* Astronomy

Blobrana · L

RE: Himiko

Blobrana · L

NASAs Hubble and Spitzer space telescopes along with ALMA telescope find trio of Young Galaxies Merging

Astronomers using the combined power of the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile and NASA's Hubble and Spitzer space telescopes have discovered a far-flung trio of primitive galaxies nestled inside an enormous blob of primordial gas nearly 13 billion light-years from Earth.
Its possible the trio will eventually merge into a single galaxy similar to our own Milky Way.
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Blobrana · L

Title: An Intensely Star-Forming Galaxy at z~7 with Low Dust and Metal Content Revealed by Deep ALMA and HST Observations
Authors: Masami Ouchi, Richard Ellis, Yoshiaki Ono, Kouichiro Nakanishi, Kotaro Kohno, Rieko Momose, Yasutaka Kurono, M. L. N. Ashby, Kazuhiro Shimasaku, S. P. Willner, G. G. Fazio, Yoichi Tamura, Daisuke Iono

We report deep ALMA observations complemented with associated HST imaging for a luminous (m_uv=25) galaxy, 'Himiko', at a redshift z=6.595. The galaxy is remarkable for its high star formation rate, 100 solar masses/yr, securely estimated from our deep HST and Spitzer photometry, and the absence of any evidence for strong AGN activity or gravitational lensing magnification. Our ALMA observations probe an order of magnitude deeper than previous IRAM observations, yet fail to detect a 1.2mm dust continuum, indicating a flux <52uJy comparable with or weaker than that of local dwarf irregulars with much lower star formation rates. We likewise provide a strong upper limit for the flux of [CII] 158um, L([CII]) < 5.1x10^7 Lo, a diagnostic of the hot interstellar gas often described as a valuable probe for early galaxies. In fact, our observations indicate Himiko lies off the local L([CII]) - star formation rate scaling relation by a factor of more than 30. Both aspects of our ALMA observations suggest Himiko is an unique object with a very low dust content and perhaps nearly primordial interstellar gas. Our HST images provide unique insight into the morphology of this remarkable source, highlighting an extremely blue core of activity and two less extreme associated clumps. We are likely witnessing an early massive galaxy during a key period of its mass assembly close to the end of the reionisation era. Himiko is undergoing a triple major merger event whose extensive ionised nebula of Lyman alpha emitting gas, discovered in our earlier work with Subaru, is powered by star formation and the dense circum-galactic gas.

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Blobrana · L

Title: A deep search for CO J=2-1 emission from a Lyman-Alpha blob at z~6.595
Authors: Jeff Wagg, Nissim Kanekar

We have used the Green Bank Telescope to carry out a deep search for redshifted CO J=2-1 line emission from an extended (>17 kpc) Ly-Alpha blob (LAB), "Himiko", at z~6.595. Our non-detection of CO J=2-1 emission places the strong 3-sigma upper limit of L'_CO < 1.8x10^10 x sqrt(dV/250) K km/s pc^2 on the CO line luminosity. This is comparable to the best current limits on the CO line luminosity in LABs at z~3 and lower-luminosity Lyman-Alpha emitters (LAEs) at z>~6.5. High-z LABs appear to have lower CO line luminosities than the host galaxies of luminous quasars and sub-mm galaxies at similar redshifts, despite their high stellar mass. Although the CO-to-H2 conversion factor is uncertain for galaxies in the early Universe, we assume X_CO = 0.8 solar masses (K km/s pc^2)^-1 to obtain the limit M(H_2) < 1.4 x 10^10 solar masses on Himiko's molecular gas mass; this is a factor of >2.5 lower than the stellar mass in the z~6.595 LAB.

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