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Post Info TOPIC: RCSGA 032727-132609
Blobrana


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RCS2 032727-132623
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Gravitational lens reveals details of distant, ancient galaxy

Thanks to the presence of a natural "zoom lens" in space, University of Chicago scientists working with NASA's Hubble Space Telescope have obtained a uniquely close-up look at the brightest gravitationally magnified galaxy yet discovered.
The imagery offers a visually striking example of gravitational lensing, in which one massive object's gravitational field can magnify and distort the light coming from another object behind it. Such optical tricks stem from Einstein's theory of general relativity, which describes how gravity can warp space and time, including bending the path that light travels.
In this case, gravity from the galaxy cluster RCS2 032727-132623 bent and amplified the light coming from a much more distant galaxy, 10 billion light-years from Earth.
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Blobrana


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RE: RCSGA 032727-132609
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Title: Source Plane Reconstruction of The Bright Lensed Galaxy RCSGA 032727-132609
Authors: Keren Sharon, Michael D. Gladders, Jane R. Rigby, Eva Wuyts, Benjamin P. Koester, Matthew B. Bayliss, L. Felipe Barrientos

We present new HST/WFC3 imaging data of RCSGA 032727-132609, a bright lensed galaxy at z=1.7 that is magnified and stretched by the lensing cluster RCS2 032727-132623. Using this new high-resolution imaging, we modify our previous lens model (which was based on ground-based data) to fully understand the lensing geometry, and use it to reconstruct the lensed galaxy in the source plane. This giant arc represents a unique opportunity to peer into 100-pc scale structures in a high-redshift galaxy. This new source reconstruction will be crucial for a future analysis of the spatially-resolved rest-UV and rest-optical spectra of the brightest parts of the arc.

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Title: A bright, spatially extended lensed galaxy at z = 1.7 behind the cluster RCS2 032727-132623
Authors: Eva Wuyts, L. Felipe Barrientos, Michael D. Gladders, Keren Sharon, Matthew B. Bayliss, Mauricio Carrasco, David Gilbank, H. K. C. Yee, Benjamin P. Koester, Roberto Muñoz

We present the discovery of an extremely bright and extended lensed source from the second Red Sequence Cluster Survey (RCS2). RCSGA 032727-132609 is spectroscopically confirmed as a giant arc and counter-image of a background galaxy at z=1.701, strongly-lensed by the foreground galaxy cluster RCS2 032727-132623 at z=0.564. The giant arc extends over ~ 38\,\arcsec and has an integrated g-band magnitude of 19.15, making it ~ 20 times larger and ~ 4 times brighter than the prototypical lensed galaxy MS1512-cB58. This is the brightest distant lensed galaxy in the Universe known to date. Its location in the 'redshift desert' provides unique opportunities to connect between the large samples of galaxies known at z~3 and z~1. We have collected photometry in 9 bands, ranging from u to K_s, which densely sample the rest-frame UV and optical light, including the age-sensitive 4000\AA\ break. A lens model is constructed for the system, and results in a robust total magnification of 2.04 ±0.16 for the counter-image; we estimate an average magnification of 17.2 ±1.4 for the giant arc based on the relative physical scales of the arc and counter-image. Fits of single-component spectral energy distribution (SED) models to the photometry result in a moderately young age, t = 115 ± 65\,Myr, small amounts of dust, E(B-V) \le 0.035, and an exponentially declining star formation history with e-folding time \tau = 10-100\,Myr. After correcting for the lensing magnification, we find a stellar mass of \log(solar masses ± 0.1. Allowing for episodic star formation, an underlying old burst could contain up to twice the mass inferred from single-component modelling. This stellar mass estimate is consistent with the average stellar mass of a sample of 'BM' galaxies (1.4 < z < 2.0) studied by Reddy et al. (2006).

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Hubble Zooms in on a Magnified Galaxy

A team of astronomers aimed Hubble at one of the most striking examples of gravitational lensing, a nearly 90-degree arc of light in the galaxy cluster RCS2 032727-132623. Hubble's view of the distant background galaxy, which lies nearly 10 billion light-years away, is significantly more detailed than could ever be achieved without the help of the gravitational lens.
This observation provides a unique opportunity to study the physical properties of a galaxy vigorously forming stars when the universe was only one-third its present age. The results have been accepted for publication in The Astrophysical Journal.
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