scholarly journals A Multiwavelength Study of ELAN Environments (AMUSE2). Detection of a Dusty Star-forming Galaxy within the Enormous Lyα Nebula at z=2.3 Sheds Light on its Origin

2021 ◽  
Vol 923 (2) ◽  
pp. 200
Author(s):  
Chian-Chou Chen ◽  
Fabrizio Arrigoni Battaia ◽  
Bjorn H. C. Emonts ◽  
Matthew D. Lehnert ◽  
J. Xavier Prochaska
Keyword(s):  
Environmental Effects ◽  
Gas Reservoir ◽  
Velocity Difference ◽  
Star Forming ◽  
Systemic Velocity ◽  
Projected Length ◽  
Ram Pressure ◽  
Cool Gas ◽  
Single Emission ◽  
Projected Distance

Abstract We present ALMA observations on and around the radio-quiet quasar UM 287 at z = 2.28. Together with a companion quasar, UM 287 is believed to play a major role in powering the surrounding enormous Lyα nebula (ELAN), dubbed the Slug ELAN, that has an end-to-end size of 450 physical kpc. In addition to the quasars, we detect a new dusty star-forming galaxy (DSFG), dubbed the Slug-DSFG, in 2 mm continuum with a single emission line consistent with CO(4−3). The Slug-DSFG sits at a projected distance of 100 kpc southeast from UM 287, with a systemic velocity difference of −360 ± 30 km s−1 with respect to UM 287, suggesting it is a possible contributor to the powering of the Slug ELAN. With careful modeling of the SED and dynamical analyses, it is found that the Slug-DSFG and UM 287 appear low in both gas fraction and gas-to-dust ratio, suggesting environmental effects due to the host’s massive halo. In addition, our Keck long-slit spectra reveal significant Lyα emissions from the Slug-DSFG, as well as a Lyα tail that starts at the location and velocity of the Slug-DSFG and extends toward the south, with a projected length of about 100 kpc. Supported by various analytical estimates we propose that the Lyα tail is a result of the Slug-DSFG experiencing ram pressure stripping. The gas mass stripped is estimated to be about 109 M ⊙, contributing to the dense warm/cool gas reservoir that is believed to help power the exceptional Lyα luminosity.

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 Evidence for ram-pressure stripping in a cluster of galaxies at z = 0.7

2019 ◽  
Vol 631 ◽  
pp. A114 ◽  
Author(s):  
A. Boselli ◽  
B. Epinat ◽  
T. Contini ◽  
V. Abril-Melgarejo ◽  
L. A. Boogaard ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Massive Star ◽  
Observational Evidence ◽  
Star Forming ◽  
Cluster Of Galaxies ◽  
Stellar Component ◽  
Ram Pressure ◽  
The Galaxy ◽  
The Universe ◽  
Projected Distance

Multi-Unit Spectroscopic Explorer (MUSE) observations of the cluster of galaxies CGr32 (M200 ≃ 2 × 1014 M⊙) at z = 0.73 reveal the presence of two massive star-forming galaxies with extended tails of diffuse gas detected in the [O II]λλ3727–3729 Å emission-line doublet. The tails, which have a cometary shape with a typical surface brightness of a few 10−18 erg s−1 cm−2 arcsec−2, extend up to ≃100 kpc (projected distance) from the galaxy discs, and are not associated with any stellar component. All this observational evidence suggests that the gas was removed during a ram-pressure stripping event. This observation is thus the first evidence that dynamical interactions with the intracluster medium were active when the Universe was only half its present age. The density of the gas derived using the observed [O II]λ3729/[O II]λ3726 line ratio implies a very short recombination time, suggesting that a source of ionisation is necessary to keep the gas ionised within the tail.

scholarly journals Cluster induced quenching of galaxies in the massive cluster XMMXCS J2215.9−1738 at z ∼ 1.5 traced by enhanced metallicities inside half R200

2019 ◽  
Vol 626 ◽  
pp. A14 ◽  
Author(s):  
C. Maier ◽  
M. Hayashi ◽  
B. L. Ziegler ◽  
T. Kodama
Keyword(s):  
Cluster Center ◽  
Velocity Versus ◽  
Intracluster Medium ◽  
Gas Reservoir ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Ram Pressure ◽  
The Individual ◽  
Halo Gas ◽  
Massive Cluster

Aims. Cluster environments at z <  0.5 were found to increase the gas metallicities of galaxies which enter inner regions of the clusters where the density of the intracluster medium is high enough to remove their hot halo gas by ram-pressure stripping effects and to stop the inflow of pristine gas. To extend these studies to z >  1, the most massive clusters known at these redshifts are the sites where these environmental effects should be more pronounced and more easily observed with present day telescopes. Methods. We explore the massive cluster XMMXCS J2215.9−1738 at z ∼ 1.5 with KMOS spectroscopy of Hα and [N II] λ 6584 covering a region that corresponds to about one virial radius. Using published spectroscopic redshifts of 108 galaxies in and around the cluster we computed the location of galaxies in the projected velocity-versus-position phase-space to separate our cluster sample into a virialized region of objects accreted longer ago (roughly inside half R200) and a region of infalling galaxies. We measured oxygen abundances for ten cluster galaxies with detected [N II] λ 6584 lines in the individual galaxy spectra and compared the mass–metallicity relation of the galaxies inside half R200 with the infalling galaxies and a field sample at similar redshifts. Results. We find that the oxygen abundances of individual z ∼ 1.5 star-forming cluster galaxies inside half R200 are comparable, at the respective stellar mass, to the higher local SDSS metallicity values. We compare our measurements with a field galaxy sample from the KMOS3D survey at similar redshifts. We find that the [N II] λ 6584/Hα line ratios inside half R200 are higher by 0.2 dex and that the resultant metallicities of the galaxies in the inner part of the cluster are higher by about 0.1 dex, at a given mass, than the metallicities of infalling galaxies and of field galaxies at z ∼ 1.5. The enhanced metallicities of cluster galaxies at z ∼ 1.5 inside 0.5R200 indicate that the density of the intracluster medium in this massive cluster becomes high enough toward the cluster center such that the ram pressure exceeds the restoring pressure of the hot gas reservoir of cluster galaxies. This can remove the gas reservoir and initiate quenching; although the galaxies continue to form stars, albeit at slightly lower rates, using the available cold gas in the disk which is not stripped.

scholarly journals Tidal Dwarf Galaxies

1998 ◽  
Vol 11 (1) ◽  
pp. 141-144
Author(s):  
P.-A. Duc ◽  
I.F. Mirabel ◽  
E. Brinks
Keyword(s):  
Environmental Effects ◽  
Intergalactic Medium ◽  
Dwarf Galaxies ◽  
Star Forming ◽  
Evolution Of Galaxies ◽  
New Generation

The life and evolution of galaxies are dramatically affected by environmental effects. Interactions with the intergalactic medium and collisions with companions cause major perturbations in the morphology and contents of galaxies: in particular stars and gas clouds may be gravitationally pulled out from their parent galaxies during tidal encounters, forming rings, tails and bridges. This debris of collisions lies at the origin of a new generation of small galaxies, the so-called “tidal dwarf galaxies” (hereafter TDGs). Such an exotic way of forming galaxies was put forward by Schweizer (1978) and by Mirabel et al. (1992), who clearly observed the genesis of a star-forming object, out of material tidally expelled from the interacting system NGC 4038/39 (“The Antennae”). Recent studies, based on optical and HI observations, have shown that TDGs actually form a class of “recycled” objects with some properties similar to the more classical dwarf irregulars (dIrr) and blue compact dwarf galaxies (BCDs).

scholarly journals Morphometry as a probe of the evolution of jellyfish galaxies: evidence of broadening in the surface brightness profiles of ram-pressure stripping candidates in the multicluster system A901/A902

2020 ◽  
Vol 500 (1) ◽  
pp. 40-53
Author(s):  
Fernanda Roman-Oliveira ◽  
Ana L Chies-Santos ◽  
Fabricio Ferrari ◽  
Geferson Lucatelli ◽  
Bruno Rodríguez Del Pino
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Quantitative Measurement ◽  
Star Formation Rate ◽  
Hubble Space Telescope ◽  
Formation Rate ◽  
Structural Evolution ◽  
Star Forming ◽  
Irregular Structures ◽  
Ram Pressure

ABSTRACT We explore the morphometric properties of a group of 73 ram-pressure stripping candidates in the A901/A902 multicluster system, at z∼ 0.165, to characterize the morphologies and structural evolution of jellyfish galaxies. By employing a quantitative measurement of morphometric indicators with the algorithm morfometryka on Hubble Space Telescope (F606W) images of the galaxies, we present a novel morphology-based method for determining trail vectors. We study the surface brightness profiles and curvature of the candidates and compare the results obtained with two analysis packages, morfometryka and iraf/ellipse on retrieving information of the irregular structures present in the galaxies. Our morphometric analysis shows that the ram-pressure stripping candidates have peculiar concave regions in their surface brightness profiles. Therefore, these profiles are less concentrated (lower Sérsic indices) than other star-forming galaxies that do not show morphological features of ram-pressure stripping. In combination with morphometric trail vectors, this feature could both help identify galaxies undergoing ram-pressure stripping and reveal spatial variations in the star formation rate.

scholarly journals Most of the cool CGM of star-forming galaxies is not produced by supernova feedback

2020 ◽  
Author(s):  
Andrea Afruni ◽  
Filippo Fraternali ◽  
Gabriele Pezzulli
Keyword(s):  
Galaxy Evolution ◽  
Cosmic Time ◽  
Energy Coupling ◽  
High Energy ◽  
Parametric Models ◽  
Star Forming ◽  
Galaxy Halos ◽  
The Galaxy ◽  
Supernova Explosions ◽  
Cool Gas

Abstract The characterization of the large amount of gas residing in the galaxy halos, the so called circumgalactic medium (CGM), is crucial to understand galaxy evolution across cosmic time. We focus here on the the cool (T ∼ 104 K) phase of this medium around star-forming galaxies in the local universe, whose properties and dynamics are poorly understood. We developed semi-analytical parametric models to describe the cool CGM as an outflow of gas clouds from the central galaxy, as a result of supernova explosions in the disc (galactic wind). The cloud motion is driven by the galaxy gravitational pull and by the interactions with the hot (T ∼ 106 K) coronal gas. Through a bayesian analysis, we compare the predictions of our models with the data of the COS-Halos and COS-GASS surveys, which provide accurate kinematic information of the cool CGM around more than 40 low-redshift star-forming galaxies, probing distances up to the galaxy virial radii. Our findings clearly show that a supernova-driven outflow model is not suitable to describe the dynamics of the cool circumgalactic gas. Indeed, to reproduce the data, we need extreme scenarios, with initial outflow velocities and mass loading factors that would lead to unphysically high energy coupling from the supernovae to the gas and with supernova efficiencies largely exceeding unity. This strongly suggests that, since the outflows cannot reproduce most of the cool gas absorbers, the latter are likely the result of cosmological inflow in the outer galaxy halos, in analogy to what we have previously found for early-type galaxies.

scholarly journals A complete census of circumgalactic Mg ii at redshift z ≲ 0.5

2021 ◽  
Vol 502 (4) ◽  
pp. 4743-4761 ◽  
Author(s):  
Yun-Hsin Huang ◽  
Hsiao-Wen Chen ◽  
Stephen A Shectman ◽  
Sean D Johnson ◽  
Fakhri S Zahedy ◽  
...  
Keyword(s):  
Rest Frame ◽  
Formation Rate ◽  
Host Galaxies ◽  
Clear Trend ◽  
Stellar Objects ◽  
Star Forming ◽  
Multiple Parameters ◽  
Isolated Galaxies ◽  
Cool Gas ◽  
Gas Accretion

ABSTRACT This paper presents a survey of Mg ii absorbing gas in the vicinity of 380 random galaxies, using 156 background quasi-stellar objects (QSOs) as absorption-line probes. The sample comprises 211 isolated (73 quiescent and 138 star-forming galaxies) and 43 non-isolated galaxies with sensitive constraints for both Mg ii absorption and H α emission. The projected distances span a range from d = 9 to 497 kpc, redshifts of the galaxies range from z = 0.10 to 0.48, and rest-frame absolute B-band magnitudes range from MB = −16.7 to −22.8. Our analysis shows that the rest-frame equivalent width of Mg ii, Wr(2796), depends on halo radius (Rh), B-band luminosity(LB), and stellar mass (Mstar) of the host galaxies, and declines steeply with increasing d for isolated, star-forming galaxies. At the same time, Wr(2796) exhibits no clear trend for either isolated, quiescent galaxies or non-isolated galaxies. In addition, the covering fraction of Mg ii absorbing gas 〈κ〉 is high with 〈κ〉 ≳ 60 per cent at &lt;40 kpc for isolated galaxies and declines rapidly to 〈κ〉 ≈ 0 at d ≳ 100 kpc. Within the gaseous radius, the incidence of Mg ii gas depends sensitively on both Mstar and the specific star formation rate inferred from H α. Different from what is known for massive quiescent haloes, the observed velocity dispersion of Mg ii absorbing gas around star-forming galaxies is consistent with expectations from virial motion, which constrains individual clump mass to $m_{\rm cl} \gtrsim 10^5 \, \rm M_\odot$ and cool gas accretion rate of $\sim 0.7\!-\!2 \, \mathrm{ M}_\odot \, \rm yr^{-1}$. Finally, we find no strong azimuthal dependence of Mg ii absorption for either star-forming or quiescent galaxies. Our results demonstrate that multiple parameters affect the properties of gaseous haloes around galaxies and highlight the need of a homogeneous, absorption-blind sample for establishing a holistic description of chemically enriched gas in the circumgalactic space.

scholarly journals Anatomy of the massive star-forming region S106

2018 ◽  
Vol 617 ◽  
pp. A45 ◽  
Author(s):  
N. Schneider ◽  
M. Röllig ◽  
R. Simon ◽  
H. Wiesemeyer ◽  
A. Gusdorf ◽  
...  
Keyword(s):  
Binary System ◽  
High Velocity ◽  
Central Area ◽  
Line Emission ◽  
Two Phase ◽  
Star Forming ◽  
Projected Length ◽  
Molecular Lines ◽  
Dark Lane ◽  
Gas Accretion

The central area (40″  × 40″) of the bipolar nebula S106 was mapped in the [O I] line at 63.2 μm (4.74 THz) with high angular (6″) and spectral (0.24 MHz) resolution, using the GREAT heterodyne receiver on board SOFIA. The spatial and spectral emission distribution of [O I] is compared to emission in the CO 16 →15, [C II] 158 μm, and CO 11 →10 lines, mm-molecular lines, and continuum. The [O I] emission is composed of several velocity components in the range from –30 to 25 km s−1. The high-velocity blue- and red-shifted emission (v = −30 to –9 km s−1 and 8 to 25 km s−1) can be explained as arising from accelerated photodissociated gas associated with a dark lane close to the massive binary system S106 IR, and from shocks caused by the stellar wind and/or a disk–envelope interaction. At velocities from –9 to –4 km s−1 and from 0.5 to 8 km s−1 line wings are observed in most of the lines that we attribute to cooling in photodissociation regions (PDRs) created by the ionizing radiation impinging on the cavity walls. The velocity range from –4 to 0.5 km s−1 is dominated by emission from the clumpy molecular cloud, and the [O I], [C II], and high-J CO lines are excited in PDRs on clump surfaces that are illuminated by the central stars. Modelling the line emission in the different velocity ranges with the KOSMA-τ code constrains a radiation field χ of a few times 104 and densities n of a few times 104 cm−3. Considering self-absorption of the [O I] line results in higher densities (up to 106 cm−3) only for the gas component seen at high blue- and red velocities. We thus confirm the scenario found in other studies that the emission of these lines can be explained by a two-phase PDR, but attribute the high-density gas to the high-velocity component only. The dark lane has a mass of ~275 M⊙ and shows a velocity difference of ~1.4 km s−1 along its projected length of ~1 pc, determined from H13CO+ 1 →0 mapping. Its nature depends on the geometry and can be interpreted as a massive accretion flow (infall rate of ~2.5 × 10−4 M⊙ yr−1), or the remains of it, linked to S106 IR/FIR. The most likely explanation is that the binary system is at a stage of its evolution where gas accretion is counteracted by the stellar winds and radiation, leading to the very complex observed spatial and kinematic emission distribution of the various tracers.

scholarly journals Young stars raining through the galactic halo: the nature and orbit of price-whelan 1

2019 ◽  
Vol 490 (2) ◽  
pp. 2588-2598 ◽  
Author(s):  
Michele Bellazzini ◽  
Rodrigo A Ibata ◽  
Nicolas Martin ◽  
Khyati Malhan ◽  
Antonino Marasco ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Stellar System ◽  
Young Stars ◽  
Stellar Content ◽  
Velocity Difference ◽  
Ram Pressure ◽  
Magellanic Stream ◽  
Gas Cloud ◽  
Velocity Cloud ◽  
High Velocity Cloud

ABSTRACT We present radial velocities for five member stars of the recently discovered young (age ≃ 100−150 Myr) stellar system Price-Whelan 1 (PW 1), which is located far away in the Galactic Halo (D≃ 29 kpc, Z≃ 15 kpc), and that is probably associated with the leading arm (LA) of the Magellanic Stream. We measure the systemic radial velocity of PW 1, Vr = 275 ± 10 km s−1, significantly larger than the velocity of the LA gas in the same direction. We re-discuss the main properties and the origin of this system in the light of these new observations, computing the orbit of the system and comparing its velocity with that of the H i in its surroundings. We show that the bulk of the gas at the velocity of the stars is more than 10 deg (5 kpc) away from PW 1 and the velocity difference between the gas and the stars becomes larger as gas closer to the stars is considered. We discuss the possibilities that (1) the parent gas cloud was dissolved by the interaction with the Galactic gas, and (2) that the parent cloud is the high-velocity cloud (HVC) 287.5+22.5 + 240, lagging behind the stellar system by ≃ 25 km s−1 and ≃10 deg ≃ 5 kpc. This HVC, which is part of the LA, has metallicity similar to PW 1, displays a strong magnetic field that should help to stabilize the cloud against ram pressure, and shows traces of molecular hydrogen. We also show that the system is constituted of three distinct pieces that do not differ only by position in the sky but also by stellar content.

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