Newborn Stars and their Effect on the Universe

Star Cluster

When galaxies form new stars, they sometimes do so in frantic episodes of activity known as starbursts. These events were commonplace in the early Universe, but are rarer in nearby galaxies. Read More →

Future MeerKAT Installation Completes Spectral Analysis of NGC 3109

The KAT-7 radio telescope is probably the largest found in the southern hemisphere. Eventually, it will be expanded to include technology that makes up an even larger system called the MeerKAT. It should remain the largest unit down south until the Square Kilometer Array is finished around 2024. Though one could argue that KAT-7 is still under construction, it is already yielding some pretty amazing results. The device has observed radio emissions from neutral hydrogen gas in the NGC 3109 galaxy.

NGC 3109

NGC 3109 is classified as a Magellanic type irregular galaxy, but it may in fact be a small spiral galaxy. If it is a spiral galaxy, it would be the smallest in the Local Group (dwarf galaxy). NGC 3109 has a mass of about 2.3×109 times the mass of the Sun, of which 20% is in the form of neutral hydrogen. It is oriented edge-on from our point of view, and may contain a disk and a halo. The disk appears to be composed of stars of all ages, whereas the halo contains only very old and metal-poor stars. NGC 3109 does not appear to possess a galactic nucleus.It is about 4.3 million light-years from Earth and is located in the constellation of Hydra. In areas where the gas is moving in a relative direction towards the point of observation, the spectral lines are Doppler shifted upward. In areas where the opposite is true, the spectral lines are downshifted. This means that astronomers can ultimately map the direction in which the gas in the galaxy is moving.

Mapping the universe with neutral hydrogen substances is one of the primary missions for the SKA and MeerKAT installations. The universe is constantly expanding, and this means that distant galaxies are moving away from one another. Spectral analysis should help to calculate just how far away these galaxies are.

NGC 3109

Image Credit: NGC 3109 by GALEX

Reference:

G. Pietrzynski, W. Gieren, A. Udalski, I. Soszynski, F. Bresolin, R. P. Kudritzki, R. Mennickent, & M. Szymanski (2006). The Araucaria Project. A Wide-Field Photometric Survey for Cepheid
Variables in NGC 3109 Astrophys.J.648:366-374,2006 arXiv: astro-ph/0605226v1

Lee, M. (1993). The distance to nearby galaxy NGC 3109 based on the tip of the red giant branch The Astrophysical Journal, 408 DOI: 10.1086/172598

Musella, I., Piotto, G., & Capaccioli, M. (1997). On the cepheid variables of nearby galaxies. III. NGC 3109. The Astronomical Journal, 114 DOI: 10.1086/118528

Barnes, D., & de Blok, W. (2001). On the Neutral Gas Content and Environment of NGC 3109 and the Antlia Dwarf Galaxy The Astronomical Journal, 122 (2), 825-829 DOI: 10.1086/321170

KAT-7. (n.d.). Square Kilometre Array (SKA) Africa. Retrieved March 16, 2012, from http://www.ska.ac.za/media/kat7.php

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A Closer Look at Galaxy Cluster Abell 520

Data from NASA’s Chandra X-ray Observatory show the hot gas in the colliding clusters colored in green. The gas provides evidence that a collision took place. Optical data from NASA’s Hubble Space Telescope and the Canada-France-Hawaii Telescope (CFHT) in Hawaii are shown in red, green, and blue. Starlight from galaxies within the clusters, derived from observations by the CFHT and smoothed to show the location of most of the galaxies, is colored orange.

The blue-colored areas pinpoint the location of most of the mass in the cluster, which is dominated by dark matter. Dark matter is an invisible substance that makes up most of the universe’s mass. The dark-matter map was derived from the Hubble observations, by detecting how light from distant objects is distorted by the cluster galaxies, an effect called gravitational lensing. The blend of blue and green in the center of the image reveals that a clump of dark matter (which can be seen by mousing over the image) resides near most of the hot gas, where very few galaxies are found.

This finding confirms previous observations of a dark-matter core in the cluster announced in 2007. The result could present a challenge to basic theories of dark matter, which predict that galaxies should be anchored to dark matter, even during the shock of a powerful collision.

Source: NASA

Image Credit: NASA, ESA, CFHT, CXO, M.J. Jee (University of California, Davis), and A. Mahdavi (San Francisco State University)

Supermassive Black Holes May be Shaping Galaxies Faster

Image Credit: Artist concept credit: ESA/AOES Medialab)

The understanding of the way in which supermassive black holes shape galaxies is quickly changing, considering that new data is helping astrophysicists to grasp ultra-fast outflows. There is apparently a correlation between central black holes in galaxies and the velocity of stars in the system. An international team at the Goddard Space Flight Center believes that they have identified a particular outflow model that forges a link between black holes and these velocities.

The current understanding is that supermassive black holes make up the center of most decent sized galaxies. Galatic systems that have additional large black holes seem to have bulges where there are faster-moving stars. There seems to be some sort of a feedback loop between star formation and the black hole. However, as of yet, there is no real solid correlation for why this is.

Recent data that was collected by the project, though, explains that ultra-fast outflows might be speeding up these processes. While they’re not as fast as particle jets, ultra-fast outflows are probably making quicker star formation systems. One can hope that the Astro-H X-ray telescope project will help people better understand these concepts when it is presumably launched in 2014. Until that time, the Goddard Center will continue to look into the physical models behind the outflows.

Reference:
Tombesi, F., Cappi, M., Reeves, J., & Braito, V. (2012). Evidence for ultrafast outflows in radio-quiet AGNs – III. Location and energetics Monthly Notices of the Royal Astronomical Society: Letters DOI: 10.1111/j.1745-3933.2012.01221.x

Tombesi, F., Cappi, M., Reeves, J., Palumbo, G., Braito, V., & Dadina, M. (2011). EVIDENCE FOR ULTRA-FAST OUTFLOWS IN RADIO-QUIET ACTIVE GALACTIC NUCLEI. II. DETAILED PHOTOIONIZATION MODELING OF Fe K-SHELL ABSORPTION LINES The Astrophysical Journal, 742 (1) DOI: 10.1088/0004-637X/742/1/44

Tombesi, F., Cappi, M., Reeves, J., Palumbo, G., Yaqoob, T., Braito, V., & Dadina, M. (2010). Evidence for ultra-fast outflows in radio-quiet AGNs Astronomy and Astrophysics, 521 DOI: 10.1051/0004-6361/200913440

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Meet I Zw 18: A Dwarf Galaxy

The Center of Astrophysics of the University of Porto recently came up with an analysis that seriously calls into question the current model of galactic formation. Polychronis Papaderos represented the CAUP, and with his Swedish colleague Göran Östlin, Papderos examined data from the Hubble Space Telescope to better understand the I Zw 18 dwarf galaxy. That particular object has received a lot of attention, and it is one of the few places where star-forming activity can be readily observed.

I Zw 18 region. (Credit: Image courtesy of Centro de Astrofísica da

For a long time, astrophysicists have simply assumed that stars were emitting light from gas structures. These structures occupied the same region as the stars that were emitting the light. The research suggests that galaxies that undergo active starbursts don’t follow this rule. Instead, nebula gases might actually be emitting around half of the total light in question. Since star mass is often calculated from the galaxy’s total luminosity, the idea that nebular emissions account for so much light means that many of these calculations could be totally off. One could also surmise that since I Zw 18 is young, the galaxy is acting the way many objects did shortly after the Big Bang. Many of the stars there have been around for less than 1 billion years. It will be interesting to watch this galaxy in the years ahead.

Reference:

Papaderos, P., & Östlin, G. (2012). I Zw 18 as morphological paradigm for rapidly assembling high-galaxies Astronomy & Astrophysics, 537 DOI: 10.1051/0004-6361/201117551

Izotov, Y., Chaffee, F., Foltz, C., Thuan, T., Green, R., Papaderos, P., Fricke, K., & Guseva, N. (2001). A Spectroscopic Study of Component C and the Extended Emission around I Zw 18 The Astrophysical Journal, 560 (1), 222-235 DOI: 10.1086/322494

Image Credit: Hubble

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