ABSTRACT
We present an overview of the Carnegie-Chicago Hubble Program, an ongoing program to obtain a 3% measurement of the Hubble constant (
H
0
) using alternative methods to the traditional ...Cepheid distance scale. We aim to establish a completely independent route to
H
0
using RR Lyrae variables, the tip of the red giant branch (TRGB), and Type Ia supernovae (SNe Ia). This alternative distance ladder can be applied to galaxies of any Hubble type, of any inclination, and, using old stars in low-density environments, is robust to the degenerate effects of metallicity and interstellar extinction. Given the relatively small number of SNe Ia host galaxies with independently measured distances, these properties provide a great systematic advantage in the measurement of
H
0
via the distance ladder. Initially, the accuracy of our value of
H
0
will be set by the five Galactic RR Lyrae calibrators with
Hubble Space Telescope
Fine-Guidance Sensor parallaxes. With
Gaia
, both the RR Lyrae zero-point and TRGB method will be independently calibrated, the former with at least an order of magnitude more calibrators and the latter directly through parallax measurement of tip red giants. As the first end-to-end “distance ladder” completely independent of both Cepheid variables and the Large Magellanic Cloud, this path to
H
0
will allow for the high-precision comparison at each rung of the traditional distance ladder that is necessary to understand tensions between this and other routes to
H
0
.
M74 (NGC 628) is a famous face-on spiral galaxy, hosting three core-collapse supernovae (SNe): SN Ic 2002ap, SN II-P 2003gd, and SN II-P 2013ej. However, its distance is not well known. We present a ...distance estimation for this galaxy based on the Tip of the Red Giant Branch (TRGB) method. We obtain photometry of the resolved stars in die arm-free region of M74 from F555W and F814W images in the Hubble Space Telescope archive. The color-magnitude diagram of the resolved stars shows a dominant red giant branch (RGB) as well as blue main sequence stars, red helium burning stars, and asymptotic giant branch stars. The I-band luminosity function of the RGB stars shows the TRGB to be at I sub(TRGB) = 26.13 + or - 0.03 mag, and I sub(RGB) = 25.97 + or - 0.03. From this, we derive the distance modulus to M74 to be 30.04 + or - 0.04 (random) + or - 0.12 (systematic) (corresponding to a linear distance of 10.19 + or - 0.14 + or - 0.56 Mpc). With this distance estimate, we calibrate the standardized candle method for SNe II-P. From the absolute magnitudes of SN 2003gd, we derive a value of the Hubble constant, Ho sub(0) = 72 + or - 6 (random) + or - 7 (systematic) km s super(-1) Mpc super(-1). It is similar to recent estimates based on the luminosity calibration of Type Ia supernovae.
Abstract
The Carnegie–Chicago Hubble Program (CCHP) seeks to anchor the distance scale of Type Ia supernovae via the Tip of the Red Giant Branch (TRGB) method. Based on deep
Hubble Space Telescope
...ACS/WFC imaging, we present an analysis of the TRGB for the metal-poor halo of NGC 1365, a giant spiral galaxy in the Fornax cluster that was host to the Type Ia supernova SN 2012fr. We have measured the extinction-corrected TRGB magnitude of NGC 1365 to be
F
814
W
= 27.34 ± 0.03
stat
± 0.04
sys
mag. In advance of future direct calibration by
Gaia
, we adopt a provisional
I
-band TRGB luminosity set at the Large Magellanic Cloud and find a true distance modulus
μ
0
= 31.29 ± 0.04
stat
± 0.06
sys
mag or
D
= 18.1 ± 0.3
stat
± 0.5
sys
Mpc. This measurement is in excellent agreement with recent Cepheid-based distances to NGC 1365 and reveals no significant difference in the distances derived from stars of Populations I and II for this galaxy. We revisit the error budget for the CCHP path to the Hubble constant based on the analysis presented here, i.e., that for one of the most distant Type Ia supernova hosts within our Program, and find that a 2.5% measurement is feasible with the current sample of galaxies and TRGB absolute calibration.
ABSTRACT We present the rest-frame optical spectral properties of 155 luminous quasars at 3.3 < z < 6.4 taken with the AKARI space telescope, including the first detection of the H emission line as ...far out as z ∼ 6. We extend the scaling relation between the rest-frame optical continuum and the line luminosity of active galactic nuclei (AGNs) to the high-luminosity, high-redshift regime that has rarely been probed before. Remarkably, we find that a single log-linear relation can be applied to the 5100 and H AGN luminosities over a wide range of luminosity (1042 < < 1047 ergs s−1) or redshift (0 < z < 6), suggesting that the physical mechanism governing this relation is unchanged from z = 0 to 6, over five decades in luminosity. Similar scaling relations are found between the optical and the UV continuum luminosities or line widths. Applying the scaling relations to the Hβ black hole (BH) mass ( ) estimator of local AGNs, we derive the estimators based on the H , Mg ii, and C iv lines, finding that the UV-line-based masses are overall consistent with the Balmer-line-based, but with a large intrinsic scatter of 0.40 dex for the C iv estimates. Our 43 estimates from H confirm the existence of BHs as massive as ∼ out to z ∼ 5 and provide a secure footing for previous results from Mg ii-line-based studies that a rapid growth has occurred in the early universe.
M85 is a peculiar S0 galaxy in Virgo and a well-known merger remnant. We present the first spectroscopic study of globular clusters (GCs) in M85. We obtain spectra for 21 GC candidates and the ...nucleus of M85 using the Gemini Multi-Object Spectrograph on the Gemini North 8.1 m telescope. From their radial velocities, 20 of the GCs are found to be members of M85. We find a strong rotation signal of the M85 GC system with a rotation amplitude of 235 km s−1. The rotation axis of the GC system has a position angle of about 161°, which is 51 5 larger than that of the stellar light. The rotation-corrected radial velocity dispersion of the GC system is estimated to be km s−1. The rotation parameter of the GC system is derived to be , which is one of the largest among known early-type galaxies. The ages and metallicities of the GCs, which show the same trend as the results based on Lick indices, are derived from full spectrum fitting (ULySS). About half of the GCs are an intermediate-age population whose mean age is ∼3.7 1.9 Gyr, having a mean Fe/H value of −0.26. The other half are old and metal-poor. These results suggest that M85 experienced a wet merging event about 4 Gyr ago, forming a significant population of star clusters. The strong rotational feature of the GC system can be explained by an off-center major merging.
Abstract
The Carnegie–Chicago Hubble Program (CCHP) is recalibrating the extragalactic SN Ia distance scale using exclusively Population II stars. This effort focuses on the Tip of the Red Giant ...Branch (TRGB) method, whose systematics are entirely independent of the Population I Cepheid-based determinations that have long served as calibrators for the SN Ia distance scale. We present deep
Hubble Space Telescope
imaging of the low surface density and low line-of-sight reddening halos of two galaxies, NGC 1448 and NGC 1316, each of which have been hosts to recent SN Ia events. Provisionally anchoring the TRGB zero-point to the geometric distance to the Large Magellanic Cloud derived from detached eclipsing binaries, we measure extinction-corrected distance moduli of
mag for NGC 1448 and
mag for NGC 1316, respectively, giving metric distances of
Mpc, and
Mpc. We find agreement between our result and the available Cepheid distance for NGC 1448; for NGC 1316, where there are relatively few published distances based on direct measurements, we find that our result is consistent with the published SN Ia distances whose absolute scales are set from other locally determined methods such as Cepheids. For NGC 1448 and NGC 1316, our distances are some of the most precise (and systematically accurate) measurements with errors at 1.7 (2.8)% and 1.6 (2.7)% levels, respectively.
We report new observations of the active asteroid P/2010 A2 taken when it made its closest approach to Earth (1.06 au in 2017 January) after its first discovery in 2010. Despite a crucial role of the ...rotational period in clarifying its ejection mechanism, the rotational property of P/2010 A2 has not yet been studied due to the extreme faintness of this tiny object (∼120 m in diameter). Taking advantage of the best observing geometry since the discovery, we succeed in obtaining the rotational light curve of the largest fragment with Gemini/GMOS-N. We find that (1) the largest fragment has a double-peaked period of 11.36 0.02 hr spinning much slower than its critical spin period; (2) the largest fragment is a highly elongated object (a/b ≥ 1.94) with an effective radius of m; (3) the size distribution of the ejecta follows a broken power law (the power indices of the cumulative size distributions of the dust and fragments are 2.5 0.1 and 5.2 0.1, respectively); (4) the mass ratio of the largest fragment to the total ejecta is around 0.8; and (5) the dust cloud morphology is in agreement with the anisotropic ejection model in Kim et al. These new characteristics of the ejecta obtained in this work are favorable to the impact shattering hypothesis.
We present a study of H II regions in M51 using the Hubble Space Telescope Advanced Camera for Surveys images taken as part of the Hubble Heritage Program. We have cataloged about 19,600 H II regions ...in M51 with H Delta *a luminosity in the range of L = 1035.5-1039.0 erg s--1. The H Delta *a luminosity function of H II regions (H II LF) in M51 is well represented by a double power law with its index Delta *a = --2.25 ? 0.02 for the bright part and Delta *a = --1.42 ? 0.01 for the faint part, separated at a break point L = 1037.1 erg s--1. This break was not found in previous studies of M51 H II regions. Comparison with simulated H II LFs suggests that this break is caused by the transition of H II region ionizing sources, from low-mass clusters (with ~103 M , including several OB stars) to more massive clusters (including several tens of OB stars). The H II LFs with L < 1037.1 erg s--1are found to have different slopes for different parts in M51: the H II LF for the interarm region is steeper than those for the arm and the nuclear regions. This observed difference in H II LFs can be explained by evolutionary effects: H II regions in the interarm region are relatively older than those in the other parts of M51.
Globular clusters are usually found in galaxies, and they are excellent tracers of dark matter. Long ago it was suggested that intracluster globular clusters (IGCs) may exist that are bound to a ...galaxy cluster rather than to any single galaxy. Here we present a map showing the large-scale distribution of globular clusters over the entire Virgo cluster. It shows that IGCs are found out to 5 million light years from the Virgo center and that they are concentrated in several substructures that are much larger than galaxies. These objects might have been mostly stripped off from low-mass dwarf galaxies.
We investigate the connection between the presence of bars and active galactic nucleus (AGN) activity, using a volume-limited sample of ~9000 late-type galaxies with axis ratio b/a > 0.6 and Mr < ...-19.5 + 5 log h at low redshift (0.02 < or =, slant z < ~ 0.055), selected from Sloan Digital Sky Survey Data Release 7. We find that the bar fraction in AGN-host galaxies (42.6%) is ~2.5 times higher than in non-AGN galaxies (15.6%), and that the AGN fraction is a factor of two higher in strong-barred galaxies (34.5%) than in non-barred galaxies (15.0%). However, these trends are simply caused by the fact that AGN-host galaxies are on average more massive and redder than non-AGN galaxies because the fraction of strong-barred galaxies (f sub(SB)) increases with u - r color and stellar velocity dispersion. When u - r color and velocity dispersion (or stellar mass) are fixed, both the excess of f sub(SB) in AGN-host galaxies and the enhanced AGN fraction in strong-barred galaxies disappears. Among AGN-host galaxies we find no strong difference of the Eddington ratio distributions between barred and non-barred systems. These results indicate that AGN activity is not dominated by the presence of bars, and that AGN power is not enhanced by bars. In conclusion, we do not find clear evidence that bars trigger AGN activity.
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