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Messier 104 (NGC 4594)
Michaela Blain

Messier 104

Lying more than 30 million light-years away from us in the constellation Virgo is Messier 104 (M104), more affectionately known as the Sombrero Galaxy. M104 is a beautiful unbarred spiral galaxy with a large, bright central bulge and striking, crisp dust lanes. The Sombrero Galaxy got its name because it resembles the traditional Mexican wide-brimmed hat. Although this galaxy is the 104th object in the famous Messier Catalog, it was actually discovered by a friend of Messier's, Pierre Méchain, in 1781. The Messier catalog is a collection of objects that looked like comets, but were actually discovered not to be comets. The catalog is named for Messier, but was a collaboration between many early astronomers who were searching for comets.

As previously stated, M104 is an unbarred spiral galaxy with a bright central bulge and distinctive dust lanes. Both of these features are visible in the image above. It is approximately 11.3Mpc away, ("Messier 104"). It has an approximate angular size of 6.4 arc minutes which corresponds to a linear size of 69,000 light years. The galaxy gets its off-white, slightly yellowish color from the many stars it contains. The color indicates the majority of M104's stars are relatively hot, white stars and slightly cooler yellow stars. Because of M104's orientation in space, we have a nearly edge-on view of the galaxy's disk. This allows us to see the dark, dust lane that runs across its face. In other spiral galaxies, there are often pink regions within the disk and spiral arms that indicate recent and ongoing star formation. However, the lack of these pinkish regions in M104's disk suggests a lack of new star formation. Because of this, M104 was first classified as an elliptical galaxy, a type of galaxy characterized by a round shape, lack of a disk, and little to no star formation.

The above images (three along the side) were taken by the Chandra X-ray Observatory, Hubble Space Telescope, and Spitzer Space Telescope respectively (http://chandra.harvard.edu/photo/2007/sombrero/).

The large image above is a composite of all three images of M104 taken by three different space telescopes: The Chandra X-ray Observatory, The Hubble Space Telescope, and the Spitzer Space Telescope. Each image was taken in one of three wavelength ranges, then given a false color to enhance the features of the combined image. X-ray is in blue, visible wavelengths are in green, and infrared is in orange.

The X-ray image taken by Chandra hardly looks like a picture of the same object. This is because there are very few X-ray sources within M104. Almost all of the bright dots in this image are active galaxies in the background. There is, however, a "haze" around the central bulge of the galaxy. This could indicate the presence of a super massive black hole (SMBH) at the galaxy's center which is heating up material that orbits around it causing the gas to emit x-rays.

Image taken by Hubble Space Telescope (http://hubblesite.org/image/1415/news_release/2003-28).

The second image, taken by the Hubble Space Telescope, is the most familiar image of this galaxy. Above is the same image in real color. In this high quality image, more of the disk is visible and the central bulge is more distinct from the stellar halo. Also, the dust lane from the image I took reveals itself to be the edge of the galactic disk. From this image we can see the central bulge is quite big and quite bright compared to the disk. The disk itself is thin and seems to be comprised of mostly dust, as there are no bright pink or blue spots that indicate ionized gas. The lack of obvious star-forming regions and of a distinct spiral pattern in the disk seems to suggest M104 is a disk galaxy, not a spiral.

The third image, taken by the Spitzer Space Telescope, shows M104 in infrared. Looking at M104 in this wavelength range reveals a slight halo of infrared radiation centered on the central bulge, as well as more intense infrared emission coming from the disk and galactic center. The presence of distinct infrared emissions in the disk may indicate stages of star formation invisible in other wavelengths.

 

References:

Admin. “Admin.” Messier Objects, 10 Sept. 2015, Accessed 10 Apr. 2017.

"Image - The Majestic Sombrero Galaxy (M104)." HubbleSite. NASA, 2 Oct. 2003. Web. 24 Apr. 2017.

"Messier 104." NASA/IPAC Extragalactic Database. NASA and JPL, n.d. Web. 27 Apr. 2017.

"Sombrero Galaxy: A Great Observatories View." Chandra :: Photo Album :: Sombrero Galaxy :: NASA, 30 Apr. 2007. Web. 24 Apr. 2017.

 

Right Ascension (J2000) 12:39:59.4
Declination (J2000) -11:37:23
Filters used B (Blue), C (Clear), R (Red), V (Green)
Exposure time per filter

B (300s x 10); V (180s x 10); R (120s x 10); C (60s x 5)

Image dimension 1092x736 pixels; 24.0x16.2 arcminutes
Date/time observed March 3, 2017, 09:08 UT

Data Reduction Process:

In MaxIm, the biases and darks were stacked (averaged) to create both a master bias and master dark image. Then, the master bias and master dark images were used to calibrate the raw flats for all the filters. Next, the 10 flats for each filter were stacked (averaged) to create one master flat for each filter. Finally, the raw data was calibrated in each filter using the master bias, master dark, and master flat for the correct filter. These images were stacked (averaged) according to filter to create a master calibrated image in each filter. The final 4 calibrated master images were then color combined to create a final color image. The color combine settings for the R, V, and B filters are as follows: R: 1; V: 1; B: 3.5.

 

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