MASSIVE AND NEWLY DEAD: DISCOVERY OF A SIGNIFICANT POPULATION OF GALAXIES WITH HIGH-VELOCITY DISPERSIONS AND STRONG BALMER LINES AT z ∼ 1.5 FROM DEEP KECK SPECTRA AND HST/WFC3 IMAGING
MASSIVE AND NEWLY DEAD: DISCOVERY OF A SIGNIFICANT POPULATION OF GALAXIES WITH HIGH-VELOCITY DISPERSIONS AND STRONG BALMER LINES AT z ∼ 1.5 FROM DEEP KECK SPECTRA AND HST/WFC3 IMAGING
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大质量和新死亡：从深 KECK 光谱和 HST/WFC3 成像中发现 z 〜 1.5 处具有高速色散和强巴尔默线的大量星系
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发表时间：
2012
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影响因子：
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通讯作者：
M. Kriek
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作者：
R. Bezanson;P. V. van Dokkum;J. van de Sande;M. Franx;M. Kriek
We present deep Keck/LRIS spectroscopy and Hubble Space Telescope/WFC3 imaging in the rest-frame optical for a sample of eight galaxies at z ∼ 1.5 with high photometrically determined stellar masses.这些数据与五个甚大望远镜/X-Shooter 光谱相结合。我们发现这13个星系具有高速色散，中位数为σ = 301 km s−1。这个高值与它们相对较高的恒星质量和紧凑的尺寸是一致的。我们利用巴尔默吸收线的强度来研究它们的恒星种群，巴尔默吸收线对灰尘吸收不敏感。我们发现巴尔默吸收强度的范围很大，许多星系显示出非常强烈的线条，表明年轻。 The median HδA equivalent width, determined directly or inferred from the H10 line, is 5.4 Å, indicating a luminosity-weighted age of ∼1 Gyr. Although this value may be biased toward higher values because of selection effects, high-dispersion galaxies with such young ages are extremely rare in the local universe. Interestingly, we do not find a simple correlation with rest-frame U − V color: some of the reddest galaxies have very strong Balmer absorption lines, which may indicate the importance of multiple bursts of star formation.这些结果表明，许多 z ∼ 1.5 处的高色散星系最近都被淬灭了。 This implies that there must be a population of star-forming progenitors at z ∼ 2 with high velocity dispersions or linewidths, which are notoriously absent from CO/Hα selected surveys.
We present deep Keck/LRIS spectroscopy and Hubble Space Telescope/WFC3 imaging in the rest-frame optical for a sample of eight galaxies at z ∼ 1.5 with high photometrically determined stellar masses. The data are combined with five Very Large Telescope/X-Shooter spectra. We find that these 13 galaxies have high velocity dispersions, with a median of σ = 301 km s−1. This high value is consistent with their relatively high stellar masses and compact sizes. We study their stellar populations using the strength of Balmer absorption lines, which are not sensitive to dust absorption. We find a large range in Balmer absorption strength, with many galaxies showing very strong lines indicating young ages. The median HδA equivalent width, determined directly or inferred from the H10 line, is 5.4 Å, indicating a luminosity-weighted age of ∼1 Gyr. Although this value may be biased toward higher values because of selection effects, high-dispersion galaxies with such young ages are extremely rare in the local universe. Interestingly, we do not find a simple correlation with rest-frame U − V color: some of the reddest galaxies have very strong Balmer absorption lines, which may indicate the importance of multiple bursts of star formation. These results demonstrate that many high-dispersion galaxies at z ∼ 1.5 were recently quenched. This implies that there must be a population of star-forming progenitors at z ∼ 2 with high velocity dispersions or linewidths, which are notoriously absent from CO/Hα selected surveys.