We study the evolution of galaxies and the circumgalactic medium (CGM) through cosmic time by correlating ∼50,000 Mg ii absorbers, tracers of cool gas (∼104 K), detected in the Sloan Digital Sky ...Survey quasar spectra with galaxies detected in the DESI Legacy Imaging Surveys. By doing so, we extract the properties of galaxies associated with absorbers from redshift 0.4 to 1.3 with effectively ∼15,000 pairs and explore the covering fraction of Mg ii absorbers as a function of galaxy type, stellar mass, impact parameter, and redshift. We find that the gas covering fraction increases with stellar mass of galaxies by . However, after we normalize the impact parameter by the virial radius of dark matter halos, the gas profiles around galaxies with masses ranging from 109 to become weakly dependent on stellar mass. In addition, the gas distribution depends on galaxy type: the covering fraction within around star-forming galaxies is 2-4 times higher than that around passive galaxies at all redshifts. We find that the covering fraction of strong absorbers ( ) around both types of galaxies evolves significantly with redshift, similarly to the evolution of star formation rate (SFR) of galaxies, while such an evolution is not detected for weak absorbers ( ). We quantify the H i mass traced by strong absorbers and find that the gas mass around galaxies evolves consistently with the SFR of galaxies. This result suggests that the properties of galaxies and their CGM coevolve through cosmic time. Finally, we discuss the origins of strong absorbers around passive galaxies and argue that its redshift evolution may trace the star formation activity of satellite galaxies.
We study the distribution and kinematics of the cool circumgalactic medium (CGM) of emission line galaxies (ELGs) traced by metal absorption lines. Using about 200,000 ELGs from SDSS-IV eBOSS and ...half a million background quasars from SDSS, we measure the median absorption strength of Mg ii and Fe ii lines in quasar spectra for impact parameters ranging from 10 kpc to 1 Mpc. For comparison, we measure the same quantity around luminous red galaxies (LRGs). On scales greater than 100 kpc both ELGs and LRGs exhibit similar absorption profiles. However, metal absorption is 5-10 times stronger around ELGs on smaller scales. The metal absorption strength is anisotropic, with an excess along the minor axis of the galaxies, indicating an outflow origin of the absorbing gas. The ratio between the velocity dispersion of the cool CGM and that of its host dark matter halo is about one for ELGs but about half for LRGs. These results show that the dichotomy of galaxy types is reflected in both the density distribution and kinematics of the CGM traced by metal absorption lines. Our results provide strong evidence that the CGM of ELGs is enriched by gas outflows generated by star formation.
Metal abundance and its evolution are studied for Mg ii quasar absorption line systems from their weak, unsaturated spectral lines using stacked spectra from the archived data of the Sloan Digital ...Sky Survey. They show an abundance pattern that resembles that of the Galactic halo or Small Magellanic Cloud, with metallicity Z/H showing an evolution from redshift z = 2 to 0.5: metallicity becomes approximately solar or even larger at . We show that the evolution of the metal abundance traces the cumulative amount of the hydrogen fuel consumed in star formation in galaxies. With the aid of a spectroscopic simulation code, we infer the median gas density of the cloud to be roughly 0.3 , with which the elemental abundance in various ionization stages, in particular C i, is consistently explained. This gas density implies that the size of the Mg ii clouds is of the order of 0.03 kpc, which suggests that individual Mg ii clouds around a galaxy are of a baryonic mass typically . This means that Mg ii clouds are numerous and "foamy," rather than a large entity that covers a sizable fraction of galaxies with a single cloud.
We characterize the luminosity functions of galaxies residing in z ∼ 0 groups and clusters over the broadest ranges of luminosity and mass reachable by the Sloan Digital Sky Survey. Our measurements ...cover four orders of magnitude in luminosity, down to about M
r = −12 mag or L = 107 L⊙, and three orders of magnitude in halo mass, from 1012 to 1015 M⊙. We find a characteristic scale, M
r ∼ −18 mag or L ∼ 109 L⊙, below which the slope of the luminosity function becomes systematically steeper. This trend is present for all halo masses and originates mostly from red satellites. This ubiquitous faint-end upturn suggests that it is formation, rather than halo-specific environmental effect, that plays a major role in regulating the stellar masses of faint satellites. We show that the satellite luminosity functions can be described in a simple manner by a double Schechter function with amplitudes scaling with halo mass over the entire range of observables. Combining these conditional luminosity functions with the dark matter halo mass function, we accurately recover the entire field luminosity function over 10 visual magnitudes and reveal that satellite galaxies dominate the field luminosity function at magnitudes fainter than −17. We find that the luminosity functions of blue and red satellite galaxies show distinct shapes and we present estimates of the stellar mass fraction as a function of halo mass and galaxy type. Finally, using a simple model, we demonstrate that the abundances and the faint-end slopes of blue and red satellite galaxies can be interpreted in terms of their formation history, with two distinct modes separated by some characteristic time.
On the environments of giant radio galaxies Lan 藍鼎文, Ting-Wen; Xavier Prochaska, J
Monthly notices of the Royal Astronomical Society,
04/2021, Letnik:
502, Številka:
4
Journal Article
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ABSTRACT
We test the hypothesis that environments play a key role in enabling the growth of enormous radio structures spanning more than 700 kpc, an extreme population of radio galaxies called giant ...radio galaxies (GRGs). To achieve this, we explore (1) the relationships between the occurrence of GRGs and the surface number density of surrounding galaxies, including satellite galaxies and galaxies from neighbouring haloes, and (2) the GRG locations towards large-scale structures. The analysis is done by making use of a homogeneous sample of 110 GRGs detected from the LOFAR Two-metre Sky Survey in combination with photometric galaxies from the DESI Legacy Imaging Surveys and a large-scale filament catalogue from the Sloan Digital Sky Survey. Our results show that the properties of galaxies around GRGs are similar with that around the two control samples, consisting of galaxies with optical colours and luminosity matched to the properties of the GRG host galaxies. Additionally, the properties of surrounding galaxies depend on neither their relative positions to the radio jet/lobe structures nor the sizes of GRGs. We also find that the locations of GRGs and the control samples with respect to the nearby large-scale structures are consistent with each other. These results demonstrate that there is no correlation between the GRG properties and their environments traced by stars, indicating that external galaxy environments are not the primary cause of the large sizes of the radio structures. Finally, regarding radio feedback, we show that the fraction of blue satellites does not correlate with the GRG properties, suggesting that the current epoch of radio jets has minimal influence on the nature of their surrounding galaxies.
ABSTRACT
We conduct a comprehensive and statistical study of the luminosity functions (LFs) for satellite galaxies, by counting photometric galaxies from HSC, DECaLS, and SDSS around isolated central ...galaxies (ICGs) and paired galaxies from the SDSS/DR7 spectroscopic sample. Results of different surveys show very good agreement. The satellite LFs can be measured down to MV ∼ −10, and for central primary galaxies as small as 8.5 < log10M*/M⊙ < 9.2 and 9.2 < log10M*/M⊙ < 9.9, which implies there are on average 3–8 satellites with MV < −10 around LMC-mass ICGs. The bright end cutoff of satellite LFs and the satellite abundance are both sensitive to the magnitude gap between the primary and its companions, indicating galaxy systems with larger magnitude gaps are on average hosted by less massive dark matter haloes. By selecting primaries with stellar mass similar to our Milky Way (MW), we discovered that (i) the averaged satellite LFs of ICGs with different magnitude gaps to their companions and of galaxy pairs with different colour or colour combinations all show steeper slopes than the MW satellite LF; (ii) there are on average more satellites with −15 < MV < −10 than those in our MW; (iii) there are on average 1.5 to 2.5 satellites with MV < −16 around ICGs, consistent with our MW; (iv) even after accounting for the large scatter predicted by numerical simulations, the MW satellite LF is uncommon at MV > −12. Hence, the MW and its satellite system are statistically atypical of our sample of MW-mass systems. In consequence, our MW is not a good representative of other MW-mass galaxies. Strong cosmological implications based on only MW satellites await additional discoveries of fainter satellites in extra-galactic systems. Interestingly, the MW satellite LF is typical among other MW-mass systems within 40 Mpc in the local Universe, perhaps implying the Local Volume is an underdense region.
ABSTRACT
We study the properties of magnetic fields in the circumgalactic medium (CGM) of z < 1 galaxies by correlating Faraday rotation measures (RMs) of ∼1000 high-redshift radio sources with the ...foreground galaxy number density estimated from the DESI Legacy Imaging Surveys. This method enables us to extract signals of RMs contributed by intervening gas around multiple galaxies. Our results show that there is no detectable correlation between the distribution of RMs and the number of foreground galaxies, contrary to several previous results. Utilizing the non-detection signals, we estimate 3σ upper limits to the RMs from the CGM of $\sim \!20 \rm \ rad\, m^{-2}$ within 50 kpc and $\sim \!10 \rm \ rad \, m^{-2}$ at separations of 100 kpc. By adopting a column density distribution of ionized gas obtained from absorption-line measurements, we further estimate the strengths of coherent magnetic fields parallel to the line of sight of $\lt \rm 2 \ \mu G$ in the CGM. We show that the estimated upper limits of RMs and magnetic field strengths are sufficient to constrain outputs of recent galaxy magnetohydrodynamic simulations. Finally, we discuss possible causes for the inconsistency between our results and previous works.
This study investigates the association between exposure to urate-lowering drugs (ULDs) and progression and recovery from chronic kidney disease (CKD).
We identified 5860 incident gout patients at ...Chang Gung Memorial Hospital from 2012 to 2015. Propensity score (PS)-weighted Cox proportional hazards model was used to estimate hazard ratios (HRs) for CKD progression and improvement. A separate analysis was conducted to assess the HR for CKD progression and CKD recovery among those with worsening CKD.
The incidence of CKD progression among allopurinol, febuxostat and uricosuric agent users were 1.98, 1.88 and 1.64 per 1000 person-days. Compared with allopurinol users, the PS-weighted HR (95% confidence intervals CIs) was 1.77 (0.85-1.76) for febuxostat users and 1.37 (0.71-1.37) for uricosuric agent users for CKD progression and 1.43 (1.26-1.62) for febuxostat users and 1.00 (0.88-1.14) for uricosuric agent users for CKD improvement. Compared to allopurinol users, the HRs for CKD progression were 1.14 (0.80-1.66) for febuxostat users and 0.92 (0.67-1.31) for uricosuric agent users. Among 741 patients who had CKD progression, the incidence of CKD recovery was 1.33, 6.21 and 3.53 per 1000 person-days for allopurinol, febuxostat and uricosuric agent users. The HRs (95% CIs) for recovery in febuxostat and uricosuric agent users were 2.17 (1.40-3.47) and 1.80 (1.20-2.83) compared to allopurinol users.
CKD progression and recovery are common in gout patients using ULDs. Febuxostat and benzbromarone were associated with a similar risk of CKD progression with allopurinol, which has a poorer recovery compared with other ULDs.
Quantifying the relative strength of isolating barriers is a major focus of research on plant speciation. Contrasting life histories and mating systems have the potential to limit gene exchange ...between closely related populations growing in sympatry. However, few studies have quantified reproductive isolating barriers between conspecific annual and perennial populations and their contributions to total reproductive isolation (RI). Incarvillea sinensis Lam. (Bignoniaceae) is an insect‐pollinated herb with largely allopatric annual and perennial populations that differ in mating systems. The perennial populations are primarily outcrossing whereas annual populations are predominantly selfing. At a rare sympatric site in northern China we estimated prezygotic and postzygotic barriers to gene exchange between annual and perennial plants and found complete RI between the two life histories. Annuals exhibited significantly higher ecogeographic isolation than perennials whereas perennials experienced more isolation through pollen–pistil interactions than annuals. Crosses between annuals and perennials demonstrated that postzygotic barriers influencing fruit and seed formation, F1 germination and survival were negligible for annuals but played a small role for perennials. However, F1 hybrids of crosses between annuals and perennials produced no pollen and their ovules were largely sterile. Our study provides insight into the relative importance of prezygotic and postzygotic isolating barriers between closely related annual and perennial populations of I. sinensis and some of these barriers could have been involved with speciation. Annuals and perennials of I. sinensis represent two biological species and thus deserve to be recognized as distinct taxonomic species.
Our study provides insight into the relative importance of prezygotic and postzygotic isolating barriers in closely related annual and perennial populations of Incarvillea sinensis Lam. Annuals and perennials of I. sinensis represent two distinct biological species with implications for future taxonomic delimitation of this taxon.
The halo assembly bias, a phenomenon referring to dependencies of the large-scale bias of a dark matter halo other than its mass, is a fundamental property of the standard cosmological model. First ...discovered in 2005 from the Millennium Run simulation, it has been proven very difficult to be detected observationally, with only a few convincing claims of detection so far. The main obstacle lies in finding an accurate proxy of the halo formation time. In this study, by utilizing a constrained simulation that can faithfully reproduce the observed structures larger than 2 Mpc in the local universe, for a sample of 634 massive clusters at
z
≤ 0.12, we found their counterpart halos in the simulation and used the mass growth history of the matched halos to estimate the formation time of the observed clusters. This allowed us to construct a pair of early- and late-forming clusters, with a similar mass as measured via weak gravitational lensing, and large-scale biases differing at the ≈3
σ
level, suggestive of the signature of assembly bias, which is further corroborated by the properties of cluster galaxies, including the brightest cluster galaxy and the spatial distribution and number of member galaxies. Our study paves a way to further detect assembly bias based on cluster samples constructed purely on observed quantities.
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