The infrared void in the Lupus dark clouds

revisited: a polarimetric approach

(Alves & Franco, 2006)

The infrared void in the Lupus dark clouds

revisited: a polarimetric approach

(Alves & Franco, 2006)

F. O. AlvesG. A. P. FrancoPhysics Departament, ICEX, UFMG, Belo Horizonte, Brazil

F. O. AlvesG. A. P. FrancoPhysics Departament, ICEX, UFMG, Belo Horizonte, Brazil

Lupus dark clouds and Lupus 1

Lupus dark clouds and Lupus 1

Optical extinction: Cambresy, 1999Optical extinction: Cambresy, 1999

100 100 m IRAS emisisonm IRAS emisison

Main purposesMain 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

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

InstrumentationInstrumentation

B-band CCD polarimetry (8’ x 8’)

B-band CCD polarimetry (8’ x 8’)

Polarimetric unit (Magalhães et al, 1996)Polarimetric unit (Magalhães et al, 1996) IAG 0.60m IAG 0.60m telescopetelescope

Observational techniqueObservational 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).

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).

Standart starsStandart stars

The parallax-polarization diagram

The parallax-polarization diagram

Lupus 1 and surroundingsLupus 1 and surroundings

The parallax-polarization diagram

The parallax-polarization diagram

Low emission region (cavity)Low emission region (cavity)

The polarization mapThe polarization map

Comparison to previous work

Comparison to previous work

Colour excess data by Franco, 2002Colour excess data by Franco, 2002

ResultsResults

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.

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.

Pipe nebulaPipe nebula

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