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19 April 2024 |
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A near-infrared excess in the continuum of high-redshift galaxies: a tracer of star and planet formation? | | E. Mentuch
; R.G. Abraham
; K. Glazebrook
; P.J. McCarthy
; H. Yan
; D.V. O'Donnell
; D. Le Borgne
; S. Savaglio
; D. Crampton
; R. Murowinski
; S. Juneau
; R. G. Carlberg
; I. Jorgensen
; K. Roth
; H. Chen
; R.O. Marzke
; | | Date: |
7 May 2009 | | Abstract: | A broad continuum excess in the near-infrared, peaking in the rest frame at
2-5 micron, is detected in a spectroscopic sample of 88 galaxies at 0.5<z<2.0
taken from the Gemini Deep Deep Survey. Line emission from polycyclic aromatic
hydrocarbons (PAHs) at 3.3 micron alone cannot explain the excess, which can be
fit by a spectral component consisting of a template of PAH emission lines
superposed on a modified blackbody of temperature T~850 K. The luminosity ratio
of this near-infrared excess emission relative to the galaxy’s stellar emission
at 3 micron is found to be related to the specific star formation rate of the
galaxy, suggesting that the rest-frame J-L color can potentially be used as a
sensitive and nearly extinction-free tracer of star-formation. The origin of
the near-infrared excess is explored by examining similar excesses observed
locally in massive star forming regions, reflection and planetary nebulae,
post-AGB stars and in the galactic cirrus. We conclude that the most likely
explanation for the 2-5 micron excess is the contribution from circumstellar
disks around massive young stellar objects seen in the integrated light of
high-redshift galaxies. Assuming circumstellar disks extend down to lower
masses, as they do in our own Galaxy, the excess emission presents us with an
exciting opportunity to measure the formation rate of planetary systems at
earlier cosmic epochs, at a time when our own Solar System formed. | | Source: | arXiv, 0905.0910 | | Services: | Forum | Review | PDF | Favorites | |
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