e-MERLIN and VLBI observations of the luminous infrared galaxy IC 883: a nuclear starburst and an AGN candidate revealed

Abstract

Context. The high star formation rates of luminous infrared galaxies (LIRGs) make them ideal places for core-collapse supernova (CCSN) searches. Massive star formation can often be found in coexistence with an active galactic nucleus (AGN), contributing jointly to the energy source of LIRGs. At radio frequencies, where light is unaffected by dust extinction, it is possible to detect compact components within the innermost LIRG nuclear regions, such as SNe and SN remnants, as well as AGN buried deep in the LIRG nuclei. Aims. Our study of the LIRG IC 883 aims at: (i) investigating the parsec-scale radio structure of the (circum-)nuclear regions of IC 883; (ii) detecting at radio frequencies the two recently reported circumnuclear SNe 2010cu and 2011hi, which were discovered by near-IR (NIR) adaptive optics observations of IC 883; and (iii) further investigating the nature of SN 2011hi at NIR wavelengths. Methods. We used the electronic European very long baseline interferometry (VLBI) Network (e-EVN) at 5 GHz, and the electronic Multi-Element Remotely Linked Interferometer Network (e-MERLIN) at 6.9 GHz, to observe contemporaneously the LIRG IC 883 at high angular-resolution (from tens to hundreds of milliarcsec) and with high sensitivity (<70 μJy), complemented by archival VLBI data at 5 GHz and 8.4 GHz. We also used the Gemini North telescope to obtain late-time JHK photometry for SN 2011hi. Results. The circumnuclear regions traced by e-MERLIN at 6.9 GHz have an extension of ∼1 kpc, at a position angle of 130 • , and show a striking double-sided structure, which very likely corresponds to a warped rotating ring, in agreement with previous studies. Our e-EVN observations at 5 GHz and complementary archival VLBI data at 5 GHz and 8.4 GHz, reveal various milliarcsec compact components in the nucleus of IC 883. A single compact source, an AGN candidate, dominates the emission at both nuclear and circumnuclear scales, as imaged with the e-EVN and e-MERLIN, respectively. The other milliarcsec components are strongly indicative of ongoing nuclear CCSN activity. Our e-EVN observations also provided upper limits to the radio luminosity of the two SNe in IC 883 recently discovered at NIR wavelengths. We refine the classification of SN 2011hi as a Type IIP SN according to our latest epoch of Gemini North observations acquired in 2012, in agreement with a low-luminosity radio SN nature. We estimate a CCSN rate lower limit of 1.1 +1.3 −0.6 yr −1 for the entire galaxy, based on three nuclear radio SNe and the circumnuclear SNe 2010cu and 2011hi.

Star formation and AGN activity in a sample of local luminous infrared galaxies through multiwavelength characterization

“…This source was classified as an AGN/SB composite (Yuan et al 2010), which has been confirmed by the direct detection of a number of radio componentes that are consistent with an AGN and with SNe/SNRs (Romero-Cañizales et al 2012b) and with the detection, in the near-IR, of two SNe (Kankare et al 2012) within the innermost nuclear region of the galaxy. Through SED model fitting, RomeroCañizales et al (2012b) estimated a core collapse supernova (CCSN) rate of 1.1 SN yr −1 and a SFR of 185 M yr −1 .…”

MOLECULAR GAS HEATING MECHANISMS, AND STAR FORMATION FEEDBACK IN MERGER/STARBURSTS: NGC 6240 AND Arp 193 AS CASE STUDIES

“…Moreover, recent observations indicate that the SF region of Arp 193 is much more compact than indicated by low-J CO imaging (which trace both SF and non-SF molecular gas). Indeed, recent e-MERLIN and very long baseline interferometry imaging revealed recent starburst activity indicated by SNe and SNR taking place within a region with a radius of r ∼ 120 pc (Romero-Cañizales et al 2012). For such compact region, a "coherent" starburst event becomes much easier to induce.…”

SPIRITS 15c and SPIRITS 14buu: Two Obscured Supernovae in the Nearby Star-forming Galaxy IC 2163

“…The SN rate estimates from such searches are still a factor of 3-10 lower than is expected from the high star formation rates inferred from the far-IR luminosities of the surveyed galaxies (e.g., Cresci et al 2007). Radio very long baseline interferometry studies of the innermost regions of LIRGs have, in fact, revealed scores of radio SNe and supernova (SN) remnants that have remained hidden at other wavelengths (Lonsdale et al 2006;Pérez-Torres et al 2009;Ulvestad 2009;Bondi et al 2012;Herrero-Illana et al 2012;Romero-Cañizales et al 2012). A few bona fide radio transients have also been identified as obscured SNeII, e.g., an SN in the starburst Galaxy Mrk297 (Yin & Heeschen 1991), VLA 121550.2+130654 (Gal-Yam et al 2006), and SN2008iz in M82 (A V > 10 mag ;Brunthaler et al 2009Brunthaler et al , 2010Mattila et al 2013).…”