Spitzer IRS low-resolution spectra for four candidate Seyfert 1-like objects from ULIRGs in the Sloan Digital Sky Survey, 2dF Galaxy Redshift Survey and 6dF Galaxy Survey

In this paper we present the Spitzer IRS low-resolution observation for four candidates of Seyfert 1-like objects of ULIRGs from the SDSS-2dF-6dF sample. It is found that they are all real Seyfert 1-like objects because their infrared spectra are similar to that for Seyfert 1 source indicative of AGN nature, i.e. their spectra all show high-ionization lines of NeV] at 14.32 μm and/or SIV] at 10.51 μm in the mid-infrared. On the other hand, it is found that they also show PAH features at 6.2, 7.7, 8.6 and 11.25 μm indicative of star formation activity. In addition, it is found that they all show the silicate feature in absorption around 10 μm indicative of heavily material obscured these sources. Furthermore, some correlations among the far infrared colors, the line ratios, the equivalent widths (EWs) of PAH feature and the Silicate strengths are also discussed for these sources.