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F. O. Alves G. A. P. Franco Physics Departament , ICEX, UFMG, Belo Horizonte, Brazil

The infrared void in the Lupus dark clouds revisited: a polarimetric approach (Alves & Franco, 2006). F. O. Alves G. A. P. Franco Physics Departament , ICEX, UFMG, Belo Horizonte, Brazil. Lupus dark clouds and Lupus 1. Optical extinction: Cambresy, 1999. 100 m IRAS emisison. Main purposes.

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F. O. Alves G. A. P. Franco Physics Departament , ICEX, UFMG, Belo Horizonte, Brazil

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  1. The infrared void in the Lupus dark clouds revisited: a polarimetric approach(Alves & Franco, 2006) F. O. Alves G. A. P. Franco Physics Departament, ICEX, UFMG, Belo Horizonte, Brazil

  2. Lupus dark clouds and Lupus 1 Optical extinction: Cambresy, 1999 100 m IRAS emisison

  3. Main purposes • Starlight polarization by dust to improve the distance to the low-mass star forming cloud Lupus 1 • Confirm the existence of a low emission region towards the cloud complex. • Describe the solar neighborhood and, particularly, the Loop 1-Local Bubble interface

  4. Instrumentation • B-band CCD polarimetry (8’ x 8’) IAG 0.60m telescope Polarimetric unit (Magalhães et al, 1996)

  5. Observational technique • 44 nights from 2001 to 2005 at Observatório do Pico dos Dias (LNA/MCT, Brazil). • 131 Hipparcos stars with trigonometric parallaxes H ≥ 4mas (≤ 250 pc). • Selection criterion: /H ≤ 1/3 • Calibration targets: polarized and unpolarized standart stars (<Q> ~ -0.007 and <U> ~ -0.006 per cent small instrumental polarization).

  6. Standart stars

  7. The parallax-polarization diagram Lupus 1 and surroundings

  8. The parallax-polarization diagram Low emission region (cavity)

  9. The polarization map

  10. Comparison to previous work Colour excess data by Franco, 2002

  11. Results • Distribution of linear polarization as a function of distance shows the same pattern found for the reddening-distance diagram; • Parallax-polarization diagram indicates low polarization values up to 130-150 pc, where the dust associated to Lupus 1 may be responsible for the sharp increasing in the polarization values; • Reddening- and polarization- distance diagrams suggest the existence of a region cleaned from dust in the Lupus dark clouds; • Material associated to the Loop 1-Local Bubble interface may be at 60-100 pc.

  12. Pipe nebula Distance from the Sun: 145 ± 16 pc (Alves & Franco, in preparation).

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