APOD: NGC 4449: Star Stream for a Dwarf Galaxy (2012 Jan 26)

[APOD Robot]

NGC 4449: Star Stream for a Dwarf Galaxy

Explanation: A mere 12.5 million light-years from Earth, irregular dwarf galaxy NGC 4449 lies within the confines of Canes Venatici, the constellation of the Hunting Dogs. About the size of our Milky Way's satellite galaxy the Large Magellanic Cloud, NGC 4449 is undergoing an intense episode of star formation, evidenced by its wealth of young blue star clusters, pinkish star forming regions, and obscuring dust clouds in this deep color portrait. It also holds the distinction of being the first dwarf galaxy with an identified tidal star stream, faintly seen at the lower right. Placing your cursor over the image reveals an inset of the stream resolved into red giant stars. The star stream represents the remains of a still smaller infalling satellite galaxy, disrupted by gravitational forces and destined to merge with NGC 4449. With relatively few stars, small galaxies are thought to possess extensive dark matter halos. But since dark matter interacts gravitationally, these observations offer a chance to examine the significant role of dark matter in galactic merger events. The interaction is likely responsible for NGC 4449's burst of star formation and offers a tantalizing insight into how even small galaxies are assembled over time.

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[/b]

[Beyond]

Dwarfs gobbleing Dwarfs. A diminutive episode of galactic canabalism.

[bystander]

Little Galaxies Are Big on Dark Matter
Universe Today | Tammy Plotner | 2011 Dec 29

Dwarf Galaxies and Dark Matter
Cosmotography | R. Jay GaBany

Dwarfs Gobbling Dwarfs: A Stellar Tidal Stream Around NGC 4449 and
Hierarchical Galaxy Formation on Small Scales - David Martinez-Delgado et al

• arXiv.org > astro-ph > arXiv:1112.2154 > 09 Dec 2011

[Ann]

This is a fantastic image!!!

Wish I had more time to comment on it.

R Jay Gabany is a master astrophtographer and extremely good at making RGB portrait of galaxies. He is also a master at teasing out faint details in the outer parts of galaxies and in their surroundings.

Today's portrait is a stunning portrait of starbursting dwarf galaxy NGC 4449. The brilliance of its blue clusters and pink emission nebulae is fantastic.

It is obvious from this picture that NGC 4449 is both similar to, and different from, the Large Magellanic Cloud. It is similar to the LMC because both these galaxies are relatively small, yet extremely full of young bright stars and nebulae. Also, both galaxies are a bit "lopsided": the LMC forms most of its new stars in and around the Tarantula Nebula on one side of the galaxy, and today's APOD makes it clear that more stars are forming on the lower left side of NGC 4449 than on its upper right side.

A remarkable difference between the LMC and NGC 4449 is that the LMC has a central bar with little star formation, but NGC 4449 is forming incredible numbers of stars in its central area.

GRI photography by SDSS has also shown that NGC 4449 has a relatively extensive halo of infrared-bright old stars. I don't know if the LMC has anything similar.

Let's return to today's APOD. To me it is almost shocking to see the color difference, as well as the overall difference, between NGC 4449 and the small dwarf that is about to merge with it. While NGC 4449 is flamboyantly blue and pink, the small dwarf is a dull reddish beige color. NGC 4449 is full of O and B-type stars, brilliantly blue in color, and pink emission nebulae. But the small dwarf galaxy has no really young bright stars at all. All its brightest stars are red giants, which may be billions of years old. No nebulae and no dust is visible in the dwarf galaxy. I have to say that I am glad that R Jay Gabany included a blue galaxy in his inset, otherwise I might almost have doubted that he had used the same filters and the same color balance when he photographed NGC 4449 and when he photographed the small dwarf galaxy.

So all in all, this is a fantastic image, wonderfully esthetically pleasing and scientifically completely fascinating!

Ann

[Byork]

..what field and valley
what glade and stream
grace thy restless arms..

these are the words i repeat to myself when viewing these images of galaxies attended by red wine and certified cheddar cheese. ngc 4449 doesn't appear to have any prominent spiral arms now, but it will in a few years as the faint star cluster merges with the dwarf galaxy. a faint spiral motion is discernable with the galaxy spinning in the clockwise direction. the two well developed spiral galaxies in the distant lower left also deserve attention. do they have an ngc number ? if not, here are my ngc entries for two spiral blue galaxies in the image: ngc 8001 and ngc 8002.

..what field and valley

..

[smitty]

I'm not getting the promised inset when I run my cursor over the image; anybody else experiencing this problem? Thanks.

[smitty]

Never mind . . . got it now (the inset). It was just late arriving. Sorry!

[ohanon]

Anyone know the designations of the two galaxies below the star stream? I'd like to see them enlarged, they're beautiful.

[Case]

Anyone know the designations of the two galaxies below the star stream?

Markarian 1475/PGC 41113 (0.49' × 0.372'), PGC 2233323 (0.447' × 0.219')

I'd like to see them enlarged, they're beautiful.

Good luck with that. The APOD might be it.

[Joe_L]

Great image today! Is there any way I can download it *without* the magnified inset? Thanks!

[geckzilla]

Great image today! Is there any way I can download it *without* the magnified inset? Thanks!

http://www.cosmotography.com/images/gab ... gc4449.jpg
Image copyright ©2009- 2012 R. Jay GaBany

[jgabany]

Great image today! Is there any way I can download it *without* the magnified inset? Thanks!

http://www.cosmotography.com/images/gab ... gc4449.jpg

Hello Joe_L:

Thanks for asking! Here is a link that will enable you to download a large copy of the image without the insert.

http://www.cosmotography.com/images/lrg ... gc4449.jpg

Jay

[saturn2]

N G C 4449 is a irregular galaxy nearly to Earth.
A interesting topic: the dark matter.
This galaxy has a halo of dark matter.
The dark matter interacts gravitacionally and it´s a real force in the Universe.

[Joe_L]

Great image today! Is there any way I can download it *without* the magnified inset? Thanks!

http://www.cosmotography.com/images/gab ... gc4449.jpg

Hello Joe_L:

Thanks for asking! Here is a link that will enable you to download a large copy of the image without the insert.

http://www.cosmotography.com/images/lrg ... gc4449.jpg

Jay

That's great, thank'ye kindly!

[bystander]

Watching a tiny galaxy grow
Max Planck Institute for Astronomy | 2012 Feb 09

Tiny galaxy with a huge appetite
Max Planck Gesellschaft | 2012 Feb 08

Subaru Telescope Captures Images of the "Stealth Merger" of Dwarf Galaxies
National Astronomical Observatory of Japan | Subaru Telescope | 2012 Feb 08

Astronomy team that includes UCLA finance professor discovers nearby dwarf galaxy
University of California, Los Angeles | Stuart Wolpert | 2012 Feb 08

New images capture 'stealth merger' of dwarf galaxies
University of California, Santa Cruz | Tim Stephens | 2012 Feb 08

Perpetrator of Galactic Hit-and-Run Found
Discovery News | Irene Klotz | 2012 Feb 08

A tidally distorted dwarf galaxy near NGC 4449 - R. M. Rich et al

• Nature 482(7384) 192 (09 Feb 2012) DOI: 10.1038/nature10837

http://asterisk.apod.com/viewtopic.php?t=26873#p167980