An accelerated K-means clustering algorithm using selection and erasure rules

Lee, Suiang-Shyan; Lin, Ja‐Chen

doi:10.1631/jzus.c1200078

Cited by 11 publications

(3 citation statements)

References 13 publications

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“…(3) BV Ri ′ z ′ data are obtained from Subaru/Suprime-Cam, J data from KPNO/NEWFIRM, K data from UKIRT/WFCAM, and [3.6] − [8.0] data from Spitzer/IRAC. Optical data are provided by T. Hayashino (see also Hayashino et al 2004), J data are obtained from the NewHα survey (Ly et al 2011;Lee et al 2012). K data are collected from the WFCAM data access page, and Spitzer data from the Spitzer Heritage Archive.…”

Section: Other Emission Line Detectionsmentioning

confidence: 99%

“…Note, however, that since the EWs are sensitive to recent starbursts, LAEs on instantaneous tracks are not necessarily very young, but can be experiencing a burst after a continuous star-formation. Such a combination of burst plus continuous star-formation is indeed needed to explain the EWs of Hα and optical colors observed in local dwarf galaxies (Lee 2006). An LAE with such a combined star-formation history will be on a track of instantaneous burst during starburst phases and on a track of constant star-formation for the remaining time.…”

Section: Physical Properties Inferred From Lyα and Hα Emissionmentioning

confidence: 99%

“…At z = 2.2, important nebular lines such as [O ii]λ3727, Hβ, [O iii]λλ5007,4959,Hα,[N ii]λ6584, are observable from the ground. Initial results were based on using three narrowbands to detect Lyα, [O ii], and Hα over the same volumes (Nakajima et al 2012; see also Lee et al 2012 andLy et al 2011 for the two NIR narrowbands and the NewHα Survey).…”

Section: Introductionmentioning

confidence: 99%

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FIRST SPECTROSCOPIC EVIDENCE FOR HIGH IONIZATION STATE AND LOW OXYGEN ABUNDANCE IN Lyα EMITTERS,

Nakajima

Ouchi

Shimasaku

et al. 2013

ApJ

132

177

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We present results from Keck/NIRSPEC and Magellan/MMIRS follow-up spectroscopy of Lyα emitters (LAEs) at z = 2.2 identified in our Subaru narrowband survey. We successfully detect Hα emission from seven LAEs, and perform a detailed analysis of six LAEs free from AGN activity, two out of which, CDFS-3865 and COSMOS-30679, have [O ii] and [O iii] line detections. They are the first [O ii]-detected LAEs at high-z, and their [O iii]/[O ii] ratios and R23-indices provide the first simultaneous determinations of ionization parameter and oxygen abundance for LAEs. CDFS-3865 has a very high ionization parameter (q ion = 2.5 +1.7 −0.8 × 10 8 cm s −1 ) and a low oxygen abundance (12 + log(O/H) = 7.84 +0.24−0.25 ) in contrast with moderate values of other high-z galaxies such as Lymanbreak galaxies (LBGs). COSMOS-30679 also possesses a relatively high ionization parameter (q ion = 8 +10 −4 ×10 7 cm s −1 ) and a low oxygen abundance (12+log(O/H) = 8.18 +0.28 −0.28 ). Both LAEs appear to fall below the mass-metallicity relation of z ∼ 2 LBGs. Similarly, a low metallicity of 12 + log(O/H) < 8.4 is independently indicated for typical LAEs from a composite spectrum and the [N ii]/Hα index. Such high ionization parameters and low oxygen abundances can be found in local star-forming galaxies, but this extreme local population occupies only ∼ 0.06% of the SDSS spectroscopic galaxy sample with a number density ∼ 100 times smaller than that of LAEs. With their high ionization parameters and low oxygen abundances, LAEs would represent an early stage of galaxy formation dominated by massive stars in compact star-forming regions. High-q ion galaxies like LAEs would produce ionizing photons efficiently with a high escape fraction achieved by density-bounded Hii regions, which would significantly contribute to cosmic reionization at z > 6.

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Section: Other Emission Line Detectionsmentioning

confidence: 99%

Section: Physical Properties Inferred From Lyα and Hα Emissionmentioning

confidence: 99%