Contamination by field late-M, L, and T dwarfs in deep surveys
Contamination by field late-M, L, and T dwarfs in deep surveys
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深层调查中M、L和T期晚期矮星的现场污染
DOI：
10.1051/0004-6361:200809520
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发表时间：
2008
影响因子：
6.5
通讯作者：
R. Klement
中科院分区：
文献类型：
--
作者：
José A. Caballero;José A. Caballero;A. Burgasser;R. Klement
上下文。年轻星团和高红移类星体中恒星下天体的深度光度测量受到不同日心距离的污染源的影响。如果没有正确地考虑，污染可能会对初始质量函数的确定和类星体的识别产生强烈的影响。目标。我们详细计算了深部调查中很晚光谱类型(中晚期M、L和T)的场矮星对背景和前景的污染，为计算提供了数据和工具。方法：研究方法。我们采用了最新的模型和文献中的数据，其中包括：(I)按指数规律建立的银河系薄盘模型；(Ii)晚型矮星的长度和高度尺度；以及(Iii)每种光谱类型的矮星的局部空间密度、绝对星等和颜色。结果。我们推导了依赖于日心距和星系坐标(L，b)的薄盘空间密度的简化表达式，并将其积分到本调查所研究的截锥体中。作为实际应用，我们计算了沿年轻的猎户座星系团方向的非常深的(i=21−29mag)L和T型场矮星的数目。最微弱的污染物数量的增加可能会阻碍对星系团中M<；0.003 M�不透明质量极限的研究。
Context. Deep photometric surveys of substellar objects in young clusters and high-redshift quasars are affected by contaminant sources at different heliocentric distances. If not correctly taken into account, the contamination may have a strong effect on the Initial Mass Function determination and on the identification of quasars. Aims. We calculate in detail the back- and foreground contamination by field dwarfs of very late spectral types (intermediate and late M, L, and T) in deep surveys and provide the data and tools for the computation. Methods. We adopt the latest models and data from the literature, which include the following: (i) a model of the Galactic thin disc by an exponential law; (ii) the length and height scales of late-type dwarfs; and (iii) the local spatial densities, absolute magnitudes, and colours of dwarfs for each spectral type. Results. We derive a simplified expression for the spatial density in the thin disc that depends on the heliocentric distance and the galactic coordinates (l, b) and integrate this into the truncated cone studied in the survey. As a practical application, we compute the numbers of L- and T-type field dwarfs in very deep (I = 21−29 mag) surveys in the direction of the young σ Orionis cluster. The increasing number of contaminants at the faintest magnitudes could inhibit the study of the opacity mass limit at M < 0.003 M� in the cluster.