Spectroscopic Confirmation of an Extreme Starburst at Redshift 4.547

Research by Peter Capak, C. L. Carilli, N. Lee, T. Aldcroft, H. Aussel, E. Schinnerer, G.W. Wilson, M. S. Yun, A . Blain, M. Giavalisco, O. Ilbert, J. Kartaltepe, K.-S. Lee, H. McCracken, B. Mobasher, M. Salvato, S. Sasaki, K.S. Scott, K. Sheth, Y. Shioya, D. Thompson, M. Elvis, D. B. Sanders, N. Z. Scoville, Y.Tanaguchi

This galaxy, Zw II 96 (about 500 million light-years away) resembles the Baby Boom galaxy which lies about 12.3 billion light-years away and appears in images as only a smudge.

Scientists report the spectroscopic confirmation of a submillimeter galaxy (SMG) (the Baby Boom Galaxy) with an estimated LIR = (0.5 - 2.0) x 1013 L. The spectra, mid-IR, and X-ray properties indicate the bolometric luminosity is dominated by star formation at a rate of >1000 M. Multiple, spatially separated components are visible in the Ly[alpha] line with an observed velocity difference of up to 380 km and the object morphology indicates a merger. The best-fit spectral energy distribution and spectral line indicators suggest the object is 2-8 M years old and contains >1010 M of stellar mass. This object is a likely progenitor for the massive early-type systems seen at z~2. The green and red splotch in this image is the most active star-making galaxy in the very distant universe. Nicknamed "Baby Boom," the galaxy is churning out an average of up to 4,000 stars per year, more than 100 times the number produced in our own Milky Way galaxy. It was spotted 12.3 billion light-years away by a suite of telescopes, including NASA's Spitzer Space Telescope.

Implications

The study of galaxies detected at millimeter and submillimeter wavelengths is one of the most rapidly developing fields in observational astronomy. It is now known that a large fraction of the star formation activity is enshrouded in dust, with the star formation rate (SFR) being directly proportional to the far-infrared (FIR) luminosity of galaxies, modulo possible contributions from an active galactic nucleus (AGN). Surveys performed at millimeter wavelengths directly probe the FIR luminosity, and hence the amount of star formation. Furthermore, the shape of the galaxy spectral energy distributions (SEDs) at rest-frame millimeter wavelengths results in a negative K-correction in the range . Therefore a flux-limited survey is equivalent to an SFR-limited survey at these redshifts (Blain et al. 2002).

Significance to Solar System Exploration

Our Milky Way galaxy produces only about 10 new stars annually. But a galaxy far, far away is experiencing a major baby boom. It is producing more than 4,000 new stars a year, and should become a massive elliptical galaxy. The discovery challenges the accepted model for galaxy formation, which has most galaxies slowly bulking up by absorbing pieces of other galaxies, rather than growing internally. The discovery also fundamentally changes the way astronomers view origins of stars in our solar system, and beyond.

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