Near infrared spectrophotometry of carbon stars from the irts to dome c
1 / 24

Near-infrared spectrophotometry of carbon stars : from the IRTS to dome C - PowerPoint PPT Presentation

  • Uploaded on

T. Le Bertre 1 , M. Tanaka 2,3 , I. Yamamura 2 , H. Murakami 2 , D.J. MacConnell 4 , A. Guertin 1,5 1 Paris Observatory, France 2 Institute of Space and Astronautical Science, Japan 3 National Astronomical Observatory, Japan

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Near-infrared spectrophotometry of carbon stars : from the IRTS to dome C' - lotus

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Near infrared spectrophotometry of carbon stars from the irts to dome c l.jpg

T. Le Bertre1, M. Tanaka2,3, I. Yamamura2,

H. Murakami2, D.J. MacConnell4, A. Guertin1,5

1 Paris Observatory, France

2 Institute of Space and Astronautical Science, Japan

3 National Astronomical Observatory, Japan

4 Computer Sciences Corporation/Space Telescope Science Institute, USA

5 University of Montréal, Canada

Near-infrared spectrophotometry of carbon stars: from the IRTS to dome C

ARENA conference, Paris, 14-16 June 2006

Introduction l.jpg

Carbon stars are characterized by the presence of carbon molecules such as C2 or CN. The enrichment in carbon may occur when they evolve on one of the giant branches or may be due to mass transfer from a more evolved companion.

Inventories of cool carbon stars are of special interest because these objects can be used to trace matter at large galactocentric distances out to the Magellanic Clouds.

Carbon stars contribute to the replenishment of the ISM.

We will examine the potential for finding and characterizing carbon stars by using near-infrared spectrophotometric surveys. For that purpose, we use the data provided by the Japanese space experiment IRTS.

The irts l.jpg

The InfraRed Telescope in Space (IRTS) is a 15 cm diameter telescope operated in space which surveyed ~ 7 % of the sky in two strips, one along the galactic plane and the other covering the high galactic latitude region (Murakami et al., 1996, PASJ 48, L41).

The 2 strips covered by the IRTS in galactic coordinates

Slide4 l.jpg

The IRTS was equipped with four scientific instruments operating in parallel: the Near-InfraRed Spectrometer (NIRS; 1.4-4.0 µm), the Mid-Infrared Spectrometer (MIRS; 4.5-11.7 µm), the Far-Infrared Line Mapper (FILM; 145, 155, 158, 160 µm), and the Far-InfraRed Photometer (FIRP; 150, 250, 400, 700 µm). Most wavelengths observed by IRTS are blocked by the Earth's atmosphere and cannot be observed with ground-based telescopes.

The nirs l.jpg
The NIRS operating in parallel:

The Near-InfraRed Spectrometer (NIRS) is a low-resolution grating spectrophotometer (Noda et al., 1994, ApJ 428, 363). A 12 x 2 channel InSb detector array covers two wavelength ranges, 1.4-2.5 and 2.8-4.0 µm, with a spectral resolution ranging from ~20, at short wavelengths, to ~40 at the long wavelength end. The entrance aperture was 8 arcmin by 8 arcmin on the sky.

More than 14 000 point sources have been detected. Their spectra can be accessed via the DARTS archive



Mass losing carbon stars can be easily identified from the deep absorption band at 3 1 m l.jpg

T Lyr, CGCS 4038 operating in parallel:

Mass losing carbon stars can be easily identified from the deep absorption band at 3.1 µm.

NIRS spectra of

cool carbon stars show

molecular absorptions at

1.4 µm (CO + CN),

1.8 µm (C2),

2.3 µm (CO),

3.1 µm (C2H2+HCN) and

3.8 µm (C2H2).

Mass losing m and c agb stars can be easily separated with infrared spectrophotometry l.jpg
Mass-losing M and C operating in parallel: AGB stars can be easily separated with infrared spectrophotometry.

By contrast, NIRS spectra

of late-type, oxygen-rich stars show only CO and H2O bands,

in particular at 1.9 µm.

increasing depth of the 3.1 µm feature

Le bertre et al 2005 pasp 117 199 l.jpg
Le Bertre et al., 2005, PASP 117, 199 operating in parallel:

We have identified 139 cool carbon stars in the NIRS survey of the IRTS from the conspicuous presence of molecular absorption bands at 1.8, 3.1, and 3.8 µm (Le Bertre et al., 2005). Among them, 14 are new, bright (K ~ 4.0-7.0) carbon stars; two such cases are shown below. Some dusty carbon stars, like NIRS 07036-2221, can only be revealed by infrared surveys.

Le bertre et al 2003 a a 403 943 l.jpg
Le Bertre et al., 2003, A&A 403, 943 operating in parallel:

The IRTS data show a clear spatial separation in the Galactic Plane between mass-losing, oxygen-rich stars and mass-losing, carbon stars, with the former (dots) outnumbering the latter (diamonds) for rGC< 8 kpc, and the reverse for rGC> 10 kpc.

Slide10 l.jpg

ISO/ SWS: 3-8 µm; operating in parallel: R ~200-1000

Aoki et al. 1999, IAUS 191, 175

Slide12 l.jpg

Y CVn; KAO operating in parallel:

CN bandhead @1.40 µm

C2 bandhead @1.77 µm





Goebel et al. 1980, ApJ 235, 104

Slide13 l.jpg

IRTS/ NIRS operating in parallel: : UV Cam; CGCS 177 (R8)

CN bandhead @1.40 µm


C2 bandhead @1.77 µm



Le Bertre et al. 2005, PASP 117, 199

Slide14 l.jpg

  • Infrared spectrophotometry in the range 1-4 µm is an important tool to identify and characterize late-type stars.

  • Since the IRTS there has been no other near-infrared spectrophotometric survey, although integral-field techniques and large-scale panoramic detectors are now available in this wavelength range.

  • We suffer (and may suffer for some time) from a gap in our vision of the Universe, that is general, i.e. not specific to carbon star studies.

Slide15 l.jpg

Allard (2001)

+ possibility of

synthesizing numerically

photometric bands/combs

Slide16 l.jpg

For galactic carbon stars important tool :

  • We need to cover as continuously as possible the spectral range from 1.5 (1.2 / CN) µm to 3.6 (4.0 / C2H2) µm.

  • with a spectral resolution >50 (100).

  • We need to survey large areas of the sky in different galactic directions (l and b) + MCs, etc.

Slide17 l.jpg

Request important tool :

An atmospheric transmission (and if possible emission during day and night) from Concordia in the range 1.2-4.1 µm, in order to determine which part of the spectrum can be accessed from dome C.

Suggestion :

An integral-field spectro-imager, R ~ 80-100, operating from

1.2 to 4.0 µm that would allow to explore an area that has

been barely touched by the IRTS.

Slide18 l.jpg

Spectrophotometric imaging surveys: important tool

 General resource for the study of stars, stellar structures and ISM

  • late-type stars / PNs in the Galaxy and nearby galaxies

  • Galactic plane; Magellanic Clouds

  • ISM (Pa , UIBs, …)

  • Star forming regions (Chamaeleon, ...)

  • Galactic halo (galactic pole)

  • etc.

Slide21 l.jpg

L’ important tool





H20 = 1mm; 1 ai

Modelled atmospheric transmission from Antarctica “dome C”

(Epchtein 2005)

Le bertre et al 2005 pasp 117 19922 l.jpg
Le Bertre et al., 2005, PASP 117, 199 important tool

NIRS 07036-2221

For the IRTS carbon stars, we find a trend relating the 3.1 µm band strength to the K-L’ color index, which is known to correlate with mass-loss rate.

NIRS 07037-2326

The 14 new carbon stars are represented by a ‘ ’

Discussion l.jpg
Discussion important tool

  • Winters et al. (2000, A&A 361, 641) have shown that mass loss from red giants is favored by a low stellar effective temperature, a low stellar mass, a high luminosity, and a large pulsation amplitude. Loidl et al. (1999, A&A 342, 531) have shown that the strengths of the C2H2 and HCN features follow these same trends because these molecules form preferentially at low temperature in the upper stellar atmosphere.

  • However, the correlation breaks down for large mass loss rates due to the effect of dust emission filling in the 3.1 µm feature.

Conclusion l.jpg
Conclusion important tool

  • Infrared spectrophotometry is an important tool to identify and characterize late-type stars.

  • Sensitive, near-infrared spectrophotometric surveys covering the range from ~1.5 to ~4.5 µm with a spectral resolution > 40 have the potential to reveal new carbon stars in the Galaxy and in its satellites and to provide useful information on their physical properties.