- ID:
- ivo://CDS.VizieR/J/A+A/581/L5
- Title:
- Mid-IR/radio correlation for Ghat galaxies
- Short Name:
- J/A+A/581/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Wright et al. (2014ApJ...792...26W) have embarked on a search for advanced Karadashev Type III civilisations via the compilation of a sample of sources with extreme mid-IR emission and colours. The aim is to furnish a list of candidate galaxies that might harbour an advanced Kardashev Type III civilisation; in this scenario, the mid-IR emission is then primarily associated with waste heat energy by-products. I apply the mid-IR radio correlation to this Glimpsing Heat from Alien Technology (Ghat) sample, a catalogue of 93 candidate galaxies compiled by Griffith et al., 2015ApJS..217...25G. I demonstrate that the mid-IR and radio luminosities are correlated for the sample, determining a k-corrected value of q_22_=1.35+/-0.42 . By comparison, a similar measurement for 124 galaxies drawn from the First Look Survey (FLS) has q_22_=0.87+/-0.27. The statistically significant difference of the mean value of q_22_ for these two samples, taken together with their more comparable far-IR properties, suggests that the Ghat sample shows excessive emission in the mid-IR. The fact that the Ghat sample largely follows the mid-IR radio correlation strongly suggests that the vast majority of these sources are associated with galaxies in which natural astrophysical processes are dominant. This simple application of the mid-IR radio correlation can substantially reduce the number of false positives in the Ghat catalogue since galaxies occupied by advanced Kardashev Type III civilisations would be expected to exhibit very high values of q. I identify nine outliers in the sample with q_22_>2 of which at least three have properties that are relatively well explained via standard astrophysical interpretations e.g. dust emission associated with nascent star formation and/or nuclear activity from a heavily obscured AGN. The other outliers have not been studied in any great detail, and are deserving of further observation. I also note that the comparison of resolved mid-IR and radio images of galaxies on sub-galactic (kpc) scales can also be useful in identifying and recognising artificial mid-IR emission from less advanced intermediate Type II/III civilisations. Nevertheless, from the bulk properties of the Ghat sample, I conclude that Kardashev Type III civilisations are either very rare or do not exist in the local Universe.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/177/431
- Title:
- Mid-IR sources in EGS
- Short Name:
- J/ApJS/177/431
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Extended Groth Strip (EGS) is one of the premier fields for extragalactic deep surveys. Deep observations of the EGS with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope cover an area of 0.38deg^2^ to a 50% completeness limit of 1.5uJy at 3.6um. The catalog comprises 57434 objects detected at 3.6um, with 84%, 28%, and 24% also detected at 4.5, 5.8, and 8.0um, respectively. Number counts are consistent with results from other Spitzer surveys. Color distributions show that the EGS IRAC sources comprise a mixture of populations: low-redshift star-forming galaxies, quiescent galaxies dominated by stellar emission at a range of redshifts, and high-redshift galaxies and AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/656/770
- Title:
- Mid-IR spectrum of star-forming galaxies
- Short Name:
- J/ApJ/656/770
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of low-resolution 5-38um Spitzer IRS spectra of the inner few square kiloparsecs of 59 nearby galaxies spanning a large range of star formation properties. A robust method for decomposing mid-infrared galaxy spectra is described and used to explore the behavior of PAH emission and the prevalence of silicate dust extinction.
- ID:
- ivo://CDS.VizieR/J/ApJ/771/88
- Title:
- Mid-IR Tully-Fisher relation with WISE & 2MTF
- Short Name:
- J/ApJ/771/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a mid-infrared Tully-Fisher (TF) relation using photometry from the 3.4{mu}m W1 band of the Wide-field Infrared Survey Explorer (WISE) satellite. The WISE TF relation is formed from 568 galaxies taken from the all-sky 2MASS Tully-Fisher (2MTF) galaxy catalog, spanning a range of environments including field, group, and cluster galaxies. This constitutes the largest mid-infrared TF relation constructed to date. After applying a number of corrections to galaxy magnitudes and line widths, we measure a master TF relation given by M_corr_=-22.24-10.05[log(W_corr_)-2.5], with an average dispersion of {sigma}_WISE_=0.686mag. There is some tension between WISE TF and a preliminary 3.6{mu}m relation, which has a shallower slope and almost no intrinsic dispersion. However, our results agree well with a more recent relation constructed from a large sample of cluster galaxies. We additionally compare WISE TF to the near-infrared 2MTF template relations, finding a good agreement between the TF parameters and total dispersions of WISE TF and the 2MTF K-band template. This fact, coupled with typical galaxy colors of (K-W1)~0, suggests that these two bands are tracing similar stellar populations, including the older, centrally-located stars in the galactic bulge which can (for galaxies with a prominent bulge) dominate the light profile.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A47
- Title:
- Milky Way nuclear star cluster extinction map
- Short Name:
- J/A+A/566/A47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although the Milky Way Nuclear Star Cluster (MWNSC) was discovered more than four decades ago, several of its key properties have not been determined unambiguously up to now because of the strong and spatially highly variable interstellar extinction toward the Galactic centre. In this paper we aim at determining the shape, size, and luminosity/mass of the MWNSC.In order to investigate the properties of the MWNSC, we use Spitzer/IRAC images at 3.6 and 4.5{mu}m, where interstellar extinction is at a minimum but the overall emission is still dominated by stars. We correct the 4.5{mu}m image for PAH emission with the help of the IRAC 8.0{mu}m map and for extinction with the help of a [3.6-4.5] colour map. Finally, we investigate the symmetry of the nuclear cluster and fit it with Sersic, Moffat, and King models. We present an extinction map for the central ~300x200pc^2^ of the Milky Way, as well as a PAH-emission and extinction corrected image of the stellar emission, with a resolution of about 0.20pc. We find that the MWNSC appears in projection intrinsically point-symmetric, that it is significantly flattened, with its major axis aligned along the Galactic Plane, and that it is centred on the black hole, Sagittarius A*. Its density follows the well known approximate {rho}{prop.to}r^-2^-law at distances of a few parsecs from Sagittarius A*, but becomes as steep as about {rho}{prop.to}r^-3^ at projected radii around 5pc. We derive a half light radius of 4.2+/-0.4pc, a total luminosity of L_MWNSC,4.5{mu}m_=4.1+/-0.4x10^7^L_{sun}_, and a mass of M_MWNSC_=2.1+/-0.4x10^7^M_{sun}_. The overall properties of the MWNSC agree well with the ones of its extragalactic counterparts, which underlines its role as a template for these objects. Its flattening agrees well with its previously established rotation parallel to Galactic rotation and suggests that it has formed by accretion of material that fell in preferentially along the Galactic Plane. Our findings support the in situ growth scenario for nuclear clusters and emphasize the need to increase the complexity of theoretical models for their formation and for the interaction between their stars and the central black hole in order to include rotation, axisymmetry, and growth in recurrent episodes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/488/1141
- Title:
- Milky Way Project DR2 bubbles & bow shocks
- Short Name:
- J/MNRAS/488/1141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Citizen science has helped astronomers comb through large data sets to identify patterns and objects that are not easily found through automated processes. The Milky Way Project (MWP), a citizen science initiative on the Zooniverse platform, presents internet users with infrared (IR) images from Spitzer Space Telescope Galactic plane surveys. MWP volunteers make classification drawings on the images to identify targeted classes of astronomical objects. We present the MWP second data release (DR2) and an updated data reduction pipeline written in Python. We aggregate 3 million classifications made by MWP volunteers during the years 2012-2017 to produce the DR2 catalogue, which contains 2600 IR bubbles and 599 candidate bow-shock driving stars. The reliability of bubble identifications, as assessed by comparison to visual identifications by trained experts and scoring by a machine-learning algorithm, is found to be a significant improvement over DR1. We assess the reliability of IR bow shocks via comparison to expert identifications and the colours of candidate bow-shock driving stars in the 2MASS point-source catalogue. We hence identify highly-reliable subsets of 1394 DR2 bubbles and 453 bow-shock driving stars. Uncertainties on object coordinates and bubble size/shape parameters are included in the DR2 catalog. Compared with DR1, the DR2 bubbles catalogue provides more accurate shapes and sizes. The DR2 catalogue identifies 311 new bow shock driving star candidates, including three associated with the giant HII regions NGC 3603 and RCW 49.
- ID:
- ivo://CDS.VizieR/J/ApJS/161/361
- Title:
- Millimeter continuum survey for protoclusters
- Short Name:
- J/ApJS/161/361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our search for the earliest stages of massive star formation turned up 12 massive pre-protocluster candidates plus a few protoclusters. For this search, we selected 47 FIR-bright IRAS sources in the outer Galaxy. We mapped regions of several square arcminutes around the IRAS source in the millimeter continuum in order to find massive cold cloud cores possibly being in a very early stage of massive star formation. Masses and densities are derived for the 128 molecular cloud cores found in the obtained maps.
- ID:
- ivo://CDS.VizieR/J/A+A/390/501
- Title:
- Millimetre observations of carbon stars. I.
- Short Name:
- J/A+A/390/501
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Millimetre observations of IRAS selected red carbon stars are presented. About 260 stars have been observed with SEST and IRAM in the CO (1-0) and CO (2-1) lines and partially in HCN (1-0) and SiO (3-2). An overall detection rate, in at least one line, of about 80% is achieved. The survey represents the second largest survey for AGB stars, and the largest ever for carbon stars. Two new detections in SiO (3-2) in carbon stars are reported. When available, the SiO/HCN and HCN/CO(1-0) line ratios are consistent with the ratios expected for carbon stars.
- ID:
- ivo://CDS.VizieR/J/A+A/390/511
- Title:
- Millimetre observations of carbon stars. II.
- Short Name:
- J/A+A/390/511
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dust- and gas mass loss rates and distances are determined for a sample of about 330 infra-red carbon stars that probe a distance up to about 5.5kpc. The dependence of the dust- and gas mass loss rates, and the expansion velocity upon galactic longitude (l) are studied. It is found that the expansion velocity significantly depends on l, but that the absolute bolometric magnitude, the dust mass loss rate and the gas-to-dust ratio depend on l marginally, if at all, and the gas mass loss rate does not depend on l. Beyond the solar circle, the expansion velocity (as well as the luminosity, dust-to-gas ratio, dust mass loss rate) is lower than inside the solar circle, as expected from the overall gradient in metallicity content of the Galaxy. Combining the average expansion velocity inside and beyond the solar circle with the theoretically predicted relation between expansion velocity and gas-to-dust ratio, we find that the metallicity gradient in the solar neighbourhood is about -0.034dex/kpc, well within the quoted range of values in the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/488/579
- Title:
- Millimetric maps of IRAS 18151-1208
- Short Name:
- J/A+A/488/579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of physical and chemical properties of massive protostars is critical to better understand the evolutionary sequence which leads to the formation of high-mass stars. IRAS 18151-1208 is a nearby massive region (d=3kpc, L~2x10^4^L_{sun}_) which splits into three cores : MM1, MM2 and MM3 (separated by 1arcmin-2arcmin). We aim at (1) studying the physical and chemical properties of the individual MM1, MM2 and MM3 cores; (2) deriving their evolutionary stages; (3) using these results to improve our view of the evolutionary sequence of massive cores. The region was observed in the CS, C^34^S, H_2_CO, HCO^+^ H^13^CO^+^, and N_2_H^+^ lines at mm wavelengths with the IRAM 30m and Mopra telescopes. We use 1D and 2D modeling of the dust continuum to derive the density and temperature distributions, which are then used in the RATRAN code to model the lines and constrain the abundances of the observed species. All the lines were detected in MM1 and MM2. MM3 shows weaker emission, or even is undetected in HCO^+^ and all isotopic species. MM2 is driving a newly discovered CO outflow and hosts a mid-IR-quiet massive protostar. The abundance of CS is significantly larger in MM1 than in MM2, but smaller than in a reference massive protostar such as AFGL 2591. In contrast the N_2_H^+^ abundance decreases from MM2 to MM1, and is larger than in AFGL 2591. Both MM1 and MM2 host an early phase massive protostar, but MM2 (and mid-IR-quiet sources in general) is younger and more dominated by the host protostar than MM1 (mid-IR-bright). The MM3 core is probably in a pre-stellar phase. We find that the N_2_H^+^/C^34^S ratio varies systematically with age in the massive protostars for which the data are available. It can be used to identify young massive protostars.
