. In the case of LS-RCr A1 spectro-astrometry confirmedthat both the line-wings of the Hα line and the forbidden emission originated in a jet.What is interesting about this object is that while only blue-shifted forbidden emission isobserved both lobes of the outflow are detected in the Hα line. This is taken as evidenceof a dust hole in the disk of LS-RCr A1 which suggests the onset of planet-formingprocesses (Whelan et al. 2009). Finally we will mention the jet driven by ISO-ChaI217. We detected a bipolar outflow from this object however what was notable was thestrong asymmetry between the two lobes of the outflow. This asymmetry is revealedin the relative brightness of the two lobes (red-shifted lobe is brighter), the factor oftwo difference in radial velocity (the red-shifted lobe is faster) and the difference in theelectron density (again higher in the red lobe). Such asymmetries are common in jetsfrom low mass protostars and the observation of a marked asymmetry at such a lowmass (< 0.1M) supports the idea that BD outflow activity is scaled down from lowmass protostellar activity. Also note that although asymmetries are unexceptional, itis uncommon for the red-shifted lobe to be the brightest as some obscuration by theaccretion disk is assumed.2. Constraining ModelsStudies of BD outflows can offer constraints to both models of jet launching and BDformation. Current models describing the launching and collimation of protostellar jetspredict how various jet parameters, including the ratio of the mass outflow to accretionrate, scale with mass and mass accretion rate (M˙out/M˙acc). Thus we have identifiedM˙out/M˙acc as an important observational constraint and have thus begun the work ofmeasuring this for sub-stellar outflows. To date we have estimated M˙out/M˙acc for threeof the known BD outflows. This was derived using two methods. Method A is based onthe equationM˙out = µmH nH πr2J vJ (2.1)where ne , xe and thus nH are derived using the Bacciotti & Eisloffel (BE) technique(Bacciottiet al.1999). Reasonable estimates of the jet velocity vJ and jet radius rJ comefrom measured radial velocities and a previously derived relation between jet width anddistance. Method B is based on the observed luminosity L(line) of an optically thinline such as [SII] or [OI]. The mass of the flow M is derived using the equations ofHartiganet al.1995. M˙out is estimated as follows, M˙out = MVtan/ltan where nc , Vtan andltan are the critical density, outflow tangential velocity and the size of the aperture inhttps://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921310016467Downloaded from https://www.cambridge.org/core. Maynooth University, on 17 Sep 2018 at 14:03:28, subject to the Cambridge Core terms of use, available at398 E. T. Whelan et al.the plane of the sky. Table 2 compares the values derived for M˙out using both methodswith previously known estimates of M˙acc . What is clear from these results is that canbe stated at present is that the mass outflow and mass accretion rates are comparable.To further constrain their ratio the number of substellar outflows investigated must begreatly increased. It is also important to simultaneously derive the two rates and tobetter understand the sources of error in the various methods for estimating the massaccretion rate. See Whelan et al. (2009b) for further discussion of the methods used andthe results. We also plan to investigate the occurrence of episodic jets in the BD regimeand the frequency of molecular outflows. For low mass stars episodic jets are taken asevidence of variable accretion. If BDs jets are also found to episodic this will help todrive models of BD accretion activity. Projects to increase the sample of BD jets, furtherinvestigate M˙out/M˙acc and search for BD molecular outflows are currently underway.ReferencesBacciotti, F., Eislo¨ffel, J., & Ray, T. P. 1999, A&A, 350, 917Barrado y Navascue´s, D., Mohanty, S., & Jayawardhana, R. 2004, ApJ, 604, 284Camenzind, M. 2005, Memorie della Societa Astronomica Italiana, 76, 98Chauvin, G., Lagrange, A.-M., Dumas, C., Zuckerman, B., Mouillet, D., Song, I., Beuzit, J.-L.,& Lowrance, P. 2005, A&A, 438, L25Comero´n, F., Ferna´ndez, M., Baraffe, I., Neuha¨user, R., & Kaas, A. A. 2003, A&A, 406, 1001Dougados, C., Cabrit, S., Lavalley, C., & Me´nard, F. 2000, A&A, 357, L61Ferna´ndez, M. & Comero´n, F. 2001, A&A, 380, 264Gatti, T., Testi, L., Natta, A., Randich, S., & Muzerolle, J. 2006, A&A, 460, 547Hartigan, P., Edwards, S., & Ghandour, L. 1995, ApJ, 452, 736Herczeg, G. J., Cruz, K. L., & Hillenbrand, L. A. 2009, ApJ, 696, 1589Lada, C. J. 1987, Star Forming Regions, 115, 1Mohanty, S., Jayawardhana, R., & Basri, G. 2004, ApJ, 609, 885Mohanty, S., Jayawardhana, R. & Basri, G. 2005, ApJ, 626, 498Mohanty, S., Jayawardhana, R., Hue´lamo, N., & Mamajek, E. 2007, ApJ, 657, 1064Muzerolle, J., Luhman, K. L., Bricen˜o, C., Hartmann, L., & Calvet, N. 2005, ApJ, 625, 906Natta, A., Testi, L., Comero´n, F., Oliva, E., D’Antona, F., Baffa, C., Comoretto, G., & Gennari,S. 2002, A&A, 393, 597Natta, A., Testi, L., Muzerolle, J., Randich, S., Comero´n, F., & Persi, P. 2004, A&A, 424, 603Natta, A., Testi, L., & Randich, S. 2006, A&A, 452, 245Pascucci, I., Apai, D., Luhman, K., Henning, T., Bouwman, J., Meyer, M. R., Lahuis, F., &Natta, A. 2009, ApJ, 696, 143Phan-Bao, N., et al. 2008, ApJL, 689, L141Ray, T., Dougados, C., Bacciotti, F., Eislo¨ffel, J., & Chrysostomou, A. 2007, Protostars andPlanets V, 231Reipurth, B. & Bally, J. 2001, A&AR, 39, 403Scholz, A., & Jayawardhana, R. 2006, ApJ, 638, 1056Stahler, S. W. 1983, ApJ, 274, 822Whelan, E. T., Ray, T. P., Bacciotti, F., Natta, A., Testi, L., & Randich, S. 2005, Nature, 435,652Whelan, E. T., Ray, T. P., Bacciotti, F., & Jayawardhana, R. 2006, New Astronomy Review,49, 582Whelan, E. T., Ray, T. P., Randich, S., Bacciotti, F., Jayawardhana, R., Testi, L., Natta, A., &Mohanty, S. 2007, ApJL, 659, L45Whelan, E. & Garcia, P. 2008, Lecture Notes in Physics, Berlin Springer Verlag, 742, 123Whelan, E. T., Ray, T. P., & Bacciotti, F. 2009, ApJL, 691, L106Whelan, E. T., Ray, T. P., Podio, L., Bacciotti, F., & Randich, S. 2009, ApJ, 706, 1054https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921310016467Downloaded from https://www.cambridge.org/core. Maynooth University, on 17 Sep 2018 at 14:03:28, subject to the Cambridge Core terms of use, available atBrown dwarf jets: launching mechanisms at the lowest masses 399Source RA (J2000) Dec (J2000) Spectral Type Mass (MJ U P )ISO-ChaI 217 11 09 52.0 -76 39 12.0 M6.2 8012MASS1207-3932 12 07 33.4 -39 32 54.0 M8 242DENIS-P J160603.9-205644 16 06 03.90 -20 56 44.6 M7.5 403ISO-Oph 32 16 26 22.05 -24 44 37.5 M8 404ISO-Oph 102 16 27 06.58 -24 41 47.9 M6 604LS-RCr A1 19 01 33.7 -37 00 30.0 M6.5 35-725Table 1. The spectral type and predicted mass of the BD candidates investigated by us todate. All sources except DENIS-P J160603.9-205644 are found to drive outflows.Object M˙ou t (Myr−1 ) MethodLS-RCr A12.4 × 10−9 A6.1 × 10−10 B [OI]λ63002.0 × 10−10 B [SII]λ6731ISO-Oph 1021.7-11.8 × 10−10 B [SII]λ67311.4 × 10−9 CO molecular outflow6ISO-ChaI 217 Red flow3.1 × 10−10 B [SII]λ6731ISO-ChaI 217 Blue flow1.8 × 10−10 B [SII]λ6731Object M˙acc (Myr−1 ) MethodLS-RCr A12.8 × 10−10 CaII(λ8542)710−10 -10−9 Optical Veiling510−9 CaII(λ8662)810−10 Hα 10% width9ISO-Oph 10210−9 Hα 10% width104.3 × 10−10 J and K band spectra11ISO-ChaI 2171.0 × 10−10 Hα emission1Table 2. Measurements of M˙ou t and M˙acc for the objects studied to date.For the BDs in our sample M˙ou t is comparable to M˙acc .Table References: 1=Muzerolle et al. 2005, 2=Mohanty et al. 2007, 3=Mohanty et al. 2004,4=Natta et al. 2002 and 5=Barrado y Navascue´s et al. 2004, 6=Phan-Bao et al. (2008),7=Comero´n et al. 2003, 3=Barrado y Navascue´s et al. 2004, 8=Mohanty et al. 2005, 9=Scholz& Jayawardhana 2006, 10=Natta et al. 2004, 11=Natta et al. 2006, 8=Muzerolle et al. 2005https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921310016467Downloaded from https://www.cambridge.org/core. Maynooth University, on 17 Sep 2018 at 14:03:28, subject to the Cambridge Core terms of use, available at

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Brown Dwarf Jets: Investigating the Universality of Jet Launching
  Mechanisms at the Lowest Masses

Brown Dwarf Jets: Investigating the Universality of Jet Launching Mechanisms at the Lowest Masses

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