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Why are some galaxy disks extremely thin? - IISER Tirupati · ... AAAA....VVVV ... IIII....,,,,...
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Galaxies with superthin stellar disks: A Puzzle Our Proposed Solution to the Puzzle Results for a Classic Superthin Galaxy: UGC 7321 Pure disk galaxies (with no bulge component) with R-band images as sharp as razor blades : A puzzle to galaxy formation models ● Vertical-to-planar axes ratio of the stellar disk < 0.1 ● Pure disk galaxies with no bulge component ● Gas Rich, Dark Matter dominated ● Metal poor, Low Star Formation Rate , Low Surface Brightness ● Ubiquitous: Common end product of disk galaxy formation Why are some galaxy disks extremely thin?* Arunima Banerjee 1 & Chanda J. Jog 2 1 National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune – 411007, India 2 Indian Institute of Science, Bangalore – 560012, India * Banerjee, A. & Jog, C. J. 2013, MNRAS, 431, 582 We propose that the presence of a dense and compact dark matter halo is essential for the existence of a superthin stellar disk in a low surface brightness , pure disk (with no bulge component) galaxy. Plot of the ratio z0/RD (where z0 is the calculated stellar exponential verticalscale height and RD the exponential disk scale length) with galactocentric radius R for UGC 7321 for different realizations of the two- component galaxy model of gravitationally-coupled stars and gas in the field of the dark matter halo. This clearly shows that it is the dense, compact dark matter halo and not the gas-rich disk, that is responsible for the superthin stellar disk observed in UGC 7321. Plot of the average value of the ratio z0/RD (where z0 is the stellar vertical scale height and RD the exponential scale length) as a function of the dark matter core radius Rc, here RD = 2.1 kpc as in UGC 7321. From the plot it is clear that the stellar disk becomes superthin only for compact dark matter halos i.e Rc ≤ 2RD Conclusions The presence of a dense and compact dark matter halo is essential for the existence of a superthin stellar disk in a low surface brightness , pure disk (with no bulge component) galaxy. References References References References Goad, J.W., & Roberts, M.S. 1981, Goad, J.W., & Roberts, M.S. 1981, Goad, J.W., & Roberts, M.S. 1981, Goad, J.W., & Roberts, M.S. 1981, ApJ ApJ ApJ ApJ, 250, 79 , 250, 79 , 250, 79 , 250, 79 Matthews, L. D., van Driel, W., & Gallagher, J. S. 1999, AJ, 118, 2751 Matthews, L. D., van Driel, W., & Gallagher, J. S. 1999, AJ, 118, 2751 Matthews, L. D., van Driel, W., & Gallagher, J. S. 1999, AJ, 118, 2751 Matthews, L. D., van Driel, W., & Gallagher, J. S. 1999, AJ, 118, 2751 Zasov, A.V., Bizyaev, D.V., Makarov, D. I., & Tyurina, N.V. 2002, Astronomy Letters, 28, 527 Banerjee, A., Matthews, L. D., & Jog, C. J. 2010, New A, 15, 89
Transcript of Why are some galaxy disks extremely thin? - IISER Tirupati · ... AAAA....VVVV ... IIII....,,,,...
Galaxies with superthin stellar disks: A Puzzle
Our Proposed Solution to the Puzzle
Results for a Classic Superthin Galaxy: UGC 7321
Pure disk galaxies (with no bulge component) with R-band images
as sharp as razor blades : A puzzle to galaxy formation models
● Vertical-to-planar axes ratio of the stellar disk < 0.1
● Pure disk galaxies with no bulge component
● Gas Rich, Dark Matter dominated
● Metal poor, Low Star Formation Rate , Low Surface Brightness
● Ubiquitous: Common end product of disk galaxy formation
Why are some galaxy disks extremely thin?*Arunima Banerjee 1 & Chanda J. Jog 2
1National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune – 411007, India2Indian Institute of Science, Bangalore – 560012, India
* Banerjee, A. & Jog, C. J. 2013, MNRAS, 431, 582
We propose that the presence of a dense and compact dark matter halo is essential for the existence of a superthin stellar disk in a low surface brightness , pure disk (with no bulge component) galaxy.
Plot of the ratio z0/RD (where z0 is the calculated stellar exponentialverticalscale height and RD the exponential disk scale length) withgalactocentric radius R for UGC 7321 for different realizations of the two-component galaxy model of gravitationally-coupled stars and gas in the fieldof the dark matter halo. This clearly shows that it is the dense, compact darkmatter halo and not the gas-rich disk, that is responsible for the superthinstellar disk observed in UGC 7321.
Plot of the average value of the ratio z0/RD (where z0 is the stellar verticalscale height and RD the exponential scale length) as a function of the darkmatter core radius Rc, here RD = 2.1 kpc as in UGC 7321. From the plot itis clear that the stellar disk becomes superthin only for compact darkmatter halos i.e Rc ≤ 2RD
Conclusions
The presence of a dense and compact dark matter halo is essential for the existence of a superthin stellar disk in a low surfacebrightness , pure disk (with no bulge component) galaxy.
ReferencesReferencesReferencesReferencesGoad, J.W., & Roberts, M.S. 1981, Goad, J.W., & Roberts, M.S. 1981, Goad, J.W., & Roberts, M.S. 1981, Goad, J.W., & Roberts, M.S. 1981, ApJApJApJApJ, 250, 79, 250, 79, 250, 79, 250, 79Matthews, L. D., van Driel, W., & Gallagher, J. S. 1999, AJ, 118, 2751Matthews, L. D., van Driel, W., & Gallagher, J. S. 1999, AJ, 118, 2751Matthews, L. D., van Driel, W., & Gallagher, J. S. 1999, AJ, 118, 2751Matthews, L. D., van Driel, W., & Gallagher, J. S. 1999, AJ, 118, 2751ZZZZaaaassssoooovvvv,,,, AAAA....VVVV....,,,, BBBBiiiizzzzyyyyaaaaeeeevvvv,,,, DDDD....VVVV....,,,, MMMMaaaakkkkaaaarrrroooovvvv,,,, DDDD.... IIII....,,,, &&&& TTTTyyyyuuuurrrriiiinnnnaaaa,,,, NNNN....VVVV.... 2222000000002222,,,, AAAAssssttttrrrroooonnnnoooommmmyyyy LLLLeeeetttttttteeeerrrrssss,,,, 22228888,,,, 555522227777BBBBaaaannnneeeerrrrjjjjeeeeeeee,,,, AAAA....,,,, MMMMaaaatttttttthhhheeeewwwwssss,,,, LLLL.... DDDD....,,,, &&&& JJJJoooogggg,,,, CCCC.... JJJJ.... 2222000011110000,,,, NNNNeeeewwww AAAA,,,, 11115555,,,, 88889999
