VERY STRONG EMISSION-LINE GALAXIES IN THE WFC3 INFRARED SPECTROSCOPIC PARALLEL SURVEY AND IMPLICATIONS FOR HIGH-REDSHIFT GALAXIES,

By H. Atek, B. Siana, Claudia Scarlata, M. Malkan, P. McCarthy, H. Teplitz, A. Henry, J. Colbert, C. Bridge, A. Bunker and 6 more. 2011

153 citations recorded by the source corpus.

The WFC3 Infrared Spectroscopic Parallel Survey uses the Hubble Space Telescope (HST) infrared grism capabilities to obtain slitless spectra of thousands of galaxies over a wide redshift range including the peak of star formation history of the universe. We select a population of very strong emission-line galaxies with rest-frame equivalent widths (EWs) higher than 200 Å. A total of 176 objects are found over the redshift range 0.35 < z < 2.3 in the 180 arcmin2 area that we have analyzed so far. This population consists of young and low-mass starbursts with high specific star formation rates (sSFR). After spectroscopic follow-up of one of these galaxies with Keck/Low Resolution Imaging Spectrometer, we report the detection at z = 0.7 of an extremely metal-poor galaxy with 12 + log(O/H) =7.47 ± 0.11. After estimating the active galactic nucleus fraction in the sample, we show that the high-EW galaxies have higher sSFR than normal star-forming galaxies at any redshift. We find that the nebular emission lines can substantially affect the total broadband flux density with a median brightening of 0.3 mag, with some examples of line contamination producing brightening of up to 1 mag. We show that the presence of strong emission lines in low-z galaxies can mimic the color-selection criteria used in the z ∼ 8 dropout surveys. In order to effectively remove low-redshift interlopers, deep optical imaging is needed, at least 1 mag deeper than the bands in which the objects are detected. Without deep optical data, most of the interlopers cannot be ruled out in the wide shallow HST imaging surveys. Finally, we empirically demonstrate that strong nebular lines can lead to an overestimation of the mass and the age of galaxies derived from fitting of their spectral energy distribution (SED). Without removing emission lines, the age and the stellar mass estimates are overestimated by a factor of 2 on average and up to a factor of 10 for the high-EW galaxies. Therefore, the contribution of emission lines should be systematically taken into account in SED fitting of star-forming galaxies at all redshifts.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b757387a40b8316143ec32c0b237475b07e4916f

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In Astronomy and Astrophysics

1. P. Hopkins
2. Richard S. Ellis
3. L. Hernquist
4. P. V. van Dokkum
5. M. Franx
6. C. Conroy
7. R. Bouwens
8. R. Dav'e

In Electrical and Electronic Engineering

1. Richard S. Ellis
2. R. Bouwens
3. P. Oesch
4. J. Dunlop
5. D. Stark
6. G. Illingworth
7. R. McLure
8. I. Labbé

In Instrumentation

1. Richard S. Ellis
2. P. V. van Dokkum
3. M. Franx
4. C. Conroy
5. R. Bouwens
6. I. Labbé
7. G. Illingworth
8. P. Oesch

Citations in the corpus

• Ionization state of inter-stellar medium in galaxies: evolution, SFR-M * -Z dependence, and ionizing photon escape (2013, background): “Recently, some studies have found galaxies with very strong nebular emission lines that are called extreme emission line galaxies (EELGs; e.g. Atek et al. 2011; van der Wel et al. 2011). van der Wel et al. (2011) investigate EELGs at z ∼ 1.7 in the CANDELS deep imaging data of HST/WFC3.”
• A CRITICAL ASSESSMENT OF PHOTOMETRIC REDSHIFT METHODS: A CANDELS INVESTIGATION (2013, background): “We provide the latter information since emission lines can have a significant effect on broad-band photometry and therefore the template SED fitting (e.g., Atek et al. 2011; Schaerer & de Barros 2012; Stark et al. 2013).”
• THE ABUNDANCE OF STAR-FORMING GALAXIES IN THE REDSHIFT RANGE 8.5–12: NEW RESULTS FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN (2012, background): “Independently, Atek et al. (2011) located a similar population in the WISP survey over 0.35 < z < 2.3 and comment specifically that such sources could contaminate dropout searches.”
• STELLAR MASSES FROM THE CANDELS SURVEY: THE GOODS-SOUTH AND UDS FIELDS (2014, background): “Indeed, strong nebular The Astrophysical Journal, 801:97 (17pp), 2015 March 10 Santini et al. lines in their spectra may mimic the Balmer and 4000 Å breaks, resulting in these sources being fitted better by older, passive, and more massive templates (see also Atek et al. 2011).”
• THE BRIGHTEST OF REIONIZING GALAXIES SURVEY: CONSTRAINTS ON THE BRIGHT END OF THE z ∼ 8 LUMINOSITY FUNCTION (2012, background): “(see Atek et al. 2011) and a V606 continuum that cannot be detected in the current data assuming its V606 − J125 is similar to that of the spiral galaxy.”
• Spectroscopic detection of C iv λ1548 in a galaxy at z = 7.045: implications for the ionizing spectra of reionization-era galaxies (2015, background): “The population of extreme emission line galaxies (EW = 500-1000 Å), relatively rare among z ' 1− 2 galaxies (e.g., Atek et al. 2011, van der Wel et al. 2011), appears to be ubiquitous at z ' 7 (Smit et al. 2014, 2015).”
• (Star)bursts of FIRE: observational signatures of bursty star formation in galaxies (2015, background): “However, some galaxies appear to be out of equilibrium in the sense that they are forming stars so rapidly that they will deplete their gas reservoirs on timescales of 10 − 100 Myr (Rodighiero et al. 2011; Atek et al. 2011, 2014; Maseda et al. 2014).”
• THE RELATION BETWEEN STAR FORMATION RATE AND STELLAR MASS FOR GALAXIES AT 3.5 ⩽ z ⩽ 6.5 IN CANDELS (2014, background): “Nebular emission is important because many galaxies at high redshift are observed to have intense star formation and high equivalent widths (EW) from emission lines (Erb et al. 2010; van der Wel et al. 2011; Atek et al. 2011; Brammer et al. 2013).”
• AN ATLAS OF GALAXY SPECTRAL ENERGY DISTRIBUTIONS FROM THE ULTRAVIOLET TO THE MID-INFRARED (2013, background): “Consequently, it can be very difficult to determine some properties of emission line galaxies (e.g., stellar masses) when only broadband photometry is available (e.g., Atek et al. 2011; Schaerer & de Barros 2009).”
• An extreme [O III] emitter at z = 3.2: a low metallicity Lyman continuum source (2015, background): “The measured line ratios among the Hβ+[O iii]λλ4959, 5007 suggest the [O iii]λ5007 rest-frame equivalent width is ' 1100Å, with a similar value to the few extreme cases reported in literature at z ∼ 1 − 2 (Atek et al. 2011; Amorı́n et al. 2014b; Maseda et al. 2014).”
• ARE ULTRA-FAINT GALAXIES AT z = 6–8 RESPONSIBLE FOR COSMIC REIONIZATION? COMBINED CONSTRAINTS FROM THE HUBBLE FRONTIER FIELDS CLUSTERS AND PARALLELS (2015, background): “Alternatively, the Lyman break colors can also be mimicked by extremely strong emission lines in z = 1− 3 star-forming galaxies (e.g., Atek et al. 2011, 2014a; van der Wel et al. 2011).”
• A CENSUS OF STAR-FORMING GALAXIES IN THE Z ∼ 9–10 UNIVERSE BASED ON HST+SPITZER OBSERVATIONS OVER 19 CLASH CLUSTERS: THREE CANDIDATE Z ∼ 9–10 GALAXIES AND IMPROVED CONSTRAINTS ON THE STAR FORMATION RATE DENSITY AT Z ∼ 9.2 (2012, background): “Another possible source of contamination is from extreme emission-line galaxies (EELGs) with strong [O iii]+Hβ emission, such as recently discovered by van der Wel et al. (2011) and Atek et al. (2011) in the CANDELS (Grogin et al. 2011; Koekemoer et al. 2012) or WISP (Atek et al. 2010) programs.”
• THE GRISM LENS-AMPLIFIED SURVEY FROM SPACE (GLASS). I. SURVEY OVERVIEW AND FIRST DATA RELEASE (2015, background): “…of spatially resolved star formation (Nelson et al. 2012); the detection of rare galaxies with strong emission lines and faint continuum emission (Atek et al. 2011); and the measurement of absorption line redshifts for z > 1 galaxies (van Dokkum et al. 2011; Newman et al. 2013) Current HST…”
• UV LUMINOSITY FUNCTIONS AT REDSHIFTS z ∼ 4 TO z ∼ 10: 10,000 GALAXIES FROM HST LEGACY FIELDS (2014, background): “Another potential contaminant of our high-redshift samples are from so-called extreme emission-line galaxies, where a significant fraction of the flux from a galaxy is concentrated into a small number of very high-equivalent-width emission lines (van der Wel et al. 2011; Atek et al. 2011).”
• Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies (2014, background): “We show that H-poor SLSNe show a preference for a class of low-mass, metal-poor, intensively star-forming galaxies with strong nebular emission lines and a hard ionizing radiation field, often referred to as Extreme Emission Line Galaxies (EELGs; e.g. Atek et al. 2011; Amorı́n et al. 2014a,b).”
• EVIDENCE FOR UBIQUITOUS HIGH-EQUIVALENT-WIDTH NEBULAR EMISSION IN z ∼ 7 GALAXIES: TOWARD A CLEAN MEASUREMENT OF THE SPECIFIC STAR-FORMATION RATE USING A SAMPLE OF BRIGHT, MAGNIFIED GALAXIES (2013, background): “Extreme line emission with EWs greater 1000Å has been found at lower redshift in low mass galaxies (van der Wel et al., 2011; Atek et al., 2011).”
• THE MOST LUMINOUS z ∼ 9–10 GALAXY CANDIDATES YET FOUND: THE LUMINOSITY FUNCTION, COSMIC STAR-FORMATION RATE, AND THE FIRST MASS DENSITY ESTIMATE AT 500 Myr (2013, background): “These are a particular concern in data sets which do not have very deep optical data to establish a strong spectral break through non-detections (see, e.g., Atek et al. 2011; van der Wel et al. 2011; Hayes et al. 2012).”