Sub-percentage measure of distances to redshift of 0.1 by a new cosmic ruler

Distance-redshift diagrams probe expansion history of the Universe. We show that the stellar mass-binding energy (massE) relation of galaxies proposed in our previous study offers a new distance ruler at cosmic scales. By using elliptical galaxies in the main galaxy sample of the Sloan Digital Sky Survey Data Release 7, we construct a distance-redshift diagram over the redshift range from 0.05 to 0.2 with the massE ruler. The best-fit dark energy density is 0.675+-0.079 for flat Lambda-CDM, consistent with those by other probes. At the median redshift of 0.11, the median distance is estimated to have a fractional error of 0.34%, much lower than those by supernova (SN) Ia and baryonic acoustic oscillation (BAO) and even exceeding their future capability at this redshift. The above low-z measurement is useful for probing dark energy that dominates at the late Universe. For a flat dark energy equation of state model (flat wCDM), the massE alone constrains w to an error that is only a factor of 2.2, 1.7 and 1.3 times larger than those by BAO, SN Ia, and cosmic microwave background (CMB), respectively.Comment: 8 pages, 5 figures, MNRAS in press. The cosmoSIS modules for the massE ruler is at https://astronomy.nju.edu.cn/DFS//file/2022/07/02/20220702161632756vbde28.zi

Co-delivery of doxorubicin and oleanolic acid by triple-sensitive nanocomposite based on chitosan for effective promoting tumor apoptosis

Nanocomposites as “stevedores” for co-delivery of multidrugs hold great promise in addressing the drawbacks of traditional cancer chemotherapy. In this work, our strategy presents a new avenue for the stepwise release of two co-delivered agents into the tumor cells. The hybrid nanocomposite consists of a pH-responsive chitosan (CS), a thermosensitive poly(N-vinylcaprolactam) (PNVCL) and a functionalized cell-penetrating peptide (H6R6). Doxorubicin (DOX) and oleanolic acid (OA) are loaded into the nanocomposite (H6R6-CS-g-PNVCL). The system displayed a suitable size (∼190 nm), a high DOX loading (13.2%) and OA loading efficiency (7.3%). The tumor microenvironment triggered the nanocomposite to be selectively retained in tumor cells, then releasing the drugs. Both in vitro and in vivo studies showed a significant enhancement in antitumor activity of the co-delivered system in comparison to mono-delivery. This approach which relies on redox, pH and temperature effects utilizing co-delivery nanosystems may be beneficial for future applications in cancer chemotherapy

Lensing by a singular isothermal sphere and a black hole

Most galaxies host central supermassive black holes. As two galaxies merge, the black holes also merge. The final single black hole may suffer a kick due to asymmetric gravitational radiation and may not be at the centre of the galaxy; off-centre black holes may also be produced by other means such as sustained acceleration due to asymmetric jet power. We model the main galaxy as a singular isothermal sphere and the black hole as an off-centre point lens, and study the critical curves and caustics using complex notation. We identify the critical parameters that govern the transitions in the topology of critical curves, caustics and pseudo-caustics, and find the number of images can be two, three, four and five. We show examples of image configurations, including cases where three highly de-magnified images are found close to the centre. The perturbation on the image magnification due to the black hole scales linearly with its mass in the off-centre case, and quadratically when the black hole is at the centre. Such images are difficult to observe unless high-contrast and high-resolution imaging facilities (e.g., the Square Kilometer Array in the radio) become available.Comment: 10 pages, 10 figures, MNRAS, in pres

Chandra X-ray Analysis of Galaxy Cluster A168

We present Chandra X-ray observations of galaxy cluster A168 (z=0.045). Two X-ray peaks with a projected distance of 676 kpc are found to be located close to two dominant galaxies, respectively. Both peaks are significantly offset from the peak of the number density distribution of galaxies. This suggests that A168 consists of two subclusters, a northern subcluster (A168N) and a southern subcluster (A168S). Further X-ray imaging analysis reveals that (1) the X-ray isophotes surrounding the two X-ray peaks are heavily distorted, (2) an elongated and ontinuous filament connects the two X-ray peaks. These suggest that strong interactions have occurred between the two subclusters. Spectral analysis shows that A168 has a mean temperature of 2.53 +/- 0.09 keV and a mean metallicity of 0.31 +/- 0.04 Z_{solar}. The metallicity is roughly a constant across the cluster but the temperature shows some systematic variations. Most X-ray, optical and radio properties of A168 are consistent with it being an off-axis merger several Gyrs after a core passage, although detailed numerical simulations are required to see whether the observed properties, in particular the significant offset between the optical and X-ray centers, can be reproduced in such a scenario.Comment: 17 pages, 7 figures, to be published in ApJ. When this paper was being refereed, Eric Hallman and Maxim Markevitch carried out a similar work (astro-ph/0406322); our results are in broad agreemen

Spatially resolved Spectro-photometry of M81: Age, Metallicity and Reddening Maps

In this paper, we present a multi-color photometric study of the nearby spiral galaxy M81, using images obtained with the Beijing Astronomical Observatory 60/90 cm Schmidt Telescope in 13 intermediate-band filters from 3800 to 10000{\AA}. The observations cover the whole area of M81 with a total integration of 51 hours from February 1995 to February 1997. This provides a multi-color map of M81 in pixels of 1\arcsec.7 \times 1\arcsec.7. Using theoretical stellar population synthesis models, we demonstrate that some BATC colors and color indices can be used to disentangle the age and metallicity effect. We compare in detail the observed properties of M81 with the predictions from population synthesis models and quantify the relative chemical abundance, age and reddening distributions for different components of M81. We find that the metallicity of M81 is about $Z=0.03$ with no significant difference over the whole galaxy. In contrast, an age gradient is found between stellar populations of the central regions and of the bulge and disk regions of M81: the stellar population in its central regions is older than 8 Gyr while the disk stars are considerably younger, $\sim 2$ Gyr. We also give the reddening distribution in M81. Some dust lanes are found in the galaxy bulge region and the reddening in the outer disk is higher than that in the central regions.Comment: Accepted for publication in AJ (May 2000 issue). 27 pages including 6 figures. Uses AASTeX aasms4 styl

Internal kinematics of groups of galaxies in the Sloan Digital Sky Survey data release 7

We present measurements of the velocity dispersion profile (VDP) for galaxy groups in the final data release of the Sloan Digital Sky Survey (SDSS). For groups of given mass we estimate the redshift-space cross-correlation function (CCF) with respect to a reference galaxy sample, xi(r_p, pi), the projected CCF, w_p(r_p), and the real-space CCF, xi(r). The VDP is then extracted from the redshift distortion in xi(r_p, pi), by comparing xi(r_p, pi) with xi(r). We find that the velocity dispersion (VD) within virial radius (R_200) shows a roughly flat profile, with a slight increase at radii below ~0.3 R_200 for high mass systems. The average VD within the virial radius, sigma_v, is a strongly increasing function of central galaxy mass. We apply the same methodology to N-body simulations with the concordance Lambda cold dark matter cosmology but different values of the density fluctuation parameter sigma_8, and we compare the results to the SDSS results. We show that the sigma_v-M_* relation from the data provides stringent constraints on both sigma_8 and sigma_ms, the dispersion in log M_* of central galaxies at fixed halo mass. Our best-fitting model suggests sigma_8 = 0.86 +/- 0.03 and sigma_ms = 0.16 +/- 0.03. The slightly higher value of sigma_8 compared to the WMAP7 result might be due to a smaller matter density parameter assumed in our simulations. Our VD measurements also provide a direct measure of the dark matter halo mass for central galaxies of different luminosities and masses, in good agreement with the results obtained by Mandelbaum et al. (2006) from stacking the gravitational lensing signals of the SDSS galaxies.Comment: 17 pages, 10 figures, 1 table, accepted for publication in ApJ, text slightly changed, abstract substantially shortened, two new panels added to Figs. 2 and 3 showing w_p and VDP as functions of r_p/R_200 instead of r_

Spitzer + VLTI-GRAVITY Measure the Lens Mass of a Nearby Microlensing Event

We report the lens mass and distance measurements of the nearby microlensing event TCP J05074264+2447555 (Kojima-1). We measure the microlens parallax vector π_E using Spitzer and ground-based light curves with constraints on the direction of lens-source relative proper motion derived from Very Large Telescope Interferometer (VLTI) GRAVITY observations. Combining this π_E determination with the angular Einstein radius θ_E measured by VLTI-GRAVITY observations, we find that the lens is a star with mass M_L = 0.495±0.063 M⊙ at a distance D_L = 429 ± 21 pc. We find that the blended light basically all comes from the lens. The lens-source proper motion is Μ_(rel,hel) = 26.55±0.36 mas yr⁻¹, so with currently available adaptive-optics instruments, the lens and source can be resolved in 2021. This is the first microlensing event whose lens mass is unambiguously measured by interferometry + satellite-parallax observations, which opens a new window for mass measurements of isolated objects such as stellar-mass black holes

Spitzer + VLTI-GRAVITY Measure the Lens Mass of a Nearby Microlensing Event

We report the lens mass and distance measurements of the nearby microlensing event TCP J05074264+2447555. We measure the microlens parallax vector ${\pi}_{\rm E}$ using Spitzer and ground-based light curves with constraints on the direction of lens-source relative proper motion derived from Very Large Telescope Interferometer (VLTI) GRAVITY observations. Combining this ${\pi}_{\rm E}$ determination with the angular Einstein radius $\theta_{\rm E}$ measured by VLTI GRAVITY observations, we find that the lens is a star with mass $M_{\rm L} = 0.495 \pm 0.063~M_{\odot}$ at a distance $D_{\rm L} = 429 \pm 21~{\rm pc}$. We find that the blended light basically all comes from the lens. The lens-source proper motion is $\mu_{\rm rel,hel} = 26.55 \pm 0.36~{\rm mas\,yr^{-1}}$, so with currently available adaptive-optics (AO) instruments, the lens and source can be resolved in 2021. This is the first microlensing event whose lens mass is unambiguously measured by interferometry + satellite parallax observations, which opens a new window for mass measurements of isolated objects such as stellar-mass black holes.Comment: 3 Figures and 6 Tables Submitted to AAS Journa

Effects of supermassive binary black holes on gravitational lenses

Recent observations indicate that many if not all galaxies host massive central black holes (BHs). In this paper we explore the influence of supermassive binary black holes (SMBBHs) on their actions as gravitational lenses. When lenses are modelled as singular isothermal ellipsoids, binary black holes change the critical curves and caustics differently as a function of distance. Each black hole can in principle create at least one additional image, which, if observed, provides evidence of black holes. By studying how SMBBHs affect the cumulative distribution of magnification for images created by black holes, we find that the cross section for at least one such additional image to have a magnification larger than $10^{-5}$ is comparable to the cross section for producing multiple-images in singular isothermal lenses. Such additional images may be detectable with high-resolution and large dynamic range maps of multiply-imaged systems from future facilities, such as the SKA. The probability of detecting at least one image (two images) with magnification above $10^{-3}$ is \sim 0.2 \fBH (\sim 0.05 \fBH) in a multiply-imaged lens system, where \fBH is the fraction of galaxies housing binary black holes. We also study the effects of SMBBHs on the core images when galaxies have shallower central density profiles (modelled as non-singular isothermal ellipsoids). We find that the cross section of the usually faint core images is further suppressed by SMBBHs. Thus their presence should also be taken into account when one constrains the core radius from the lack of central images in gravitational lenses.Comment: 9 pages, 5 figures, accepted for publication in MNRA