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The Carnegie Supernova Project-II (CSP-II) was an NSF-funded, four-year program to obtain optical and near-infrared observations of a “Cosmology” sample of ∼100 Type Ia supernovae located in the smooth Hubble flow (0.03 ≲ z ≲ 0.10). Light curves were also obtained of a “Physics” sample composed of 90 nearby Type Ia supernovae at z ≤ 0.04 selected for near-infrared spectroscopic timeseries observations. The primary emphasis of the CSP-II is to use the combination of optical and near-infrared photometry to achieve a distance precision of better than 5%. In this paper, details of the supernova sample, the observational strategy, and the characteristics of the photometric data are provided. In a companion paper, the near-infrared spectroscopy component of the project is presented.

Polybrominated diphenyl ethers (PBDEs) are ubiquitous persistent organic pollutants (POPs) that are known neuroendocrine disrupting chemicals with adverse neurodevelopmental effects. PBDEs may act as risk factors for autism spectrum disorders (ASD), characterized by abnormal psychosocial functioning, although direct evidence is currently lacking. Using a translational exposure model, we tested the hypothesis that maternal transfer of a commercial mixture of PBDEs, DE-71, produces ASD-relevant behavioral and neurochemical deficits in female offspring. C57Bl6/N mouse dams (F0) were exposed to DE-71 via oral administration of 0 (VEH/CON), 0.1 (L-DE-71) or 0.4 (H-DE-71) mg/kg bw/d from 3 wk prior to gestation through end of lactation. Mass spectrometry analysis indicated in utero and lactational transfer of PBDEs (in ppb) to F1 female offspring brain tissue at postnatal day (PND) 15 which was reduced by PND 110. Neurobehavioral testing of social novelty preference (SNP) and social recognition memory (SRM) revealed that adult L-DE-71 F1 offspring display deficient short- and long-term SRM, in the absence of reduced sociability, and increased repetitive behavior. These effects were concomitant with reduced olfactory discrimination of social odors. Additionally, L-DE-71 exposure also altered short-term novel object recognition memory but not anxiety or depressive-like behavior. Moreover, F1 L-DE-71 displayed downregulated mRNA transcripts for oxytocin ( Oxt ) in the bed nucleus of the stria terminalis (BNST) and supraoptic nucleus, and vasopressin ( Avp ) in the BNST and upregulated Avp1ar in BNST, and Oxtr in the paraventricular nucleus. Our work demonstrates that developmental PBDE exposure produces ASD-relevant neurochemical, olfactory processing and behavioral phenotypes that may result from early neurodevelopmental reprogramming within central social and memory networks.

Dust associated with various stellar sources in galaxies at all cosmic epochs remains a controversial topic, particularly whether supernovae play an important role in dust production. We report evidence of dust formation in the cold, dense shell behind the ejecta–circumstellar medium (CSM) interaction in the Type Ia-CSM supernova (SN) 2018evt three years after the explosion, characterized by a rise in mid-infrared emission accompanied by an accelerated decline in the optical radiation of the SN. Such a dust-formation picture is also corroborated by the concurrent evolution of the profiles of the Hα emission line. Our model suggests enhanced CSM dust concentration at increasing distances from the SN as compared to what can be expected from the density profile of the mass loss from a steady stellar wind. By the time of the last mid-infrared observations at day +1,041, a total amount of 1.2 ± 0.2 × 10 −2   M ⊙ of new dust has been formed by SN 2018evt, making SN 2018evt one of the most prolific dust factories among supernovae with evidence of dust formation. The unprecedented witness of the intense production procedure of dust may shed light on the perceptions of dust formation in cosmic history. By day 1,041 after explosion, SN Ia-CSM 2018evt had produced an estimated 0.01 solar masses of dust in the cold, dense shell behind the supernova ejecta–circumstellar medium interaction, ranking it as one of the most prolific dust-producing supernovae ever recorded.

The Carnegie Supernova Project-II (CSP-II) was an NSF-funded, four-year program to obtain optical and near-infrared observations of a \"Cosmology\" sample of ∼100 Type Ia supernovae located in the smooth Hubble flow (0.03 z 0.10). Light curves were also obtained of a \"Physics\" sample composed of 90 nearby Type Ia supernovae at z ≤ 0.04 selected for near-infrared spectroscopic timeseries observations. The primary emphasis of the CSP-II is to use the combination of optical and near-infrared photometry to achieve a distance precision of better than 5%. In this paper, details of the supernova sample, the observational strategy, and the characteristics of the photometric data are provided. In a companion paper, the near-infrared spectroscopy component of the project is presented.

The Carnegie Supernova Project-II (CSP-II) was an NSF-funded, four-year program to obtain optical and near-infrared observations of a \"Cosmology\" sample of ~100 Type Ia supernovae located in the smooth Hubble flow (0.03 $\\lesssim$ z $\\lesssim$ 0.10). Light curves were also obtained of a \"Physics\" sample composed of 90 nearby Type Ia supernovae at z ≤ 0.04 selected for near-infrared spectroscopic timeseries observations. The primary emphasis of the CSP-II is to use the combination of optical and near-infrared photometry to achieve a distance precision of better than 5%. Here in this paper, details of the supernova sample, the observational strategy, and the characteristics of the photometric data are provided. In a companion paper, the near-infrared spectroscopy component of the project is presented.

We report evidence of dust formation in the cold, dense shell behind the ejecta-circumstellar medium (CSM) interaction in the Type Ia (SNIa) SN2018evt three years after the explosion, characterized by a rise in the mid-infrared (MIR) flux accompanied by an accelerated decline in the optical. Such a dust-formation picture is also corroborated by the concurrent evolution of the profiles of the Ha emission lines. Our models suggest enhanced dust concentration at increasing distances from the SN as compared to what can be expected from the density profile of the mass loss from a steady stellar wind. This may indicate an enhanced dust presence at larger distances from the progenitor star. The dust distribution can be modeled in terms of a double-shell which assumes a sudden change of the density profile of the dust or a single-shell model with a flatter radial profile. The inferred mass-loss history of SN2018evt is consistent with a progenitor's mass loss in a binary system containing a C/O white dwarf and a massive asymptotic giant branch star. The grand rebrightening in the MIR after day +310 is attributed to the formation of new dust within the CDS region behind the forward shock. The mass of the newly-formed dust increases rapidly with time and follows a power law with an index of 4. By the time of the last MIR observations at day +1041, a total amount of 1.2+-0.2 x 10^{-2} Msun of dust has been produced, making SN 2018evt one of the most prolific dust factory among SNe with evidence of dust formations.

We construct average spectra of host galaxies of slower, faster, bluer, and redder Type Ia Supernovae (SNe Ia) from the SDSS-II supernova survey. The average spectrum of slower declining (broader light-curve width or higher stretch) SN Ia hosts shows stronger emission lines compared to the average spectrum of faster declining (narrower light-curve width or lower stretch) SN Ia hosts. Using pPXF, we find that hosts of slower declining SNe Ia have metallicities that are, on average, 0.24 dex lower than average metallicities of faster declining SN Ia hosts. Similarly, redder SN Ia hosts have slightly higher metallicities than bluer SN Ia hosts. Lick index analysis of metallic lines and Balmer lines show that faster declining SN Ia hosts have relatively higher metal content and have relatively older stellar populations compared with slower declining SN Ia hosts. We calculate average \\(\\rm H_{\\alpha}\\) Star Formation Rate (SFR), stellar mass, and the specific-SFR (sSFR) of host galaxies in these subgroups of SNe Ia. We find that slower declining SN Ia hosts have significantly higher (\\(>5\\sigma\\)) sSFR than faster declining SN Ia hosts. A Kolmogorov-Smirnov test shows that these two types of hosts originate from different parent distributions. Our results, when compared with the models of \\cite{childress14}, indicate that slower declining SNe Ia, being hosted in actively star-forming galaxies, are young (prompt) SNe Ia, originating from similar progenitor age groups.

Astrophysical cosmology constrains the variation of Newton's Constant in a manner complementary to laboratory experiments, such as the celebrated lunar laser ranging campaign. Supernova cosmology is an example of the former and has attained campaign status, following planning by a Dark Energy Task Force in 2005. In this paper we employ the full SNIa dataset to the end of 2013 to set a limit on G variation. In our approach we adopt the standard candle delineation of the redshift distance relation. We set an upper limit on its rate of change |G dot / G| of 0.1 parts per billion per year over 9 Gyrs. By contrast lunar laser ranging tests variation of G over the last few decades. Conversely, one may adopt the laboratory result as a prior and constrain the effect of variable G in dark energy equation of state experiments to delta w < 0.02. We also examine the parameterization G ~ 1 + z. Its short expansion age conflicts with the measured values of the expansion rate and the density in a flat Universe. In conclusion, supernova cosmology complements other experiments in limiting G variation. An important caveat is that it rests on the assumption that the same mass of 56Ni is burned to create the standard candle regardless of redshift. These two quantities, f and G, where f is the Chandrasekhar mass fraction burned, are degenerate. Constraining f variation alone requires more understanding of the SNIa mechanism.

1991T-like supernovae are the luminous, slow-declining extreme of the Branch shallow-silicon (SS) subclass of Type Ia supernovae. They are distinguished by extremely weak Ca II H & K and Si II \\(\\lambda6355\\) and strong Fe III absorption features in their optical spectra at pre-maximum phases, and have long been suspected to be over-luminous compared to normal Type Ia supernovae. In this paper, the pseudo equivalent width of the Si II \\(\\lambda\\)6355 absorption obtained at light curve phases from \\(\\leq+10\\) days is combined with the morphology of the \\(i\\)-band light curve to identify a sample of 1991T-like supernovae in the Carnegie Supernova Project-II. Hubble diagram residuals show that, at optical as well as near-infrared wavelengths, these events are over-luminous by \\(\\sim\\)0.1-0.5 mag with respect to the less extreme Branch SS (1999aa-like) and Branch core-normal supernovae with similar \\(B\\)-band light curve decline rates.

We present multi-wavelength time-series spectroscopy of SN 2013aa and SN 2017cbv, two Type Ia supernovae (SNe Ia) on the outskirts of the same host galaxy, NGC 5643. This work utilizes new nebular-phase near-infrared (NIR) spectra obtained by the Carnegie Supernova Project-II, in addition to previously published optical and NIR spectra. By measuring nebular-phase [Fe II] lines in both the optical and NIR, we examine the explosion kinematics and test the efficacy of several emission line fitting techniques commonly used in the literature. The NIR [Fe II] 1.644 \\(\\mu\\)m line provides the most robust velocity measurements against variations due to the choice of the fit method and line blending. The resulting effects on velocity measurements due to choosing different fit methods, initial fit parameters, continuum and line profile functions, and fit region boundaries were also investigated. The NIR [Fe II] velocities yield the same radial shift direction as velocities measured using the optical [Fe II] 7155 A line, but the sizes of the shifts are consistently and substantially lower, pointing to a potential issue in optical studies. The NIR [Fe II] 1.644 \\(\\mu\\)m emission profile shows a lack of significant asymmetry in both SNe Ia, and the observed low velocities elevate the importance for correcting for any radial velocity contribution from the host galaxy's rotation. The low [Fe II] velocities measured in the NIR at nebular phases disfavors most progenitor scenarios in close double-degenerate systems for both SN 2013aa and SN 2017cbv. The time evolution of the NIR [Fe II] 1.644 \\(\\mu\\)m line also indicates moderately high progenitor white dwarf central density and potentially high magnetic fields. These sibling SNe Ia were well observed at both early and late times, providing an excellent opportunity to study the intrinsic diversity of SNe Ia.