scholarly journals Interacting galaxies in the IllustrisTNG simulations - I: Triggered star formation in a cosmological context

2020 ◽  
Vol 494 (4) ◽  
pp. 4969-4985 ◽  
Author(s):  
David R Patton ◽  
Kieran D Wilson ◽  
Colin J Metrow ◽  
Sara L Ellison ◽  
Paul Torrey ◽  
...  
Keyword(s):  
Star Formation ◽  
Local Density ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Massive Galaxies ◽  
Star Forming ◽  
Cosmological Context ◽  
Sky Survey ◽  
The Mean ◽  
Hydrodynamical Simulations

ABSTRACT We use the IllustrisTNG cosmological hydrodynamical simulations to investigate how the specific star formation rates (sSFRs) of massive galaxies (M* > 1010 M⊙) depend on the distance to their closest companions. We estimate sSFR enhancements by comparing with control samples that are matched in redshift, stellar mass, local density, and isolation, and we restrict our analysis to pairs with stellar mass ratios of 0.1 to 10. At small separations (∼15 kpc), the mean sSFR is enhanced by a factor of 2.0 ± 0.1 in the flagship (110.7 Mpc)3 simulation (TNG100-1). Statistically significant enhancements extend out to 3D separations of 280 kpc in the (302.6 Mpc)3 simulation (TNG300-1). We find similar trends in the EAGLE and Illustris simulations, although their sSFR enhancements are lower than those in TNG100-1 by about a factor of two. Enhancements in IllustrisTNG galaxies are seen throughout the redshift range explored (0 ≤ $z$ < 1), with the strength of the enhancements decreasing with increasing redshift for galaxies with close companions. In order to more closely compare with observational results, we separately consider 2D projected distances between galaxies in IllustrisTNG. We detect significant sSFR enhancements out to projected separations of 260 kpc in TNG300-1, with projection effects diluting the size of the enhancements by about 20 per cent below 50 kpc. We find similar sSFR enhancements in TNG100-1 and Sloan Digital Sky Survey galaxies, with enhancements extending out to projected separations of about 150 kpc for star-forming galaxies at $z$ < 0.2. Finally, by summing over all separations, we estimate that the presence of closest companions boosts the average sSFR of massive galaxies in TNG100-1 by 14.5 per cent.

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 Exploring galaxy colour in different environments of the cosmic web with SDSS

2020 ◽  
Vol 498 (4) ◽  
pp. 6069-6082
Author(s):  
Biswajit Pandey ◽  
Suman Sarkar
Keyword(s):  
Local Density ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Local Dimension ◽  
Sky Survey ◽  
The Galaxy ◽  
Colour Distribution ◽  
The Mean ◽  
Red Galaxies

ABSTRACT We analyse a set of volume-limited samples from the Sloan Digital Sky Survey (SDSS) to study the dependence of galaxy colour on different environments of the cosmic web. We measure the local dimension of galaxies to determine the geometry of their embedding environments and find that filaments host a higher fraction of red galaxies than sheets at each luminosity. We repeat the analysis at a fixed density and recover the same trend, which shows that galaxy colours depend on geometry of environments besides local density. At a fixed luminosity, the fraction of red galaxies in filaments and sheets increases with the extent of these environments. This suggests that the bigger structures have a larger baryon reservoir favouring higher accretion and larger stellar mass. We find that the mean colour of the red and blue populations are systematically higher in the environments with smaller local dimension and increases monotonically in all the environments with luminosity. We observe that the bimodal nature of the galaxy colour distribution persists in all environments and all luminosities, which suggests that the transformation from blue to red galaxy can occur in all environments.

scholarly journals The impact of the connectivity of the cosmic web on the physical properties of galaxies at its nodes

2019 ◽  
Vol 491 (3) ◽  
pp. 4294-4309 ◽  
Author(s):  
Katarina Kraljic ◽  
Christophe Pichon ◽  
Sandrine Codis ◽  
Clotilde Laigle ◽  
Romeel Davé ◽  
...  
Keyword(s):  
Physical Properties ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Massive Galaxies ◽  
Star Forming ◽  
Star Formation Activity ◽  
Theoretical Predictions ◽  
Hydrodynamical Simulations ◽  
Minor Mergers ◽  
The Impact

ABSTRACT We investigate the impact of the number of filaments connected to the nodes of the cosmic web on the physical properties of their galaxies using the Sloan Digital Sky Survey. We compare these measurements to the cosmological hydrodynamical simulations H orizon-(no)AGN and Simba. We find that more massive galaxies are more connected, in qualitative agreement with theoretical predictions and measurements in dark-matter-only simulations. The star formation activity and morphology of observed galaxies both display some dependence on the connectivity of the cosmic web at a fixed stellar mass: Less star forming and less rotation supported galaxies also tend to have higher connectivity. These results qualitatively hold both for observed and for virtual galaxies, and can be understood given that the cosmic web is the main source of fuel for galaxy growth. The simulations show the same trends at a fixed halo mass, suggesting that the geometry of filamentary infall impacts galaxy properties beyond the depth of the local potential well. Based on simulations, it is also found that active galactic nucleus feedback is key to reversing the relationship between stellar mass and connectivity at a fixed halo mass. Technically, connectivity is a practical observational proxy for past and present accretion (minor mergers or diffuse infall).

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 Evaluating hydrodynamical simulations with green valley galaxies

2020 ◽  
Author(s):  
J Angthopo ◽  
A Negri ◽  
I Ferreras ◽  
I G de la Rosa ◽  
C Dalla Vecchia ◽  
...  
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Galaxy Formation ◽  
Seed Mass ◽  
Bimodal Distribution ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
M 10 ◽  
Sky Survey ◽  
Hydrodynamical Simulations

Abstract We test cosmological hydrodynamical simulations of galaxy formation regarding the properties of the Blue Cloud (BC), Green Valley (GV) and Red Sequence (RS), as measured on the 4000Å break strength vs stellar mass plane at z = 0.1. We analyse the RefL0100N1504 run of EAGLE and the TNG100 run of IllustrisTNG project, by comparing them with the Sloan Digital Sky Survey, while taking into account selection bias. Our analysis focuses on the GV, within stellar mass log  M⋆/M⊙ ≃ 10 − 11, selected from the bimodal distribution of galaxies on the Dn(4000) vs stellar mass plane, following Angthopo et al. methodology. Both simulations match the fraction of AGN in the green-valley. However, they over-produce quiescent GV galaxies with respect to observations, with IllustrisTNG yielding a higher fraction of quiescent GV galaxies than EAGLE. In both, GV galaxies have older luminosity-weighted ages with respect to the SDSS, while a better match is found for mass-weighted ages. We find EAGLE GV galaxies quench their star formation early, but undergo later episodes of star formation, matching observations. In contrast, IllustrisTNG GV galaxies have a more extended SFH, and quench more effectively at later cosmic times, producing the excess of quenched galaxies in GV compared with SDSS, based on the 4000Å break strength. These results suggest the AGN feedback subgrid physics, more specifically, the threshold halo mass for black hole input and the black hole seed mass, could be the primary cause of the over-production of quiescent galaxies found with respect to the observational constraints.

scholarly journals The weak imprint of environment on the stellar populations of galaxies

2020 ◽  
Vol 500 (4) ◽  
pp. 4469-4490 ◽  
Author(s):  
James Trussler ◽  
Roberto Maiolino ◽  
Claudia Maraston ◽  
Yingjie Peng ◽  
Daniel Thomas ◽  
...  
Keyword(s):  
Environmental Effects ◽  
Unique Feature ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Star Forming ◽  
Sky Survey ◽  
Satellite Galaxies ◽  
Projected Distance ◽  
Environmental Dependence

ABSTRACT We investigate the environmental dependence of the stellar populations of galaxies in Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Echoing earlier works, we find that satellites are both more metal-rich (<0.1 dex) and older (<2 Gyr) than centrals of the same stellar mass. However, after separating star-forming, green valley, and passive galaxies, we find that the true environmental dependence of both stellar metallicity (<0.03 dex) and age (<0.5 Gyr) is in fact much weaker. We show that the strong environmental effects found when galaxies are not differentiated result from a combination of selection effects brought about by the environmental dependence of the quenched fraction of galaxies, and thus we strongly advocate for the separation of star-forming, green valley, and passive galaxies when the environmental dependence of galaxy properties are investigated. We also study further environmental trends separately for both central and satellite galaxies. We find that star-forming galaxies show no environmental effects, neither for centrals nor for satellites. In contrast, the stellar metallicities of passive and green valley satellites increase weakly (<0.05 and <0.08 dex, respectively) with increasing halo mass, increasing local overdensity and decreasing projected distance from their central; this effect is interpreted in terms of moderate environmental starvation (‘strangulation’) contributing to the quenching of satellite galaxies. Finally, we find a unique feature in the stellar mass–stellar metallicity relation for passive centrals, where galaxies in more massive haloes have larger stellar mass (∼0.1 dex) at constant stellar metallicity; this effect is interpreted in terms of dry merging of passive central galaxies and/or progenitor bias.

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 Stellar populations in star forming galaxies in the Sloan Digital Sky Survey

2009 ◽  
Vol 5 (S262) ◽  
pp. 446-447
Author(s):  
Pieter Westera ◽  
François Cuisinier ◽  
Carlos R. Rabaça
Keyword(s):  
Population Analysis ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
High Mass ◽  
Synthesis Methods ◽  
Young Generation ◽  
Homogeneous Sample ◽  
Star Forming ◽  
Sky Survey

AbstractWe examine the star forming phenomenon as it can be encountered in galaxies in the Sloan Digital Sky Survey, which possibly contains the largest homogeneous sample of star forming galaxy spectra to date.After eliminating all spectra with an insufficient signal-to-noise ratio, without strong emission lines, and without the [OII] λ3727 Å line, which is necessary for the determination of the gas metallicity (which excludes galaxies with redshift ≲ 0.024–0.025), our sample contains ~6000 spectra of star forming galaxies.Through a detailed stellar population analysis employing evolutionary synthesis methods we determined the stellar composition of these galaxies, that is, the masses, ages and metallicities of their partial stellar populations.We find that most, possibly all, galaxies of our sample contain, apart from the presently bursting, ionising young generation (≤ 107 yrs), old (≥ 109 yrs) and intermediate (between 107 and 109 yrs) populations, whereas the old population dominates the stellar mass (but not the light).We also find that high (stellar) mass galaxies have higher gas metallicities and lower present star formation rates relative to their total (stellar) masses, than low mass galaxies, indicating a higher chemical evolution degree for high mass galaxies.Furthermore, we find that gas enrichment mechanisms in star forming galaxies do not vary with galactic mass, being the same for low- and high-mass galaxies on average. Gas enrichment mechanisms seem to present a greater variety at the high-mass end, though, indicating a more complex assembly history for high-mass galaxies.

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