Preprint

# The ALMA-PILS survey: Gas dynamics in IRAS 16293$-$2422 and the connection between its two protostars

Authors:
Preprints and early-stage research may not have been peer reviewed yet.
To read the file of this research, you can request a copy directly from the authors.

## Abstract

[Abridged] The majority of stars form in binary or higher order systems. The Class 0 protostellar system IRAS16293-2422 contains two protostars, 'A' and 'B', separated by ~600 au and embedded in a single, 10^4 au scale envelope. Their relative evolutionary stages have been debated. We aim to study the relation and interplay between the two protostars A and B at spatial scales of 60 to ~1000 au. We selected molecular gas line transitions of CO, H2CO, HCN, CS, SiO, and CCH from the ALMA-PILS spectral imaging survey (329-363 GHz) and used them as tracers of kinematics, density, and temperature in the IRAS16293-2422 system. The angular resolution of the PILS data set allows us to study these quantities at a resolution of 0.5 arcsec (60 au [..]). Line-of-sight velocity maps of both optically thick and optically thin molecular lines reveal: (i) new manifestations of previously known outflows emanating from protostar A; (ii) a kinematically quiescent bridge of dust and gas spanning between the two protostars, with an inferred density between 4 10^4 and 3 10^7 cm^-3; and (iii) a separate, straight filament seemingly connected to protostar B seen only in CCH, with a flat kinematic signature. Signs of various outflows, all emanating from source A, are evidence of high-density and warmer gas; none of them coincide spatially and kinematically with the bridge. We hypothesize that the bridge arc is a remnant of filamentary substructure in the protostellar envelope material from which protostellar sources A and B have formed. One particular morphological structure appears to be due to outflowing gas impacting the quiescent bridge material. The continuing lack of clear outflow signatures unambiguously associated to protostar B and the vertically extended shape derived for its disk-like structure lead us to conclude that source B may be in an earlier evolutionary stage than source A.

## No file available

ResearchGate has not been able to resolve any citations for this publication.
Full-text available
Article
The formation of planets around binary stars may be more difficult than around single stars. In a close binary star (with a separation of less than a hundred astronomical units), theory predicts the presence of circumstellar disks around each star, and an outer circumbinary disk surrounding a gravitationally cleared inner cavity around the stars. Given that the inner disks are depleted by accretion onto the stars on timescales of a few thousand years, any replenishing material must be transferred from the outer reservoir to fuel planet formation (which occurs on timescales of about one million years). Gas flowing through disk cavities has been detected in single star systems. A circumbinary disk was discovered around the young low-mass binary system GG Tau A (ref. 7), which has recently been shown to be a hierarchical triple system. It has one large inner disk around the single star, GG Tau Aa, and shows small amounts of shocked hydrogen gas residing within the central cavity, but other than a single weak detection, the distribution of cold gas in this cavity or in any other binary or multiple star system has not hitherto been determined. Here we report imaging of gas fragments emitting radiation characteristic of carbon monoxide within the GG Tau A cavity. From the kinematics we conclude that the flow appears capable of sustaining the inner disk (around GG Tau Aa) beyond the accretion lifetime, leaving time for planet formation to occur there. These results show the complexity of planet formation around multiple stars and confirm the general picture predicted by numerical simulations.
Full-text available
Article
The frequencies of the first six rotational transitions of the CO molecule have been measured to an accuracy of $\pm 500 Hz$ in the frequency region up to 700 GHz. This high level of accuracy was achieved with the Cologne terahertz spectrometer operated in the sub-Doppler mode (1). To carry out precise CO Lamb-dip measurements, Least squares fits of the new CO, and 0.26 kHz, respectively. The experimental setup and the results of a fit to the Lamb-dip data combined with the frequencies up to 4.3 THz $(J = 38 \leftarrow 37)$ given by Evenson (3) will be presented. The analysis yielded a revised set of rotational constants for CO in its vibrational ground state, which is in good agreement with the previous values given by Varberg and Evenson(4).
Article
Binary and multiple star systems are a frequent outcome of the star formation process, and as a result, almost half of all sun-like stars have at least one companion star. Theoretical studies indicate that there are two main pathways that can operate concurrently to form binary/multiple star systems: large scale fragmentation of turbulent gas cores and filaments or smaller scale fragmentation of a massive protostellar disk due to gravitational instability. Observational evidence for turbulent fragmentation on scales of $>$1000~AU has recently emerged. Previous evidence for disk fragmentation was limited to inferences based on the separations of more-evolved pre-main sequence and protostellar multiple systems. The triple protostar system L1448 IRS3B is an ideal candidate to search for evidence of disk fragmentation. L1448 IRS3B is in an early phase of the star formation process, likely less than 150,000 years in age, and all protostars in the system are separated by $<$200~AU. Here we report observations of dust and molecular gas emission that reveal a disk with spiral structure surrounding the three protostars. Two protostars near the center of the disk are separated by 61 AU, and a tertiary protostar is coincident with a spiral arm in the outer disk at a 183 AU separation. The inferred mass of the central pair of protostellar objects is $\sim$1 M$_{sun}$, while the disk surrounding the three protostars has a total mass of $\sim$0.30 M$_{\sun}$. The tertiary protostar itself has a minimum mass of $\sim$0.085 M$_{sun}$. We demonstrate that the disk around L1448 IRS3B appears susceptible to disk fragmentation at radii between 150~AU and 320~AU, overlapping with the location of the tertiary protostar. This is consistent with models for a protostellar disk that has recently undergone gravitational instability, spawning one or two companion stars.
Article
APLpy (the Astronomical Plotting Library in Python) is a Python module for producing publication-quality plots of astronomical imaging data in FITS format. The module uses Matplotlib, a powerful and interactive plotting package. It is capable of creating output files in several graphical formats, including EPS, PDF, PS, PNG, and SVG. Plots can be made interactively or by using scripts, and can generate co-aligned FITS cubes to make three-color RGB images. It also offers different overlay capabilities, including contour sets, markers with customizable symbols, and coordinate grids, and a range of other useful features.
Article
The pure rotational J+1←J transitions, with J=0, 1, 3–8, of H13CN have been observed in the millimeter- and submillimeter-wave region using the Lamb-dip technique to resolve the hyperfine structure due to H, 13C, and 14N. The present observations allow us to provide for the first time the spin–rotation constant of 13C and the spin–spin interaction constant S12 (between H and 13C) as well as to remarkably improve the quadrupole coupling and spin–rotation constants of 14N. In addition, a good empirical estimation of CI(H), based on ab initio calculations, has also been provided. Furthermore, our frequencies together with previous data permit to determine the most accurate ground state rotational parameters known up to now.
Article
The rotational spectra of formaldehyde, H212C16O and its isotopic species H213C16O, H212C18O, and H213C18O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H212C16O and H213C16O a large number of ΔKa = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are: {A table is presented} This paper reports the first observations of the H213C18O rotational spectrum.
Article
Measurements of the present-day abundances of elements and isotopes, combined with model calculations, allow us to trace the history of nucleosynthesis in the universe. Throughout this review, emphasis will be placed on descriptions of the measurement processes and the interpretations needed to obtain actual isotope and element abundances from measurements. Comparisons of the abundances of isotopomers of a given element are less affected by systematic effects than are comparisons of the abundances of different elements. Thus ratios of isotopomers should be given a greater weight when data and models are compared. As is generally accepted, the universe began with an explosive event, the Big Bang. The nucleosynthesis associated with this event produced primordial' abundances of the light elements', deuterium, , , and . Subsequent stellar processing of the light elements has altered the relative abundances, and also produced heavier elements such as carbon, nitrogen and oxygen. Stellar nucleosynthesis products from solar and larger mass stars are expelled into the interstellar medium (ISM). The goal of studies of the abundances of the light elements is to estimate the primordial abundances, that is, the abundances produced in the Big Bang. It is believed that D is always net destroyed in stars; and may be net produced, is certainly net produced. In the Solar System itself, results are obtained from in situ measurements with space probes to Jupiter, measurements of solar wind constituents, the analysis of the content of meteorites, and spectral line measurements of the solar photosphere. For sources outside the Solar System, these data are based on spectral line measurements of gas-phase species. The ratio of gas-phase abundances of elements, such as carbon to lithium may be affected by differing amounts of condensation onto dust grains; however such a process will not affect the ratio of isotopes such as . The most reliable measurements of D to H ratios are based on spectroscopic measurements of Lyman series ultraviolet absorption lines from foreground interstellar gas. Measurements of clouds in our galaxy have been obtained with satellites such as the International Ultraviolet Observatory, Copernicus, and the Hubble Space Telescope. The most interesting new development is the measurement of distant clouds with large redshifted velocities. Such data can be taken with Earth-bound optical telescopes. In the near future the Far Ultra Violet Explorer will refine and extend measurements of D/H ratios in relatively nearby regions. Abundances of in the ISM have been measured using the hyperfine transition of , in galactic H II regions which are ionized by high-mass stars. is the most abundant of the light elements. The primordial abundance must be very accurately determined if one wishes to use this quantity to estimate the baryon density in the early universe. Recently /H ratios have been measured in a number of metal-poor compact blue galaxies. These sources seem to have had little stellar evolution, so the ratio should be close to the primordial value. Estimates of the primordial abundance of are made for a population of old stars found far from the plane of our galaxy. A refinement of Li abundance estimates requires a more detailed understanding of the Li destruction processes in stars.
Article
Matplotlib is a 2D graphics package used for Python for application development, interactive scripting, and publication-quality image generation across user interfaces and operating systems. The latest release of matplotlib runs on all major operating systems, with binaries for Macintosh's OS X, Microsoft Windows, and the major Linux distributions. Matplotlib has a Matlab emulation environment called PyLab, which is a simple wrapper of the matplotlib API. Matplotlib provides access to basic GUI events such as button_press_event, mouse_motion_event and can also be registered with those events to receive callbacks. Event handling code written in matplotlib works across many different GUIs. It supports toolkits for domain specific plotting functionality that is either too big or too narrow in purpose for the main distribution. Matplotlib has three basic API classes, including, FigureCanvasBase, RendererBase and Artist.
• S P Ruden
• F H Shu
Adams, F. C., Ruden, S. P., & Shu, F. H. 1989, ApJ, 347, 959
• Y Aikawa
• T Umebayashi
• T Nakano
• S M Miyama
Aikawa, Y., Umebayashi, T., Nakano, T., & Miyama, S. M. 1997, ApJ, 486, L51
• T P Robitaille
• E J Tollerud
Astropy Collaboration, Robitaille, T. P., Tollerud, E. J., et al. 2013, A&A, 558, A33
• A M Baryshev
• R Hesper
• F P Mena
Baryshev, A. M., Hesper, R., Mena, F. P., et al. 2015, A&A, 577, A129
• S E Bisschop
• J K Jørgensen
• T L Bourke
• S Bottinelli
• E F Van Dishoeck
Bisschop, S. E., Jørgensen, J. K., Bourke, T. L., Bottinelli, S., & Van Dishoeck, E. F. 2008, A&A, 488, 959
• P Bjerkeli
• J K Jørgensen
• C Brinch
Bjerkeli, P., Jørgensen, J. K., & Brinch, C. 2016, A&A, 587, A145
• I A Bonnell
• M R Bate
Bonnell, I. A. & Bate, M. R. 1994, MNRAS, 269
• S Bottinelli
• C Ceccarelli
• R Neri
Bottinelli, S., Ceccarelli, C., Neri, R., et al. 2004, ApJ, 617, L69
• T L Bourke
• P C Myers
• Neal J Evans
Bourke, T. L., Myers, P. C., Evans, Neal J., I., et al. 2006, ApJ, 649, L37 Brinch, C. & Hogerheijde, M. R. 2010, A&A, 523, A25
• C Brinch
• M R Hogerheijde
Brinch, C. & Hogerheijde, M. R. 2010, A&A, 523, A25
• C Brinch
• J K Jørgensen
• M R Hogerheijde
• R P Nelson
• O Gressel
Brinch, C., Jørgensen, J. K., Hogerheijde, M. R., Nelson, R. P., & Gressel, O. 2016, ApJ, 830, L16
• H Calcutt
• J K Jørgensen
• H S P Müller
Calcutt, H., Jørgensen, J. K., Müller, H. S. P., et al. 2018, A&A, 616, A90
• P Caselli
• T W Hartquist
• O Havnes
Caselli, P., Hartquist, T. W., & Havnes, O. 1997, A&A, 322, 296
• E Caux
• C Kahane
• A Castets
Caux, E., Kahane, C., Castets, A., et al. 2011, A&A, 532, A23
• C Ceccarelli
• A Castets
• E Caux
Ceccarelli, C., Castets, A., Caux, E., et al. 2000, A&A, 355, 1129
• C Ceccarelli
• L Loinard
• A Castets
Ceccarelli, C., Loinard, L., Castets, A., et al. 2001, A&A, 372, 998
• C J Chandler
• C L Brogan
• Y L Shirley
• L Loinard
Chandler, C. J., Brogan, C. L., Shirley, Y. L., & Loinard, L. 2005, ApJ, 632, 371
• X Chen
• H G Arce
• Q Zhang
Chen, X., Arce, H. G., Zhang, Q., et al. 2013, ApJ, 768, 110
• J K Jørgensen
• M H D Van Der Wiel
• A Coutens
Jørgensen, J. K., Van der Wiel, M. H. D., Coutens, A., et al. 2016, A&A, 595, A117
• A Coutens
• E R Willis
• R T Garrod
Coutens, A., Willis, E. R., Garrod, R. T., et al. 2018, A&A, 612, A107
• N Crimier
• C Ceccarelli
• S Maret
Crimier, N., Ceccarelli, C., Maret, S., et al. 2010, A&A, 519, A65
• J R Goicoechea
• P Pilleri
Cuadrado, S., Goicoechea, J. R., Pilleri, P., et al. 2015, A&A, 575, A82
• F Dayou
• C Balança
Dayou, F. & Balança, C. 2006, A&A, 459, 297
• M N Drozdovskaya
• E F Van Dishoeck
• J K Jørgensen
Drozdovskaya, M. N., Van Dishoeck, E. F., Jørgensen, J. K., et al. 2018, MNRAS, 476, 4949
• M N Drozdovskaya
• C Walsh
• R Visser
• D Harsono
• E F Van Dishoeck
Drozdovskaya, M. N., Walsh, C., Visser, R., Harsono, D., & Van Dishoeck, E. F. 2015, MNRAS, 451, 3836
• G Duchêne
• A Kraus
Duchêne, G. & Kraus, A. 2013, ARA&A, 51, 269
• F Dumouchel
• A Faure
• F Lique
Dumouchel, F., Faure, A., & Lique, F. 2010, MNRAS, 406, 2488
• A Dutrey
• E Di Folco
• T Beck
• S Guilloteau
Dutrey, A., Di Folco, E., Beck, T., & Guilloteau, S. 2016, A&A Rev., 24, 5
• A Dutrey
• E Di Folco
• S Guilloteau
Dutrey, A., Di Folco, E., Guilloteau, S., et al. 2014, Nature, 514, 600 Article number, page 15 of 27
• S A Dzib
• G N Ortiz-León
• A Hernández-Gómez
Dzib, S. A., Ortiz-León, G. N., Hernández-Gómez, A., et al. 2018, A&A, 614, A20
• C P Endres
• S Schlemmer
• P Schilke
• J Stutzki
• H S P Müller
Endres, C. P., Schlemmer, S., Schilke, P., Stutzki, J., & Müller, H. S. P. 2016, J. Mol. Spectrosc., 327, 95
• C Favre
• J K Jørgensen
• D Field
Favre, C., Jørgensen, J. K., Field, D., et al. 2014, ApJ, 790, 55
• E C Fayolle
• K I Öberg
• J K Jørgensen
Fayolle, E. C., Öberg, K. I., Jørgensen, J. K., et al. 2017, Nature Astronomy, 1, 703
• M Fernández-López
• L A Zapata
• R Gabbasov
Fernández-López, M., Zapata, L. A., & Gabbasov, R. 2017, ApJ, 845, 10
• D R Flower
• G Pineau Des Forets
• D Field
• P W May
Flower, D. R., Pineau des Forets, G., Field, D., & May, P. W. 1996, MNRAS, 280, 447
• R T Garrod
• A Belloche
• H S P Müller
• K M Menten
Garrod, R. T., Belloche, A., Müller, H. S. P., & Menten, K. M. 2017, A&A, 601, A48
• J M Girart
• R Estalella
• A Palau
• J M Torrelles
• R Rao
Girart, J. M., Estalella, R., Palau, A., Torrelles, J. M., & Rao, R. 2014, ApJ, 780, L11
• C A Gottlieb
• P C Myers
Gottlieb, C. A., Myers, P. C., & Thaddeus, P. 2003, ApJ, 588, 655
• A Gusdorf
• S Cabrit
• D R Flower
• Pineau Des
• G Forêts
Gusdorf, A., Cabrit, S., Flower, D. R., & Pineau Des Forêts, G. 2008a, A&A, 482, 809
• A Gusdorf
• G Pineau Des Forêts
• S Cabrit
• D R Flower
Gusdorf, A., Pineau Des Forêts, G., Cabrit, S., & Flower, D. R. 2008b, A&A, 490, 695
• V Guzmán
• J Pety
• J R Goicoechea
• M Gerin
• E Roueff
Guzmán, V., Pety, J., Goicoechea, J. R., Gerin, M., & Roueff, E. 2011, A&A, 534, A49
• E Herbst
• E F Van Dishoeck
Herbst, E. & Van Dishoeck, E. F. 2009, ARA&A, 47, 427