From Hubble: “Galactic David and Goliath” and “Hubble unveils a galaxy in living colour”

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27 July 2017
Mathias Jäger
ESA/Hubble, Public Information Officer
Garching, Germany
Tel: +49 176 62397500
Email: mjaeger@partner.eso.org

1
The gravitational dance between two galaxies in our local neighbourhood has led to intriguing visual features in both as witnessed in this new NASA/ESA Hubble Space Telescope image. The tiny NGC 1510 and its colossal neighbour NGC 1512 are at the beginning of a lengthy merger, a crucial process in galaxy evolution. Despite its diminutive size, NGC 1510 has had a significant effect on NGC 1512’s structure and amount of star formation.

Galaxies come in a range of shapes and sizes, and astronomers use this fact to classify them based on their appearance. NGC 1512, the large galaxy to the left in this image, is classified as a barred spiral, named after the bar composed of stars, gas and dust slicing through its centre. The tiny NGC 1510 to the right, on the other hand, is a dwarf galaxy. Despite their very different sizes, each galaxy affects the other through gravity, causing slow changes in their appearances.

The bar in NGC 1512 acts as a cosmic funnel, channelling the raw materials required for star formation from the outer ring into the heart of the galaxy. This pipeline of gas and dust in NGC 1512 fuels intense star birth in the bright, blue, shimmering inner disc known as a circumnuclear starburst ring, which spans 2400 light-years.

Both the bar and the starburst ring are thought to be at least in part the result of the cosmic scuffle between the two galaxies — a merger that has been going on for 400 million years.

NGC 1512, which has been observed by Hubble in the past [see below], is also home to a second, more serene, star-forming region in its outer ring. This ring is dotted with dozens of HII regions, where large swathes of hydrogen gas are subject to intense radiation from nearby, newly formed stars. This radiation causes the gas to glow and creates the bright knots of light seen throughout the ring.

Remarkably, NGC 1512 extends even further than we can see in this image — beyond the outer ring — displaying malformed, tendril-like spiral arms enveloping NGC 1510. These huge arms are thought to be warped by strong gravitational interactions with NGC 1510 and the accretion of material from it. But these interactions are not just affecting NGC 1512; they have also taken their toll on the smaller of the pair.

The constant tidal tugging from its neighbour has swirled up the gas and dust in NGC 1510 and kick-started star formation that is even more intense than in NGC 1512. This causes the galaxy to glow with the blue hue that is indicative of hot new stars.

NGC 1510 is not the only galaxy to have experienced the massive gravitational tidal forces of NGC 1512. Observations made in 2015 showed that the outer regions of the spiral arms of NGC 1512 were indeed once part of a separate, older galaxy. This galaxy was ripped apart and absorbed by NGC 1512, just as it is doing now to NGC 1510.

Together, the pair demonstrate how interactions between galaxies, even if they are of very different sizes, can have a significant influence on their structures, changing the dynamics of their constituent gas and dust and even triggering starbursts. Such interactions between galaxies, and galaxy mergers in particular, play a key role in galactic evolution.

Hubble unveils a galaxy in living colour

31 May 2001
Lars Lindberg Christensen
Hubble European Space Agency Information Centre (Garching, Germany)
Phone: +49-(0)89-3200-6306
Cellular (24 hr): +49-(0)173-38-72-621
E-mail: lars@eso.org

Dan Maoz
School of Physics and Astronomy, and Wise Observatory Tel-Aviv University, Israel
Temporary address:
Department of Astronomy, Columbia University, USA Phone: +1-212-854-6899
Email: dani@astro.columbia.edu

Ray Villard
Office of Public Outreach, Space Telescope Science Institute, Baltimore, USA
Phone: +001 410 338 4514
E-mail: villard@stsci.edu

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An extensive, multi-wavelength study with the Hubble Space Telescope has shown the many faces of the galaxy NGC 1512. Hubble’s unique vantage point high above the atmosphere allows scientists to see objects over a broad range of wavelengths from the ultraviolet to the infrared.

In this view of the centre of the magnificent barred spiral galaxy NGC 1512, the NASA/ESA Hubble Space Telescope’s broad spectral vision reveals the galaxy at all wavelengths from ultraviolet through to infrared. The colours (which indicate differences in light intensity) map where newly born star clusters exist in both ‘dusty’ and ‘clean’ regions of the galaxy.

This colour composite image was created from seven images, taken with three different Hubble cameras, the Faint Object Camera (FOC), the Wide Field and Planetary Camera 2 (WFPC2) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).

NASA/Hubble WFPC2. No longer in service.

NASA/Hubble NICMOS

NGC 1512 is a barred spiral galaxy in the southern constellation of Horologium. Located 30 million light years away, relatively ‘nearby’ as galaxies go, it is bright enough to be seen with amateur telescopes. The galaxy spans 70 000 light years, nearly as much as our own Milky Way galaxy.

The galaxy’s core is unique for its stunning 2400 light year wide circle of infant star clusters, called a ‘circumnuclear’ starburst ring. Starbursts are episodes of vigorous formation of new stars and are found in a variety of galaxy environments.

Taking advantage of Hubble’s sharp vision, as well as its unique wavelength coverage, a team of Israeli and American astronomers performed one of the broadest and most detailed studies ever of such star-forming regions. The results, which will be published in the June issue of The Astronomical Journal , show that in NGC 1512 newly born star clusters exist in both dusty and clean environments. The clean clusters are readily seen in ultraviolet and visible light, appearing as bright, blue clumps in the image. However the dusty clusters are revealed only by the glow of the gas clouds in which they are hidden, as detected in red and infrared wavelengths by the Hubble cameras. This glow can be seen as red light permeating the dark, dusty lanes in the ring.

‘The dust obscuration of clusters appears to be an on-off phenomenon’ says Dan Maoz, who headed the collaboration. ‘The clusters are either completely hidden, enshrouded in their birth clouds, or almost completely exposed.’ The scientists believe that stellar winds and powerful radiation from the bright, newly born stars have cleared away the original natal dust cloud in a fast and efficient ‘cleansing’ process.

Aaron Barth, a co-investigator on the team, adds: ‘It is remarkable how similar the properties of this starburst are to those of other nearby starbursts that have been studied in detail with Hubble.’ This similarity gives the astronomers the hope that, by understanding the processes occurring in nearby galaxies, they can better interpret observations of very distant and faint starburst galaxies. Such distant galaxies formed the first generations of stars, when the Universe was a fraction of its current age.

See the full article [http://www.spacetelescope.org/news/heic1712/] here .
See the full article [https://www.spacetelescope.org/news/heic0106/] here .

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The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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