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1621. HST imaging of Pisces A and B
ID:
ivo://CDS.VizieR/J/ApJ/827/89
Title:
HST imaging of Pisces A and B
Short Name:
J/ApJ/827/89
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present observations of the Pisces A and B galaxies with the Advanced Camera for Surveys on the Hubble Space Telescope. Photometry from these images clearly resolves a red giant branch (RGB) for both objects, demonstrating that they are nearby dwarf galaxies. We describe a Bayesian inferential approach to determining the distance to these galaxies using the magnitude of the tip of the RGB (TRGB), and then apply this approach to these galaxies. This reveals the distance to these galaxies as 5.64_-0.15_^+0.13^Mpc and 8.89_-0.85_^+0.75^Mpc for Pisces A and B, respectively, placing both within the Local Volume but not the Local Group (LG). We estimate the star formation histories of these galaxies, which suggests that they have recently undergone an increase in their star formation rates. Together these yield luminosities for Pisces A and B of M_V_=-11.57_-0.05_^+0.06^ and -12.9+/-0.2, respectively, and estimated stellar masses of log(M*/M_{sun})=7.0_-1.7_^+0.4^ and 7.5_-1.8_^+0.3^. We further show that these galaxies are likely at the boundary between nearby voids and higher-density filamentary structure. This suggests that they are entering a higher-density region from voids, where they would have experienced delayed evolution, consistent with their recent increased star formation rates. If this is indeed the case, they are useful for study as proxies of the galaxies that later evolved into typical LG satellite galaxies.
1622. HST K-selected extremely red galaxies
ID:
ivo://CDS.VizieR/J/ApJ/586/765
Title:
HST K-selected extremely red galaxies
Short Name:
J/ApJ/586/765
Date:
21 Oct 2021
Publisher:
CDS
Description:
We selected 115 extremely red objects (EROs) from deep Hubble Space Telescope (HST) WFPC2 archive data combined with ground-based K-band images, with (F814W-Ks)>=4, K-band signal-to-noise ratio >=5, and a median limiting Ks magnitude of ~18.7, over a corresponding area of 228 arcmin2, for a morphological study of the ERO galaxy population. The survey covered a total of ~409-arcmin^2^ over 77 separate WFPC2 fields. This is the first complete sample of bright EROs with high-resolution HST morphologies.
1623. HST/NICMOS observations of bright IR galaxies
ID:
ivo://CDS.VizieR/J/ApJ/730/125
Title:
HST/NICMOS observations of bright IR galaxies
Short Name:
J/ApJ/730/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new results on the physical nature of infrared-luminous sources at 0.5<z<2.8 as revealed by HST/NICMOS imaging and Infrared Spectrograph mid-infrared spectroscopy. Our sample consists of 134 galaxies selected at 24um with a flux of S(24um)>0.9mJy. We find many (~60%) of our sources to possess an important bulge and/or central point source component, most of which reveal additional underlying structures after subtraction of a best-fit Sersic (or Sersic+PSF) profile. Based on visual inspection of the NIC2 images and their residuals, we estimate that ~80% of all our sources are mergers. We calculate lower and upper limits on the merger fraction to be 62% and 91%, respectively. At z<1.5, we observe objects in early (pre-coalescence) merging stages to be mostly disk and star formation dominated, while we find mergers to be mainly bulge dominated and active galactic nucleus (AGN)-starburst composites during coalescence and then AGN dominated in late stages. This is analogous to what is observed in local ULIRGs. Finally, we observe obscured ({tau}_9.7um_>3.36) quasars to live in faint and compact hosts and show that these are likely high-redshift analogs of local dense-core mergers. We find late-stage mergers to possess predominantly unobscured AGN spectra, but do not observe other morphological classes to carry any specific combination of {tau}_9.7um_ and polycyclic aromatic hydrocarbon (PAH) equivalent width.
1624. HST observations of carbon in spiral galaxies
ID:
ivo://CDS.VizieR/J/ApJ/513/168
Title:
HST observations of carbon in spiral galaxies
Short Name:
J/ApJ/513/168
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present measurements of the gas-phase abundance ratio C/O in six H II regions in the spiral galaxies M101 and NGC 2403, based on ultraviolet spectroscopy using the Faint Object Spectrograph on the Hubble Space Telescope. The ratios of C to O increase systematically with O/H in both galaxies, from log(C/O){~=}-0.8 at log(O/H){~=}-4.0 to log(C/O){~=}-0.1 at log(O/H){~=}-3.4. C/N shows no correlation with O/H. The rate of increase of C/O is somewhat uncertain because of uncertainty as to the appropriate UV reddening law and uncertainty in the metallicity dependence on grain depletions. However, the trend of increasing C/O with O/H is clear, confirming and extending the trend in C/O indicated previously from observations of irregular galaxies. Our data indicate that the radial gradients in C/H across spiral galaxies are steeper than the gradients in O/H. Comparing the data to chemical-evolution models for spiral galaxies shows that models in which the massive star yields do not vary with metallicity predict radial C/O gradients that are much flatter than the observed gradients.
1625. HST observations of Extremely Red Objects
ID:
ivo://CDS.VizieR/J/MNRAS/330/1
Title:
HST observations of Extremely Red Objects
Short Name:
J/MNRAS/330/1
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a survey for extremely red objects (EROs) undertaken in the fields of 10 massive galaxy cluster lenses at z~0.2, combining sensitive, high-resolution Hubble Space Telescope imaging with deep, half-arcsecond K-band imaging from UKIRT. We detect 60 EROs with (R-K)>=5.3, of which 26 have (R-K)>=6.0 in a total image-plane survey area of 49arcmin2 down to K=20.6, including one multiply imaged ERO.
1626. HST observations of GCs in NGC 1399
ID:
ivo://CDS.VizieR/J/ApJ/746/88
Title:
HST observations of GCs in NGC 1399
Short Name:
J/ApJ/746/88
Date:
21 Oct 2021
Publisher:
CDS
Description:
We combine new Wide Field Camera 3 IR Channel (WFC3/IR) F160W (H_160_) imaging data for NGC 1399, the central galaxy in the Fornax cluster, with archival F475W (g_475_), F606W (V_606_), F814W (I_814_), and F850LP (z _850_) optical data from the Advanced Camera for Surveys (ACS). The purely optical g_475_-I_814_, V_606_-I_814_, and g_475_-z_850_colors of NGC 1399's rich globular cluster (GC) system exhibit clear bimodality, at least for magnitudes I_814_>21.5. The optical-IR I_814_-H_160_ color distribution appears unimodal, and this impression is confirmed by mixture modeling analysis. The V_606_-H_160_ colors show marginal evidence for bimodality, consistent with bimodality in V_606_-I_814_ and unimodality in I_814_-H_160_.
1627. HST Observations of 2 high-z clusters
ID:
ivo://CDS.VizieR/J/ApJ/644/30
Title:
HST Observations of 2 high-z clusters
Short Name:
J/ApJ/644/30
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the photometric and structural properties of spectroscopically confirmed members in the two massive X-ray-selected z~0.83 galaxy clusters MS 105403 and RX J0152.7-1357 using three-band mosaic imaging with the Hubble Space Telescope Advanced Camera for Surveys. The samples include 105 and 140 members of RX J0152.7-1357 and MS 105403, respectively, to i_775_<24.0. A quantitative classification scheme using Sersic indices and "bumpiness" (the ratio of the rms residuals to the model mean) was found to correlate well with visual morphological type. The color-magnitude residuals correlate well with the local density, as measured from both galaxy numbers and weak lensing. Weaker correlations are found with cluster radius (the fundamental dependence is on local density).
1628. HST observations of HII regions in M51
ID:
ivo://CDS.VizieR/J/ApJ/735/75
Title:
HST observations of HII regions in M51
Short Name:
J/ApJ/735/75
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of HII regions in M51 using the Hubble Space Telescope Advanced Camera for Surveys images taken as part of the Hubble Heritage Program. We have cataloged about 19600 HII regions in M51 with H{alpha} luminosity in the range of L=10^35.5^-10^39.0^erg/s. The H{alpha} luminosity function of HII regions (HII LF) in M51 is well represented by a double power law with its index {alpha}=-2.25+/-0.02 for the bright part and {alpha}=-1.42+/-0.01 for the faint part, separated at a break point L=10^37.1^erg/s. This break was not found in previous studies of M51 HII regions. Comparison with simulated HII LFs suggests that this break is caused by the transition of HII region ionizing sources, from low-mass clusters (with ~10^3^M_{sun}_, including several OB stars) to more massive clusters (including several tens of OB stars). The HII LFs with L<10^37.1^erg/s are found to have different slopes for different parts in M51: the HII LF for the interarm region is steeper than those for the arm and the nuclear regions. This observed difference in HII LFs can be explained by evolutionary effects: HII regions in the interarm region are relatively older than those in the other parts of M51.
1629. HST observations of star clusters in NGC 3256
ID:
ivo://CDS.VizieR/J/ApJ/826/32
Title:
HST observations of star clusters in NGC 3256
Short Name:
J/ApJ/826/32
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use the Advanced Camera for Surveys on the Hubble Space Telescope to study the rich population of young massive star clusters in the main body of NGC 3256, a merging pair of galaxies with a high star formation rate (SFR) and SFR per unit area ({Sigma}_SFR_). These clusters have luminosity and mass functions that follow power laws, dN/dL{propto}L^{alpha}^ with {alpha}=-2.23+/-0.07, and dN/dM{propto}M^{beta}^ with {beta}=-1.86+/-0.34 for {tau}<10Myr clusters, similar to those found in more quiescent galaxies. The age distribution can be described by dN/d{tau}{propto}{tau}^{gamma}^, with {gamma}~-0.67+/-0.08 for clusters younger than about a few hundred million years, with no obvious dependence on cluster mass. This is consistent with a picture where ~80% of the clusters are disrupted each decade in time. We investigate the claim that galaxies with high {Sigma}_SFR_ form clusters more efficiently than quiescent systems by determining the fraction of stars in bound clusters ({Gamma}) and the CMF/SFR statistic (CMF is the cluster mass function) for NGC 3256 and comparing the results with those for other galaxies. We find that the CMF/SFR statistic for NGC 3256 agrees well with that found for galaxies with {Sigma}_SFR_ and SFRs that are lower by 1-3 orders of magnitude, but that estimates for {Gamma} are only robust when the same sets of assumptions are applied. Currently, {Gamma} values available in the literature have used different sets of assumptions, making it more difficult to compare the results between galaxies.
1630. HST obs. of Mira variables in the SNIa host NGC1559
ID:
ivo://CDS.VizieR/J/ApJ/889/5
Title:
HST obs. of Mira variables in the SNIa host NGC1559
Short Name:
J/ApJ/889/5
Date:
17 Jan 2022 11:46:55
Publisher:
CDS
Description:
We present year-long, near-infrared Hubble Space Telescope (HST) WFC3 observations used to search for Mira variables in NGC 1559, the host galaxy of the Type Ia supernova (SN Ia) SN 2005df. This is the first dedicated search for Miras, highly evolved low-mass stars, in an SNIa host, and subsequently the first calibration of the SN Ia luminosity using Miras in a role historically played by Cepheids. We identify a sample of 115 O-rich Miras with P<400days based on their light-curve properties. We find that the scatter in the Mira period-luminosity relation (PLR) is comparable to Cepheid PLRs seen in SN Ia host galaxies. Using a sample of O-rich Miras discovered in NGC 4258 with HSTF160W and its maser distance, we measure a distance modulus for NGC1559 of {mu}_1559_=31.41+/-0.050(statistical)+/-0.060(systematic)mag. Based on the light curve of the normal, well-observed, low-reddening SN 2005df, we obtain a measurement of the fiducial SN Ia absolute magnitude of M_B_^0^=-19.27+/-0.13mag. With the Hubble diagram of SNe Ia we find H_0_=72.7+/-4.6km/s/Mpc. Combining the calibration from the NGC 4258 megamaser and the Large Magellanic Cloud detached eclipsing binaries gives a best value of H_0_=73.3+/-4.0km/s/Mpc. This result is within 1{sigma} of the Hubble constant derived using Cepheids and multiple calibrating SNe Ia. This is the first of four expected calibrations of the SN Ia luminosity from Miras that should reduce the error in H_0_ via Miras to ~3%. In light of the present Hubble tension and JWST, Miras have utility in the extragalactic distance scale to check Cepheid distances or calibrate nearby SNe in early-type host galaxies that would be unlikely targets for Cepheid searches.