Abstract
Coupling of black hole mass to the cosmic expansion has been suggested as a possible path to understanding the dark energy content of the Universe. We test this hypothesis by comparing the ...supermassive black hole (SMBH) mass density at
z
= 0 to the total mass accreted in active galactic nuclei (AGN) since
z
= 6, to constrain how much of the SMBH mass density can arise from cosmologically coupled growth, as opposed to growth by accretion. Using an estimate of the local SMBH mass density of ≈1.0 × 10
6
M
⊙
Mpc
−1
, a radiative accretion efficiency,
η
, in the range 0.05 <
η
< 0.3, and the observed AGN luminosity density at
z
≈ 4, we constrain the value of the coupling constant between the scale size of the Universe and the black hole mass,
k
, to lie in the range 0 <
k
≲ 2, below the value of
k
= 3 needed for black holes to be the source term for dark energy. Initial estimates of the gravitational-wave background (GWB) using pulsar timing arrays, however, favor a higher SMBH mass density at
z
= 0. We show that if we adopt such a mass density at
z
= 0 of ≈7.4 × 10
6
M
⊙
Mpc
−1
, this makes
k
= 3 viable even for low radiative efficiencies, and may exclude nonzero cosmological coupling. We conclude that, although current estimates of the SMBH mass density based on the black hole mass–bulge mass relation probably exclude
k
= 3, the possibility remains open that, if the GWB is due to SMBH mergers,
k
> 2 is preferred.
Recent simulations and observations of massive galaxy cluster evolution predict that the majority of stellar mass buildup happens within cluster members by z = 2, before cluster virialization. ...Protoclusters rich with dusty, star-forming galaxies (DSFGs) at z > 3 are the favored candidate progenitors for these massive galaxy clusters at z ∼ 0. We present here the first study analyzing stellar emission along with cold dust and gas continuum emission in a spectroscopically confirmed z = 4.002 protocluster core rich with DSFGs, the Distant Red Core (DRC). We combine new Hubble Space Telescope and Spitzer data with existing Gemini, Herschel, and Atacama Large Millimeter/submillimeter Array observations to derive individual galaxy-level properties and compare them to coeval field and other protocluster galaxies. All of the protocluster members are massive (>1010 M ), but not significantly more so than their coeval field counterparts. Within uncertainty, all are nearly indistinguishable from galaxies on the star-forming versus stellar mass main-sequence relationship and the star formation efficiency plane. Assuming no future major influx of fresh gas, we estimate that these gaseous DSFGs will deplete their gas reservoirs in ∼300 Myr, becoming the massive quiescent ellipticals dominating cluster cores by z ∼ 3. Using various methodologies, we derive a total z = 4 halo mass of ∼1014 M and estimate that the DRC will evolve to become an ultramassive cluster core of mass 1015 M by z = 0.
Abstract
Observations have found black holes spanning 10 orders of magnitude in mass across most of cosmic history. The Kerr black hole solution is, however, provisional as its behavior at infinity ...is incompatible with an expanding universe. Black hole models with realistic behavior at infinity predict that the gravitating mass of a black hole can increase with the expansion of the universe independently of accretion or mergers, in a manner that depends on the black hole’s interior solution. We test this prediction by considering the growth of supermassive black holes in elliptical galaxies over 0 <
z
≲ 2.5. We find evidence for cosmologically coupled mass growth among these black holes, with zero cosmological coupling excluded at 99.98% confidence. The redshift dependence of the mass growth implies that, at
z
≲ 7, black holes contribute an effectively constant cosmological energy density to Friedmann’s equations. The continuity equation then requires that black holes contribute cosmologically as vacuum energy. We further show that black hole production from the cosmic star formation history gives the value of Ω
Λ
measured by Planck while being consistent with constraints from massive compact halo objects. We thus propose that stellar remnant black holes are the astrophysical origin of dark energy, explaining the onset of accelerating expansion at
z
∼ 0.7.
Abstract
The assembly of stellar and supermassive black hole (SMBH) mass in elliptical galaxies since
z
∼ 1 can help to diagnose the origins of locally observed correlations between SMBH mass and ...stellar mass. We therefore construct three samples of elliptical galaxies, one at
z
∼ 0 and two at 0.7 ≲
z
≲ 2.5, and quantify their relative positions in the
M
BH
−
M
*
plane. Using a Bayesian analysis framework, we find evidence for translational offsets in both stellar mass and SMBH mass between the local sample and both higher-redshift samples. The offsets in stellar mass are small, and consistent with measurement bias, but the offsets in SMBH mass are much larger, reaching a factor of 7 between
z
∼ 1 and
z
∼ 0. The magnitude of the SMBH offset may also depend on redshift, reaching a factor of ∼20 at
z
∼ 2. The result is robust against variation in the high- and low-redshift samples and changes in the analysis approach. The magnitude and redshift evolution of the offset are challenging to explain in terms of selection and measurement biases. We conclude that either there is a physical mechanism that preferentially grows SMBHs in elliptical galaxies at
z
≲ 2, or that selection and measurement biases are both underestimated, and depend on redshift.
Extreme submillimetre starburst galaxies Rowan-Robinson, M.; Wang, Lingyu; Farrah, Duncan ...
Astronomy and astrophysics (Berlin),
11/2018, Letnik:
619
Journal Article
Recenzirano
Odprti dostop
We have used two catalogues, a Herschel catalogue selected at 500 μm (HerMES) and an IRAS catalogue selected at 60 μm (RIFSCz), to contrast the sky at these two wavelengths. Both surveys demonstrate ...the existence of “extreme” starbursts, with star-formation rates (SFRs) > 5000 M⊙ yr−1. The maximum intrinsic star-formation rate appears to be ~30 000 M⊙ yr−1. The sources with apparent SFR estimates higher than this are in all cases either lensed systems, blazars, or erroneous photometric redshifts. At redshifts between three and five, the time-scale for the Herschel galaxies to make their current mass of stars at their present rate of star formation is ~108 yr, so these galaxies are making a significant fraction of their stars in the current star-formation episode. Using dust mass as a proxy for gas mass, the Herschel galaxies at redshift three to five have gas masses comparable to their mass in stars. Of the 38 extreme starbursts in our Herschel survey for which we have more complete spectral energy distribution (SED) information, 50% show evidence for QSO-like optical emission, or exhibit AGN dust tori in the mid-infrared SEDs. In all cases however the infrared luminosity is dominated by a starburst component. We derive a mean covering factor for AGN dust as a function of redshift and derive black hole masses and black hole accretion rates. There is a universal ratio of black-hole mass to stellar mass in these high redshift systems of ~10−3, driven by the strong period of star-formation and black-hole growth at z = 1−5.
Multiwavelength surveys covering large sky volumes are necessary to obtain an accurate census of rare objects such as high-luminosity and/or high-redshift active galactic nuclei (AGNs). Stripe 82X is ...a 31.3 X-ray survey with Chandra and XMM-Newton observations overlapping the legacy Sloan Digital Sky Survey Stripe 82 field, which has a rich investment of multiwavelength coverage from the ultraviolet to the radio. The wide-area nature of this survey presents new challenges for photometric redshifts for AGNs compared to previous work on narrow-deep fields because it probes different populations of objects that need to be identified and represented in the library of templates. Here we present an updated X-ray plus multiwavelength matched catalog, including Spitzer counterparts, and estimated photometric redshifts for 5961 (96% of a total of 6181) X-ray sources that have a normalized median absolute deviation, , and an outlier fraction, = 13.7%. The populations found in this survey and the template libraries used for photometric redshifts provide important guiding principles for upcoming large-area surveys such as eROSITA and 3XMM (in X-ray) and the Large Synoptic Survey Telescope (optical).
We report the first results of AS2UDS, an 870 m continuum survey with the Atacama Large Millimeter/Submillimeter Array (ALMA) of a total area of ∼50 arcmin2 comprising a complete sample of 716 ...submillimeter sources drawn from the SCUBA-2 Cosmology Legacy Survey (S2CLS) map of the UKIDSS/UDS field. The S2CLS parent sample covers a 0.96 degree2 field at 850 = 0.90 0.05 mJy beam−1. Our deep, high-resolution ALMA observations with 870 ∼ 0.25 mJy and a 0 15-0 30 FWHM synthesized beam, provide precise locations for 695 submillimeter galaxies (SMGs) responsible for the submillimeter emission corresponding to 606 sources in the low-resolution, single-dish map. We measure the number counts of SMGs brighter than S870 ≥ 4 mJy, free from the effects of blending and show that the normalization of the counts falls by 28% 2% in comparison with the SCUBA-2 published counts, but that the shape remains unchanged. We determine that 44 − 14 + 16 % of the brighter single-dish sources with S850 ≥ 9 mJy consist of a blend of two or more ALMA-detectable SMGs brighter than S870 ∼ 1 mJy (corresponding to a galaxy with a total-infrared luminosity of LIR 1012 L ), in comparison with 28% 2% for the single-dish sources at S850 ≥ 5 mJy. Using the 46 single-dish submillimeter sources that contain two or more ALMA-detected SMGs with photometric redshifts, we show that there is a significant statistical excess of pairs of SMGs with similar redshifts (<1% probability of occurring by chance), suggesting that at least 30% of these blends arise from physically associated pairs of SMGs.
Abstract
Low-ionization broad absorption line QSOs (LoBALs) are suspected to be merging systems in which extreme, active galactic nucleus-driven outflows have been triggered. Whether or not LoBALs ...are uniquely associated with mergers, however, has yet to be established. To characterize the morphologies of LoBALs, we present the first high-resolution morphological analysis of a volume-limited sample of 22 Sloan Digital Sky Survey (SDSS)-selected LoBALs at 0.5 <
z
< 0.6 from Hubble Space Telescope Wide Field Camera 3 observations. Host galaxies are resolved in 86% of the systems in F125W, which is sensitive to old stellar populations, while only 18% are detected in F475W, which traces young, unobscured stellar populations. Signs of recent or ongoing tidal interaction are present in 45%–64% of the hosts, including double nuclei, tidal tails, bridges, plumes, shells, and extended debris. Ongoing interaction with a companion is apparent in 27%−41% of the LoBALs, with as much as 1/3 of the sample representing late-stage mergers at projected nuclear separations <10 kpc. Detailed surface brightness modeling indicates that 41% of the hosts are bulge dominated while only 18% are disks. We discuss trends in various properties as a function of merger stage and parametric morphology. Notably, mergers are associated with slower, dustier winds than those seen in undisturbed/unresolved hosts. Our results favor an evolutionary scenario in which quasar-level accretion during various merger stages is associated with the observed outflows in low-
z
LoBALs. We discuss differences between LoBALs and FeLoBALs and show that selection via the traditional balnicity index would have excluded all but one of the mergers.
We report molecular gas observations of IRAS 20100−4156 and IRAS 03158+4227, two local ultraluminous infrared galaxies (ULIRGs) hosting some of the fastest and most massive molecular outflows known. ...Using Atacama Large Millimeter Array and Plateau de Bure Interferometer observations, we spatially resolve the CO (1−0) emission from the outflowing molecular gas in both and find maximum outflow velocities of vmax ∼ 1600 and ∼1700 km s−1 for IRAS 20100−4156 and IRAS 03158+4227, respectively. We find total gas mass outflow rates of and ∼350 M yr−1, respectively, corresponding to molecular gas depletion timescales and ∼16 Myr. This is nearly 3 times shorter than the depletion timescales implied by star formation, and ∼46 Myr, respectively. To determine the outflow driving mechanism, we compare the starburst luminosity (L*) and active galactic nucleus (AGN) luminosity (LAGN) to the outflowing energy and momentum fluxes, using mid-infrared spectral decomposition to discern LAGN. Comparison to other molecular outflows in ULIRGs reveals that outflow properties correlate similarly with L* and LIR as with LAGN, indicating that AGN luminosity alone may not be a good tracer of feedback strength and that a combination of AGN and starburst activity may be driving the most powerful molecular outflows. We also detect the OH 1.667 GHz maser line from both sources and demonstrate its utility in detecting molecular outflows.
Abstract
We demonstrate a single-parameter route for reproducing higher mass objects as observed in the LIGO–Virgo mass distribution, using only the isolated-binary stellar evolution channel. This ...single parameter encodes the cosmological mass growth of compact stellar remnants that exceed the Tolman–Oppenheimer–Volkoff limit. Cosmological mass growth appears in known solutions to General Relativity with cosmological boundary conditions. We consider the possibility of solutions with cosmological boundary conditions, which reduce to Kerr on timescales short compared to the Hubble time. We discuss complementary observational signatures of these solutions that can confirm or invalidate their astrophysical relevance.
PDF
