Arp 220

Arp220 HST NICMOS 1997-17 web print.jpg

The Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) has uncovered a collision between two spiral galaxies in the heart of the peculiar galaxy called Arp 220. The collision has provided the spark for a burst of star formation.

The NICMOS image captures bright knots of stars forming in the heart of Arp 220. The bright, crescent moon-shaped object is a remnant core of one of the colliding galaxies. The core is a cluster of 1 billion stars. The core's half-moon shape suggests that its bottom half is obscured by a disk of dust about 300 light-years across. This disk is embedded in the core and may be swirling around a black hole. The core of the other colliding galaxy is the bright round object to the left of the crescent moon-shaped object. Both cores are about 1,200 light-years apart and are orbiting each other.

Arp 220, located 250 million light-years away in the constellation Serpens, is the 220th object in Halton Arp's Atlas of Peculiar Galaxies.

The image was taken with three filters. The colors have been adjusted so that, in this infrared image, blue corresponds to shorter wavelengths, red to longer wavelengths.

The image was taken April 5, 1997.

Galaxy arp 220.jpg
Galaxy Arp 220 as imaged by the Wide Field Planetary Camera on the Hubble Space Telescope

Arp 220 - JWST, HST.png
Autor/Urheber: Judy Schmidt, Lizenz: CC BY 2.0

A combination of JWST and HST data showing a new view of ultraluminous infrared galaxy Arp 220. Here, I've tried to cut down on the redness because if I were to simply take all the data and throw it together, much of the galaxy would be lost in a red glare. Instead, the central details are actually visible. This is important because the imagery reveals what I presume to be the cores of the two galaxies that merged to create this single disturbed galaxy, not yet fully merged themselves. Prior to JWST observations two cores were already detected, but these new data reveal them in more detail than before.

Surrounding the center are some splotchy red and orange areas representing the MIRI (Mid-Infrared) data. This is essentially glowing dust. That is, the dust emits light in certain mid-infrared wavelengths, revealing it in much greater detail. In visible light, dust requires background illumination to see it or it is otherwise invisible. The eight faint, fuzzy red lines/bars emanating from the center are diffraction spikes caused by support structures of JWST.

Other interesting features include the blue clusters of younger stars resulting from recent star formation brought about when dust and gas collided as the galaxies orbited and merged with one another. Colorful background galaxies were also revealed in JWST data that were previously invisible or below the signal to noise ratio for HST observations. Note that many individual stars and star clusters are visible within the galaxy, thanks to the resolving power of JWST. What may look like noise in this galaxy is actually resolved stars!

Regarding the processing of this image: It took a long time to smooth this out to an aesthetically pleasing image. The shortwave NIRCam imagery is muddled by fine and coarse banding, which makes for a rather unsightly image if not taken care of. I'd like to thank the makers of the open source project G'MIC and specifically Simeon Schmauß for assisting me in greatly reducing and nearly eliminating the banding problems.

Data from the following proposals were used to create this image: Proposal 2739 (no info as of this post) An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in the Local Universe

Reddish orange "screen": JWST MIRI F1130W

Red: JWST NIRCam F444W+F356W+F277W Green: JWST NIRCam F200W+F150W+F090W Blue: HST F814W+F435W

North is up.

Hubble Interacting Galaxy Arp 220 (2008-04-24).jpg

Arp 220 appears to be a single, odd-looking galaxy, but is in fact a nearby example of the aftermath of a collision between two spiral galaxies. It is the brightest of the three galactic mergers closest to Earth, about 250 million light-years away in the constellation of Serpens, the Serpent. The collision, which began about 700 million years ago, has sparked a cracking burst of star formation, resulting in about 200 huge star clusters in a packed, dusty region about 5,000 light-years across (about 5 percent of the Milky Way's diameter). The amount of gas in this tiny region equals the amount of gas in the entire Milky Way Galaxy. The star clusters are the bluish-white bright knots visible in the Hubble image. Arp 220 glows brightest in infrared light and is an ultra-luminous infrared galaxy. Previous Hubble observations, taken in the infrared at a wavelength that looks through the dust, have uncovered the cores of the parent galaxies 1,200 light-years apart. Observations with NASA s Chandra X-ray Observatory have also revealed X-rays coming from both cores, indicating the presence of two supermassive black holes. Arp 220 is the 220th galaxy in Arp's Atlas of Peculiar Galaxies.

This image is part of a large collection of 59 images of merging galaxies taken by the Hubble Space Telescope and released on the occasion of its 18th anniversary on 24th April 2008.

About the object
Object name	Arp 220, IC 1127, VV 540, KPG 470, UGC 09913
Object description	Interacting Galaxies
Position (J2000)	15 34 57.29 +23 30 09.5
Constellation	Serpens
Distance	250 million light-years (100 million parsecs)
About the data
Data description	The Hubble image was created using HST data from proposal 10592: A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)
Instrument	ACS/WFC
Exposure date(s)	January 5, 2002
Exposure time	33 minutes
Filters	F435W (B) and F814W (I)