Transcript Star Formation in Lynds Dark Nebulae

Star Formation in Lynds Dark
Nebulae
Ashley Peter, Willly Wassmer,
Rose Haber
Abstract
Dust is found everywhere in the universe, dating back to nearly the
beginning of time (Yan, 05). Dust found in molecular clouds is crucial to the star
formation process, as it allows gas to condense into pre-stellar cores and evolve into
YSOs, or young stellar objects (Greene, 01). Research by Carballo (1992) identified
new candidate YSOs in Scorpio-Centaurus Lupus, which was later confirmed by
Connelley (2007), along with Padgett’s (2008) findings of over 300 YSOs in
Ophuichus. In 1962, Beverly Lynds undertook a survey of dark nebulae and
determined their locations and opacities (Lynds, 62). In this study, two small, isolated,
dark molecular clouds, Lynds Dark Nebulae 425 and 981, which may contain areas of
star formation and YSOs, were observed using the Spitzer Space Telescope in IRAC
(3.6, 4.5, 5.8, and 8 microns) and MIPS (24 microns). The purpose was to obtain
more data about known YSOs and find candidate YSOs. Using infrared images taken
by Spitzer accessed through the Leopard software, mosaics were made using
MOPEX, and candidates were found through certain criteria. Fluxes were calculated
using APT, were converted to magnitudes using a generated Excel spreadsheet, and
SEDs (Spectral Energy Distributions) and color-color plots were constructed and
compared to those of YSOs.
Need
Dust is found
everywhere in the
universe, dating
back to nearly the
beginning of time
(Yan, 05).
http://www.iras.ucalgary.ca/~volk/figs/disk2.jpg
Knowledge Base
Why infrared?
Galaxies at Many Wavelengths:
Near IR
Visible
X-ray
UV
2MASS,
HST
Chandra GALEX,HST
Spitzer
2 nm
200nm
1.5x106K
14,500K
Black Hole
Hot stars =
accretion disks young stars
500nm
5800K
Run of the
mill stars
(all ages)
Far IR
Spitzer
1600nm
100,000nm
1800K
29K
Very cool stars Cool dust (usually old)
heated by hot
stars
Spitzer Telescope
(October 2000)
(IRAC)
(MIPS)
Lynds 1014
Visible
600 LY away
IR
Lynds 425 and 981
Infrared images of LDN 425 (left) and
LDN 981 (right).
Formation of a low mass star
Class 0
Class II
Class I
Class III
Greene, American Scientist, Jul-Aug 2001
Class 0
Main accretion phase?
Menv>~0.5 Msun
<~104 years
Class I
Late accretion phase?
Menv<~0.1 Msun
~105 years
Class II
Optically thick disk
Avg Mdisk~0.01 Msun
~106 years
Class III
Optically thin disk
Avg Mdisk<~0.003 Msun
~107 years
IRAC Color-Color Diagrams
Class I (envelope)
models
Av =30
Class II (disk) models
Allen et al. 2004
Literature Review
Carballo, R et al. “Identification of IRAS Point Sources in
Scorpio-Centaurus Lupus.”
184 sources from IRAS Point
Sources Catalog
Photometry
Classification- identify YSOs
Rebull, L.M. et al. “Spitzer Observations of Young Stars in the
Witch Head Nebula (IC 2118).”
Spitzer/IRAC and MIPS
observations- March 05/06
Photometry, mosaics
created- MOPEX
SEDs and color-color
plots
Connelley, Michael et al. “Infrared Nebulae Around Young Stellar Objects.”
IRAS Point and Faint Source
Catalogs
Class I YSOs
SEDs
Padgett, D et al. “The Spitzer C2D Survey of Large, Nearby, Interstellar
Clouds: VII. Ophiuchus Observed with MIPS.”
MIPS observations of
Ophiuchus- 14.4 square
degrees
Flux densities converted
to magnitude
BCD’s mosaicked- MOPEX
Color-color and colormagnitude diagrams
Purpose
The purpose of this study is to obtain more data
about known YSOs (young stellar objects) and
find more candidate YSOs.
Hypotheses
• H(o)- LDN 425 and LDN 981 are areas
of young star formation
• H(a)- star formations do occur in LDN
425 and 981, YSOs will be found
Methodology
Obtained images from the Spitzer Space Telescope on
Lynds Dark Nebulae 425 and 981 (Leopard)
Mosaics of LDN 425
made (MOPEX)
Mosaics of LDN 981
made (MOPEX)
Searched for candidates within clouds using
criteria such as infrared excess
Fluxes of candidates calculated using
APT (Aperture Photometry Tool)
Using Excel the fluxes were converted
into magnitudes
Using these values SEDs (spectral energy
distributions) and Color-Color plots were made to
compare the YSO candidates to known YSOs.
Bibliography
Carballo, R et al. “Identification of IRAS Point Sources in Scorpio-Centaurus
Lupus.” Astronomy & Astrophysics. 1 April 1992. Pages 106-124.
Connelley, Michael et al. “Infrared Nebulae Around Young Stellar Objects.” The
Astrophysical Journal. 20 November 2006.
DeWolf, Chris et al. “Star Formation in Lynds Dark Nebulae.” 2008.
Greene. “Star Formation.” American Scientist, July-August 2001.
Kun, M. “Star Formation in L1199.” Kluwer Academic Publishers. 1995.
Lynds, Beverly T. “Catalogue of Dark Nebulae.” American Astronomical Society. NASA
Astrophyiscs Data System. 29 January 1962.
Padgett, D et al. “The Spitzer C2D Survey of Large, Nearby, Interstellar Clouds: VII. Ophiuchus
Observed with MIPS.” The Astrophysical Journal. 21 September 2007.
Quanz, S.P. “Dust Rings and Filaments Around the Isolated Young Star V1331 Cygni.” The
Astrophysical Journal. 26 October 2006. Pages 1-15.
Rebull, Luisa M. “Studying Young Stars.” 20 November 2007.
<https://coolwiki.ipac.caltech.edu/index.php/Studying_Young_Stars>
Rebull, Luisa M. et al. “Spitzer Observations of Young Stars in the Witch Head Nebula (IC 2118).”
2007 AAS/AAPT Joint Meeting, Bulletin of the American Astronomical Society, Vol. 38, p.
1053. December 2006.
Rho, J. et al. “Freshly Formed Dust in the Cassiopeia A Supernova Remnant as Revealed by the
Spitzer Space Telescope.” Astrophysical Journal. 18 September 2007.
Sartori, M. “The Star Formation Scenario in the Galactic Range from Ophiuchus
to Chamaeleon.” Instituto Astronômico e Geofísico. July 2000.
Wilking, B.A. “Star Formation in the Ophiuchus Molecular Cloud Complex .” The Astrophysical
Journal. Page 159. 1992.
Yan, Lin et al. “Spitzer Detection of PAG and Silicate Dust Features in the Mid-Infrared Spectra of
z 2 Ultraluminous Infrared Galaxies.” The Astrophysical Journal. 14 April 2005. Pages 1-22.