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Do LIRGs follow the Tully-Fisher relation?
VerСnica Torres MartМnez and Adriana J. ColСn Rosa, Colegio San Felipe Arecibo Mentors: Dr. Tapasi Ghosh, Arecibo Observatory National Astronomy and Ionosphere Center, Arecibo Observatory of Puerto Rico



Abstract

Objectives
The objective of the research is to examine if the Tully-Fisher relation can be applied to LIRGs. For a small we can say majority of investigate i

Conclusion
number of galaxies in our sample, that the T-F relation holds. For the our objects, we have no data to f the TF relation is satisfied or not.

The purpose of this research was to study the LIRGs (Luminous Infrared Galaxies) and see if they follow the Tully-Fisher relation. The LIRGs are different to normal galaxies in the fact that they emit 90% of their light in infrared. The Tullyi Fisher relation states that the bigger the galaxy is, the faster it rotates. The faster the galaxy rotates, the wider is the emission line in velocity. Also, the bigger the galaxy, the more is its luminosity. TullyFisher relation shows that for normal galaxies, the velocity width (W) of the lines is proportional to its luminosity (L) following an equation, L

Methods and Materials
To p e r f o r m t h i s i n v e s t i g a t i o n w e s p o k e with Professor NeftalМ S. Rivera-Castillo of the University of Puerto Rico at Arecibo, and with Dr. T. Ghosh of the Arecibo Observatory, our mentor. They gave us papers, books, web references and some insights about the subject. we reviewed them and developed an understanding of the topic. We then took the following steps. (1) The Radio spectra for neutral hydrogen, and OH radicals were taken using the 305-m Arecibo telescope for a sample of 33 LIRGs during December 2011 (2) We reduced the data which involved calibration and production of averaged spectra using a standard IDL software developed at the Observatory.

Future Work
Due to small number of galaxies, we were unable to check if some of the LIRGs don't follow the TF relation. It is expected that as long as the LIRGs have the rotation and mass distribution of a normal galaxy, they will follow the TF-relation. Due to interaction with closeby galaxies, some of the LIRGs may not follow this law. We need to gather data width) for many more LIR they are interacting with Then study TF plots for interacting LIRGs. (L_abs, and HI-line Gs, and also see if any nearby galaxy. isolated LIRGs and



W.

In a

sample of 33 LIRGs the neutral hydrogen emission line width was measured. The luminosities of these galaxies from literature were found and a study was made of whether the Tully-Fisher law is maintained by the LIRGs. This indicates whether the LIRGs are peculiar either in their motion or in the amount of light they emit.

Introduction

Galaxy: is a large system of stars, star clusters, gas, dust, and nebulae orbiting a common center of mass. IR (Infrared) : The portion of the electromagnetic spectrum with wavelengths longer than red light, ranging from 700 nm to about 1 mm, between (3) Then fitted a baseline visible light and radio waves. and subtracted that out to LIRGs (Luminous Infrared Galaxies): Among the remove any instrumental various type of galaxies there are the Luminous effect. Infrared Galaxies (LIRGs). These are galaxies very bright in IR (Infrared) region of the spectrum. About (4) The HI spectral line is redshifted due to 90% of the light LIRGs emit is IR. LIRGs are not expansion of the universe. So, using Doppler common galactic bodies, they generate effect, the frequency scale of the spectrum was approximately 100 new stars per year. LIRGs are converted into velocity scale. The velocity width of the line is related to the rotational speed of the the result of mix or collisions of galaxies. galaxy. We measured that out of the plots using the HI Line : Neutral hydrogen in galaxies emit a line IDL software. at 21cm wavelength due to spin-flip transition of the electron and proton in a Hydrogen atom. The (5) Next, from the NASA Extragalactic Database line gets broadened due to the internal rotation of (nedwww .ipac.caltech.edu), we gathered the galaxies, and also due to interaction with other the inclination angle and the H-band (1.65 micron) absolute luminosity (L_abs) for each object. closeby galaxies. (6) We then plotted log(L_abs) against log of inclination-corrected velocity width, log[(W_c)] for the LIRGs for which these information were available and the inclination angle was more than 30 deg.

A new step would be to study LIRGs at further distances to investigate if TF relation is followed by LIRGs in early stages of development.

References
1) GUZMAN, R., Class Notes, web site, Ch15.html , http://www.astro.ufl.edu/ ~guzman/ast1002/class_notes/Ch15/ Ch15.html, 05-Jan-2009
2) FREEMAN, K., Structure and Dynamics in the Local Universe, web site, Dark Matter and Tully-Fisher Law, http://www.publish.csiro.au/? act=view_file&file_id=AS04049.pdf, 2004 3) NEHONSKY, F., Distance measurement in space, web site, Tully-Fisher Relation, http:// pluslucis.univie.ac.at/FBA/FBA99/Neho/ 3_1_3_.html, 1998/99 4) Seeds, M. and Backman, D. (2010/11) Galaxies, Astro, ( pp. 194-216),(Instructors Edition), Boston, MA, USA : Laura Rush, Bbooks, Ltd. 5) Robert, M. S. & Haynes .M.P. ,1994 Annu. Rev. Astron. Astrophys., 32: 115 6) Haynes, M.P. & Giovanelli , R. Astron.J. 1984, 89, 758

Results

Tully-Fisher Relation: Astronomers R. Brent Tully and J. Richard Fisher established that if we know the rotation velocity of a galaxy we can determine how bright it is. This correlation is known as TullyFisher (TF) relation. The TF-relation allow us to find the distance by comparing the magnitude and the brightness. Astronomers use the TF-relation to determine when and how LIRGs collision or mix occurs, also to know the stage of evolution, distribution and age of the galaxy. The Tully-Fisher relation allows us to study the galaxies when they were young. Tully-Fisher relation applies to spiral galaxies with a normal rotation and a good mass distribution.
Saturday, May 5, 2012

Acknowledgements
Special thank to: Dra. Tapasi Ghosh Prof. NeftalМ Sotero Rivera Castillo Arecibo Observatory Dr. Juan Arratia Luis Font Aida AlbС NSF Jenipher D. GonzАlez Carlos E. Caro

From this plot, and the "trend curve" we see that L_abs is proportional to W-c for the LIRGs for which we have been able to collect the relevant data. L_abs at H-band is dominited by emission from the stars, and the Hydrogen line width is describing the motion of gas in those galaxies.