High Angular Resolution Observations of Maser Kinematics in Nearby Low Mass Young Stellar Objects

1. High Angular Resolution Observations of Maser Kinematics in Nearby Low Mass Young Stellar Objects Al Wootten NRAO Co-investigators Mark Claussen (NRAO), Kevin Marvel (AAS), Bruce Wilking (UMSL), Ray Furuya (Arcetri), Jeff Mangum (NRAO), Ronak Shah (Illinois) CWRU Astronomy

2. Star Formation Paradigm • Dense core forms star and perhaps disk accompanied by outflow • Problems: separation of infall motions (typically few km/s) from rotation (typically few km/s) and outflow (typically tens of km/s) in a region perhaps 10” (1400 AU at 150 pc distance) • Example: a comparison of two molecules as probes of the region near a forming star: IRAS16293-2422 • Sensitivity of current instruments inadequate; hence the use of maser lines as probes of inner regions

3. Formaldehyde, an asymmetric rotor molecule, has many transitions. Some of these, at different energy levels, lie adjacent in frequency and may be observed simultaneously. One useful grouping of lines includes lines at 211, 218.2, 218.5, 218.8 and 226 GHz. The cluster at 218 GHz is especially well suited to existing correlators. Furthermore, these lines lie at 23 K (218.2 GHz line) and 64 K (the others) above ground, and are from the para form of formaldehyde. Wootten and Shah

4. Ammonia, an asymmetric top molecule, has a number of inversion lines lying close together in frequency near 1.3cm. The two lowest observable energy transitions lie at energies of 23 K and 64 K above ground. Even with antiquated correlators, these two transitions may be observed simultaneously. Our hypothesis: With like energetics, the reasons for differences in the distribution of these two molecules must lie in their chemistry Test: Image them in similar star forming regions

5. Imaging of three regions is underway: IRAS16293-2422, L1448 IRS3, S68N • Ammonia (VLA) and formaldehyde (BIMA) data is under analysis for all, • preliminary results will be shown here for IRAS16293-2422 and S68N. • Total power data is problematic; with the closure of the NRAO 12m no U. S. • Facility can obtain the needed data for all transitions; the CSO suffices for these • two. • Spatial distribution (flow, core, disk) • Kinematics (infall, outflow, rotation) • Temperature • Density (through millimeter continuum measures) IRAS16293-2422 A and B Very young binary in a very massive common envelope; IRAS 16293-2422 has a Class 0 spectral energy distribution (SED) and has strong 1.3mm continuum emission due to the dusty environment within which it is deeply embedded. ~.5 and ~.6 solar masses in compact structures About 30 solar luminosities; complex outflow

6. Spatial Distribution • NH3: flattened distribution, (1,1) weakly peaked at positions of mm continuum emission. (2,2) shows negligible emission except on most compact scales • H2CO: flattened distribution in K=0 line, strongly peaked at positions of mm continuum emission in K=2 and K=0. Conclusion: Although H2CO emits strongly in the inner envelope gas the embedded protostellar objects, ammonia does not. The strength of the H2CO K=2 line suggests that gas in this vicinity has been substantially warmed by the presence of the protostars, to 50K or warmer. The weakness of the NH3 K=2 line suggests that the ammonia gas has not been warmed. On still finer scales, H2CO suggests warmer temperatures. The spatial distribution suggests that ammonia avoids the inner envelope relative to H2CO and to dust emission. Ammonia does show a compact component very near the protostars. The molecular excitation supports this--the warm ammonia gas appears to be much cooler than the warm formaldehyde gas in the inner envelope.

7. CO--Lis et al to be submitted Kinematics: Outflow • IRAS16293: Outflow • Occurs only from ‘A’ • PA 50 near star but with opposite polarity to large scales! • Little evidence that formaldehyde participates in the outflow • No evidence that ammonia participates in the outflow Water Masers -- VLBA

8. Kinematics: Core motions H2CO • Rotation: dominant motion of H2CO in IRAS16293 • Line broadens substantially at mm sources • Line center velocities increase to SE • Velocities change by 2 km/s over 6”=900AU or 400 km/s/pc! SE N NW

9. NH3 Kinematics: Core motions • Rotation: less discernible motions of NH3 in IRAS16293 • (1,1) and (2,2) Lines broaden somewhat at mm sources • Line center velocities stable across 30” structure-- little evidence of rotation • Some evidence for rotation at most sensitive levels

10. Kinematics: Summary • H2CO: • Subtly present in outflow • Strongly present in envelope • Strongly present in inner envelope • NH3: • Not evident in outflow • Strong in outer reaches of envelope only • Present in inner envelope Temperature • H2CO: • Indeterminate in outflow • Envelope temperature ~xxK • Inner envelope temperature • NH3: • Not evident in outflow • Cool envelope temperature • Inner envelope warmer Abundance • H2CO: • About 10-9 in envelope • Perhaps 10-7 in inner 100 AU (Ceccarelli et al.) NH3: Decreases with increasing density in envelope Probably rises in inner envelope

11. Conclusions • H2CO and NH3 both provide good probes of circumstellar envelopes. • In cool regions of intermediate density, ammonia is abundant but apparently its abundance can drop as density increases • As temperature increases, abundances of both H2CO and NH3 may rise • Therefore formaldehyde is probably a better probe of intermediate density regions and their connection to denser regions • In some other regions, formaldehyde also strongly traces outflow. This can hamper its efficacy in trying to understand infall motions in the envelope. • With current sensitivities, penetration further into the region where the star is forming requires new tools…water masers? Exception is the rule, however…..

12. Multi-Epoch Survey with Nobeyama 45 m Telescope • 1996 - 1999, total of 32 epochs • 254 sources (δ>-25°) with 598 obs. Including 30 preprotostellar cores (PPCs), all of the northern Class 0 sources, 5 Class II, and 4 high-mass sources • Beam size ~75”; pointing acc. is better than 10” • Sensitivities with 0.5 km/s res. are • ~50 mK in TA* (140 mJy ) in winter • ~100 mK in TA* (280 mJy ) in summer This is the most sensitive survey ever performed • Velocity coverage ~2,500 km/s • Follow-up 3-epoch VLA observations Particularly for crowded regions --- NGC1333, Oph, Serpens…. Furuya, Kitamura, Wootten, Claussen and Kawabe 2001

13. Results:from Nobeyama 45m telescope and VLA observations • 8 of 35 Class 0 sources (including high-mass sources), while only 3 Class I sources (GSS30-IRS, YLW 16, and T Tau) show maser emissions. • Our new detections are B1-IRS,NGC 2024-FIR5, IRAS 05375+0731, Serpens-SMM4, L723-FIR, GF 9-2, IRAS 22198+6336, IRAS 22266+6845, and L1204A. • We newly detected extremely high velocity components towards IRAS 20050+2720 (-92 km/s) and Cep E (-61 and –38 km/s) • 3 Class 0 sources (L1448-IRS2, L1448C, and Serpens 68N) previously reported to show maser emissions above our detection limit were not active during our observations. • The lowest luminosity source (Lbol~0.3Lsun) which shows masers is GF 9-2. • Our VLA observations established H2O masers in T Tau to be associated with T Tau south.

14. Implications: Detection Rates of the Masers In order to calculate the detection rates, we selected Class 0, I, and II sources which are nearby (d < 450 pc), low-mass (Lbol< 100 Lsun), and have well-defined bolometric temperatures. Preprotostellar Cores 0.0 % (30 samples; 30 obs.) 44 % (22 samples; 134 obs.) Class 0 4.2 % (32 samples; 89 obs.) Class I 0.0 % (5 samples; 14 obs.) Class II Class 0 sources are favorable sites to Harbor H2O masers.

15. 0.68 LH2O ~Lbol 0.78 LH2O ~Menv Implications: Luminosity of the Masers vs.Bolometric Luminosity and Envelope Mass As previously suggested by Felli et al. (1992) and Wilking et al.(1994), LH2O correlates with FIR luminosity (~Lbol). This correlation can be found even down to LH2O ~ 10-12 –10-13 Lsun(upper panel). Furthermore, we found a correlation with the envelope mass (Menv; lower panel) measured from 1.3 mm continuum emission. From “Class 0” to “Class I”, Menv changes considerably (mean ~1.1+/-0.1 Msun; Bontemps et al. 1996). Considering this fact, the large Menv is likely to be responsible for the high H2O maser intensities. This is because the large Menv provides more favorable conditions for maser amplification.

16. log LH2O (Lsun) log LmCO (Lsun) Luminosity of the Masers vs. Mechanical Luminosity of CO outflows, and Luminosity of Radio Continuum Emission Felli, Palagi & Tofani 1992 Medicina 32m survey Down to ~10-9 Lsun, LH2O is known to correlate with mechanical luminosity of CO outflows. However, a clear correlation cannot be found for LH2O < 10-9 Lsun(upper left). On the other hand, LH2O correlate well with radio continuum emission (lower left). Therefore, masers are more likely related to 100 AU scale ionized jets than to large scale molecular outflows.

17. Motivation Water masers near young, low-mass stars are thought to form in shocks associated with the energetic outflows from forming stars (Elitzur et al. 1989). The tremendous brightness of water masers make them good tracers of motions in molecular gas on small scales. The Very Long Baseline Array (VLBA) provides beams of about one half milliarcsecond (0.17 AU) in size and can measure proper motions of about 10 km s-1 in the several days to weeks lifetime of a typical maser at a distance of 350 pc, the distance generally employed for NGC1333. Observationally, masers occur within about 100 AU of their low luminosity driving source, and provide excellent signposts for the source of a flow, as well as good probes of the flow geometry and dynamics. The geometry of a flow and the physics of maser emission (produced along a tangential sight-line through the flow cocoon) conspire to result in a spread of radial velocity in a typical low mass maser source of only a few km s-1. A few Herbig-Haro objects have measured proper motions of as much as a few hundred km s-1; CO also shows very high velocities in this source--can the masers also show such high space velocities? Recent VLBI observations (Claussen et al. 1999, Furuya et al. 1999) have confirmed this theory for two sources, IRAS 05413-0104 and S106FIR. These observations show that the masers are aligned with the outflow axis and have proper motions of 60 to 100 km/s. Wootten, Murphy, Marvel, Claussen and Wilking

18. Objectives • The basic objective of the observations was to measure the proper motions of the observable water masers over a short period (~4 mos.). • We (Claussen et al. 1999) produced a proper motion map for IRAS 05413-0104 shown below. • Class 0 SED, 14 Lsun, 0.4 Menv central mass in 12000 AU rotating disk (Wiseman et al. 2000) • Space motions of 64 +/- 27 km/s for maser components. • Within 40 AU of protostar. • Large scale (0.6 pc) at same position angle from source A plot from Claussen et al. (1999) showing the spectrum, distribution and proper motions of the water masers associated with IRAS 05413-0104. Notice the bow-shock shaped structure near 20,-50.

19. One group of water masers in S106FIR (Furuya et al. 1999) clearly lie along a bow-shock structure that is propagating through the surrounding medium. • 40-70 km/s expansion • Region 50AU x 5 AU • No larger scale outflow in e.g. CO

20. IRAS16293: Masers Observations of IRAS 16293-2422 have been made with the VLA and with OVRO (Wootten 1993; Mundy et al. 1990) of water masers (VLA) and continuum emission (VLA and OVRO). These observations show that the masers exist in a bipolar outflow on scales smaller than 40 AU and are associated with the SE component. The water masers observed with the VLA to be closest to the ambient cloud velocity (4 km/s) were also coincident (within VLA positional errors amounting to about 40 AU at 160pc) with both the cm and mm continuum peaks. Since these masers fall close to the ambient velocity and are coincident with the central continuum source, it is very likely they are associated with an inner shock region where the outflowing material impacts on the dense collapsing shell. This maser feature is always present (Claussen et al 1996) but varies in intensity and complexity on timescales of weeks. We undertook multi-epoch VLBA observations of IRAS 16293-2422 to measure the proper motions of the water masers directly and therefore test the infall-rotation model.  Wootten, Murphy, Marvel, Claussen and Wilking

21. Observations • 10 station VLBA experiment + one VLA for more short spacings • 4 epochs in 1997: July 26, August 23, September 24 and November 8 • Observations of 3C345 were used to calibrate the delay, while the strong maser at 4 km/s was used for initial fringe rate calibration • An iterative phase-only self-calibration procedure was used on the strong maser at 4 km/s to determine the residual phase errors and the resultant corrections were applied to all spectral channels • The calibrated data were edited and then mapped using a cellsize of 90 arcseconds and a robust weight of 1 • Multiple fields were imaged simultaneously at full resolution

22. July 26 Spectra Cross-Power spectra from the LA-PT baseline for all four epochs are shown here. The spectra represent a 5 minute average near source transit. Each epoch has a separate amplitude scale. The vertical line is at the ambient velocity of 4 km/s. Aug. 23 Sept. 24 Nov. 8

23. Observations • Resultant channel RMS noises were 25 mJy/Beam, as expected from apriori sensitivity calculations • A sample contour map of an interesting region ~ 500 mas to the SW of the 4 km/s maser is shown below. Masers in this region were always present in all epochs, but detailed matches between the epochs were difficult to obtain due to the complexity of the distribution.

24. Images Shown below is a plot of the overall maser distribution for the third epoch.

25. Proper Motions Since detailed component matching between epochs was very difficult, a measurement of the distance between the strong maser at 4 km/s and the maser clumps to the SE was made. The resulting plot is shown below. Clearly, the two regions are expanding. This motion is not possible if the masers were in a rotating-infalling disk. The motion necessary to account for the expansion is 75 km/s.

26. Conclusions • Water masers in IRAS 16293-2422 show expansion of 75 km/s • Masers occur quite well collimated • Water masers are currently the best method for sampling the kinematics near YSOs

27. NGC1333: Masers Near Protostars On the left is an optical view (Bally, Devine and Reipurth 1996). These authors noted that the abundance of collisionally excited nebulae in this young cluster required a nearly coeval microburst of star formation. Sandell and Knee (2001) imaged the region in the submillimeter, locating 33 dense clumps. In such a crowded environment, the source of the flows has at times been uncertain; VLBA precision measures proper motions to pinpoint origins. Marvel, Wootten, Claussen and Wilking

28. Proper Motion of Water Masers Near NGC1333-SVS13 • SSV13 is associated with the millimeter continuum SED Class I source SSV13A1. • High resolution CO observations have secured the association of the flow with the continuum object on arc-second scales. • A 1998 Aug 12 VLA observation places the blueshifted masers within 80 AU (0''.2) of the 2.7 mm position for A1 reported from BIMA. • Here we report VLBA observations toward the region of NGC1333 near SSV13, the driving source for the well-known Herbig-Haro objects HH7-11. • Maser emission was observed over four epochs spaced interstitially by three weeks during late 1998, • We report observations of two groups of masers, one redshifted by about 6 km s-1 and one blueshifted by about 2-3 km s-1, separated by about 100 AU in projected distance along position angle 21 degrees. Alwyn Wootten (NRAO), Kevin Marvel (AAS), Mark Claussen (NRAO), Bruce Wilking (U. Mo.-St Louis)

29. HH7-11 NGC 1333

30. SVS13 - Young Star Cluster A1 B

31. Disks Around Two Stars in SVS13 Cluster 100 AU 100 AU B A1 Webster and Welch 2001

32. Source 1.3 mm Flux 2.7 mm Flux Flux Ratio SVS13 A disk 175 mJy 38 mJy 4.6 SVS13 A envelope 1108 mJy 90 mJy 12.3 SVS13 B disk 206 mJy 48 mJy 4.3 SVS13 B envelope 904 mJy 103 mJy 8.8 Masses in Disks and Envelopes of SVS13 Webster and Welch 2001

34. Proper Motion of Water Masers in NGC1333 SVS13 Water masers observed over four epochs encompassing 50 days. Several of the masers define an arc structure about 5AU in length. This consistently moved at a rate of 0.023 mas/day, or 13.6 km/s. Including the radial velocity offset, a space velocity of 13.7 km/s is calculated at an inclination of 6 degrees from the plane of the sky. These structures apparently represent water emission from interstellar shocks driven by the outflow from SVS13. Masers near SVS13; 1mas=0.34AU Blue Epoch I, Green Epoch III, Blue Epoch IV Wootten, Marvel, Claussen and Wilking

35. The Water Masers of IRAS 4Masers in Context NGC 1333 15 AU Kevin B. Marvel, AAS Mark Claussen Al Wootten, NRAO Color CCD Image by Bally et al.

36. IRAS 4 Background • Located in the active star forming cloud NGC1333, D ~ 350 pc • IRAS 4 is a multiple system • Two dominant class 0 systems, 4A and 4B • Water masers first mapped in 1993 with VLA (Rogers and Gottschalk) • 4A and 4B are cold ( T~30K ) • Age esitmates vary, 4A ~ 500,000 yr. • 4A is more luminous than 4B and has a more extensive outflow • 4A and 4B are separated by about 11,000 AU, P.A. 135o 4A 4B Image from Minchin et al. 1995 10,000 AU

37. IRAS 4…a multiple, multiple Smith et al. (2000) have used SCUBA (and deconvolution) to find that IRAS 4B breaks up into 4B-I, 4B-II and 4C. Estimated masses: 4A ~ 11 Msun 4B-I ~ 6 Msun 4B-II ~ 2 Msun 4C ~ 3 Msun Unclear if 4C is part of the dynamical system. 4C 4A 4B-I 4B-II

38. 4A Polarization in the mm & sub-mm Outflow axis Outflow axis • Akeson et al., linear polzn., |B| ~ 10 mG, arises in very dense (~ 108 cm-3) gas & 2 emission peaks • Minchin et al., 800 mm polzn. from 4A and 4B, direction along ridge connecting the two sources

39. Molecular line study by Blake et al. • Compact CO outflow, approx. perpendicular to the submm 4A “disk” • Dynamical age of CO outflow ~ 1000 yr • Highly variable jet indicated by symmetric clumpy structure • Depletion factors of 10-20 are observed for all molecular species, but abundances are similar to other cores when scaled to the CO abundance • BUT, Jet N-S aligned near origin, shift to NW closer to YSO

40. H2O Single Dish Observations • Claussen et al. 1992 • Observed for about one year on a monthly timescale • Highly variable on this timescale • Results drove VLBI observations to ~3 week intervals

41. IRAS 4A H2O Masers • Two regions separated by 90 AU • 138o Degrees PA • Proper motions detected • Separating at about 68 km/s, 138o E of N…same PA as the IRAS4A-4B axis • Velocity too great to be explained by rotation Diameter of Earth’s orbit L.S.R. V=7.5 km/s Proper Motion = 67.5 km/s L.S.R. V = 10-12 km/s

42. IRAS 4B VLBI Observations • 4 epochs total, 2 mapped so far, separated by 10 weeks • Two linear emission regions, each about 15 AU in length, less than 2 AU “thick” • The two structures are separated by about 175 AU at a 150o position angle Region 1

43. IRAS 4B VLBI Observations • Proper motions detected, exact one-to-one matching still ongoing • ~ 35 km/s expansion between two regions • Not likely due to orbital motion, too high for estimated mass • Maser structures highly variable Region 2

44. Conclusions • Water masers in IRAS 4A & B associated with outflow, but axis different than large scale outflow • 4B Expansion speed of roughly 35 km/s • 4A Expansion speed of roughly 70 km/s • Difference likely ultimately related to mass difference of YSOs themselves, smaller systems typically have weaker outflows • Highly variable structures, more frequent sampling potentially very useful on YSO sources • Linear maser structures indicate shock regions of roughly 15 AU, thickness < 2 AU

45. Brightens Fades Epoch 4, Field 1 Epoch 1, Field 1

46. Epoch 4, Field 2 Epoch 1, Field 2

47. General Conclusions Formaldehyde and ammonia offer good but differently biassed probes of circumprotostellar material. Neither probes scales smaller than a few hundred AU at current sensitivities. Water masers, though also biassed, are common in primitive stars Water masers probe the inner 100 AU and can provide proper motion information Expansion speeds are measured at 15 - 70 km/s--between those measured from CO on large scales and those measured via optical tracking of HH objects. Water masers are in flows nearly in the plane of the sky, and are well collimated Linear maser structures have been identified extending perhaps 15 AU in extent of unresolved (<2AU) width; their motions can be followed with time over weeks. Some theories of flow acceleration (e.g. X wind theory of Shu and Glassgold) remain viable.