- ID:
- ivo://CDS.VizieR/J/ApJ/883/128
- Title:
- alpha & Fe abundances in the giant stellar stream
- Short Name:
- J/ApJ/883/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first measurements of [Fe/H] and [{alpha}/Fe] abundances, obtained using spectral synthesis modeling, for red giant branch stars in M31's giant stellar stream (GSS). The spectroscopic observations, obtained at a projected distance of 17kpc from M31's center, yielded 61 stars with [Fe/H] measurements, including 21 stars with [{alpha}/Fe] measurements, from 112 targets identified as M31 stars. The [Fe/H] measurements confirm the expectation from photometric metallicity estimates that stars in this region of M31's halo are relatively metal rich compared to stars in the Milky Way's inner halo: more than half the stars in the field, including those not associated with kinematically identified substructure, have [Fe/H] abundances >-1.0. The stars in this field are {alpha}-enhanced at lower metallicities, while [{alpha}/Fe] decreases with increasing [Fe/H] above metallicities of [Fe/H]>~-0.9. Three kinematical components have been previously identified in this field: the GSS, a second kinematically cold feature of unknown origin, and M31's kinematically hot halo. We compare probabilistic [Fe/H] and [{alpha}/Fe] distribution functions for each of the components. The GSS and the second kinematically cold feature have very similar abundance distributions, while the halo component is more metal poor. Although the current sample sizes are small, a comparison of the abundances of stars in the GSS field with abundances of M31 halo and dSph stars from the literature indicate that the progenitor of the stream was likely more massive, and experienced a higher efficiency of star formation, than M31's existing dSphs or the dEs NGC147 and NGC185.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/643/A4
- Title:
- ALPINE-ALMA [CII] survey. IR luminosity
- Short Name:
- J/A+A/643/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present dust attenuation properties of spectroscopically confirmed star forming galaxies on the main sequence at a redshift of ~4.4-5.8. Our analyses are based on the far infrared continuum observations of 118 galaxies at rest-frame 158 {mu}m obtained with the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [CII] at Early times (ALPINE). We study the connection between the ultraviolet (UV) spectral slope ({beta}), stellar mass (M*), and infrared excess (IRX=L_IR_/L_UV_). Twenty-three galaxies are individually detected in the continuum at > 3.5{sigma} significance. We perform a stacking analysis using both detections and nondetections to study the average dust attenuation properties at z~4.4-5.8. The individual detections and stacks show that the IRX-{beta} relation at z~5 is consistent with a steeper dust attenuation curve than typically found at lower redshifts (z<4). The attenuation curve is similar to or even steeper than that of the extinction curve of the Small Magellanic Cloud. This systematic change of the IRX-{beta} relation as a function of redshift suggests an evolution of dust attenuation properties at z>4. Similarly, we find that our galaxies have lower IRX values, up to 1dex on average, at a fixed mass compared to previously studied IRX-M* relations at z<=4, albeit with significant scatter. This implies a lower obscured fraction of star formation than at lower redshifts. Our results suggest that dust properties of UV-selected star forming galaxies at z>=4 are characterised by (i) a steeper attenuation curve than at z<=4, and (ii) a rapidly decreasing dust obscured fraction of star formation as a function of redshift. Nevertheless, even among this UV-selected sample, massive galaxies (logM*/M_{sun}_>10) at z~5-6 already exhibit an obscured fraction of star formation of ~45%, indicating a rapid build-up of dust during the epoch of reionization.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A2
- Title:
- ALPINE DR1 merged catalog
- Short Name:
- J/A+A/643/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ALPINE-ALMA large program targets the [CII] 158um line and the far-infrared continuum in 118 spectroscopically confirmed star-forming galaxies between z=4.4 and z=5.9. It represents the first large [CII] statistical sample built in this redshift range. We present details of the data processing and the construction of the catalogs. We detected 23 of our targets in the continuum. To derive accurate infrared luminosities and obscured star formation rates, we measured the conversion factor from the ALMA 158um rest-frame dust continuum luminosity to the total infrared luminosity (LIR) after constraining the dust spectral energy distribution by stacking a photometric sample similar to ALPINE in ancillary single-dish far-infrared data. We found that our continuum detections have a median LIR of 4.4x10^11^L_{sun}_. We also detected 57 additional continuum sources in our ALMA pointings. They are at lower redshift than the ALPINE targets, with a mean photometric redshift of 2.5+/-0.2. We measured the 850um number counts between 0.35 and 3.5mJy, improving the current interferometric constraints in this flux density range. We found a slope break in the number counts around 3mJy with a shallower slope below this value. More than 40% of the cosmic infrared background is emitted by sources brighter than 0.35mJy. Finally, we detected the [CII] line in 75 of our targets. Their median [CII] luminosity is 4.8x108L_{sun}_ and their median full width at half maximum is 252km/s. After measuring the mean obscured SFR in various [CII] luminosity bins by stacking ALPINE continuum data, we find a good agreement between our data and the local and predicted SFR-L[CII] relations of De Looze et al. (2014A&A...568A..62D) and Lagache et al. (2018A&A...609A.130L).
- ID:
- ivo://CDS.VizieR/J/ApJS/126/85
- Title:
- A mid-infrared galaxy atlas (MIGA)
- Short Name:
- J/ApJS/126/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A mid-infrared atlas of part of the Galactic plane (75{deg}<l<148{deg}, b=+/-6{deg}) has been constructed using HIRES processed infrared data to provide a mid-infrared data set for the Canadian Galactic Plane Survey (CGPS). The addition of this data set to the CGPS will enable the study of the emission from the smallest components of interstellar dust at an angular resolution comparable to that of the radio, millimeter, and far-infrared data in the CGPS. The Mid-Infrared Galaxy Atlas (MIGA) is a mid-infrared (12 and 25um) counterpart to the far-infrared IRAS Galaxy Atlas (IGA), and consists of resolution enhanced (~0.5' resolution) HIRES images along with ancillary maps. This paper describes the processing and characteristics of the atlas, the cross-band simulation technique used to obtain high-resolution ratio maps, and future plans to extend both the IGA and MIGA.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/325
- Title:
- 452 AMIGA galaxies physical parameters
- Short Name:
- J/MNRAS/434/325
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Disentangling processes governing the formation and evolution of galaxies is a fundamental challenge in extragalactic research. In this sense the current belief that galaxies grow by the action of minor mergers makes the study of the stellar mass-size relation in different environments an important tool for distinguishing effects of internal and external processes. The aim of this work is to study the effects of environment on the growth in size of galaxies. As part of AMIGA project (Analysis of the Interstellar Medium of Isolated GAlaxies), we examine the stellar mass-size relation for a sample of the most isolated galaxies in the local Universe interpreted as stellar systems where evolution has been mainly governed by internal processes. Effects of environment on the stellar mass-size relation are evaluated by comparing our results with samples of less isolated early- and late-type galaxies, as well as, for the first time, different spiral subtypes. Stellar masses in our sample were derived by fitting the SED of each galaxy with kcorrect. We used two different size estimators, the half-light radius obtained with SExtractor and the effective radius calculated by fitting a Sersic profile to the i-band image of each galaxy using GALFIT.We found good agreement between those size estimators when the Sersic index fell in the range 2.5<n<4.5 and 0.5<n<2.5 for (visually classified) early- and late-type galaxies respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/L39
- Title:
- AMIGA galaxies structural parameters
- Short Name:
- J/ApJ/788/L39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present structural parameters and (g-i) bulge/disk colors for a large sample (189) of isolated AMIGA galaxies. The structural parameters of bulges were derived from the two-dimensional bulge/disk/bar decomposition of Sloan Digital Sky Survey i-band images using GALFIT. Galaxies were separated between classical bulges (n_b_>2.5) and pseudobulges (n_b_<2.5), resulting in a dominant pseudobulge population (94%) with only 12 classical bulges. In the <{mu}_e_>-R_e_plane, pseudobulges are distributed below the elliptical relation (smaller R_e_ and fainter {mu}_e_), with the closest region to the Kormendy relation populated by those pseudobulges with larger values of B/T. We derived (g-i) bulge colors using aperture photometry and find that pseudobulges show median colors (g-i)_b_~1.06, while their associated disks are much bluer, (g-i)_d_~0.77. Moreover, 64% (113/177) of pseudobulges follow the red sequence of early-type galaxies. Bluer pseudobulges tend to be located in galaxies with the highest likelihood of tidal perturbation. The red bulge colors and low B/T values for AMIGA isolated galaxies are consistent with an early formation epoch and not much subsequent growth. Properties of bulges in isolated galaxies contrast with a picture where pseudobulges grow continuously via star formation. They also suggest that environment could be playing a role in rejuvenating the pseudobulges.
157. AMIGA III. IRAS data
- ID:
- ivo://CDS.VizieR/J/A+A/462/507
- Title:
- AMIGA III. IRAS data
- Short Name:
- J/A+A/462/507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the mid- (MIR) and far- (FIR) infrared properties of a large (~1000) sample of the most isolated galaxies in the local Universe. This sample is intended as a "nurture-free" zero point against which more environmentally influenced samples can be compared. We reprocess IRAS MIR/FIR survey data using the ADDSCAN/SCANPI utility for 1030 out of 1050 galaxies from the Catalogue of Isolated Galaxies (CIG, Cat. <VII/82>) as part of the AMIGA survey. We focus on diagnostics (FIR luminosity LFIR , R=log(LFIR/LB) and IRAS colours) thought to be sensitive to effects of environment or interaction.
- ID:
- ivo://CDS.VizieR/J/A+A/449/937
- Title:
- AMIGA. II. Morphological refinement
- Short Name:
- J/A+A/449/937
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a refinement of the optical morphologies for galaxies in the Catalog of Isolated Galaxies (Karachentseva et al., 1973, Cat. <VII/82>) that forms the basis of the AMIGA (Analysis of the interstellar Medium of Isolated GAlaxies) project. Uniform reclassification using the digitized POSS II data benefited from the high resolution and dynamic range of that sky survey. Comparison with independent classifications made for an SDSS overlap sample of more than 200 galaxies confirms the reliability of the early vs. late-type discrimination and the accuracy of spiral subtypes within {Delta}T=1-2. CCD images taken at the Observatorio de Sierra Nevada (OSN) were also used to solve ambiguities in early versus late-type classifications. A considerable number of galaxies in the catalog (n=193) are flagged for the presence of nearby companions or signs of distortion likely due to interaction. This most isolated sample of galaxies in the local Universe is dominated by two populations: 1) 82% are spirals (Sa-Sd) with the bulk being luminous systems with small bulges (63% between types Sb-Sc) and 2) a significant population of early-type E-S0 galaxies (14%).
- ID:
- ivo://CDS.VizieR/J/A+A/436/443
- Title:
- AMIGA. I. Velocities of CIG galaxies
- Short Name:
- J/A+A/436/443
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The AMIGA project (Analysis of the Interstellar Medium of Isolated Galaxies) is compiling a multiwavelength database of isolated galaxies that includes optical (B and H{alpha}), infrared (FIR and NIR) and radio (continuum plus HI and CO lines) properties. It involves a refinement of the pioneering Catalog of Isolated Galaxies (<VII/82>). This paper is the first in a series and begins with analysis of the global properties of the nearly redshift-complete Catalog of Isolated Galaxies (CIG) with emphasis on the Optical Luminosity Function (OLF) which we compare with other recent estimates of the OLF for a variety of environments. The CIG redshift distribution for n=956 galaxies re-enforces the evidence for a bimodal structure seen earlier in smaller samples. The peaks at redshift near 1500 and 6000km/s correspond respectively to galaxies in the local supercluster and those in more distant large-scale components (particularly Perseus- Pisces). The two peaks in the redshift distribution are superimposed on 50% or more of the sample that is distributed in a much more homogeneous way. The CIG probably represents the most homogeneous local field example that has ever been compiled. Our derivation of the CIG OLF is consistent with other studies of the OLF for lower density environments. This comparison via the Schechter parameter formalization shows that: 1) M* increases with galaxy surface density on the sky and 2) {alpha} shows a weaker tendency to do the same. The CIG represents the largest and most complete foundation for studies of isolated galaxies and is likely as close as we can come to a field sample.
- ID:
- ivo://CDS.VizieR/J/A+A/470/505
- Title:
- AMIGA IV. Neighbours around CIG galaxies
- Short Name:
- J/A+A/470/505
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studies of the effects of environment on galaxy properties and evolution require well defined control samples. Such isolated galaxy samples have up to now been small or poorly defined. The AMIGA project (Analysis of the interstellar Medium of Isolated GAlaxies) represents an attempt to define a statistically useful sample of the most isolated galaxies in the local (z<0.05) Universe. A suitable large sample for the AMIGA project already exists, the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973; 1050 galaxies, Cat. VII/82), and we use this sample as a starting point to refine and perform a better quantification of its isolation properties. Digitised POSS-I E images were analysed out to a minimum projected radius R<0.5Mpc around 950 CIG galaxies (those within Vr=1500km/s were excluded). We identified all galaxy candidates in each field brighter than B=17.5 with a high degree of confidence using the LMORPHO software. We generated a catalogue of approximately 54000 potential neighbours (redshifts exist for 30% of this sample). 666 galaxies pass and 284 fail the original CIG isolation criterion. The available redshift data confirm that our catalogue involves a largely background population rather than physically associated neighbours. We find that the exclusion of neighbours within a factor of 4 in size around each CIG galaxy, employed in the original isolation criterion, corresponds to {Delta}Vr~18000km/s indicating that it was a conservative limit. Galaxies in the CIG have been found to show different degrees of isolation. We conclude that a quantitative measure of this is mandatory. It will be the subject of future work based on the catalogue of neighbours obtained here.
