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M31 UV

As distant light travels on a path toward us, it can be absorbed by intervening, interstellar dust. Much work has been done to understand this “dust extinction” in the Milky Way, providing us with detailed information about the properties of the dust in our galaxy. Far less, however, is known about the dust extinction of other galaxies. The image above, taken with the ultraviolet space telescope GALEX, identifies the locations of four stars in the nearby Andromeda galaxy (click for a full view!) that are reddened due to extinction of their light by dust within Andromeda. In a recent study led by Geoffrey Clayton (Louisiana State University), new, high-signal-to-noise spectra were obtained for these four stars using Hubble’s Space Telescope Imaging Spectrograph. These observations have allowed the authors to construct dust extinction curves to carefully study the nature of Andromeda’s interstellar dust. To learn about the results, see the paper below.

Citation

Geoffrey C. Clayton et al 2015 ApJ 815 14. doi:10.1088/0004-637X/815/1/14

S4G galaxies

These three galaxies (click for a full view!) were imaged as a part of the Spitzer Survey of Stellar Structure in Galaxies (S4G), a recent survey of 2352 nearby galaxies with deep imaging at 3.6 and 4.5 μm. The bottom panels show false-color near-UV and far-UV images previously obtained with GALEX. The top panels show the new images obtained with Spitzer as part of S4G. The three galaxies shown here represent three types of galaxies that have a high concentration of mass in their centers, yet still have a high specific star-formation rate (the star formation rate per unit stellar mass):

  1. Barred galaxies with a prominent ring around their nucleus, like NGC 7552
  2. Interacting systems, like NGC 2782
  3. Galaxies with compact bulges and smooth extended disks, like NGC 3642

To learn why this is the case, and to see more results from S4G, see the original paper below.

Citation

Juan Carlos Muñoz-Mateos et al 2015 ApJS 219 3. doi:10.1088/0067-0049/219/1/3

Westerlund 2 Cluster

This is a color composite image from Hubble of the very young star cluster Westerlund 2, seen near the center of the image (click for the full view!). The image was produced using visible-light data from the Advanced Camera for Surveys and near-infrared data from the Wide Field Camera 3. A recently-published study, led by Peter Zeidler (Center for Astronomy at Heidelberg University), reports the results of a high-resolution multi-band survey of the Westerlund 2 region with Hubble. In their detailed analysis of the cluster, the authors cataloged over 17,000 objects in six different filters! They find that the cluster actually consists of two separate clumps that were born at the same time but have different stellar densities. For more information and the original image, see the paper here:

Citation

Peter Zeidler et al 2015 AJ 150 78. doi:10.1088/0004-6256/150/3/78

The galaxy that takes up most of the frame in this stunning image (click for the full view!) is NGC 1427A. This is a dwarf irregular galaxy (unlike the fortuitously-located background spiral galaxy in the lower right corner of the image), and it’s currently in the process of plunging into the center of the Fornax galaxy cluster. Marcelo Mora (Pontifical Catholic University of Chile) and collaborators have analyzed observations of this galaxy made by both the Very Large Telescope in Chile and the Hubble Advanced Camera for Surveys, which produced the image shown here as a color composite in three channels. The team worked to characterize the clusters of star formation within NGC 1427A — identifiable in the image as bright knots within the galaxy — and determine how the interactions of this galaxy with its cluster environment affect the star formation within it. For more information and the original image, see the paper below.

Citation:

Marcelo D. Mora et al 2015 AJ 150 93. doi:10.1088/0004-6256/150/3/93

Q Continuum simulation

Each frame in this image (click for the full view!) represents a different stage in the simulated evolution of our universe, ending at present day in the rightmost panel. In a recently-published paper, Katrin Heitmann (Argonne National Laboratory) and collaborators reveal the results from — and challenges inherent in — the largest cosmological simulation currently available: the Q Continuum simulation. Evolving a volume of (1300 Mpc)3, this massive N-body simulation tracks over half a trillion particles as they clump together as a result of their mutual gravity, imitating the evolution of our universe over the last 13.8 billion years. Cosmological simulations such as this one are important for understanding observations, testing analysis pipelines, investigating the capabilities of future observing missions, and much more. For more information and the original image (as well as several other awesome images!), see the paper below.

Citation:

Katrin Heitmann et al 2015 ApJS 219 34. doi:10.1088/0067-0049/219/2/34

RCW 103

This is a three-color X-ray image taken by Chandra of the supernova remnant RCW 103. This supernova remnant is an unusual system: it’s young, but unlike other remnants of its age, metal-rich ejecta hadn’t previously been discovered in it. In this paper, Kari Frank (Pennsylvania State University) and collaborators analyze the three deepest Chandra observations of RCW 103 and find the first evidence for metal-rich ejecta emission scattered throughout the remnant. Their analyses also help to constrain the identity of the mysterious compact stellar object powering the remnant. In this image, red = 0.3–0.85 keV, green = 0.85–1.70 keV, and blue = 1.7–3.0 keV; click on the image for the full view. For more information and the original image, see the paper here:

Kari A. Frank et al 2015 ApJ 810 113 doi:10.1088/0004-637X/810/2/113.

coronal loops

This is an extreme ultraviolet image of NOAA Active Region 1283, as seen by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The region in this image consists of two coronal loops embedded within the same coronal magnetic arcade. Rekha Jain and collaborators observed these loops oscillate while a wavefront, plotted on top of the image in white, passed through them. The oscillations were triggered by a nearby solar flare, and studying them can give us information about the properties of the coronal loops that we wouldn’t otherwise be able to measure. For more information and the original image, see the paper below.

Citation:

Rekha Jain et al. 2015 ApJ 804 L19 doi:10.1088/2041-8205/804/1/L19.

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