By: Carlos E. Marín Pérez & Edwin C. López Ramos Mentor: Dr. Tapasi Ghosh Arecibo Observatory Gas in Luminous Infrared Galaxies

Luminous Infrared Galaxies, also known as LIRGs, are galaxies that emit 90% of their light in infrared. These galaxies create one hundred times more stars in comparison with normal galaxies. The objective of this project is to investigate if the gas in these LIRGs is in a “strange” state. The data has been obtained via radio spectroscopic observations of neutral Hydrogen (HI) and OH radicals present in the interstellar space of these galaxies.

 Known as Hydrogen, HI is the simplest and most abundant atom in space.  HI is of scientific key-importance for our understanding of galaxy formation, evolution and merging history.

 Radio frequency interference, RFI, is any undesirable electrical energy with content within the frequency range dedicated to radio frequency transmission.  RFI by conduction is most often found in the low frequency range of several kHz to 30MHz.  Radiated RFI is most often found in the frequency range from 30MHz to 10GHz.

 Problem Gas in luminous infrared galaxies.  Question Is the gas in luminous infrared galaxies(LIRGs) in a “strange” state?  Hypothesis The gas in the luminous infrared galaxies (LIRGs) will be in a “strange” state.  Hypothesis justification Xímena, María (Spring, 2007). “HI 21cm and OH 18cm Arecibo Observations of Galaxies with High Infrared Luminosity from the 2 Jy IRAS- NVSS Sample”. Vassar College.

1. Turn on and log in the computer. 2. Launch the X11 application in order to begin with the data reduction. 3. Measure the HI line. 4. Verify if the HI emissions are Symmetric or asymmetric.

5. Verify if there is any HI absorption. 6. Check if there’s OH absorption. 7. Repeat steps 2 through 6 for each and one of the sources. 8. Place the experimental data in tables.

9.Calculate the ratio of the symmetry, asymmetry, HI absorption and OH absorption. 10.Make graphs comparing the data obtained with the control group of the investigation.

The board on the left is an example of an HI emission in the spectrum. Source

The board on the left is an example of a polarization- averaged HI emission in the spectrum. Source

The board on the left is an example of a polarization- averaged HI emission that has been zoomed on to the spectrum. Source

 Symmetry is when one shape becomes exactly like another when flipped over.  Asymmetry is when one shape doesn’t become exactly like another when flipped over.  The presence of asymmetry in the LIRGs indicate effects of interactions with other near by galaxies.

On the left there is a example of a symmetrical HI emission.

On the left there is a example of a asymmetrical HI emission.

The symmetry and asymmetry ratio of both LIRGs and normal galaxies Ratio of asymmetry and symmetry Symmetry and asymmetry of each group

The figure on the left is an example of HI absorption. HI absorption indicates if there is presence of any cold gas in the LIRGs.

The HI absorption ratio in Luminous Infrared Galaxies(LIRGs) in comparison with the absence of HI absorption in the same LIRGs. Absortion Ratio

 The presence of OH absorption indicates if there is any dust in the interstellar space of the LIRGs.  There wasn’t any detectable presence of OH absorption due to the RFI in the observations.

In sum, the data that was collected during the investigation supports the hypothesis that states that the gas will be in a “strange” state in these LIRGs. Though there wasn’t any presence of OH absorption and a minimum ratio of HI absorption, there was a high level of asymmetry in the HI emissions. This indicates that these galaxies are interacting with other galaxies, thus altering the gas’s state in the observed LIRGs. For a future investigation, it is recommended that there should be a comparative study between different LIRG groups on a larger scale.

 Dr. Tapasi Ghosh- Mentor  Dr. Juan F. Arratia- Director & Principal Investigator  Luis Font-Coordinator  Gladys Sanchéz-School Teacher  Dr. Edvier Cabassa- Technical Support.  Chris Salter- Organizer  Jennifer Danline- Poster Orientation  Carmen Pérez & Yolanda Ramos- Mothers  Carlos Caro- Motivator

 Xímena, María (Spring, 2007). “HI 21cm and OH 18cm Arecibo Observations of Galaxies with High Infrared Luminosity from the 2 Jy IRAS-NVSS Sample”. Vassar College.