A DECam view of the diffuse dwarf galaxy Crater II: the colour–magnitude diagram

ABSTRACT We present a deep Blanco/DECam colour–magnitude diagram (CMD) for the large but very diffuse Milky Way satellite dwarf galaxy Crater II. The CMD shows only old stars with a clearly bifurcated subgiant branch (SGB) that feeds a narrow red giant branch. The horizontal branch (HB) shows many RR Lyrae and red HB stars. Comparing the CMD with [Fe/H] = −2.0 and [α/Fe] = + 0.3 alpha-enhanced BaSTI isochrones indicates a mean age of 12.5 Gyr for the main event and a mean age of 10.5 Gyr for the brighter SGB. With such multiple star formation events Crater II shows similarity to more massive dwarfs that have intermediate age populations, however for Crater II there was early quenching of the star formation and no intermediate age or younger stars are present. The spatial distribution of Crater II stars overall is elliptical in the plane of the sky, the detailed distribution shows a lack of strong central concentration, and some inhomogeneities. The 10.5 Gyr subgiant and upper main-sequence stars show a slightly higher central concentration when compared to the 12.5 Gyr population. Matching to Gaia DR2 we find the proper motion of Crater II: μαcos δ = −0.14 ± 0.07, μδ = −0.10 ± 0.04 mas yr−1, approximately perpendicular to the semimajor axis of Crater II. Our results provide constraints on the star formation and chemical enrichment history of Crater II, but cannot definitively determine whether or not substantial mass has been lost over its lifetime.

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The Sagittarius Dwarf Galaxy Survey (SDGS): Constraints on the Star Formation History of the Sgr dSph

Symposium - International Astronomical Union ◽

10.1017/s0074180900204026 ◽

1999 ◽

Vol 192 ◽

pp. 121-128

Author(s):

M. Bellazzini ◽

F. R. Ferraro ◽

R. Buonanno

Keyword(s):

Star Formation ◽

Star Formation Rate ◽

Dwarf Galaxy ◽

Formation Rate ◽

Star Formation History ◽

Full Potential ◽

Chemical Enrichment ◽

Formation History ◽

The Galaxy ◽

History Of

The main characteristics of a wide photometric survey of the Sgr dwarf spheroidal galaxy are briefly presented. V and I photometry has been obtained for ~90000 stars toward Sgr and for ~9000 stars in a region devoid of Sgr stars (for decontamination purposes).The full potential of this large database is far from being completely explored. Here we present only preliminary results from the analysis of statistically decontaminated Color Magnitude Diagrams, trying to set a scheme of the Star Formation History of the Sgr Galaxy. A scenario is proposed in which star formation in Sgr began very early and lasted for several Gyr, with progressive chemical enrichment of the Inter-Stellar Medium (ISM). Nearly 8 Gyr ago the star formation rate abruptly decreased, perhaps in coincidence with the event that led to the gas depletion of the galaxy. A very small rate of star formation continued until relatively recent times (~ 1 Gyr ago).

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The Star Formation History of the Local Group Dwarf Galaxy Leo I

The Astronomical Journal ◽

10.1086/301078 ◽

1999 ◽

Vol 118 (5) ◽

pp. 2245-2261 ◽

Cited By ~ 115

Author(s):

Carme Gallart ◽

Wendy L. Freedman ◽

Antonio Aparicio ◽

Giampaolo Bertelli ◽

Cesare Chiosi

Keyword(s):

Star Formation ◽

Local Group ◽

Dwarf Galaxy ◽

Star Formation History ◽

Formation History ◽

History Of

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Gaia DR1 completeness within 250 pc & star formation history of the Solar neighbourhood

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317006159 ◽

2017 ◽

Vol 12 (S330) ◽

pp. 148-151 ◽

Cited By ~ 1

Author(s):

Edouard J. Bernard

Keyword(s):

Star Formation ◽

Star Formation History ◽

Solar Neighbourhood ◽

The Sun ◽

Thick Disc ◽

Formation History ◽

Magnitude Diagram ◽

History Of

AbstractWe took advantage of the Gaia DR1 to combine TGAS parallaxes with Tycho-2 and APASS photometry to calculate the star formation history (SFH) of the solar neighbourhood within 250 pc using the colour-magnitude diagram fitting technique. We present the determination of the completeness within this volume, and compare the resulting SFH with that calculated from the Hipparcos catalogue within 80 pc of the Sun. We also show how this technique will be applied out to ~5 kpc thanks to the next Gaia data releases, which will allow us to quantify the SFH of the thin disc, thick disc and halo in situ, rather than extrapolating based on the stars from these components that are today in the solar neighbourhood.

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Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

Proceedings of the International Astronomical Union ◽

10.1017/s174392131600764x ◽

2015 ◽

Vol 11 (S315) ◽

Author(s):

Monique C. Aller ◽

Varsha P. Kulkarni ◽

Donald G. York ◽

Daniel E. Welty ◽

Giovanni Vladilo ◽

...

Keyword(s):

Star Formation ◽

Galaxy Evolution ◽

Absorption Feature ◽

Dust Grains ◽

Interstellar Gas ◽

Chemical Enrichment ◽

Normal Galaxies ◽

History Of ◽

Dust Grain ◽

Grain Properties

AbstractGas and dust grains are fundamental components of the interstellar medium and significantly impact many of the physical processes driving galaxy evolution, such as star-formation, and the heating, cooling, and ionization of the interstellar material. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous quasars, provide a valuable tool to directly study the properties of the interstellar gas and dust in distant, normal galaxies. We have established the presence of silicate dust grains in at least some gas-rich QASs, and find that they exist at higher optical depths than expected for diffuse gas in the Milky Way. Differences in the absorption feature shapes additionally suggest variations in the silicate dust grain properties, such as in the level of grain crystallinity, from system-to-system. We present results from a study of the gas and dust properties of QASs with adequate archival IR data to probe the silicate dust grain properties. We discuss our measurements of the strengths of the 10 and 18 μm silicate dust absorption features in the QASs, and constraints on the grain properties (e.g., composition, shape, crystallinity) based on fitted silicate profile templates. We investigate correlations between silicate dust abundance, reddening, and gas metallicity, which will yield valuable insights into the history of star formation and chemical enrichment in galaxies.

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The star formation history of galaxies in 3D: CALIFA perspective

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314009399 ◽

2014 ◽

Vol 10 (S309) ◽

pp. 99-104

Author(s):

R. M. González Delgado ◽

R. Cid Fernandes ◽

R. García-Benito ◽

E. Pérez ◽

A. L. de Amorim ◽

...

Keyword(s):

Star Formation ◽

Surface Density ◽

Spectral Synthesis ◽

Stellar Mass ◽

Star Formation History ◽

Chemical Enrichment ◽

Radial Profiles ◽

Formation History ◽

The Galaxy ◽

History Of

AbstractWe resolve spatially the star formation history of 300 nearby galaxies from the CALIFA integral field survey to investigate: a) the radial structure and gradients of the present stellar populations properties as a function of the Hubble type; and b) the role that plays the galaxy stellar mass and stellar mass surface density in governing the star formation history and metallicity enrichment of spheroids and the disks of galaxies. We apply the fossil record method based on spectral synthesis techniques to recover spatially and temporally resolved maps of stellar population properties of spheroids and spirals with galaxy mass from 109 to 7×1011 M⊙. The individual radial profiles of the stellar mass surface density (μ⋆), stellar extinction (AV), luminosity weighted ages (〈logage〉L), and mass weighted metallicity (〈log Z/Z⊙〉M) are stacked in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc and Sd). All these properties show negative gradients as a sight of the inside-out growth of massive galaxies. However, the gradients depend on the Hubble type in different ways. For the same galaxy mass, E and S0 galaxies show the largest inner gradients in μ⋆; and Andromeda-like galaxies (Sb with log M⋆ (M⊙) ∼ 11) show the largest inner age and metallicity gradients. In average, spiral galaxies have a stellar metallicity gradient ∼ −0.1 dex per half-light radius, in agreement with the value estimated for the ionized gas oxygen abundance gradient by CALIFA. A global (M⋆-driven) and local (μ⋆-driven) stellar metallicity relation are derived. We find that in disks, the stellar mass surface density regulates the stellar metallicity; in spheroids, the galaxy stellar mass dominates the physics of star formation and chemical enrichment.

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The Star Formation History of Leo I

Symposium - International Astronomical Union ◽

10.1017/s0074180900204063 ◽

1999 ◽

Vol 192 ◽

pp. 151-157

Author(s):

C. Gallart ◽

W. L. Freedman

Keyword(s):

Star Formation ◽

Binary Stars ◽

Large Fraction ◽

Solar Neighborhood ◽

Star Formation History ◽

Formation History ◽

Magnitude Diagram ◽

History Of ◽

The One ◽

Low Rate

We advance some results of our study of the star formation history of the Local Group dSph galaxy Leo I, obtained through the analysis of its deep HST color-magnitude diagram (CMD) using model CMDs computed from stellar evolutionary models. We conclude that most star formation (≃ 90%) took place in Leo I between 7 and 1 Gyr ago. It seems to have started at a very low rate ≃ 15 Gyr ago and continued, also at a very low rate, from 1 Gyr ago until the present time. A constant Z=0.0004 and a large fraction of binary stars are required to obtain the best agreement with both the distribution of stars across the CMD and with its morphology. An IMF like the one obtained by Kroupa et al. (1993) for the solar neighborhood, or steeper, is compatible with the data.

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The star formation history of the Fornax dwarf spheroidal galaxy

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310003200 ◽

2009 ◽

Vol 5 (S262) ◽

pp. 353-354

Author(s):

Enrico V. Held ◽

Eline Tolstoy ◽

Luca Rizzi ◽

Mary Cesetti ◽

Andrew A. Cole ◽

...

Keyword(s):

Star Formation ◽

Galaxy Evolution ◽

Stellar Population ◽

Main Sequence ◽

Dwarf Galaxy ◽

Star Formation History ◽

Stellar Content ◽

Formation History ◽

First Results ◽

History Of

AbstractWe present the first results of a comprehensive HST study of the star-formation history of Fornax dSph, based on WFPC2 imaging of 7 Fornax fields. Our observations reach the oldest main-sequence turnoffs, allowing us to address fundamental questions of dwarf galaxy evolution, such as the spatial variations in the stellar content, and whether the old stellar population is made up of stars formed in a very early burst or the result of a more continuous star formation.

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Star Formation Histories of Dwarf Galaxies from the Colour-Magnitude Diagrams of Their Resolved Stellar Populations

Advances in Astronomy ◽

10.1155/2010/158568 ◽

2010 ◽

Vol 2010 ◽

pp. 1-25 ◽

Cited By ~ 27

Author(s):

Michele Cignoni ◽

Monica Tosi

Keyword(s):

Star Formation ◽

Galaxy Formation ◽

Dwarf Galaxies ◽

Early Type ◽

Significant Difference ◽

Magnitude Diagram ◽

The Galaxy ◽

Show Evidence ◽

History Of ◽

Star Formation Histories

In this tutorial paper we summarize how the star formation (SF) history of a galactic region can be derived from the colour-magnitude diagram (CMD) of its resolved stars. The procedures to build synthetic CMDs and to exploit them to derive the SF histories (SFHs) are described, as well as the corresponding uncertainties. The SFHs of resolved dwarf galaxies of all morphological types, obtained from the application of the synthetic CMD method, are reviewed and discussed. To summarize: (1) only early-type galaxies show evidence of long interruptions in the SF activity; late-type dwarfs present rather continuous, orgasping, SF regimes; (2) a few early-type dwarfs have experienced only one episode of SF activity concentrated at the earliest epochs, whilst many others show extended or recurrent SF activity; (3) no galaxy experiencing now its first SF episode has been found yet; (4) no frequent evidence of strong SF bursts is found; (5) there is no significant difference in the SFH of dwarf irregulars and blue compact dwarfs, except for the current SF rates. Implications of these results on the galaxy formation scenarios are briefly discussed.

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