Molecular gas and star formation within 12 strong galactic bars observed with IRAM-30m
Metadatos
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Díaz García, S.; Lisenfeld, Ute; Pérez Martín, María Isabel; Zurita Muñoz, Almudena; Verley, Simon; Espada Fernández, Daniel; Verdes Montenegro, LourdesEditorial
EDP Sciences
Materia
Galaxies: star formation Galaxies: ISM Galaxies: structure Galaxies: evolution Galaxies: statistics
Fecha
2021-10-22Referencia bibliográfica
Díaz-García, S... [et al.]. Molecular gas and star formation within 12 strong galactic bars observed with IRAM-30m. A&A 654, A135 (2021). [https://doi.org/10.1051/0004-6361/202140674]
Patrocinador
European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska Curie 893673; European Commission 721463; State Research Agency (AEI-MCINN) of the Spanish Ministry of Science and Innovation under the grant "The structure and evolution of galaxies and their central regions" - Ministry of Science and Innovation P/300724 PID2019-105602GBI00; Spanish Public Employment Service (SEPE); Spanish Ministerio de Economia y Competitividad, from the European Regional Development Funds (FEDER) AYA2017-84897-P; Junta de Andalucia; European Commission FQM108; Spanish Government BG20/00224; State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa award SEV-2017-0709; Canary Islands Department of Economy, Knowledge and Employment, through the Regional Budget of the Autonomous Community; MINECO/FEDER, UE AYA2015-65973-C3-1-R RTI2018096228-B-C31Resumen
Context. While some galactic bars show recent massive star formation (SF) along them, some others do not. Whether bars with low level of SF are a consequence of low star formation efficiency, low gas inflow rate, or dynamical effects remains a matter of debate. Aims. In order to study the physical conditions that enable or prevent SF, we perform a multi-wavelength analysis of 12 strongly barred galaxies with total stellar masses log(10)(M-*/M-circle dot)is an element of[10.2,11], chosen to host different degrees of SF along the bar major axis without any prior condition on gas content. We observe the CO(1-0) and CO(2-1) emission within bars with the IRAM-30 m telescope (beam sizes of 1.7-3.9 kpc and 0.9-2.0 kpc, respectively; 7-8 pointings per galaxy on average). Methods. We estimated molecular gas masses (M-mol) from the CO(1-0) and CO(2-1) emissions. SF rates (SFRs) were calculated from GALEX near-ultraviolet (UV) and WISE 12 mu m images within the beam-pointings, covering the full bar extent (SFRs were also derived from far-UV and 22 mu m). Results. We detect molecular gas along the bars of all probed galaxies. Molecular gas and SFR surface densities span the ranges log(10)(sigma(mol)/[M-circle dot pc(-2)]) is an element of [0.4,2.4] and log(10)(sigma(SFR)/[M-circle dot pc(-1) kpc(-2)]]) is an element of [-3.25, -0.75], respectively. The star formation efficiency (SFE; i.e., SFR/M-mol) in bars varies between galaxies by up to an order of magnitude (SFE is an element of[0.1,1.8] Gyr(-1)). On average, SFEs are roughly constant along bars. SFEs are not significantly different from the mean value in spiral galaxies reported in the literature (similar to 0.43 Gyr(-1)), regardless of whether we estimate M-mol from CO(1-0) or CO(2-1). Interestingly, the higher the total stellar mass of the host galaxy, the lower the SFE within their bars. In particular, the two galaxies in our sample with the lowest SFE and sigma(SFR) (NGC 4548 and NGC 5850, SFE less than or similar to 0.25 Gyr(-1), sigma(SFR)less than or similar to 10(-2.25)M(circle dot) yr(-1) kpc(-2), M greater than or similar to 10(10.7)M(circle dot)) are also those hosting massive bulges and signs of past interactions with nearby companions. Conclusions. We present a statistical analysis of the SFE in bars for a sample of 12 galaxies. The SFE in strong bars is not systematically inhibited (either in the central, middle, or end parts of the bar). Both environmental and internal quenching are likely responsible for the lowest SFEs reported in this work.
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