Candidate LBV stars in galaxy NGC 7793 found via HST photometry + MUSE spectroscopy
Aida Wofford, Vanesa Ramirez, Janice C. Lee, David A. Thilker, Lorenza Della Bruna, Angela Adamo, Schuyler D. Van Dyk, Artemio Herrero, Hwihyun Kim, Alessandra … 展开作者
Aida Wofford, Vanesa Ramirez, Janice C. Lee, David A. Thilker, Lorenza Della Bruna, Angela Adamo, Schuyler D. Van Dyk, Artemio Herrero, Hwihyun Kim, Alessandra Aloisi, Daniela Calzetti, Rupali Chandar, Daniel A. Dale, Selma E. de Mink, John S. Gallagher, Dimitrios A. Gouliermis, Kathryn Grasha, Eva K. Grebel, E. Sacchi, Linda J. Smith, Leonardo Ubeda, Rene A. M. Walterbos, Stephen Hannon, Matteo Messa
Only about 19 Galactic and 25 extra-galactic bona-fide Luminous Blue Variables (LBVs) are known to date. This incomplete census prevents our understanding of this crucial phase of massive star evolution which leads to the formation of heavy binary black holes via the classical channel. With large samples of LBVs one could better determine the duration and maximum stellar luminosity which characterize this phase. We search for candidate LBVs (cLBVs) in a new galaxy, NGC 7793. For this purpose, we combine high spatial resolution images from two Hubble Space Telescope (HST) programs with optical spectroscopy from the Multi Unit Spectroscopic Explorer (MUSE). By combining PSF-fitting photometry measured on F547M, F657N, and F814W images, with restrictions on point-like appearance (at HST resolution) and Hα luminosity, we find 100 potential cLBVs, 36 of which fall in the MUSE fields. Five of the latter 36 sources are promising cLBVs which have M(V) less than or equal to -7 and a combination of: Hα with a P-Cygni profile; no [O I] 6300 emission; weak or no [O III] 5007 emission; large [N II]/Hα relative to H II regions; and [S II] 6716 / [S II] 6731 similar to 1. It is not clear if these five cLBVs are isolated from O-type stars, which would favor the binary formation scenario of LBVs. Our study, which approximately covers one fourth of the optical disc of NGC 7793, demonstrates how by combining the above HST surveys with multi-object spectroscopy from 8-m class telescopes, one can efficiently find large samples of cLBVs in nearby galaxies.
We present VLT/MUSE observations of NGC 2070, the dominant ionizing nebula of 30 Doradus in the LMC, plus HST/STIS spectroscopy of its central star cluster R136. Integral Field Spectroscopy (MUSE) and pseudo IFS (STIS) together provides a complete census of all massive stars within the central 30x30 parsec^2 of the Tarantula. We discuss the integrated far-UV spectrum of R136, of particular interest for UV studies of young extragalactic star clusters. Strong HeII 1640 emission at very early ages (1-2 Myr) from very massive stars cannot be reproduced by current population synthesis models, even …
The paper presents new results of the ongoing study of the unusual Lynx-Cancer void galaxy DDO 68 with record-low-metallicity regions (12+log(O/H) ~7.14) of the current star formation (SF). They include: a) a new spectrum and photometry with the 6-m SAO RAS telescope (BTA) for the Luminous Blue Variable (LBV = DDO68-V1). Photometric data sets are complemented with those based on the Sloan Digital Sky Survey (SDSS) and the Hubble Space Telescope (HST) archive images; b) the analysis of the DDO~68 supergiant shell (SGS) and the prominent smaller H-alpha arcs/shells visible at the HST image coupl…
Luminous blue variable stars (LBVs) are of great interest in massive-star evolution as they experience very high mass-loss episodes within short periods of time. HR Car is a famous member of this class in the Galaxy. It has a large circumstellar nebula and has also been confirmed as being in a binary system. One means of gaining information about the evolutionary status and physical nature of LBVs is studying their environments. We investigated the stellar content within ~100 pc of HR Car and also its circumstellar nebula. Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) obs…
Ancient ($>$10 Gyr) globular clusters (GCs) show chemical abundance variations in the form of patterns among certain elements, e.g. N correlates with Na and anti-correlates with O. Recently, N abundance spreads have also been observed in massive star clusters that are significantly younger than old GCs, down to an age of $\sim$2 Gyr. However, so far N has been the only element found to vary in such young objects. We report here the presence of Na abundance variations in the intermediate age massive star clusters NGC 416 ($\sim$6.5 Gyr old) and Lindsay 1 ($\sim$7.5 Gyr old) in the Small Magella…
Nearly all of the well studied ancient globular clusters (GCs), in the Milky Way and in nearby galaxies, show star-to-star variations in specific elements (e.g., He, C, N, O, Na, Al), known as "multiple populations" (MPs). However, MPs are not restricted to ancient clusters, with massive clusters down to $\sim2$ Gyr showing signs of chemical variations. This suggests that young and old clusters share the same formation mechanism but most of the work to date on younger clusters has focused on N-variations. Initial studies even suggested that younger clusters may not host spreads in other elemen…
Core-collapse supernovae (SNe) are the inevitable fate of most massive stars. Since most stars form in groups, SN progenitors can be constrained with information of their environments. It remains challenging to accurately analyse the various components in the environment and to correctly identify their relationships with the SN progenitors. Using a combined dataset of VLT/MUSE spatially-resolved integral-field-unit (IFU) spectroscopy and HST/ACS+WFC3 high-spatial resolution imaging, we present a detailed investigation of the environment of the Type II-P SN 2004dg and Type IIb SN 2012P. The two…
Galactic globular clusters (GCs) are now known to host multiple populations displaying particular abundance variations. The different populations within a GC can be well distinguished following their position in the pseudo two-colors diagrams, also referred to as "chromosome maps". These maps are constructed using optical and near-UV photometry available from the Hubble Space Telescope (HST) UV survey of GCs. However, the chemical tagging of the various populations in the chromosome maps is hampered by the fact that HST photometry and elemental abundances are both available only for a limited …
We present progenitor-star detections, light curves, and optical spectra of SN2009ip and the 2009 optical transient in UGC2773 (U2773-OT), which were not genuine SNe. Precursor variability in the decade before outburst indicates that both of the progenitor stars were LBVs. Their pre-outburst light curves resemble the S Doradus phases that preceded giant eruptions of eta Carinae and SN1954J (V12 in NGC2403), with intermediate progenitor luminosities. HST detections a decade before discovery indicate that the SN2009ip and U2773-OT progenitors were supergiants with likely initial masses of 50-80 …
The luminous blue variable (LBV) RMC143 is located in the outskirts of the 30~Doradus complex, a region rich with interstellar material and hot luminous stars. We report the $3σ$ sub-millimetre detection of its circumstellar nebula with ALMA. The observed morphology in the sub-millimetre is different than previously observed with HST and ATCA in the optical and centimetre wavelength regimes. The spectral energy distribution (SED) of RMC143 suggests that two emission mechanisms contribute to the sub-mm emission: optically thin bremsstrahlung and dust. Both the extinction map and the SED are con…
Aims. We demonstrate the high multiplex advantage of crowded field 3D spectroscopy using the new integral field spectrograph MUSE by means of a spectroscopic analysis of more than 12,000 individual stars in the globular cluster NGC 6397. Methods. The stars are deblended with a PSF fitting technique, using a photometric reference catalogue from HST as prior, including relative positions and brightnesses. This catalogue is also used for a first analysis of the extracted spectra, followed by an automatic in-depth analysis using a full-spectrum fitting method based on a large grid of PHOENIX spect…
Aims. We use the spectra of more than 30,000 red giant branch (RGB) stars in 25 globular clusters (GC), obtained within the MUSE survey of Galactic globular clusters, to calibrate the Ca II triplet (CaT) metallicity relation and derive metallicities for all individual stars. We investigate the overall metallicity distributions as well as those of the different populations within each cluster. Methods. The Ca II triplet in the near-infrared at 8498, 8542, and 8662 AA is visible in stars with spectral types between F and M and can be used to determine their metallicities. In this work, we calibr…
We utilize multi-epoch MUSE spectroscopy to study binaries in the core of NGC 3201. Our sample consists of 3553 stars with 54883 spectra in total comprising 3200 main-sequence stars up to 4 magnitudes below the turn-off. Each star in our sample has between 3 and 63 (with a median of 14) reliable radial velocity (RV) measurements within five years of observations. We introduce a statistical method to determine the probability of a star showing RV variations based on the whole inhomogeneous RV sample. Using HST photometry and an advanced dynamical MOCCA simulation of this specific GC we overcome…
Westerlund 2 (Wd2) is the central ionizing star cluster of the \ion{H}{2} region RCW~49 and the second most massive young star cluster (${\rm M} = (3.6 \pm 0.3)\times 10^4\,{\rm M}_\odot$) in the Milky Way. Its young age ($\sim2\,$Myr) and close proximity to the Sun ($\sim 4\,$kpc) makes it a perfect target to study stars emerging from their parental gas cloud, the large number of OB-stars and their feedback onto the gas, and the gas dynamics. We combine high-resolution multi-band photometry obtained in the optical and near-infrared with the \textit{Hubble} Space Telescope (HST), and VLT/MUSE …
Photometric Metallicities for 367,324 stars of Omega Centauri
Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学前沿天体物理研究所）；School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院）；Department of Physics and Astronomy, University of Notre Dame（圣母大学物理与天文系）；Joint Institute for Nuclear Astrophysics – Center for the Evolution of the Elements (JINA-CEE)（核天体物理联合中心——元素演化中心）
Binary mass transfer via Roche-lobe overflow (RLOF) is a key channel for producing stripped-envelope Wolf-Rayet (WR) stars and may be critical to account for SN Ib/c progenitors. RY Scuti is an extremely rare example of a massive binary star caught in this brief but important phase. Its toroidal nebula indicates equatorial mass loss during RLOF, while the mass-gaining star is apparently embedded in an opaque accretion disk. RY Scuti's toroidal nebula has two components: an inner ionised double-ring system, and an outer dust torus that is twice the size of the ionised rings. We present two epoc…
The bright, nearby, recently discovered supernova SN2010jl is a member of the rare class of relatively luminous Type~IIn events. Here we report archival HST observations of its host galaxy UGC5189A taken roughly 10yr prior to explosion, as well as early-time optical spectra of the SN. The HST images reveal a bright, blue point source at the position of the SN, with an absolute magnitude of -12.0 in the F300W filter. If it is not just a chance alignment, the source at the SN position could be (1) a massive young (less than 6 Myr) star cluster in which the SN resided, (2) a quiescent, luminous b…
A review of the properties of the Tarantula Nebula (30 Doradus) in the Large Magellanic Cloud is presented, primarily from the perspective of its massive star content. The proximity of the Tarantula and its accessibility to X-ray through radio observations permit it to serve as a Rosetta Stone amongst extragalactic supergiant HII regions since one can consider both its integrated characteristics and the individual properties of individual massive stars. Recent surveys of its high mass stellar content, notably the VLT FLAMES Tarantula Survey (VFTS), are reviewed, together with VLT/MUSE observat…
Young star clusters enable us to study the effects of stellar rotation on an ensemble of stars of the same age and across a wide range in stellar mass and are therefore ideal targets for understanding the consequences of rotation on stellar evolution. We combine MUSE spectroscopy with HST photometry to measure the projected rotational velocities (Vsini) of 2,184 stars along the split main sequence and on the main sequence turn-off (MSTO) of the 100 Myr-old massive (10^5 M_sun) star cluster NGC 1850 in the Large Magellanic Cloud. At fixed magnitude, we observe a clear correlation between Vsini …
