The nuclear starburst in Arp 299-A: from the 5.0 GHz VLBI radio light-curves to its core-collapse supernova rate

Abstract

Context. The nuclear region of the luminous infrared galaxy (LIRG) Arp 299-A hosts a recent ( 10 Myr) intense burst of massive star formation that is expected to lead to numerous core-collapse supernovae (CCSNe). Previous VLBI observations, carried out with the European VLBI Network (EVN) at 5.0 GHz and with the VLBA at 2.3 and 8.4 GHz, resulted in the detection of many compact, bright, non-thermal sources in a region < ∼ 150 pc in size. Aims. We aim to establish the nature of all non-thermal compact components in Arp 299-A, as well as to estimate its core-collapse supernova rate. While the majority of the compact components are expected to be young radio supernovae (RSNe) and supernova remnants (SNRs), a definitive classification is still lacking. Yet, this is very relevant for eventually establishing the CCSN rate, as well as the star formation rate, for this galaxy. Methods. We used multi-epoch EVN observations taken at 5.0 GHz to image the compact radio sources in the nuclear region of Arp 299-A with milliarcsecond resolution. We also used one single-epoch 5.0 GHz Multi-Element Radio Linked Interferometer Network (MERLIN) observation to image the extended emission in which these compact radio sources are embedded.Results. We present the first 5.0 GHz radio light-curve (spanning ∼2.5 yr) of all compact components in the nuclear starburst of Arp 299-A. Twenty-six compact sources are detected, eight of which are new objects. The properties of all detected objects are consistent with them being a mixed population of CCSNe and SNRs. We find clear evidence for at least two new CCSNe, implying a lower limit to the CCSN rate of ν SN > ∼ 0.80 SN/yr, indicating that the bulk of the current star formation in Arp 299-A is taking place in the innermost ∼150 pc. A few more objects show variability consistent with them being recently exploded SNe, but only future observations will clarify this point. Our MERLIN observations trace a region of diffuse extended emission that is cospatial to the region where all compact sources are found. From this diffuse non-thermal radio emission traced by MERLIN we obtain an independent estimate for the CCSN rate, which is in the range ν SN = 0.40−0.65 SN/yr, in agreement with previous estimates and our direct estimate of the CCSN rate from the compact radio emission. Conclusions. Our ∼2.5 yr monitoring of Arp 299-A has allowed us to obtain for the first time a direct estimate of the CCSN rate of ν SN > ∼ 0.80 SN/yr for the innermost ∼150 pc of Arp 299-A.

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).…”

No AGN evidence in NGC 1614 from deep radio VLBI observations

“…An interesting case is Arp 299, as its IR luminosity (6.7 × 10 11 L ) and distance (45 Mpc) make it comparable to NGC 1614. From the dozens of compact sources detected in Arp 299 (Pérez-Torres et al 2009;Bondi et al 2012), only eight are above our 5σ detection threshold (7.4 × 10 26 erg s −1 Hz −1 ) and have a SN origin. Furthermore, the supernova rate obtained through consistent SED multiwavelength modeling is higher for Arp 299 ( 0.8 SN yr −1 ; Mattila et al 2012) than for NGC 1614 ( 0.4 SN yr −1 ; Herrero-Illana et al 2014).…”

Arp 299: The show must go on!

“…Miguel Pérez-Torres There is also growing evidence that A6 is a microquasar, based on its appearance and disappearance in our 5.0 GHz images [12,2]. If confirmed, A6 would be, together with the microquasar candidates in Arp 220 [1], one of the first extragalactic microquasars to be confirmed ever.…”

“…More recently, we presented the first 5.0 GHz radio light-curve (spanning ∼2.5 yr) of 26 compact components in the nuclear starburst of Arp 299-A ( [2] and Fig. 1).…”

“…Those SNe can be detected, even in the innermost regions of U/LIRGs, by means of high angular resolution (≤ 0.05 arcsec), high-sensitivity (≤0.05 mJy) radio searches, which proved that they can unveil nuclear starbursts and detect individual radio supernovae up to large distances in the local Universe (e.g. Arp 220 [9]; Arp 299 [10,2]; IC 883 [14]). …”