scholarly journals Intermediate Resolution Spectroscopy of the Radio Galaxy B2 0902+34 at Z ≈ 3.4

1996 ◽  
Vol 168 ◽  
pp. 499-500
Author(s):  
J. L. Sanz ◽  
J. M. Martín-Mirones ◽  
E. Martínez-González ◽  
J. I. González-Serrano
Keyword(s):  
Galaxy Evolution ◽  
Spectral Range ◽  
Spectral Resolution ◽  
Radio Galaxy ◽  
High Redshift ◽  
Neutral Hydrogen ◽  
Radio Continuum ◽  
Continuum Source ◽  
The Galaxy ◽  
William Herschel

We have carried out optical spectroscopic observations at intermediate spectral resolution of the massive high redshift radio galaxy 0902+34 atz≈ 3.39. This source was first identified by Lilly (1988) (from hereafter L88). The study of high redshift radio galaxies is interesting to analyze the physical conditions of the early universe and the galaxy evolution at cosmological redshifts. It has been claimed that some of these systems may be protogalaxies in the process of formation. Indications for this are the flat spectrum and the absence of the 4000 Å break, features which have already been observed in many cases. In particular, observations in the spectral range fromVtoKsuggest that 0902+34 is a young galaxy (Eisenhardt and Dickinson 1992). Recent radio observations of the 21 cm line of neutral hydrogen have detected (Uson et al. 1991) an absorption against the radio continuum source. This absorption could also leave a track in the optical, redwards the Lyα line. Our observations were carried out with the ISIS spectrograph at the 4.2 m William Herschel Telescope (seeing ≈ 1.2–1.6 arcsec). A spectral dispersion of 0.78 Å/pixel (blue arm) and 1.38 Å/pixel (red arm) was obtained. Å long slit of width 3′ was used providing a spectral resolution of ≈ 5.4 Å in the blue arm and of ≈ 9.5 Å in the red one. Both resolutions are a clear improvement over that achieved by L88 of 20 Å, allowing us to resolve the Lyα line (and its possible structure) and any other possible strong features appearing in the spectral range observed (e. g., C iv λ1549, He ii λ1640, …). Six different observations of 2700 s of the radio galaxy 0902+34 were carried out. The slit was rotated to coincide with the parallactic angle at the beginning of each exposure. This will allow us to map spectroscopically different regions of the galaxy (for more details see Martín-Mirones et al. 1994).

scholarly journals Quasar Sightline and Galaxy Evolution (QSAGE) survey – I. The galaxy environment of O vi absorbers up to z = 1.4 around PKS 0232−04

2019 ◽  
Vol 486 (1) ◽  
pp. 21-41 ◽  
Author(s):  
R M Bielby ◽  
J P Stott ◽  
F Cullen ◽  
T M Tripp ◽  
J N Burchett ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Near Infrared ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Star Forming ◽  
The Galaxy ◽  
Circumgalactic Medium ◽  
Galaxy Environment ◽  
Using Data ◽  
Galaxy Population

ABSTRACT We present the first results from a study of O vi absorption around galaxies at z < 1.44 using data from a near-infrared grism spectroscopic Hubble Space Telescope Large Programme, the Quasar Sightline and Galaxy Evolution (QSAGE) survey. QSAGE is the first grism galaxy survey to focus on the circumgalactic medium at z ∼ 1, providing a blind survey of the galaxy population. The galaxy sample is H α flux limited (f(H α) > 2 × 10−17 erg s−1 cm−2) at 0.68 < z < 1.44, corresponding to ≳0.2–0.8 M⊙ yr−1. In this first of 12 fields, we combine the galaxy data with high-resolution STIS and COS spectroscopy of the background quasar to study O vi in the circumgalactic medium. At z ∼ 1, we find O vi absorption systems up to b ∼ 350 kpc (∼4Rvir) from the nearest detected galaxy. Further, we find ${\sim }50{{\ \rm per\ cent}}$ of ≳1 M⊙ yr−1 star-forming galaxies within 2Rvir show no associated O vi absorption to a limit of at least N(O vi) = 1013.9 cm−2. That we detect O vi at such large distances from galaxies and that a significant fraction of star-forming galaxies show no detectable O vi absorption disfavours outflows from ongoing star formation as the primary medium traced by these absorbers. Instead, by combining our own low- and high-redshift data with existing samples, we find tentative evidence for many strong (N(O vi) > 1014 cm−2) O vi absorption systems to be associated with M⋆ ∼ 109.5–10 M⊙ mass galaxies (Mhalo ∼ 1011.5–12 M⊙ dark matter haloes), and infer that they may be tracing predominantly collisionally ionized gas within the haloes of such galaxies.

scholarly journals Shedding light on high-redshift galaxies with the 21cm signal

2019 ◽  
Vol 15 (S352) ◽  
pp. 69-69
Author(s):  
Anne Hutter
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
Neutral Hydrogen ◽  
First Stars ◽  
High Redshift Galaxies ◽  
Redshift Galaxy ◽  
First Galaxies ◽  
Galaxy Population ◽  
The Impact ◽  
Redshift Galaxies

AbstractReionization represents an important epoch in the history in the Universe, when the first stars and galaxies gradually ionize the neutral hydrogen in the intergalactic medium (IGM). Understanding the nature of the ionizing sources, the associated ionization of the IGM, and its impact on subsequent structure formation and galaxy evolution by means of radiative feedback effects, represent key outstanding questions in current astrophysics. High-redshift galaxy observations and simulations have significantly extended our knowledge on the nature of high-redshift galaxies. However, essential properties such as the escape fraction of ionizing photons from galaxies into the IGM and their dependency on galactic properties remain essentially unknown, but determine significantly the distribution and time evolution of the ionized regions during reionization. Analyzing this ionization topology by means of the neutral hydrogen sensitive 21cm signal with radio interferometers such as SKA offers a complementary and unique opportunity to determine the nature of these first galaxies. I will show results from a self-consistent semi-numerical model of galaxy evolution and reionization, and discuss the potential of inferring galactic properties with the 21cm signal as well as the impact of reionization on the high-redshift galaxy population and its evolution.

scholarly journals A Distant HII Region In The Galaxy

1965 ◽  
Vol 18 (1) ◽  
pp. 91 ◽  
Author(s):  
K Akabane ◽  
FJ Kerr
Keyword(s):  
Radial Velocity ◽  
Neutral Hydrogen ◽  
Line Of Sight ◽  
Radio Sources ◽  
Velocity Range ◽  
Hii Region ◽  
Continuum Source ◽  
Absorption Studies ◽  
The Galaxy

It has long been realized that 21 cm absorption studies can provide information about the distance of unidentified radio sources. When the radiation from a continuum source is absorbed by neutral hydrogen clouds in the foreground, an observation of the radial velocity range over which the absorption occurs indicates the position of the source in relation to the various hydrogen features along the line of sight. Whenever absorption effects can be seen, we can immediately tell whether the source concerned is galactic or extragalactic; if it is galactic, we can then place limits on its distance.

scholarly journals The cosmic epoch dependence of environmental effects on size evolution of red-sequence early-type galaxies

2018 ◽  
Vol 617 ◽  
pp. A53 ◽  
Author(s):  
S. Andreon
Keyword(s):  
Growth Rate ◽  
Galaxy Evolution ◽  
High Redshift ◽  
Early Period ◽  
Early Type ◽  
General Field ◽  
The Galaxy ◽  
Size Growth ◽  
Massive Halos ◽  
Red Sequence

This work aims to observationally investigate the history of size growth of early-type galaxies and how the growth depends on cosmic epoch and the mass of the halo in which they are embedded. We carried out a photometric and structural analysis in the rest-frameVband of a mass-selected (logM/M⊙> 10.7) sample of red-sequence early-type galaxies with spectroscopic/grism redshift in the general field up toz= 2 to complement a previous work presenting an identical analysis but in halos 100 times more massive and 1000 times denser. We homogeneously derived sizes (effective radii) fully accounting for the multi-component nature of galaxies and the common presence of isophote twists and ellipticity gradients. By using these mass-selected samples, composed of 170 red-sequence early-type galaxies in the general field and 224 identically selected and analyzed in clusters, we isolate the effect on galaxy sizes of the halo in which galaxies are embedded and its dependence on epoch. We find that the log of the galaxy size at a fixed stellar mass, logM/M⊙= 11, has increased with epoch at a rate twice as fast in the field than in cluster in the last 10 Gyr (0.26 ± 0.03 versus 0.13 ± 0.02 dex per unit redshift). Red-sequence early-type galaxies in the general field reached the size of their cousins in denser environment byz= 0.25 ± 0.13 in spite of being three times smaller atz∼ 2. Data point toward a model where size growth is epoch-independent (i.e., ∂ logre/∂z=c), but with a ratecdepending on environment, ∂c/∂ logMhalo≈ 0.05. Environment determines the growth rate (d logre/dz) at all redshifts, indicating an external origin for the galaxy growth without any clear epoch where it ceases to have an effect. The larger size of early-type galaxies in massive halos at high redshift indicates that their size grew buildup earlier (atz> 2) at an accelerated rate, slowing down at some still unidentifiedz> 2 redshift. Instead, the size growth rate of red-sequence early-type galaxies in low-mass halos is reversed: it proceeds at an increased rate at late epochs after an early period (z> 2) of reduced growth, in agreement with the qualitative hierarchical picture of galaxy evolution. We found similar values of scatter around the mass-size relation independently of environment and epoch, indicating that the amount of dissipation in the system forming the observed galaxy does not vary greatly with epoch or environment.

scholarly journals GASP XXV: neutral hydrogen gas in the striking jellyfish galaxy JO204

2020 ◽  
Vol 494 (4) ◽  
pp. 5029-5043 ◽  
Author(s):  
Tirna Deb ◽  
Marc A W Verheijen ◽  
Marco Gullieuszik ◽  
Bianca M Poggianti ◽  
Jacqueline H van Gorkom ◽  
...  
Keyword(s):  
Neutral Hydrogen ◽  
Turbulent Medium ◽  
Hydrogen Gas ◽  
Radio Continuum ◽  
Absorption Profile ◽  
Ionized Gas ◽  
Absorption Column ◽  
Continuum Source ◽  
Neutral Gas ◽  
Ram Pressure

ABSTRACT We present JVLA-C observations of the H i gas in JO204, one of the most striking jellyfish galaxies from the GASP survey. JO204 is a massive galaxy in the low-mass cluster A957 at z = 0.04243. The H i map reveals an extended 90 kpc long ram-pressure stripped tail of neutral gas, stretching beyond the 30 kpc long ionized gas tail and pointing away from the cluster centre. The H i mass seen in emission is $(1.32\pm 0.13) \times 10^{9} \, \rm M_{\odot }$, mostly located in the tail. The northern part of the galaxy disc has retained some H i gas, while the southern part has already been completely stripped and displaced into an extended unilateral tail. Comparing the distribution and kinematics of the neutral and ionized gas in the tail indicates a highly turbulent medium. Moreover, we observe associated H i absorption against the 11 mJy central radio continuum source with an estimated H i absorption column density of 3.2 × 1020 cm−2. The absorption profile is significantly asymmetric with a wing towards higher velocities. We modelled the H i absorption by assuming that the H i and ionized gas discs have the same kinematics in front of the central continuum source, and deduced a wider absorption profile than observed. The observed asymmetric absorption profile can therefore be explained by a clumpy, rotating H i gas disc seen partially in front of the central continuum source, or by ram pressure pushing the neutral gas towards the centre of the continuum source, triggering the AGN activity.

scholarly journals OH Megamasers and Active Galactic Nuclei

1988 ◽  
Vol 129 ◽  
pp. 261-262
Author(s):  
R.P. Norris
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Disk ◽  
Galactic Nuclei ◽  
Far Infrared ◽  
Active Galaxies ◽  
Radio Continuum ◽  
Substantial Fraction ◽  
Continuum Source ◽  
Maser Amplifier ◽  
The Galaxy

OH megamasers are believed to be active galaxies in which a substantial fraction of the OH gas in the disk of the galaxy is stimulated by the intense far-infrared flux from the active nucleus. The result is that the galactic disk acts as a maser amplifier, producing in the OH line an amplified image of the radio continuum source in the nucleus. Megamasers promise to be powerful tools for the study of active galaxies, provided we can determine what it is that turns an active galaxy into a megamaser. Here I examine the archetypal megamaser galaxy Arp220 and ask the question: what makes it different from other active galaxies?

scholarly journals Galaxy Preprocessing in a Starbrusting Group Infalling into Abell1367

2006 ◽  
Vol 2 (S235) ◽  
pp. 197-197
Author(s):  
L. Cortese ◽  
G. Gavazzi ◽  
A. Boselli ◽  
P. Franzetti ◽  
R. C. Kennicutt ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
High Speed ◽  
Ambient Medium ◽  
High Redshift ◽  
Cluster Assembly ◽  
Ionized Gas ◽  
Tidal Forces ◽  
Star Formation Activity ◽  
The Galaxy ◽  
Group Members

AbstractWe present a multiwavelength analysis of a compact group infalling at high speed (~1700 km s−1) into the dynamically young cluster Abell 1367. Peculiar morphologies and unusually high Halpha emission are associated with two giant galaxies and at least ten dwarfs/extragalactic HII regions, making this group the region with the highest density of star formation activity ever observed in the local clusters. Moreover Halpha imaging observations reveal extraordinary complex trails of ionized gas behind the galaxies, with projected lengths exceeding 100 kpc. These unique cometary trails mark the gaseous trajectory of galaxies, witnessing their dive into the hot cluster intergalactic medium. Under the combined action of tidal forces among group members and the ram-pressure by the cluster ambient medium, the group galaxies were fragmented and the ionized gas was blown out. The properties of this group suggest that environmental effects within infalling groups may have represented a preprocessing step of the galaxy evolution during the high redshift cluster assembly phase.

scholarly journals The elephant in the bathtub: when the physics of star formation regulate the baryon cycle of galaxies

2020 ◽  
Vol 500 (2) ◽  
pp. 2000-2011
Author(s):  
Jindra Gensior ◽  
J M Diederik Kruijssen
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
High Redshift ◽  
Formation Rate ◽  
Cosmic Time ◽  
Free Fall ◽  
Isolated Galaxies ◽  
The Galaxy ◽  
Galaxy Masses

ABSTRACT In simple models of galaxy formation and evolution, star formation is solely regulated by the amount of gas present in the galaxy. However, it has recently been shown that star formation can be suppressed by galactic dynamics in galaxies that contain a dominant spheroidal component and a low gas fraction. This ‘dynamical suppression’ is hypothesized to also contribute to quenching gas-rich galaxies at high redshift, but its impact on the galaxy population at large remains unclear. In this paper, we assess the importance of dynamical suppression in the context of gas regulator models of galaxy evolution through hydrodynamic simulations of isolated galaxies, with gas-to-stellar mass ratios of 0.01–0.20 and a range of galactic gravitational potentials from disc-dominated to spheroidal. Star formation is modelled using a dynamics-dependent efficiency per free-fall time, which depends on the virial parameter of the gas. We find that dynamical suppression becomes more effective at lower gas fractions and quantify its impact on the star formation rate as a function of gas fraction and stellar spheroid mass surface density. We combine the results of our simulations with observed scaling relations that describe the change of galaxy properties across cosmic time, and determine the galaxy mass and redshift range where dynamical suppression may affect the baryon cycle. We predict that the physics of star formation can limit and regulate the baryon cycle at low redshifts (z ≲ 1.4) and high galaxy masses (M* ≳ 3 × 1010 M⊙), where dynamical suppression can drive galaxies off the star formation main sequence.

Galactic dynamics and DM profile of NGC1380 with ALMA and VLT/MUSE

2019 ◽  
Vol 14 (S353) ◽  
pp. 248-252
Author(s):  
Takafumi Tsukui ◽  
Satoru Iguchi ◽  
Kyoko Onishi
Keyword(s):  
Dark Matter ◽  
Galaxy Evolution ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
Large Field ◽  
Molecular Gas ◽  
Early Type ◽  
Stellar Kinematics ◽  
Gas Kinematics ◽  
The Galaxy

AbstractIn order to understand the interaction between dark matter and baryonic matter in the galaxy evolution history, it is fundamental to constrain dark matter (DM) distribution in galaxies. However, it is difficult to constrain DM profile in the central region of early type galaxy because of the lack of extended neutral hydrogen gas and the degeneracy between dynamical stellar M/L and DM profile. To resolve this difficulty, we conducted combined analysis of ALMA cold molecular gas kinematics and MUSE stellar kinematics of early type fast rotator galaxy NGC1380. In addition, we used HST image to trace the stellar luminosity distribution. With the help of high resolution of ALMA image and large field of view of MUSE, we derived the central BH mass, stellar bulge, disk and DM profile.

scholarly journals Self-consistent modelling of aromatic dust species and extinction curves in galaxy evolution

2020 ◽  
Vol 492 (3) ◽  
pp. 3779-3793 ◽  
Author(s):  
Hiroyuki Hirashita ◽  
Maria S Murga
Keyword(s):  
Galaxy Evolution ◽  
Milky Way ◽  
High Redshift ◽  
Extinction Curve ◽  
Aromatic Carbon ◽  
The Galaxy ◽  
Consistent Manner ◽  
Polycyclic Aromatic ◽  
Nearby Galaxies ◽  
Far Ultraviolet

ABSTRACT We formulate and calculate the evolution of dust in a galaxy focusing on the distinction among various dust components – silicate, aromatic carbon, and non-aromatic carbon. We treat the galaxy as a one-zone object and adopt the evolution model of grain size distribution developed in our previous work. We further include aromatization and aliphatization (inverse reaction of aromatization). We regard small aromatic grains in a radius range of 3–50 Å as polycyclic aromatic hydrocarbons (PAHs). We also calculate extinction curves in a consistent manner with the abundances of silicate and aromatic and non-aromatic carbonaceous dust. Our model nicely explains the PAH abundance as a function of metallicity in nearby galaxies. The extinction curve becomes similar to the Milky Way curve at an age of ∼10 Gyr, in terms of the carbon bump strength and the far-ultraviolet slope. We also apply our model to starburst galaxies by shortening the star formation time-scale (0.5 Gyr) and increasing the dense-gas fraction (0.9), finding that the extinction curve maintains bumpless shapes (because of low aromatic fractions), which are similar to the extinction curves observed in the Small Magellanic Cloud and high-redshift quasars. Thus, our model successfully explains the variety in extinction curve shapes at low and high redshifts.

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