Abstract
We present an optically-selected cluster catalog from the Hyper Suprime-Cam (HSC) Subaru Strategic Program. The HSC images are sufficiently deep to detect cluster member galaxies down to ...M* ∼ 1010.2 M⊙ even at z ∼ 1, allowing a reliable cluster detection at such high redshifts. We apply the CAMIRA algorithm to the HSC Wide S16A dataset covering ∼232 deg2 to construct a catalog of 1921 clusters at redshift 0.1 < z < 1.1 and richness ${\skew7\hat{N}}_{\rm mem}>15$ that roughly corresponds to M200m ≳ 1014 h−1 M⊙. We confirm good cluster photometric redshift performance, with the bias and the scatter in Δz/(1 + z) being better than 0.005 and 0.01, respectively, over most of the redshift range. We compare our cluster catalog with large X-ray cluster catalogs from the XXL and XMM-LSS (the XMM Large Scale Structure) surveys and find good correlation between richness and X-ray properties.We also study the mis-centering effect from the distribution of offsets between optical and X-ray cluster centers. We confirm the high (>0.9) completeness and purity for high-mass clusters by analyzing mock galaxy catalogs.
ABSTRACT We report the discovery of a new ultra-faint dwarf satellite companion of the Milky Way (MW) based on the early survey data from the Hyper Suprime-Cam Subaru Strategic Program. This new ...satellite, Virgo I, which is located in the constellation of Virgo, has been identified as a statistically significant (5.5 ) spatial overdensity of star-like objects with a well-defined main sequence and red giant branch in the color-magnitude diagram. The significance of this overdensity increases to 10.8 when the relevant isochrone filter is adopted for the search. Based on the distribution of the stars around the likely main-sequence turnoff at r ∼ 24 mag, the distance to Virgo I is estimated as 87 kpc, and its most likely absolute magnitude calculated from a Monte Carlo analysis is MV = −0.8 0.9 mag. This stellar system has an extended spatial distribution with a half-light radius of pc, which clearly distinguishes it from a globular cluster with comparable luminosity. Thus, Virgo I is one of the faintest dwarf satellites known and is located beyond the reach of the Sloan Digital Sky Survey. This demonstrates the power of this survey program to identify very faint dwarf satellites. This discovery of Virgo I is based only on about 100 square degrees of data, thus a large number of faint dwarf satellites are likely to exist in the outer halo of the MW.
Thirteen explosion sites of Type II-P and II-L supernovae (SNe) in nearby galaxies have been observed using integral field spectroscopy, enabling both spatial and spectral study of the explosion ...sites. We used the properties of the parent stellar population of the coeval SN progenitor star to derive its metallicity and initial mass. The spectrum of the parent stellar population yields estimates of metallicity via the strong-line method and age via a comparison with simple stellar population models. These metallicity and age parameters are adopted for the progenitor star. Age, or lifetime of the star, was used to derive the initial (zero-age main sequence) mass of the star using comparisons with stellar evolution models. With this technique, we were able to determine the metallicities and initial masses of the SN progenitors in our sample. Our results indicate that some Type II SN progenitors may have been stars with masses comparable to those of SN Ib/c progenitors.
Context. Deuterated interstellar molecules frequently have abundances relative to their main isotopologues much higher than the overall elemental D-to-H ratio in the cold dense interstellar medium. H ...3+ $_3^+$3+ and its isotopologues play a key role in the deuterium fractionation; however, the abundances of these isotopologues have not been measured empirically with respect to H 3+ $_3^+$3+ to date. Aims. Our aim was to constrain the relative abundances of H2D+ and D 3+ $_3^+$3+ in the cold outer envelope of the hot core CRL 2136 IRS 1. Methods. We carried out three observations targeting H 3+ $_3^+$3+ and its isotopologues using the spectrographs CRIRES at the VLT, iSHELL at IRTF, and EXES on board SOFIA. In addition, the CO overtone band at 2.3 μm was observed by iSHELL to characterize the gas on the line of sight. Results. The H 3+ $_3^+$3+ ion was detected toward CRL 2136 IRS 1 as in previous observations. Spectroscopy of lines of H2D+ and D 3+ $_3^+$3+ resulted in non-detections. The 3σ upper limits of N(H2D+)/N(H3+) $N(\textrm{H}_2\textrm{D}^+)/N({\textrm{H}_3^+})$N(H2D+)/N(H3+) and N(D3+)/N(H3+) $N({\textrm{D}_3^+})/N({\textrm{H}_3^+})$N(D3+)/N(H3+) are 0.24 and 0.13, respectively. The population diagram for CO is reproduced by two components of warm gas with the temperatures 58 and 530 K, assuming a local thermodynamic equilibrium (LTE) distribution of the rotational levels. Cold gas (<20 K) makes only a minor contribution to the CO molecular column toward CRL 2136 IRS 1. Conclusions. The critical conditions for deuterium fractionation in a dense cloud are low temperature and CO depletion. Given the revised cloud properties, it is no surprise that H 3+ $_3^+$3+ isotopologues are not detected toward CRL 2136 IRS 1. The result is consistent with our current understanding of how deuterium fractionation proceeds.
Cassiopeia A Supernova Was of Type IIb Krause, Oliver; Birkmann, Stephan M; Usuda, Tomonori ...
Science (American Association for the Advancement of Science),
05/2008, Letnik:
320, Številka:
5880
Journal Article
Recenzirano
Odprti dostop
Cassiopeia A is the youngest supernova remnant known in the Milky Way and a unique laboratory for supernova physics. We present an optical spectrum of the Cassiopeia A supernova near maximum ...brightness, obtained from observations of a scattered light echo more than three centuries after the direct light of the explosion swept past Earth. The spectrum shows that Cassiopeia A was a type IIb supernova and originated from the collapse of the helium core of a red supergiant that had lost most of its hydrogen envelope before exploding. Our finding concludes a long-standing debate on the Cassiopeia A progenitor and provides new insight into supernova physics by linking the properties of the explosion to the wealth of knowledge about its remnant.
Abstract
Redshifts of an astronomical body measured at multiple epochs (e.g., separated by 10 yr) are different due to the cosmic expansion. This so-called Sandage–Loeb test offers a direct ...measurement of the expansion rate of the Universe. However, acceleration in the motion of the Solar System with respect to the cosmic microwave background also changes redshifts measured at multiple epochs. If not accounted for, it yields a biased cosmological inference. To address this, we calculate the acceleration of the Solar System with respect to the Local Group of galaxies to quantify the change in the measured redshift due to local motion. Our study is motivated by the recent determination of the mass of the Large Magellanic Cloud (LMC), which indicates a significant fraction of the Milky Way mass. We find that the acceleration towards the Galactic Center dominates, which gives a redshift change of 7 cm s−1 in 10 yr, while the accelerations due to the LMC and M 31 cannot be ignored, depending on lines of sight. We create all-sky maps of the expected change in redshift and the corresponding uncertainty, which can be used to correct for this effect.
ABSTRACT We present measurements of the clustering properties of a sample of infrared (IR) bright dust-obscured galaxies (DOGs). Combining 125 deg2 of wide and deep optical images obtained with the ...Hyper Suprime-Cam on the Subaru Telescope and all-sky mid-IR images taken with Wide-Field Infrared Survey Explorer, we have discovered 4367 IR-bright DOGs with and flux density at 22 mJy. We calculate the angular autocorrelation function (ACF) for a uniform subsample of 1411 DOGs with 3.0 mJy < flux (22 ) < 5.0 mJy and < 24.0. The ACF of our DOG subsample is well-fit with a single power law, = (0.010 0.003) , where θ is in degrees. The correlation amplitude of IR-bright DOGs is larger than that of IR-faint DOGs, which reflects a flux dependence of the DOG clustering, as suggested by Brodwin et al. We assume that the redshift distribution for our DOG sample is Gaussian, and consider two cases: (1) the redshift distribution is the same as IR-faint DOGs with flux at 22 < 1.0 mJy, mean and sigma z = 1.99 0.45, and (2) z = 1.19 0.30, as inferred from their photometric redshifts. The inferred correlation length of IR-bright DOGs is r0 = 12.0 2.0 and 10.3 1.7 Mpc, respectively. IR-bright DOGs reside in massive dark matter halos with a mass of and in the two cases, respectively.
Abstract
We report the discovery of a diffuse stellar cloud with an angular extent ≳30″, which we term “Sumo Puff”, in data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). While we do ...not have a redshift for this object, it is in close angular proximity to a post-merger galaxy at redshift z = 0.0431 and is projected within a few virial radii (assuming similar redshifts) of two other ∼L⋆ galaxies, which we use to bracket a potential redshift range of 0.0055 < z < 0.0431. The object’s light distribution is flat, as characterized by a low Sérsic index (n ∼ 0.3). It has a low central g-band surface brightness of ∼26.4 mag arcsec−2, large effective radius of ∼13″ (∼11 kpc at z = 0.0431 and ∼1.5 kpc at z = 0.0055), and an elongated morphology (b/a ∼ 0.4). Its red color (g − i ∼ 1) is consistent with a passively evolving stellar population and similar to the nearby post-merger galaxy, and we may see tidal material connecting Sumo Puff with this galaxy. We offer two possible interpretations for the nature of this object: (1) it is an extreme, galaxy-sized tidal feature associated with a recent merger event, or (2) it is a foreground dwarf galaxy with properties consistent with a quenched, disturbed, ultra-diffuse galaxy. We present a qualitative comparison with simulations that demonstrates the feasibility of forming a structure similar to this object in a merger event. Follow-up spectroscopy and/or deeper imaging to confirm the presence of the bridge of tidal material will be necessary to reveal the true nature of this object.
ABSTRACT
We describe a weak lensing view of the downsizing of star-forming galaxies based on cross-correlating a weak lensing (
κ
) map with a predicted map constructed from a redshift survey. ...Moderately deep and high-resolution images with Subaru/Hyper Suprime-Cam covering the
DLS F2 field provide a
κ
map with 1 arcmin resolution. A dense complete redshift survey of the F2 field including 12,705 galaxies with
is the basis for construction of the predicted map. The zero-lag cross-correlation between the
κ
and predicted maps is significant at the 30
σ
level. The width of the cross-correlation peak is comparable to the angular scale of rich clusters at
, the median depth of the redshift survey. Slices of the predicted map in
redshift bins enable exploration of the impact of structure as a function of redshift. The zero-lag normalized cross-correlation has significant local maxima at redshifts coinciding with known massive X-ray clusters. Even in slices where there are no known massive clusters, there is a significant signal in the cross-correlation originating from lower mass groups that trace the large-scale of the universe. Spectroscopic
measurements enable division of the sample into star-forming and quiescent populations. In regions surrounding massive clusters of galaxies, the significance of the cross-correlation with maps based on star-forming galaxies increases with redshift from 5
σ
at
z
= 0.3 to 7
σ
at
the fractional contribution of the star-forming population to the total cross-correlation signal also increases with redshift. This weak lensing view is consistent with the downsizing picture of galaxy evolution established from other independent studies.
Abstract
We have measured the clustering of galaxies around active galactic nuclei (AGNs) for which single-epoch virial masses of the super-massive black hole (SMBH) are available to investigate the ...relation between the large-scale environment of AGNs and the evolution of SMBHs. The AGN samples used in this work were derived from the Sloan Digital Sky Survey (SDSS) observations and the galaxy samples were from the 240 deg2 S15b data of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). The investigated redshift range is 0.6–3.0, and the masses of the SMBHs lie in the range 107.5–1010 M⊙. The absolute magnitude of the galaxy samples reaches to Mλ310 ∼ −18 at rest-frame wavelength 310 nm for the low-redshift end of the samples. More than 70% of the galaxies in the analysis are blue. We found a significant dependence of the cross-correlation length on redshift, which primarily reflects the brightness-dependence of the galaxy clustering. At the lowest redshifts the cross-correlation length increases from 7 h−1 Mpc around Mλ310 = −19 mag to >10 h−1 Mpc beyond Mλ310 = −20 mag. No significant dependence of the cross-correlation length on BH mass was found for whole galaxy samples dominated by blue galaxies, while there was an indication of BH mass dependence in the cross-correlation with red galaxies. These results provides a picture of the environment of AGNs studied in this paper being enriched with blue star-forming galaxies, and a fraction of the galaxies are evolving into red galaxies along with the evolution of SMBHs in that system.
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