First Results From the Noao Survey of the Outer Limits of the Magellanic Clouds

Saha, Abhijit; Olszewski, Edward W.; Brondel, B. J.; Olsen, Knut; Knezek, Patricia; Harris, Jason; Smith, Chris; Subramaniam, Annapurni; Claver, Jenna; Rest, A.; Seitzer, Patrick; Cook, K. H.; Minniti, D.; Suntzeff, Nicholas B.

doi:10.1088/0004-6256/140/6/1719

Cited by 93 publications

(120 citation statements)

References 54 publications

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“…They observed an outside-to-inside quenching of star-formation, such that, a field at 2.3 • is currently active in star-formation, while fields at 4.4 • , 5.5 • , and 7.1 • have 100 Myr, 0.8 Gyr, and 1.5 Gyr old stars as the youngest population, respectively. Thus, the age of the youngest stars in each field gradually increases with distance from the center and the population is found to be older on average towards the outer part of the galaxy (Saha et al 2010;Gallart et al 2009). It will be interesting to ascertain out to which radius this outside-in quenching of star-formation can be traced.…”

Section: Introductionmentioning

confidence: 88%

The recent star-formation history of the Large and Small Magellanic Clouds

Indu

Subramaniam

2011

A&A

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Aims. Recent interactions between the Large and the Small Magellanic Clouds (LMC and SMC) and the Milky Way can be understood by studying their recent star formation history. This study aims to detect any directional or propagating star formation in the last 500 Myr. Methods. We traced the age of the last star-formation event (LSFE) in the inner Large and Small Magellanic Cloud (L&SMC) using the photometric data in V and I passbands from the Optical Gravitational Lensing Experiment (OGLE-III) and the Magellanic Cloud Photometric Survey (MCPS). The LSFE is estimated from the main sequence turn-off point in the color-magnitude diagram (CMD) of a subregion. After correcting for extinction, the turn-off magnitude is converted to age, which represents the LSFE in a region.Results. The spatial distribution of the age of the LSFE shows that the star-formation has shrunk to within the central regions in the last 100 Myr in both the galaxies. The location as well as age of LSFE is found to correlate well with those of the star cluster in both the Clouds. The SMC map shows two separate concentrations of young star-formation, one near the center and the other near the wing. We detect peaks of star-formation at 0-10 Myr and 90-100 Myr in the LMC, and 0-10 Myr and 50-60 Myr in the SMC. The quenching of star-formation in the LMC is found to be asymmetric with respect to the optical center such that most of the young star forming regions are located to the north and east. On deprojecting the data onto the LMC plane, the recent star-formation appears to be stretched in the northeast direction and the HI gas is found to be distributed preferentially in the north. We found that the centroid is shifted to the north during the time interval 200-40 Myr, whereas it is found to have shifted to the northeast in the last 40 Myr. In the SMC, we detect a shift in the centroid of the population younger than 500 Myr and as young as 40 Myr in the direction of the LMC. Conclusions. We propose that the HI gas in the LMC has been pulled to the north of the LMC in the last 200 Myr because of the gravitational attraction of our Galaxy at the time of perigalactic passage. The shifted HI gas was preferentially compressed in the north during the time interval 200-40 Myr and in the northeast in the last 40 Myr, owing to the motion of the LMC in the Galactic halo. The recent star-formation in the SMC is due to the combined gravitational effect of the LMC and the perigalactic passage.

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Section: Introductionmentioning

confidence: 88%

The recent star-formation history of the Large and Small Magellanic Clouds

Indu

Subramaniam

2011

A&A

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“…The methodology used in this section is described in detail in Saha et al (2010). DoPHOT uses an analytical function as a model PSF for describing different object types.…”

Section: Photometrymentioning

confidence: 99%

Deep wide-field imaging down to the oldest main sequence turn-offs in the Sculptor dwarf spheroidal galaxy

Boer

Tolstoy

Saha

et al. 2011

A&A

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We present wide-field photometry of resolved stars in the nearby Sculptor dwarf spheroidal galaxy using CTIO/MOSAIC, going down to the oldest main sequence turn-off. The accurately flux calibrated wide field colour-magnitude diagrams can be used to constrain the ages of different stellar populations, and also their spatial distribution. The Sculptor dSph contains a predominantly ancient stellar population (>10 Gyr old) which can be easily resolved into individual stars. A galaxy dominated by an old population provides a clear view of ancient processes of galaxy formation unimpeded by overlying younger populations. By using spectroscopic metallicities of RGB stars in combination with our deep main sequence turn-off photometry we can constrain the ages of different stellar populations with particular accuracy. We find that the known metallicity gradient in Sculptor is well matched to an age gradient. This is the first time that this link with age has been directly quantified. This gradient has been previously observed as a variation in horizontal branch properties and is now confirmed to exist for main sequence turn-offs as well. It is likely the Sculptor dSph first formed an extended metal-poor population at the oldest times, and subsequent more metal-rich, younger stars were formed more towards the centre until the gas was depleted or lost roughly 7 Gyr ago. The fact that these clear radial gradients have been preserved up to the present day is consistent with the apparent lack of signs of recent tidal interactions.

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“…Furthermore, carbon stars from Kunkel et al (1997) follow disk kinematics out to ∼13° (van der Marel et al 2002). Finally, the Outer Limits Survey (OLS; Saha et al 2010) used deep photometry to study old LMC main-sequence stars in select fields far from the LMC center and found that in the north they followed the disk exponential profile out to ∼16°.…”

Section: Introductionmentioning

confidence: 99%

SMASH: Survey of the MAgellanic Stellar History

Nidever

Olsen

Walker

et al. 2017

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The Large and Small Magellanic Clouds are unique local laboratories for studying the formation and evolution of small galaxies in exquisite detail. The Survey of the MAgellanic Stellar History (SMASH) is an NOAO community Dark Energy Camera (DECam) survey of the Clouds mapping 480 deg 2 (distributed over ∼2400 square degrees at ∼20% filling factor) to ∼24thmag in ugriz. The primary goals of SMASH are to identify low surface brightness stellar populations associated with the stellar halos and tidal debris of the Clouds, and to derive spatially resolved star formation histories. Here, we present a summary of the survey, its data reduction, and a description of the first public Data Release (DR1). The SMASH DECam data have been reduced with a combination of the NOAO Community Pipeline, the PHOTRED automated point-spread-function photometry pipeline, and custom calibration software. The astrometric precision is ∼15 mas and the accuracy is ∼2 mas with respect to the Gaia reference frame. The photometric precision is ∼0.5%-0.7% in griz and ∼1% in u with a calibration accuracy of ∼1.3% in all bands. The median 5σ point source depths in ugriz are 23.9, 24.8, 24.5, 24.2, and 23.5 mag. The SMASH data have already been used to discover the Hydra II Milky Way satellite, the SMASH 1 old globular cluster likely associated with the LMC, and extended stellar populations around the LMC out to R∼18.4 kpc. SMASH DR1 contains measurements of ∼100 million objects distributed in 61 fields. A prototype version of the NOAO Data Lab provides data access and exploration tools.

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First Results From the Noao Survey of the Outer Limits of the Magellanic Clouds

Cited by 93 publications

References 54 publications

The recent star-formation history of the Large and Small Magellanic Clouds

The recent star-formation history of the Large and Small Magellanic Clouds

Deep wide-field imaging down to the oldest main sequence turn-offs in the Sculptor dwarf spheroidal galaxy

SMASH: Survey of the MAgellanic Stellar History

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