AMI-LA radio continuum observations of low mass young stars: target sample for e-MERLIN legacy project

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AMI-LA radio continuum observations of low mass
young stars target sample for e-MERLIN legacy
project

• Rachael Ainsworth
• Dublin Institute for Advanced Studies
• YERAC 2011

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Introduction

• 16 GHz radio continuum observations of target
  sample for the e-MERLIN legacy project on the
  morphology and time evolution of thermal jets
  associated with low mass young stars
  (Rodriguez).
• I will draw correlations between the radio
  luminosity and a number of global properties for
  these systems.
• These correlations along with the spectral
  indices for these sources will help place limits
  on the physical mechanisms responsible for the
  radio emission.
• Future work e-MERLIN

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Protostellar Evolution

• Evolutionary Indicators (Hatchell 2007)
• Bolometric temperature
• Class 0 Tbol lt 70 K, Class I 70 lt Tbol lt 150 K
• Ratio of submm to bolometric luminosity
• Lbol/Lsmm gt 3000
• Ratio of Spitzer IRAC to submm emission
• F3.6/F850 gt 0.003

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Bremsstrahlung

• A form of thermal emission that comes from gas
  which has been ionized.
• Atoms in the gas become ionized when their
  electrons become stripped or dislodged.
• This results in charged particles moving around
  in an ionized gas.
• As this happens, the electrons are accelerated by
  the charged particles, and the gas cloud emits
  radiation continuously.
• Often called called "free-free" emission because
  it is produced by free electrons scattering off
  ions without being captured.

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Spectral Indices
Partially optically thick
Optically thick
Optically thin
S? ?2
S? ?0.6
S? ?-0.1
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Emission Mechanisms

• Ionized spherical stellar winds (Panagia Felli
  1975)
• Ionized collimated winds (Reynolds 1986)
• Both models predict a correlation between the
  radio luminosity and the rate of stellar mass
  loss,
• and a 0.6, where a is the spectral index
  defined as

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The Sample
L1448, HH 7-11, L1551, L1527, HH 1-2, HH 26 IR,
HH 111, NGC 2264, Serpens, L723, L1251
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L1448
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HH 7-11
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Results
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Radio Luminosity with Bolometric Luminosity

• (Scaife 2011)
• logL1.8 cm (mJy kpc2) -(1.74 0.18)
  (0.510.26)logLbol(L?)

• logL1.8 cm (mJy kpc2) -1.44
  0.60logLbol(L?)

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Radio Luminosity withEnvelope Mass

• (Scaife 2011)
• logL1.8 cm (mJy kpc2) -(2.23 0.65)
  (0.680.62)logMenv(M?)

• logL1.8 cm (mJy kpc2) -2.26
  1.21logMenv(M?)

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e-MERLIN

• Image the jet launch zone to look for clues as
  to how jets from young stars are generated.
• Measure the strength and direction of the
  magnetic field in the jet launch zone.

• Capabilities include
• Observing bands at 1.3-1.8 GHz, 4-8 GHz, 22-24
  GHz
• Resolution 10 to 150 mas
• Total bandwidth 4 GHz
• Sensitivity 1 µJy
• Astrometry, polarimetry, spectroscopy