Probing the circumnuclear stellar populations of starburst galaxies in the near-infrared

Abstract

We employ the NASA Infrared Telescope Facility's near-infrared spectrograph SpeX at 0.8-2.4µm to investigate the spatial distribution of the stellar populations (SPs) in four well known Starburst galaxies: NGC 34, NGC 1614, NGC 3310 and NGC 7714. We use the STARLIGHT code updated with the synthetic simple stellar populations models computed by Maraston (2005, M05). Our main results are that the NIR light in the nuclear surroundings of the galaxies is dominated by young/intermediate age SPs (t 2 × 10 9 yr), summing from ∼40% up to 100% of the light contribution. In the nuclear aperture of two sources (NGC 1614 and NGC 3310) we detected a predominant old SP component (t > 2 × 10 9 yr), while for NGC 34 and NGC 7714 the younger component prevails. Furthermore, we found evidence of a circumnuclear star formation ring-like structure and a secondary nucleus in NGC 1614, in agreement with previous studies. We also suggest that the merger/interaction experienced by three of the galaxies studied, NGC 1614, NGC 3310 and NGC 7714 can explain the lower metallicity values derived for the young SP component of these sources. In this scenario the fresh unprocessed metal poorer gas from the destroyed/interacting companion galaxy is driven to the centre of the galaxies and mixed with the central region gas, before star formation takes place. In order to deepen our analysis, we performed the same procedure of SP synthesis using Maraston & Strömbäck (2011, M11) EPS models. Our results show that the newer and higher resolution M11 models tend to enhance the old/intermediate age SP contribution over the younger ages.

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

“…Near-IR also includes an important contribution from thermally pulsating asymptotic giant branch (TP-AGB) stars, with young to intermediate populations, up to 2 Gyr (Maraston 1998). This range of the spectrum can be used to effectively trace star formation in galaxies where the relatively high extinction hinders their study in the optical (e.g., Dametto et al 2014). This makes near-IR a good spectral window in which to study (super) star clusters (e.g., Díaz-Santos et al 2007;Randriamanakoto et al 2013b).…”

A SINFONI view of the nuclear activity and circumnuclear star formation in NGC 4303 – II. Spatially resolved stellar populations

“…Moreover, this will allow us to compare the results presented here with those previously published by our group using M05 models (e.g. Riffel et al 2010Riffel et al , 2011cStorchi-Bergmann et al 2012;Dametto et al 2014;Schönell et al 2017;Diniz et al 2017). Figure 7.…”

“…In order to deepen our analysis, we decided to perform stellar population synthesis using other EPS models available in the literature: et al (2009, hereafter C09). We do not include the models from Maraston & Strömbäck (2011, hereafter M11) in this analysis, as the use of the lower resolution M05 models is a better option to deal with stellar population synthesis in the NIR when compared to the M11 ones (Dametto et al 2014). Addressing to the limitations on the M11 models, an example is the fact that above ∼1µm about half of the spectra (from Pickles stellar spectral library, used to construct the M11 models that extent to the NIR, Pickles 1998) lack spectroscopic observations leading the authors to construct a smooth energy distribution from broad-band photometry, which may imply that some NIR absorption features are not well resolved, even for these higher resolution models.…”

“…Next, we inspect spaxel-by-spaxel to remove any additional spurious data. For more details see Dametto et al (2014) and starlight manual available at http://www.starlight.ufsc.br.…”

“…Note that the base is not a continuous distribution of ages, with the old ages being represented by 13 Gyr SSPs in this case, for details see(Dametto et al 2014).3 We smoothed all maps to the H-band spatial resolution (0 .6). Note that the K-band has a higher (0 .5) spatial resolution, while the J-band has a lower one (1 ).…”