NGC 4395
Sdm
M • = 10
4−10
5M
☉NGC 4395
Sdm
M • = 10
4−10
5M
☉POX 52
Sph or dE
Wednesday, February 26, 14
NGC 4395
Sdm
M • = 10
4−10
5M
☉POX 52
Sph or dE
M • = 1.6 x 10
5M
☉Wednesday, February 26, 14
BH Mass Function 9
Fig. 7.— Volume-weighted BH mass function in bins of 0.25 dex (# Mpc−3 log MBH−1). The weights used are identical to those for the luminosity function, and as above we show in the inset the mass functions for objects targeted as galaxies (left) and QSOs (right), respectively. Although we are subject to significant incom-pleteness, we will argue below that there is truly a turnover in active galaxy masses at both lower and higher BH masses. We have fit the mass function with both a double power-law (dashed line) and a log-normal function (solid line).
Additionally, as the BH mass increases, the corresponding bulge luminosity is presumably increasing, further decreas-ing the contrast and the S/N in the broad line.
If we could uniquely ascribe a host galaxy luminosity and light profile to each MBH, then we could easily model our incompleteness as a function of MBH and Lbol/LEdd. At high BH mass, this is in fact possible, as there is a re-lation linking MBH and spheroid luminosity, and the fun-damental plane tells us the typical sizes (and thus fiber luminosities) of elliptical galaxies. However, for spiral or dwarf spheroidal host galaxies, there ceases to be a unique mapping between MBH and galaxy luminosity or structure.
The relation between bulge-to-total ratio and galaxy lumi-nosity is poorly quantified and contains significant scatter in any case. Furthermore, at lower masses, as the AGNs become intrinsically fainter, only systems with relatively luminous host galaxies will fall above the magnitude limit of the SDSS. For these reasons, at low MBH the calculated incompleteness is a strong function of the assumed (but unconstrained) host galaxy morphology.
As a matter of practicality, then, we turn the problem around. Rather than attempting to quantify our absolute incompleteness as a function of MBH, we simply quan-tify the range of host galaxy luminosities for which we might hope to detect a BH of a given mass, LHα, and z. Over narrow ranges in all of these parameters, neither the line width nor the galaxy continuum strength changes dramatically and the completeness ought to be constant (provided the BHs are drawn from the same host galaxy population). In such bins, with uniform completeness, we are able to measure true changes in space density.
Sim-ulations allow us to isolate ranges of MBH, LHα, and z with constant sensitivity to galaxy fiber luminosity. Note, however, that in any given interval, we necessarily exclude different members of the population as a function of MBH; at the lowest masses we preferentially exclude those sys-tems in faint hosts, while at the highest MBH we exclude the higher Lbol/LEdd systems. Therefore, we implicitly as-sume that the distribution of MBH is uniform independent of both disk luminosity and Eddington luminosity. With this approach, however, we need not concern ourselves di-rectly with host galaxy structure3 per se, but solely the luminosity. The total host galaxy luminosity must be high enough that the source is spectroscopically targeted, while the fiber luminosity must be low enough to allow detection of the broad line.
We investigate three mass regimes (MBH=105.5 − 106.4, 106 − 107, and 106.5 − 107.5 M!), choosing optimal z and LHα ranges for each. Our procedure is described in most detail for the lowest (and most challenging) mass bin, and then results are presented for all three. In the first bin, we are fundamentally limited by the total number of ob-jects. Therefore, we are forced to use the lowest possible redshift bins: z = 0.05−0.07 and z = 0.07−0.1. These are bins with ≥ 10 objects per bin for the most part; at still lower z a prohibitively large range in distance is needed to populate each bin. In terms of LHα, the highest lu-minosity is set by the Eddington lulu-minosity of the lowest mass bin, in this case 1041 ergs s−1 for a BH with mass 105.5 M!, while the lowest luminosity is set by the paucity of lower-luminosity objects (1040.5 ergs s−1).
Simulations allow us to verify that the selection proba-bility is indeed independent of host galaxy fiber luminos-ity. We make artificial spectra in the appropriate MBH and LHα range, with fiber galaxy luminosities spanning
−14 ≤ MB ≤ −22. The galaxy continuum is modeled as a single stellar absorption-line system, constructed from the eigenspectra of Yip et al. (2004), and the S/N is varied to correspond to typical SDSS spectra over the redshift range of interest. Five realizations are made for each galaxy lu-minosity and S/N, and each spectrum is run through our full detection algorithm. For those with detectable broad Hα, we then investigate whether the galaxy luminosity is sufficient for spectroscopic targeting in the first place. Re-call that this limit depends on total (rather than fiber) luminosity, but there is not a one-to-one conversion from fiber to total luminosity; it depends on galaxy morphology and redshift rather strongly. Therefore, we place an upper limit on the total galaxy luminosity by insisting that the fiber luminosity account for no less than 20% of the to-tal galaxy luminosity (as motivated by the observed range shown in Fig. 9 of Tremonti et al. 2004). Over the entire range of galaxy luminosities we explore, a non-zero detec-tion fracdetec-tion results only for fiber luminosities in the range
−16 < MB < −18, but the detection fractions at a given host luminosity are very constant across the mass range of interest, as shown in Figure 8.
In Figure 9a we show the resulting mass functions for the two different redshift bins. Visually, it appears that the space density is truly falling at low mass. To quantify
Greene & Ho (2004, 2007); Dong, Ho et al. (2012)
Wednesday, February 26, 14
BH Mass Function 9
Fig. 7.— Volume-weighted BH mass function in bins of 0.25 dex (# Mpc−3 log MBH−1). The weights used are identical to those for the luminosity function, and as above we show in the inset the mass functions for objects targeted as galaxies (left) and QSOs (right), respectively. Although we are subject to significant incom-pleteness, we will argue below that there is truly a turnover in active galaxy masses at both lower and higher BH masses. We have fit the mass function with both a double power-law (dashed line) and a log-normal function (solid line).
Additionally, as the BH mass increases, the corresponding bulge luminosity is presumably increasing, further decreas-ing the contrast and the S/N in the broad line.
If we could uniquely ascribe a host galaxy luminosity and light profile to each MBH, then we could easily model our incompleteness as a function of MBH and Lbol/LEdd. At high BH mass, this is in fact possible, as there is a re-lation linking MBH and spheroid luminosity, and the fun-damental plane tells us the typical sizes (and thus fiber luminosities) of elliptical galaxies. However, for spiral or dwarf spheroidal host galaxies, there ceases to be a unique mapping between MBH and galaxy luminosity or structure.
The relation between bulge-to-total ratio and galaxy lumi-nosity is poorly quantified and contains significant scatter in any case. Furthermore, at lower masses, as the AGNs become intrinsically fainter, only systems with relatively luminous host galaxies will fall above the magnitude limit of the SDSS. For these reasons, at low MBH the calculated incompleteness is a strong function of the assumed (but unconstrained) host galaxy morphology.
As a matter of practicality, then, we turn the problem around. Rather than attempting to quantify our absolute incompleteness as a function of MBH, we simply quan-tify the range of host galaxy luminosities for which we might hope to detect a BH of a given mass, LHα, and z. Over narrow ranges in all of these parameters, neither the line width nor the galaxy continuum strength changes dramatically and the completeness ought to be constant (provided the BHs are drawn from the same host galaxy population). In such bins, with uniform completeness, we are able to measure true changes in space density.
Sim-ulations allow us to isolate ranges of MBH, LHα, and z with constant sensitivity to galaxy fiber luminosity. Note, however, that in any given interval, we necessarily exclude different members of the population as a function of MBH; at the lowest masses we preferentially exclude those sys-tems in faint hosts, while at the highest MBH we exclude the higher Lbol/LEdd systems. Therefore, we implicitly as-sume that the distribution of MBH is uniform independent of both disk luminosity and Eddington luminosity. With this approach, however, we need not concern ourselves di-rectly with host galaxy structure3 per se, but solely the luminosity. The total host galaxy luminosity must be high enough that the source is spectroscopically targeted, while the fiber luminosity must be low enough to allow detection of the broad line.
We investigate three mass regimes (MBH=105.5 − 106.4, 106 − 107, and 106.5 − 107.5 M!), choosing optimal z and LHα ranges for each. Our procedure is described in most detail for the lowest (and most challenging) mass bin, and then results are presented for all three. In the first bin, we are fundamentally limited by the total number of ob-jects. Therefore, we are forced to use the lowest possible redshift bins: z = 0.05−0.07 and z = 0.07−0.1. These are bins with ≥ 10 objects per bin for the most part; at still lower z a prohibitively large range in distance is needed to populate each bin. In terms of LHα, the highest lu-minosity is set by the Eddington lulu-minosity of the lowest mass bin, in this case 1041 ergs s−1 for a BH with mass 105.5 M!, while the lowest luminosity is set by the paucity of lower-luminosity objects (1040.5 ergs s−1).
Simulations allow us to verify that the selection proba-bility is indeed independent of host galaxy fiber luminos-ity. We make artificial spectra in the appropriate MBH and LHα range, with fiber galaxy luminosities spanning
−14 ≤ MB ≤ −22. The galaxy continuum is modeled as a single stellar absorption-line system, constructed from the eigenspectra of Yip et al. (2004), and the S/N is varied to correspond to typical SDSS spectra over the redshift range of interest. Five realizations are made for each galaxy lu-minosity and S/N, and each spectrum is run through our full detection algorithm. For those with detectable broad Hα, we then investigate whether the galaxy luminosity is sufficient for spectroscopic targeting in the first place. Re-call that this limit depends on total (rather than fiber) luminosity, but there is not a one-to-one conversion from fiber to total luminosity; it depends on galaxy morphology and redshift rather strongly. Therefore, we place an upper limit on the total galaxy luminosity by insisting that the fiber luminosity account for no less than 20% of the to-tal galaxy luminosity (as motivated by the observed range shown in Fig. 9 of Tremonti et al. 2004). Over the entire range of galaxy luminosities we explore, a non-zero detec-tion fracdetec-tion results only for fiber luminosities in the range
−16 < MB < −18, but the detection fractions at a given host luminosity are very constant across the mass range of interest, as shown in Figure 8.
In Figure 9a we show the resulting mass functions for the two different redshift bins. Visually, it appears that the space density is truly falling at low mass. To quantify
3At a given luminosity, a wide range of galaxy morphologies are permitted. Thus it is still possible to find significant differences in σ∗ (e.g., Greene & Ho 2006b) and potentially host galaxy structure (J. E. Greene, in preparation) as a function of MBH for the SDSS-selected samples of low-mass systems.
200-300 new sources
Greene & Ho (2004, 2007); Dong, Ho et al. (2012)
Wednesday, February 26, 14
HST/ACS Greene, Ho & Barth (2008); Jiang et al. (2011a, 2011b)
Wednesday, February 26, 14
Wednesday, February 26, 14
Ho (2014a, b)
Wednesday, February 26, 14
Recent Updates
☯ Central BHs detected from 104 – 1010 M⊙
☯ All bulges contain BHs, but not all BHs live in bulges
☯ M• ~ Mbulge 〈M• / Mbulge〉 ~ 0.5%
☯ M• ∝ "4.4
☯ M•− " and M• − Mbulge relations have similar scatter
☯ Scaling relations only tight for classical bulges and Es
☯ Scaling relations already in place for high-z QSOs
☯ Mild evolution only for most massive BHs
☯ AGN feedback effective only for classical bulges and Es
1.2