Young Stellar Population in the Lupus 3 Molecular Cloud

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Young Stellar Population in the Lupus 3 Molecular
Cloud

• Ya-Ting Jhang, W. P. Chen, Wen Shan Hsiao, F. Y.
  Huang Chien-Hui Kao

Graduated Institute of Astronomy, National Center
University, Taiwan
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Introduction

• The Lupus Molecular Cloud Complex
• One of the nearest SFRs.
• 13x 25 centered at (l,b) (340, 15),
  including nine subgroups, designated as Lupus 1-
  9 (Hara 1999).
• Distance 150 pc (Krautter 1991)
• Total mass 1.7x 104 M?
• (Tachihara et al. 2001, 12CO survey).
• Many kinds of star formation modes
• ?Lupus 3 (Schartz 1977 Hughes et al. 1994
  Nakajima et al. 2000)
• Isolated star formation ? Lupus1
• No star formation ? Lupus 5.

The integrated intensity map of 12CO by Tachihara
et al. (2001), showing the distribution of
molecular clouds in the Lupus SFR.
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• The Lupus 3 Cloud
• Filamentary dark cloud
• M13CO 300 M? (Tachihara et al. 1996).
• High star formation efficiency of 3.8 (Tachihara
  et al. 1996).
• The most active cloud in this region
• gt 65 known T Tauri stars (e.g. Schwartz 1977
  Krautter 1991 Hughes et al. 1994)
• Tachihara (2002) suggested (by 18CO survey)
• Head-tail structures
• cluster-forming cores two Ae stars are located
  in the heads.
• The external shock interaction is suggested to
  form the cloud structures and trigger cluster
  formation.

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The integrated intensity map of the Lupus 3 cloud
in 13CO clouds in contours and gray scale.
Crosses and circles are associated pre-main
sequence stars and protostellar IRAS point
sources, respectively (Tachihara et al. 2002)
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Archival Data

• UK Schmidt Telescope Sky Survey (UKST)
• Southern Galactic Plane and Magellanic Clouds,
  ended in late 2003
• Filters (in narrow band) -- Ha and Short-Red (SR)
• High resolution 1 arcsec
• High sensitivity ? 5 Rayleighs.
• Photographic plates then digitized SuperCosmos
  Ha Survey (SHS)
• Two Ae stars (HR5999 and HR6000) near the center
  of the cloud
• Two Micron Sky Survey
• Large survey area 70 of the sky
• Near-infrared survey (Neugebauer Leighton 1969)
  
• 3 near-infrared bands J (1.25 µm), H (1.65 µm)
  and Ks (2.17 µm)

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Young Stars in Molecular Clouds

• Classical T Tauri stars are known to show
• H-alpha in emission (cf. objective-prism survey
  by Schwartz 1977) from the chromosphere and the
  boundary layer
• Near-infrared excess due to dust thermal emission
• X-ray emission (Feigelson and Montmerle 1999)
  from coronal heating
• Our Study
• To combine both the UKST H-alpha and the 2MASS
  data to identify young stellar objects, i.e. T
  Tauri stars, previously unrecognized outside of
  molecular clouds

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• NIR excess
• Select sources with (J-H) and (H-Ks) colors
  consistent with those of CTTSs.
• Carbon stars might blend with our sources.

The 2MASS JHK color-color diagram for 2MASS
sources ( mark as black point) in the Lupus 3
field. The solid line are main-sequence, giant
and dwarf loci, respectively (Bessell Brett
1988). The dash blue lines bracket the reddening
band (Rieke Lebofsky 1985). The red dot line
is the unreddened CTTS locus (Meyer et al. 1997).

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• Ha stars
• a. ltHagt image Ha line Continuum ltSRgt
  Continuum
• b. ltHagt - Scaled ltSRgt Ha line emission
• d. Scaling factor chosen so that non-Ha stars
  have null line emission

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Caution!! The TiO band may contaminate and
suppress the counts of Short Red, causing
seemingly higher counts of Ha
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List
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SHS Ha image, centered around the two Ae stars
(HR5999 and HR6000). The CTTSs are seen
preferentially to the north of the molecular
cloud.
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Spectroscopy with the CTIO 1.5 m telescope
The spectrum for Sz 96, a known CTTS with strong
Ha in emission.
The spectra of stars 33 and 43. In each case, Ha
is seen in emission.
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Conclusions

• The Ha image archive such as the UKST/SHS is
  useful to find emission-line stars. Our pilot
  study on the Lupus 3 cloud reveals prominent
  H-alpha stars consistent with previously known
  CTTSs in the region.
• Combining with near-infrared excess (2MASS), one
  can identify effectively young stars, e.g.,
  CTTSs, in star-forming regions, in particular on
  larger scales outside the densest parts of the
  cloud to obtain a more comprehensive sample of
  young stellar population.
• We plan to extend the study to a larger coverage
  of Lupus 3, of other Lupus clouds, and of other
  molecular clouds.
• We also plan to use digital H-alpha archive,
  e.g., IPHAS.

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Thank You For Listening
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IPHAS

• The INT Photometric Ha survey of the Northern
  Galactic plane (-5 ?b ?5)
• Provide large-scale Ha imaging surveys, in Ha, r
  and i filters.
• IPHAS point sources
• compact planetary and symbiotic nebulae rapidly
  evolving post-AGB stars
• luminous blue variables
• Be stars of all types
• dMe stars clusters of T Tau stars
• a range of interacting binary stars (symbiotics,
  supersoft' compact binaries
• H-rich white dwarfs
• large numbers of near main sequence A stars
• M giants

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• The Wide Field Camera (WFC) on the 2.5-metre
  Isaac Newton Telescope (INT).
• Magnitude range 13 ? r ? 19.5
• Initial Data Release (IDR) is archived on-line in
  December 2007.
• A photometric catalogue
• more than 200 million objects coupled with
  associated imaging data covering about 1700
  square degrees three colours.
• IPHAS will be followed in the next few years by a
  survey of the southern Galactic Plane on the VLT
  Survey Telescope (VST) using OmegaCam.

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This is a false-colour composite constructed from
the IPHAS images. The colour scheme is red for
Ha, blue for the Sloan r band, and green for
Sloan i. (Image prepared by Mike and Jonathan
Irwin)
This figure is a schematic representation of the
(r'-Ha, r'-i') colour-colour plane that IPHAS
data define. The points plotted on it are the
IPHAS colours of already known objects falling
into the object classes specified in the key. The
figure is from Corradi et al. 2008.
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The following table shows the survey parameters
and quality summary of the IDR