scholarly journals Radio Morphology of Red Geysers

2021 ◽  
Vol 922 (2) ◽  
pp. 230
Author(s):  
Namrata Roy ◽  
Emily Moravec ◽  
Kevin Bundy ◽  
Martin J. Hardcastle ◽  
Gülay Gürkan ◽  
...  
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Large Scale ◽  
Formation Rate ◽  
Small Scale ◽  
Radio Sources ◽  
Spatially Resolved ◽  
Radio Imaging ◽  
Extended Radio ◽  
Massive Halos

Abstract We present 150 MHz, 1.4 GHz, and 3 GHz radio imaging (LoTSS, FIRST, and VLASS) and spatially resolved ionized gas characteristics (SDSS IV-MaNGA) for 140 local (z < 0.1) early-type red geyser galaxies. These galaxies have a low star formation activity (with a star formation rate, SFR, ∼ 0.01 M ⊙ yr−1), but show unique extended patterns in spatially resolved emission-line maps that have been interpreted as large-scale ionized winds driven by active galactic nuclei (AGN). In this work, we confirm that red geysers host low-luminosity radio sources (L 1.4GHz ∼ 1022 WHz −1). Out of 42 radio-detected red geysers, 32 are spatially resolved in LoTSS and FIRST, with radio sizes varying between ∼5–25 kpc. Three sources have radio sizes exceeding 40 kpc. A majority display a compact radio morphology and are consistent with either low-power compact radio sources (FR0 galaxies) or radio-quiet quasars. They may be powered by small-scale AGN-driven jets that remain unresolved at the current 5″ resolution of radio data. The extended radio sources, not belonging to the “compact” morphological class, exhibit steeper spectra with a median spectral index of −0.67, indicating the dominance of lobed components. The red geysers hosting extended radio sources also have the lowest specific SFRs, suggesting they either have a greater impact on the surrounding interstellar medium or are found in more massive halos on average. The degree of alignment of the ionized wind cone and the extended radio features are either 0° or 90°, indicating possible interaction between the interstellar medium and the central radio AGN.

scholarly journals Conference summary: triggered star formation in a turbulent ISM

2006 ◽  
Vol 2 (S237) ◽  
pp. 384-389 ◽  
Author(s):  
Bruce G. Elmegreen
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Formation Rate ◽  
Small Scale ◽  
Space And Time ◽  
Gravitational Instabilities ◽  
Rate Limiting Step ◽  
Dynamical Time ◽  
Galactic Spiral ◽  
Rate Limiting

AbstractWhile the overall star formation rate in a galaxy appears to depend primarily on the gas mass and density, with the timescale for conversion of gas into stars given by the dynamical time, turbulence and explosions are still important for the process of star formation because they control the birth correlations in space and time. Most star formation appears triggered by some specific process, whether it is a galactic spiral shock, the expansion of a superbubble, the compression of a bright-rimmed globule, or some seemingly random compressive event in a supersonically turbulent flow. These processes give space and time sequences for star birth that are well observed. Many examples were given at this conference. Shocks are the link between large-scale but weak galactic processes and small-scale but strong final collapses. The rate limiting step is on the largest scale, where the dynamical time is slowest. Both gravitational instabilities and pressurized triggering seem to work on the same local dynamical time, making it difficult to tell that star formation is highly triggered when observing only galactic scales.

scholarly journals Quasi-equilibrium models of high-redshift disc galaxy evolution

2020 ◽  
Vol 500 (3) ◽  
pp. 3394-3412
Author(s):  
Steven R Furlanetto
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
High Redshift ◽  
Formation Rate ◽  
New Physics ◽  
Small Scale ◽  
Quasi Equilibrium ◽  
Mass Relation ◽  
Disc Galaxy

ABSTRACT In recent years, simple models of galaxy formation have been shown to provide reasonably good matches to available data on high-redshift luminosity functions. However, these prescriptions are primarily phenomenological, with only crude connections to the physics of galaxy evolution. Here, we introduce a set of galaxy models that are based on a simple physical framework but incorporate more sophisticated models of feedback, star formation, and other processes. We apply these models to the high-redshift regime, showing that most of the generic predictions of the simplest models remain valid. In particular, the stellar mass–halo mass relation depends almost entirely on the physics of feedback (and is thus independent of the details of small-scale star formation) and the specific star formation rate is a simple multiple of the cosmological accretion rate. We also show that, in contrast, the galaxy’s gas mass is sensitive to the physics of star formation, although the inclusion of feedback-driven star formation laws significantly changes the naive expectations. While these models are far from detailed enough to describe every aspect of galaxy formation, they inform our understanding of galaxy formation by illustrating several generic aspects of that process, and they provide a physically grounded basis for extrapolating predictions to faint galaxies and high redshifts currently out of reach of observations. If observations show violations from these simple trends, they would indicate new physics occurring inside the earliest generations of galaxies.

scholarly journals Turbulent structure and star formation in a stratified, supernova-driven, interstellar medium

2006 ◽  
Vol 2 (S237) ◽  
pp. 358-362
Author(s):  
M. K. Ryan Joung ◽  
Mordecai-Mark Mac Low
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Adaptive Mesh Refinement ◽  
Formation Rate ◽  
Three Dimensional ◽  
Adaptive Mesh ◽  
Mass Function ◽  
Initial Mass Function ◽  
Interstellar Turbulence ◽  
Self Gravity

AbstractWe report on a study of interstellar turbulence driven by both correlated and isolated supernova explosions. We use three-dimensional hydrodynamic models of a vertically stratified interstellar medium run with the adaptive mesh refinement code Flash at a maximum resolution of 2 pc, with a grid size of 0.5 × 0.5 × 10 kpc. Cold dense clouds form even in the absence of self-gravity due to the collective action of thermal instability and supersonic turbulence. Studying these clouds, we show that it can be misleading to predict physical properties such as the star formation rate or the stellar initial mass function using numerical simulations that do not include self-gravity of the gas. Even if all the gas in turbulently Jeans unstable regions in our simulation is assumed to collapse and form stars in local freefall times, the resulting total collapse rate is significantly lower than the value consistent with the input supernova rate. The amount of mass available for collapse depends on scale, suggesting a simple translation from the density PDF to the stellar IMF may be questionable. Even though the supernova-driven turbulence does produce compressed clouds, it also opposes global collapse. The net effect of supernova-driven turbulence is to inhibit star formation globally by decreasing the amount of mass unstable to gravitational collapse.

scholarly journals The MALATANG survey: dense gas and star formation from high-transition HCN and HCO+ maps of NGC 253

2020 ◽  
Vol 494 (1) ◽  
pp. 1276-1296
Author(s):  
Xue-Jian Jiang ◽  
Thomas R Greve ◽  
Yu Gao ◽  
Zhi-Yu Zhang ◽  
Qinghua Tan ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Average Density ◽  
Dense Gas ◽  
James Clerk Maxwell ◽  
Physical Conditions ◽  
Spatially Resolved ◽  
Stellar Component ◽  
Integrated Intensity ◽  
High Transition

ABSTRACT To study the high-transition dense-gas tracers and their relationships to the star formation of the inner ∼2 kpc circumnuclear region of NGC 253, we present HCN J = 4−3 and HCO+ J = 4−3 maps obtained with the James Clerk Maxwell Telescope. Using the spatially resolved data, we compute the concentration indices r90/r50 for the different tracers. HCN and HCO+ 4–3 emission features tend to be centrally concentrated, which is in contrast to the shallower distribution of CO 1–0 and the stellar component. The dense-gas fraction (fdense, traced by the velocity-integrated-intensity ratios of HCN/CO and HCO+/CO) and the ratio R31 (CO 3–2/1–0) decline towards larger galactocentric distances, but increase with higher star formation rate surface density. The radial variation and the large scatter of fdense and R31 imply distinct physical conditions in different regions of the galactic disc. The relationships of fdense versus Σstellar, and SFEdense versus Σstellar are explored. SFEdense increases with higher Σstellar in this galaxy, which is inconsistent with previous work that used HCN 1–0 data. This implies that existing stellar components might have different effects on the high-J HCN and HCO+ than their low-J emission. We also find that SFEdense seems to be decreasing with higher fdense which is consistent with previous works, and it suggests that the ability of the dense gas to form stars diminishes when the average density of the gas increases. This is expected in a scenario where only the regions with high-density contrast collapse and form stars.

scholarly journals Persistence of the colour–density relation and efficient environmental quenching to z ∼ 1.4

2019 ◽  
Vol 490 (1) ◽  
pp. 1231-1254 ◽  
Author(s):  
B C Lemaux ◽  
A R Tomczak ◽  
L M Lubin ◽  
R R Gal ◽  
L Shen ◽  
...  
Keyword(s):  
Star Formation ◽  
Time Scales ◽  
Large Scale ◽  
Formation Rate ◽  
Cosmic Time ◽  
Stellar Mass ◽  
Cluster Galaxies ◽  
Quenching Efficiency ◽  
Density Relation ◽  
Galaxy Populations

ABSTRACT Using ∼5000 spectroscopically confirmed galaxies drawn from the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey we investigate the relationship between colour and galaxy density for galaxy populations of various stellar masses in the redshift range 0.55 ≤ z ≤ 1.4. The fraction of galaxies with colours consistent with no ongoing star formation (fq) is broadly observed to increase with increasing stellar mass, increasing galaxy density, and decreasing redshift, with clear differences observed in fq between field and group/cluster galaxies at the highest redshifts studied. We use a semi-empirical model to generate a suite of mock group/cluster galaxies unaffected by environmentally specific processes and compare these galaxies at fixed stellar mass and redshift to observed populations to constrain the efficiency of environmentally driven quenching (Ψconvert). High-density environments from 0.55 ≤ z ≤ 1.4 appear capable of efficiently quenching galaxies with $\log (\mathcal {M}_{\ast }/\mathcal {M}_{\odot })\gt 10.45$. Lower stellar mass galaxies also appear efficiently quenched at the lowest redshifts studied here, but this quenching efficiency is seen to drop precipitously with increasing redshift. Quenching efficiencies, combined with simulated group/cluster accretion histories and results on the star formation rate-density relation from a companion ORELSE study, are used to constrain the average time from group/cluster accretion to quiescence and the elapsed time between accretion and the inception of the quenching event. These time-scales were constrained to be 〈tconvert〉 = 2.4 ± 0.3 and 〈tdelay〉 = 1.3 ± 0.4 Gyr, respectively, for galaxies with $\log (\mathcal {M}_{\ast }/\mathcal {M}_{\odot })\gt 10.45$ and 〈tconvert〉 = 3.3 ± 0.3 and 〈tdelay〉 = 2.2 ± 0.4 Gyr for lower stellar mass galaxies. These quenching efficiencies and associated time-scales are used to rule out certain environmental mechanisms as being the primary processes responsible for transforming the star formation properties of galaxies over this 4 Gyr window in cosmic time.

scholarly journals Chandra COSMOS Legacy Survey: Clustering dependence of Type 2 active galactic nuclei on host galaxy properties

2019 ◽  
Vol 632 ◽  
pp. A88
Author(s):  
V. Allevato ◽  
A. Viitanen ◽  
A. Finoguenov ◽  
F. Civano ◽  
H. Suh ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Large Scale ◽  
Formation Rate ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
Host Galaxy ◽  
X Ray ◽  
Normal Galaxies ◽  
Massive Halos

Aims. We perform clustering measurements of 800 X-ray selected Chandra COSMOS Legacy (CCL) Type 2 active galactic nuclei (AGN) with known spectroscopic redshift to probe the halo mass dependence on AGN host galaxy properties, such as galaxy stellar mass Mstar, star formation rate (SFR), and specific black hole accretion rate (BHAR; λBHAR) in the redshift range z = [0−3]. Methods. We split the sample of AGN with known spectroscopic redshits according to Mstar, SFR and λBHAR, while matching the distributions in terms of the other parameters, including redshift. We measured the projected two-point correlation function wp(rp) and modeled the clustering signal, for the different subsamples, with the two-halo term to derive the large-scale bias b and corresponding typical mass of the hosting halo. Results. We find no significant dependence of the large-scale bias and typical halo mass on galaxy stellar mass and specific BHAR for CCL Type 2 AGN at mean z ∼ 1, while a negative dependence on SFR is observed, i.e. lower SFR AGN reside in richer environment. Mock catalogs of AGN, matched to have the same X-ray luminosity, stellar mass, λBHAR, and SFR of CCL Type 2 AGN, almost reproduce the observed Mstar − Mh, λBHAR − Mh and SFR–Mh relations, when assuming a fraction of satellite AGN fAGNsat ∼ 0.15. This corresponds to a ratio of the probabilities of satellite to central AGN of being active Q ∼ 2. Mock matched normal galaxies follow a slightly steeper Mstar − Mh relation, in which low mass mock galaxies reside in less massive halos than mock AGN of similar mass. Moreover, matched mock normal galaxies are less biased than mock AGN with similar specific BHAR and SFR, at least for Q >  1.

scholarly journals Interstellar Scintillation of Radio Sources as a Probe for Investigations of the Local Interstellar Medium

1997 ◽  
Vol 166 ◽  
pp. 215-218
Author(s):  
N. Bochkarev ◽  
M. Ryabov
Keyword(s):  
Interstellar Medium ◽  
Small Scale ◽  
Radio Sources ◽  
Local Interstellar Medium ◽  
Star Formation Region ◽  
X Ray ◽  
Extragalactic Radio Sources ◽  
Hot Gas ◽  
The North ◽  
Scintillation Indices

AbstractA possibility of obtaining information on small scale inhomogeneities of the electron component of the local interstellar medium (LISM) is investigated using interstellar scintillations of extragalactic radio sources. We analyse Culgoora array observational data on variability of 190 extragalactic radio sources, covering most of the sky, at 80 and 160 MHz. The variability at time scales from 1 month to 15 years is interpreted as refractive interstellar scintillations in fast-moving nearby (less than 150 pc) hot gas near shock waves in the LISM. All-sky map of scintillation indices m averaged over 3–5 sources closest to one another shows several m maxima. Two of the 3 most pronounced maxima are probably connected with Loop I; the third one coincides with the soft X-ray (0.1–0.3 keV) background maximum near the South Galactic Pole. Other, less certain, m maxima probably correspond to the Orion star-formation region and to a soft X-ray maximum near the North Galactic Pole. The ”free-of-gas” tunnel in the direction l = 240° corresponds to low values of m. The estimated time scale of interstellar scintillations on the above-mentioned LISM structures is in agreement with that of the observed radio-source variations.

scholarly journals SDSS-IV MaNGA: effects of morphology in the global and local star formation main sequences

2019 ◽  
Vol 488 (3) ◽  
pp. 3929-3948 ◽  
Author(s):  
M Cano-Díaz ◽  
V Ávila-Reese ◽  
S F Sánchez ◽  
H M Hernández-Toledo ◽  
A Rodríguez-Puebla ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Density ◽  
Main Sequence ◽  
Formation Rate ◽  
Stellar Mass ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Formation Activity ◽  
Global And Local ◽  
Universal Mechanism

ABSTRACT We study the global star formation rate (SFR) versus stellar mass (M*) correlation, and the spatially resolved SFR surface density (ΣSFR) versus stellar mass surface density (Σ*) correlation, in a sample of ∼2000 galaxies from the MaNGA MPL-5 survey. We classify galaxies and spatially resolved areas into star forming and retired according to their ionization processes. We confirm the existence of a star-forming main sequence (SFMS) for galaxies and spatially resolved areas, and show that they have the same nature, with the global as a consequence of the local one. The latter presents a bend below a limit Σ* value, ≈3 × 107 M$\odot$ kpc−2, which is not physical. Using only star-forming areas (SFAs) above this limit, a slope and a scatter of ≈1 and ≈0.27 dex are determined. The retired galaxies/areas strongly segregate from their respective SFMSs, by ∼−1.5 dex on average. We explore how the global/local SFMSs depend on galaxy morphology, finding that for star-forming galaxies and SFAs, there is a trend to lower values of star formation activity with earlier morphological types, which is more pronounced for the local SFMS. The morphology not only affects the global SFR due to the diminish of SFAs with earlier types, but also affects the local SF process. Our results suggest that the local SF at all radii is established by some universal mechanism partially modulated by morphology. Morphology seems to be connected to the slow aging and sharp decline of the SF process, and on its own it may depend on other properties as the environment.

scholarly journals Large Scale Jets in Class I and Class II Radio Sources and Quasars

1989 ◽  
Vol 8 ◽  
pp. 409-416
Author(s):  
G.V. Bicknell
Keyword(s):  
Interstellar Medium ◽  
Surface Brightness ◽  
Large Scale ◽  
External Medium ◽  
Class Ii ◽  
Class I ◽  
Radio Sources ◽  
Speed Of Light ◽  
Slow Surface ◽  
Quasar Jets

ABSTRACTThe physics of large scale jets in class I and class II extragalactic radio sources and quasars is discussed. Class I jets appear to be turbulent, transonic jets which entrain the interstellar medium. The related jet deceleration causes a slow surface brightness decline which is usually observed. Class II jets are supersonic and terminate in an advancing shock against the external medium. Both types of jet are initially light but the ratio of jet density to external density of class I jets increases owing to entrainment. It is quite plausible that quasar jets are hypersonic and light and this may solve problems of confinement. The velocities of class I jets are of the order of a few thousand kilometers per second. Class II and quasar jets may be at least mildly relativistic. However, it is not clear whether the velocities of large scale jets in powerful sources are close to the speed of light. Recent depolarization measurements provide an interesting focus for discussion of this question.

scholarly journals Simulations of the star-forming molecular gas in an interacting M51-like galaxy

2020 ◽  
Vol 492 (2) ◽  
pp. 2973-2995 ◽  
Author(s):  
Robin G Tress ◽  
Rowan J Smith ◽  
Mattia C Sormani ◽  
Simon C O Glover ◽  
Ralf S Klessen ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Formation Rate ◽  
Three Dimensional ◽  
Molecular Gas ◽  
Secondary Importance ◽  
Star Forming ◽  
The Galaxy ◽  
Cold Star ◽  
Self Gravity

ABSTRACT We present here the first of a series of papers aimed at better understanding the evolution and properties of giant molecular clouds (GMCs) in a galactic context. We perform high-resolution, three-dimensional arepo simulations of an interacting galaxy inspired by the well-observed M51 galaxy. Our fiducial simulations include a non-equilibrium, time-dependent, chemical network that follows the evolution of atomic and molecular hydrogen as well as carbon and oxygen self-consistently. Our calculations also treat gas self-gravity and subsequent star formation (described by sink particles), and coupled supernova feedback. In the densest parts of the simulated interstellar medium (ISM), we reach sub-parsec resolution, granting us the ability to resolve individual GMCs and their formation and destruction self-consistently throughout the galaxy. In this initial work, we focus on the general properties of the ISM with a particular focus on the cold star-forming gas. We discuss the role of the interaction with the companion galaxy in generating cold molecular gas and controlling stellar birth. We find that while the interaction drives large-scale gas flows and induces spiral arms in the galaxy, it is of secondary importance in determining gas fractions in the different ISM phases and the overall star formation rate. The behaviour of the gas on small GMC scales instead is mostly controlled by the self-regulating property of the ISM driven by coupled feedback.

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