1. Focus area: Galactic Motion
NGC 891
Focus area: Galactic Motion
Joshua Gross

2. NGC 891 (AKA UGC 1831, PGC 9031, Caldwell 23) RA: 2h 22m 33.4s (J2000)
Dec: +42d 20’ 57” (J2000)
Type: Unbarred spiral galaxy, viewed edge on
Distance: 27.3 Mly
Magnitude: 10.8
Surface Brightness: 14.6 mag/arcmin
Angular Dimensions: 13.5’ x 2.5’
Physical size: 105,000 ly across
Location: Andromeda constellation, part of the NGC 1023 local group and in turn part of Virgo super cluster
Interesting Facts: This galaxy is how we would think the milky way appears when viewed edge on. Was chosen to be the first light image for Large binocular telescope in Because we can see NGC 891 edge on, an observer in that galaxy would not be able to see the milky way in the visible spectrum as the milky way would fall in NGC 891’s zone of avoidance
NASA Extra Galactic Database (NED)
"First Light Information". Large Binocular Telescope Observatory. 2008

4. NGC 891 Edge-on http://apod.nasa.gov/apod/ap131011.html

5. https://commons. wikimedia. org/wiki/File:NGC_891_Hubble_north_part

6. At the Edge of NGC 891, http://apod.nasa.gov/apod/ap120526.html

7. Observing Session:
Date: 03 Mar 16 Sunset: 1815 CST Astronomical Twilight: 2002 CST
Moonset: 1227 CST Moon phase: Waxing crescent
SQM: 1901, 2001, 2101
Cloud Cover: 10% (thin layer at times) Seeing: average-below average
Darkness: 5.6/6.0 Temperature: -10oC Humidity: 60% Pressure: 99.1 kPa
Wind 12 km/h
Issues finding original visual check star Almaak, used the star Mirphak instead
When locating focus star a star field image was used to find the proper star
Nearing end of data collection thin layer of cloud came in, obscuring images
As well when lower in the sky near end of observations effects of light pollution and increased air mass distort images making the blurry

8. Reduced Image
-data reduced using bias, dark, and flat frames
-Used average z project

9. Same as previous image but used median z projection

10. Used blue lookup table
- Able to resolve more of galaxy

11. -Used red LUT
- Reduces some of the noise in image

12. -Sepia LUT
-Image highlights dust band

13. -Thallium LUT
Galaxy and major stars stand out
Good contrast between luminous part of galaxy and dust bad
good contrast between galaxy and background

14. Research and Focus Area
Galaxy Motion
Hubble Flow:
Objects in deep space found to have Doppler shifted light that is shifted to red spectrum (red shift)
This red shift increases proportional to distance and increases the further an object is from earth
Recession Velocity = Ho x D (Ho = Hubble constant ~ 70 km/s/Mpc, D=distance)
Attributed to Edwin Hubble but idea first derived in 1927 by Georges Lemaitre from general relativity.
Hubble confirmed theory two years later and determined hubble constant more accurately
Some Galaxies moving away faster the light because recession velocity caused by universal expansion
Only true for galaxies outside local region, other factors such as motion within local group, cluster, super cluster have effect
Hubble’s law

15. Local Group 50+ galaxies and dwarf galaxies
Milky Way and Andromeda are largest galaxies
Motion dominated by gravity of these galaxies
This structure scale is small enough to be out of the Hubble flow and galaxies are moving together here
The cosmic distance scale, the local group

16. By Andrew Z. Colvin (Own work) [CC BY-SA 3. 0 (http://creativecommons
By Andrew Z. Colvin (Own work) [CC BY-SA 3.0 ( or GFDL ( via Wikimedia Commons

17. Virgo Super cluster 100+ galaxy groupings and clusters 33 mpc across
One of millions of super clusters
Hubble flow is apparent between galaxy groupings but there are other forces at work in galactic motion
NGC 1023 grouping which contains NGC 891 is located in this region
New study shows Virgo to only be a lobe of a much larger Laniakea SC
arXiv: v1 [astro-ph.CO]
10 facts about the milky way, Williams, M. 2014, Universe Today

18. Richard Powell CC BY-SA 2. 5 https://en. wikipedia

19. Laniakea Super Cluster
-100,000+ galaxies
-160 mpc across
-comprised of four major parts that were seen as separate super clusters before(Virgo, Hydra-Centarus, Pavo-Indus, Southern super clusters)
2014 study sets new criteria for designating super clusters
Based on peculiar motion of galaxy clusters(motion predicted by hubble flow plus a small velocity due to flow within cluster envirnment)
Found to be a bulk flow of galaxies towards area near Noma termed the great attractor
R. Brent Tully, Hélène Courtois, Yehuda Hoffman, Daniel Pomarède. The Laniakea supercluster of galaxies. Nature, 2014; 513 (7516): 71 DOI: /nature13674

20. Laniakea Supercluster of Galaxies, arXiv:1409.0880v1 [astro-ph.CO]

21. The Great Attractor
Gravitational anomaly in intergalactic space with a mass ten’s of thousand’s times the milky way
Only viewed in x-ray as it is in our zone of avoidance
Defines our super cluster as it is what dominates the peculiar velocity of galaxy groupings in our super cluster
No clear picture of what it actually is made of or what is causing it
arXiv: v1 [astro-ph.CO]

22. Research Paper
-Discusses how they are proposing the definition of a super cluster to be
Galaxy’s group together in clusters that in turn bunch along filaments that trace out the boundaries of areas absent of galaxies called voids
Explains that the Laniakea super cluster is like a water shed with the peculiar flow of galaxies flowing towards a common point of attraction(the great attractor)
The water shed or area of influence for these attractors determine the boundaries of the super cluster not the location of the galaxy group
arXiv: v1 [astro-ph.CO]

23. arXiv: v1 [astro-ph.CO]

24. Conclusion
Multiple factors at different levels affect galactic motion beyond Hubble flow
NGC 891 is not in our local group but is in our super cluster
Hubble flow still dominates over all galactic motion
Our galactic neighbourhood has recently gotten a whole lot bigger

25. Questions?

26. Refrences
Laniakea Supercluster of Galaxies, arXiv: v1 [astro-ph.CO]
NASA Extra Galactic Database (NED)
"First Light Information". Large Binocular Telescope Observatory. 2008
NGC 891 Edge-on
At the Edge of NGC 891,
Hubble’s law
The cosmic distance scale, the local group
By Andrew Z. Colvin (Own work) [CC BY-SA 3.0 ( or GFDL ( via Wikimedia Commons
arXiv: v1 [astro-ph.CO]
10 facts about the milky way, Williams, M. 2014, Universe Today
Richard Powell CC BY-SA 2.5
R. Brent Tully, Hélène Courtois, Yehuda Hoffman, Daniel Pomarède. The Laniakea supercluster of galaxies. Nature, 2014; 513 (7516): 71 DOI: /nature13674