Foreground Extinction to Extended Celestial Objects. I. New Extinction Maps

We present new three-dimensional (3D) interstellar extinctionmaps in the V and Gaia G filterswithin 2 kpc of the Sun, a 3D differential extinction (dust density) map along the line of sight in the samespace, a 3D map of variations in the ratio of the extinctions in the V and Gaia G filters within 800 pcof the Sun, and a 2D map of total Galactic extinction through the entire dust half-layer from the Sun toextragalactic space for Galactic latitudes |b| 13◦. The 3D maps have a transverse resolution from 3.6to 11.6 pc and a radial resolution of 50 pc. The 2D map has an angular resolution of 6.1 arcmin. Wehave produced these maps based on the Gaia DR3 parallaxes and Gaia, Pan-STARRS1, SkyMapper,2MASS, andWISE photometry for ∼ 100 million stars. We have paid special attention to the space within200 pc of the Sun and high Galactic latitudes as regions where the extinction estimates have had a largerelative uncertainty so far. Our maps estimate the extinction within the Galactic dust layer from the Sunto an extended object or through the entire dust half-layer from the Sun to extragalactic space with anaccuracy σ(AV) = 0.06 mag. This gives a high relative accuracy of extinction estimates even at highGalactic latitudes, where, according to our estimates, the median total Galactic extinction through theentire dust half-layer from the Sun to extragalactic objects is AV = 0.12 ± 0.06 mag. We have shown thatthe presented maps are among the best ones in data volume, space size, resolution, accuracy, and otherproperties.

Context. Gaia parallaxes and photometric measurements open a three-dimensional (3D) era for the Milky Way, including its interstellar (IS) matter. Three-dimensional Galactic dust distributions are constructed in various ways, based on Gaia data and photometric or spectroscopic surveys. Aims. The assignment of radial motions to IS dust structures seen in 3D, or 3D kinetic tomography, would be a valuable tool allowing one to connect the structures to emission lines of the associated gas, which are now measured at increasingly higher spectral and angular resolutions, and rich in information on physical and chemical processes. To this end, one of the potential techniques is to establish a link between dust clouds and Doppler velocities of absorption lines imprinted in stellar spectra by the gas associated with the dust. This requires a relatively close correlation between the absorber column and the dust opacity. We have investigated the link between the strength of interstellar K I absorption and the opacity of the dust in front of stars in the Taurus area, and we have tested the feasibility of assigning velocities to 3D dust clouds on the basis of K I absorption data. Methods. We have obtained high spectral resolution and high signal-to-noise spectra of 58 early-type stars in the direction of the Taurus, Perseus, and California molecular clouds. We have developed a new, dual interstellar and telluric profile-fitting technique to extract the interstellar K I λλ 7665, 7699 Å absorption lines from stellar spectra and applied it to the new data and to archived spectra of 58 additional targets. In parallel, we have updated 3D dust maps reconstructed through the inversion of individual stellar light extinctions. To do so, we supplemented the catalog of extinction estimates based on Gaia and 2MASS photometry with recently published extinction catalogs based on stellar spectroscopic surveys. We used the 3D map and the set of velocity components seen in absorption to assign radial velocities to the dust clouds distributed along their paths in the most consistent way. Results. We illustrate our profile-fitting technique and present the K I velocity structure of the dense ISM along the paths to all targets. As a validation test of the dust map, we show comparisons between distances to several reconstructed clouds with recent distance assignments based on different techniques. Target star extinctions estimated by integration in the 3D map are compared with their K I 7699 Å absorptions and the degree of correlation is found comparable to the one between the same K I line and the total hydrogen column for stars distributed over the sky that are part of a published high resolution survey. We show images of the updated dust distribution in a series of vertical planes in the Galactic longitude interval 150–182.5° and our estimated assignments of radial velocities to the opaque regions. Most clearly defined K I absorptions may be assigned to a dense dust cloud between the Sun and the target star. It appeared relatively straightforward to find a velocity pattern consistent will all absorptions and ensuring coherence between adjacent lines of sight, at the exception of a few weak lines. We compare our results with recent determinations of the velocities of several clouds and find good agreement. These results demonstrate that the extinction-K I relationship is tight enough to allow one to link the radial velocity of the K I lines to the dust clouds seen in 3D and that their combination may be a valuable tool in building a 3D kinetic structure of the dense ISM. We discuss limitations and perspectives for this technique.

Galactic interstellar extinction maps are powerful and necessary tools for Milky Way structure and stellar population analyses, particularly toward the heavily reddened bulge and in the midplane. However, due to the difficulty of obtaining reliable extinction measures and distances for a large number of stars that are independent of these maps, tests of their accuracy and systematics have been limited. Our goal is to assess a variety of photometric stellar extinction estimates, including both two-dimensional and three-dimensional extinction maps, using independent extinction measures based on a large spectroscopic sample of stars toward the Milky Way bulge. We employ stellar atmospheric parameters derived from high-resolution H-band Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra, combined with theoretical stellar isochrones, to calculate line-of-sight extinction and distances for a sample of more than 2400 giants toward the Milky Way bulge. We compare these extinction values to those predicted by individual near-IR and near+mid-IR stellar colors, two-dimensional bulge extinction maps, and three-dimensional extinction maps. The long baseline, near+mid-IR stellar colors are, on average, the most accurate predictors of the APOGEE extinction estimates, and the two-dimensional and three-dimensional extinction maps derived from different stellar populations along different sightlines show varying degrees of reliability. We present the results of all of the comparisons and discuss reasons for the observed discrepancies. We also demonstrate how the particular stellar atmospheric models adopted can have a strong impact on this type of analysis, and discuss related caveats.

The Carnegie Supernova Project (CSP) is designed to measure the luminosity distance for Type Ia supernovae (SNe Ia) as a function of redshift, and to set observational constraints on the dark energy contribution to the total energy content of the Universe. The CSP differs from other projects to date in its goal of providing an I-band {rest-frame} Hubble diagram. Here we present the first results from near-infrared (NIR) observations obtained using the Magellan Baade telescope for SNe Ia with 0.1 < z < 0.7. We combine these results with those from the low-redshift CSP at z <0.1 (Folatelli et al. 2009). We present light curves and an I-band Hubble diagram for this first sample of 35 SNe Ia and we compare these data to 21 new SNe Ia at low redshift. These data support the conclusion that the expansion of the Universe is accelerating. When combined with independent results from baryon acoustic oscillations (Eisenstein et al. 2005), these data yield Omega_m = 0.27 +/- 0.0 (statistical), and Omega_DE = 0.76 +/- 0.13 (statistical) +/- 0.09 (systematic), for the matter and dark energy densities, respectively. If we parameterize the data in terms of an equation of state, w, assume a flat geometry, and combine with baryon acoustic oscillations, we find that w = -1.05 +/- 0.13 (statistical) +/- 0.09 (systematic). The largest source of systematic uncertainty on w arises from uncertainties in the photometric calibration, signaling the importance of securing more accurate photometric calibrations for future supernova cosmology programs. Finally, we conclude that either the dust affecting the luminosities of SNe Ia has a different extinction law (R_V = 1.8) than that in the Milky Way (where R_V = 3.1), or that there is an additional intrinsic color term with luminosity for SNe Ia independent of the decline rate.

SweetSpot is a 3 yr National Optical Astronomy Observatory (NOAO) survey program to observe Type Ia supernovae (SNe Ia) in the smooth Hubble flow with the WIYN High-resolution Infrared Camera (WHIRC) on the WIYN 3.5 m telescope. We present data from the first half of this survey, covering the 2011B–2013B NOAO semesters and consisting of 493 calibrated images of 74 SNe Ia observed in the rest-frame near-infrared (NIR) in the range 0.02 &lt; z &lt; 0.09. Because many observed supernovae require host-galaxy subtraction from templates taken in later semesters, this release contains only the 186 NIR (JHK s ) data points for the 33 SNe Ia that do not require host-galaxy subtraction. The sample includes four objects with coverage beginning before the epoch of B-band maximum and 27 beginning within 20 days of B-band maximum. We also provide photometric calibration between the WIYN+WHIRC and Two Micron All-Sky Survey (2MASS) systems, along with light curves for 786 2MASS stars observed alongside the SNe Ia. This work is the first in a planned series of three SweetSpot Data Releases. Future releases will include the full set of images from all 3 yr of the survey, including host-galaxy reference images and updated data processing with host-galaxy reference subtraction. SweetSpot will provide a well-calibrated sample that will help improve our ability to standardize distance measurements to SNe Ia, examine the intrinsic optical–NIR colors of SNe Ia at different epochs, explore the nature of dust in other galaxies, and act as a stepping-stone for more distant, potentially space-based surveys.

Investigating the extinction properties in dense molecular clouds is of significant importance for understanding the behavior of interstellar dust and its impact on observations. In this study, we comprehensively examined the extinction law in the Ophiuchus cloud across a wavelength range from 0.8 μm to 8 μm. To achieve this, we analyzed NIR and MIR data obtained from the UKIDSS GCS and the Spitzer c2d survey, respectively. By fitting a series of color–color diagrams, we determined color-excess ratios EJ−λ/EJ−K for seven passbands. These ratios were then directly converted to derive the relative extinction law Aλ/AK. Our findings demonstrate that the Ophiuchus cloud exhibits a characteristic of flat MIR extinction, consistent with previous studies. Additionally, our results reveal variations in the extinction law with extinction depth, indicating a flatter trend from the NIR to MIR bands as extinction increases. Notably, our analysis reveals no significant difference in the MIR extinction law among the four dark clouds: L1712, L1689, L1709, and L1688. However, distinct variations were observed in the extinction law for regions outside the dark clouds, specifically L1688N and L1688W. These regions displayed lower color-excess ratios EJ−λ/EJ−K in the Spitzer/IRAC bands. This observation lends support to the dust growth occurring in the dense regions of the Ophiuchus cloud.

This is the first release of optical spectroscopic data of low-redshift Type\nIa supernovae (SNe Ia) by the Carnegie Supernova Project including 604\npreviously unpublished spectra of 93 SNe Ia. The observations cover a range of\nphases from 12 days before to over 150 days after the time of B-band maximum\nlight. With the addition of 228 near-maximum spectra from the literature we\nstudy the diversity among SNe Ia in a quantitative manner. For that purpose,\nspectroscopic parameters are employed such as expansion velocities from\nspectral line blueshifts, and pseudo-equivalent widths (pW). The values of\nthose parameters at maximum light are obtained for 78 objects, thus providing a\ncharacterization of SNe Ia that may help to improve our understanding of the\nproperties of the exploding systems and the thermonuclear flame propagation.\nTwo objects, namely SNe 2005M and 2006is, stand out from the sample by showing\npeculiar Si II and S II velocities but otherwise standard velocities for the\nrest of the ions. We further study the correlations between spectroscopic and\nphotometric parameters such as light-curve decline rate and color. In agreement\nwith previous studies, we find that the pW of Si II absorption features are\nvery good indicators of light-curve decline rate. Furthermore, we demonstrate\nthat parameters such as pW2(SiII4130) and pW6(SiII5972) provide precise\ncalibrations of the peak B-band luminosity with dispersions of ~0.15 mag. In\nthe search for a secondary parameter in the calibration of peak luminosity for\nSNe Ia, we find a ~2--3-sigma correlation between B-band Hubble residuals and\nthe velocity at maximum light of S II and Si II lines.\n

Large stellar surveys are sensitive to interstellar dust through the effects of reddening. Using extinctions measured from photometry and spectroscopy, together with three-dimensional (3D) positions of individual stars, it is possible to construct a three-dimensional dust map. We present the first continuous map of the dust distribution in the Galactic disk out to 7 kpc within 100 pc of the Galactic midplane, using red clump and giant stars from SDSS APOGEE DR14. We use a non-parametric method based on Gaussian Processes to map the dust density, which is the local property of the ISM rather than an integrated quantity. This method models the dust correlation between points in 3D space and can capture arbitrary variations, unconstrained by a pre-specified functional form. This produces a continuous map without line-of-sight artefacts. Our resulting map traces some features of the local Galactic spiral arms, even though the model contains no prior suggestion of spiral arms, nor any underlying model for the Galactic structure. This is the first time that such evident arm structures have been captured by a dust density map in the Milky Way. Our resulting map also traces some of the known giant molecular clouds in the Galaxy and puts some constraints on their distances, some of which were hitherto relatively uncertain.

We present an extinction map of the Polaris molecular cirrus cloud derived from star counts and compare it with the Schlegel et al. [13] extinction map derived from the far-infrared dust opacity. We find that, within the Polaris cloud, the Schlegel et al. [13] AV values are, on average, a factor 2 higher than the star count values. We propose that this discrepancy results from a difference in τFIR/AV between the diffuse atomic medium and the Polaris cloud. We use the difference in spectral energy distribution, warm for the diffuse atomic medium, cold for the Polaris cloud, to separate their respective contribution to the line of sight integrated infrared emission and find that the τFIR/AV of cold dust in Polaris is on average 4 times higher than the Schlegel et al. [13] value for dust in atomic cirrus. This change in dust property could be interpreted by a growth of fluffy particles within low opacity molecular cirrus clouds such as Polaris. Our work suggests that variations in dust emissivity must be taken into account to estimate AV from dust emission wherever cold infrared emission is present (i.e. molecular clouds).

\n \nWe present an extinction map of the Polaris molecular cirrus cloud derived\nfrom star counts and compare it with the Schlegel et al. ([CITE]) extinction map\nderived from the far-infrared dust opacity.\nWe find that, within the Polaris cloud, the Schlegel et al. ([CITE])\nAV values are a factor 2 to 3 higher than the star count values. \nWe propose that this discrepancy results from a difference in \n$\\tau_{\\rm FIR}/ A_V$ between the diffuse atomic medium and the Polaris \ncloud. We use the difference in spectral energy distribution, warm for \nthe diffuse atomic medium, cold for the Polaris cloud, to separate\ntheir respective contribution to the line of sight integrated infrared\nemission and find that the $\\tau_{\\rm FIR}/ A_V$ of cold dust in\nPolaris is on average 4 times higher than the Schlegel et al. ([CITE]) value for dust\nin atomic cirrus. This change in dust property could be interpreted by a\ngrowth of fluffy particles within low opacity molecular cirrus clouds such\nas Polaris. \nOur work suggests that variations in dust emissivity must be taken \ninto account to estimate AV from dust emission wherever cold\ninfrared emission is present (i.e. molecular clouds). \n \n\n

Type Ia supernovae (SNe Ia) are runaway thermonuclear explosions in white dwarfs that result in the disruption of the white dwarf star, and possibly its nearby stellar companion. SNe Ia occur over an immense range of stellar population age and host galaxy environments, and play a critical role in the nucleosynthesis of intermediate-mass and iron-group elements, primarily the production of nickel, iron, cobalt, chromium, and manganese. Though the nature of their progenitors is still not well-understood, SNe Ia are unique among stellar explosions in that the majority of them exhibit a systematic lightcurve relation: more luminous supernovae dim more slowly over time than less luminous supernovae in optical light (intrinsically brighter SNe Ia have broader lightcurves). This feature, unique to SNe Ia, is rather remarkable and allows their peak luminosities to be determined with fairly high accuracy out to cosmological distances via measurement of their lightcurve decline. Further, studying SNe Ia gives us important insights into binary star evolution physics, since it is widely agreed that the progenitors of SNe Ia are binary (possibly multiple) star systems. In this review, we give a current update on the different proposed Type Ia supernova progenitors, including descriptions of possible binary star configurations, and their explosion mechanisms, from a theoretical perspective. We additionally give a brief overview of the historical (focussing on the more recent) observational work that has helped the astronomical community to understand the nature of the most important distance indicators in cosmology.

Type Ia supernovae (SNe Ia) provide the robustest means of measuring extragalactic distances. While increasing the number of SNe Ia observed in the optical has received most effort so far, near-infrared (NIR) observations remain scarce despite their advantages. The dust extinction in NIR observations is lower and the behavior of standard candles is more intrinsic and therefore requires little to no empirical corrections. We present the ANDICAM-SOFI Near-infrared and Optical type Ia Supernova (ASNOS) dataset with sample size of 1,482 epochs in the BVRIYJH filters from the ANDICAM instrument on the 1.3-meter SMARTS telescope at Cerro Tololo Inter-American Observatory, along with 125 JHK epochs from the SOFI instrument on the 3.58-meter New Technology Telescope on the La Silla Observatory. Additionally, we incorporate optical forced photometry from the Zwicky Transient Facility and the Asteroid Terrestrial-impact Last Alert System. The sample comprises 41 SNe Ia in total, including 29 normal events, eight 1991T-like objects, and four peculiar subtypes, all located at redshifts z &lt; 0.085. We provide a detailed overview of the ASNOS sample selection, data reduction, SN photometry, construction of the global and local host-galaxy spectral energy distribution, and SN light-curve fitting using three methods: SALT3-NIR, SNooPy, and BayeSN. A companion paper will present the cosmological analysis.

We present the Galactic Arecibo L-Band Feed Array H i (GALFA-H i) survey data release 2 (DR2). The survey covers the 21 cm hyperfine transition of Galactic H i from −650 to 650 , with 0.184 channel spacing, 4′ angular resolution, and 150 mK rms noise per 1 velocity channel. DR2 covers the entirety of the sky available from the William E. Gordon 305 m antenna at Arecibo, from decl. −1°17′ to decl. + 37°57′ across all R.A.: 4 steradians or 32% of the sky. DR2 differs in a number of ways from data release 1, which was released in 2011. DR2 is built from a largely separate set of observations from DR1, which were taken in a much more consistent mode. This consistency, coupled with more careful attention to systematics and more advanced data reduction algorithms, leads to a much higher-quality DR2 data product. We present three data sets for public use: H i data cubes, far-sidelobe stray-radiation-corrected column density maps, and results of the Rolling Hough Transform linear feature detection algorithm.

We measured the extinction law in the 30 Dor star formation region in the Large Magellanic Cloud using Early Release Observations (EROs) taken with Near-Infrared Camera (NIRCam) on board the JWST, thereby extending previous studies carried out with the Hubble Space Telescope to the infrared. We used red clump stars to derive the direction of the reddening vector in twelve bands and we present the extinction law in this massive star forming region from 0.3 to 4.7 μm. At wavelengths longer than 1 μm, we find a ratio of total and selective extinction twice as high as in the diffuse Milky Way interstellar medium and a change in the relative slope from the optical to the infrared domain. Additionally, we derive an infrared extinction map and find that extinction closely follows the structure of the highly embedded regions of 30 Dor.

We investigate the statistical dependence of the peak intrinsic colors of\nType Ia supernovae (SN Ia) on their expansion velocities at maximum light,\nmeasured from the Si II 6355 spectral feature. We construct a new hierarchical\nBayesian regression model, accounting for the random effects of intrinsic\nscatter, measurement error, and reddening by host galaxy dust, and implement a\nGibbs sampler and deviance information criteria to estimate the correlation.\nThe method is applied to the apparent colors from BVRI light curves and Si II\nvelocity data for 79 nearby SNe Ia. The apparent color distributions of high\n(HV) and normal velocity (NV) supernovae exhibit significant discrepancies for\nB-V and B-R, but not other colors. Hence, they are likely due to intrinsic\ncolor differences originating in the B-band, rather than dust reddening. The\nmean intrinsic B-V and B-R color differences between HV and NV groups are 0.06\n+/- 0.02 and 0.09 +/- 0.02 mag, respectively. A linear model finds significant\nslopes of -0.021 +/- 0.006 and -0.030 +/- 0.009 mag/(1000 km/s) for intrinsic\nB-V and B-R colors versus velocity, respectively. Since the ejecta velocity\ndistribution is skewed towards high velocities, these effects imply\nnon-Gaussian intrinsic color distributions with skewness up to +0.3. Accounting\nfor the intrinsic color-velocity correlation results in corrections to A_V\nextinction estimates as large as -0.12 mag for HV SNe Ia and +0.06 mag for NV\nevents. Velocity measurements from SN Ia spectra have potential to diminish\nsystematic errors from the confounding of intrinsic colors and dust reddening\naffecting supernova distances.\n