scholarly journals Discovery of a 21 Myr old stellar population in the Orion complex

2019 ◽  
Vol 631 ◽  
pp. A166 ◽  
Author(s):  
Janez Kos ◽  
Joss Bland-Hawthorn ◽  
Martin Asplund ◽  
Sven Buder ◽  
Geraint F. Lewis ◽  
...  

Context. The Orion complex is arguably the most studied star-forming region in the Galaxy. While stars are still being born in the Orion nebula, the oldest part was believed to be no more than 13 Myr old. Aims. In order to study the full hierarchy of star formation across the Orion complex, we perform a clustering analysis of the Ori OB1a region using new stellar surveys and derive robust ages for each identified stellar aggregate. Methods. We use Gaia DR2 parameters supplemented with radial velocities from the GALAH and APOGEE surveys to perform clustering of the Ori OB1a association. Five overdensities are resolved in a six-dimensional parameter space (positions, distance, proper motions, and radial velocity). Most correspond to previously known structures (ASCC 16, 25 Orionis, ASCC 20, ASCC 21). We use Gaia DR2, Pan-STARRS1 and 2MASS photometry to fit isochrones to the colour-magnitude diagrams of the identified clusters. The ages of the clusters can thus be measured with ∼10% precision. Results. While four of the clusters have ages between 11 and 13 Myr, the ASCC 20 cluster stands out at an age of 21 ± 3 Myr. This is significantly greater than the age of any previously known component of the Orion complex. To some degree, all clusters overlap in at least one of the six phase-space dimensions. Conclusions. We argue that the formation history of the Orion complex, and its relation to the Gould belt, must be reconsidered. A significant challenge in reconstructing the history of the Ori OB1a association is to understand the impact of the newly discovered 21 Myr old population on the younger parts of the complex, including their formation.

2014 ◽  
Vol 11 (S308) ◽  
pp. 383-389
Author(s):  
M. A. Aragón-Calvo ◽  
Mark C. Neyrinck ◽  
Joseph Silk

AbstractThe star formation history of galaxies is a complex process usually considered to be stochastic in nature, for which we can only give average descriptions such as the color-density relation. In this work we follow star-forming gas particles in a hydrodynamical N-body simulation back in time in order to study their initial spatial configuration. By keeping record of the time when a gas particle started forming stars we can produce Lagrangian gas-star isochrone surfaces delineating the surfaces of accreting gas that begin producing stars at different times. These surfaces form a complex a network of filaments in Eulerian space from which galaxies accrete cold gas. Lagrangian accretion surfaces are closely packed inside dense regions, intersecting each other, and as a result galaxies inside proto-clusters stop accreting gas early, naturally explaining the color dependence on density. The process described here has a purely gravitational / geometrical origin, arguably operating at a more fundamental level than complex processes such as AGN and supernovae, and providing a conceptual origin for the color-density relation.


2014 ◽  
Vol 10 (S309) ◽  
pp. 169-170
Author(s):  
C. C. Thöne ◽  
L. Christensen ◽  
J. Gorosabel ◽  
A. de Ugarte Postigo

AbstractThe late-type spiral NGC 2770 hosted 3 Type Ib supernovae (SNe) in or next to star-forming regions in its outer spiral arms. We study the properties of the SN sites and the galaxy at different spatial resolutions to infer propeties of the SN progenitors and the SF history of the galaxy. Several 3D techniques are used and, for the first time, we present images of metallicity, shocks and stellar population ages from OSIRIS/GTC imaging with tunable narrowband filters.


1987 ◽  
Vol 117 ◽  
pp. 33-33
Author(s):  
G. Gilmore ◽  
R. Wyse

Analysis of the detailed photometric, kinematic and chemical properties of stellar populations constrains the formation history of the Galaxy. We have completed a photometric survey and initiated a spectroscopic survey, obtaining radial velocities and abundances for volume complete samples of spheroid dwarfs in situ, to distances of a few kpc. Three fields under study are those for which Chiu (Ap. J. Suppl. 1980) obtained proper motions - SA 57 (NGP), SA51 (anticenter field) and SA68. Two of these fields are on the sun - Galactic center meridional plane (SA57 and SA51) so that (U,V) and (V,W) components of space motion respectively may be derived on the basis of the proper motions alone, once distances have been obtained. Our initial distance estimates are from Chiu's photometry and population classes, which are based on the position of the star on the reduced proper motion diagram.


2019 ◽  
Vol 15 (S359) ◽  
pp. 418-420
Author(s):  
João P. V. Benedetti ◽  
Rogério Riffel ◽  
Tiago V. Ricci ◽  
João E. Steiner ◽  
Rogemar A. Riffel ◽  
...  

AbstractWe mapped the stellar population and emission gas properties in the nuclear region of NGC 6868 using datacubes extracted with Gemini Multi-Object Spectrograph (GMOS) in the Integral Field Unit (IFU) mode. To obtain the star-formation history of this galaxy we used the starlight code together with the new generation of MILES simple stellar population models. The stellar population dominating (95% in light fraction) the central region of NGC 6868 is old and metal rich (~10 Gyr, 2.2 Z⊙). We also derived the kinematics and emission line fluxes of ionized gas with the IFSCube package. A rotation disk is clearly detected in the nuclear region of the galaxy and no broad components were detected. Also, there is a region where the emission lines disappear almost completely, probably due to diffuse ionized gas component. Channel maps, diagnostic diagrams and stellar kinematics are still under analysis.


2009 ◽  
Vol 5 (S266) ◽  
pp. 366-366
Author(s):  
Jura Borissova ◽  
Radostin Kurtev ◽  
Margaret M. Hanson ◽  
Leonid Georgiev ◽  
Valentin Ivanov ◽  
...  

AbstractWe are reporting some recent results from our long-term program aimed at characterizing the obscured present-day star cluster population in the Galaxy. Our goal is to expand the current census of the Milky Way's inner stellar disk to guide models seeking to understand the structure and recent star-formation history of our Galaxy. The immediate goal is to derive accurate cluster physical parameters using precise infrared photometry and spectroscopy. So far, we observed approximately 60 star cluster candidates selected from different infrared catalogs. Their nature, reddening, distance, age and mass are analyzed. Two of them, Mercer 3 and Mercer 5, are new obscured Milky Way globular clusters. Among the newly identified open clusters, the objects [DBS2003] 179, Mercer 23, Mercer 30, Mercer 70, and [DBS2003] 106 are particularly interesting because they contain massive young OB and Wolf–Rayet stars with strong emission lines.


2020 ◽  
Vol 498 (3) ◽  
pp. 4205-4221
Author(s):  
N Vale Asari ◽  
V Wild ◽  
A L de Amorim ◽  
A Werle ◽  
Y Zheng ◽  
...  

ABSTRACT The H α and H β emission-line luminosities measured in a single integrated spectrum are affected in non-trivial ways by point-to-point variations in dust attenuation in a galaxy. This work investigates the impact of this variation when estimating global H α luminosities corrected for the presence of dust by a global Balmer decrement. Analytical arguments show that the dust-corrected H α luminosity is always underestimated when using the global H α/H β flux ratio to correct for dust attenuation. We measure this effect on 156 face-on star-forming galaxies from the Mapping Nearby Galaxies at APO (MaNGA) survey. At 1–2 kpc spatial resolution, the effect is small but systematic, with the integrated dust-corrected H α luminosity underestimated by 2–4 per cent (and typically not more than by 10 per cent), and depends on the specific star formation rate of the galaxy. Given the spatial resolution of MaNGA, these are lower limits for the effect. From Multi Unit Spectroscopic Explorer (MUSE) observations of NGC 628 with a resolution of 36 pc, we find the discrepancy between the globally and the point-by-point dust-corrected H α luminosity to be 14 ± 1 per cent, which may still underestimate the true effect. We use toy models and simulations to show that the true difference depends strongly on the spatial variance of the H α/H β flux ratio, and on the slope of the relation between H αluminosity and dust attenuation within a galaxy. Larger samples of higher spatial resolution observations are required to quantify the dependence of this effect as a function of galaxy properties.


2018 ◽  
Vol 14 (S344) ◽  
pp. 118-121
Author(s):  
Rhorom Priyatikanto ◽  
Mochamad Ikbal Arifyanto ◽  
Rendy Darma ◽  
Aprilia ◽  
Muhamad Irfan Hakim

AbstractGlobal history of star or cluster formation in the Large Magellanic Cloud (LMC) has been the center of interest in several studies as it is thought to be influenced by tidal interaction with the Small Magellanic Cloud and even the Milky Way. This study focus on the formation history of the LMC in relation with the context of binary star clusters population, the apparent binary fraction (e.g., percentage of cluster pairs) in different epoch were calculated and analyzed. From the established distributions, it can be deduced that the binary clusters tend to be young (∽ 100 Myr) while their locations coincide with the locations of star forming complexes. There is an indication that the binary fraction increases as the rise of star formation rate in the last millions years. In the LMC, the increase of binary fraction at age ∽ 100 Myr can be associated to the last episode of close encounter with the Small Magellanic Cloud at ∽ 150 Myr ago. This observational evidence supports the theory of binary cluster formation through the fission of molecular cloud where the encounter between galaxies enhanced the clouds velocity dispersion which in turn increased the probability of cloud-cloud collisions that produce binary clusters.


1999 ◽  
Vol 190 ◽  
pp. 470-472
Author(s):  
Eva K. Grebel ◽  
Wolfgang Brandner

A new age calibration of Cepheids and supergiants is used to study the large-scale recent star formation history of the LMC and the SMC. We find evidence for migration of star formation along the LMC bar as well as for the existence of long-lived (≈ 200 Myr) extended star-forming features.


Sign in / Sign up

Export Citation Format

Share Document