Proper Motions of large-scale Optical Outflows Fiona McGroarty, N.U.I. Maynooth ASGI, Cork 2006

Talk Outline Introduction to star formation and the outflow phase Parsec-Scale Outflows: Outflows – What is their function? How do we “see” them? RESULTS : Examine tangential velocity of the HH objects in the CTTS - driven outflows RESULTS : Parsec-scale outflows from Classical T Tauri stars (CTTS) with microjets Observations

Star Formation Process HR Diagram

Outflow Infalling Envelope Accretion Disk Bipolar outflows remove excess angular momentum from the forming star (a) Cores collapse under gravity (b) Protostar and disk form in centre (c) Bipolar outflow forms  to disk (d) Infall and outflows stop; star is formed. Outflows: Functions Direct optical observations of the star are often impossible but we can observe some of the phenomenon that accompany star formation e.g. outflows

Outflows: Observations Outflows are observed by their interaction with the ambient medium. When optically visible these shocks are known as Herbig-Haro objects Outflows are mainly observed in lines from  CO, H 2, optical and various atomic species  CO traces the ambient molecular gas  H 2 traces low velocity shocked emission  Optical traces high velocity shocked emission Observe HH shocks in: [OIII], [SII] and H  HH emission is due to radiative shocks Shock velocities vary from tens (  50 kms -1 ) to hundreds of kms -1 HH [SII]

Structure of Outflows Knots with “empty space” further out Jet (~ continuous flow of emission) close to source Only in the past 10 years that we have Realised that outflows can extend for many parsecs Can outflows be larger than their parent cloud? 1pc ~ 3 X km ~ 3.26 light years ~ AU

Observations: INT Telescope All observations were taken using the Wide Field Camera (WFC) on the Isaac Newton Telescope, La Palma. The WFC consists of four 2048 X 4100 pixel CCDs. Each pixel projects to 0.33 ’’ on the sky. CCDs are aligned to form an approximate square 34 ’ in size. This is a large enough field of view to find parsec scale outflows, with high enough resolution (0.33 ” ) to see their structure.

Importance of parsec-scale outflows  - Morphology can be used to determine the mass-loss history of the source - Outflows are related to accretion so can deduce if similar accretion rates for different stellar masses (similar star formation process?) - Are a possible source of turbulence in the parent cloud - May have a significant effect on subsequent star formation in their vicinity   Typical sources are low-mass, embedded young (forming) stars  Here, look at sources that are not usually associated with parsec-scale outflows – Are parsec-scale outflows ubiquitous?

Classical T Tauri Stars  More evolved, low-mass stars - Classical T Tauri Stars (CTTS)  Accretion decreases with age, does outflow activity decrease?  Previously known to be the sources of “microjets” of ~5 ’’ - 40 ’’  Looked at 5 sources – CW Tau, DG Tau, DO Tau, HV Tau C and RW Aur

McGroarty & Ray 2004, A&A, 420, 189 Morphologically : HH826, HH827 and HH829 are extensions of the CW Tau outflow, making it 1pc (24 ’ ) in length. The previously known length of the HH220 jet was ~12 ’’ The curving inverted “S” shape of the assumed outflow is a trend often seen in parsec-scale outflows from Class I YSOs. The fact that HH827 and HH829 are symmetrically located about CW Tau seemed to strengthen the idea that they are extensions to this outflow. However my kinematical studies show that HH829 is not driven by CW Tau….. CW Tau

McGroarty, Ray, Froebrich, in preparation Kinematical studies show HH826 to be driven by CW Tau and if precession is present HH827 is also part of this outflow For the 5 CTTS-driven outflows observed: Lengths: between 0.3 and 0.5 pc  dyn : is of the order of 10 3 yr Outflow lengths are comparable to the size of the parent cloud – outflows have “blown out” However these studies show that HH828 and HH829 are not driven by CW Tau This reduces the length of this outflow to ~ 0.3pc

Kinematical studies of the CTTS-driven outflows show:  velocity of micro-jets to be ~200 km/s  velocity of distant objects to also be ~ 200 km/s  Is the outflow velocity at the source decreasing over time or does the velocity of the outflow remain approximately constant over these large distances? CW Tau McGroarty, Ray, Froebrich, in preparation Need larger data sample and numerical simulations to answer this question

CTTS : Conclusions  Optical evidence for outflows of the order of 0.5pc from from more evolved, classical T Tauri stars  These outflows have similar degree of collimation as parsec-scale outflows from younger low-mass sources (Class I) i.e. collimation remains high as the source evolves over ~ 1Myr  Outflow lengths are comparable to parent size cloud  “blow out”  Caution is needed when using the apparent alignment of HH objects to derive their sources. However in the absense of kinematical studies it is still the best means of finding potential driving sources  Velocities of ~200 kms -1 are found for the more distant objects, i.e. velocity remains high at large distances from the source