Atefeh Javadi

The UK Infrared Telescope M33 monitoring project – III. Feedback from dusty stellar winds in the central square kiloparsec

We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group spiral galaxy M33 (Triangulum). The main aim was to identify stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. In this third paper of the series, we measure the dust production and rates of mass loss by the pulsating Asymptotic Giant Branch (AGB) stars and red supergiants. To this aim, we combined our time-averaged nearIR photometry with the multi-epoch mid-IR photometry obtained with the Spitzer Space Telescope. The mass-loss rates are seen to increase with increasing strength of pulsation and with increasing bolometric luminosity. Low-mass stars lose most of their mass through stellar winds, but even super-AGB stars and red supergiants lose � 40% of their mass via a dusty stellar wind. More than three-quarters of the dust return is oxygenous. We construct a 2-D map of the mass-return rate, showing a radial decline but also local enhancements due to agglomerations of massive stars. We estimate a total mass-loss rate of 0.004–0.005 M⊙ yr −1 kpc −2 , increasing to � 0.006 M⊙ yr −1 kpc −2 when accounting for eruptive mass loss (e.g., supernovae); comparing this to the current star formation rate of � 0.03 M⊙ yr −1 kpc −2 we conclude that star formation in the central region of M33 can only be sustained if gas is accreted from further out in the disc or from circum-galactic regions.

The UK Infrared Telescope M33 monitoring project – II. The star formation history in the central square kiloparsec

We have conducted a near-infrared monitoring campaign at the UK Infrared Telescope, of the Local Group spiral galaxy M33 (Triangulum). The main aim was to identify stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. In this second paper of the series, we construct the birth mass function and hence derive the star formation history. The star formation rate has varied between ∼0.002 and 0.007 M⊙ yr ―1 kpc ―2 . We give evidence of two epochs of a star formation rate enhanced by a factor of a few - one that happened ≥6 Gyr ago and produced ≥80 per cent of the total mass in stars, and one around 250 Myr ago that lasted ∼200 Myr and formed ≤6 per cent of the mass in stars. We construct radial and azimuthal distributions in the image plane and in the galaxy plane for populations associated with old first-ascent red giant branch (RGB) stars, intermediate-age asymptotic giant branch (AGB) stars and young (massive) blue and red supergiants. We find that the RGB stars follow an spheroidal distribution, while younger stars follow a flat-disc distribution. The intermediate-age population displays signs of a pseudo-bulge or possibly a bar. The inner spiral arm pattern as recorded in mid-19th-century drawings is confirmed. We interpret our findings as evidence for an old, pressure-supported component and a younger disc formed 6 Gyr ago, with an accretion event occurring 250 Myr ago giving rise to the compact nucleus in M33. Our study provides support for recent Padova stellar evolution models except that super-AGB stars likely reach low temperatures and thus high mass-loss rates, supporting the super-AGB nature of the progenitors of dust-enshrouded supernovae such as SN 2008S.

The UK Infrared Telescope M33 monitoring project – I. Variable red giant stars in the central square kiloparsec

We have conducted a near-infrared monitoring campaign at the UK Infrared Telescope (UKIRT), of the Local Group spiral galaxy M33 (Triangulum). The main aim was to identify stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. The most extensive data set was obtained in the K band with the UIST instrument for the central 4 × 4 arcmin 2 (1 kpc 2 ) - this contains the nuclear star cluster and inner disc. These data, taken during the period 2003-2007, were complemented by J- and H-band images. Photometry was obtained for 18 398 stars in this region; of these, 812 stars were found to be variable, most of which are asymptotic giant branch (AGB) stars. Our data were matched to optical catalogues of variable stars and carbon stars and to mid-infrared photometry from the Spitzer Space Telescope. In this first of a series of papers, we present the methodology of the variability survey and the photometric catalogue - which is made publicly available at the Centre de Donnees astronomiques de Strasbourg - and discuss the properties of the variable stars. The most dusty AGB stars had not been previously identified in optical variability surveys, and our survey is also more complete for these types of stars than the Spitzer survey.

The star formation history of the Magellanic Clouds derived from long-period variable star counts

We present the first reconstruction of the star formation history (SFH) of the Large and Small Magellanic Clouds (LMC and SMC) using Long Period Variable stars. These cool evolved stars reach their peak luminosity in the near-infrared; thus, their K-band magnitudes can be used to derive their birth mass and age, and hence the SFH can be obtained. In the LMC, we found a 10-Gyr old single star formation epoch at a rate of

The ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES). I. Project description, survey sample, and quality assessment

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Probing the Local Bubble with diffuse interstellar bands - I. Project overview and southern hemisphere survey

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Probing the Local Bubble with Diffuse Interstellar Bands. II. The DIB properties in the Northern hemisphere

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The UK Infrared Telescope M33 monitoring project – IV. Variable red giant stars across the galactic disc

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Probing the Local Bubble with Diffuse Interstellar Bands. III. The Northern Hemisphere Data and Catalog

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An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-redshift AGB Analogs

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