Astronomical Observatory: Cool Images

Astr212 Galaxy Projects, Spring 2005

M90 NGC 4569, Joshua Blocker

The name of this spiral galaxy is M90 found by Charles Messier in March of 1781 in the Virgo Cluster. It is
about 60million light years away. This galaxy is moving toward us at 383km/sec so it actually has a blueshift
which is different from other galaxies in the sky which typically have a redshift (moving away from us) due to
the expansion of the universe. This is probably because of the movement in the Virgo Cluster with M90
moving toward us and that velocity is overcoming the expansion of the Universes velocity, so over time it will
end not be moving toward us anymore when it is 180 degrees around the center of the Virgo Cluster.

M90 has an inclination angle of 62 degrees, so we are not looking straight on to it. I was able to calculate this
by finding the effective radius for the major and minor axis of the galaxy then taking the inverse cosine of the
minor axis radius over the major axis radius. M90 has pretty tight spiral arms. There is another galaxy in near
the top of the picture, this is the irregular galaxy IC 3583. It is different than M90 because of the shape of the galaxy. M90 has spirals arms, while IC 3583 does not have a typical galactic shape.

Multiwavelength Comparison

Carbon Monoxide

Carbon Monoxide emission is emitted at 2.6mm, so it is a type of radio wave. It is formed by the cold gas interacting causing an emission line. This image is 2.5 x 2.5 arcmins and showing just the core of the galaxy. Carbon Monoxide photos are the nearest starburst galaxies.

H-alpha

This image is 1.0 x 1.0 arcmins and is oriented 90degrees CCW. This is a picture showing the HII regions in
the galaxy via an H-alpha picture. It is emitting photon of wavelength 6562.8 Angstroms(red). HII regions are clouds of hot, ionized hydrogen in the interstellar medium which is ionized by the formation of stars causing
an H-alpha emission line.

This is the Light Profile for M90 with a linearized fit. A light profile is the brightness that is through the axis of
the galaxy. A profile for both the major axis and the minor axis was created. This also gives a effective radius.
And from the effective radius, you can get the scale length. This has a major axis scale length of 4.4 kpc with
an uncertainty of
+ or - .1kpc.

References:
Banfi, M.; Rampazzo, R.; Chincarini, G.; Henry, R. B. C. H II regions in spiral galaxies: Positions, luminosity
function and diameter distribution 1993, Astronomy and Astrophysics, 280, 373

Sofue, Yoshiaki; Koda, Jin; Nakanishi, Hiroyuki; Onodera, Sachiko; Kohno, Kotaro; Tomita, Akihiko; Okumura, Sachiko K. The Virgo High-Resolution CO Survey: I. CO Atlas 2003, Publications of the
Astronomical Society of Japan, 55, 17

Students for the Exploration and Development of Space, M90

Guided Discoveries M90

This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and
Space Administration.