scholarly journals The MOSDEF-LRIS Survey: The Interplay Between Massive Stars and Ionized Gas in High-Redshift Star-Forming Galaxies1

2020 ◽  
Author(s):  
Michael W Topping ◽  
Alice E Shapley ◽  
Naveen A Reddy ◽  
Ryan L Sanders ◽  
Alison L Coil ◽  
...  
Keyword(s):  
Emission Line ◽  
High Redshift ◽  
Optical Emission ◽  
Continuum Emission ◽  
Joint Analysis ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Composite Spectra ◽  
Local Sequence ◽  
Ionization Parameter

Abstract We present a joint analysis of rest-UV and rest-optical spectra obtained using Keck/LRIS and Keck/MOSFIRE for a sample of 62 star-forming galaxies at z ∼ 2.3. We divide our sample into two bins based on their location in the [OIII]5007/Hβ vs. [NII]6584/Hα BPT diagram, and perform the first differential study of the rest-UV properties of massive ionizing stars as a function of rest-optical emission-line ratios. Fitting BPASS stellar population synthesis models, including nebular continuum emission, to our rest-UV composite spectra, we find that high-redshift galaxies offset towards higher [OIII]λ5007/Hβ and [NII]λ6584/Hα have younger ages ($\log (\textrm {~Age/yr})=7.20^{+0.57}_{-0.20}$) and lower stellar metallicities ($Z_*=0.0010^{+0.0011}_{-0.0003}$) resulting in a harder ionizing spectrum, compared to the galaxies in our sample that lie on the local BPT star-forming sequence ($\log (\textrm {Age/yr})=8.57^{+0.88}_{-0.84}$, $Z_*=0.0019^{+0.0006}_{-0.0006}$). Additionally, we find that the offset galaxies have an ionization parameter of $\log (U)=-3.04^{+0.06}_{-0.11}$ and nebular metallicity of ($12+\log (\textrm {~O/H})=8.40^{+0.06}_{-0.07}$), and the non-offset galaxies have an ionization parameter of $\log (U)=-3.11^{+0.08}_{-0.08}$ and nebular metallicity of $12+\log (\textrm {~O/H})=8.30^{+0.05}_{-0.06}$. The stellar and nebular metallicities derived for our sample imply that the galaxies offset from the local BPT relation are more α-enhanced ($7.28^{+2.52}_{-2.82}\textrm {~O/Fe}_{\odot }$) compared to those consistent with the local sequence ($3.04^{+0.95}_{-0.54}\textrm {~O/Fe}_{\odot }$). However, even galaxies that are entirely consistent with the local nebular excitation sequence appear to be α-enhanced – in contrast with typical local systems. Such differences must be considered when estimating gas-phase oxygen abundances at high redshift based on strong emission-line ratios. Specifically, a similarity in the location of high-redshift and local galaxies in the BPT diagram may not be indicative of a similarity in their physical properties.

scholarly journals New methods for identifying Lyman continuum leakers and reionization-epoch analogues

2020 ◽  
Vol 498 (1) ◽  
pp. 164-180 ◽  
Author(s):  
Harley Katz ◽  
Dominika Ďurovčíková ◽  
Taysun Kimm ◽  
Joki Rosdahl ◽  
Jeremy Blaizot ◽  
...  
Keyword(s):  
Emission Line ◽  
Galaxy Formation ◽  
Dwarf Galaxy ◽  
High Redshift ◽  
Indirect Methods ◽  
High Redshift Galaxies ◽  
Lyman Continuum ◽  
The Universe ◽  
Ionization Parameter ◽  
Redshift Galaxies

ABSTRACT Identifying low-redshift galaxies that emit Lyman continuum radiation (LyC leakers) is one of the primary, indirect methods of studying galaxy formation in the epoch of reionization. However, not only has it proved challenging to identify such systems, it also remains uncertain whether the low-redshift LyC leakers are truly ‘analogues’ of the sources that reionized the Universe. Here, we use high-resolution cosmological radiation hydrodynamics simulations to examine whether simulated galaxies in the epoch of reionization share similar emission line properties to observed LyC leakers at z ∼ 3 and z ∼ 0. We find that the simulated galaxies with high LyC escape fractions (fesc) often exhibit high O32 and populate the same regions of the R23–O32 plane as z ∼ 3 LyC leakers. However, we show that viewing angle, metallicity, and ionization parameter can all impact where a galaxy resides on the O32–fesc plane. Based on emission line diagnostics and how they correlate with fesc, lower metallicity LyC leakers at z ∼ 3 appear to be good analogues of reionization-era galaxies. In contrast, local [S ii]-deficient galaxies do not overlap with the simulated high-redshift LyC leakers on the S ii Baldwin–Phillips–Terlevich (BPT) diagram; however, this diagnostic may still be useful for identifying leakers. We use our simulated galaxies to develop multiple new diagnostics to identify LyC leakers using infrared and nebular emission lines. We show that our model using only [C ii]158 μm and [O iii]88 μm can identify potential leakers from non-leakers from the local Dwarf Galaxy Survey. Finally, we apply this diagnostic to known high-redshift galaxies and find that MACS 1149_JD1 at z = 9.1 is the most likely galaxy to be actively contributing to the reionization of the Universe.

scholarly journals Constraints on the production and escape of ionizing radiation from the emission-lines of metal-poor star-forming galaxies

2019 ◽  
Vol 15 (S352) ◽  
pp. 121-122
Author(s):  
A. Plat ◽  
S. Charlot ◽  
G. Bruzual ◽  
A. Feltre ◽  
A. Vidal-Garca ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Emission Line ◽  
Active Galactic Nuclei ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Radiative Shocks ◽  
Metal Poor Star

AbstractTo understand how the nature of the ionizing sources and the leakage of ionizing photons in high-redshift galaxies can be constrained from their emission-line spectra, we compare emission-line models of star-forming galaxies including leakage of ionizing radiation, active galactic nuclei (AGN) and radiative shocks, with observations of galaxies at various redshifts with properties expected to approach those of primeval galaxies.

scholarly journals The MOSDEF survey: direct-method metallicities and ISM conditions at z ∼ 1.5–3.5

2019 ◽  
Vol 491 (1) ◽  
pp. 1427-1455 ◽  
Author(s):  
Ryan L Sanders ◽  
Alice E Shapley ◽  
Naveen A Reddy ◽  
Mariska Kriek ◽  
Brian Siana ◽  
...  
Keyword(s):  
Star Formation Rate ◽  
Direct Method ◽  
High Redshift ◽  
Formation Rate ◽  
Strong Line ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Rapid Formation ◽  
Binary Evolution ◽  
Ionization Parameter

ABSTRACT We present detections of [O iii] λ4363 and direct-method metallicities for star-forming galaxies at z = 1.7–3.6. We combine new measurements from the MOSFIRE Deep Evolution Field (MOSDEF) survey with literature sources to construct a sample of 18 galaxies with direct-method metallicities at z > 1, spanning 7.5 < 12+log(O/H) < 8.2 and log(M*/M⊙) = 7–10. We find that strong-line calibrations based on local analogues of high-redshift galaxies reliably reproduce the metallicity of the z > 1 sample on average. We construct the first mass–metallicity relation at z > 1 based purely on direct-method O/H, finding a slope that is consistent with strong-line results. Direct-method O/H evolves by ≲0.1 dex at fixed M* and star formation rate from z ∼ 0 to 2.2. We employ photoionization models to constrain the ionization parameter and ionizing spectrum in the high-redshift sample. Stellar models with supersolar O/Fe and binary evolution of massive stars are required to reproduce the observed strong-line ratios. We find that the z > 1 sample falls on the z ∼ 0 relation between ionization parameter and O/H, suggesting no evolution of this relation from z ∼ 0 to z ∼ 2. These results suggest that the offset of the strong-line ratios of this sample from local excitation sequences is driven primarily by a harder ionizing spectrum at fixed nebular metallicity compared to what is typical at z ∼ 0, naturally explained by supersolar O/Fe at high redshift caused by rapid formation time-scales. Given the extreme nature of our z > 1 sample, the implications for representative z ∼ 2 galaxy samples at ∼1010 M⊙ are unclear, but similarities to z > 6 galaxies suggest that these conclusions can be extended to galaxies in the epoch of reionization.

scholarly journals Rest-frame UV and optical emission line diagnostics of ionized gas properties: a test case in a star-forming knot of a lensed galaxy at z ∼ 1.7

2019 ◽  
Vol 488 (4) ◽  
pp. 5862-5886 ◽  
Author(s):  
Ayan Acharyya ◽  
Lisa J Kewley ◽  
Jane R Rigby ◽  
Matthew Bayliss ◽  
Fuyan Bian ◽  
...  
Keyword(s):  
Rest Frame ◽  
High Redshift ◽  
Optical Emission ◽  
Emission Lines ◽  
Log P ◽  
Test Case ◽  
Single Star ◽  
Star Forming ◽  
James Webb Space Telescope ◽  
Ionization Parameter

Abstract We examine the diagnostic power of rest-frame ultraviolet (UV) nebular emission lines, and compare them to more commonly used rest-frame optical emission lines, using the test case of a single star-forming knot of the bright lensed galaxy RCSGA 032727–132609 at redshift $z$ ∼ 1.7. This galaxy has complete coverage of all the major rest-frame UV and optical emission lines from Magellan/MagE and Keck/NIRSPEC. Using the full suite of diagnostic lines, we infer the physical properties: nebular electron temperature (Te), electron density (ne), oxygen abundance (log (O/H), ionization parameter [log (q), and interstellar medium (ISM) pressure (log (P/k)]. We examine the effectiveness of the different UV, optical, and joint UV–optical spectra in constraining the physical conditions. Using UV lines alone we can reliably estimate log (q), but the same is difficult for log (O/H). UV lines yield a higher (∼1.5 dex) log (P/k) than the optical lines, as the former probes a further inner nebular region than the latter. For this comparison, we extend the existing Bayesian inference code izi, adding to it the capability to infer ISM pressure simultaneously with metallicity and ionization parameter. This work anticipates future rest-frame UV spectral data sets from the James Webb Space Telescope (JWST) at high redshift and from the Extremely Large Telescope (ELT) at moderate redshift.

scholarly journals ALMA band 8 observations of DLA 2233+131 at z = 3.150

2020 ◽  
Vol 72 (2) ◽  
Author(s):  
Kazuyuki Ogura ◽  
Hideki Umehata ◽  
Yoshiaki Taniguchi ◽  
Yuichi Matsuda ◽  
Nobunari Kashikawa ◽  
...  
Keyword(s):  
Emission Line ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Optical Images ◽  
Dusty Galaxies ◽  
Good Laboratory

Abstract We present our ALMA Band 8 observations of a damped Ly$\alpha$ absorption (DLA) system at $z = 3.150$ observed in the spectrum of the quasar Q2233+131 at $z = 3.295$. The optical counterpart of this DLA has been identified and it shows a double-peaked Ly$\alpha$ emission line. Since one possible origin of DLAs at high redshift is an outflowing gas from star-forming galaxies, DLA 2233+131 provides a good laboratory to investigate the nature of high-z DLAs. Motivated by this, we have carried out ALMA band 8 observations to study the [C ii] line in this system. However, we do not detect any significant emission line in the observed pass bands. Instead, we have serendipitously found three submm continuum sources in the observed sky area. One appears to be the quasar Q2233+131 itself while the other two sources are newly identified submm galaxies (SMGs), called SMG1 and SMG2 in this paper. They are located at a separation of ${4{^{\prime \prime }_{.}}7}$ and ${8{^{\prime \prime }_{.}}1}$ from Q2233+131, respectively. Their 646 μm fluxes are $6.35\:$mJy and $6.43\:$mJy, respectively, being higher than that of Q2233+131, $3.62\:$mJy. Since these two SMGs are not detected in the optical images obtained with the Hubble Space Telescope and the Subaru Telescope, they have a very red spectral energy distribution. It is, therefore, suggested that they are high-redshift galaxies or very dusty galaxies at intermediate redshift, although we cannot rule out the possibility that they are optically very faint SMG analogs at low redshift. Follow-up observations will be necessary to explore the nature of this interesting region.

scholarly journals Disentangling the Physical Origin of Emission Line Ratio Offsets at High Redshift with Spatially Resolved Spectroscopy

2021 ◽  
Vol 922 (1) ◽  
pp. 12
Author(s):  
Jessie Hirtenstein ◽  
Tucker Jones ◽  
Ryan L. Sanders ◽  
Crystal L. Martin ◽  
M. C. Cooper ◽  
...  
Keyword(s):  
Emission Line ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Emission Spectra ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Spatially Resolved ◽  
Resolution Element ◽  
Spatially Resolved Spectroscopy ◽  
Redshift Galaxies

Abstract We present spatially resolved Hubble Space Telescope grism spectroscopy of 15 galaxies at z ∼ 0.8 drawn from the DEEP2 survey. We analyze Hα+[N ii], [S ii], and [S iii] emission on kiloparsec scales to explore which mechanisms are powering emission lines at high redshifts, testing which processes may be responsible for the well-known offset of high-redshift galaxies from the z ∼ 0 locus in the [O iii]/Hβ versus [N ii]/Hα Baldwin—Phillips—Terlevich (BPT) excitation diagram. We study spatially resolved emission-line maps to examine evidence for active galactic nuclei (AGN), shocks, diffuse ionized gas (DIG), or escaping ionizing radiation, all of which may contribute to the BPT offsets observed in our sample. We do not find significant evidence of AGN in our sample and quantify that, on average, AGN would need to contribute ∼25% of the Hα flux in the central resolution element in order to cause the observed BPT offsets. We find weak (2σ) evidence of DIG emission at low surface brightnesses, yielding an implied total DIG emission fraction of ∼20%, which is not significant enough to be the dominant emission line driver in our sample. In general we find that the observed emission is dominated by star-forming H ii regions. We discuss trends with demographic properties and the possible role of α-enhanced abundance patterns in the emission spectra of high-redshift galaxies. Our results indicate that photoionization modeling with stellar population synthesis inputs is a valid tool to explore the specific star formation properties which may cause BPT offsets, to be explored in future work.

scholarly journals The e-MERGE Survey (e-MERLIN Galaxy Evolution Survey): overview and survey description

2020 ◽  
Vol 495 (1) ◽  
pp. 1188-1208 ◽  
Author(s):  
T W B Muxlow ◽  
A P Thomson ◽  
J F Radcliffe ◽  
N H Wrigley ◽  
R J Beswick ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Angular Resolution ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Very Large Array ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Large Program

ABSTRACT We present an overview and description of the e-MERGE Survey (e-MERLIN Galaxy Evolution Survey) Data Release 1 (DR1), a large program of high-resolution 1.5-GHz radio observations of the GOODS-N field comprising ∼140 h of observations with enhanced-Multi-Element Remotely Linked Interferometer Network (e-MERLIN) and ∼40 h with the Very Large Array (VLA). We combine the long baselines of e-MERLIN (providing high angular resolution) with the relatively closely packed antennas of the VLA (providing excellent surface brightness sensitivity) to produce a deep 1.5-GHz radio survey with the sensitivity (${\sim}1.5\, \mu$ Jy beam−1), angular resolution (0.2–0.7 arcsec) and field-of-view (∼15 × 15 arcmin2) to detect and spatially resolve star-forming galaxies and active galactic nucleus (AGN) at $z$ ≳ 1. The goal of e-MERGE is to provide new constraints on the deep, sub-arcsecond radio sky which will be surveyed by SKA1-mid. In this initial publication, we discuss our data analysis techniques, including steps taken to model in-beam source variability over an ∼20-yr baseline and the development of new point spread function/primary beam models to seamlessly merge e-MERLIN and VLA data in the uv plane. We present early science results, including measurements of the luminosities and/or linear sizes of ∼500 galaxies selected at 1.5 GHz. In combination with deep Hubble Space Telescope observations, we measure a mean radio-to-optical size ratio of re-MERGE/rHST ∼ 1.02 ± 0.03, suggesting that in most high-redshift galaxies, the ∼GHz continuum emission traces the stellar light seen in optical imaging. This is the first in a series of papers that will explore the ∼kpc-scale radio properties of star-forming galaxies and AGN in the GOODS-N field observed by e-MERGE DR1.

scholarly journals The MOSDEF survey: a comprehensive analysis of the rest-optical emission-line properties of z ∼ 2.3 star-forming galaxies

2021 ◽  
Vol 502 (2) ◽  
pp. 2600-2614
Author(s):  
Jordan N Runco ◽  
Alice E Shapley ◽  
Ryan L Sanders ◽  
Michael W Topping ◽  
Mariska Kriek ◽  
...  
Keyword(s):  
Emission Line ◽  
High Redshift ◽  
Formation Rate ◽  
Optical Emission ◽  
High Population ◽  
Star Forming ◽  
Star Forming Regions ◽  
Density Values ◽  
Optical Line ◽  
Two Populations

ABSTRACT We analyse the rest-optical emission-line spectra of z ∼ 2.3 star-forming galaxies in the complete MOSFIRE Deep Evolution Field (MOSDEF) survey. In investigating the origin of the well-known offset between the sequences of high-redshift and local galaxies in the [O iii]λ5008/Hβ versus [N ii]λ6585/Hα (‘[N ii] BPT’) diagram, we define two populations of z ∼ 2.3 MOSDEF galaxies. These include the high population that is offset towards higher [O iii]λ5008/Hβ and/or [N ii]λ6585/Hα with respect to the local SDSS sequence and the low population that overlaps the SDSS sequence. These two groups are also segregated within the [O  iii]λ5008/Hβ versus [S ii]λλ6718,6733/Hα and the [O iii]λλ4960,5008/[O ii ]λλ3727,3730 (O32) versus ([O  iii]λλ4960,5008+[O ii]λλ3727,3730)/Hβ (R23) diagrams, which suggests qualitatively that star-forming regions in the more offset galaxies are characterized by harder ionizing spectra at fixed nebular oxygen abundance. We also investigate many galaxy properties of the split sample and find that the high sample is on average smaller in size and less massive, but has higher specific star formation rate (SFR) and SFR surface density values and is slightly younger compared to the low population. From Cloudy+BPASS photoionization models, we estimate that the high population has a lower stellar metallicity (i.e. harder ionizing spectrum) but slightly higher nebular metallicity and higher ionization parameter compared to the low population. While the high population is more α-enhanced (i.e. higher α/Fe) than the low population, both samples are significantly more α-enhanced compared to local star-forming galaxies with similar rest-optical line ratios. These differences must be accounted for in all high-redshift star-forming galaxies – not only those ‘offset’ from local excitation sequences.

Spectral Modeling of Star‐forming Regions in the Ultraviolet: Stellar Metallicity Diagnostics for High‐Redshift Galaxies

2004 ◽  
Vol 615 (1) ◽  
pp. 98-117 ◽  
Author(s):  
Samantha A. Rix ◽  
Max Pettini ◽  
Claus Leitherer ◽  
Fabio Bresolin ◽  
Rolf‐Peter Kudritzki ◽  
...  
Keyword(s):  
High Redshift ◽  
Spectral Modeling ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Star Forming Regions ◽  
Redshift Galaxies
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