scholarly journals The nucleus of IC 342 as a potential twin of the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 66-68
Author(s):  
David S. Meier
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Galactic Center ◽  
Formation Rate ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Star Forming ◽  
Optical Continuum ◽  
Nuclear Cluster ◽  
Circumnuclear Disk

AbstractThe Galactic center (GC), being the closest nucleus, holds a position of privilege in the study of galaxy centers, but because it is edge-on and hidden behind 30 magnitudes of visual extinction it is often difficult to understand the overall structure of the region. Nearby galactic nuclei potentially provide a guide to understanding the large-scale structure of the GC. High resolution maps of molecular line emission along with radio and optical continuum towards the nucleus of the nearby, face-on spiral IC 342 are discussed. Attention is focused on a comparison of the large-scale morphology, gas chemistry, and star formation between the two nuclei. The case is made that IC 342 is one of the best extragalactic templates for the GC. Both have a star formation rate within a factor of two of each other and an ISM morphology characterized by a R 300 pc central molecular zone formed from a pair of arms laced with a collection of dense star forming molecular clouds. IC 342 also exhibits a nuclear cluster and associated circumnuclear disk. Whether the nuclear morphology and chemistry in IC 342 is an extension of the disk bar, a separate nuclear bar, or results from radiative/mechanical feedback remains unsettled.

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.

scholarly journals The EDGE-CALIFA survey: exploring the role of molecular gas on galaxy star formation quenching

2020 ◽  
Vol 644 ◽  
pp. A97
Author(s):  
D. Colombo ◽  
S. F. Sanchez ◽  
A. D. Bolatto ◽  
V. Kalinova ◽  
A. Weiß ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Large Scale ◽  
Formation Rate ◽  
Molecular Gas ◽  
Star Forming ◽  
Average Value ◽  
First Results ◽  
Gas Consumption ◽  
Formation Efficiency

Understanding how galaxies cease to form stars represents an outstanding challenge for galaxy evolution theories. This process of “star formation quenching” has been related to various causes, including active galactic nuclei activity, the influence of large-scale dynamics, and the environment in which galaxies live. In this paper, we present the first results from a follow-up of CALIFA survey galaxies with observations of molecular gas obtained with the APEX telescope. Together with the EDGE-CARMA observations, we collected 12CO observations that cover approximately one effective radius in 472 CALIFA galaxies. We observe that the deficit of galaxy star formation with respect to the star formation main sequence (SFMS) increases with the absence of molecular gas and with a reduced efficiency of conversion of molecular gas into stars, which is in line with the results of other integrated studies. However, by dividing the sample into galaxies dominated by star formation and galaxies quenched in their centres (as indicated by the average value of the Hα equivalent width), we find that this deficit increases sharply once a certain level of gas consumption is reached, indicating that different mechanisms drive separation from the SFMS in star-forming and quenched galaxies. Our results indicate that differences in the amount of molecular gas at a fixed stellar mass are the primary drivers for the dispersion in the SFMS, and the most likely explanation for the start of star formation quenching. However, once a galaxy is quenched, changes in star formation efficiency drive how much a retired galaxy differs in its star formation rate from star-forming ones of similar masses. In other words, once a paucity of molecular gas has significantly reduced star formation, changes in the star formation efficiency are what drives a galaxy deeper into the red cloud, hence retiring it.

scholarly journals The dependence of mass and environment on the secular processes of AGNs in terms of morphology, colour, and specific star-formation rate

2018 ◽  
Vol 620 ◽  
pp. A113 ◽  
Author(s):  
M. Argudo-Fernández ◽  
I. Lacerna ◽  
S. Duarte Puertas
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
High Mass ◽  
Late Type ◽  
Star Forming ◽  
Isolated Galaxies

Context. Galaxy mass and environment play a major role in the evolution of galaxies. In the transition from star-forming to quenched galaxies, active galactic nuclei (AGNs) also have a principal action therein. However, the connections between these three actors are still uncertain. Aims. In this work we investigate the effects of stellar mass and the large-scale structure (LSS) environment on the fraction of optical nuclear activity in a population of isolated galaxies, where AGN would not be triggered by recent galaxy interactions or mergers. Methods. As a continuation of a previous work, we focus on isolated galaxies to study the effect of stellar mass and the LSS in terms of morphology (early- and late-type), colour (red and blue), and specific star-formation rate (quenched and star-forming). To explore where AGN activity is affected by the LSS, we separate galaxies into two groups, of low- and high mass, respectively, and use the tidal strength parameter to quantify the effects. Results. We found that AGN is strongly affected by stellar mass in “active” galaxies (namely late-type, blue, and star-forming), but that mass has no influence on “quiescent” galaxies (namely early-type, red, and quenched), at least for masses down to 1010 M⊙. In relation to the LSS, we found an increase in the fraction of star-forming nuclei galaxies with denser LSS in low-mass star-forming and red isolated galaxies. Regarding AGN, we find a clear increase in the fraction of AGNs with denser environment in quenched and red isolated galaxies, independently of the stellar mass. Conclusions. Active galactic nuclei activity appears to be “mass triggered” in active isolated galaxies. This means that AGN activity is independent of the intrinsic properties of the galaxies, but is dependent on their stellar mass. On the other hand, AGN activity appears to be “environment triggered” in quiescent isolated galaxies, where the fraction of AGNs as a function of specific star formation rate and colour increases from void regions to denser LSS, independently of stellar mass.

scholarly journals CO (J=2-1) Observations of the Molecular Cloud Complex in the Galactic Center

1994 ◽  
Vol 140 ◽  
pp. 168-169
Author(s):  
Tomoharu Oka ◽  
Tetsuo Hasegawa ◽  
Masahiko Hayashi ◽  
Toshihiro Handa ◽  
Sei'ichi Sakamoto
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Galactic Center ◽  
Molecular Gas ◽  
Star Forming ◽  
Near Future ◽  
Cloud Complex ◽  
Mapping Observation

AbstractWe report a large scale mapping observation of the Galactic center region in the CO (J=2-1) line using the Tokyo-NRO 60cm survey telescope. Distribution of the CO (J=2-1) emission in the I-V plane suggests that molecular clouds forms a huge complex (Nuclear Molecular cloud Complex, NMC). Tracers of star formation activities in the last 106-108 years show that star formation has occured in a ring ~ 100 pc in radius. Relative to this Star Forming Ring, the molecular gas is distributed mainly on the positive longitude side. This may indicate that much of the gas in NMC is in transient orbit to fall into the star forming ring or to the nucleus in the near future.

scholarly journals Centrally concentrated molecular gas driving galactic-scale ionized gas outflows in star-forming galaxies

2020 ◽  
Vol 500 (3) ◽  
pp. 3802-3820
Author(s):  
L M Hogarth ◽  
A Saintonge ◽  
L Cortese ◽  
T A Davis ◽  
S M Croom ◽  
...  
Keyword(s):  
Star Formation ◽  
Spatial Resolution ◽  
Large Scale ◽  
Formation Rate ◽  
Control Sample ◽  
Joint Analysis ◽  
Molecular Gas ◽  
Ionized Gas ◽  
Data Set ◽  
Star Forming

ABSTRACT We perform a joint analysis of high spatial resolution molecular gas and star-formation rate (SFR) maps in main-sequence star-forming galaxies experiencing galactic-scale outflows of ionized gas. Our aim is to understand the mechanism that determines which galaxies are able to launch these intense winds. We observed CO(1→0) at 1-arcsec resolution with ALMA in 16 edge-on galaxies, which also have 2-arcsec spatial-resolution optical integral field observations from the SAMI Galaxy Survey. Half the galaxies in the sample were previously identified as harbouring intense and large-scale outflows of ionized gas (‘outflow types’) and the rest serve as control galaxies. The data set is complemented by integrated CO(1→0) observations from the IRAM 30-m telescope to probe the total molecular gas reservoirs. We find that the galaxies powering outflows do not possess significantly different global gas fractions or star-formation efficiencies when compared with a control sample. However, the ALMA maps reveal that the molecular gas in the outflow-type galaxies is distributed more centrally than in the control galaxies. For our outflow-type objects, molecular gas and star-formation are largely confined within their inner effective radius (reff), whereas in the control sample, the distribution is more diffuse, extending far beyond reff. We infer that outflows in normal star-forming galaxies may be caused by dynamical mechanisms that drive molecular gas into their central regions, which can result in locally enhanced gas surface density and star-formation.

scholarly journals Star-formation efficiency at 600Myr of cosmic time

2019 ◽  
Vol 15 (S352) ◽  
pp. 115-118
Author(s):  
Mauro Stefanon ◽  
Ivo Labbé ◽  
Rychard Bouwens ◽  
Pascal Oesch
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Line Emission ◽  
Cosmic Time ◽  
Volume Density ◽  
Star Forming ◽  
Lyman Break Galaxies ◽  
Accelerated Evolution ◽  
Galaxy Assembly ◽  
Formation Efficiency

AbstractCurrent observations suggest an accelerated evolution of the cosmic star formation rate density for 8 < z < 10, indicating that galaxy assembly experienced an extremely intense phase during the first ∼600Myr years of cosmic time. We performed a systematic search of ultrabright star-forming galaxies at z ∼ 8 over the COSMOS/UltraVISTA survey, identifying 16 candidate Lyman-break galaxies. The still large uncertainties on the associated volume density do not yet allow us to ascertain whether a different star-formation efficiency (SFE) existed at early cosmic epochs. Leveraging the deepest Spitzer/IRAC data available from the GREATS program over the CANDELS/GOODS fields, we also constructed stacked SEDs of sub- L* LBGs at z ∼ 8. We find extreme nebular line emission (EW0 (Hα) ∼ 1000Å), high specific star-formation rates (∼10/Gyr) and indication of an inverse Balmer break. These results point toward very young ages (<100 Myr), and, combined with measurements at lower redshifts, that the SFE evolved only marginally during the first ∼1.5Gyr of cosmic history.

scholarly journals The properties of radio and mid-infrared detected galaxies and the effect of environment on the co-evolution of AGN and star formation at z ∼ 1

2020 ◽  
Vol 494 (4) ◽  
pp. 5374-5395 ◽  
Author(s):  
Lu Shen ◽  
Brian C Lemaux ◽  
Lori M Lubin ◽  
John McKean ◽  
Neal A Miller ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Formation Rate ◽  
Rapid Quenching ◽  
Radio Luminosity ◽  
Star Forming ◽  
Cluster Group ◽  
Significant Difference ◽  
Almost All ◽  
Quenching Time

ABSTRACT In this study, we investigate 179 radio-infrared (IR) galaxies drawn from a sample of spectroscopically confirmed galaxies, which are detected in radio and mid-IR (MIR) in the redshift range of 0.55 ≤ z ≤ 1.30 in the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey. We constrain the active galactic nuclei (AGN) contribution to the total IR luminosity (fAGN), and estimate the AGN luminosity (LAGN) and the star formation rate (SFR). Based on the fAGN and radio luminosity, radio–IR galaxies are split into galaxies that host either high- or low-fAGN AGN (high-/low-fAGN), and star-forming galaxies (SFGs) with little to no AGN activity. We study the properties of the three radio–IR sub-samples comparing to an underlying parent sample. In the comparison of radio luminosity of three sub-samples, no significant difference was found, which could be due to the combined contribution of radio emission from AGN and star formation. We find a positive relationship between LAGN and specific SFR (sSFR) for both AGN sub-samples, strongly suggesting a co-evolution scenario of AGN and SF in these galaxies. A toy model is designed to demonstrate this co-evolution scenario, where we find that, in almost all cases, a rapid quenching time-scale is required, which we argue is a signature of AGN quenching. The environmental preference for intermediate/infall regions of clusters/groups remains across the co-evolution scenario, which suggests that galaxies might be in an orbital motion around the cluster/group during the scenario.

scholarly journals Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey: Candidate galaxy clusters at 1.3 < z < 3 selected by high star-formation rate

2018 ◽  
Vol 620 ◽  
pp. A198 ◽  
Author(s):  
C. Martinache ◽  
A. Rettura ◽  
H. Dole ◽  
M. Lehnert ◽  
B. Frye ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Formation Rate ◽  
Physical Processes ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Efficient Detection ◽  
Star Formation In Galaxies ◽  
The Individual ◽  
Massive Clusters

There is a lack of large samples of spectroscopically confirmed clusters and protoclusters at high redshifts, z > 1.5. Discovering and characterizing distant (proto-)clusters is important for yielding insights into the formation of large-scale structure and on the physical processes responsible for regulating star-formation in galaxies in dense environments. The Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey was initiated to identify these characteristically faint and dust-reddened sources during the epoch of their early assembly. We present Spitzer/IRAC observations of 82 galaxy (proto-)cluster candidates at 1.3 < zp < 3.0 that were vetted in a two step process: (1) using Planck to select by color those sources with the highest star-formation rates, and (2) using Herschel at higher resolution to separate out the individual red sources. The addition of the Spitzer data enables efficient detection of the central and massive brightest red cluster galaxies (BRCGs). We find that BRCGs are associated with highly significant, extended and crowded regions of IRAC sources which are more overdense than the field. This result corroborates our hypothesis that BRCGs within the Planck–Herschel sources trace some of the densest and actively star-forming proto-clusters in the early Universe. On the basis of a richness-mass proxy relation, we obtain an estimate of their mean masses which suggests our sample consists of some of the most massive clusters at z ≈ 2 and are the likely progenitors of the most massive clusters observed today.

scholarly journals 4.6. Structure of the molecular cloud and star-forming activity in the Sagittarius B2 region

1998 ◽  
Vol 184 ◽  
pp. 177-178 ◽  
Author(s):  
Fumio Sato ◽  
Tetsuo Hasegawa ◽  
John B. Whiteoak ◽  
Ryosuke Miyawaki
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Large Scale ◽  
Massive Star ◽  
Galactic Center ◽  
Full Description ◽  
Grid Spacing ◽  
Restricted Area ◽  
Star Forming ◽  
Right Ascension

Sgr B2 is one of the most active star-forming complexes in our Galaxy located ~100 pc from the Galactic center. Whiteoak et al. (1987) found that groups of the OH and H2CO masers and the compact HII regions are aligned in a north-south line, and suggested that star formation there is being triggered by a single large-scale event such as an interaction between molecular clouds. In order to investigate the total molecular cloud distribution and the triggering mechanism of the active massive-star formation in the Sgr B2 region, we mapped it in the 13CO and C18O (J = 1–0) lines with the Nobeyama 45 m telescope in 1988 March and May. In the 13CO line, an area was mapped of 345″ in right ascension and 495″ in declination covering the whole Sgr B2 molecular cloud at a grid spacing of 15″. In the C18O line, more restricted area was observed at 7.5″ or 15″ spacing. The HPBW of the 45 m telescope was 16″ at 110 GHz. Full description of the observations will be given elsewhere (Whiteoak et al. 1997).

scholarly journals Close pairs of galaxies with different activity levels

2013 ◽  
Vol 9 (S304) ◽  
pp. 327-330 ◽  
Author(s):  
T. A. Nazaryan ◽  
A. R. Petrosian ◽  
A. A. Hakobyan ◽  
B. J. McLean ◽  
D. Kunth
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Spectral Properties ◽  
Large Scale ◽  
Interaction Strength ◽  
Galactic Nuclei ◽  
Morphological Type ◽  
Activity Levels ◽  
Star Forming ◽  
Interacting Systems

AbstractWe selected and studied 180 pairs with d V < 800 km s−1 and Dp < 60 kpc containing Markarian (MRK) galaxies to investigate the dependence of galaxies integral parameters, star-formation (SF) and active galactic nuclei (AGN) properties on kinematics of pairs, their structure and large-scale environments. Projected radial separation Dp and perturbation level P are better measures of interaction strength than dV. The latter correlates with the density of large-scale environment and with the morphologies of galaxies. Both galaxies in a pair are of the same nature, the only difference is that MRK galaxies are usually brighter than their neighbors. Specific star formation rates (SSFR) of galaxies in pairs with smaller Dp or d V is in average 0.5 dex higher than that of galaxies in pairs with larger Dp or d V. Closeness of a neighbor with the same and later morphological type increases the SSFR, while earlier-type neighbors do not increase SSFR. Major interactions/mergers trigger SF and AGN more effectively than minor ones. The fraction of AGNs is higher in more perturbed pairs and pairs with smaller Dp. AGNs typically are in stronger interacting systems than star-forming and passive galaxies. There are correlations of both SSFRs and spectral properties of nuclei between pair members.

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