- ID:
- ivo://CDS.VizieR/J/MNRAS/455/370
- Title:
- Predicted LIR for SDSS galaxies
- Short Name:
- J/MNRAS/455/370
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The total infrared (IR) luminosity (L_IR_) can be used as a robust measure of a galaxy's star formation rate (SFR), even in the presence of an active galactic nucleus (AGN), or when optical emission lines are weak. Unfortunately, existing all sky far-IR surveys, such as the Infrared Astronomical Satellite (IRAS) and AKARI, are relatively shallow and are biased towards the highest SFR galaxies and lowest redshifts. More sensitive surveys with the Herschel Space Observatory are limited to much smaller areas. In order to construct a large sample of L_IR_ measurements for galaxies in the nearby Universe, we employ artificial neural networks (ANNs), using 1136 galaxies in the Herschel Stripe 82 sample as the training set. The networks are validated using two independent data sets (IRAS and AKARI) and demonstrated to predict the L_IR_ with a scatter {sigma}~0.23dex, and with no systematic offset. Importantly, the ANN performs well for both star-forming galaxies and those with an AGN. A public catalogue is presented with our L_IR_ predictions which can be used to determine SFRs for 331926 galaxies in the Sloan Digital Sky Survey (SDSS), including ~129000 SFRs for AGN-dominated galaxies for which SDSS SFRs have large uncertainties.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/651/A55
- Title:
- Predicted redshifts of galaxies with NetZ
- Short Name:
- J/A+A/651/A55
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The redshifts of galaxies are a key attribute that is needed for nearly all extragalactic studies. Since spectroscopic redshifts require additional telescope and human resources, millions of galaxies are known without spectroscopic redshifts. Therefore, it is crucial to have methods for estimating the redshift of a galaxy based on its photometric properties, the so-called photo-z. We developed NetZ, a new method using a Convolutional Neural Network (CNN) to predict the photo-z based on galaxy images, in contrast to previous methods which often used only the integrated photometries of galaxies without their images. We use data from the Hyper Suprime-Cam Subaru Strategic Program (HSC SSP) in five different filters as training data. The network over the whole redshift range between 0 and 4 performs well overall and especially in the high-z range better than other methods on the same data. We obtain an accuracy |zpred-zref| of sigma=0.12 (68% confidence interval) with a CNN working for all galaxy types averaged over all galaxies in the redshift range of 0 to ~4. By limiting to smaller redshift ranges or to Luminous Red Galaxies (LRGs), we find a further notable improvement. We publish more than 34 million new photo-z values predicted with NetZ here. This shows that the new method is very simple and fast to apply, and, importantly, covers a wide redshift range limited only by the available training data. It is broadly applicable and beneficial to imaging surveys, particularly upcoming surveys like the Rubin Observatory Legacy Survey of Space and Time which will provide images of billions of galaxies with similar image quality as HSC.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A157
- Title:
- Probing star formation and ISM properties. II
- Short Name:
- J/A+A/616/A157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We evaluate dust-corrected far-ultraviolet (FUV) star formation rates (SFRs) for samples of star-forming galaxies at z~0 and z~0.7 and find significant differences between values obtained through corrections based on UV colour, from a hybrid mid-infrared (MIR) plus FUV relation, and from a radiative transfer based attenuation correction method. The performances of the attenuation correction methods are assessed by their ability to remove the dependency of the corrected SFR on inclination, as well as returning, on average, the expected population mean SFR. We find that combining MIR (rest-frame ~13um) and FUV luminosities gives the most inclination-independent SFRs and reduces the intrinsic SFR scatter of the methods we tested. However, applying the radiative transfer based method gives corrections to the FUV SFR that are inclination independent and in agreement with the expected SFRs at both z~0 and z~0.7. SFR corrections based on the UV-slope perform worse than the other two methods we tested. For our local sample, the UV-slope method works on average, but does not remove inclination biases. At z~0.7, we find that the UV-slope correction we used locally flattens the inclination dependence compared to the raw FUV measurements, but was not sufficient to correct for the large attenuation observed at z~0.7.
- ID:
- ivo://CDS.VizieR/J/ApJ/800/120
- Title:
- Profiles of z<0.5 galaxies with Pan-STARRS1
- Short Name:
- J/ApJ/800/120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an analysis of Pan-STARRS1 Medium Deep Survey multi-band (grizy) images of a sample of 698 low-redshift disk galaxies that span broad ranges in stellar mass, star-formation rate, and bulge/disk ratio. We use population synthesis spectral energy distribution fitting techniques to explore the radial distribution of the light, color, surface mass density, mass/light ratio, and age of the stellar populations. We characterize the structure and stellar content of the galaxy disks out to radii of about twice Petrosian r_90_, beyond which the halo light becomes significant. We measure normalized radial profiles for sub-samples of galaxies in three bins each of stellar mass and concentration. We also fit radial profiles to each galaxy. The majority of galaxies have down-bending radial surface brightness profiles in the bluer bands with a break radius at roughly r_90_. However, they typically show single unbroken exponentials in the reddest bands and in the stellar surface mass density. We find that the mass/light ratio and stellar age radial profiles have a characteristic "U" shape. There is a good correlation between the amplitude of the down-bend in the surface brightness profile and the rate of the increase in the M/L ratio in the outer disk. As we move from late- to early-type galaxies, the amplitude of the down-bend and the radial gradient in M/L both decrease. Our results imply a combination of stellar radial migration and suppression of recent star formation can account for the stellar populations of the outer disk.
- ID:
- ivo://CDS.VizieR/J/AJ/149/42
- Title:
- Proper motion of Draco dwarf galaxy from HST
- Short Name:
- J/AJ/149/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured the proper motion of the Draco dwarf galaxy using images at two epochs with a time baseline of about two years taken with the Hubble Space Telescope Advanced Camera for Surveys. Wide Field Channels 1 and 2 provide two adjacent fields, each containing a known QSO. The zero point for the proper motion is determined using both background galaxies and the QSOs and the two methods produce consistent measurements within each field. Averaging the results from the two fields gives a proper motion in the equatorial coordinate system of ({mu}_{alpha}_,{mu}_{delta}_)=(-17.7+/-6.3,-22.1+/-6.3)mas/century and in the Galactic coordinate system of ({mu}_l_,{mu}_b_)=(-23.1+/-6.3,-16.3+/-6.3)mas/century. Removing the contributions of the motion of the Sun and of the LSR to the measured proper motion yields a Galactic rest-frame proper motion of ({mu}_{alpha}_^Grf^,({mu}_{delta}_^Grf^)=(51.4+/-6.3,-18.7+/-6.3)mas/century and ({mu}_l_^Grf^,({mu}_b_^Grf^)=(-21.8+/-6.3,-50.1+/-6.3)mas/century. The implied space velocity with respect to the Galactic center is ({Pi},{Theta},Z)=27+/-14,89+/-25,-212+/-20)km/s. This velocity implies that the orbital inclination is 70{deg}, with a 95% confidence interval of (59{deg},80{deg}), and that the plane of the orbit is consistent with that of the vast polar structure (VPOS) of Galactic satellite galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/595/L2
- Title:
- Proper motions in NGC6681 globular cluster
- Short Name:
- J/A+A/595/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For the first time the astrometric capabilities of the MCAO facility GeMS with the GSAOI camera on Gemini-South are tested to quantify the accuracy in determining stellar proper motions in the Galactic globular cluster NGC 6681. Proper motions from HST/ACS for a sample of its stars are already available, and this allows us to construct a distortion-free reference at the epoch of GeMS observations that is used to measure and correct the temporally changing distortions for each GeMS exposure. In this way, we are able to compare the corrected GeMS images with a first-epoch of HST/ACS images to recover the relative proper motion of the Sagittarius dwarf spheroidal galaxy with respect to NGC 6681. We find this to be (pm_{alpha}_cos{delta}, pm_{delta}_)=(4.09,-3.41)mas/yr, which matches previous HST/ACS measurements with a very good accuracy of 0.03mas/yr and with a comparable precision (r.m.s of 0.43mas/yr). This study successfully demonstrates that high-quality proper motions can be measured for quite large fields of view (85arcsecx85arcsec) with MCAO-assisted, ground-based cameras and provides a first, successful test of the performances of GeMS on multi-epoch data.
- ID:
- ivo://CDS.VizieR/J/ApJ/741/100
- Title:
- Proper motions of Leo II member stars
- Short Name:
- J/ApJ/741/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use 14 year baseline images obtained with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope (HST) to derive a proper motion for one of the Milky Way's most distant dwarf spheroidal companions, Leo II, relative to an extragalactic background reference frame. Astrometric measurements are performed in the effective point-spread function formalism using our own developed code. An astrometric reference grid is defined using 3224 stars that are members of Leo II and brighter than a magnitude of 25 in the F814W band. We identify 17 compact extragalactic sources, for which we measure a systemic proper motion relative to this stellar reference grid. We derive a proper motion [{mu}_{alpha}_,{mu}_{delta}_]=[+104+/-113,-33+/-151]uas/yr for Leo II in the heliocentric reference frame. Though marginally detected, the proper motion yields constraints on the orbit of Leo II. Given a distance of d~230kpc and a heliocentric radial velocity v_r_=+79km/s, and after subtraction of the solar motion, our measurement indicates a total orbital motion v_G_=266.1+/-128.7km/s in the Galactocentric reference frame, with a radial component v_rG_=21.5+/-4.3km/s and tangential component v_tG_=265.2+/-129.4km/s. The small radial component indicates that Leo II either has a low-eccentricity orbit or is currently close to perigalacticon or apogalacticon distance. We see evidence for systematic errors in the astrometry of the extragalactic sources which, while close to being point sources, are slightly resolved in the HST images. We provide a detailed catalog of the stellar and extragalactic sources identified in the HST data which should provide a solid early-epoch reference for future astrometric measurements.
- ID:
- ivo://CDS.VizieR/J/ApJ/875/77
- Title:
- Proper motions of MW satellites with Gaia & DES
- Short Name:
- J/ApJ/875/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new, probabilistic method for determining the systemic proper motions of Milky Way (MW) ultra-faint satellites in the Dark Energy Survey (DES). We utilize the superb photometry from the first public data release (DR1) of the DES to select candidate members and cross-match them with the proper motions from the Gaia DR2. We model the candidate members with a mixture model (satellite and MW) in spatial and proper motion space. This method does not require prior knowledge of satellite membership and can successfully determine the tangential motion of 13 DES satellites. With our method, we present measurements of the following satellites: Columba I, Eridanus III, Grus II, Phoenix II, Pictor I, Reticulum III, and Tucana IV. This is the first systemic proper motion measurement for several of these satellites, and the majority lack extensive spectroscopic follow-up studies. We compare these to the predictions of Large Magellanic Cloud satellites and the vast polar structure. With the high-precision DES photometry, we conclude that most of the newly identified member stars are very metal-poor ([Fe/H]<=-2), similar to other ultra-faint dwarf galaxies, while Reticulum III is likely more metal-rich. We also find potential members in the following satellites that might indicate their overall proper motion: Cetus II, Kim 2, and Horologium II. However, due to the small number of members in each satellite, spectroscopic follow-up observations are necessary to determine the systemic proper motion in these satellites.
- ID:
- ivo://CDS.VizieR/J/AJ/129/2119
- Title:
- Properties for 165 dwarf galaxies
- Short Name:
- J/AJ/129/2119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive inner dark matter halo density profiles for a sample of 165 low-mass galaxies using rotation curves obtained from high-quality, long-slit optical spectra assuming minimal disks and spherical symmetry.
- ID:
- ivo://CDS.VizieR/J/AJ/143/83
- Title:
- Properties of a sample of Seyfert 1 galaxies
- Short Name:
- J/AJ/143/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a statistical study of a large, homogeneously analyzed sample of narrow-line Seyfert 1 (NLS1) galaxies, accompanied by a comparison sample of broad-line Seyfert 1 (BLS1) galaxies. Optical emission-line and continuum properties are subjected to correlation analyses, in order to identify the main drivers of the correlation space of active galactic nuclei (AGNs), and of NLS1 galaxies in particular. For the first time, we have established the density of the narrow-line region as a key parameter in Eigenvector 1 space, as important as the Eddington ratio L/L_Edd_. This is important because it links the properties of the central engine with the properties of the host galaxy, i.e., the interstellar medium (ISM). We also confirm previously found correlations involving the line width of H{beta} and the strength of the Fe II and [O III]{lambda}5007 emission lines, and we confirm the important role played by L/L_Edd_ in driving the properties of NLS1 galaxies. A spatial correlation analysis shows that large-scale environments of the BLS1 and NLS1 galaxies of our sample are similar. If mergers are rare in our sample, accretion-driven winds, on the one hand, or bar-driven inflows, on the other hand, may account for the strong dependence of Eigenvector 1 on ISM density.
