Hubble’s Hidden Galaxy

IC 342

Credit:  ESA/Hubble & NASA

IC 342 is a challenging cosmic target. Although it is bright, the galaxy sits near the equator of the Milky Way’s galactic disc, where the sky is thick with glowing cosmic gas, bright stars, and dark, obscuring dust. In order for astronomers to see the intricate spiral structure of IC 342, they must gaze through a large amount of material contained within our own galaxy — no mean feat! As a result IC 342 is relatively difficult to spot and image, giving rise to its intriguing nickname: the “Hidden Galaxy”.

Located very close (in astronomical terms!) to the Milky Way, this sweeping spiral galaxy would be among the brightest in the sky were it not for its dust-obscured location. The galaxy is very active, as indicated by the range of colours visible in this NASA/ESA Hubble Space Telescope image, depicting the very central region of the galaxy. A beautiful mixture of hot, blue star-forming regions, redder, cooler regions of gas, and dark lanes of opaque dust can be seen, all swirling together around a bright core. In 2003, astronomers confirmed this core to be a specific type of central region known as an HII nucleus — a name that indicates the presence of ionised hydrogen — that is likely to be creating many hot new stars.

Source: ESA/Hubble/Potw

Understanding Star Formation in the Nucleus of Galaxy IC 342

A BIMA-SONG radio map of the IC 342 central molecular zone; dots indicate locations of SOFIA/GREAT observations.

Credits: Röllig et al.

An international team of researchers used NASA’s Stratospheric Observatory for Infrared Astronomy, SOFIA, to make maps of the ring of molecular clouds that encircles the nucleus of galaxy IC 342. 

The maps determined the proportion of hot gas surrounding young stars as well as cooler gas available for future star formation. The SOFIA maps indicate that most of the gas in the central zone of IC 342, like the gas in a similar region of our Milky Way Galaxy, is heated by already-formed stars, and relatively little is in dormant clouds of raw material.

At a distance of about 13 million light years, galaxy IC 342 is considered relatively nearby. It is about the same size and type as our Milky Way Galaxy, and oriented face-on so we can see its entire disk in an undistorted perspective. Like our galaxy, IC 342 has a ring of dense molecular gas clouds surrounding its nucleus in which star formation is occurring. However, IC 342 is located behind dense interstellar dust clouds in the plane of the Milky Way, making it difficult to study by optical telescopes.

The team of researchers from Germany and the Netherlands, led by Markus Röllig of the University of Cologne, Germany, used the German Receiver for Astronomy at Terahertz frequencies, GREAT, onboard SOFIA to scan the center of IC 342 at far-infrared wavelengths to penetrate the intervening dust clouds. Röllig’s group mapped the strengths of two far-infrared spectral lines – one line, at a wavelength of 158 microns, is emitted by ionized carbon, and the other, at 205 microns, is emitted by ionized nitrogen.

The 158-micron line is produced both by cold interstellar gas that is the raw material for new stars, and also by hot gas illuminated by stars that have already finished forming. The 205-micron spectral line is only emitted by the hot gas around already-formed young stars. Comparison of the strengths of the two  spectral lines allows researchers to determine of the amount of warm gas versus cool gas in the clouds.

Röllig’s team found that most of the ionized gas in IC 342’s central molecular zone (CMZ) is in clouds heated by fully formed stars rather than in cooler gas found farther out in the zone, like the situation in the Milky Way’s CMZ. The team’s research was published in Astronomy and Astrophysics, volume 591.

“SOFIA and its powerful GREAT instrument allowed us to map star formation in the center of IC 342 in unprecedented detail,” said Markus Röllig of the University of Cologne, Germany, “These measurements are not possible from ground-based telescopes or existing space telescopes.”

Researchers previously used SOFIA’s GREAT spectrometer for a corresponding study of the Milky Way’s CMZ. That research, published in 2015 by principal investigator W.D. Langer, et. al, appeared in the journal Astronomy & Astrophysics 576, A1; an overview of that study can be found here. 

SOFIA is a Boeing 747SP jetliner modified to carry a 100-inch diameter telescope. It is a joint project of NASA and the German Aerospace Center, DLR. NASA’s Ames Research Center in California’s Silicon Valley manages the SOFIA program, science and mission operations in cooperation with the Universities Space Research Association headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart. The aircraft is based at NASA’s Armstrong Flight Research Center's Hangar 703, in Palmdale, California.

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For More Information

For more information about SOFIA, visit: http://www.nasa.gov/sofia • http://www.dlr.de/en/sofia

For information about SOFIA's science mission and scientific instruments, visit:  http://www.sofia.usra.edu • http://www.dsi.uni-stuttgart.de/index.en.html

Media Point of Contact

Nicholas A. Veronico
NVeronico@sofia.usra.edu • SOFIA Science Center
NASA Ames Research Center, Moffett Field, California

Editor: Kassandra Bell

Source: NASA/Galaxies

Bursting at the seams

NGC 1569

Credit: ESA/Hubble & NASA, Aloisi, Ford
Acknowledgement: Judy Schmidt (Geckzilla)

This NASA/ESA Hubble Space Telescope image reveals the iridescent interior of one of the most active galaxies in our local neighbourhood — NGC 1569, a small galaxy located about eleven million light-years away in the constellation of Camelopardalis (The Giraffe).

This galaxy is currently a hotbed of vigorous star formation. NGC 1569 is a starburst galaxy, meaning that — as the name suggests — it is bursting at the seams with stars, and is currently producing them at a rate far higher than that observed in most other galaxies. For almost 100 million years, NGC 1569 has pumped out stars over 100 times faster than the Milky Way!

As a result, this glittering galaxy is home to super star clusters, three of which are visible in this image — one of the two bright clusters is actually  the superposition of two massive clusters. Each containing more than a million stars, these brilliant blue clusters reside within a large cavity of gas carved out by multiple supernovae, the energetic remnants of massive stars.

In 2008, Hubble observed the galaxy's cluttered core and sparsely populated outer fringes. By pinpointing individual red giant stars, Hubble’s Advanced Camera for Surveys enabled astronomers to calculate a new — and much more precise — estimate for NGC 1569’s distance. This revealed that the galaxy is actually one and a half times further away than previously thought, and a member of the IC 342 galaxy group.

Astronomers suspect that the IC 342 cosmic congregation is responsible for the star-forming frenzy observed in NGC 1569. Gravitational interactions between this galactic group are believed to be compressing the gas within NGC 1569. As it is compressed, the gas collapses, heats up and forms new stars.

Source: ESA/Hubble - Space Telescope

Twisted magnetic loop in the Giraffe galaxy IC 342

Large-scale polarized emission from IC 342 at 6 cm wavelength, observed with the 100-m Effelsberg telescope at a resolution of 3 minutes of arc. The field size is 0.75°x0.75°, the angular diameter of 0.5° for IC 342 is comparable to that of the full moon in the sky. The lines show the magnetic field orientations. Credit: R. Beck., A&A Vol. 578, A93 (June 2015)

Small- and large-scale polarized emission from IC 342 at 6 cm wavelength, combined from data from the VLA (5 pointings) and the 100-m Effelsberg telescope at a resolution of 25 seconds of arc. The field size is 0.27°x0.27°. Credit: Polarized radio emission: R. Beck/MPIfR; Graphics: U. Klein/AIfA; Background Image: Kitt Peak Observatory (T.A. Rector, University of Alaska Anchorage, and H. Schweiker, WIYN and NOAO/AURA/NSF).

Magnetic-Field Discovery Gives Clues to Galaxy-Formation Processes

Magnetic fields exist everywhere in the Universe, but there is still little idea how important they are for the evolution of cosmic objects. Radio waves are an ideal means to measure magnetic fields in galaxies. In a long-standing effort, Rainer Beck from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, gathered a huge data set of the nearby galaxy IC 342 from observations with two of the world’s largest radio telescopes, NRAO’s Very Large Array and the 100-m radio telescope of the MPIfR, in four different wavelength bands, from 2.8 cm to 21 cm. An ordered magnetic field mostly aligned along the optical spiral arms was discovered. The discovery helps to explain how galactic spiral arms are formed. The same study also shows how gas can be funneled inward toward the center of IC 342.

The results are published in the current online issue of the journal 'Astronomy & Astrophysics'.

Astronomers making a detailed, multi-telescope study of a nearby galaxy have discovered a magnetic field coiled around the galaxy's main spiral arm. "This study helps resolve some major questions about how galaxies form and evolve," says Rainer Beck, of the Max-Planck Institute for Radio Astronomy (MPIfR), in Bonn, Germany.

The scientists studied a galaxy called IC 342, some 10 million light-years from Earth in the northern constellation Camelopardalis (the Giraffe), using MPIfR's 100-meter Effelsberg radio telescope in Germany and the National Science Foundation's Karl G. Jansky Very Large Array (VLA). Data from both radio telescopes were merged to reveal the magnetic structures of the galaxy.

The surprising result showed a huge, helically-twisted loop coiled around the galaxy's main spiral arm. Such a feature, never before seen in a galaxy, is strong enough to affect the flow of gas around the spiral arm.

"Spiral arms can hardly be formed by gravitational forces alone," continues Rainer Beck. "This new IC 342 image indicates that magnetic fields also play an important role in forming spiral arms."

The new observations provided clues to another aspect of the galaxy, a bright central region that may host a black hole and also is prolifically producing new stars. To maintain the high rate of star production requires a steady inflow of gas from the galaxy's outer regions into its center.

"The magnetic field lines at the inner part of the galaxy point toward the galaxy's center, and would support an inward flow of gas," says Rainer Beck.

The scientists mapped the galaxy's magnetic-field structures by measuring the orientation, or polarization, of the radio waves emitted by the galaxy. The orientation of the radio waves is perpendicular to that of the magnetic field. Observations at several wavelengths made it possible to correct for rotation of the waves' polarization plane caused by their passage through interstellar magnetic fields along the line of sight to Earth.

The Effelsberg telescope, with its wide field of view, showed the full extent of IC 342, which, if not partially obscured to visible-light observing by dust clouds within our own Milky Way Galaxy, would appear as large as the full moon in the sky. The high resolution of the VLA, on the other hand, revealed the finer details of the galaxy. The final image was produced by combining five VLA images made with 24 hours of observing time, along with 30 hours of data from Effelsberg.

Scientists from MPIfR, including Rainer Beck were the first to detect polarized radio emission in galaxies, starting with Effelsberg observations of the Andromeda Galaxy in 1978. Another MPIfR scientist, Marita Krause, made the first such detection with the VLA in 1989, with observations that included IC 342, which is the third-closest spiral galaxy to Earth, after the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33).

 Source: Max Planck Institute for Radio Astronomy

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Original Paper 

Magnetic fields in the nearby spiral galaxy IC 342: A multi-frequency radio polarization study 
Rainer Beck Astronomy & Astrophysics, Volume 578, Juni 2015, A93 (DOI: 10.1051/0004-6361/201425572)

 
Local Contact

Dr. Rainer Beck
Phone:+49 228 525-323
Email: rbeck@mpifr-bonn.mpg.de
Max-Planck-Institut für Radioastronomie, Bonn
 
Dr. Norbert Junkes
Presse- und Öffentlichkeitsarbeit
Phone:+49 228 525-399
Email: njunkes@mpifr-bonn.mpg.de
Max-Planck-Institut für Radioastronomie, Bonn


Further Information

Effelsberg Radio Telescope - The Effelsberg 100m radio telescope

JVLA - Karl G. Jansky Very Large Array

Atlas of Galaxies - (Maja Kierdorf & Rainer Beck) 

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The Effelsberg 100m radio telescope is one of the largest fully steerable radio telescopes on earth. It is operated by the Max-Planck-Institut für Radioastronomie in Bonn, Germany and located in a valley approximately 40 km southwest of Bonn. It is a very sensitive instrument in order to investigate magnetic fields in nearby galaxies by observations of polarized radio emission at different radio wavelengths.

The Very Large Array (VLA) is one of the world's premier astronomical radio observatories, consisting of 27 radio antennas of 25 m diameter each in a Y-shaped configuration on the Plains of San Agustin fifty miles west of Socorro, New Mexico. The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Spitzer Sees Spider Web of Stars

IC 342's dust structures show up vividly in red, in this infrared view from Spitzer. Image credit: NASA/JPL-Caltech. Full image and caption

IC 342 has a lower density of stars than what is typical for galaxies, as indicated by a very faint blue haze coming from starlight. Image credit: NASA/JPL-Caltech. Full image and caption

Those aren't insects trapped in a spider's web -- they're stars in our own Milky Way galaxy, lying between us and another spiral galaxy called IC 342. NASA's Spitzer Space Telescope captured this picture in infrared light, revealing the galaxy's bright patterns of dust.

At a distance of about 10 million light-years from Earth, IC 342 is relatively close by galaxy standards. However, our vantage point places it directly behind the disk of our own Milky Way. The intervening dust makes it difficult to see in visible light, but infrared light penetrates this veil easily. While stars in our own galaxy appear as blue/white dots, the blue haze is from IC 342's collective starlight. Red shows the dust structures, which contain clumps of new stars.

The center of the galaxy, where one might look for a spider, is actually home to an enormous burst of star formation. To either side of the center, a small bar of dust and gas is helping to fuel the new stars.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA. For more information about Spitzer, visit http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer

Whitney Clavin (818) 354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

Hiding Out Behind the Milky Way

A leggy cosmic creature comes out of hiding in this new infrared view from NASA's Wide-field Infrared Survey Explorer, or WISE. Image credit: NASA/JPL-Caltech/UCLA. Full image and caption

A leggy cosmic creature comes out of hiding in this new infrared view from NASA's Wide-field Infrared Survey Explorer, or WISE. The spiral beauty, called IC 342 and sometimes the "hidden galaxy," is shrouded behind our own galaxy, the Milky Way. Stargazers and professional astronomers have a hard time seeing the galaxy through the Milky Way's bright band of stars, dust and gas. WISE's infrared vision cuts through this veil, offering a crisp view.

In a spiral galaxy like IC 342, dust and gas are concentrated in the arms. The denser pockets of gas trigger the formation of new stars, as represented here in green and yellow. The core, shown in red, is also bursting with young stars, which are heating up dust. Stars that appear blue reside within our Milky Way, between us and IC 342.

This galaxy has been of great interest to astronomers because it is relatively close. However, determining its distance from Earth has proven difficult due to the intervening Milky Way. Astronomer Edwin Hubble first thought the galaxy might belong to our own Local Group of galaxies, but current estimates now place it farther away, at about 6.6 to 11 million light-years.

This image was made from observations by all four infrared detectors aboard WISE. Blue and cyan represent infrared light at wavelengths of 3.4 and 4.6 microns, which is primarily light from stars. Green and red represent light at 12 and 22 microns, which is primarily emission from warm dust.

Whitney Clavin (818) 354-4673
Whitney.clavin@jpl.nasa.gov