The global gas and dust budget of the Small Magellanic Cloud

Abstract

In order to understand the evolution of the interstellar medium (ISM) of a galaxy, we have analysed the gas and dust budget of the Small Magellanic Cloud (SMC). Using the Spitzer Space Telescope, we measured the integrated gas mass-loss rate across asymptotic giant branch (AGB) stars and red supergiants (RSGs) in the SMC, and obtained a rate of 1.4×10 −3 M ⊙ yr −1 . This is much smaller than the estimated gas ejection rate from type II supernovae (SNe) (2-4×10 −2 M ⊙ yr −1 ). The SMC underwent a an increase in starformation rate in the last 12 Myrs, and consequently the galaxy has a relatively high SN rate at present. Thus, SNe are more important gas sources than AGB stars in the SMC. The total gas input from stellar sources into the ISM is 2-4×10 −2 M ⊙ yr −1 . This is slightly smaller than the ISM gas consumed by starformation (∼8×10 −2 M ⊙ yr −1 ). Starformation in the SMC relies on a gas reservoir in the ISM, but eventually the starformation rate will decline in this galaxy, unless gas infalls into the ISM from an external source. The dust injection rate from AGB and RSG candidates is 1×10 −5 M ⊙ yr −1 . Dust injection from SNe is in the range of 0.2-11×10 −4 M ⊙ yr −1 , although the SN contribution is rather uncertain. Stellar sources could be important for ISM dust (3×10 5 M ⊙ ) in the SMC, if the dust lifetime is about 1.4 Gyrs. We found that the presence of poly-aromatic hydrocarbons (PAHs) in the ISM cannot be explained entirely by carbon-rich AGB stars. Carbon-rich AGB stars could inject only 7×10 −9 M ⊙ yr −1 of PAHs at most, which could contribute up to 100 M ⊙ of PAHs in the lifetime of a PAH. The estimated PAH mass of 1800 M ⊙ in the SMC can not be explained. Additional PAH sources, or ISM reprocessing should be needed.

Mass loss of stars on the asymptotic giant branch

“…This conclusion is in line with the predominance of carbon stars among the extreme objects (Boyer et al 2012;Dell'Agli et al 2016). Nevertheless, Matsuura et al (2013) usedṀ-colour relations and concluded that the dust mass-return rate is equally divided between O-and C-rich objects in both the LMC and SMC (the RSG contribution is negligible). They claimed that a fair fraction of the extreme objects are actually O-rich AGB stars.…”

Dust grains from the heart of supernovae

“…the Magellanic Clouds to make a global census of dusty AGB stars, inferring dust production rates of ∼ 2 × 10 −5 M /yr for the LMC, Riebel et al (2012) and of ∼8 × 10 −7 M /yr for the Small Magellanic Cloud (Boyer et al 2012), with variations among the results of different surveys (Matsuura et al 2013), and in good agreement with theoretical predictions (Ventura et al 2012b. Hence, even in the LMC, the current dust production rate by AGB stars appears to be more than one order of magnitude lower than that estimated from our sample of four SNe.…”

Galaxy And Mass Assembly (GAMA): Gas Fueling of Spiral Galaxies in the Local Universe. I. The Effect of the Group Environment on Star Formation in Spiral Galaxies

“…As mechanisms to replenish the HIreservoirs of galaxies from ionized hydrogen have been put forward (e.g., Hopkins et al 47 In this derivation we at all times assume the rate of change of the inflow to be small compared to the other timescales (quenching and replenishment) involved, and we treatṀ in as (quasi-)constant. 48 Even when considering the total gas return rate from stellar populations, i.e., including the contribution from short-lived stars absorbed in the value of κ, this rate is generally found to be at most several tens of percent of the SFR, both for young lower-mass galaxies, such as the LMC and SMC (Matsuura et al 2009(Matsuura et al , 2013, and for more massive and mature spiral galaxies (Tielens 2005), and thus well shy of the required fueling rates.…”