- ID:
- ivo://CDS.VizieR/J/A+A/647/A167
- Title:
- Using H-bump to identify RSGs in NGC6822
- Short Name:
- J/A+A/647/A167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a case study in which we used a novel method to identify red supergiant (RSG) candidates in NGC 6822 based on their 1.6um H-bump. We collected 32 bands of photometric data for NGC 6822 ranging from the optical to the mid-infrared (MIR), derived from Gaia, PS1, LGGS, VHS, UKIRT, IRSF, HAWK-I, Spitzer, and WISE. Using the theoretical spectra from MARCS, we demonstrate that there is a prominent difference around 1.6um (H-bump) between targets with high and low surface gravity (HSG and LSG). Taking advantage of this feature, we identify efficient color-color diagrams of rzH (r-z versus z-H) and rzK (r-z versus z-K) to separate HSG (mostly foreground dwarfs) and LSG targets (mainly background red giant stars, asymptotic giant branch stars, and RSGs) from crossmatching of optical and near-infrared (NIR) data. Moreover, synthetic photometry from ATLAS9 gives similar results. We further separated RSG candidates from the remaining LSG candidates as determined by the H-bump method by using semi-empirical criteria on NIR color-magnitude diagrams, where both the theoretic cuts and morphology of the RSG population are considered. This separation produced 323 RSG candidates. The simulation of foreground stars with Besancon models also indicates that our selection criteria are largely free from the contamination of Galactic giants. In addition to the H-bump method, we used the traditional BVR method (B-V versus V-R) as a comparison and/or supplement by applying a slightly aggressive cut to select as many RSG candidates as possible (358 targets). Furthermore, the Gaia astrometric solution was used to constrain the sample, where 181 and 193 targets were selected with the H-bump and BVR method, respectively. The percentages of selected targets in the two methods are similar at ~60%, indicating a comparable accuracy of the two methods. In total, there are 234 RSG candidates after combining targets from the two methods, and 140 (~60%) of them are in common. The final RSG candidates are in the expected locations on the mid-infrared color-magnitude diagram with [3.6]-[4.5]<~0 and J-[8.0]~1.0. The spatial distribution is also coincident with the far-ultraviolet-selected star formation regions, suggesting that the selection is reasonable and reliable. We indicate that our method can also be used to identify other LSG targets, such as red giants and asymptotic giant branch stars, and it can also be applied to most of the nearby galaxies by using recent large-scale ground-based surveys. Future ground- and space-based facilities may promote its application beyond the Local Group.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/164/38
- Title:
- UV and FIR properties of nearby galaxies
- Short Name:
- J/ApJS/164/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work presents the main ultraviolet (UV) and far-infrared (FIR) properties of two samples of nearby galaxies selected from the GALEX ({lambda}=2315{AA}, hereafter NUV) and IRAS ({lambda}=60{mu}m) surveys, respectively. They are built in order to obtain detection at both wavelengths for most of the galaxies. Star formation rate (SFR) estimators based on the UV and FIR emissions are compared. Systematic differences are found between the SFR estimators for individual galaxies based on the NUV fluxes corrected for dust attenuation and on the total IR luminosity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/406/420
- Title:
- UV/far-IR data of infrared excess sources
- Short Name:
- J/MNRAS/406/420
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the nature of Infrared Excess sources (IRX), which are proposed as candidates for luminous [LX(2-10keV)>10^43^erg/s] Compton thick (NH>2x10^24^cm^-2^) QSOs at z~~2. Lower redshift, z~~1, analogues of the distant IRX population are identified by first redshifting to z=2 the spectral energy distributions (SEDs) of all sources with secure spectroscopic redshifts in the AEGIS (6488) and the GOODS-North (1784) surveys and then selecting those that qualify as IRX sources at that redshift. A total of 19 galaxies are selected. The mean redshift of the sample is z~~1. We do not find strong evidence for Compton thick QSOs in the sample. For nine sources with X-ray counterparts, the X-ray spectra are consistent with Compton thin active galactic nucleus (AGN). Only three of them show tentative evidence for Compton thick obscuration. The SEDs of the X-ray undetected population are consistent with starburst activity.
- ID:
- ivo://CDS.VizieR/J/ApJ/879/131
- Title:
- UV-FIR obs. of post-starburst galaxies & dust masses
- Short Name:
- J/ApJ/879/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive dust masses (M_dust_) from the spectral energy distributions of 58 post-starburst galaxies (PSBs). There is an anticorrelation between specific dust mass (M_dust_/M_*_) and the time elapsed since the starburst ended, indicating that dust was either destroyed, expelled, or rendered undetectable over the ~1Gyr after the burst. The M_dust_/M_*_ depletion timescale, 205_-37_^+58^Myr, is consistent with that of the CO-traced M_H2_/M_*_, suggesting that dust and gas are altered via the same process. Extrapolating these trends leads to the M_dust_/M_*_ and M_H2_/M_*_ values of early-type galaxies (ETGs) within 1-2Gyr, a timescale consistent with the evolution of other PSB properties into ETGs. Comparing Mdust and M_H2_ for PSBs yields a calibration, log M_H2_=0.45logM_dust_+6.02, that allows us to place 33 PSBs on the Kennicutt-Schmidt (KS) plane, {Sigma}SFR-{Sigma}M_H2_. Over the first ~200-300Myr, the PSBs evolve down and off of the KS relation, as their star formation rate (SFR) decreases more rapidly than M_H2_. Afterwards, M_H2_ continues to decline whereas the SFR levels off. These trends suggest that the star formation efficiency bottoms out at 10^-11^/yr and will rise to ETG levels within 0.5-1.1Gyr afterwards. The SFR decline after the burst is likely due to the absence of gas denser than the CO-traced H2. The mechanism of the M_dust_/M_*_ and M_H2_/M_*_ decline, whose timescale suggests active galactic nucleus/low-ionization nuclear emission-line region feedback, may also be preventing the large CO-traced molecular gas reservoirs from collapsing and forming denser star-forming clouds.
- ID:
- ivo://CDS.VizieR/J/ApJ/824/70
- Title:
- UV-FIR SED results of SDSS QSOs and their hosts
- Short Name:
- J/ApJ/824/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we present a study of 207 quasars selected from the Sloan Digital Sky Survey quasar catalogs and the Herschel Stripe 82 survey. Quasars within this sample are high-luminosity quasars with a mean bolometric luminosity of 10^46.4^erg/s. The redshift range of this sample is within z Herschel-SPIRE bands, the quasar sample is complete yet highly biased. Based on the multi-wavelength photometric observation data, we conducted a spectral energy distribution (SED) fitting through UV to FIR. Parameters such as active galactic nucleus (AGN) luminosity, far-IR (FIR) luminosity, stellar mass, as well as many other AGN and galaxy properties are deduced from the SED fitting results. The mean star formation rate (SFR) of the sample is 419M_{sun}_/yr and the mean gas mass is ~10^11.3^M_{sun}_. All of these results point to an IR luminous quasar system. Compared with star formation main sequence (MS) galaxies, at least 80 out of 207 quasars are hosted by starburst galaxies. This supports the statement that luminous AGNs are more likely to be associated with major mergers. The SFR increases with the redshift up to z=2. It is correlated with the AGN bolometric luminosity, where L_FIR_{propto}L_Bol_^0.46+/-0.03^. The AGN bolometric luminosity is also correlated with the host galaxy mass and gas mass. Yet the correlation between L_FIR_ and L_Bol_ has higher significant level, implies that the link between AGN accretion and the SFR is more primal. The M_BH_/M_*_ ratio of our sample is 0.02, higher than the value 0.005 in the local universe. It might indicate an evolutionary trend of the M_BH_/M_*_ scaling relation.
- ID:
- ivo://CDS.VizieR/J/ApJS/193/30
- Title:
- UV-to-FIR analysis of sources in the EGS. II.
- Short Name:
- J/ApJS/193/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the ultraviolet to far-infrared photometry already compiled and presented in a companion paper (Barro et al. 2011, Cat. J/ApJS/193/13), we present a detailed spectral energy distribution (SED) analysis of nearly 80000 IRAC 3.6+4.5um selected galaxies in the Extended Groth Strip. We estimate photometric redshifts, stellar masses, and star formation rates (SFRs) separately for each galaxy in this large sample. The catalog includes 76936 sources with [3.6]<=23.75 (85% completeness level of the IRAC survey) over 0.48deg^2^. The typical photometric redshift accuracy is {Delta}z/(1+z)=0.034, with a catastrophic outlier fraction of just 2%. We quantify the systematics introduced by the use of different stellar population synthesis libraries and initial mass functions in the calculation of stellar masses. We find systematic offsets ranging from 0.1 to 0.4dex, with a typical scatter of 0.3dex. We also provide UV- and IR-based SFRs for all sample galaxies, based on several sets of dust emission templates and SFR indicators. We evaluate the systematic differences and goodness of the different SFR estimations using the deep FIDEL 70um data available in the Extended Groth Strip. Typical random uncertainties of the IR-bases SFRs are a factor of two, with non-negligible systematic effects at z>~1.5 observed when only MIPS 24um data are available.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A142
- Title:
- UV-to-IR fluxes of Hickson compact groups
- Short Name:
- J/A+A/533/A142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive study on the impact of the environment of compact galaxy groups on the evolution of their members using a multi-wavelength analysis, from the UV to the infrared, for a sample of 32 Hickson compact groups (HCGs) containing 135 galaxies. Fitting the SEDs of all galaxies with the state-of-the-art model of da Cunha (2008MNRAS.388.1595D) we can accurately calculate their mass, SFR, and extinction, as well as estimate their infrared luminosity and dust content. We compare our findings with samples of field galaxies, early-stage interacting pairs, and cluster galaxies with similar data. We find that classifying the groups as dynamically "old" or "young", depending on whether or not at least one quarter of their members are early-type systems, is physical and consistent with past classifications of HCGs based on their atomic gas content. Dynamically "old" groups are more compact and display higher velocity dispersions than "young" groups. Late-type galaxies in dynamically "young" groups have specific star formation rates (sSFRs), NUV-r, and mid-infrared colors which are similar to those of field and early stage interacting pair spirals. Late-type galaxies in dynamically "old" groups have redder NUV-r colors, as they have likely experienced several tidal encounters in the past building up their stellar mass, and display lower sSFRs. We identify several late-type galaxies which have sSFRs and colors similar to those of elliptical galaxies, since they lost part of their gas due to numerous interactions with other group members. Also, 25% of the elliptical galaxies in these groups have bluer UV/optical colors than normal ellipticals in the field, probably due to star formation as they accreted gas from other galaxies of the group, or via merging of dwarf companions. Finally, our SED modeling suggests that in 13 groups, 10 of which are dynamically "old", there is diffuse cold dust in the intragroup medium. All this evidence point to an evolutionary scenario in which the effects of the group environment and the properties of the galaxy members are not instantaneous. Early on, the influence of close companions to group galaxies is similar to the one of galaxy pairs in the field. However, as the time progresses, the effects of tidal torques and minor merging, shape the morphology and star formation history of the group galaxies, leading to an increase of the fraction of early-type members and a rapid built up of the stellar mass in the remaining late-type galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/134/2099
- Title:
- Variability of point sources in infrared
- Short Name:
- J/AJ/134/2099
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a list of 552 sources with suspected variability, based on a comparison of mid-infrared photometry from the GLIMPSE I and Midcourse Space Experiment (MSX) surveys, which were carried out nearly a decade apart. We were careful to address issues such as the difference in resolution and sensitivity between the two surveys, as well as the differences in the spectral responses of the instruments. We selected only sources where the IRAC 8.0um and MSX 8.28um fluxes differ by more than a factor of 2, in order to minimize contamination from sources where the difference in fluxes at 8um is due to a strong 10um silicate feature. We present a subset of 40 sources for which additional evidence suggests variability, using 2MASS and MIPSGAL data. Based on a comparison with the variability flags in the IRAS and MSX point-source catalogs we estimate that at least a quarter of the 552 sources and at least half of the 40 sources in the subset are truly variable. In addition, we tentatively confirm the variability of one source using multiepoch IRAS LRS spectra. We suggest that most of the sources in our list are likely to be asymptotic giant branch stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/731/97
- Title:
- Variable AGNs in GOODS fields
- Short Name:
- J/ApJ/731/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify 85 variable galaxies in the GOODS North and South fields using five epochs of Hubble Space Telescope Advance Camera for Survey V-band (F606W) images spanning 6 months. The variables are identified through significant flux changes in the galaxy's nucleus and represent ~2% of the survey galaxies. With the aim of studying the active galaxy population in the GOODS fields, we compare the variability-selected sample with X-ray and mid-IR active galactic nucleus (AGN) candidates. Forty-nine percent of the variables are associated with X-ray sources identified in the 2Ms Chandra surveys. Twenty-four percent of X-ray sources likely to be AGNs are optical variables and this percentage increases with decreasing hardness ratio of the X-ray emission. Stacking of the non-X-ray-detected variables reveals marginally significant soft X-ray emission. Forty-eight percent of mid-IR power-law sources are optical variables, all but one of which is also X-ray detected. Thus, about half of the optical variables are associated with either X-ray or mid-IR power-law emission. The slope of the power-law fit through the Spitzer IRAC bands indicates that two-thirds of the variables have BLAGN-like spectral energy distributions. Among those galaxies spectroscopically identified as AGNs, we observe variability in 74% of broad-line AGNs and 15% of NLAGNs. The variables are found in galaxies extending to z~3.6.
- ID:
- ivo://CDS.VizieR/J/A+A/267/515
- Title:
- Very cold C-rich circumstellar envelopes
- Short Name:
- J/A+A/267/515
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper develops a method for identification of very cold C-rich circumstellar envelopes (CSEs) in IR regions colder than region VII (i.e., larger value of IRAS flux ratio S25/S12), by reviewing the different criteria and by identifying C-rich CSEs in a sample of 228 bright IRAS sources. By using the results of OH surveys and catalogs together with the results of additional HCN/CO millimeter observations performed on critical classes of objects, a C/O classification is proposed for 94 percent of the sources with a good probability. It is shown that the low-resolution spectra by themselves are a reasonable and easy way to identify C-rich late AGB CSEs. For post-AGB object with cold CSEs, HCN and OH observations or visible/near IR spectroscopy are necessary.
