Communiqué de presse
A VLT Spectrum of a Gravitationally Lensed Galaxy
An Arc at z = 3.23 in Galaxy Cluster 1ES 0657-55
27 février 1999
The galaxy cluster 1ES 0657-55 is located in the southern constellation Carina (The Keel), south of the Milky Way band. Its redshift has been measured as z = 0.29. It is a source of strong and very hot X-ray emission and has an asymmetric galaxy distribution, indicating a large mass and recent formation. Images obtained with the ESO 3.6-m New Technology Telescope (NTT) at La Silla have revealed the presence of an arc , i.e. presumably a background galaxy at larger distance, whose image is strongly distorted by the gravitational field of this cluster.
VLT images of 1ES 0657-55
New images of the galaxy cluster 1ES 0657-558 in several colours were obtained by the FORS Commissioning Team in December 1998 under good seeing conditions (0.65 - 0.80 arcsec). Colour composite (eso9919a) and single-band (eso9919b) reproductions are shown here.
Thanks to the excellent image sharpness (the small pixel size provides sufficient spatial sampling), it is obvious that this arc is very thin and long (upper right). Other arcs and arclets are also visible.
The spectrum of the arc
Photo eso9919c displays the spectrum of the most prominent gravitational arc in the galaxy cluster 1ES 0657-558 , as obtained at VLT UT1 with the FORS1 instrument in December 1998. The total exposure time was 1.5 hours. It shows absorption lines of hydrogen (Lyman-alpha and Lyman-beta) as well as lines of silicium, oxygen carbon and iron.
From the measured wavelengths, the redshift of the arc is determined as z = 3.23. An earlier, much less accurate photometric redshift estimate (from the observed colours) is confirmed and refined by this spectral observation.
Star forming galaxies at lower redshifts have very similar spectra. It is therefore concluded that this arc is the gravitationally distorted image of a distant galaxy caught in its formation stage , when the Universe was only about 2 billion (2,000 million) years old.
Outlook
The new FORS data will allow a much more detailed modelling of the gravitational lens and a better estimate of the cluster mass than was possible before.
There are several additional strong lensing features visible in the field. These are probably the images of objects at even higher redshift that are distorted into multiple images or arc(let)s. Follow-up observations with VLT UT1 and the ISAAC instrument with infrared imaging and spectroscopy will be essential in order to achieve an exact determination of the redshifts and corresponding distances of these faint, red arcs.
The foreground cluster magnifies the images of background galaxies. The conspicuous arc is magnified, e.g., by approximately a factor of 20. This effect assists the VLT by acting as a natural, second light collecting facility. The cluster thus provides a deeper look into the universe behind it, and "supports" the identifaction and investigation of distant and young galaxies.
A propos du communiqué de presse
Communiqué de presse N°: | eso9919 |
Legacy ID: | Photo 16a-c/99 |
Nom: | 1ES 0657-558, Spectrum |
Type: | Early Universe : Star : Grouping : Cluster |
Facility: | Very Large Telescope |
Instruments: | FORS1 |
Our use of Cookies
We use cookies that are essential for accessing our websites and using our services. We also use cookies to analyse, measure and improve our websites’ performance, to enable content sharing via social media and to display media content hosted on third-party platforms.
ESO Cookies Policy
The European Organisation for Astronomical Research in the Southern Hemisphere (ESO) is the pre-eminent intergovernmental science and technology organisation in astronomy. It carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities for astronomy.
This Cookies Policy is intended to provide clarity by outlining the cookies used on the ESO public websites, their functions, the options you have for controlling them, and the ways you can contact us for additional details.
What are cookies?
Cookies are small pieces of data stored on your device by websites you visit. They serve various purposes, such as remembering login credentials and preferences and enhance your browsing experience.
Categories of cookies we use
Essential cookies (always active): These cookies are strictly necessary for the proper functioning of our website. Without these cookies, the website cannot operate correctly, and certain services, such as logging in or accessing secure areas, may not be available; because they are essential for the website’s operation, they cannot be disabled.
Functional Cookies: These cookies enhance your browsing experience by enabling additional features and personalization, such as remembering your preferences and settings. While not strictly necessary for the website to function, they improve usability and convenience; these cookies are only placed if you provide your consent.
Analytics cookies: These cookies collect information about how visitors interact with our website, such as which pages are visited most often and how users navigate the site. This data helps us improve website performance, optimize content, and enhance the user experience; these cookies are only placed if you provide your consent. We use the following analytics cookies.
Matomo Cookies:
This website uses Matomo (formerly Piwik), an open source software which enables the statistical analysis of website visits. Matomo uses cookies (text files) which are saved on your computer and which allow us to analyze how you use our website. The website user information generated by the cookies will only be saved on the servers of our IT Department. We use this information to analyze www.eso.org visits and to prepare reports on website activities. These data will not be disclosed to third parties.
On behalf of ESO, Matomo will use this information for the purpose of evaluating your use of the website, compiling reports on website activity and providing other services relating to website activity and internet usage.
Matomo cookies settings:
Additional Third-party cookies on ESO websites: some of our pages display content from external providers, e.g. YouTube.
Such third-party services are outside of ESO control and may, at any time, change their terms of service, use of cookies, etc.
YouTube: Some videos on the ESO website are embedded from ESO’s official YouTube channel. We have enabled YouTube’s privacy-enhanced mode, meaning that no cookies are set unless the user actively clicks on the video to play it. Additionally, in this mode, YouTube does not store any personally identifiable cookie data for embedded video playbacks. For more details, please refer to YouTube’s embedding videos information page.
Cookies can also be classified based on the following elements.
Regarding the domain, there are:
- First-party cookies, set by the website you are currently visiting. They are stored by the same domain that you are browsing and are used to enhance your experience on that site;
- Third-party cookies, set by a domain other than the one you are currently visiting.
As for their duration, cookies can be:
- Browser-session cookies, which are deleted when the user closes the browser;
- Stored cookies, which stay on the user's device for a predetermined period of time.
How to manage cookies
Cookie settings: You can modify your cookie choices for the ESO webpages at any time by clicking on the link Cookie settings at the bottom of any page.
In your browser: If you wish to delete cookies or instruct your browser to delete or block cookies by default, please visit the help pages of your browser:
Please be aware that if you delete or decline cookies, certain functionalities of our website may be not be available and your browsing experience may be affected.
You can set most browsers to prevent any cookies being placed on your device, but you may then have to manually adjust some preferences every time you visit a site/page. And some services and functionalities may not work properly at all (e.g. profile logging-in, shop check out).
Updates to the ESO Cookies Policy
The ESO Cookies Policy may be subject to future updates, which will be made available on this page.
Additional information
For any queries related to cookies, please contact: pdprATesoDOTorg.
As ESO public webpages are managed by our Department of Communication, your questions will be dealt with the support of the said Department.