scholarly journals Gas accretion as fuel for residual star formation in Galaxy Zoo elliptical galaxies

2019 ◽  
Vol 489 (1) ◽  
pp. L108-L113 ◽  
Author(s):  
Timothy A Davis ◽  
Lisa M Young
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
External Source ◽  
Elliptical Galaxies ◽  
Sloan Digital Sky Survey ◽  
Star Forming ◽  
Sky Survey ◽  
Low Metallicity ◽  
Minor Mergers ◽  
Gas Accretion

ABSTRACT In this letter we construct a large sample of early-type galaxies (ETGs) with measured gas-phase metallicities from the Sloan Digital Sky Survey and Galaxy Zoo in order to investigate the origin of the gas that fuels their residual star formation. We use this sample to show that star-forming elliptical galaxies have a substantially different gas-phase metallicity distribution from spiral galaxies, with ≈7.4 per cent having a very low gas-phase metallicity for their mass. These systems typically have fewer metals in the gas phase than they do in their stellar photospheres, which strongly suggests that the material fuelling their recent star formation was accreted from an external source. We use a chemical evolution model to show that the enrichment time-scale for low-metallicity gas is very short, and thus that cosmological accretion and minor mergers are likely to supply the gas in ≳ 37 per cent of star-forming ETGs, in good agreement with estimates derived from other independent techniques.

scholarly journals Galaxy pairs in the Sloan Digital Sky Survey – XIV. Galaxy mergers do not lie on the fundamental metallicity relation

2020 ◽  
Vol 494 (3) ◽  
pp. 3469-3480 ◽  
Author(s):  
Sebastián Bustamante ◽  
Sara L Ellison ◽  
David R Patton ◽  
Martin Sparre
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Formation Rate ◽  
Local Environment ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Galaxy Mergers ◽  
Star Forming ◽  
Sky Survey ◽  
Evolutionary Phase

ABSTRACT In recent observational studies, star-forming galaxies have been shown to follow a relation often dubbed the fundamental metallicity relation (FMR). This relation links the stellar mass of a galaxy with its star formation rate (SFR) and its gas-phase metallicity. Specifically, the FMR predicts that galaxies, at a given stellar mass, exhibit lower metallicities for higher SFRs. This trend is qualitatively consistent with observations of galaxy pairs, which have been robustly shown to experience increasing gas-phase metallicity dilution and enhanced star formation activity with decreasing projected separation. In this work, we show that, despite the qualitative consistency with FMR expectations, the observed O/H dilution in galaxy pairs of the Sloan Digital Sky Survey is stronger than what is predicted by the FMR. We conclude that the evolutionary phase of galaxies interacting with companions is not encoded in the FMR, and thus, mergers constitute a clearly defined population of outliers. We find that galaxies in pairs are consistent with the FMR only when their separation is larger than 110 kpc. Finally, we also quantify the local environment of the pairs using the number of galaxy neighbours within 2 Mpc, N2, and the projected separation to the second closest galaxy, r2. We find that pairs are more sensitive to a second companion than to the local galaxy density, displaying less elevated SFRs with smaller values of r2.

scholarly journals Mg II λ2797, λ2803 emission in a large sample of low-metallicity star-forming galaxies from SDSS DR14

2019 ◽  
Vol 624 ◽  
pp. A21 ◽  
Author(s):  
N. G. Guseva ◽  
Y. I. Izotov ◽  
K. J. Fricke ◽  
C. Henkel
Keyword(s):  
Noble Gas ◽  
Formation Rate ◽  
Sloan Digital Sky Survey ◽  
Large Sample ◽  
Star Forming ◽  
Magnesium Depletion ◽  
Sky Survey ◽  
Solar Metallicity ◽  
Low Metallicity ◽  
Damped Lyman Alpha Systems

A large sample of Mg II emitting star-forming galaxies with low metallicity [O/H] = log(O/H) – log(O/H)⊙ between –0.2 and –1.2 dex is constructed from Data Release 14 of the Sloan Digital Sky Survey. We selected 4189 galaxies with Mg II λ2797, λ2803 emission lines in the redshift range z ∼ 0.3–1.0 or 35% of the total Sloan Digital Sky Survey star-forming sample with redshift z ≥ 0.3. We study the dependence of the magnesium-to-oxygen and magnesium-to-neon abundance ratios on metallicity. Extrapolating this dependence to [Mg/Ne] = 0 and to solar metallicity we derive a magnesium depletion of [Mg/Ne] ≃ –0.4 (at solar metallicity). We prefer neon instead of oxygen to evaluate the magnesium depletion in the interstellar medium because neon is a noble gas and is not incorporated into dust, contrary to oxygen. Thus, we find that more massive and more metal abundant galaxies have higher magnesium depletion. The global parameters of our sample, such as the mass of the stellar population and star formation rate, are compared with previously obtained results from the literature. These results confirm that Mg II emission has a nebular origin. Our data for interstellar magnesium-to-oxygen abundance ratios relative to the solar value are in good agreement with similar measurements made for Galactic stars, for giant stars in the Milky Way satellite dwarf galaxies, and with low-metallicity damped Lyman-alpha systems.

scholarly journals Redshift measurement through star formation

2019 ◽  
Vol 629 ◽  
pp. A7
Author(s):  
Mikkel O. Lindholmer ◽  
Kevin A. Pimbblet
Keyword(s):  
Star Formation ◽  
Galaxy Clusters ◽  
Main Sequence ◽  
Formation Rate ◽  
Sloan Digital Sky Survey ◽  
X Ray ◽  
Star Forming ◽  
Sky Survey ◽  
The Galaxy ◽  
Galaxy Population

In this work we use the property that, on average, star formation rate increases with redshift for objects with the same mass – the so called galaxy main sequence – to measure the redshift of galaxy clusters. We use the fact that the general galaxy population forms both a quenched and a star-forming sequence, and we locate these ridges in the SFR–M⋆ plane with galaxies taken from the Sloan Digital Sky Survey in discrete redshift bins. We fitted the evolution of the galaxy main sequence with redshift using a new method and then subsequently apply our method to a suite of X-ray selected galaxy clusters in an attempt to create a new distance measurement to clusters based on their galaxy main sequence. We demonstrate that although it is possible in several galaxy clusters to measure the main sequences, the derived distance and redshift from our galaxy main sequence fitting technique has an accuracy of σz = ±0.017 ⋅ (z + 1) and is only accurate up to z ≈ 0.2.

scholarly journals What is Important? Morphological Asymmetries are Useful Predictors of Star Formation Rates of Star-forming Galaxies in SDSS Stripe 82

2021 ◽  
Vol 923 (2) ◽  
pp. 205
Author(s):  
Hassen M. Yesuf ◽  
Luis C. Ho ◽  
S. M. Faber
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Sloan Digital Sky Survey ◽  
Imaging Data ◽  
Galaxy Interactions ◽  
Star Forming ◽  
Sky Survey ◽  
Structural Variables ◽  
Central Concentration

Abstract The morphology and structure of galaxies reflect their star formation and assembly histories. We use the framework of mutual information (MI) to quantify the interdependence among several structural variables and to rank them according to their relevance for predicting the specific star formation rate (SSFR) by comparing the MI of the predictor variables with the SSFR and penalizing variables that are redundant. We apply this framework to study ∼3700 face-on star-forming galaxies (SFGs) with varying degrees of bulge dominance and central concentration and with stellar mass M ⋆ ≈ 109 M ⊙−5 × 1011 M ⊙ at redshift z = 0.02–0.12. We use the Sloan Digital Sky Survey (SDSS) Stripe 82 deep i-band imaging data, which improve measurements of asymmetry and bulge dominance indicators. We find that star-forming galaxies are a multiparameter family. In addition to M ⋆, asymmetry emerges as the most powerful predictor of SSFR residuals of SFGs, followed by bulge prominence/concentration. Star-forming galaxies with higher asymmetry and stronger bulges have higher SSFR at a given M ⋆. The asymmetry reflects both irregular spiral arms and lopsidedness in seemingly isolated SFGs and structural perturbations by galaxy interactions or mergers.

scholarly journals Properties and redshift evolution of star-forming galaxies with high [O III]/[O II] ratios with MUSE at 0.28 < z < 0.85

2018 ◽  
Vol 618 ◽  
pp. A40 ◽  
Author(s):  
M. Paalvast ◽  
A. Verhamme ◽  
L. A. Straka ◽  
J. Brinchmann ◽  
E. C. Herenz ◽  
...  
Keyword(s):  
Formation Rate ◽  
Incidence Rates ◽  
Sloan Digital Sky Survey ◽  
Star Forming ◽  
Sky Survey ◽  
Combining Data ◽  
Low Metallicity ◽  
The Relationship ◽  
Bright Emission ◽  
Similar Incidence

We present a study of the [O III]/[O II] ratios of star-forming galaxies drawn from Multi-Unit Spectroscopic Explorer (MUSE) data spanning a redshift range 0.28 < z < 0.85. Recently discovered Lyman continuum (LyC) emitters have extremely high oxygen line ratios: [O III]λ5007/[O II]λλ3726, 3729 > 4. Here we aim to understand the properties and the occurrences of galaxies with such high line ratios. Combining data from several MUSE Guaranteed Time Observing (GTO) programmes, we select a population of star-forming galaxies with bright emission lines, from which we draw 406 galaxies for our analysis based on their position in the z-dependent star formation rate (SFR)–stellar mass (M∗) plane. Out of this sample 15 are identified as extreme oxygen emitters based on their [O III]/[O II] ratios (3.7%) and 104 galaxies have [O III]/[O II] > 1 (26%). Our analysis shows no significant correlation between M∗, SFR, and the distance from the SFR−M∗ relation with [O III]/[O II]. We find a decrease in the fraction of galaxies with [O III]/[O II] > 1 with increasing M∗, however, this is most likely a result of the relationship between [O III]/[O II] and metallicity, rather than between [O III]/[O II] and M∗. We draw a comparison sample of local analogues with ⟨z⟩ ≈ 0.03 from the Sloan Digital Sky Survey, and find similar incidence rates for this sample. In order to investigate the evolution in the fraction of high [O III]/[O II] emitters with redshift, we bin the sample into three redshift subsamples of equal number, but find no evidence for a dependence on redshift. Furthermore, we compare the observed line ratios with those predicted by nebular models with no LyC escape and find that most of the extreme oxygen emitters can be reproduced by low metallicity models. The remaining galaxies are likely LyC emitter candidates.

scholarly journals Actively Star-forming Elliptical Galaxies at Low Redshifts in the Sloan Digital Sky Survey

2004 ◽  
Vol 601 (2) ◽  
pp. L127-L130 ◽  
Author(s):  
Masataka Fukugita ◽  
Osamu Nakamura ◽  
Edwin L. Turner ◽  
Joe Helmboldt ◽  
R. C. Nichol
Keyword(s):  
Elliptical Galaxies ◽  
Sloan Digital Sky Survey ◽  
Star Forming ◽  
Sky Survey

scholarly journals Comparison of Composite and Star-forming Early-type Galaxies

2021 ◽  
Vol 163 (1) ◽  
pp. 28
Author(s):  
Yu-Zhong Wu
Keyword(s):  
Star Formation ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Early Type ◽  
Massive Galaxies ◽  
Star Forming ◽  
Sky Survey ◽  
Excitation Mechanisms ◽  
Stellar Masses ◽  
Evolution Scheme

Abstract I assemble 4684 star-forming early-type galaxies (ETGs) and 2011 composite ETGs (located in the composite region on the BPT diagram) from the catalog of the Sloan Digital Sky Survey Data Release 7 MPA-JHU emission-line measurements. I compare the properties of both ETG samples and investigate their compositions, stellar masses, specific star formation rates (sSFRs), and excitation mechanisms. Compared with star-forming ETGs, composite ETGs have higher stellar mass and lower sSFR. In the stellar mass and u − r color diagram, more than 60% of star-forming ETGs and composite ETGs are located in the green valley, showing that the two ETG samples may have experienced star formation and that ∼17% of star-forming ETGs lie in the blue cloud, while ∼30% of composite ETGs lie in the red sequence. In the [N II]/Hα versus EWHα (the Hα equivalent width) diagram, all star-forming ETGs and most of the composite ETGs are located in the star-forming galaxy region, and composite ETGs have lower EWHα than their counterparts. We show the relations between 12+log(O/H) and log(N/O) for both ETG samples, and suggest that nitrogen production of some star-forming ETGs can be explained by the evolution scheme of Coziol et al., while the prodution of composite ETGs may be a consequence of the inflowing of metal-poor gas and these more evolved massive galaxies.

scholarly journals Galactic conformity in both star formation and morphological properties

2020 ◽  
Vol 492 (2) ◽  
pp. 2722-2730 ◽  
Author(s):  
Justin A Otter ◽  
Karen L Masters ◽  
Brooke Simmons ◽  
Chris J Lintott
Keyword(s):  
Star Formation ◽  
Relative Size ◽  
Mass Range ◽  
Sloan Digital Sky Survey ◽  
Morphological Properties ◽  
Star Forming ◽  
Sky Survey ◽  
Group Environment ◽  
Group Memberships ◽  
Morphology Changes

ABSTRACT We investigate one-halo galactic conformity (the tendency for satellite galaxies to mirror the properties of their central) in both star formation and morphology using a sample of 8230 galaxies in 1266 groups with photometry and spectroscopy from the Sloan Digital Sky Survey, morphologies from Galaxy Zoo and group memberships as determined by Yang et al. This is the first paper to investigate galactic conformity in both star formation and visual morphology properties separately. We find that the signal of galactic conformity is present at low significance in both star formation and visual morphological properties, however it is stronger in star formation properties. Over the entire halo mass range we find that groups with star-forming (spiral) centrals have, on average, a fraction 0.18 ± 0.08 (0.08 ± 0.06) more star-forming (spiral) satellites than groups with passive (early-type) centrals at a similar halo mass. We also consider conformity in groups with four types of central: passive early-types, star-forming spirals, passive spirals, and star-forming early-types (which are very rarely centrals), finding that the signal of morphological conformity is strongest around passive centrals regardless of morphology; although blue spiral centrals are also more likely than average to have blue spiral satellites. We interpret these observations of the relative size of the conformity signal as supporting a scenario where star formation properties are relatively easily changed, while morphology changes less often/more slowly for galaxies in the group environment.

scholarly journals Low-redshift lowest-metallicity star-forming galaxies in the SDSS DR14

2019 ◽  
Vol 623 ◽  
pp. A40 ◽  
Author(s):  
Y. I. Izotov ◽  
N. G. Guseva ◽  
K. J. Fricke ◽  
C. Henkel
Keyword(s):  
Accurate Determination ◽  
Sloan Digital Sky Survey ◽  
Emission Lines ◽  
Strong Line ◽  
Star Forming ◽  
Line Method ◽  
Sky Survey ◽  
Low Metallicity ◽  
Semi Empirical

We present a sample of low-redshift (z <  0.133) candidates for extremely low-metallicity star-forming galaxies with oxygen abundances 12 + log O/H <  7.4 selected from the Data Release 14 (DR14) of the Sloan Digital Sky Survey (SDSS). Three methods are used to derive their oxygen abundances. Among these methods two are based on strong [O II]λ3727 Å, [O III]λ4959 Å, and [O III]λ5007 Å emission lines, which we call strong-line and semi-empirical methods. These were applied for all galaxies. We have developed one of these methods, the strong-line method, in this paper. This method is specifically focused on the accurate determination of metallicity in extremely low-metallicity galaxies and may not be used at higher metallicities with 12 + log O/H ≳ 7.5. The third, the direct Te method, was applied for galaxies with detected [O III]λ4363 emission lines. All three methods give consistent abundances and can be used in combination or separately for selection of lowest-metallicity candidates. However, the strong-line method is preferable for spectra with a poorly detected or undetected [O III]λ4363 emission line. In total, our list of selected candidates for extremely low-metallicity galaxies includes 66 objects.

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