Rest-Frame Ultraviolet Spectra of z ∼ 3 Lyman Break Galaxies

By A. Shapley, C. Steidel, M. Pettini, K. Adelberger. 2003

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We present the results of a systematic study of the rest-frame UV spectroscopic properties of Lyman break galaxies (LBGs). The database of almost 1000 LBG spectra proves useful for constructing high signal-to-noise composite spectra. The composite spectrum of the entire sample reveals a wealth of features attributable to hot stars, H II regions, dust, and outflowing neutral and ionized gas. By grouping the database according to galaxy parameters such as Lyα equivalent width, UV spectral slope, and interstellar kinematics, we isolate some of the major trends in LBG spectra that are least compromised by selection effects. We find that LBGs with stronger Lyα emission have bluer UV continua, weaker low-ionization interstellar absorption lines, smaller kinematic offsets between Lyα and the interstellar absorption lines, and lower star formation rates. There is a decoupling between the dependence of low- and high-ionization outflow features on other spectral properties. Additionally, galaxies with rest-frame WLyα ≥ 20 Å in emission have weaker than average high-ionization lines and nebular emission lines that are significantly stronger than in the sample as a whole. Most of the above trends can be explained in terms of the properties of the large-scale outflows seen in LBGs. According to this scenario, the appearance of LBG spectra is determined by a combination of the covering fraction of outflowing neutral gas, which contains dust and the range of velocities over which this gas is absorbing. In contrast, the strengths of collisionally excited nebular emission lines should not be affected by the nature of the outflow, and variations in these lines may indicate differences in the temperatures and metallicities in H II regions of galaxies with very strong Lyα emission. Higher sensitivity and spectral resolution observations are still required for a full understanding of the covering fraction and velocity dispersion of the outflowing neutral gas in LBGs and its relationship to the escape fraction of Lyman continuum radiation in galaxies at z ~ 3.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/2f7d3c14f22d7a7e50c41556f902853ba8659632

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Citations in the corpus

Lyα Emission-Line Galaxies at z = 3.1 in the Extended Chandra Deep Field-South (2007, methodology): “The equivalent width distribution of Figure 9 also differs dramatically from that found by Shapley et al. (2003) for a sample of z 3 LBGs.”
Lyα Emitters at z = 5.7 in the Subaru Deep Field (2006, background): “It is also interesting to note that a similar trend has been found for LBGs at z ∼ 3 although their absolute EW values are much lower than our LAEs’ (Shapley et al. 2003).”
Galactic winds driven by cosmic ray streaming (2012, background): “…Galaxies at z ∼ 3 have C© 2012 The Authors Monthly Notices of the Royal Astronomical Society C© 2012 RASDownloaded from https://academic.oup.com/mnras/article-abstract/423/3/2374/2460323 by guest on 29 July 2018 also revealed the presence of winds (e.g. Adelberger et al. 2003; Shapley et al. 2003).”
Galaxies with Wolf-Rayet signatures in the low-redshift Universe. A survey using the Sloan Digital Sky Survey (2008, background): “While interesting in their own rights most of the galaxies under investigation here show very strong star formation activity with many showing SFR/M∗ similar to that of high redshift Lyman-break galaxies (e.g. Steidel et al. 2001, 2003; Shapley et al. 2003).”
Keeping the Universe ionized: photoheating and the clumping factor of the high-redshift intergalactic medium (2008, methodology): “We use η = 2 and vw = 600 km s −1, consistent with observations of local (e.g. Veilleux, Cecil, & Bland-Hawthorn 2005) and redshift z ≈ 3 (Shapley et al. 2003) starburst galaxies.”
COMPLETING THE CENSUS OF Lyα EMITTERS AT THE REIONIZATION EPOCH (2011, background): “Shapley et al. (2003) found the kinematic offset implied by the relative redshifts of Lyα emission and low-ionization interstellar absorption lines in an LBG sample at z ∼ 3.”
Studying reionization with Lyα emitters (2007, background): “This value for vw is motived by the average velocity offset of the Lyα line in strong emitters at z ≈ 3 (Shapley et al. 2003).”
THE MOSDEF SURVEY: ELECTRON DENSITY AND IONIZATION PARAMETER AT z ∼ 2.3 (2015, background): “…al. 2013) and compact sizes (van der Wel et al. 2014), combined with high rates of star formation (Shivaei et al. 2015), significant feedback driving outflows (Shapley et al. 2003; Steidel et al. 2010), and high level of turbulence observed in z ∼ 2 disk galaxies (Förster Schreiber et al. 2009).”
Dusty Star Forming Galaxies at High Redshift (2014, background): “Spectroscopic campaigns of ∼500 M⊙yr−1 850 µm-selected SMGs have often found bright emission lines with no detected continuum (Chapman et al., 2003b, 2005), with emission-line-to-continuum ratios far higher than observed in, e.g. ∼10 M⊙yr−1 Lyman-Break Galaxies (Shapley et al., 2003).”
THE IMPACT OF COLD GAS ACCRETION ABOVE A MASS FLOOR ON GALAXY SCALING RELATIONS (2009, background): “This strong evolution of the SFR sequence implies that distant z ∼ 2 SFGs with M⋆ > 10 10.6M⊙ had SFRs in excess of 100 M⊙ yr −1(Shapley et al. 2003; Erb et al. 2006a; Grazian et al. 2007; Daddi et al. 2007).”
A critical analysis of the ultraviolet continuum slopes (β) of high-redshift galaxies: no evidence (yet) for extreme stellar populations at z > 6 (2011, background): “For example, one long-sought distinctive spectral signature of the first generation of galaxies is relatively strong HeII emission at λrest = 1640Å (e.g. Shapley et al. 2003, Nagao et al. 2008, di Serego Alighieri et al. 2008).”
Properties of Lyα emitters around the radio galaxy MRC 0316 257 (2005, background): “The median UV continuum slope isβ = −1.76, bluer than the average slope of LBGs with Lyα emission (β ∼ −1.09; Shapley et al., 2003).”
An extreme [O III] emitter at z = 3.2: a low metallicity Lyman continuum source (2015, result): “This is in line with the results from Shapley et al. (2003) at z ∼ 3: galaxies with high Lyα equivalent width exhibit much weaker low-ionization absorption lines than galaxies with low EW(Lyα).”
Probing reionization with Lyman α emission lines (2003, background): “High velocity (∼360 km s−1) redshifts of Lyman α emission compared to other interstellar features are observed in z = 3 Lyman Break galaxies (Shapley et al. 2003); QSO absorption line cross-correlation suggests that these winds may have blown to large distances (∼0.2 pMpc; Adelberger et al. 2003).”
Evolution in the properties of Lyman-α emitters from redshifts z ~ 3 to z ~ 2 (2008, result): “This relation was previously observed for LBGs (Shapley et al. 2003).”
Galaxies–intergalactic medium interaction calculation – I. Galaxy formation as a function of large-scale environment (2009, background): “However, observed starburst galaxies exhibit signs of galaxy-wide winds (Heckman, Armus & Miley 1990; Martin 1999; Pettini et al. 2002; Adelberger et al. 2003; Shapley et al. 2003; Wilman et al. 2005; Swinbank et al. 2007) that are thought to be responsible for enriching the IGM with metals.”
Hierarchical formation of bulgeless galaxies: why outflows have low angular momentum (2010, background): “Indeed, outflows have been detected at high redshift from Lyman-break selected galaxies (Pettini et al. 1998; Simcoe et al. 2002; Shapley et al. 2003; Adelberger et al. 2005), as well as gravitationally lensed galaxies (Pettini et al. 2000).”
ON THE STELLAR POPULATIONS AND EVOLUTION OF STAR-FORMING GALAXIES AT 6.3 < z ⩽ 8.6 (2009, background): “Among thez∼ 3 galaxy population, Shapley et al. (2003) showed roughly 25–30% of the predominantly fainter LBG population exhibited Lyα in emission with sufficient strength to be selected as a LAE via narrowband surveys (with rest–frame equivalent width≥ 20 Å).”