• A MUSE view of the asymmetric jet from HD 163296

      Xie, C.; Haffert, S.Y.; De Boer, J.; Kenworthy, M.A.; Brinchmann, J.; Girard, J.; Snellen, I.A.G.; Keller, C.U.; Steward Observatory, University of Arizona (EDP Sciences, 2021)
      Context. Jets and outflows are thought to play important roles in regulating star formation and disk evolution. An important question is how the jets are launched. HD 163296 is a well-studied Herbig Ae star that hosts proto-planet candidates, a protoplanetary disk, a protostellar jet, and a molecular outflow, which makes it an excellent laboratory for studying jets. Aims. We aim to characterize the jet at the inner regions and check if there are large differences with the features at large separations. A secondary objective is to demonstrate the performance of Multi Unit Spectroscopic Explorer (MUSE) in high-contrast imaging of extended line emission. Methods. MUSE in the narrow field mode (NFM) can provide observations at optical wavelengths with high spatial (∼75 mas) and medium spectral (R  ∼  2500) resolution. With the high-resolution spectral differential imaging technique, we can characterize the kinematic structures and physical conditions of jets down to 100 mas. Results. We detect multiple atomic lines in two new knots, B3 and A4, at distances of < 4 from the host star with MUSE. The derived M jet/M acc is about 0.08 and 0.06 for knots B3 and A4, respectively. The observed [Ca II]/[S II] ratios indicate that there is no sign of dust grains at distances of < 4. Assuming the A4 knot traced the streamline, we can estimate a jet radius at the origin by fitting the half width half maximum of the jet, which sets an upper limit of 2.2 au on the size of the launching region. Although MUSE has the ability to detect the velocity shifts caused by high- and low-velocity components, we found no significant evidence of velocity decrease transverse to the jet direction in our 500 s MUSE observation. Conclusions. Our work demonstrates the capability of using MUSE NFM observations for the detailed study of stellar jets in the optical down to 100 mas. The derived M jet/M acc, no dust grain, and jet radius at the star support the magneto-centrifugal models as a launching mechanism for the jet. © C. Xie et al. 2021.
    • Assessing the Impact of Astrochemistry on Molecular Cloud Turbulence Statistics

      Boyden, Ryan D.; Offner, Stella S. R.; Koch, Eric W.; Rosolowsky, Erik W.; Univ Arizona, Steward Observ; Univ Arizona, Dept Astron (IOP PUBLISHING LTD, 2018-06-20)
      We analyze hydrodynamic simulations of turbulent, star-forming molecular clouds that are post-processed with the photodissociation region astrochemistry code 3D-PDR. We investigate the sensitivity of 15 commonly applied turbulence statistics to post-processing assumptions, namely, variations in gas temperature, abundance, and external radiation field. We produce synthetic (CO)-C-12 (1-0) and CI (P-3(1)-P-3(0)) observations and examine how the variations influence the resulting emission distributions. To characterize differences between the data sets, we perform statistical measurements, identify diagnostics sensitive to our chemistry parameters, and quantify the statistic responses by using a variety of distance metrics. We find that multiple turbulent statistics are sensitive not only to the chemical complexity but also to the strength of the background radiation field. The statistics with meaningful responses include principal component analysis, spatial power spectrum, and bicoherence. A few of the statistics, such as the velocity coordinate spectrum, are primarily sensitive to the type of tracer being utilized, while others, like the.-variance, strongly respond to the background radiation field. Collectively, these findings indicate that more realistic chemistry impacts the responses of turbulent statistics and is necessary for accurate statistical comparisons between models and observed molecular clouds.
    • Dust Transport and Processing in Centrifugally Driven Protoplanetary Disk Winds

      Giacalone, Steven; Teitler, Seth; Königl, Arieh; Krijt, Sebastiaan; Ciesla, Fred J.; Univ Arizona, Dept Astron & Steward Observ (IOP PUBLISHING LTD, 2019-08-29)
      There is evidence that protoplanetary disks including the protosolar one-contain crystalline dust grains on spatial scales where the dust temperature is lower than the threshold value for their formation through thermal annealing of amorphous interstellar silicates. We interpret these observations in terms of an extended, magnetocentrifugally driven disk wind that transports grains from the inner disk-where they are thermally processed by the stellar radiation after being uplifted from the disk surfaces-to the outer disk regions. For any disk radius r, there is a maximum grain size a(max)(r) that can be uplifted from that location: grains of size a << a(max) are carried away by the wind, whereas those with a less than or similar to a(max) reenter the disk at larger radii. A significant portion of the reentering grains converge to-and subsequently accumulate in-a narrow region just beyond r(max)(a), the maximum radius from which grains of size a can be uplifted. We show that this model can account for the inferred crystallinity fractions in classical T Tauri and Herbig Ae disks and for their indicated near constancy after being established early in the disk evolution. It is also consistent with the reported radial gradients in the mean grain size, crystallinity, and crystal composition. In addition, this model yields the properties of the grains that remain embedded in the outflows from protoplanetary disks and naturally explains the inferred persistence of small grains in the surface layers of these disks.

      Watson, Dan M.; Calvet, Nuria P.; Fischer, William J.; Forrest, W. J.; Manoj, P.; Megeath, S. Thomas; Melnick, Gary J.; Najita, Joan; Neufeld, David A.; Sheehan, Patrick D.; et al. (IOP PUBLISHING LTD, 2016-08-29)
      We have surveyed 84 Class 0, Class I, and flat-spectrum protostars in mid-infrared [Si II], [Fe II], and [S I] line emission, and 11 of these in far-infrared [O I] emission. We use the results to derive their mass. outflow rates, (M) over dot(w). Thereby we observe a strong correlation of (M) over dot(w) with bolometric luminosity, and with the inferred mass accretion rates of the central objects, (M) over dot(a), which continues through the Class 0 range the trend observed in Class II young stellar objects. Along this trend from large to small mass. flow rates, the different classes of young stellar objects lie in the sequence Class 0-Class I/flat-spectrum-Class II, indicating that the trend is an evolutionary sequence in which (M) over dot(a) and (M) over dot(w) decrease together with increasing age, while maintaining rough proportionality. The survey results include two that. are key tests of magnetocentrifugal outflow-acceleration mechanisms: the distribution of the outflow/accretion branching ratio b = (M) over dot(w)/(M) over dot(a), and limits on the distribution of outflow speeds. Neither rules out any of the three leading outflow-acceleration, angular-momentum-ejection mechanisms, but they provide some evidence that disk winds and accretion-powered stellar winds (APSWs) operate in many protostars. An upper edge observed in the branching-ratio distribution is consistent with the upper bound of b = 0.6 found in models of APSWs, and a large fraction (31%) of the sample have a. branching ratio sufficiently small that only disk winds, launched on scales as large as several au, have been demonstrated to account for them.
    • High-resolution Near-IR Spectral Mapping with H-2 and [Fe II] Lines of Multiple Outflows around LkH alpha 234

      Oh, Heeyoung; Pyo, Tae-Soo; Koo, Bon-Chul; Yuk, In-Soo; Kaplan, Kyle F.; Lee, Yong-Hyun; Sokal, Kimberly R.; Mace, Gregory N.; Park, Chan; Lee, Jae-Joon; et al. (IOP PUBLISHING LTD, 2018-05)
      We present a high-resolution, near-IR spectroscopic study of multiple outflows in the LkH alpha 234 star formation region using the Immersion GRating INfrared Spectrometer (IGRINS). Spectral mapping over the blueshifted emission of HH 167 allowed us to distinguish at least three separate, spatially overlapped outflows in H-2 and [Fe II] emission. We show that the H-2 emission represents not a single jet but rather complex multiple outflows driven by three known embedded sources: MM1, VLA 2, and VLA 3. There is a redshifted H-2 outflow at a low velocity, V-LSR < +50 km s(-1), with respect to the systemic velocity of V-LSR = -11.5 km s(-1), that coincides with the H2O masers seen in earlier radio observations 2 '' southwest of VLA 2. We found that the previously detected [Fe II] jet with vertical bar V-LSR vertical bar > 100 km s(-1) driven by VLA 3B is also detected in H-2 emission and confirm that this jet has a position angle of about 240 degrees. Spectra of the redshifted knots at 14 ''-65 '' northeast of LkH alpha 234 are presented for the first time. These spectra also provide clues to the existence of multiple outflows. We detected high-velocity (50-120 km s(-1)) H-2 gas in the multiple outflows around LkH alpha 234. Since these gases move at speeds well over the dissociation velocity (> 40 km s(-1)), the emission must originate from the jet itself rather than H-2 gas in the ambient medium. Also, position-velocity and excitation diagrams indicate that emission from knot C in HH 167 comes from two different phenomena, shocks and photodissociation.
    • Kinematic Links and the Coevolution of MHD Winds, Jets, and Inner Disks from a High-resolution Optical [OI] Survey

      Banzatti, Andrea; Pascucci, Ilaria; Edwards, Suzan; Fang, Min; Gorti, Uma; Flock, Mario; Univ Arizona, Dept Planetary Sci; Univ Arizona, Dept Astron (American Astronomical Society, 2019-01-10)
      We present a survey of optical [O I] emission at 6300 angstrom toward 65 T Tauri stars at the spectral resolution of similar to 7 km s(-1). Past work identified a highly blueshifted velocity component (HVC) tracing microjets and a less blueshifted low-velocity component (LVC) attributed to winds. We focus here on the LVC kinematics to investigate links between winds, jets, accretion, and disk dispersal. We track the behavior of four types of LVC components: a broad and a narrow component ("BC" and "NC," respectively) in LVCs that are decomposed into two Gaussians which typically have an HVC, and single-Gaussian LVC profiles separated into those that have an HVC ("SCJ") and those that do not ("SC"). The LVC centroid velocities and line widths correlate with the HVC EW and accretion luminosity, suggesting that LVC/winds and HVC/jets are kinematically linked and connected to accretion. The deprojected HVC velocity correlates with accretion luminosity, showing that faster jets come with higher accretion. BC and NC kinematics correlate, and their blueshifts are maximum at similar to 35 degrees, suggesting a conical wind geometry with this semi-opening angle. Only SCs include n(13-31) up to similar to 3, and their properties correlate with this infrared index, showing that [O I] emission recedes to larger radii as the inner dust is depleted, tracing less dense/hot gas and a decrease in wind velocity. Altogether, these findings support a scenario where optically thick, accreting inner disks launch radially extended MHD disk winds that feed jets, and where inner disk winds recede to larger radii and jets disappear in concert with dust depletion.
    • The MOSDEF Survey: A Census of AGN-driven Ionized Outflows at z = 1.4–3.8

      Leung, Gene C. K.; Coil, Alison L.; Aird, James; Azadi, Mojegan; Kriek, Mariska; Mobasher, Bahram; Reddy, Naveen; Shapley, Alice; Siana, Brian; Fetherolf, Tara; et al. (IOP PUBLISHING LTD, 2019-11-13)
      Using data from the MOSFIRE Deep Evolution Field (MOSDEF) survey, we present a census of active galactic nucleus (AGN)-driven ionized outflows in a sample of 159 AGNs at 1.4 <= z <= 3.8. The sample spans AGN bolometric luminosities of 10(44-47) erg s(-1) and includes both quiescent and star-forming galaxies extending across 3 orders of magnitude in stellar mass. We identify and characterize outflows from the H beta, [O III], H alpha, and [N II] emission line spectra. We detect outflows in 17% of the AGNs, seven times more often than in a mass-matched sample of inactive galaxies in MOSDEF. The outflows are fast and galaxy-wide, with velocities of similar to 400-3500 km s(-1) and spatial extents of 0.3-11.0 kpc. The incidence of outflows among AGNs is independent of the stellar mass of the host galaxy, with outflows detected in both star-forming and quiescent galaxies. This suggests that outflows exist across different phases in galaxy evolution. We investigate relations between outflow kinematic, spatial, and energetic properties and both AGN and host galaxy properties. Our results show that AGN-driven outflows are widespread in galaxies along the star-forming main sequence. The mass-loading factors of the outflows are typically 0.1-1 and increase with AGN luminosity, capable of exceeding unity at L-AGN greater than or similar to 10(46) erg s(-1). In these more luminous sources, the ionized outflow alone is likely sufficient to regulate star formation and, when combined with outflowing neutral and molecular gas, may be able to quench star formation in their host galaxies.
    • Multiwavelength Characterization of an ACT-selected, Lensed Dusty Star-forming Galaxy at z = 2.64

      Roberts-Borsani, G. W.; Jiménez-Donaire, M. J.; Daprà, M.; Alatalo, Katherine; Aretxaga, I.; Álvarez-Márquez, J.; Baker, A. J.; Fujimoto, S.; Gallardo, P. A.; Gralla, M.; et al. (IOP PUBLISHING LTD, 2017-07-27)
      We present CI(2-1) and multi-transition (CO)-C-12 observations of a dusty star-forming galaxy, ACT J2029+0120, which we spectroscopically confirm to lie at z = 2.64. We detect CO(3-2), CO(5-4), CO(7-6), CO(8-7), and CI (2-1) at high significance, tentatively detect HCO+(4-3), and place strong upper limits on the integrated strength of dense gas tracers (HCN(4-3) and CS(7-6)). Multi-transition CO observations and dense gas tracers can provide valuable constraints on the molecular gas content and excitation conditions in high-redshift galaxies. We therefore use this unique data set to construct a CO spectral line energy distribution (SLED) of the source, which is most consistent with that of a ULIRG/Seyfert or QSO host object in the taxonomy of the Herschel Comprehensive ULIRG Emission Survey. We employ RADEX models to fit the peak of the CO SLED, inferring a temperature of T similar to 117 K and n(H2) similar to 10(5) cm(-3), most consistent with a ULIRG/QSO object and the presence of high-density tracers. We also find that the velocity width of the C I line is potentially larger than seen in all CO transitions for this object, and that the L'(Ci(2-1))/L'(CO(3-2)) ratio is also larger than seen in other lensed and unlensed submillimeter galaxies and QSO hosts; if confirmed, this anomaly could be an effect of differential lensing of a shocked molecular outflow.
    • An Ordered Envelope–Disk Transition in the Massive Protostellar Source G339.88-1.26

      Zhang, Yichen; Tan, Jonathan C.; Sakai, Nami; Tanaka, Kei E. I.; De Buizer, James M.; Liu, Mengyao; Beltrán, Maria T.; Kratter, Kaitlin; Mardones, Diego; Garay, Guido; et al. (IOP PUBLISHING LTD, 2019-03-01)
      We report molecular line observations of the massive protostellar source G339.88-1.26 with the Atacama Large Millimeter/Submillimeter Array. The observations reveal a highly collimated SiO jet extending from the 1.3. mm continuum source, which connects to a slightly wider but still highly collimated CO outflow. Rotational features perpendicular to the outflow axis are detected in various molecular emissions, including SiO, SO2, H2S, CH3OH, and H2CO emissions. Based on their spatial distributions and kinematics, we find that they trace different parts of the envelope-disk system. The SiO emission traces the disk and inner envelope in addition to the jet. The CH3OH and H2CO emissions mostly trace the infalling-rotating envelope and are enhanced around the transition region between envelope and disk, i.e., the centrifugal barrier. The SO2 and H2S emissions are enhanced around the centrifugal barrier and also trace the outer part of the disk. Envelope kinematics are consistent with rotating-infalling motion, while those of the disk are consistent with Keplerian rotation. The radius and velocity of the centrifugal barrier are estimated to be about 530 au and 6 km s(-1), respectively, leading to a central mass of about 11 M-circle dot, consistent with estimates based on spectral energy distribution fitting. These results indicate that an ordered transition from an infalling-rotating envelope to a Keplerian disk through a centrifugal barrier, accompanied by changes of types of molecular line emissions, is a valid description of this massive protostellar source. This implies that at least some massive stars form in a similar way to low-mass stars via core accretion.
    • Progenitor, precursor, and evolution of the dusty remnant of the stellar merger M31-LRN-2015

      Blagorodnova, N; Karambelkar, V; Adams, S M; Kasliwal, M M; Kochanek, C S; Dong, S; Campbell, H; Hodgkin, S; Jencson, J E; Johansson, J; et al. (OXFORD UNIV PRESS, 2020-06-30)
      M31-LRN-2015 is a likely stellar merger discovered in the Andromeda Galaxy in 2015. We present new optical to mid-infrared photometry and optical spectroscopy for this event. Archival data show that the source started to brighten similar to 2 yr before the nova event. During this precursor phase, the source brightened by similar to 3 mag. The light curve at 6 and 1.5 months before the main outburst may show periodicity, with periods of 16 +/- 0.3 and 28.1 +/- 1.4 d, respectively. This complex emission may be explained by runaway mass-loss from the system after the binary undergoes Roche lobe overflow, leading the system to coalesce in tens of orbital periods. While the progenitor spectral energy distribution shows no evidence of pre-existing warm dust in the system, the remnant forms an optically thick dust shell at approximately four months after the outburst peak. The optical depth of the shell increases dramatically after 1.5 yr, suggesting the existence of shocks that enhance the dust formation process. We propose that the merger remnant is likely an inflated giant obscured by a cooling shell of gas with mass similar to 0.2 M-circle dot ejected at the onset of the common envelope phase.
    • Proper motions of collimated jets from intermediate-mass protostars in the Carina Nebula

      Reiter, Megan; Kiminki, Megan M.; Smith, Nathan; Bally, John; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2017-10)
      We present proper motion measurements of 37 jets and HH objects in the Carina Nebula measured in two epochs of H alpha images obtained similar to 10 yr apart with Hubble Space Telescope/Advanced Camera for Surveys (ACS). Transverse velocities in all but one jet are faster than greater than or similar to 25 km s(-1), confirming that the jet-like H alpha features identified in the first epoch images trace outflowing gas. Proper motions constrain the location of the jet-driving source and provide kinematic confirmation of the intermediate-mass protostars that we identify for 20/37 jets. Jet velocities do not correlate with the estimated protostar mass and embedded driving sources do not have slower jets. Instead, transverse velocities (median similar to 75 km s(-1)) are similar to those in jets from low-mass stars. Assuming a constant velocity since launch, we compute jet dynamical ages (median similar to 10(4) yr). If continuous emission from inner jets traces the duration of the most recent accretion bursts, then these episodes are sustained longer (median similar to 700 yr) than the typical decay time of an FU Orionis outburst. These jets can carry appreciable momentum that may be injected into the surrounding environment. The resulting outflow force, dp/dt, lies between that measured in low- and high-mass sources, despite the very different observational tracers used. Smooth scaling of the outflow force argues for a common physical process underlying outflows from protostars of all masses. This latest kinematic result adds to a growing body of evidence that intermediate-mass star formation proceeds like a scaled-up version of the formation of low-mass stars.
    • Searching for proto-planets with MUSE

      Xie, C.; Haffert, S.Y.; De Boer, J.; Kenworthy, M.A.; Brinchmann, J.; Girard, J.; Snellen, I.A.G.; Keller, C.U.; Steward Observatory, University of Arizona (EDP Sciences, 2020)
      Context.Protoplanetary disks contain structures such as gaps, rings, and spirals, which are thought to be produced by the interaction between the disk and embedded protoplanets. However, only a few planet candidates are found orbiting within protoplanetary disks, and most of them are being challenged as having been confused with disk features. Aims. The VLT/MUSE discovery of PDS 70 c demonstrated a powerful way of searching for still-forming protoplanets by targeting accretion signatures with medium-resolution integral field spectroscopy. We aim to discover more proto-planetary candidates with MUSE, with a secondary aim of improving the high-resolution spectral differential imaging (HRSDI) technique by analyzing the instrumental residuals of MUSE. Methods. We analyzed MUSE observations of five young stars with various apparent brightnesses and spectral types. We applied the HRSDI technique to perform high-contrast imaging. The detection limits were estimated using fake planet injections. Results. With a 30 min integration time, MUSE can reach 5σ detection limits in apparent Hα line flux down to 10-14 and 10-15 erg s-1 cm-2 at 0.075' and 0.25', respectively. In addition to PDS 70 b and c, we did not detect any clear accretion signatures in PDS 70, J1850-3147, and V1094 Sco down to 0.1'. MUSE avoids the small sample statistics problem by measuring the noise characteristics in the spatial direction at multiple wavelengths. We detected two asymmetric atomic jets in HD 163296 with a very high spatial resolution (down to 8 au) and medium spectral resolution (R 2500). Conclusions. The HRSDI technique when applied to MUSE data allows us to reach the photon noise limit at small separations (i.e., <0.5'). With the combination of high-contrast imaging and medium spectral resolution, MUSE can achieve fainter detection limits in apparent line flux than SPHERE/ZIMPOL by a factor of 5. MUSE has some instrumental issues that limit the contrast that appear in cases with strong point sources, which can be either a spatial point source due to high Strehl observations or a spectral point source due to a high line-to-continuum ratio. We modified the HRSDI technique to better handle the instrumental artifacts and improve the detection limits. To avoid the instrumental effects altogether, we suggest faint young stars with relatively low Hα line-to-continuum ratio to be the most suitable targets for MUSE to search for potential protoplanets. © ESO 2020.
    • A SiO J = 5 → 4 Survey Toward Massive Star Formation Regions

      Li, Shanghuo; Wang, Junzhi; Fang, Min; Zhang, Qizhou; Li, Fei; Zhang, Zhi-Yu; Li, Juan; Zhu, Qingfeng; Zeng, Shaoshan; Univ Arizona, Dept Astron; et al. (IOP PUBLISHING LTD, 2019-06-11)
      We performed a survey in the SiO J = 5 → 4 line toward a sample of 199 Galactic massive star-forming regions at different evolutionary stages with the Submillimeter Telescope (SMT) 10 m and Caltech Submillimeter Observatory (CSO) 10.4 m telescopes. The sample consists of 44 infrared dark clouds (IRDCs), 86 protostellar candidates, and 69 young H ii regions. We detected SiO J = 5 → 4 line emission in 102 sources, with a detection rate of 57%, 37%, and 65% for IRDCs, protostellar candidates, and young H ii regions, respectively. We find both broad line emissions with full widths at zero power >20 km s−1 and narrow line emissions of SiO in objects at various evolutionary stages, likely associated with high-velocity shocks and low-velocity shocks, respectively. The SiO luminosities do not show apparent differences among various evolutionary stages in our sample. We find no correlation between the SiO abundance and the luminosity-to-mass ratio, indicating that the SiO abundance does not vary significantly in regions at different evolutionary stages of star formation.
    • X Marks the Spot: Nexus of Filaments, Cores, and Outflows in a Young Star-forming Region

      Imara, Nia; Lada, Charles; Lewis, John; Bieging, John H.; Kong, Shuo; Lombardi, Marco; Alves, Joao; Univ Arizona, Steward Observ (IOP PUBLISHING LTD, 2017-05-15)
      We present a multiwavelength investigation of a region of a nearby giant molecular cloud that is distinguished by a minimal level of star formation activity. With our new (CO)-C-12(J = 2-1) and (CO)-C-13(J = 2-1) observations of a remote region within the middle of the California molecular cloud, we aim to investigate the relationship between filaments, cores, and a molecular outflow in a relatively pristine environment. An extinction map of the region from Herschel Space Observatory observations reveals the presence of two 2 pc long filaments radiating from a highextinction clump. Using the (CO)-C-13 observations, we show that the filaments have coherent velocity gradients and that their mass-per-unit-lengths may exceed the critical value above which filaments are gravitationally unstable. The region exhibits structure with eight cores, at least one of which is a starless, prestellar core. We identify a low-velocity, low-mass molecular outflow that may be driven by a flat spectrum protostar. The outflow does not appear to be responsible for driving the turbulence in the core with which it is associated, nor does it provide significant support against gravitational collapse.