A NEAR-INFRARED EXCESS IN THE CONTINUUM OF HIGH-REDSHIFT GALAXIES: A TRACER OF STAR FORMATION AND CIRCUMSTELLAR DISKS?

Journal Article · Tue Dec 01 00:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/706/2/1020· OSTI ID:21378117

Mentuch, Erin; Abraham, Roberto G; Carlberg, R G ^[1]; Glazebrook, Karl ^[2]; McCarthy, Patrick J ^[3]; Yan, Haojing ^[4]; O'Donnell, Daniel V ^[5]; Le Borgne, Damien ^[6]; Savaglio, Sandra ^[7]; Crampton, David; Murowinski, Richard ^[8]; Juneau, Stephanie ^[9]; Joergensen, Inger; Roth, Kathy ^[10]; Chen, H -W ^[11]; Marzke, Ronald O ^[12]

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1. Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON, M5S 3H4 (Canada)
2. Centre for Astrophysics and Supercomputing, Swinburne University of Technology, 1 Alfred St, Hawthorn, Victoria 3122 (Australia)
3. Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
4. Center for Cosmology and AstroParticle Physics, the Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210 (United States)
5. Department of Physics, Ernest Rutherford Physics Building, McGill University, 3600 rue University, Montreal, QC, H3A 2T8 (Canada)
6. Institut d'Astrophysique de Paris, UMR7095, UPMC, Paris (France)
7. Max-Planck-Institut fuer extraterrestrische Physik, Garching (Germany)
8. Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, British Columbia, V9E 2E7 (Canada)
9. Department of Astronomy/Steward Observatory, University of Arizona, 933 N Cherry Ave., Rm. N204, Tucson, AZ 85721-0065 (United States)
10. Gemini Observatory, Hilo, HI 96720 (United States)
11. Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave, Chicago, IL 60637 (United States)
12. Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132 (United States)

A broad continuum excess in the near-infrared, peaking in the rest frame at 2-5 mum, 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 mum 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 approx 850 K. The luminosity of this near-infrared excess emission at 3 mum is found to be correlated with the star formation rate of the galaxy. 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-asymptotic giant branch stars, and in the galactic cirrus. We also consider the potential contribution from dust heated around low-luminosity active galactic nuclei. We conclude that the most likely explanation for the 2-5 mum 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 cosmic epochs before our own solar system formed.

• OSTI ID: 21378117
• Journal Information: Astrophysical Journal, Vol. 706, Issue 2; Other Information: DOI: 10.1088/0004-637X/706/2/1020; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASYMPTOTIC SOLUTIONS
DUSTS
GALACTIC EVOLUTION
GALAXIES
GALAXY NUCLEI
LUMINOSITY
MASS
MATTER
PLANETARY NEBULAE
POLYCYCLIC AROMATIC HYDROCARBONS
PROTOPLANETS
RED SHIFT
SOLAR SYSTEM
STARS
VISIBLE RADIATION
AROMATICS
ELECTROMAGNETIC RADIATION
EVOLUTION
HYDROCARBONS
MATHEMATICAL SOLUTIONS
NEBULAE
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
RADIATIONS