This project is focused on the analysis of galaxy pairs since they are the minimal unit in which changes of different properties can be measured, such as star formation rate and metallicity. Data are taken from the Galaxy and Mass Assembly Survey II (GAMA-II). The 2dF robot positioner of fibres solved the problem of fiber collision (seen in SDSS), this makes the GAMA survey highly complete and ideal for the study of pairs and groups of galaxies. We selected galaxies at all multiplicities, with a maximum angular separation of 100 arcsec, relative velocity ∆v < 1000 km s −1 , S/N > 3 and a redshift interval 0<z<0.35 from the GAMA galaxy group catalogue. Once galaxy pairs and only SF galaxies were selected, they were divided into 4 categories (from multiplicity 1 to multiplicity ≥4). A control sample for each category was created by matching five control galaxies for each galaxy in a pair: the main condition is that control galaxies must be similar to its galaxy pair in mass and redshift. Our galaxy pairs and control samples had ∼ 4000 and ∼ 17,000 galaxies, respectively. We compared the control and the pair samples in the M-Z and M-SFR relations in order to analyze specifically the posible changes in each property as a function of multiplicity. To control effects of evolution and completeness, we selected three redshift intervals 0<z<0.1, 0.1<z<0.2 and 0.2<z<0.35 to study. The M-SFR and M-Z relations for GAMA II galaxies agree with the well known correlation between both properties. The overview in our results showed that such both properties have an enhancement for galaxy pairs. We found an offset ∆SF R for galaxies with multiplicity 1 that goes from 0.073-0.104 dex in the different intervals of redshift. For multiplicity 2 such offset goes from 0.036-0.116 dex (pairs from these both multiplicities showed the most enhancement of all samples). For the case of metallicities, the ∆Z for pairs with multiplicity 1 is almost constant 0.000-0.008 dex while for pairs multiplicity 2 goes from 0.010-0.017 dex (both in the different intervals of redshift).
By comparing the differences in SFR and Metallicity from all redshifts together, and up to redshift 0.1, it was seen that the differences are mostly the same. In the interval 0.1<z<0.2 the ∆SF R increased for multiplicities 1 and 2, however for multiplicities 3 and ≥4 showed no pattern. In the same interval, ∆Z increased with the multiplicity. In the last range of redshift (0.2<z<0.35) the statistics was only significant for pairs with multiplicity 1 and 2; ∆SF R showed almost the same value than the overview, but is the minimum respect to the other ranges of redshift. For the case of metallicities (in this latter range of redshift), the 0 dex almost keeps for both multiplicities, but there is a slight increment from multiplicity 1 to 2.
The main contributions resided in having a complete analysis of galaxy pairs (free of fibre collision) and deeper in magnitude and redshift. This meaned to analyze the closest pairs and checked if they followed the tendencies found in previous results or they maintained the same behavior even in the closest separations.
Enviado por datalife_enrique@hotmail.com, 2019 Aug