scholarly journals Resolving discs and mergers in z ∼ 2 heavily reddened quasars and their companion galaxies with ALMA

2021 ◽  
Vol 503 (4) ◽  
pp. 5583-5599
Author(s):  
Manda Banerji ◽  
Gareth C Jones ◽  
Stefano Carniani ◽  
Colin DeGraf ◽  
Jeff Wagg
Keyword(s):  
Black Hole ◽  
Host Galaxy ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Local Environments ◽  
The Galaxy ◽  
Major Merger ◽  
Galaxy Masses ◽  
Array Imaging

ABSTRACT We present sub-arcsecond resolution Atacama Large Millimeter Array imaging of the CO(3–2) emission in two z ∼ 2.5 heavily reddened quasars (HRQs) – ULASJ1234+0907 and ULASJ2315+0143 – and their companion galaxies. Dynamical modelling of the resolved velocity fields enables us to constrain the molecular gas morphologies and host galaxy masses. Combining the new data with extensive multiwavelength observations, we are able to study the relative kinematics of different molecular emission lines, the molecular gas fractions, and the locations of the quasars on the MBH–Mgal relation. Despite having similar black hole properties, the two HRQs display markedly different host galaxy properties and local environments. J1234 has a very massive host – Mdyn ∼ 5 × 1011 M⊙ and two companion galaxies that are similarly massive located within 200 kpc of the quasar. The molecular gas fraction is low (∼6 per cent). The significant ongoing star formation in the host galaxy is entirely obscured at rest-frame ultraviolet (UV) and optical wavelengths. J2315 is resolved into a close-separation major merger (Δr = 15 kpc; Δv = 170 km s−1) with a ∼1:2 mass ratio. The total dynamical mass is estimated to be ≲1011 M⊙ and the molecular gas fraction is high (>45 per cent). A new HSC image of the galaxy shows unobscured UV-luminous star-forming regions co-incident with the extended reservoir of cold molecular gas in the merger. We use the outputs from the Illustris simulations to track the growth of such massive black holes from z ∼ 6 to the present day. While J1234 is consistent with the simulated z ∼ 2 relation, J2315 has a black hole that is overmassive relative to its host galaxy.

Gamma-ray burst models

2007 ◽  
Vol 365 (1854) ◽  
pp. 1277-1280 ◽  
Author(s):  
Andrew King
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Neutron Star ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Close Binaries ◽  
Host Galaxy ◽  
Star Forming ◽  
Star Forming Regions ◽  
Long Duration

I consider various possibilities for making gamma-ray bursts, particularly from close binaries. In addition to the much-studied neutron star+neutron star and black hole+neutron star cases usually considered good candidates for short-duration bursts, there are also other possibilities. In particular, neutron star+massive white dwarf has several desirable features. These systems are likely to produce long-duration gamma-ray bursts (GRBs), in some cases definitely without an accompanying supernova, as observed recently. This class of burst would have a strong correlation with star formation and occur close to the host galaxy. However, rare members of the class need not be near star-forming regions and could have any type of host galaxy. Thus, a long-duration burst far from any star-forming region would also be a signature of this class. Estimates based on the existence of a known progenitor suggest that this type of GRB may be quite common, in agreement with the fact that the absence of a supernova can only be established in nearby bursts.

scholarly journals The ALMaQUEST Survey: VI. The molecular gas main sequence of ‘retired’ regions in galaxies.

2020 ◽  
Author(s):  
Sara L Ellison ◽  
Lihwai Lin ◽  
Mallory D Thorp ◽  
Hsi-An Pan ◽  
Sebastian F Sánchez ◽  
...  
Keyword(s):  
Main Sequence ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Gas Main ◽  
The Galaxy ◽  
Order Of Magnitude ◽  
Using Data ◽  
Gas Fractions

Abstract In order to investigate the role of gas in the demise of star formation on kpc-scales, we compare the resolved molecular gas main sequence (rMGMS: $\Sigma _{\rm H_2}$ vs Σ⋆) of star-forming regions to the sequence of ‘retired’ regions that have ceased to form new stars. Using data from the ALMaQUEST survey, we find that retired spaxels form a rMGMS that is distinct from that of star-forming spaxels, offset to lower $\Sigma _{\rm H_2}$ at fixed Σ⋆ by a factor of ∼5. We study the rMGMS of star-forming and retired spaxels on a galaxy-by-galaxy basis for eight individual ALMaQUEST galaxies. Six of these galaxies have their retired spaxels concentrated within the central few kpc. Molecular gas is detected in 40-100% of retired spaxels in the eight galaxies in our sample. Both the star-forming and retired rMGMS show a diversity in normalization from galaxy-to-galaxy. However, in any given galaxy, the rMGMS for retired regions is found to be distinct from the star-forming sequence and gas fractions of retired spaxels are up to an order of magnitude lower than the star-forming spaxels. We conclude that quenching is associated with a depletion (but not absence) of molecular gas via a mechanism that typically begins in the centre of the galaxy.

scholarly journals Masers and Galactic structure: Micro-arcsecond astrometry with the VLBA

2007 ◽  
Vol 3 (S242) ◽  
pp. 348-355 ◽  
Author(s):  
M. J. Reid ◽  
A. Brunthaler ◽  
K. M. Menten ◽  
Xu Ye ◽  
Zheng Xing-Wu ◽  
...  
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
Galactic Plane ◽  
Infrared Images ◽  
Star Forming ◽  
Supermassive Black Hole ◽  
Star Forming Regions ◽  
The Galaxy ◽  
Trigonometric Parallaxes ◽  
Sgr A

AbstractAstrometric observations with the VLBA with accuracies approaching ~ 10 μas are being conducted in order to better understand the Galaxy. The location of Sgr A* on infrared images can be determined with an accuracy of a few mas, using stars with SiO maser emission as a calibration grid for infrared images. The apparent proper motion of Sgr A*, which is dominated by the effects of the orbit of the Sun around the Galactic center, has been measured with high accuracy. This measurement strongly constrains Θ0R0 and offers a dynamical definition of the Galactic plane with Sgr A* at its origin. The intrinsic motion of Sgr A* is very small and comparable to that expected for a supermassive black hole. When combined with infrared results, this provides overwhelming evidence that Sgr A* is a supermassive black hole. Finally, we are engaged in a large project to map the spiral structure and kinematics of the Galaxy. Preliminary trigonometric parallaxes, obtained with the VLBA, to eight massive star forming regions are presented.

scholarly journals Survival of molecular gas in a stellar feedback-driven outflow witnessed with the MUSE TIMER project and ALMA

2019 ◽  
Vol 488 (3) ◽  
pp. 3904-3928 ◽  
Author(s):  
Ryan Leaman ◽  
Francesca Fragkoudi ◽  
Miguel Querejeta ◽  
Gigi Y C Leung ◽  
Dimitri A Gadotti ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Mechanical Energy ◽  
Molecular Gas ◽  
Ionized Gas ◽  
Star Forming ◽  
Stellar Feedback ◽  
Dominant Component ◽  
The Galaxy ◽  
Field Lines

ABSTRACT Stellar feedback plays a significant role in modulating star formation, redistributing metals, and shaping the baryonic and dark structure of galaxies – however, the efficiency of its energy deposition to the interstellar medium is challenging to constrain observationally. Here we leverage HST and ALMA imaging of a molecular gas and dust shell ($M_{\mathrm{ H}_2} \sim 2\times 10^{5}\, {\rm M}_{\odot }$) in an outflow from the nuclear star-forming ring of the galaxy NGC 3351, to serve as a boundary condition for a dynamical and energetic analysis of the outflowing ionized gas seen in our MUSE TIMER survey. We use starburst99 models and prescriptions for feedback from simulations to demonstrate that the observed star formation energetics can reproduce the ionized and molecular gas dynamics – provided a dominant component of the momentum injection comes from direct photon pressure from young stars, on top of supernovae, photoionization heating, and stellar winds. The mechanical energy budget from these sources is comparable to low luminosity active galactic neuclei, suggesting that stellar feedback can be a relevant driver of bulk gas motions in galaxy centres – although here ≲10−3 of the ionized gas mass is escaping the galaxy. We test several scenarios for the survival/formation of the cold gas in the outflow, including in situ condensation and cooling. Interestingly, the geometry of the molecular gas shell, observed magnetic field strengths and emission line diagnostics are consistent with a scenario where magnetic field lines aided survival of the dusty ISM as it was initially launched (with mass-loading factor ≲1) from the ring by stellar feedback. This system’s unique feedback-driven morphology can hopefully serve as a useful litmus test for feedback prescriptions in magnetohydrodynamical galaxy simulations.

scholarly journals Using stellar population studies to determine the progenitors of GRBs and SNe

2009 ◽  
Vol 5 (S262) ◽  
pp. 436-437
Author(s):  
Christina C. Thöne ◽  
Lise Christensen ◽  
Johan P. U. Fynbo
Keyword(s):  
Emission Line ◽  
Stellar Population ◽  
Population Studies ◽  
Population Models ◽  
Host Galaxy ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions

AbstractWe present spatially resolved emission line studies of three nearby GRB and SN hosts with longslit and/or IFU observations. We compare the environment of the GRBs/SNe with those of other star-forming regions in the host galaxy and try to get informations on the progenitor from stellar population models and metallicities.

scholarly journals Accretion and Outflow in Active Galaxies

2009 ◽  
Vol 5 (S267) ◽  
pp. 273-282
Author(s):  
Andrew King
Keyword(s):  
Black Hole ◽  
Large Scale ◽  
Host Galaxy ◽  
Small Scale ◽  
Gas Flows ◽  
Inverse Compton ◽  
The Galaxy ◽  
Black Hole Growth ◽  
Lower Excitation ◽  
Hole Growth

AbstractI review accretion and outflow in active galactic nuclei. Accreti4on appears to occur in a series of very small-scale, chaotic events, whose gas flows have no correlation with the large-scale structure of the galaxy or with each other. The accreting gas has extremely low specific angular momentum and probably represents only a small fraction of the gas involved in a galaxy merger, which may be the underlying driver.Eddington accretion episodes in AGN must be common in order for the supermassive black holes to grow. I show that they produce winds with velocities v ~ 0.1c and ionization parameters implying the presence of resonance lines of helium-like and hydrogen-like iron. The wind creates a strong cooling shock as it interacts with the interstellar medium of the host galaxy, and this cooling region may be observable in an inverse Compton continuum and lower-excitation emission lines associated with lower velocities. The shell of matter swept up by the shocked wind stalls unless the black hole mass has reached the value Mσ implied by the M–σ relation. Once this mass is reached, further black hole growth is prevented. If the shocked gas did not cool as asserted above, the resulting (“energy-driven”) outflow would imply a far smaller SMBH mass than actually observed. Minor accretion events with small gas fractions can produce galaxy-wide outflows, including fossil outflows in galaxies where there is little current AGN activity.

scholarly journals The Connection between Molecular Gas and Star Formation in XUV Disks

2016 ◽  
Vol 11 (S321) ◽  
pp. 214-216
Author(s):  
Linda C. Watson
Keyword(s):  
Star Formation ◽  
Molecular Hydrogen ◽  
Optical Disk ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions

AbstractWe found that star-forming regions in extended ultraviolet (XUV) disks are generally consistent with the molecular-hydrogen Kennicutt-Schmidt law that applies within the inner, optical disk. This is true for star formation rates based on Hα + 24 μm data or FUV + 24 μm data. We estimated that the star-forming regions have ages of 1 − 7 Myr and propose that the presence or absence of molecular gas provides an additional “clock” that may help distinguish between aging and stochasticity as the explanation for the low Hα-to-FUV flux ratios in XUV disks. This contribution is a summary of the work originally presented in Watson et al. (2016).

scholarly journals Shocked Molecular Hydrogen from Star Forming Regions

1987 ◽  
Vol 115 ◽  
pp. 181-181 ◽  
Author(s):  
Adair P. Lane ◽  
John Bally
Keyword(s):  
Shock Waves ◽  
High Velocity ◽  
Molecular Hydrogen ◽  
Near Infrared ◽  
Young Stars ◽  
Emission Lines ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Post Shock

Near infrared (2 micron) emission lines from molecular hydrogen provide a powerful probe of the morphology and energetics of outflows associated with stellar birth. The H2 emission regions trace the location of shock waves formed when the high velocity outflow from young stars encounters dense quiescent gas. Since H2 is the dominant coolant of the hot post-shock molecular gas, the H2 lines provide a measure of the fraction of the total mechanical luminosity radiated away from the cloud.

scholarly journals Are interstellar ices porous, and how do the pores collapse?

2015 ◽  
Vol 11 (A29A) ◽  
Author(s):  
C. R. Hill ◽  
C. Mitterdorfer ◽  
T. G. A. Youngs ◽  
D. T. Bowron ◽  
N. Pascual ◽  
...  
Keyword(s):  
Solar System ◽  
Amorphous Solid ◽  
Growth Conditions ◽  
Molecular Gas ◽  
Pore Collapse ◽  
Star Forming ◽  
Gas Phases ◽  
Star Forming Regions ◽  
Solar System Objects ◽  
Interstellar Ices

Amorphous solid water (ASW) is of great importance in astrochemistry as it has been detected in star forming regions, comets, and cold solar-system objects. A key property of ASW is its porous nature (with the extent of porosity reflecting the formation and growth conditions) and the subsequent pore collapse when the ice is heated. If interstellar ices are porous there are huge implications to both the process of planet formation and the budgets of molecular gas in the solid and gas phases. It is therefore vital to understand ASW porosity over astronomically relevant conditions in order to effectively model its potential effects on these processes.

scholarly journals Molecular Gas in the Magellanic Clouds

1999 ◽  
Vol 190 ◽  
pp. 67-73 ◽  
Author(s):  
Mónica Rubio
Keyword(s):  
Line Emission ◽  
Magellanic Clouds ◽  
Gas Content ◽  
Molecular Gas ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Hydrogen Column Density ◽  
Spatial Coverage ◽  
Co Emission

The molecular gas content in the Magellanic Clouds has been studied, with different spatial coverage and resolution, through obervations of CO(1-0) line emission. In the LMC and the SMC the molecular gas is dominated by clouds whose properties are different from those of their Galactic counterparts. The relation between the intensity of CO emission and molecular hydrogen column density, or the conversion factor X, is different than that of molecular clouds in our Galaxy and depends on the ambient physical conditions. Studying the molecular gas through observations in the H2 emission line may prove an alternative way to determine the molecular content associated with star forming regions in the Magellanic Clouds. In particular, results obtained towards 30 Doradus in the LMC are presented.

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