- ID:
- ivo://CDS.VizieR/J/ApJ/836/199
- Title:
- IRDC G028.23-00.19 NIR polarimetry analysis
- Short Name:
- J/ApJ/836/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The importance of the magnetic (B) field in the formation of infrared dark clouds (IRDCs) and massive stars is an ongoing topic of investigation. We studied the plane-of-sky B field for one IRDC, G028.23-00.19, to understand the interaction between the field and the cloud. We used near-IR background starlight polarimetry to probe the B field and performed several observational tests to assess the field importance. The polarimetric data, taken with the Mimir instrument, consisted of H-band and K-band observations, totaling 17160 stellar measurements. We traced the plane-of-sky B-field morphology with respect to the sky-projected cloud elongation. We also found the relationship between the estimated B-field strength and gas volume density, and we computed estimates of the normalized mass-to-magnetic flux ratio. The B-field orientation with respect to the cloud did not show a preferred alignment, but it did exhibit a large-scale pattern. The plane-of-sky B-field strengths ranged from 10 to 165{mu}G, and the B-field strength dependence on density followed a power law with an index consistent with 2/3. The mass-to-magnetic flux ratio also increased as a function of density. The relative orientations and relationship between the B field and density imply that the B field was not dynamically important in the formation of the IRDC. The increase in mass-to-flux ratio as a function of density, though, indicates a dynamically important B field. Therefore, it is unclear whether the B field influenced the formation of G28.23. However, it is likely that the presence of the IRDC changed the local B-field morphology.
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7122. IRDC18223 images
- ID:
- ivo://CDS.VizieR/J/A+A/584/A67
- Title:
- IRDC18223 images
- Short Name:
- J/A+A/584/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Filamentary structures in the interstellar medium are crucial ingredients of the star formation process. They fragment to form individual star-forming cores, and at the same time they may also funnel gas toward the central gas cores, providing an additional gas reservoir. We want to resolve the length scales for filament formation and fragmentation (resolution <=0.1pc), in particular the Jeans length and cylinder fragmentation scale. We have observed the prototypical high-mass star-forming filament IRDC 18223 with the Plateau de Bure Interferometer (PdBI) in the 3.2mm continuum and N_2_H^+^(1-0) line emission in a ten-field mosaic at a spatial resolution of ~4{deg} (~14000au).
- ID:
- ivo://CDS.VizieR/J/A+A/603/A22
- Title:
- IRDCs cores spectra of HCN and HNC isotopologue
- Short Name:
- J/A+A/603/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the measurement of nitrogen fractionation in a sample of infrared-dark clouds (IRDCs) cores which are believed to be the precursors of high-mass stars and star clusters. We observed the J=1-0 transitions of HCN, H^13/^CN, HC^15/^N, HN^13/^C, and H^15/^NC towards a sample of 22 cores in four IRDCs using the IRAM 30m telescope.Assuming LTE and a temperature of 15K, the 14N/^15/^N ratios measured are consistent with the terrestrial atmosphere(TA) and protosolar nebula(PSN) values, and with the ratios measured in low-mass prestellar cores. However, the 14N/^15/^N ratios measured in cores C1, C3, F1, F2, and G2 do not agree with the results from similar studies towards the same cores using nitrogen bearing molecules with nitrile functional group(-CN) and nitrogen hydrides (-NH) although the ratio spread covers a similar range. Relatively low 14N/^15/^N ratios amongst the four-IRDCs were measured in IRDC G which are comparable to those measured in small cosmomaterials and protoplanetary disks. The low average gas density of this cloud suggests that the gas density, rather than the gas temperature, may be the dominant parameter influencing the initial nitrogen isotopic composition in young PSN.
- ID:
- ivo://CDS.VizieR/J/ApJ/694/546
- Title:
- IR dust bubbles. II. YSOs model parameters
- Short Name:
- J/ApJ/694/546
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of late-O/early-B-powered, parsec-sized bubbles and associated star formation using Two Micron All Sky Survey, GLIMPSE, MIPSGAL, and MAGPIS surveys. Three bubbles were selected from the Churchwell et al. catalog (2007, Cat. J/ApJ/670/428). We confirm that the structure identified in Watson et al. (2008ApJ...681.1341W) holds in less energetic bubbles, i.e., a photodissociated region, identified by 8um emission due to polycyclic aromatic hydrocarbons surrounding hot dust, identified by 24um emission and ionized gas, and identified by 20cm continuum. We estimate the dynamical age of two bubbles by comparing bubble sizes to numerical models of Hosokawa and Inutsuka. We also identify and analyze candidate young stellar objects using spectral energy distribution (SED) fitting and identify sites of possible triggered star formation. Lastly, we identify likely ionizing sources for two sources based on SED fitting.
- ID:
- ivo://CDS.VizieR/J/MNRAS/437/391
- Title:
- IR excess in Sun-like stars observed by WISE
- Short Name:
- J/MNRAS/437/391
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for infrared-excess (IR-excess) candidates in a comprehensive (29000 stars) magnitude-limited sample of dwarf stars, spanning the spectral range F2-K0, and brighter than V=15mag. We searched the sample within the WISE all sky survey data base for objects within 1 arcsec of the coordinates provided by the SIMBAD data base, and found over 9000 sources detected in all WISE bands. The sample excludes objects that are flagged as extended sources and those images that are affected by various optical artefacts. For each detected object, we compared the observed W4/W2 (22{mu}m/4.6{mu}m) flux ratio with the expected photospheric value and identified 197 excess candidates at 3{sigma}. For the vast majority of candidates, the results of this analysis represent the first reported evidence of an IR excess. Through the comparison with a simple blackbody emission model, we derive estimates of the dust temperature, as well as of the dust fractional luminosities. For more than 80 percent of the sample, this temperature is higher than 120K, suggesting the presence of warm circumstellar dust. Complementary observations at longer wavelengths (far-IR and submillimetre) are required for better characterizing and explaining the origin of this emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/658/1264
- Title:
- IR-excess sources in GLIMPSE and MSX
- Short Name:
- J/ApJ/658/1264
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 230 Tycho-2 Spectral Catalog stars that exhibit 8um mid-IR extraphotospheric excesses in the MSX and Spitzer GLIMPSE surveys. Of these, 183 are either OB stars earlier than B8 in which the excess plausibly arises from a thermal bremsstrahlung component or evolved stars in which the excess may be explained by an atmospheric dust component. The remaining 47 stars have spectral classifications B8 or later and appear to be main-sequence or late pre-main-sequence objects harboring circumstellar disks. Six of the 47 stars exhibit multiple signatures characteristic of pre-main-sequence circumstellar disks, including emission lines, near-IR K-band excesses, and X-ray emission. Approximately one-third of the remaining 41 sources have emission lines suggesting relative youth. We modeled the excesses in 26 stars having two or more measurements in excess of the expected photospheres as single-component blackbodies.
- ID:
- ivo://CDS.VizieR/J/ApJS/225/15
- Title:
- IR excess stars from Tycho-2 and AllWISE
- Short Name:
- J/ApJS/225/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The conclusion of the Wide-Field Infrared Survey Explorer (WISE) mission presents an opportune time to summarize the history of using excess emission in the infrared as a tracer of circumstellar material and exploit all available data for future missions such as the James Webb Space Telescope. We have compiled a catalog of infrared excess stars from peer-reviewed articles and perform an extensive search for new infrared excess stars by cross-correlating the Tycho-2 and all-sky WISE (AllWISE) catalogs. We define a significance of excess in four spectral type divisions and select stars showing greater than either 3{sigma} or 5{sigma} significance of excess in the mid- and far-infrared. Through procedures including spectral energy distribution fitting and various image analyses, each potential excess source was rigorously vetted to eliminate false positives. The infrared excess stars from the literature and the new stars found through the Tycho-2 and AllWISE cross-correlation produced nearly 500 "Prime" infrared excess stars, of which 74 are new sources of excess, and >1200 are "Reserved" stars, of which 950 are new sources of excess. The main catalog of infrared excess stars are nearby, bright, and either demonstrate excess in more than one passband or have infrared spectroscopy confirming the infrared excess. This study identifies stars that display a spectral energy distribution suggestive of a secondary or post-protoplanetary generation of dust, and they are ideal targets for future optical and infrared imaging observations. The final catalogs of stars summarize the past work using infrared excess to detect dust disks, and with the most extensive compilation of infrared excess stars (~1750) to date, we investigate various relationships among stellar and disk parameters.
- ID:
- ivo://CDS.VizieR/J/ApJ/555/932
- Title:
- IR fluxes of solar-type stars
- Short Name:
- J/ApJ/555/932
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using ISO-ISOPHOT, we carried out a survey of almost 150 stars to search for evidence of emission from dust orbiting young main-sequence stars, both in clusters and isolated systems. Over half of the detections are new examples of dusty stellar systems and demonstrate that such dust can be detected around numerous stars older than a few times 10^6^yr. Fluxes at 60 and either 90 or 100{mu}m or the new excess sources together with improved fluxes for a number of IRAS-identified sources are presented. Analysis of the excess luminosity relative to the stellar photosphere shows a systematic decline of this excess with stellar age consistent with a power-law index of -2.
- ID:
- ivo://CDS.VizieR/J/AJ/144/11
- Title:
- IR imaging, nuclear SEDs, Spitzer spectra of 22 AGNs
- Short Name:
- J/AJ/144/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution mid-infrared (MIR) imaging, nuclear spectral energy distributions (SEDs), and archival Spitzer spectra for 22 low-luminosity active galactic nuclei (LLAGNs; L_bol_<~10^42^erg/s). Infrared (IR) observations may advance our understanding of the accretion flows in LLAGNs, the fate of the obscuring torus at low accretion rates, and, perhaps, the star formation histories of these objects. However, while comprehensively studied in higher-luminosity Seyferts and quasars, the nuclear IR properties of LLAGNs have not yet been well determined. We separate the present LLAGN sample into three categories depending on their Eddington ratio and radio emission, finding different IR characteristics for each class. (1) At the low-luminosity, low-Eddington-ratio (log L_bol_/L_Edd_< -4.6) end of the sample, we identify "host-dominated" galaxies with strong polycyclic aromatic hydrocarbon bands that may indicate active (circum-)nuclear star formation. (2) Some very radio-loud objects are also present at these low Eddington ratios. The IR emission in these nuclei is dominated by synchrotron radiation, and some are likely to be unobscured type 2 AGNs that genuinely lack a broad-line region. (3) At higher Eddington ratios, strong, compact nuclear sources are visible in the MIR images. The nuclear SEDs of these galaxies are diverse; some resemble typical Seyfert nuclei, while others lack a well-defined MIR "dust bump." Strong silicate emission is present in many of these objects. We speculate that this, together with high ratios of silicate strength to hydrogen column density, could suggest optically thin dust and low dust-to-gas ratios, in accordance with model predictions that LLAGNs do not host a Seyfert-like obscuring torus. We anticipate that detailed modeling of the new data and SEDs in terms of accretion disk, jet, radiatively inefficient accretion flow, and torus components will provide further insights into the nuclear structures and processes of LLAGNs.
- ID:
- ivo://CDS.VizieR/J/AJ/144/187
- Title:
- Iris photometry near southern Cepheids. V. AQ Pup
- Short Name:
- J/AJ/144/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A photometric UBV survey is presented for 610 stars in a region surrounding the Cepheid AQ Puppis and centered southwest of the variable, based upon photoelectric measures for 14 stars and calibrated iris photometry of photographic plates of the field for 596 stars. An analysis of reddening and distance for program stars indicates that the major dust complex in this direction is ~1.8kpc distant, producing differential extinction described by a ratio of total-to-selective extinction of R=A_V_/E_B-V_=3.10+/-0.20. Zero-age main-sequence fitting for the main group of B-type stars along the line of sight yields a distance of 3.21+/-0.19kpc (V_0_-M_V_=12.53+/-0.13s.e.). The 29.97 Cepheid AQ Pup, of field reddening E_B-V_=0.47+/-0.07 (E_B-V_(B0)=0.51+/-0.07), appears to be associated with B-type stars lying within 5' of it as well as with a sparse group of stars, designated Turner 14, centered south of it at J2000.0=07:58:37, -29:25:00, with a mean reddening of E_B-V_=0.81+/-0.01. AQ Pup has an inferred luminosity as a cluster member of <M_V_>=-5.40+/-0.25 and an evolutionary age of 3x10^7^yr. Its observed rate of period increase of +300.1+/-1.2s/yr is an order of magnitude larger than what is observed for Cepheids of comparable period in the third crossing of the instability strip, and may be indicative of a high rate of mass loss or a putative fifth crossing. Another sparse cluster, designated Turner 13, surrounds the newly recognized 2.59 Cepheid V620 Pup, of space reddening E_B-V_=0.64+/-0.02 (E_B-V_(B0)=0.68+/-0.02), distance 2.88+/-0.11kpc (V_0_-M_V_=12.30+/-0.08s.e.), evolutionary age 10^8^yr, and an inferred luminosity as a likely cluster member of <M_V_>=-2.74+/-0.11. V620 Pup is tentatively identified as a first crosser, pending additional observations.